102 results on '"Harry Hothi"'
Search Results
2. Characterisation of 3D-printed acetabular hip implants
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Arya Nicum, Harry Hothi, Johann Henckel, Anna di Laura, Klaus Schlueter-Brust, and Alister Hart
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3d-printed implants ,3d-printing ,acetabular cup ,additive manufacturing ,features ,hip ,orthopaedic implants ,Orthopedic surgery ,RD701-811 - Abstract
Three-dimensional printing is a rapidly growing manufacturing method for orthopaedic implants and it is currently thriving in several other engineering industries. It enables the variation of implant design and the construction of complex structures which can be exploited in orthopaedics and other medical sectors. In this review, we develop the vocabulary to characterise 3D printing in orthopaedics from terms defined by industries employing 3D printing, and by fully examining a 3D-printed off-the-shelf acetabular cup (Fig. 1). This is a commonly used 3D-printed implant in orthopaedics, and it exhibits a range of prominent features brought about by 3D printing. The key features and defects of the porous and dense regions of the implant are clarified and discussed in depth to determine reliable definitions and a common understanding of characteristics of 3D printing between engineers and medical experts in orthopaedics. Despite the extensive list of terminology derived here, it is clear significant gaps exist in the knowledge of this field. Therefore, it is necessary for continued investigations of unused implants, but perhaps more significantly, examining those in vivo and retrieved to understand their long-term impact on patients and the effects of certain features (e.g. surface-adhered particles). Analyses of this kind will establish an understanding of 3D printing in orthopaedics and additionally it will help to update the regulatory approach to this new technology. more...
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- 2024
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3. Cemented or uncemented fixation: Which allows a more acceptable prosthetic femoral version in total hip arthroplasty?
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Maria Moralidou, Anna Di Laura, Harry Hothi, Johann Henckel, and Alister J. Hart
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Primary total hip arthroplasty ,Prosthetic femoral version ,Uncemented hip surgery ,Cemented hip surgery ,Orthopedic surgery ,RD701-811 ,Diseases of the musculoskeletal system ,RC925-935 - Abstract
Abstract Background Three-dimensional computed-tomography (3D-CT) planning for primary Total Hip Arthroplasty (THA) typically uses the external femoral surface; as a result, it is difficult to predict the prosthetic femoral version (PFV) for uncemented femoral stems that press-fit to the internal surface of the bone. Cemented fixation allows the surgeon to adjust the version independent of the internal femoral anatomy. We aimed to better understand the effect of the fixation type on PFV. Methods This was a case series study including a total of 95 consecutive patients (106 hips), who underwent uncemented (n = 81 hips) and cemented (n = 25 hips) primary THA using the posterior approach. The surgeon aimed for a PFV of 20°. Our primary objective was to compare PFV in both groups; our secondary objective was to evaluate the clinical outcomes. Results The mean (± SD) PFV was 13° (± 9°) and 23° (± 8°) for the uncemented and cemented THA groups (P more...
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- 2023
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4. A Geometric Analysis of Polyethylene Liners Exposed to Acrylic-based Bone Cement
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Zoe Thompson, Harry Hothi, MSc, PhD, Jacqueline Brillantes, MSc, Amir Khoshbin, MD, MSc, and Amit Atrey, MD, MSc
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Hip arthroplasty ,Geometric analysis ,Polyethylene ,Acetabular component ,Acrylic-based bone cement ,Orthopedic surgery ,RD701-811 - Abstract
Background: Acrylic-based bone cement (polymethyl methacrylate [PMMA]) is a material commonly used in orthopaedic surgeries; however, during PMMA polymerization, a highly exothermic reaction occurs. The heat released in polymerization can damage nearby materials including poorly heat-resistant cross-linked polyethylene (XLPE). Both PMMA and XLPE are used in total hip arthroplasty and could interact during femoral stem fixation. We sought to determine if the exothermic polymerization of PMMA could alter the surface characteristics of XLPE acetabular liners. Methods: Six XLPE liners were assigned to one of 4 experimental categories with varying volumes of PMMA applied in a manner that mimicked how the 2 materials would come into contact intraoperatively. Measurements were taken both pre- and post-intervention using a coordinate measuring machine for geometric and gravimetric analysis. Light microscopy was conducted postintervention to examine the surface for damage. Results: Coordinate measuring machine measurements showed minimal gross deformation in all 6 liners, but there were isolated surface deposits in 4 of 6 liners. The average maximal surface deviations, when compared to the control, for liners exposed to 1 cc of cement, 2 cc of cement, or 1 cc of cement with a femoral head implant attached were 26.6 μm, 77.2 μm, and 26.4 μm, respectively. All but one liner showed an increase in volume following intervention when compared to the control. Subtle scratches were identified using light microscopy on all 6 liners. Conclusions: XLPE shows areas of isolated surface deformation in a dose-dependent manner but with minimal gross deformation after interacting with highly exothermic PMMA. more...
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- 2023
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5. Morphometric analysis of patient-specific 3D-printed acetabular cups: a comparative study of commercially available implants from 6 manufacturers
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Harry Hothi, Johann Henckel, Sean Bergiers, Anna Di Laura, Klaus Schlueter-Brust, and Alister Hart
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3D printing ,Micro-CT ,Porosity ,Additive manufacturing ,Medical physics. Medical radiology. Nuclear medicine ,R895-920 - Abstract
Abstract Background 3D printed patient-specific titanium acetabular cups are used to treat patients with massive acetabular defects. These have highly porous surfaces, with the design intent of enhancing bony fixation. Our aim was to characterise these porous structures in commercially available designs. Methods We obtained 12 final-production, patient-specific 3D printed acetabular cups that had been produced by 6 manufacturers. High resolution micro-CT imaging was used to characterise morphometric features of their porous structures: (1) strut thickness, 2) the depth of the porous layer, (3) pore size and (4) the level of porosity. Additionally, we computed the surface area of each component to quantify how much titanium may be in contact with patient tissue. Statistical comparisons were made between the designs. Results We found a variability between designs in relation to the thickness of the struts (0.28 to 0.65 mm), how deep the porous layers are (0.57 to 11.51 mm), the pore size (0.74 to 1.87 mm) and the level of porosity (34 to 85%). One manufacturer printed structures with different porosities between the body and flange; another manufacturer had two differing porous regions within the body of the cups. The cups had a median (range) surface area of 756.5 mm2 (348 – 1724). Conclusions There is a wide variability between manufacturers in the porous titanium structures they 3D print. We do not currently know whether there is an optimal porosity and how this variability will impact clinically on the integrity of bony fixation; this will become clearer as post market surveillance data is generated. more...
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- 2022
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6. Blood titanium levels in patients with large and sliding titanium implants
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Martina Tognini, Harry Hothi, Stewart Tucker, Edel Broomfield, Masood Shafafy, Panos Gikas, Anna Di Laura, Johann Henckel, and Alister Hart
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Titanium ,Blood ,Implants ,Diseases of the musculoskeletal system ,RC925-935 - Abstract
Abstract Background Titanium, which is known to be a highly biologically inert element, is one of the most commonly used metals in orthopaedic implants. While cobalt and chromium blood metal ion testing is routinely used in the clinical monitoring of patients with metal-on-metal hip implants, much less is known about the levels of titanium in patients with other implant types. The aim of this study was to better understand the normal ranges of blood titanium levels in patients implanted with large and sliding titanium constructs by comparison with reference levels from conventional titanium hips. Methods This study examined data collected from 136 patients. Over a period of 24 months, whole blood samples were collected from 41 patients implanted with large titanium implants: long (range 15 to 30 cm) spine rods with a sliding mechanism (“spine rods”, n = 18), long bone tumour implants (“tumour implants”, n = 13) and 3D-printed customised massive acetabular defect implants (“massive acetabular implants”, n = 10). This data was compared with standard, uncemented primary titanium hip implants (“standard hips”, 15 cm long) (n = 95). Clinical, imaging and blood titanium levels data were collected for all patients and compared statistically between the different groups. Results The median (range) of blood titanium levels of the standard hip, spine rods, femoral tumour implants and massive acetabular implants were 1.2 ppb (0.6–4.9), 9.7 ppb (4.0–25.4), 2.6 ppb (0.4–104.4) and 5.7 ppb (1.6–31.5) respectively. Spine rods and massive acetabular implants had significantly greater blood titanium levels compared to the standard hips group (p more...
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- 2022
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7. The accuracy and precision of acetabular implant measurements from CT imaging
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Johann Henckel, Angelika Ramesh, Harry Hothi, Robin Richards, Anna Di Laura, and Alister Hart
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3D-CT ,inclination ,version ,acetabular component position ,coordinate measuring arm ,cup orientation ,Biotechnology ,TP248.13-248.65 - Abstract
The placement of acetabular implant components determines the short- and long-term outcomes of total hip replacement (THR) and a number of tools have been developed to assist the surgeon in achieving cup orientation to match the surgical plan. However, the accuracy and precision of 3D-CT for the measurement of acetabular component position and orientation is yet to be established. To investigate this, we compared measurements of cobalt chrome acetabular components implanted into 2 different bony pelvic models between a coordinate measuring Faro arm and 3 different low dose CT images, including 3D-CT, 2D anterior pelvic plane (APP) referenced CT and 2D scanner referenced (SR) CT. Intra-observer differences were assessed using the Intraclass correlation coefficient (ICC). The effect of imaging the pelvis positioned in 3 different orientations within the CT scanner was also assessed. The measured parameters were the angles of inclination and version. 3D-CT measurements were found to closely match the “true values” of the component position measurements, compared with the 2D-CT methods. ICC analysis also showed good agreement between the coordinate measuring arm (CMA) and 3D-CT but poor agreement between the 2D SR method, in the results from two observers. When using the coordinate system of the CT scanner, the measurements consistently produced the greatest error; this method yielded values up to 34° different from the reference digitising arm. However, the difference between the true inclination and version angles and those measured from 3D APP CT was below half a degree in all cases. We concluded that low radiation dose 3D-CT is a validated reference standard for the measurement of acetabular cup orientation. more...
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- 2023
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8. Comparative retrieval analysis of a novel anatomic tibial tray backside: alterations in tibial component design and surface coating can increase cement adhesions and surface roughness
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Dominic T. Mathis, Joshua Schmidli, Felix Amsler, Johann Henckel, Harry Hothi, Alister Hart, and Michael T. Hirschmann
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Total knee arthroplasty ,Tibial tray ,Retrieval analysis ,Implant-cement interface ,Surface roughness ,TKA revision reason ,Diseases of the musculoskeletal system ,RC925-935 - Abstract
Abstract Background With the Persona® knee system a novel anatomic total knee design was developed, which has no pre-coating, whereas the predecessor knee system is pre-coated with polymethylmethacrylate (PMMA). Joint registry data have shown no decrease in risk of aseptic revision of PMMA pre-coated tibial components compared with non-pre-coated implants. The aim of this retrieval study was to compare the amount of cement adhesions, geometry and surface features between the two knee designs and to correlate them with the underlying reason for revision surgery. Methods Retrieval analysis was performed of 15 NexGen® and 8 Persona® fixed-bearing knee implants from the same manufacturer retrieved from two knee revision centres. A photogrammetric method was used to grade the amount of cement attached to the tibial tray backside. The geometry and dimensions of the tibial trays, tray projections and peripheral lips were measured using digital callipers and compared between the two different designs. To measure the surface roughness on the backside of the tibial tray, a contact profilometer was used. To investigate differences between the two designs statistical analyses (t-test) were performed. Results All Persona® trays showed evidence of cement adhesion with a % area of 75.4%; half of the NexGen® trays had cement adhesions, with a mean value of 20%. There was a significant difference in the percentage of area covered by cement between the two designs (p more...
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- 2022
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9. SPECT/CT Assessment of In-Vivo Loading of the Knee Correlates with Polyethylene Deformation in Retrieved Total Knee Arthroplasty
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Harry Hothi, Arianna Cerquiglini, Lukas Büel, Johann Henckel, Lukas B. Moser, Michael T. Hirschmann, and Alister Hart
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SPECT/CT ,TKA ,retrieval analysis ,Computer applications to medicine. Medical informatics ,R858-859.7 - Abstract
Background: SPECT/CT distribution patterns in patients with total knee replacements have previously been correlated with factors such as time of implantation, implant type and alignment. It is unknown, however, if an increased and more extended bone tracer uptake (BTU) in SPECT/CT, representing loading of the joint, correlates with findings from retrieval studies. The aim of this study was to further understand this subject. Materials and Methods: 62 retrieved TKA were included. SPECT/CT was performed prior to revision. Quantitative and qualitative medio-lateral comparisons of BTU intensity and distribution in the tibia were performed. Retrieval analysis was performed with a micro-CT method to assess the thickness differences between medial and lateral sides of polyethylene inserts with symmetrical designs. Results: In the subgroup of TKA with asymmetrical SPECT/CT distribution, there was a significant correlation between retrieval and medical imaging data (p = 0.0355): patients showing a more extended BTU in the medial compartment also had a significantly thinner insert in the medial compartment, and vice versa in the lateral side. Conclusion: This is the first study comparing BTU distribution patterns and retrieval findings. Our results support the hypothesis that SPECT/CT is able to identify bone activity due to implant position and loading. more...
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- 2022
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10. Comparative retrieval analysis of antioxidant polyethylene: bonding of vitamin-E does not reduce in-vivo surface damage
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Dominic T. Mathis, Joshua Schmidli, Michael T. Hirschmann, Felix Amsler, Johann Henckel, Harry Hothi, and Alister Hart
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Total knee arthroplasty ,Polyethylene ,Retrieval analysis ,Polyethylene surface damage ,Surface roughness ,Diseases of the musculoskeletal system ,RC925-935 - Abstract
Abstract Background With the Persona® knee system a new polyethylene formulation incorporating vitamin-E which aims to reduce oxidation and maintain wear resistance was introduced. Although in-vitro studies have demonstrated positive effects of the vitamin-E antioxidants on UHMWPE, no retrieval study has looked at polyethylene damage of this system yet. It was the aim to investigate the in-vivo performance of this new design, by comparing it with its predecessor in retrieval analysis. Methods 15 NexGen® and 8 Persona® fixed-bearing implants from the same manufacturer (Zimmer Biomet) were retrieved from two knee revision centres. For retrieval analysis, a macroscopic analysis of polyethylene using a peer-reviewed damage grading method was used (Hood-score). The roughness of all articulating metal components was measured using a contact profilometer. The reason(s) for TKA revision were recorded. Statistical analyses (t-test) were performed to investigate differences between the two designs. Results The mean Hood score for Persona® inserts was 109.3 and for NexGen® 115.1 without significant differences between the two designs. Results from the profilometer revealed that Persona® and NexGen® femoral implants showed an identical mean surface roughness of 0.14 μm. The Persona® tibial tray showed a significantly smoother surface (0.06 μm) compared to the NexGen® (0.2 μm; p more...
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- 2021
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11. The in vivo location of edge-wear in hip arthroplasties: combining pre-revision 3D CT imaging with retrieval analysis
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Sean Bergiers, Harry Hothi, Johann Henckel, Anna Di Laura, Martín Belzunce, John Skinner, and Alister Hart
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wear ,retrieval analysis ,ct ,hip arthroplasties ,hip joints ,hip implants ,ct scans ,acetabular component positioning ,metal-on-metal hip arthroplasties ,acetabular cartilage ,acetabular components ,acetabular cups ,subluxation ,Diseases of the musculoskeletal system ,RC925-935 - Abstract
Aims: Acetabular edge-loading was a cause of increased wear rates in metal-on-metal hip arthroplasties, ultimately contributing to their failure. Although such wear patterns have been regularly reported in retrieval analyses, this study aimed to determine their in vivo location and investigate their relationship with acetabular component positioning. Methods: 3D CT imaging was combined with a recently validated method of mapping bearing surface wear in retrieved hip implants. The asymmetrical stabilizing fins of Birmingham hip replacements (BHRs) allowed the co-registration of their acetabular wear maps and their computational models, segmented from CT scans. The in vivo location of edge-wear was measured within a standardized coordinate system, defined using the anterior pelvic plane. Results: Edge-wear was found predominantly along the superior acetabular edge in all cases, while its median location was 8° (interquartile range (IQR) -59° to 25°) within the anterosuperior quadrant. The deepest point of these scars had a median location of 16° (IQR -58° to 26°), which was statistically comparable to their centres (p = 0.496). Edge-wear was in closer proximity to the superior apex of the cups with greater angles of acetabular inclination, while a greater degree of anteversion influenced a more anteriorly centred scar. Conclusion: The anterosuperior location of edge-wear was comparable to the degradation patterns observed in acetabular cartilage, supporting previous findings that hip joint forces are directed anteriorly during a greater portion of walking gait. The further application of this novel method could improve the current definition of optimal and safe acetabular component positioning. more...
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- 2021
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12. Analysis of retrieved STRYDE nails
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Harry Hothi, Sean Bergiers, Johann Henckel, Alexis D. Iliadis, William David Goodier, Jonathan Wright, John Skinner, Peter Calder, and Alister J. Hart
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limb lengthening ,stryde nail ,retrieval analysis ,precice lengthening nail ,plain radiographs ,osteolysis ,chromium ,energy dispersive x-ray spectroscopy ,radiographs ,femoral nails ,infection ,tibial bones ,blood metal ion ,tibial nails ,Orthopedic surgery ,RD701-811 - Abstract
Aims: The aim of this study was to present the first retrieval analysis findings of PRECICE STRYDE intermedullary nails removed from patients, providing useful information in the post-market surveillance of these recently introduced devices. Methods: We collected ten nails removed from six patients, together with patient clinical data and plain radiograph imaging. We performed macro- and microscopic analysis of all surfaces and graded the presence of corrosion using validated semiquantitative scoring methods. We determined the elemental composition of surface debris using energy dispersive x-ray spectroscopy (EDS) and used metrology analysis to characterize the surface adjacent to the extendable junctions. Results: All nails were removed at the end of treatment, having achieved their intended lengthening (20 mm to 65 mm) and after regenerate consolidation. All nails had evidence of corrosion localized to the screw holes and the extendable junctions; corrosion was graded as moderate at the junction of one nail and severe at the junctions of five nails. EDS analysis showed surface deposits to be chromium rich. Plain radiographs showed cortical thickening and osteolysis around the junction of six nails, corresponding to the same nails with moderate – severe junction corrosion. Conclusion: We found, in fully united bones, evidence of cortical thickening and osteolysis that appeared to be associated with corrosion at the extendable junction; when corrosion was present, cortical thickening was adjacent to this junction. Further work, with greater numbers of retrievals, is required to fully understand this association between corrosion and bony changes, and the influencing surgeon, implant, and patient factors involved. Cite this article: Bone Jt Open 2021;2(8):599–610. more...
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- 2021
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13. Osseointegration of retrieved 3D-printed, off-the-shelf acetabular implants
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Lorenzo Dall’Ava, Harry Hothi, Johann Henckel, Anna Di Laura, Roberto Tirabosco, Antti Eskelinen, John Skinner, and Alister Hart
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3d-printing ,additive manufacturing ,osseointegration ,hip arthroplasty ,retrieval analysis ,Diseases of the musculoskeletal system ,RC925-935 - Abstract
Aims: The main advantage of 3D-printed, off-the-shelf acetabular implants is the potential to promote enhanced bony fixation due to their controllable porous structure. In this study we investigated the extent of osseointegration in retrieved 3D-printed acetabular implants. Methods: We compared two groups, one made via 3D-printing (n = 7) and the other using conventional techniques (n = 7). We collected implant details, type of surgery and removal technique, patient demographics, and clinical history. Bone integration was assessed by macroscopic visual analysis, followed by sectioning to allow undecalcified histology on eight sections (~200 µm) for each implant. The outcome measures considered were area of bone attachment (%), extent of bone ingrowth (%), bone-implant contact (%), and depth of ingrowth (%), and these were quantified using a line-intercept method. Results: The two groups were matched for patient sex, age (61 and 63 years), time to revision (30 and 41 months), implant size (54 mm and 52 mm), and porosity (72% and 60%) (p > 0.152). There was no difference in visual bony attachment (p = 0.209). Histological analysis showed greater bone ingrowth in 3D-printed implants (p < 0.001), with mean bone attachment of 63% (SD 28%) and 37% (SD 20%), respectively. This was observed for all the outcome measures. Conclusion: This was the first study to investigate osseointegration in retrieved 3D-printed acetabular implants. Greater bone ingrowth was found in 3D-printed implants, suggesting that better osseointegration can be achieved. However, the influence of specific surgeon, implant, and patient factors needs to be considered. more...
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- 2021
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14. The impact and surgeon perceptions of the suspension of the CE certification of MAGEC devices on clinical practice
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Harry Hothi
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MCGR ,EOS ,CE Mark ,MAGEC Rods ,alternative treatment ,surgical treatment ,Orthopedic surgery ,RD701-811 - Abstract
Abstract MAGnetic Expansion Control (MAGEC) rods are used in the surgical treatment of children with early onset scoliosis. The magnetically controlled lengthening mechanism enables rod distractions without the need for repeated invasive surgery. The CE certification of these devices was suspended in March 2021 due, primarily, to performance evidence gaps in the documents provided by the manufacturer to regulators and notified bodies. MAGEC rods are therefore not permitted for use in countries requiring CE marking. This was a survey of 18 MAGEC rod surgeons in the UK about their perception of the impact of the CE suspension on the clinical management of their patients. Unsurprisingly, virtually all perceived a negative impact, reflecting the complexity of this patient group. Reassuringly, these surgeons are highly experienced in alternative treatment methods. Cite this article: Bone Jt Open 2022;3(2):155–157. more...
- Published
- 2022
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15. Can 3D surgical planning and patient specific instrumentation reduce hip implant inventory? A prospective study
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Anna Di Laura, Johann Henckel, Harry Hothi, and Alister Hart
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Total hip Arthroplasty ,Preoperative planning ,Three-dimensional computerised planning ,Implant cost ,Implant inventory ,Medical physics. Medical radiology. Nuclear medicine ,R895-920 - Abstract
Abstract Background Modern designs of joint replacements require a large inventory of components to be available during surgery. Pre-operative CT imaging aids 3D surgical planning and implant sizing, which should reduce the inventory size and enhance clinical outcome. We aimed to better understand the impact of the use of 3D surgical planning and Patient Specific Instrumentation (PSI) on hip implant inventory. Methods An initial feasibility study of 25 consecutive cases was undertaken to assess the discrepancy between the planned component sizes and those implanted to determine whether it was possible to reduce the inventory for future cases. Following this, we performed a pilot study to investigate the effect of an optimized inventory stock on the surgical outcome: we compared a group of 20 consecutive cases (experimental) with the 25 cases in the feasibility study (control). We assessed: (1) accuracy of the 3D planning system in predicting size (%); (2) inventory size changes (%); (3) intra and post-operative complications. Results The feasibility study showed variability within 1 size range, enabling us to safely optimize inventory stock for the pilot study. (1) 3D surgical planning correctly predicted sizes in 93% of the femoral and 89% of the acetabular cup components; (2) there was a 61% reduction in the implant inventory size; (3) we recorded good surgical outcomes with no difference between the 2 groups, and all patients had appropriately sized implants. Conclusions 3D planning is accurate in up to 95% of the cases. CT-based planning can reduce inventory size in the hospital setting potentially leading to a reduction in costs. more...
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- 2020
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16. The effect of metal artefact on the design of custom 3D printed acetabular implants
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Anna Di Laura, Johann Henckel, Robert Wescott, Harry Hothi, and Alister J. Hart
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Paprosky acetabular classification ,Revision hip surgery ,Metal artefact ,Computed tomography ,Custom 3D printed implants ,Medical physics. Medical radiology. Nuclear medicine ,R895-920 - Abstract
Abstract Background 3D Printed custom-made implants constitute a viable option in patients with acetabular Paprosky III defects. In these patients, needing complex hip revision surgery, the appreciation of the bony defect is crucial to assure stable fixation of the customised implant, often intended to replace a failed one. We aimed to understand the effect of metal artefact on the design of customised implants. Methods 26 patients with massive acetabular defects were referred, between May 2016 and September 2018, to our institution classified as “un-reconstructable” by other hospitals. They all received custom 3D-printed acetabular cups. A subset of them underwent two-stage revision surgery due to infection. We then extended the two-stage procedure to the cases where metal artefacts were significantly affecting the reading of the CT scans. CT scans of patients’ pelvises were taken pre and post-implant removal. We assessed for changes in bony shape and volume of the pelvis using 3D imaging software and quantified the effect on implant design with CAD software. Results Eight (out of 26) patients (31%) underwent two-stage revision surgery. The CT bony reconstructions between the two timepoints changed in all cases. The changes were mostly associated to the shape and distribution of the acetabular defects. Three of these cases (37.5%) showed a remarkable difference in the remaining bone that led to a change in implant design. So far, there has been no difference in the clinical outcome between the patients who underwent single (n = 18) and two-stage surgery (n = 8). Conclusions The shape of the acetabulum reconstructed from CT data is potentially altered by metal artefact and bone excised during removal of the failed component. For “end-of-road” acetabular reconstruction, we recommend surgeons consider the use of two-stage surgery to enable a reliable fitting of the complex shape of 3D-printed implants. more...
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- 2020
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17. Characterization of dimensional, morphological and morphometric features of retrieved 3D-printed acetabular cups for hip arthroplasty
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Lorenzo Dall’Ava, Harry Hothi, Johann Henckel, Anna Di Laura, Paul Shearing, and Alister Hart
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3D printing ,Additive manufacturing ,Orthopaedic implants ,Hip arthroplasty ,Porous acetabular cups ,Orthopedic surgery ,RD701-811 ,Diseases of the musculoskeletal system ,RC925-935 - Abstract
Abstract Background Three-dimensional (3D) printing of porous titanium implants is increasing in orthopaedics, promising enhanced bony fixation whilst maintaining design similarities with conventionally manufactured components. Our study is one of the first to non-destructively characterize 3D-printed implants, using conventionally manufactured components as a reference. Methods We analysed 16 acetabular cups retrieved from patients, divided into two groups: ‘3D-printed’ (n = 6) and ‘conventional’ (n = 10). Coordinate-measuring machine (CMM), electron microscopy (SEM) and microcomputed tomography (micro-CT) were used to investigate the roundness of the internal cup surface, the morphology of the backside surface and the morphometric features of the porous structures of the cups, respectively. The amount of bony attachment was also evaluated. Results CMM analysis showed a median roundness of 19.45 and 14.52 μm for 3D-printed and conventional cups, respectively (p = 0.1114). SEM images revealed partially molten particles on the struts of 3D-printed implants; these are a by-product of the manufacturing technique, unlike the beads shown by conventional cups. As expected, porosity, pore size, strut thickness and thickness of the porous structure were significantly higher for 3D-printed components (p = 0.0002), with median values of 72.3%, 915 μm, 498 μm and 1.287 mm (p = 0.0002). The median values of bony attachment were 84.9% and 69.3% for 3D-printed and conventional cups, respectively (p = 0.2635). Conclusion 3D-printed implants are designed to be significantly more porous than some conventional components, as shown in this study, whilst still exhibiting the same shape and size. We found differences in the surface morphologies of the groups, related to the different manufacturing methods; a key finding was the presence of partially molten particles on the 3D-printed cups. more...
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- 2020
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18. Statistical Shape Modelling the In Vivo Location of Acetabular Wear in Retrieved Hip Implants
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Sean Bergiers, Johann Henckel, Harry Hothi, Anna Di Laura, Chris Goddard, David Raymont, Furqan Ullah, Ross Cotton, Rebecca Bryan, and Alister Hart
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statistical shape modelling ,retrieval analysis ,hip replacement ,CT imaging ,Technology ,Biology (General) ,QH301-705.5 - Abstract
Edge-wear in acetabular cups is known to be correlated with greater volumes of material loss; the location of this wear pattern in vivo is less understood. Statistical shape modelling (SSM) may provide further insight into this. This study aimed to identify the most common locations of wear in vivo, by combining CT imaging, retrieval analysis and SMM. Shape variance was described in 20 retrieved metal-on-metal acetabular surfaces. These were revised after a mean of 90 months, from 13 female and seven male patients. They were positioned with a mean inclination and anteversion of 53° and 30°, respectively. Their orientation, in vivo, was established using their stabilising fins, visible in pre-revision CT imaging. The impact of wear volume, positioning, time, gender and size on the in vivo location of wear was investigated. These surfaces had a mean wear volume of 49.63 mm3. The mean acetabular surface displayed superior edge-wear centred 7° within the posterosuperior quadrant, while more of the volumetric wear occurred in the anterosuperior quadrant. Components with higher inclination had greater superior edge-wear scars, while a relationship was observed between greater anteversion angles and more posterosuperior edge-wear. This SSM method can further our understanding of hip implant function, informing future design and may help to refine the safe zone for implant positioning. more...
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- 2022
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19. Accuracy of a Three-Dimensional (3D)-Printed Patient-Specific (PS) Femoral Osteotomy Guide: A Computed Tomography (CT) Study
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Maria Moralidou, Anna Di Laura, Johann Henckel, Harry Hothi, and Alister James Hart
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3D-printed patient-specific guides ,total hip arthroplasty ,femoral neck osteotomy ,Technology ,Biology (General) ,QH301-705.5 - Abstract
Femoral neck osteotomy creates a critical anatomical landmark for surgeons performing primary Total Hip Arthroplasty (THA); it affects the final height and position of the femoral component. Patient Specific Instrumentation (PSI) has been developed to guide the osteotomy. We aimed to assess the accuracy of a patient-specific (PS) femoral osteotomy guide in primary THA using three-dimensional (3D) computed tomography (CT) analysis. We included pre- and post-operative CT data of 103 THAs. All patients underwent 3D planning to define the optimal femoral neck osteotomy level. Our primary objective was to quantify the discrepancy between the achieved and planned osteotomy level; our secondary objective was to evaluate the clinical outcome. The median (Interquartile Range—IQR) discrepancy between the achieved and planned osteotomy level was 0.3 mm (−1 mm to 2 mm). We found a strong positive correlation between the planned and achieved osteotomy level (R2 = 0.9, p < 0.001). A satisfactory clinical outcome was recorded. Our findings suggest that surgeons can use 3D-printed PS guides to achieve a femoral neck osteotomy with a high level of accuracy to the plan. more...
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- 2022
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20. Comparative analysis of current 3D printed acetabular titanium implants
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Lorenzo Dall’Ava, Harry Hothi, Johann Henckel, Anna Di Laura, Paul Shearing, and Alister Hart
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3D printing ,Additive manufacturing ,Orthopaedic implant ,Acetabular cup ,Hip Arthroplasty ,Medical physics. Medical radiology. Nuclear medicine ,R895-920 - Abstract
Abstract Background The design freedom allowed by three-dimensional (3D) printing enables the production of acetabular off-the-shelf cups with complex porous structures. The only studies on these designs are limited to clinical outcomes. Our aim was to analyse and compare the designs of different 3D printed cups from multiple manufacturers (Delta TT, Trident II Tritanium and Mpact 3D Metal). Methods We analysed the outer surface of the cups using scanning electron microscopy (SEM) and assessed clinically relevant morphometric features of the lattice structures using micro-computed tomography (micro-CT). Dimensions related to the cup wall (solid, lattice and overall thickness) were also measured. Roundness and roughness of the internal cup surface were analysed with coordinate measuring machine (CMM) and optical profilometry. Results SEM showed partially molten titanium beads on all cups, significantly smaller on Trident II (27 μm vs ~ 70 μm, p more...
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- 2019
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21. Host-specific factors affect the pathogenesis of adverse reaction to metal debris
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Lari Lehtovirta, Aleksi Reito, Olli Lainiala, Jyrki Parkkinen, Harry Hothi, Johann Henckel, Alister Hart, and Antti Eskelinen
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Metal-on-metal ,ASR ,ARMD ,ALVAL ,Pseudotumor ,Pseudotumour ,Diseases of the musculoskeletal system ,RC925-935 - Abstract
Abstract Background Adverse Reaction to Metal Debris (ARMD) is a major reason for revision surgeries in patients with metal-on-metal (MoM) hip replacements. Most failures are related to excessively wearing implant producing harmful metal debris (extrinsic factor). As ARMD may also occur in patients with low-wearing implants, it has been suggested that there are differences in host-specific intrinsic factors contributing to the development of ARMD. However, there are no studies that have directly assessed whether the development of ARMD is actually affected by these intrinsic factors. Methods We included all 29 patients (out of 33 patients) with sufficient data who had undergone bilateral revision of ASR MoM hips (58 hips) at our institution. Samples of the inflamed synovia and/or pseudotumour were obtained perioperatively and sent to histopathological analysis. Total wear volumes of the implants were assessed. Patients underwent MARS-MRI imaging of the hips preoperatively. Histological findings, imaging findings and total wear volumes between the hips of each patient were compared. Results The difference in wear volume between the hips was clinically and statistically significant (median difference 15.35 mm3, range 1 to 39 mm3, IQR 6 to 23 mm3) (p 0.05 for all comparisons). These features included macrophage sheet thickness, perivascular lymphocyte cuff thickness, presence of plasma cells, presence of diffuse lymphocytic infiltration and presence of germinal centers. Conclusions Despite the significantly differing amounts of wear (extrinsic factor) seen between the sides, majority of the histological findings were similar in both hips and the presence of pseudotumour was symmetrical in most hips. As a direct consequence, it follows that there must be intrinsic factors which contribute to the symmetry of the findings, ie. the pathogenesis of ARMD, on individual level. This has been hypothesized in the literature but no studies have been conducted to confirm the hypothesis. Further, as the threshold of metal debris needed to develop ARMD appears to be largely variable based on the previous literature, it is likely that there are between-patient differences in these intrinsic factors, ie. the host response to metal debris is individual. more...
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- 2019
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22. Analysis of bearing wear, whole blood and synovial fluid metal ion concentrations and histopathological findings in patients with failed ASR hip resurfacings
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Lari Lehtovirta, Aleksi Reito, Jyrki Parkkinen, Harry Hothi, Johann Henckel, Alister Hart, and Antti Eskelinen
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Metal-on-metal hip replacement ,Adverse reaction to metal debris ,ARMD ,ALTR ,ALVAL ,Wear ,Diseases of the musculoskeletal system ,RC925-935 - Abstract
Abstract Background Adverse Reaction to Metal Debris (ARMD) is still a major reason for revision surgeries in patients with metal-on-metal (MoM) hip replacements. ARMD consists of a wide range of alterations in periprosthetic tissues, most important of which are metallosis, inflammation, pseudotumors and necrosis. Studies investigating histopathological findings and their association to implant wear or indirect measures of wear have yielded inconsistent results. Therefore, we aimed to investigate bearing surface wear volume, whole blood and synovial fluid metal ion concentrations, histopathological findings in periprosthetic tissues and their associations. Methods Seventy-eight patients with 85 hips revised for ARMD were included in the study. Prior to revision surgery, all patients had whole blood chromium and cobalt ion levels assessed. In revision surgery, a synovial fluid sample was taken and analyzed for chromium and cobalt. Periprosthetic tissue samples were taken and analyzed for histopathological findings. Explanted implants were analyzed for bearing wear volume of both acetabular cup and femoral head components. Results Volumetric wear of the failed components was highly variable. The total wear volume of the head and cup had a strong correlation with whole blood chromium and cobalt ion concentrations (Cr: ρ = 0.80, p more...
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- 2017
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23. Quantifying the bearing surface wear of retrieved hip replacements
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Sean Bergiers, Harry Hothi, Robin Richards, Johann Henckel, and Alister Hart
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volume measurement ,prosthetics ,wear ,machine bearings ,geometry ,biomedical materials ,biomechanics ,bearing surface wear ,retrieved hip replacements ,accurate quantification ,material loss ,metal-on-metal hip replacements ,geometric methods ,volumetric wear ,retrieved implants ,numerous contrasting approaches ,data collection strategies ,error incurring factors ,current methods ,pre-wear geometry ,wear volume measurements ,automated analysis strategy ,entire bearing surface ,implants pristine geometry ,geometrically effected data points ,fit ,size ,reference geometry ,volume change representative ,MOM hip implants ,clinically meaningful data ,Biotechnology ,TP248.13-248.65 ,Biochemistry ,QD415-436 - Abstract
Accurate quantification of bearing material loss from retrieved metal-on-metal (MOM) hip replacements is key to understanding their failure. Geometric methods are currently the only means of estimating volumetric wear from retrieved implants and numerous contrasting approaches to obtain these measures have been published. Data collection strategies have been thoroughly discussed and refined to minimise the effect of error incurring factors; however, there is an opportunity to optimise the current methods of estimating the pre-wear geometry and, therefore, improve the accuracy of wear volume measurements. An automated analysis strategy to quantify volumetric wear is proposed in this study, which utilises the entire bearing surface to determine the implants pristine geometry. This involves the iterative removal of geometrically effected data points to optimise the fit and size of a perfect sphere. Once fitted, this reference geometry is compared with the measured data, in its entirety, to calculate the volume change representative of the quantity of material lost. Improving the reliability of this parameter could influence the care of a million patients that remain with MOM hip implants. Rigorous validation of this method will dominate future work, ensuring that the accuracy and reliability of this approach are sufficient to provide clinically meaningful data. more...
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- 2019
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24. 3D Printed Acetabular Cups for Total Hip Arthroplasty: A Review Article
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Lorenzo Dall’Ava, Harry Hothi, Anna Di Laura, Johann Henckel, and Alister Hart
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3D printing ,additive manufacturing ,orthopaedic implants ,total hip arthroplasty ,acetabular cups ,Mining engineering. Metallurgy ,TN1-997 - Abstract
Three-dimensional (3D) printed titanium orthopaedic implants have recently revolutionized the treatment of massive bone defects in the pelvis, and we are on the verge of a change from conventional to 3D printed manufacture for the mass production of millions of off-the-shelf (non-personalized) implants. The process of 3D printing has many adjustable variables, which taken together with the possible variation in designs that can be printed, has created even more possible variables in the final product that must be understood if we are to predict the performance and safety of 3D printed implants. We critically reviewed the clinical use of 3D printing in orthopaedics, focusing on cementless acetabular components used in total hip arthroplasty. We defined the clinical and engineering rationale of 3D printed acetabular cups, summarized the key variables involved in the manufacturing process that influence the properties of the final parts, together with the main limitations of this technology, and created a classification according to end-use application to help explain the controversial and topical issues. Whilst early clinical outcomes related to 3D printed cups have been promising, in-depth robust investigations are needed, partly because regulatory approval systems have not fully adapted to the change in technology. Analysis of both pristine and retrieved cups, together with long-term clinical outcomes, will help the transition to 3D printing to be managed safely. more...
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- 2019
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25. Rod Fracture in Magnetically Controlled Growing Spine Rods
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Martina Tognini, Harry Hothi, Sean Bergiers, Edel Broomfield, Stewart Tucker, Johann Henckel, and Alister Hart
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Pediatrics, Perinatology and Child Health ,Orthopedics and Sports Medicine ,General Medicine - Published
- 2023
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26. Statistical shape modeling of the large acetabular defect in hip revision surgery
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Sara De Angelis, Johann Henckel, Sean Bergiers, Harry Hothi, Anna Di Laura, and Alister Hart
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Orthopedics and Sports Medicine - Published
- 2023
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27. Clinical guidelines on the use of biomarkers for surveillance of hip replacements
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Harry Hothi, Reshid Berber, Shiraz A. Sabah, and Alister J. Hart
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- 2023
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28. List of contributors
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Obakanyin J. Akinfosile, Ravindra V. Badhe, Mark Barba, Andrew R. Beadling, Reshid Berber, Divya Bijukumar, Benjamin Bloch, Michael G. Bryant, Alister J. Hart, Laura-Maria Horga, Harry Hothi, Peter James, Marc-Olivier Kiss, Andrew Manktelow, Vincent Massé, Mathew T. Mathew, Anne Neville, Shiraz A. Sabah, Angela Styhler, Pascal-André Vendittoli, and Ilona Świtkowska more...
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- 2023
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29. The in vivo location of edge-wear in hip arthroplasties
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John A. Skinner, Alister Hart, Sean Bergiers, Martin A. Belzunce, Harry Hothi, Anna Di Laura, and Johann Henckel
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musculoskeletal diseases ,wear ,metal-on-metal hip arthroplasties ,ct scans ,Diseases of the musculoskeletal system ,Edge (geometry) ,Acetabular cartilage ,In vivo ,Medicine ,Orthopedics and Sports Medicine ,hip implants ,subluxation ,Subluxation ,retrieval analysis ,hip arthroplasties ,business.industry ,medicine.disease ,acetabular cartilage ,acetabular component positioning ,acetabular components ,RC925-935 ,acetabular cups ,Surgery ,Ct imaging ,business ,Nuclear medicine ,hip joints ,ct - Abstract
Aims Acetabular edge-loading was a cause of increased wear rates in metal-on-metal hip arthroplasties, ultimately contributing to their failure. Although such wear patterns have been regularly reported in retrieval analyses, this study aimed to determine their in vivo location and investigate their relationship with acetabular component positioning. Methods 3D CT imaging was combined with a recently validated method of mapping bearing surface wear in retrieved hip implants. The asymmetrical stabilizing fins of Birmingham hip replacements (BHRs) allowed the co-registration of their acetabular wear maps and their computational models, segmented from CT scans. The in vivo location of edge-wear was measured within a standardized coordinate system, defined using the anterior pelvic plane. Results Edge-wear was found predominantly along the superior acetabular edge in all cases, while its median location was 8° (interquartile range (IQR) -59° to 25°) within the anterosuperior quadrant. The deepest point of these scars had a median location of 16° (IQR -58° to 26°), which was statistically comparable to their centres (p = 0.496). Edge-wear was in closer proximity to the superior apex of the cups with greater angles of acetabular inclination, while a greater degree of anteversion influenced a more anteriorly centred scar. Conclusion The anterosuperior location of edge-wear was comparable to the degradation patterns observed in acetabular cartilage, supporting previous findings that hip joint forces are directed anteriorly during a greater portion of walking gait. The further application of this novel method could improve the current definition of optimal and safe acetabular component positioning. Cite this article: Bone Joint Res 2021;10(10):639–649. more...
- Published
- 2021
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30. The analysis of defects in custom 3D-printed acetabular cups: A comparative study of commercially available implants from six manufacturers
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Harry Hothi, Johann Henckel, Sean Bergiers, Anna Di Laura, Klaus Schlueter‐Brust, and Alister Hart
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Orthopedics and Sports Medicine - Abstract
Three-dimensional (3D) printing is used to manufacture custom acetabular cups to treat patients with massive acetabular defects. There is a risk of defects occurring in these, often in the form of structural voids. Our aim was to investigate the presence of voids in commercially available cups. We examined 12, final-production titanium custom acetabular cups, that had been 3D-printed by six manufacturers. We measured their mass, then performed micro-computed tomography (micro-CT) imaging to determine their volume and density. The micro-CT data were examined for the presence of voids. In cups that had voids, we computed (1) the number of voids, (2) their volume and the cup volume fraction, (3) their sphericity, (4) size, and (5) their location. The cups had median mass, volume, and density of 208.5 g, 46,471 mm more...
- Published
- 2022
31. Analysis of retrieved STRYDE nails
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W D Goodier, John A. Skinner, Alister Hart, Alexis D. Iliadis, Sean Bergiers, Peter Calder, Harry Hothi, Jonathan Wright, and Johann Henckel
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General Orthopaedics ,Materials science ,Complications ,limb lengthening ,Radiography ,Glycemic Control ,tibial bones ,blood metal ion ,plain radiographs ,Orthopedic surgery ,retrieval analysis ,business.industry ,stryde nail ,General Engineering ,Glycated Haemoglobin ,precice lengthening nail ,infection ,Glucose ,energy dispersive x-ray spectroscopy ,radiographs ,femoral nails ,Plain radiographs ,chromium ,tibial nails ,Nuclear medicine ,business ,osteolysis ,Glucose Variability ,RD701-811 - Abstract
Aims The aim of this study was to present the first retrieval analysis findings of PRECICE STRYDE intermedullary nails removed from patients, providing useful information in the post-market surveillance of these recently introduced devices. Methods We collected ten nails removed from six patients, together with patient clinical data and plain radiograph imaging. We performed macro- and microscopic analysis of all surfaces and graded the presence of corrosion using validated semiquantitative scoring methods. We determined the elemental composition of surface debris using energy dispersive x-ray spectroscopy (EDS) and used metrology analysis to characterize the surface adjacent to the extendable junctions. Results All nails were removed at the end of treatment, having achieved their intended lengthening (20 mm to 65 mm) and after regenerate consolidation. All nails had evidence of corrosion localized to the screw holes and the extendable junctions; corrosion was graded as moderate at the junction of one nail and severe at the junctions of five nails. EDS analysis showed surface deposits to be chromium rich. Plain radiographs showed cortical thickening and osteolysis around the junction of six nails, corresponding to the same nails with moderate – severe junction corrosion. Conclusion We found, in fully united bones, evidence of cortical thickening and osteolysis that appeared to be associated with corrosion at the extendable junction; when corrosion was present, cortical thickening was adjacent to this junction. Further work, with greater numbers of retrievals, is required to fully understand this association between corrosion and bony changes, and the influencing surgeon, implant, and patient factors involved. Cite this article: Bone Jt Open 2021;2(8):599–610. more...
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- 2021
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32. Osseointegration of retrieved 3D-printed, off-the-shelf acetabular implants
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Antti Eskelinen, Alister Hart, Roberto Tirabosco, John A. Skinner, Anna Di Laura, Johann Henckel, Harry Hothi, Lorenzo Dall’Ava, Tampere University, Clinical Medicine, and Coxa PLC
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3d printed ,Materials science ,02 engineering and technology ,Diseases of the musculoskeletal system ,Osseointegration ,Arthroplasty ,3d-printing ,03 medical and health sciences ,Fixation (surgical) ,0302 clinical medicine ,Off the shelf ,Orthopedics and Sports Medicine ,hip arthroplasty ,030222 orthopedics ,retrieval analysis ,Hip ,osseointegration ,Reverse Hybrid ,3126 Surgery, anesthesiology, intensive care, radiology ,021001 nanoscience & nanotechnology ,Hip arthroplasty ,RC925-935 ,Surgery ,0210 nano-technology ,additive manufacturing ,Biomedical engineering - Abstract
Aims The main advantage of 3D-printed, off-the-shelf acetabular implants is the potential to promote enhanced bony fixation due to their controllable porous structure. In this study we investigated the extent of osseointegration in retrieved 3D-printed acetabular implants. Methods We compared two groups, one made via 3D-printing (n = 7) and the other using conventional techniques (n = 7). We collected implant details, type of surgery and removal technique, patient demographics, and clinical history. Bone integration was assessed by macroscopic visual analysis, followed by sectioning to allow undecalcified histology on eight sections (~200 µm) for each implant. The outcome measures considered were area of bone attachment (%), extent of bone ingrowth (%), bone-implant contact (%), and depth of ingrowth (%), and these were quantified using a line-intercept method. Results The two groups were matched for patient sex, age (61 and 63 years), time to revision (30 and 41 months), implant size (54 mm and 52 mm), and porosity (72% and 60%) (p > 0.152). There was no difference in visual bony attachment (p = 0.209). Histological analysis showed greater bone ingrowth in 3D-printed implants (p < 0.001), with mean bone attachment of 63% (SD 28%) and 37% (SD 20%), respectively. This was observed for all the outcome measures. Conclusion This was the first study to investigate osseointegration in retrieved 3D-printed acetabular implants. Greater bone ingrowth was found in 3D-printed implants, suggesting that better osseointegration can be achieved. However, the influence of specific surgeon, implant, and patient factors needs to be considered. Cite this article: Bone Joint Res 2021;10(7):388–400. more...
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- 2021
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33. The impact and surgeon perceptions of the suspension of the CE certification of MAGEC devices on clinical practice
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Vinay Jasani and Harry Hothi
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Orthopedic surgery ,EOS ,surgical treatment ,MAGEC Rods ,alternative treatment ,General Engineering ,CE Mark ,MCGR ,RD701-811 - Abstract
MAGnetic Expansion Control (MAGEC) rods are used in the surgical treatment of children with early onset scoliosis. The magnetically controlled lengthening mechanism enables rod distractions without the need for repeated invasive surgery. The CE certification of these devices was suspended in March 2021 due, primarily, to performance evidence gaps in the documents provided by the manufacturer to regulators and notified bodies. MAGEC rods are therefore not permitted for use in countries requiring CE marking. This was a survey of 18 MAGEC rod surgeons in the UK about their perception of the impact of the CE suspension on the clinical management of their patients. Unsurprisingly, virtually all perceived a negative impact, reflecting the complexity of this patient group. Reassuringly, these surgeons are highly experienced in alternative treatment methods. Cite this article: Bone Jt Open 2022;3(2):155–157. more...
- Published
- 2022
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34. Understanding the implant performance of magnetically controlled growing spine rods: a review article
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Colin Nnadi, Martina Tognini, Johann Henckel, Stewart Tucker, Masood Shafafy, Elisabetta Dal Gal, Alister Hart, and Harry Hothi
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Reoperation ,medicine.medical_specialty ,business.industry ,Gold standard ,Prostheses and Implants ,Scoliosis ,medicine.disease ,Spine ,Review article ,Systematic review ,Distraction ,medicine ,Humans ,Orthopedic Procedures ,Orthopedics and Sports Medicine ,Surgery ,Implant ,Neurosurgery ,Intensive care medicine ,Early failure ,business ,Aged - Abstract
Purpose Early-Onset Scoliosis (EOS) (defined as a curvature of the spine ≥ 10° with onset before 10 years of age) if not properly treated, can lead to increased morbidity and mortality. Traditionally Growing Rods (TGRs), implants fixated to the spine and extended every 6–8 months by surgery, are considered the gold standard, but Magnetically Controlled Growing Rods (MCGRs) avoid multiple surgeries. While the potential benefit of outpatient distraction procedure with MCGR is huge, concerns still remain about its risks, up to the release of a Medical Device Alert (MDA) by the Medicines and Healthcare Regulatory Agency (MHRA) advising not to implant MCGRs until further notice. The aim of this literature review is to (1) give an overview on the use of MCGRs and (2) identify what is currently understood about the surgical, implant and patient factors associated with the use of MCGRs. Methods Systematic literature review. Results Surgical factors such as use of single rod configuration or incorrect rod contouring might affect early failure of MCGRs. Patient’s older age and higher BMI are correlated with rod slippage. Wear debris and distraction mechanism failure may result from implant design and iteration. Conclusion Despite the complications reported, this technology still offers one of the best solutions to spine surgeons dealing with severe EOS. Lowering the complication rate by identifying risk factors for failure is possible and further studies in this direction are required. Once the risk factors are well described, some of these can be addressed enabling a safer use of MCGRs. more...
- Published
- 2021
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35. Metal-on-metal total hip arthroplasty: does increasing modularity affect clinical outcome?
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Harry Hothi, Kevin C Ilo, Alister Hart, and John A. Skinner
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Arthroplasty, Replacement, Hip ,Dentistry ,02 engineering and technology ,Prosthesis Design ,Affect (psychology) ,03 medical and health sciences ,0302 clinical medicine ,Humans ,Medicine ,Orthopedics and Sports Medicine ,Retrospective Studies ,030222 orthopedics ,Modularity (networks) ,business.industry ,Metal debris ,Modular design ,021001 nanoscience & nanotechnology ,Prosthesis Failure ,Corrosion ,Hip arthroplasty ,Metals ,Metal-on-Metal Joint Prostheses ,Surgery ,Hip Prosthesis ,0210 nano-technology ,business ,Total hip arthroplasty - Abstract
Background: Modularity of metal-on-metal (MoM) implants has come under scrutiny due to concerns regarding additional sources of metal debris. This study is a retrieval analysis of implants from the same manufacturer with the same MoM bearing surface. The difference between the implants was presence or absence of modular junctions. Methods: This is a retrospective study of 31 retrieved implants from 31 patients who received a Conserve Wright Medical MoM hip prosthesis. The 31 implants consisted of 16 resurfacings and 15 implants with modular junctions; 4 conventional THAs and 11 modular-neck THAs. Results: 43% of pre-revision MRI scans performed on resurfacing implants and 91% performed on the modular implants illustrated evidence of an adverse local tissue reaction. There was no difference in pre-revision blood metal ion levels or bearing surface wear between the resurfacings and modular implants. The neck-head tapers of the modular group showed low levels of material loss. However, the neck-stem tapers showed increased severity of corrosion and material loss Conclusions: The modular implants had an increased incidence of adverse local tissue reaction. This could be related to the presence of modular junctions, particular the neck-stem junction which showed increased susceptibly to corrosion more...
- Published
- 2020
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36. Three-dimensional pre-operative planning of primary hip arthroplasty: a systematic literature review
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Maria Moralidou, Harry Hothi, Anna Di Laura, Johann Henckel, and Alister Hart
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030222 orthopedics ,medicine.medical_specialty ,Hip ,Computer science ,Orientation (computer vision) ,Leg length ,primary total hip arthroplasty (THA) ,Surgical planning ,Pre operative ,030218 nuclear medicine & medical imaging ,surgical planning ,03 medical and health sciences ,Hip arthroplasty ,0302 clinical medicine ,Systematic review ,Human anatomy ,3D pre-operative planning ,medicine ,Orthopedics and Sports Medicine ,Surgery ,Medical physics ,Elective surgery - Abstract
Three-dimensional (3D) pre-operative planning in total hip arthroplasty (THA) is being recognized as a useful tool in planning elective surgery, and as crucial to define the optimal component size, position and orientation. The aim of this study was to systematically review the existing literature for the use of 3D pre-operative planning in primary THA. A systematic literature search was performed using keywords, through PubMed, Scopus and Google Scholar, to retrieve all publications documenting the use of 3D planning in primary THA. We focussed on (1) the accuracy of implant sizing, restoration of hip biomechanics and component orientation; (2) the benefits and barriers of this tool; and (3) current gaps in literature and clinical practice. Clinical studies have highlighted the accuracy of 3D pre-operative planning in predicting the optimal component size and orientation in primary THAs. Component size planning accuracy ranged between 34–100% and 41–100% for the stem and cup respectively. The absolute, average difference between planned and achieved values of leg length, offset, centre of rotation, stem version, cup version, inclination and abduction were 1 mm, 1 mm, 2 mm, 4°, 7°, 0.5° and 4° respectively. Benefits include 3D representation of the human anatomy for precise sizing and surgical execution. Barriers include increased radiation dose, learning curve and cost. Long-term evidence investigating this technology is limited. Emphasis should be placed on understanding the health economics of an optimized implant inventory as well as long-term clinical outcomes. Cite this article: EFORT Open Rev 2020;5:845-855. DOI: 10.1302/2058-5241.5.200046 more...
- Published
- 2020
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37. Can 3D surgical planning and patient specific instrumentation reduce hip implant inventory? A prospective study
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Alister Hart, Anna Di Laura, Harry Hothi, and Johann Henckel
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3d planning ,lcsh:Medical physics. Medical radiology. Nuclear medicine ,Hospital setting ,lcsh:R895-920 ,Biomedical Engineering ,Dentistry ,Surgical planning ,030218 nuclear medicine & medical imaging ,03 medical and health sciences ,Hip implant ,Implant cost ,0302 clinical medicine ,Total hip Arthroplasty ,Medicine ,Radiology, Nuclear Medicine and imaging ,Prospective cohort study ,Implant inventory ,030222 orthopedics ,business.industry ,Research ,Computer Science Applications ,Patient specific instrumentation ,Preoperative planning ,Three-dimensional computerised planning ,Implant ,Ct imaging ,business - Abstract
Background Modern designs of joint replacements require a large inventory of components to be available during surgery. Pre-operative CT imaging aids 3D surgical planning and implant sizing, which should reduce the inventory size and enhance clinical outcome. We aimed to better understand the impact of the use of 3D surgical planning and Patient Specific Instrumentation (PSI) on hip implant inventory. Methods An initial feasibility study of 25 consecutive cases was undertaken to assess the discrepancy between the planned component sizes and those implanted to determine whether it was possible to reduce the inventory for future cases. Following this, we performed a pilot study to investigate the effect of an optimized inventory stock on the surgical outcome: we compared a group of 20 consecutive cases (experimental) with the 25 cases in the feasibility study (control). We assessed: (1) accuracy of the 3D planning system in predicting size (%); (2) inventory size changes (%); (3) intra and post-operative complications. Results The feasibility study showed variability within 1 size range, enabling us to safely optimize inventory stock for the pilot study. (1) 3D surgical planning correctly predicted sizes in 93% of the femoral and 89% of the acetabular cup components; (2) there was a 61% reduction in the implant inventory size; (3) we recorded good surgical outcomes with no difference between the 2 groups, and all patients had appropriately sized implants. Conclusions 3D planning is accurate in up to 95% of the cases. CT-based planning can reduce inventory size in the hospital setting potentially leading to a reduction in costs. more...
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- 2020
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38. Management of patients with magnetically controlled growth rods amidst the global COVID-19 pandemic
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Stewart Tucker, Kenneth M.C. Cheung, Colin Nnadi, Martina Tognini, Elisabetta Dal Gal, John A. Skinner, Johann Henckel, Alister Hart, Masood Shafafy, and Harry Hothi
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MAGEC rod ,2019-20 coronavirus outbreak ,Coping (psychology) ,Time Factors ,Medical device ,Coronavirus disease 2019 (COVID-19) ,Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) ,Pneumonia, Viral ,Osteogenesis, Distraction ,Betacoronavirus ,03 medical and health sciences ,Patient safety ,0302 clinical medicine ,Pandemic ,Humans ,Medicine ,Orthopedics and Sports Medicine ,Patient treatment ,Child ,Pandemics ,Infection Control ,030222 orthopedics ,Health Care Rationing ,SARS-CoV-2 ,Forum ,EOS ,business.industry ,COVID-19 ,Prostheses and Implants ,medicine.disease ,Telemedicine ,United Kingdom ,Scoliosis ,Practice Guidelines as Topic ,Magnets ,Surgery ,Patient Safety ,Medical emergency ,Coronavirus Infections ,MCGR ,business ,030217 neurology & neurosurgery - Abstract
Introduction At the time of writing, we are all coping with the global COVID-19 pandemic. Amongst other things, this has had a significant impact on postponing virtually all routine clinic visits and elective surgeries. Concurrently, the Magnetic Expansion Control (MAGEC) rod has been issued with a number of field safety notices and UK regulator medical device alerts. Methods This document serves to provide an overview of the current situation regarding the use of MAGEC rods, primarily in the UK, and the impact that the pandemic has had on the management of patients with these rods. Results and Conclusion The care of each patient must of course be determined on an individual basis; however, the experience of the authors is that a short delay in scheduled distractions and clinic visits will not adversely impact patient treatment. The authors caution against a gap in distractions of longer than 6 months and emphasise the importance of continued remote patient monitoring to identify those who may need to be seen more urgently. more...
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- 2020
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39. Dimensional analysis of 3D-printed acetabular cups for hip arthroplasty using X-ray microcomputed tomography
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Lorenzo Dall’Ava, Alister Hart, Sean Bergiers, Harry Hothi, Paul R. Shearing, Anna Di Laura, and Johann Henckel
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Manufacturing technology ,3d printed ,Materials science ,business.industry ,Scanning electron microscope ,Mechanical Engineering ,3D printing ,02 engineering and technology ,Microcomputed tomography ,021001 nanoscience & nanotechnology ,Coordinate-measuring machine ,01 natural sciences ,Industrial and Manufacturing Engineering ,010309 optics ,Hip arthroplasty ,X-Ray Microcomputed Tomography ,0103 physical sciences ,0210 nano-technology ,business ,Biomedical engineering - Abstract
Purpose Three-dimensional (3D) printing is increasingly used to produce orthopaedic components for hip arthroplasty, such as acetabular cups, which show complex lattice porous structures and shapes. However, limitations on the quality of the final implants are present; thus, investigations are needed to ensure adequate quality and patients safety. X-ray microcomputed tomography (micro-CT) has been recognised to be the most suitable method to evaluate the complexity of 3D-printed parts. The purpose of this study was to assess the reliability of a micro-CT analysis method comparing it with reference systems, such as coordinate measuring machine and electron microscopy. Design/methodology/approach 3D-printed acetabular components for hip arthroplasty (n = 2) were investigated. Dimensions related to the dense and porous regions of the samples were measured. The micro-CT scanning parameters (voltage – kV, current – µA) were optimised selecting six combinations of beam voltage and current. Findings Micro-CT showed good correlation and agreement with both coordinate measuring machine and scanning electron microscopy when optimal scanning parameters were selected (130 kV – 100 µA to 180 kV – 80 µA). Mean discrepancies of 50 µm (± 300) and 20 µm (± 60) were found between the techniques for dense and porous dimensions. Investigation method such as micro-CT imaging may help to better understand the impact of 3D printing manufacturing technology on the properties of orthopaedic implants. Originality/value The optimisation of the scanning parameters and the validation of this method with reference techniques may guide further analysis of similar orthopaedic components. more...
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- 2020
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40. Comparative retrieval analysis of a novel anatomic tibial tray backside: alterations in tibial component design and surface coating can increase cement adhesions and surface roughness
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Dominic T. Mathis, Joshua Schmidli, Felix Amsler, Johann Henckel, Harry Hothi, Alister Hart, and Michael T. Hirschmann
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Rheumatology ,Tibia ,Polyethylene ,Bone Cements ,Humans ,Polymethyl Methacrylate ,Orthopedics and Sports Medicine ,Arthroplasty, Replacement, Knee ,Knee Prosthesis ,Prosthesis Design ,Prosthesis Failure - Abstract
Background With the Persona® knee system a novel anatomic total knee design was developed, which has no pre-coating, whereas the predecessor knee system is pre-coated with polymethylmethacrylate (PMMA). Joint registry data have shown no decrease in risk of aseptic revision of PMMA pre-coated tibial components compared with non-pre-coated implants. The aim of this retrieval study was to compare the amount of cement adhesions, geometry and surface features between the two knee designs and to correlate them with the underlying reason for revision surgery. Methods Retrieval analysis was performed of 15 NexGen® and 8 Persona® fixed-bearing knee implants from the same manufacturer retrieved from two knee revision centres. A photogrammetric method was used to grade the amount of cement attached to the tibial tray backside. The geometry and dimensions of the tibial trays, tray projections and peripheral lips were measured using digital callipers and compared between the two different designs. To measure the surface roughness on the backside of the tibial tray, a contact profilometer was used. To investigate differences between the two designs statistical analyses (t-test) were performed. Results All Persona® trays showed evidence of cement adhesion with a % area of 75.4%; half of the NexGen® trays had cement adhesions, with a mean value of 20%. There was a significant difference in the percentage of area covered by cement between the two designs (p < 0.001). Results from the contact profilometer revealed that Persona® and NexGen® tray backsides showed a similar lateral (1.36 μm and 1.10 μm) and medial (1.39 μm and 1.12 μm) mean surface roughness with significant differentiation (p < 0.05) of the lateral and medial roughness values between the two designs. Persona® stems showed a significantly higher mean surface roughness (1.26) compared to NexGen® stems (0.89; p < 0.05). Conclusion The novel anatomic knee system showed significantly more cements adhesions and a higher surface roughness which was most likely attributed to the most obvious design and coating alteration of the tibial tray. This study provides first retrieval findings of a novel TKA design recently introduced to the market. more...
- Published
- 2021
41. The Performance of MAGEC X Spine Rods: A Comparative Retrieval Study
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Martina Tognini, Harry Hothi, Sean Bergiers, Masood Shafafy, Stewart Tucker, Edel Broomfield, Johann Henckel, and Alister Hart
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Orthopedics and Sports Medicine ,Surgery ,Neurology (clinical) - Abstract
Study Design Multicentre comparative analysis of explanted Spine Magnetically Controlled Growing Rods (MCGRs). Objectives MAGEC X, the latest commercially available generation, was recalled in 2020 due to the risk of post-implantation separation of an actuator end-cap component. Currently, the supply of all MAGEC rods was temporarily suspended in the UK and the EU. Objective of this study is to compare the performance of the MAGEC X MCGR to the earlier MAGEC 1.3 design iteration, by means of retrieval analysis. Methods Fifteen of both MAGEC X and MAGEC 1.3 rods were consecutively collected from five different hospitals following removal surgery and matched by time to removal. Clinical and implant data was collected for all MCGRs. Analysis comprised visual assessments of external damage, plain radiograph evaluations, force and elongation testing, MAGEC X end-cap torque testing and disassembly. Mann-Whitney U tests were used to statistically compare groups. Results Rod distraction reached in vivo was significantly higher in the MAGEC 1.3 ( P = .002). There was no statistically significant difference in the total external damage score ( P = .870), maximum force produced ( P = .695) or distraction reached during force test ( P = .880). No pin fracture was detected. Elongation of stroke was mildly higher ( P = .051) for the MAGEC X implants. One MAGEC X had evident end cap component loosening. Internal damage scores were mildly lower in the MAGEC X group. Conclusion MAGEC X showed similar performance results than the previous design iteration MAGEC 1.3. End-cap component loosening was observed, with no major consequences on the internal mechanism. more...
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- 2022
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42. The effect of metal artefact on the design of custom 3D printed acetabular implants
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Johann Henckel, R Wescott, Harry Hothi, Anna Di Laura, and Alister Hart
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lcsh:Medical physics. Medical radiology. Nuclear medicine ,3d printed ,Custom 3D printed implants ,Metal artefact ,business.industry ,lcsh:R895-920 ,Research ,Implant design ,Revision hip surgery ,Biomedical Engineering ,Dentistry ,Acetabulum ,Computer Science Applications ,Hip revision ,medicine.anatomical_structure ,Paprosky acetabular classification ,Medicine ,Radiology, Nuclear Medicine and imaging ,In patient ,Implant ,business ,Computed tomography ,Pelvis - Abstract
Background 3D Printed custom-made implants constitute a viable option in patients with acetabular Paprosky III defects. In these patients, needing complex hip revision surgery, the appreciation of the bony defect is crucial to assure stable fixation of the customised implant, often intended to replace a failed one. We aimed to understand the effect of metal artefact on the design of customised implants. Methods 26 patients with massive acetabular defects were referred, between May 2016 and September 2018, to our institution classified as “un-reconstructable” by other hospitals. They all received custom 3D-printed acetabular cups. A subset of them underwent two-stage revision surgery due to infection. We then extended the two-stage procedure to the cases where metal artefacts were significantly affecting the reading of the CT scans. CT scans of patients’ pelvises were taken pre and post-implant removal. We assessed for changes in bony shape and volume of the pelvis using 3D imaging software and quantified the effect on implant design with CAD software. Results Eight (out of 26) patients (31%) underwent two-stage revision surgery. The CT bony reconstructions between the two timepoints changed in all cases. The changes were mostly associated to the shape and distribution of the acetabular defects. Three of these cases (37.5%) showed a remarkable difference in the remaining bone that led to a change in implant design. So far, there has been no difference in the clinical outcome between the patients who underwent single (n = 18) and two-stage surgery (n = 8). Conclusions The shape of the acetabulum reconstructed from CT data is potentially altered by metal artefact and bone excised during removal of the failed component. For “end-of-road” acetabular reconstruction, we recommend surgeons consider the use of two-stage surgery to enable a reliable fitting of the complex shape of 3D-printed implants. more...
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- 2020
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43. Does diametrical clearance influence the wear of Pinnacle hip implants?
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John A. Skinner, Alister Hart, Antti Eskelinen, Harry Hothi, Sean Bergiers, Johann Henckel, Tampere University, Clinical Medicine, and Coxa PLC
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Orthodontics ,Pinnacle ,030222 orthopedics ,Hip ,Diametrical clearance ,Materials science ,Bearing (mechanical) ,0206 medical engineering ,02 engineering and technology ,3126 Surgery, anesthesiology, intensive care, radiology ,020601 biomedical engineering ,law.invention ,03 medical and health sciences ,0302 clinical medicine ,Wear ,law ,Orthopedics and Sports Medicine ,Surgery - Abstract
Aims The optimum clearance between the bearing surfaces of hip arthroplasties is unknown. Theoretically, to minimize wear, it is understood that clearances must be low enough to maintain optimal contact pressure and fluid film lubrication, while being large enough to allow lubricant recovery and reduce contact patch size. This study aimed to identify the relationship between diametrical clearance and volumetric wear, through the analysis of retrieved components. Methods A total of 81 metal-on-metal Pinnacle hips paired with 12/14 stems were included in this study. Geometrical analysis was performed on each component, using coordinate and roundness measuring machines. The relationship between their as-manufactured diametrical clearance and volumetric wear was investigated. The Mann-Whitney U test and unpaired t-test were used, in addition to calculating the non-parametric Spearman's correlation coefficient, to statistically evaluate the acquired data. Results The hips in this study were found to have had a median unworn diametrical clearance of 90.31 μm (interquartile range (IQR) 77.59 to 97.40); 32% (n = 26) were found to have been below the manufacturing tolerance. There was no correlation found between clearance and bearing (rs = -0.0004, p = 0.997) or taper (rs = 0.0048, p = 0.966) wear rates. The wear performance of hips manufactured within and below these specifications was not significantly different (bearing: p = 0.395; taper: p = 0.653). Pinnacles manufactured from 2007 onwards had a greater prevalence of bearing clearance below tolerance (p = 0.004). Conclusion The diametrical clearance of Pinnacle hips did not influence their wear performance, even when below the manufacturing tolerance. The optimum clearance for minimizing hip implant wear remains unclear. Cite this article: Bone Joint Res 2020;9(8):515–523. more...
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- 2020
44. Mechanical wear analysis helps understand a mechanism of failure in retrieved magnetically controlled growing rods: a retrieval study
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Holly Morganti, Alister Hart, Sean Bergiers, Harry Hothi, Jack Z. Wei, Elisabetta Dal Gal, Johann Henckel, and Doris Likcani
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lcsh:Diseases of the musculoskeletal system ,genetic structures ,education ,Early detection ,Rod ,03 medical and health sciences ,0302 clinical medicine ,Early-onset scoliosis ,Rheumatology ,Internal mechanism ,Material loss ,Humans ,Medicine ,Orthopedics and Sports Medicine ,Composite material ,030203 arthritis & rheumatology ,030222 orthopedics ,Mechanical wear ,business.industry ,Magnetic expansion control growing rods ,Roundness (object) ,Radiography ,Clinical Practice ,Scoliosis ,Plain radiographs ,sense organs ,lcsh:RC925-935 ,Early onset scoliosis ,business ,Research Article - Abstract
Background To assess the relationship between mechanical wear and the failure of the internal lengthening mechanism in retrieved MAGnetic Expansion Control (MAGEC) growing rods. Methods This study included 34 MAGEC rods retrieved from 20 patients. The state of the internal mechanism and mechanical wear were assessed in all the rods using plain radiographs and visual inspection. Metrology was then performed to assess the topography and mechanical wear of the telescopic bars, using a Talyrond 365 (Taylor Hobson, Leicester, UK) roundness measuring machine. Results Plain radiographs showed evidence of a broken internal mechanism in 29% of retrieved rods. Single-side wear marks were found in 97% of retrieved rods. Material loss was found to significantly increase in rods with a damaged internal mechanism (p r = 0.692, p Conclusions We found an association between damage to the internal mechanism of the rods and (1) patterns of single-side longitudinal wear marks and (2) increased material loss. As the material loss was also found to increase over time of rod in situ, we emphasise the importance of early detection and revision of failed MAGEC rods in clinical practice. more...
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- 2020
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45. Retrieval Findings of Recalled Dual-Taper Hips
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Young-Min Kwon, John A. Skinner, Harry Hothi, Anna Di Laura, Johann Henckel, and Alister Hart
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Adult ,Male ,Medical Device Recalls ,Reoperation ,medicine.medical_specialty ,Scientific Articles ,MEDLINE ,Prosthesis Design ,Risk Assessment ,030218 nuclear medicine & medical imaging ,03 medical and health sciences ,0302 clinical medicine ,Medicine ,Prosthesis design ,Humans ,Orthopedics and Sports Medicine ,Medical physics ,Aged ,Retrospective Studies ,Aged, 80 and over ,030222 orthopedics ,business.industry ,Retrospective cohort study ,General Medicine ,DUAL (cognitive architecture) ,Middle Aged ,Prosthesis Failure ,Surgery ,Female ,Hip Prosthesis ,Risk assessment ,business - Abstract
Background: The recent high-profile recalls of several dual-taper hip designs pose questions regarding why those designs perform poorly. We aimed to characterize taper damage in 1 recalled design to understand failure mechanisms to inform surgeons on which patients should be considered at risk of revision and when to revise. Methods: High-precision measurement equipment was used to characterize the metal loss from the neck-stem interface of 116 retrieved Rejuvenate femoral stems (Stryker Howmedica Osteonics) revised because of an adverse reaction to metal debris. Head-neck taper surfaces were also investigated, and clinical and laboratory data were examined. Results: The neck-stem junction of each implant was moderately to severely corroded and showed a characteristic wear pattern on both male and female taper surfaces. The severity of taper damage was positively correlated with time to revision (coefficient, 0.040 [95% confidence interval (CI), 0.028 to 0.051]; p < 0.0001) and with serum cobalt concentration (coefficient, 0.02 [95% CI, 0.01 to 0.02]; p < 0.0001) and serum chromium concentration (coefficient, 0.04 [95% CI, 0.009 to 0.070]; p = 0.0142). Conclusions: A forensic examination of the retrieved components that failed secondary to an adverse reaction to metal debris showed, in all cases, visible corrosion. Of the implant and patient factors investigated, we did not identify any predictors of corrosion. The severity of damage was found to increase with time; cobalt was significantly elevated over chromium. Clinical Relevance: Surgeons should scrupulously follow and consider revision for patients with this implant design to avoid extensive tissue excision. Blood metal ion tests may aid in identifying the mechanisms of taper corrosion. more...
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- 2018
46. Computed Tomography Techniques Help Understand Wear Patterns in Retrieved Total Knee Arthroplasty
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Arianna Cerquiglini, Paul R. Shearing, Lorenzo Dall’Ava, Michael T. Hirschmann, Johann Henckel, Harry Hothi, and Alister Hart
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Adult ,Male ,Knee Joint ,Surface Properties ,medicine.medical_treatment ,0206 medical engineering ,Total knee arthroplasty ,Computed tomography ,02 engineering and technology ,Cohort Studies ,03 medical and health sciences ,Imaging, Three-Dimensional ,0302 clinical medicine ,medicine ,Humans ,Knee ,Orthopedics and Sports Medicine ,Femur ,Arthroplasty, Replacement, Knee ,Aged ,030222 orthopedics ,Tibia ,biology ,medicine.diagnostic_test ,Orientation (computer vision) ,business.industry ,Reproducibility of Results ,X-Ray Microtomography ,Middle Aged ,biology.organism_classification ,020601 biomedical engineering ,Arthroplasty ,Valgus ,Polyethylene ,Coronal plane ,Radiographic Image Interpretation, Computer-Assisted ,Female ,Implant ,Knee Prosthesis ,Tomography, X-Ray Computed ,business ,Algorithms ,Software ,Ct measurements ,Biomedical engineering - Abstract
Background Suboptimal total knee arthroplasty (TKA) position of both femoral and tibial components is thought to be linked with poor clinical outcomes, polyethylene wear and the “unexplained” painful knee arthroplasty. The aim of this study was to better understand the effect of implant orientation on knee implant performance. Methods We analyzed 30 retrieved contemporary TKA implants. Implant positioning measurements in the coronal plane were made prior to revision using a diagnostic algorithm, based on 3D computed tomography (CT) images. Each retrieved polyethylene component was imaged using a micro-CT scanner and a high resolution computational 3D model of each component was digitally reconstructed. The difference in thickness between medial and lateral components was calculated. Statistical analysis was performed to investigate the association between component positioning and damage patterns. Results We found a significant correlation between both the tibiofemoral and femoral angles and difference in thickness between polyethylene compartments: varus angulations were strongly associated with thinner medial compartments, whilst valgus angulations were associated with thinner lateral compartments. Moreover, suboptimal tibiofemoral orientations and tibial component angulations were associated to greater differences in thickness between polyethylene compartments. Conclusion Our study is the first to compare accurate 3D CT measurements of prerevision TKA positioning in the coronal plane with postrevision retrieval analysis from innovative, accurate and highly reliable micro-CT–based method. Our results demonstrate the impact of component positioning on polyethylene damage and helps understanding of the in vivo performance of these implants. Level of Evidence III. more...
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- 2018
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47. Effect of Bearing Type on Taper Material Loss in Hips From 1 Manufacturer
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Antti Eskelinen, Alister Hart, John A. Skinner, Gordon Blunn, Young-Min Kwon, Harry Hothi, and Johann Henckel
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Male ,Reoperation ,Arthroplasty, Replacement, Hip ,Prosthesis Design ,Imaging data ,030218 nuclear medicine & medical imaging ,law.invention ,Cohort Studies ,03 medical and health sciences ,0302 clinical medicine ,law ,Humans ,Medicine ,Orthopedics and Sports Medicine ,Aged ,Aged, 80 and over ,030222 orthopedics ,Bearing (mechanical) ,business.industry ,Middle Aged ,Prosthesis Failure ,Corrosion ,Metals ,Polyethylene ,Multivariate Analysis ,Metal on polyethylene ,Female ,Hip Joint ,Hip Prosthesis ,Multivariate statistical ,Nuclear medicine ,business - Abstract
BACKGROUND: Numerous studies have reported on clinical significant volumes of material loss and corrosion at the head-stem junction of metal-on-metal (MOM) hips; less is understood about metal-on-polyethylene (MOP) hips. We compared the effect of bearing type (MOM vs MOP) on taper material loss for a hip system of a single design. METHODS: In this cohort study, we recruited retrieved MOM (n = 30) and MOP (n = 22) bearing hips that were consecutively received at our center. We prospectively collected associated clinical and imaging data. We measured the severity of corrosion and volumes of material loss at each head taper surface and used multivariate statistical analysis to investigate differences between the 2 bearing types. RESULTS: The median rate of material loss for the MOM and MOP groups was 0.81 mm3/y (0.01-3.45) and 0.03 mm3/y (0-1.07), respectively (P < .001). Twenty-nine of 30 MOM hips were revised for adverse metal reactions, compared with 1 of 22 MOP hips. CONCLUSION: MOP hips lost significantly less material from their taper junctions than MOM hips. Our results can reassure patients with MOP Pinnacle hips that they are unlikely to experience clinically significant problems related to material loss from the taper junction. more...
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- 2018
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48. Analysing a mechanism of failure in retrieved magnetically controlled spinal rods
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Johann Henckel, Thomas Ember, John A. Skinner, Robert K. Whittaker, Alister Hart, Stewart Tucker, Julian J. H. Leong, Harry Hothi, and Vasiliki C. Panagiotopoulou
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Male ,medicine.medical_specialty ,Bone Nails ,Rod ,03 medical and health sciences ,0302 clinical medicine ,medicine ,Humans ,Orthopedics and Sports Medicine ,Child ,Device Removal ,Retrospective Studies ,030222 orthopedics ,business.industry ,Magnetic Phenomena ,X-Ray Microtomography ,Spine ,Prosthesis Failure ,Surgery ,Corrosion ,Mechanism (engineering) ,Scoliosis ,Microscopy, Electron, Scanning ,Female ,Plain radiographs ,Early onset scoliosis ,business ,030217 neurology & neurosurgery ,Biomedical engineering - Abstract
We aim to describe a mechanism of failure in magnetically controlled growth rods which are used for the correction of the early onset scoliosis. This retrieval study involved nine magnetically controlled growth rods, of a single design, revised from five patients for metal staining, progression of scoliosis, swelling, fractured actuator pin, and final fusion. All the retrieved rods were radiographed and assessed macroscopically and microscopically for material loss. Two implants were further analysed using micro-CT scanning and then sectioned to allow examination of the internal mechanism. No funding was obtained to analyse these implants. There were no potential conflicts interests. Plain radiographs revealed that three out of nine retrieved rods had a fractured pin. All had evidence of surface degradation on the extendable telescopic rod. There was considerable corrosion along the internal mechanism. We found that a third of the retrieved magnetically controlled growth rods had failed due to pin fracture secondary to corrosion of the internal mechanism. We recommend that surgeons consider that any inability of magnetically controlled growth rods to distract may be due to corrosive debris building up inside the mechanism, thereby preventing normal function. more...
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- 2017
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49. Damage Patterns at the Head-Stem Taper Junction Helps Understand the Mechanisms of Material Loss
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Rebecca A. McMillan, Harry Hothi, Paul J. Bills, Andreas C. Panagiotopoulos, Robert K. Whittaker, Alister Hart, and John A. Skinner
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Adult ,Male ,Stem taper ,Arthroplasty, Replacement, Hip ,Total hip replacement ,Prosthesis Design ,03 medical and health sciences ,0302 clinical medicine ,Forensic engineering ,Humans ,Medicine ,Orthopedics and Sports Medicine ,030212 general & internal medicine ,Early failure ,Aged ,Patient factors ,Aged, 80 and over ,030222 orthopedics ,business.industry ,Middle Aged ,R1 ,Prosthesis Failure ,Corrosion ,Metals ,Metal-on-Metal Joint Prostheses ,Trunnion ,Head (vessel) ,Female ,TJ ,Hip Prosthesis ,Implant ,business ,Biomedical engineering - Abstract
Background:\ud Material loss at the taper junction of metal-on-metal total hip replacements (MOM THRs) has been implicated in their early failure. The mechanisms of material loss are not fully understood; analysis of the patterns of damage at the taper can help us better understand why material loss occurs at this junction.\ud Methods:\ud We mapped the patterns of material loss in a series of 155 MOM-THRs received at our centre by scanning the taper surface using a roundness-measuring machine. We\ud examined these material loss maps to develop a five-tier classification system based\ud on visual differences between different patterns. We correlated these patterns to\ud surgical, implant and patient factors known to be important for head-stem taper damage.\ud Results:\ud We found that 63 implants had ‘minimal damage’ at the taper (material loss more...
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- 2017
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50. Factors Associated With Trunnionosis in the Metal-on-Metal Pinnacle Hip
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John A. Skinner, Antti Eskelinen, Alister Hart, Teemu Moilanen, Reshid Berber, Harry Hothi, and Olli Lainiala
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Adult ,Male ,Pinnacle ,Arthroplasty, Replacement, Hip ,02 engineering and technology ,Prosthesis Design ,law.invention ,Bearing design ,03 medical and health sciences ,0302 clinical medicine ,0203 mechanical engineering ,law ,Femoral offset ,Forensic engineering ,Humans ,Medicine ,Orthopedics and Sports Medicine ,Femur ,Device Removal ,Aged ,Orthodontics ,030222 orthopedics ,Bearing (mechanical) ,business.industry ,Implant failure ,Middle Aged ,Prosthesis Failure ,Corrosion ,020303 mechanical engineering & transports ,Metals ,Metal-on-Metal Joint Prostheses ,Trunnion ,Female ,Multiple linear regression analysis ,Hip Prosthesis ,business - Abstract
Background Trunnionosis of the tapered head-stem junction of total hip arthroplasties, either through corrosion or mechanical wear, has been implicated in early implant failure. Retrieval analysis of large numbers of failed implants can help us better understand the factors that influence damage at this interface. Methods In this study, we examined 120 retrieved total hip arthroplasties of one bearing design, the 36-mm diameter metal-on-metal, DePuy Pinnacle, that had been paired with 3 different stems. We measured material loss of the bearing and head-trunnion taper surfaces and collected clinical and component data for each case. We then used multiple linear regression analysis to determine which factors influenced the rate of taper material loss. Results We found 4 significant variables: (1) longer time to revision ( P = .004), (2) the use of a 12/14 taper for the head-trunnion junction ( P P = .003), and (4) vertical femoral offset ( P = .05). These together explained 29% of the variability in taper material loss. Conclusion Our most important finding is the effect of trunnion design. Of the 3 types studied, we found that S-ROM design was the most successful at minimizing trunnionosis. more...
- Published
- 2017
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