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Although various papers have reported on the clinical performance of cup retention with cementation of a new liner and bone grafting in the management of well-fixed cups with polyethylene wear and periacetabular osteolysis after total hip arthroplasty (THA), no systematic review of this topic has been published to date. Medline, EMBASE and Cochrane Library were searched for articles published from January 1999 to January 2019 using “osteolysis” AND “well-fixed”, “osteolysis” AND “retro-acetabular”, “bone graft” AND (“retention” OR “retained” OR “stable”) AND “cup”, and “cemented liner” AND “well-fixed”. Nine articles were selected for review (186 cases, 76.1 months mean follow-up). The overall revision rate was 11.3% (21 hips) most commonly due to aseptic loosening (9/186 hips), dislocation (8/186 hips), and liner wear progression (2/186 cases). The reported square size of osteolytic lesions ranged from a mean of 465.84 mm2 to a max of 4,770 mm2. Almost all reported lesions treated with bone grafts resolved or did not progress 97% (72/74). All studies indicated improved pain and functional scores at follow-up. Cementation of a new liner with periacetabular bone grafting provides an alternative option to isolated liner exchange and cup revision for the management of periacetabular osteolysis in well-fixed cups with a disrupted locking mechanism or unavailable exchange liner. Further higher quality studies are required in order to examine if the use of highly cross-linked polyethylene, highly porous-coated cups, hydroxyapatite-coated cups, and small-diameter cups influence the clinical outcome of liner cementation in well-fixed cups with periacetabular osteolysis.

Aims Prior studies have identified that malseating of a modular dual mobility liner can occur, with previous reported incidences between 5.8% and 16.4%. The aim of this study was to determine the incidence of malseating in dual mobility implants at our institution, assess for risk factors for liner malseating, and investigate whether liner malseating has any impact on clinical outcomes after surgery. Methods We retrospectively reviewed the radiographs of 239 primary and revision total hip arthroplasties with a modular dual mobility liner. Two independent reviewers assessed radiographs for each patient twice for evidence of malseating, with a third observer acting as a tiebreaker. Univariate analysis was conducted to determine risk factors for malseating with Youden’s index used to identify cut-off points. Cohen’s kappa test was used to measure interobserver and intraobserver reliability. Results In all, 12 liners (5.0%), including eight Stryker (6.8%) and four Zimmer Biomet (3.3%), had radiological evidence of malseating. Interobserver reliability was found to be 0.453 (95% confidence interval (CI) 0.26 to 0.64), suggesting weak inter-rater agreement, with strong agreement being greater than 0.8. We found component size of 50 mm or less to be associated with liner malseating on univariate analysis (p = 0.031). Patients with malseated liners appeared to have no associated clinical consequences, and none required revision surgery at a mean of 14 months (1.4 to 99.2) postoperatively. Conclusion The incidence of liner malseating was 5.0%, which is similar to other reports. Component size of 50 mm or smaller was identified as a risk factor for malseating. Surgeons should be aware that malseating can occur and implant design changes or changes in instrumentation should be considered to lower the risk of malseating. Although further follow-up is needed, it remains to be seen if malseating is associated with any clinical consequences. Cite this article: Bone Jt Open 2021;2(10):858–864.

Background The ability to utilize magnetic resonance imaging (MRI) to assess bony fixation in 3 dimensions may allow a better understanding of the implant design and bony integration. We hypothesized that a new 3-dimensionally printed cementless highly porous acetabular component (Stryker Trident II TritaniumTM) would show better fixation than an earlier cup from the same manufacturer as assessed by the noninvasive technique of multispectral MRI. Methods Multiacquisition variable-resonance image combination selective metal suppression MRI was performed in 19 patients implanted with a new 3-dimensionally printed cup and 20 patients who had received a previous-generation cup from the same manufacturer at 1-year follow-up. Each cup was graded globally as well as by 9 specific zones. Integration grades were performed for each zone: 0, full bone integration; 1, fibrous membrane present; 2, osteolysis; and 3, fluid present. A mixed-effects logistic regression model was used to compare fixation between the 2 groups. Results All cups in both cohorts showed greater than 90% radiographically estimated global bony integration (3-dimensionally printed cups, 99.4%; regular cups 91.6%) with no osteolysis or fluid observed in any cup. The 3-dimensionally printed cup had 1 of 171 zones (0.6%) graded as fibrous membrane present, while the 2-dimensional group had 15 of 180 zones (8.3%) graded as fibrous. Of note, screw hole regions were omitted but may be read as fibrous membrane areas. Conclusion Using multiacquisition variable-resonance image combination selective MRI, our analysis showed greater biologic fixation and less fibrous membrane formation in the 3-dimensionally printed cups than the control group at 1-year follow-up.

This study prospectively reports survivorship and radiographic and clinical outcomes following primary elective total hip arthroplasty (THA) using a novel single hemispherical, porous-coated acetabular cup with five different bearing combinations and a minimum of five year follow-up. Continuing post-market release monitoring of this cup, we prospectively enrolled 108 patients (121 THA) between 2009 and 2015. We followed this cohort by examining survivorship, in addition to clinical and radiological outcomes for metal-on-metal (MoM) compared with non-MoM bearing combinations (ceramic-on-ceramic, oxinium-on-polyethylene, ceramic-on-metal, and metal-on-polyethylene). All 108 (121 hips) patients were followed up. Average age at time of surgery was 45.1 years (range 19 to 71 years) of which 42.1% were males. A total of seven (5.8%) cups were revised, all of which were MoM. No osteolysis was observed in any of the patients at the latest visit with a mean follow-up of 9.1 ± 1.7 years (range 4.4–10.7 years). With MoM excluded, survivorship of the cup at five years is 97.8%. Survivorship for MoM implants was 90.0%. Validated hip scores showed significant improvements for all bearing types and no significant difference between groups at latest follow-up (p = 0.614). There was no cup migration with any bearing surface. This cup showed excellent survivorship at five year follow-up, except for patients receiving a MoM articulation. While there were concerns over the early survivorship of this cup, our cohort and joint registry data confirm excellent outcomes.

Purpose Polyethylene (PE) wear remains a common reason for revision surgery following total hip arthroplasty (THA). An established treatment method is isolated liner exchange in a well-fixed acetabular cup and entails a known high risk of hip dislocation after revision surgery. The purpose of this retrospective study was to determine the rate of hip dislocation after liner exchange. Methods Patients were included if (1) the PE liner was removable, (2) the acetabular shell was stable with acceptable orientation, (3) no osteolysis around the acetabular cup was found and (4) no dislocation of the THA occurred before revision surgery. We reviewed medical histories and performed radiological measurements using Einzel-Bild-Röntgen-Analyse (EBRA) software. EBRA measurements and statistical investigations were performed by two independent investigators. Results A total of 82 patients were included in our study. Mean follow-up was six (range: 3.6–9.9) years. In 13 (15.8%) patients THA dislocations occurred at a mean postoperative period of 20.2 (range: 1–44) weeks after revising the PE liner. This is equivalent to an absolute risk increase of 16% after revision surgery, which results in a number needed to harm of 6. This means that every sixth patient with isolated liner exchange can expect to experience dislocation due to wear. Conclusion In conclusion, isolated exchange of the polyethylene liner because of wear showed a high risk of dislocation and further cup revision. Our results suggest that the threshold for revising well-fixed components in the case of liner wear should be lowered. Trial Registration number and date of registration Number: 20140710-1012 and Date: 2016-03-09.

Background The initial stability of press-fit acetabular components is partially determined by the reaming technique. Nonhemispherical (NHS) acetabular shells, which have a larger radius at the rim than the dome, often require larger reaming preparations than the same-sized hemispherical (HS) shells. Furthermore, deeper central reaming may provide a more stable press fit. Using a reproducible, in vitro protocol, we compared initial shell stability under different reaming techniques with HS and NHS acetabular components. Methods Cavities for 54-mm NHS and 56-mm HS acetabular components were premachined in 20-pcf Sawbones blocks. Acetabular cavities included diameters of 54, 55, “54+,” and “55+”. “+” indicates a cavity with a 2-mm smaller diameter that is 2-mm deeper. A 4750N statically applied force seated shells to a height that was comparable with shell height after an orthopaedic surgeon’s manual impaction. Force required to dislodge shells was assessed via a straight torque-out with a linear load. Results Increased preparation depth (+) was associated with deeper shell seating in all groups. Deeper central reaming increased required lever-out force for all groups. Overall, HS and NHS implants prepared with 55 + preparation had the highest lever-out forces, although this was not significantly higher than those with 54+. Conclusions In 20-pcf Sawbones, representing dense bone, overreaming depth by 1-mm improved initial seating measurements. In both HS and NHS acetabular shells, seating depth and required lever-out force were higher in the “+” category. It is unclear, however, whether a decreased diameter ream increased seating stability (55+ vs 54+). Clinically, this deeper central reaming technique may help initial acetabular stability.

A 59-year-old male, diagnosed with advanced arthritis of left hip underwent total hip arthroplasty using a modular dual mobility with metal liner. Post-operative radiographs there was suspicion of incomplete seating of the metal liner inferiorly. The patient was reoperated the next day which confirmed the incomplete seating. The metal liner seating was corrected which was confirmed by intra operative visualization and fluoroscopy. Post-operative radiographs showed complete seating of the liner. Periodic follow ups were uneventful. Incomplete seating of dual mobility metal liner especially at the inferior part, though seldom reported is a possible complication which can lead to early failure.

Background Total hip arthroplasty complications are associated with mechanical loosening of the acetabular component, which may be attributed to the type of fixation used (press fit, trans-cortical screws, cancellous screws). Therefore, the purpose of this study was to compare trans-cortical and cancellous screws to press fit for fixation of the acetabular shell. Methods Five cadaveric pelvis specimens were hemisected (N = 10) at the sacroiliac joint. Each hemi-pelvis was initially tested with a press fit cup followed by the left and right pairs being randomized to either a cancellous or trans-cortical screw condition. Each fixation was tested by applying a load to a rod inserted into the centre of the acetabular cup at 0.5 mm/s, until failure occurred. The failure force, failure moment, and the rotation angle of the cup at failure were calculated. Findings The cups fixated with a trans-cortical screw failed at a significantly greater mean [SD] force (1046.20 [386.52] N). The trans-cortical screws also significantly increased the angle of failure 46.29 (16.90) ° compared to the press-fit cups (6.73 [4.59] °). Finally, there was a significant increase in the failure moment, such that, the trans-cortical condition failed at a mean (SD) moment of 53.75 (16.24) Nm compared to 9.59 (1.85) Nm and 32.15 (18.16) Nm for the press fit and cancellous ( p = 0.044) conditions, respectively. Interpretation The acetabular shells that were fixated with trans-cortical screws provide greater stability compared to the press-fit cups or cancellous screws.

Retention of the acetabular component is an option during conversion from hip resurfacing arthroplasty (HRA) to total hip arthroplasty (THA). The purpose of this study was to compare clinical outcomes of conversion of the femoral resurfacing component with retained acetabular components (RAC) and use of dual-mobility femoral heads to outcomes of patients treated with both component (BC) revisions.A retrospective review was performed of the clinical outcomes of HRA to THA conversions performed at a single institution between 2008 and 2017.Seventy-one conversions were included (27 RAC and 44 BC). Average age at time of conversion was 54.4 years (range, 30-68 years). Median time to conversion was 5.14 (2.77-7.41) years and median follow-up post-conversion was 1.7 (0.33-4.0) years. There were no significant differences in indications for conversion between the 2 groups with the majority performed for complications related to elevated metal ions and aseptic loosening. Harris Hip Scores improved from pre-conversion to post-conversion in both cohorts (P.01). There were no significant differences in pre-conversion and post-conversion metal ion levels between the RAC and BC groups. Serum metal ion levels decreased significantly in both cohorts (P .01). There were 6 additional revisions in the cohort (4 in BC, 2 in RAC) at a median 2.94 (1.99-3.85) years post-conversion. Two RAC patients had intraprosthetic dislocations with extensive polyethylene wear requiring acetabular revision at median 3.92 (3.85-3.98) years post-conversion. Overall, there were a higher number of complications in the BC group related to acetabular fracture, failure of osseointegration, and periprosthetic joint infection; however, this did not reach statistical significance (P = .27).Salvage of an appropriately positioned, well-fixed HRA acetabular component is a reasonable option in the setting of conversion to THA using dual-mobility components. This technique avoids the morbidity of acetabular revision and was associated with a decrease in metal ion levels and improvements in short-term functional outcomes comparable to a BC revision.

Total hip arthroplasty constitutes the operation of the century, although not without complications, which require revision surgery due to loosening, infection, dislocation, and wear. Hereby, we report a rare case of acetabular shell wear misdiagnosed as a dislocation. Patients who underwent total hip arthroplasty with ultra-high molecular weight polyethylene are more vulnerable to excessive wear, and close monitoring can prevent this catastrophic sequence. Timely and accurate diagnosis is mandatory to avoid any unnecessary interventions, such as useless reduction attempts. An anteroposterior radiograph is valuable, although computed tomography can settle the diagnosis with accuracy. Evaluation of any previous radiographic examination is very helpful to highlight any differences. Metal debris shown in the joint space, the bubble sign, and also the eccentric location of the prosthetic head are very helpful signs of the catastrophic wear presented to the X-rays. Since late onset dislocations are rare, orthopedic surgeons should be aware that catastrophic wear of the polyethylene and subsequently the acetabular shell can be presented as a late onset dislocation or protrusion. Furthermore, arthroplasty surgeons should adequately monitor patients who underwent hip arthroplasty with this particular polyethylene type.

Background Cementation of a highly cross-linked polyethylene liner into a well-fixed acetabular shell provided a good durability for liner wear. However, its efficacy in treating recurrent instability due to malposition cup is less reported. The aim of this study is to evaluate the outcome of this surgical technique to treat hip instability. Methods From 2009 to 2019, we have identified 38 patients who had been surgically treated for recurrent instability, including cementation liner (N=20) and revision cup (N=18) procedures. Patients were followed for a mean of 45.66 months. We have recorded and analyzed all causes of implant failure including recurrent instability. Clinical outcomes were assessed including complication and Harris Hip Score (HHS) preoperatively and at the latest follow-up. Results Revision-free survivorship for any cause was 95.0% at 1 year, and 84.4 % at 5 years in cementation liner group and 88.9% at 1 year and 5 years in revision cup group. Mean Harris hip score improved from 48.3 points preoperatively to 79.5 points at the last follow-up in cementation liner group and mean HHS improved from 43.3 points preoperatively to 77.2 points in revision cup group. There were two implant failures in each group, including One is due to persistent hip instability and the other is due to periprosthetic joint infection in the cementation liner group and two implant failure are due to persistent hip instability in the revision cup group. Functional scores and implant survival were similar in both groups. Conclusion We demonstrated that orientation correction via the cementation of the polyethylene liner into well-fixed acetabular shell is a promising option to treat and prevent instability.

CASE We present the results of 3 cases followed up for a minimum period of 4.5 years of revision total hip arthroplasty using a metal acetabular shell with retention of a well-fixed monoblock femoral component by inserting a dual mobility polyethylene bearing onto the femoral head in situ. CONCLUSION This is the first case series to use this technique to address acetabular osteolysis and avoid removing a well-fixed monoblock femoral component at the time of revision surgery.

Background Many surgeons are reluctant to use a constrained liner at the time of acetabular component revision because of concerns that doing so might result in early acetabular component loosening related to high bone-implant interface stresses transmitted from the constrained liner. We hypothesized that, with appropriate initial implant stabilization using highly porous acetabular components with robust supplemental screw fixation, constrained liners could be safely used at the time of acetabular revision. Methods We retrospectively identified 148 revision total hip arthroplasties (THAs) in which a constrained liner of 1 design was cemented into a newly placed highly porous acetabular component fixed with supplemental screws (mean, 5 screws). The mean age at the time of revision THA was 69 years, and 68% of the patients were female. The most common indications for revision were 2-stage reimplantation (33%), recurrent dislocation (30%), and aseptic loosening of the acetabular component (22%) or both the acetabular and femoral components (9%). The mean duration of follow-up was 7 years. Results There were no failures at the bone-implant interface. No cases of acetabular metal shell loosening were identified on radiographic analysis. The 10-year survival rates with acetabular revision and any reoperation as the end points were 75% and 67%, respectively. Overall, 33 hips (22%) required revision or reoperation because of infection or wound complications (n = 12), dislocation or mechanical failure of the constrained liner (n = 11), periprosthetic femoral fracture (n = 4), femoral loosening (n = 3), or other reasons (n = 3). The 10-year survival rate with re-revision for instability as the end point was 88% overall, which was similar to the 85% 10-year survival rate with re-revision for instability as the end point among hips that were specifically revised because of instability during index revision THA (p = 0.9). Conclusions Implanting a constrained liner at the time of acetabular revision in high-risk patients resulted in no cases of aseptic metal acetabular component loosening in this large series. This finding is likely related to the fact that a highly porous acetabular component was utilized with robust supplemental screw fixation in each case. Such information is valuable as these data favor a paradigm shift when compared with some traditionally held tenets. Level of evidence Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Background Templating for preoperative planning of joint arthroplasty has followed the evolution of digital templating software. Objective This study aims to provide a safe, reliable and reproducible method for prediction of acetabular component size based on measurement of the radiographic femoral head diameter, with the aid of templating software. Methods A defined methodology for femoral head measurement was applied to 97 consecutive, calibrated digital pelvic radiographs. Based on radiographic femoral head diameter, the minimum acetabular shell diameter was calculated and then compared to the size of the implanted acetabular shells. Results This method predicted safe minimum acetabular component size with an accuracy of 95.9% with a high inter-observer reliability of 97.6%. Conclusions This study presents a simple, reproducible and accurate method for templating of the minimum safest acetabular component diameter.

Purpose The purpose of this paper is to improve the manufacturing of a prosthetic acetabular shell by analyzing the main factors leading to failure during the selective laser melting (SLM) additive manufacturing (AM) process. Design/methodology/approach Different computer-aided design and computer-aided manufacturing processes have been applied to fabricate acetabular parts. Then, various investigations into surface quality, mechanical properties and microstructure have been carried out to scrutinize the possible limitations in fabrication. Findings Geometrical measurements showed 1.59 and 0.27 per cent differences between the designed and manufactured prototypes for inside and outside diameter, respectively. However, resulting studies showed that unstable surfaces, cracks, an interruption in powder delivery and low surface quality were the main problems that occurred during this process. These results indicate that SLM is an accurate and promising method for production of intricate shapes, provided that the appropriate settings of production conditions are considered to minimize possible limitations. Originality/value The contributions of this paper are discussions covering different issues in the AM fabrication of acetabular shells to improve the mechanical properties, quality and durability of the produced parts.

This is a prospective data collection across seven centers in a non-randomized, post- market study where an additive manufactured cementless acetabular shell was used in primary total hip arthroplasty. There was a total of 254 hips/246 patients across seven centers. Clinical outcomes including all-cause survivorship, the Harris Hip Score (HHS), Lower Extremity Activity Scale (LEAS), Veterans Rand 12 (VR-12), EuroQol 5D (EQ- 5D) and radiographs were collected pre- and postoperatively. Radiographs were analyzed for presence of radiolucencies, migration and overall cup stability. All-cause survival rate was 99.61% and there were no reported radiolucencies greater than 2mm for any zone. There was a reduction in radiolucencies from the 6-week to 1-year postoperative timeframe. All cups reviewed at 1-year were stable with no radiolucencies in 96% of hips. These early results demonstrate the favorable properties of this shell and the use of additive manufacturing in orthopaedic surgery.

Dissociation of the polyethylene liner from the acetabular shell is a rare but catastrophic complication of total hip arthroplasty (THA). There have been reports of polyethylene liner dissociation (PLD) as well as ceramic liner dissociation (CLD) in the literature. Amongst the commonly used implants, liner dissociation has been reported with the Pinnacle (DePuy), Harris–Galante (Zimmer) and Trident (Stryker) acetabular components. To the best of our knowledge, this is the first case report of PLD in an R3 (Smith & Nephew) acetabular component. This case report highlights the implant choice for treatment of the liner dissociation and the role of constrained implants in such cases.

AimsModular dual mobility (DM) prostheses in which a cobalt-chromium liner is inserted into a titanium acetabular shell ( vs a monoblock acetabular component) have the advantage of allowing supplementary screw fixation, but the potential for corrosion between the liner and acetabulum has raised concerns. While DM prostheses have shown improved stability in patients deemed ‘high-risk’ for dislocation undergoing total hip arthroplasty (THA), their performance in young, active patients has not been reported. This study’s purpose was to assess clinical outcomes, metal ion levels, and periprosthetic femoral bone mineral density (BMD) in young, active patients receiving a modular DM acetabulum and recently introduced titanium, proximally coated, tapered femoral stem design.Patients and MethodsThis was a prospective study of patients between 18 and 65 years of age, with a body mass index (BMI) < 35 kg/m2and University of California at Los Angeles (UCLA) activity score > 6, who received a modular cobalt-chromium acetabular liner, highly crosslinked polyethylene mobile bearing, and cementless titanium femoral stem for their primary THA. Patients with a history of renal disease and metal hardware elsewhere in the body were excluded. A total of 43 patients (30 male, 13 female; mean age 52.6 years (sd 6.5)) were enrolled. All patients had a minimum of two years’ clinical follow-up. Patient-reported outcome measures, whole blood metal ion levels (ug/l), and periprosthetic femoral BMD were measured at baseline, as well as at one and two years postoperatively. Power analysis indicated 40 patients necessary to demonstrate a five-fold increase in cobalt levels from baseline (alpha = 0.05, beta = 0.80). A mixed model with repeated measures was used for statistical analysis.ResultsMean Harris Hip Scores improved from 54.1 (sd 20.5) to 91.2 (sd 10.8) at two years postoperatively (p < 0.001). All patients had radiologically well-fixed components, no patients experienced any instability, and no patients required any further intervention. Mean cobalt levels increased from 0.065 ug/l (sd 0.03) preoperatively to 0.30 ug/l (sd 0.51) at one year postoperatively (p = 0.01) but decreased at two years postoperatively to 0.16 ug/l (sd 0.23; p = 0.2). Four patients (9.3%) had a cobalt level outside the reference range (0.03 ug/l to 0.29 ug/l) at two years postoperatively, with values from 0.32 ug/l to 0.94 ug/l. The mean femoral BMD ratio was maintained in Gruen zones 2 to 7 at both one and two years postoperatively using this stem design. At two years postoperatively, mean BMD in the medial calcar was 101.5% of the baseline value.ConclusionUse of a modular DM prosthesis and cementless, tapered femoral stem has shown encouraging results in young, active patients undergoing primary THA. Elevation in mean cobalt levels and the presence of four patients outside the reference range at two years postoperatively demonstrates the necessity of continued surveillance in this cohort. Cite this article: Bone Joint J 2019;101-B:365–371.

Liner dissociation of polyethylene from a cementless acetabular socket following total hip arthroplasty (THA) is a rare complication. Cross-linked polyethylene liner dissociation from AMS-HA shell (KYOCERA Med, Osaka, Japan) occurred in 2 out of the 4153 (0.04%) cases approximately 10 years after undergoing surgery at our institute. First case was an 80-year-old female who underwent right THA along with subtrochanteric femoral shortening osteotomy due to complete dislocation hip, and second case was a 72-year-old male, who underwent right THA due to coxarthrosis. A 26 mm femoral head and CPE liner were used in both cases and the inclination degree of the acetabular socket was within 50°.There was no implant loosening in both cases. There was partial damage in the elevated rim on the alternative side and scratches on the back side in the both extracted CPE liner. It was surmised that liner dissociation was caused due to a problem in the liner fixing format of the push in type of the present model.

Background Highly cross-linked polyethylene in total hip arthroplasty (THA) has been shown to decrease wear rate compared with a conventional polyethylene liner. However, it has also been reported that the manufacturing processes can cause early failure of the implant. Case We describe early catastrophic failure at Conclusions We conclude that a malpositioned acetabular shell resulting in point loading and abnormal contact stresses was the mechanism of failure. Our case highlights the importance of achieving correct acetabular component alignment in total hip arthroplasty.

Additive Manufacturing (AM) includes a range of approaches that correlate with computer aided design (CAD) and manufacturing by fabrication via precise layers and is a promising method for the production of medical tools. In this study, different aspects and mechanisms of solidification for curved surfaces based on equilibrium at curved interfaces, Monge patch, interfacial and Gibbs energy will be discussed. Also, the effect of capillarity, geometry, substrate temperature, cooling rate and scanning parameters in the solidification of a prosthetic acetabular cup (PAC) using selective laser melting (SLM) is analysed. The contributions of this work are analysing solidification and effective factors in this process to produce parts with a higher quality and mechanical properties such as strength, strain, porosity, relative density and hardness. Results indicate that due to the surface to volume (S/V) ratio, and the increasing effect of the radius on Monge patch, thermal stresses and surface forces are more prevalent on outer surfaces. Moreover, solidification and mechanical properties are related to capillarity, geometry, substrate temperature, cooling rate, scanning power and speed. The results also indicate the interaction of solute diffusion and heat transfer with interatomic forces in large S/V ratio and at small scales tend to improve solidification. Keywords: Acetabular shell, Gibbs free energy, Selective laser melting, Surface energy, Solidification, Thermal stress

Background Large-diameter, monoblock acetabular components have been used for both hip resurfacing arthroplasty and metal-on-metal (MoM) total hip arthroplasty (THA). If revision is required, one solution is to retain the shell and use a dual-mobility bearing. Methods We reviewed the results of 25 revision THAs including 11 hip resurfacing arthroplasty and 14 MoM THAs where a monoblock acetabular component was mated to a dual-mobility bearing. Results At a mean of 29 months, there was one failure, an intraprosthetic dislocation of the dual-mobility bearing. There was a significant decrease in serum metal ion levels postoperatively. Conclusion Retention of a well-fixed, monoblock MoM acetabular shell and mating it to a dual-mobility bearing in the setting of revision surgery seems to be a reasonable, low-morbidity option at short-term follow-up in appropriately positioned cups.

A 75-year-old woman who suffered a left femoral neck fracture underwent a left total hip arthroplasty using a Stryker Trident (Kalamazoo, MI) hemispherical acetabular shell and Modular Dual Mobility (MDM) metal liner. Post-operative radiographs demonstrated canted seating of the liner. The patient was taken immediately back to the operating room where the acetabular liner appeared well seated superiorly but was in a canted position inferiorly. Removal and replacement was performed and post-operative radiographs demonstrated complete seating. Subsequent follow up at 6 months demonstrated good clinical function with no adverse radiographic findings. Canted seating is a potential complication of the MDM metal liner. Providers should be aware of potential incomplete seating inferiorly despite the superior portion of the liner being well seated.

Background: Hip resurfacing arthroplasty (HRA) typically uses a hybrid design (cemented femoral component and cementless acetabular shell) but has recently been performed with fully cementless components. There is a paucity of information on the clinical performance of these cementless designs. Methods: The UCLA clinical scores, SF-12 quality of life scores, complication rates, survivorship and radiographic signs of loosening or gross stress shielding of 39 hips (39 male patients) implanted with cementless HRA were compared with those of 40 hips (37 male patients) implanted with hybrid HRA during the same time frame. Results: There were no significant differences in postoperative clinical and quality of life scores, complication rates, or radiographic signs of loosening between the 2 groups. The 5-year Kaplan-Meier survivorship was 97.2% for the cementless group and 100% for the hybrid group. This difference was not significant ( p = 0.3694). There were no femoral component failures in any of the 2 groups. Conclusions: At a mean follow-up of 6 years, there is no tangible difference between the performance of cementless HRA compared to hybrid HRA. The absence of learning curve associated with this device and the potential for better preservation of femoral neck bone mineral density suggest that this technology is well suited for young patients with good bone quality seeking to resume an active lifestyle including high-impact activities.

As the demand for total hip arthroplasty (THA) continues to increase, the burden of revision THA is also expected to increase. Although the quality of polyethylene has improved markedly, osteolysis continues to be a risk for older designs and younger, active patients. Although progressive but typically asymptomatic in early stages, osteolysis can result in component failure and complicate revision surgery. Serial radiographs are paramount for monitoring progression. Although select cases may be treated with observation, surgery should be considered based on age, activity level, and projected life span. Well-fixed, noncemented modular acetabular components may be treated with curettage and bone grafting, as well as having to bear liner exchange with retention of the acetabular shell. However, in the setting of osteolysis, it is controversial whether bone grafting and component retention is superior to cup revision. This review explores the pathophysiology of osteolysis after THA and provides a comprehensive analysis of the evaluation and treatment of patients with osteolysis.

SummaryComponent malalignment and impingement are possible causes of recurrent luxation following total hip replacement in the dog. In the two cases presented in this report, luxation that was probably due to impingement was managed by exchanging the standard 17 mm prosthetic head for a 24 mm prosthetic head. This required removal of the original acetabular cup liner and placement of a new polyethylene liner that would accept the 24 mm head into the stable acetabular shell. In the first case, a 50 kg Malamute dog, recurrent luxation was initially managed by component alignment revision, iliofemoral suture, triple pelvic osteotomy and a novel lasso technique, without long-term success. After exchanging the head and cup liner, luxation did not recur over a 12-month period. In the second case, a 65 kg Newfoundland dog, impingement was suspected after a second luxation event. Luxation did not recur during the nine months after exchange of the head and cup liner. The larger prosthetic head used in these two cases increased the impingement-free range-of-motion of the joint and increased the translation distance required for luxation (jump distance).

This multicenter study evaluated survivorship, functional outcomes, complications, and radiographic outcomes for patients who underwent total hip arthroplasty using a newly developed highly porous 3-dimensional titanium implant. Excellent aseptic (99.6%) and all-cause (98%) survivorship and functional outcomes were found at 3-year follow-up. This highly porous acetabular shell holds promise in total hip arthroplasty. [ Orthopedics. 2018; 41(1):e154–e157.]

This is a relatively new technique that provides a viable option for the treatment of complex severe acetabular defects and pelvic discontinuity [1]. A porous trabecular metal acetabular shell (titanium and tantalum) and a bridging ilioischial cage are used to achieve mechanical construct stability and biologic fixation of the acetabular shell [2]. It was first presented at the 2007 annual meeting of American Association of Orthopaedic Surgeons [3, 4].

Cementation of a polyethylene liner into the well-fixed shell is a convenient option for revision total hip arthroplasty. We retrospectively reviewed 45 patients who had liner cementation to investigate the risk factors which gave rise to major complications and reoperation. Patients were observed for a minimum of 7 years (range 7.8-14 years). Relevant risk factors (age, BMI, surgical approach, previous cup size and position, types of coated surface) were assessed with Cox regression analysis. The mean Harris Hip Score was improved from 62.5 (range 57-68) preoperatively to 87.1 (range 70-97). A total of 7 hips (15.5%) had acetabular component loosening that was treated with reoperation. Prevalence of acetabular component loosening was statistically significantly higher in hydroxyapatite-coated group (5 of 13) than in the Ti-coated group (2 of 32, p = 0.015). All recurrent dislocations occurred in patients treated with a posterior approach. Diameter of the previous metal shell of below 54 mm showed a lower 10-year survival rate than those greater than 54 mm in diameter. PE liner cementation in stable metal cup is a useful alternative option for carefully selected patients. Pre-existing HA-coated cups as well as small sized cups were indicative of poor outcomes.

The present study was undertaken to document outcomes of cementation of a highly cross-linked polyethylene (PE) liner into a well-fixed acetabular metal shell in 36 hips. All operations were performed by a single surgeon using only one type of liner. Patients were followed for a mean of 6.1 years (range, 3-8 years). Mean Harris hip score improved from 58 points preoperatively to 91 points postoperatively. There were no cases of PE liner dislodgement or progressive osteolysis. 1 hip (2.8%) required revision surgery for acetabular cup loosening with greater trochanteric fracture. Complications included 1 peroneal nerve palsy and 1 dislocation. The results of this study and previous reports demonstrated that cementation of highly cross-linked PE liner into well-fixed metal shell could provide good midterm durability.

Metal-on-metal (MoM) bearings with a cemented femoral component and a cementless acetabular shell has historically been the gold standard for fixation in surface arthroplasty (SA) of the hip. Lately, there has been an increase in the availability of cementless femoral fixation. Since there is a paucity of literature on the clinical performance of modern generation cementless designs in SA, we aimed to perform a review of the literature on this type of fixation, as well as to report our institutional mid-term survival with a MoM cementless hip design. A comprehensive literature search provided information on joint arthroplasty registries, case-series, case-controlled studies and randomized controlled-trials reporting on the performance of hip resurfacings with cementless femoral fixation and its comparison with cemented fixation. Even though initial attempts of cementless femoral fixation showed high failure rates in the early 1990s, modern cementless porous-coated designs have proven to be non-inferior, with excellent mid- and long-term results in terms of survival and clinical outcomes. Our experience showed a two-, five-, and eight-year survivorships of 99.6% (95% CI: 98.8–100%), 98.3% (95% CI: 96.3–100%), and 98.3% (95% CI: 96.3–100%), respectively; with only 2 aseptic femoral failures. In SA of the hip, cementless femoral fixation has evolved in such a fashion that is the fixation of choice for SA in many centers. Modern implants have similar outcomes to that of cemented fixation in the early to mid-term. However, long-term clinical outcomes are still necessary to determine whether these results will continue or surpass that of cemented femoral fixation in SA.

In this article, we present a 48-year-old female case who had an unsuccessful previous forte ceramic-on-ceramic total hip arthroplasty for early coxarthrosis secondary to acetabular dysplasia. She had fracture and protrusion of the ceramic liner through the titanium acetabular shell without any apparent trauma, possibly resulting from the mistake during the implantation of the ceramic liner into the metal shell in the initial operation. The patient had no other risk factors (component malposition, trauma, malalignment) for ceramic liner fracture. She underwent revision surgery with allograft, reinforcement ring, all-polyethylene cup and reinforced stainless-steel femoral head.

Total hip arthroplasty (THA) has been associated with excellent functional outcomes and survival rates (Cushner et al., 2010 [1]). Selection of acetabular shell and technique of implantation is an important factor as is the stem for a successful THA. Both cemented all-polyethylene cups and cementless sockets have benefited from improvements in surgical techniques, cup designs, and bearing surfaces. This paper is a review of the current literature that focuses on the options for the acetabular components of a modern total hip replacement, aiming to answer common questions and controversies on this topic.

Trabecular metal (TM) augments are a relatively new option for reconstructing segmental bone loss during acetabular revision. We studied 34 failed hip replacements in 34 patients that were revised between October 2003 and March 2010 using a TM acetabular shell and one or two augments. The mean age of the patients at the time of surgery was 69.3 years (46 to 86) and the mean follow-up was 64.5 months (27 to 107). In all, 18 patients had a minor column defect, 14 had a major column defect, and two were associated with pelvic discontinuity. The hip centre of rotation was restored in 27 patients (79.4%). The Oxford hip score increased from a mean of 15.4 points (6 to 25) before revision to a mean of 37.7 (29 to 47) at the final follow-up. There were three aseptic loosenings of the construct, two of them in the patients with pelvic discontinuity. One septic loosening also occurred in a patient who had previously had an infected hip replacement. The augments remained stable in two of the failed hips. Whenever there was a loose acetabular component in contact with a stable augment, progressive metal debris shedding was evident on the serial radiographs. Complications included another deep infection treated without revision surgery. Good clinical and radiological results can be expected for bone-deficient acetabula treated by a TM cup and augment, but for pelvic discontinuities this might not be a reliable option.Cite this article: Bone Joint J 2013;95-B:166–72.

Aim To evaluate the clinical performance of a polycarbonate-urethane liner as a bearing material inside a cobalt-chrome acetabular shell. Methods Between December 2007 and July 2011, this material combination was used in 27 total hip replacement patients, most of whom had an indication of osteoarthritis. This report focuses on the first 5-year results of the clinical use of this material combination in the TriboFit® Hip System. Results Mean Harris Hip Score showed significant improvement from 40 to 86 after 5 years, similar to studies in the literature. No adverse events - revisions or complications - or disadvantages that have been reported for other total hip materials were observed over the 5-year period. The radiographs showed no signs of wear, migration or loosening of the implants. Conclusions These early results indicate this new material combination offers promise as a safe and effective alternative bearing material for use in total hip systems. Further clinical trials are necessary to reconfirm these findings.

Background: Dissociation of the polyethylene liner from the acetabular shell is an uncommon event. Offset, face-changing polyethylene liners theoretically increase femoral head coverage, allow for larger heads with smaller cup diameters, and offer improved stability without risk of impingement. However, we present four cases of liner dissociations from the acetabular shell that necessitated revision hip surgery. Methods: Four patients with spontaneous dissociations of offset, face-changing polyethylene acetabular liners underwent revision hip arthroplasty between January 2007 and June 2010. All patients were women with an average age of fifty-three years. All cases involved the combination of a Pinnacle acetabular component with an offset, face-changing polyethylene liner. We reviewed the presenting signs and symptoms associated with liner dissociations and analyzed the radiographs for the acetabular component position. Results: All cases of liner dissociation occurred without direct trauma and were associated with squeaking sounds reported by the patient. The average cup abduction angle was 55° (range, 51° to 60°) and the average anteversion was 21.5° (range, 17° to 24°). Examination of the dissociated liners at the time of revision surgery revealed plastic deformation of the polyethylene liner rim posterosuperiorly at the eleven o’clock position on the right hip and the one o’clock position on the left hip. Conclusions: The combination of a vertically positioned acetabular component and an offset, face-changing liner resulted in impingement and dissociation of the liner from the shell in four patients. Proper acetabular component positioning, rather than the routine use of uniquely designed polyethylene liners, is critical to maximizing implant stability in total hip arthroplasty. Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

This study reports minimum 5-year results of 95 hips implanted with a Pinnacle (DePuy, Warsaw, Ind) modular metal-on-metal acetabular prosthesis. Clinical scores such as the Harris Hip and Western Ontario and McMaster Universities Arthritis Index revealed excellent clinical outcomes at mean 6-year follow-up. With the use of large-diameter femoral heads, dislocation was rare, occurring in only 1 hip. Moreover, no acetabular and only 3 femoral osteolytic lesions were detected. Kaplan-Meier survivorship at 7 years after arthroplasty was 97.8% for the total hip arthroplasty construct and 100% for the acetabular shell. No unexplained pain or other complication attributable to wear debris or the metal-on-metal articulation was observed. These findings indicate that total hip arthroplasty with this specific modular metal-on-metal bearing performed well in a high-demand population at midterm follow-up.

Smaller head sizes and head/cup ratios make cups smaller than 50 mm and larger than 58 mm, more prone to dislocation. Using computer modeling, we compared average head sizes and posterior horizontal dislocation distance (PHDD) in two 78-patient matched cohorts. Cup sizes were small (≤ 50 mm) or large (≥ 58 mm). The control cohort had conventional fixed bearing prostheses, while the experimental cohort had anatomical dual mobility (ADM) hip prostheses. ADM cups have larger average head sizes and PHDD than traditional fixed bearing prostheses by 11.5 mm and 80% for cups ≤ 50 mm, and 16.3 mm and 90% for cups ≥ 58 mm. Larger head sizes and increased head/cup ratio may allow the ADM prosthesis to reduce the incidence of dislocation.

The acetabular shell mobilization is the main long-term complication in total hip replacement. Metal-back fracture has also to be considered among the possible causes of shell mobilization. A case is presented of bilateral acetabular shell mobilization due to the trabecular covering de-soldering from the metal-back in a 43 year-old patient, 13–14 years after the first surgery.

The highly cross-linked polyethylene liners currently used with modular uncemented cups have substantially decreased wear and osteolysis at early follow-up. However, retroacetabular osteolysis has still been reported in some cases with DePuy Orthopaedic's (Warsaw, IN) second-generation Duraloc acetabular shell. DePuy's third-generation Pinnacle cup incorporates a different shell-liner locking mechanism. We compared the clinical outcome among a matched series of 42 Duraloc and 42 Pinnacle cups at a mean follow-up of 5.9 years. Although the Harris Hip Scores and wear rates were not statistically different between the 2 cup designs, retroacetabular osteolysis behind the central hole was absent among the Pinnacle cups but noted among 19% of the Duraloc cups.

Cementation of a liner into a well-fixed acetabular shell is common in revision hip arthroplasty. We compare the biomechanical strengths of cemented liners with standard locked liners. Fifty polyethylene liners were inserted into acetabular shells using the standard locking mechanism or 1 of 2 cement types then loaded to failure by torsion or lever-out testing. Lever-out testing showed that all cemented liners failed at similar loads to standard locked liners. With torsion testing, cemented liners failed at significantly higher loads than standard locked liners; roughening the liner increased load to failure. Cementation of an acetabular liner into a metal shell is safe and strong and a good alternative to metal shell replacement. Saw roughening of the polyethylene liner strengthens the poly-cement interface.

The fracture rate of third-generation ceramic liners is greatly reduced compared with first- and second-generation liners because of improvement in the design and manufacturing process. The ABC® (alumina-bearing couple) ceramic liner is one such design, and fracture of this type of liner has not been reported. We report three cases of fracture of an ABC® ceramic liner occurring within 3 years of implantation. The liner was broken into multiple pieces in two patients, whereas in one patient it was broken only in its periphery. These patients were treated with debridement and cementation of the metal-inlay polyethylene liner into the retained acetabular shell.

As the number of revision hip arthroplasties continues to increase, alternative reconstructive options may be necessary. Cementation of a polyethylene liner into a well-fixed metal acetabular shell has previously been reported to save bone stock and enhance the pullout strength. This study analyzed whether cementation of various types of mechanically modified or nonmodified liners into a metal shell altered wear characteristics when compared with noncemented modular liners. The authors used nonirradiated and highly cross-linked polyethylene liners that were mechanically modified or left unmodified. Wear in both nonirradiated and highly cross-linked liners was not affected by the cementing process. Wear of the highly cross-linked polyethylene liners was significantly less when compared with the nonirradiated liners. This laboratory study provides quantitative data supporting previous qualitative studies of cementing a polyethylene liner into a metal-backed acetabular shell. Based on this study, cementation of a mechanically modified liner did not affect wear in this study, which simulated 3 years of activity.

Avoiding or diminishing bone stock loss in hip revision surgery is one of the main concerns of a surgeon. The surgical procedure must be safe, non-traumatic, reproducible, reliable, and if possible with the lowest or minimum cost. We present an easy technique of polyethylene liner extraction in hip revision surgery, reviewing other common extraction methods. The method depicted here has been used by the authors for years in many occasions where the liner is to be removed while preserving the acetabular shell.

Although it is understood that backside damage occurs in polyethylene acetabular liners, the effect of highly crosslinked polyethylene, which has completely replaced conventional polyethylene, has yet to be examined. The purpose of this study was to answer the following questions: (1) With conventional polyethylene (CPE), did the acetabular design make a difference in backside wear? (2) Is there a difference in backside damage between CPE and crosslinked polyethylene (XLPE) liners? (3) With XLPE, is the difference in backside wear between designs still present? (4) Is there any difference in backside damage in various zones on backside of individual liners? This single-institution retrieval analysis involved visual damage scoring on the backside of 233 polyethylene liners implanted between 2002 and 2011. The liners were retrieved from either polished/dovetail cups (PD) or roughened/wire cups (RW) made by two different manufacturers. The inserts were divided into four groups: PD-CPE (n = 105), PD-XLPE (n = 16), RW-CPE (n = 99), and RW-XLPE (n = 13). Aseptic loosening and polyethylene wear were the predominant reasons for revision of CPE liners, whereas instability and infection were the common reasons for revision of XLPE liners. The time in situ (TIS) was shorter for the XLPE liners as compared with the CPE liners (PD-CPE: 8.5 years [SD 4.4]; RD-CPE: 9.5 [SD 4.8]; PD-CPE: 3.8 [SD 3.7]; RD-XLPE: 4.0 [SD 4.3]). The backside of each liner was divided into five zones and graded initially from a scale of 0 to 3 for seven different damage modes by one observer. There was substantial interobserver (kappa 0.769) and intraobserver (0.736) reliability on repeat scoring. To compare the effects of crosslinking, a subset of the conventional polyethylene liners was matched to the crosslinked liners based on TIS, resulting in 16 per group for the two PD types and 13 per group for the two RW types. Total damage scores in the RW-CPE (19 ± 7) group were greater (p

Constrained acetabular components have been used to treat certain cases of intraoperative instability and postoperative dislocation after total hip arthroplasty. We report our experience with a tripolar constrained component used in these situations since 1988. The outcomes of the cases where this component was used were analyzed for component failure, component loosening, and osteolysis. At average 10-year followup, for cases treated for intraoperative instability (2 cases) or postoperative dislocation (4 cases), the component failure rate was 6% (6 of 101 hips in 5 patients). For cases where the constrained liner was cemented into a fixed cementless acetabular shell, the failure rate was 7% (2 of 31 hips in 2 patients) at 3.9-year average followup. Use of a constrained liner was not associated with an increased osteolysis or aseptic loosening rate. This tripolar constrained acetabular liner provided total hip arthroplasty construct stability in most cases in which it was used for intraoperative instability or postoperative dislocation.

Background: During revision hip replacement surgery, the cementless acetabular shell is often well fixed but the locking mechanism may be ineffective. Cementing a new liner into the existing acetabular shell (the double-socket technique) can provide a simple solution. The purposes of the present study were to review our initial clinical results and to define the potential limitations of this technique. Methods: Thirty-two hips with a preexisting well-fixed acetabular socket that had been in situ for an average of 8.6 years were treated with the insertion of a new polyethylene liner (seventeen hips) or a metal liner (fifteen hips) with use of cement. The indication for this technique was a deficient locking mechanism in twenty-two hips and the unavailability of a matching liner in ten hips. Anteroposterior radiographs of all hips were analyzed by a single independent reviewer. Results: The mean duration of follow-up was 5.1 years. Six hips required a reoperation after a mean of 29.7 months; the reasons for the reoperations included aseptic failure of the acetabular construct (four hips), instability (one hip), and sepsis (one hip). The University of California at Los Angeles hip scores improved significantly (p < 0.001) compared with the preoperative values; specifically, the mean score improved from 6.2 to 9.1 for pain, from 6.3 to 8.3 for walking, from 6.2 to 7.8 for function, and from 4.7 to 5.8 for activity. The prevalence of dislocation was 22%. Kaplan-Meier analysis with revision as the end point revealed a five-year survival rate of 78% (95% confidence interval, 55% to 91%). Conclusions: The double-socket technique is a good alternative to acetabular socket removal for suitable candidates who have a well-fixed cementless socket with an inner diameter that is larger than the outer diameter of the cemented liner. This technique preserves acetabular bone stock and permits conversion to alternate bearing surfaces. We believe, however, that removal of a well-fixed acetabular shell or the use of a constrained liner should be strongly considered for patients with a history of hip instability. Level of Evidence: Therapeutic study, Level IV (case series [no, or historical, control group]). See Instructions to Authors for a complete description of levels of evidence.

We report a complication during total hip arthroplasty using an uncemented press-fit acetabular shell and ceramic liner for a woman with osteoarthritis. Fracture of the ceramic liner occurred during its insertion owing to non-concentric reduction. The main body of the ceramic liner became wedged in the acetabular shell and was resistant to removal. The shell itself was immovable owing to the prior insertion of 2 polyaxial screws, to which access was covered. Successful removal involved drilling a hole in the ceramic liner as a stress riser, and then cracking the liner with a Steinman pin.

To minimize the morbidity associated with revision of a well-fixed acetabular shell, some surgeons advocate cementing a polyethylene liner into the shell when a liner exchange is not possible. So far the strength of this cement locking mechanism has been measured on only a few specimens. The purpose of this study is to correct that oversight by measuring the push-out and lever-out strengths of an acetabular polyethylene liner cemented into a porous-coated shell. We cemented acetabular liners into porous-coated acetabular shells using first-generation cementing techniques. Each of 30 specimens was tested for its push-out or lever-out strength. The results suggest that the strength of a cemented polyethylene liner locking mechanism is similar to that of an uncemented acetabular shell.