Search

Background In shoulder arthroplasty, bone resorption around the stem can lead to stem loosening and makes surgery difficult at the time of revision. Proximal bone resorption after reverse shoulder arthroplasty can cause instability because of a decrease of deltoid wrapping effect. As factors of the stem itself, such as stem coating, shape, length, and use of bone cement, may also affect bone resorption, a single-stem model should be used to compare bone resorptions between different pathologies and surgical procedures. However, to date, a few reports have compared these differences in detail using a single-stem model. Therefore, we investigated the prevalence and location of humeral bone resorption in a single-stem model. Methods The study included 100 shoulders that underwent anatomical total shoulder arthroplasty (TSA) or humeral head replacement (HHR) with a single uncemented humeral stem from 2008 to 2018. The patients were 31 men and 69 women. The mean age at surgery was 72.9 years (range, 41-86 years). The patients were divided into three groups: especially, 25, 61, and 14 shoulders received TSA for primary osteoarthritis without rotator cuff tears (TSA group), HHR using an anatomical head with rotator cuff repair for cuff tear arthropathy (CTA) (HHR group), and HHR using a CTA head without rotator cuff repair (CTA group), respectively. Patients were monitored for a mean of 56 months (range, 12-98 months). The location of bone resorption was divided into seven zones as follows: zone 1, greater tuberosity; zone 2, lateral diaphysis; zone 3, lateral diaphysis beyond the deltoid tuberosity; zone 4, tip of the stem; zone 5, medial diaphysis beyond the deltoid tuberosity; zone 6, medial diaphysis; and zone 7, calcar region. The degree of bone resorption was classified from grade 0 to 4. Results Bone resorption of grade 3 or higher was significantly more frequent at the greater tuberosity in the HHR and CTA groups (P Conclusion The state of attachment of the rotator cuff to the greater tuberosity might affect bone resorption at the greater tuberosity, such as the greater tuberosity after shoulder arthroplasty. In cases of shoulder arthroplasty for arthropathy with rotator cuff tear, performing rotator cuff repair might prevent bone resorption. Level of evidence Level IV; Prognosis Study

Metal plates have always been the gold standard in the clinic for internal fracture fixation due to their high strength advantages. However, high elastic modulus can cause stress shielding and lead to bone embrittlement. This study used an electron beam melting method to prepare personalized porous Ti6Al4V (pTi) bone plates. Then, chemical vapor deposition (CVD) technology coats tantalum (Ta) metal on the pTi bone plates. The prepared porous Ta-coated bone plate has an elastic modulus similar to cortical bone, and no stress shielding occurred. In vitro experiments showed that compared with pTi plates, Ta coating significantly enhances the attachment and proliferation of cells on the surface of the scaffold. To better evaluate the function of the Ta-coated bone plate, animal experiments were conducted using a coat tibia fracture model. Our results showed that the Ta-coated bone plate could effectively fix the fracture. Both imaging and histological analysis showed that the Ta-coated bone plate had prominent indirect binding of callus formation. Histological results showed that new bone grew at the interface and formed good osseointegration with the host bone. Therefore, this study provides an alternative to bio-functional Ta-coated bone plates with improved osseointegration and osteogenic functions for orthopaedic applications., Graphical abstract Image 1, Highlights • Porous Ta coated bone plate has a low elastic modulus, which can avoid stress shielding. • Porous Ta coated bone plate has excellent biocompatibility and can be permanently implanted in the body. • Porous Ta coated bone plate has excellent osseointegration properties and can promote fracture healing.

Magnesium (Mg) has emerged as one of the third-generation biomaterials for regeneration and support of functional bone tissue. Mg is a better choice over permanent implants such as titanium, stainless steel, cobalt-chrome as magnesium is biodegradable and does not require a second surgery for its removal after bone tissue recovery. It also reduces the risk of stress shielding as its elastic modulus is closer to human bone in comparison to permanent implants and other biodegradable metallic implants based on Iron and Zinc. Most importantly, Mg is osteoconductive thus stimulates new bone formation and possess anti-bacterial properties hence reducing the risk of failure due to infection. Despite its advantages, a major concern with pure Mg is its rapid bio-corrosion in presence of body fluids due to which the mechanical integrity of the implant deteriorates before healing of the tissue is complete. Mechanical properties of Mg-based implants can be enhanced by mechanical processing, alloying, and topology optimization. To reduce the corrosion/degradation rate, Mg has been alloyed with metals, reinforced with ceramics, and surface coatings have been applied so that the degradation rate of Mg-based implant matches with that of healing rate of bone tissue. The present review discusses the effect of alloying elements and reinforcing ceramics on microstructure, mechanical, and corrosion properties of Mg-based orthopedic implants. In addition, the biocompatibility of Mg-based alloys, composites, and coatings applied on Mg implants has been highlighted. Further, different methods of fabricating porous implants have been highlighted as making the implant porous facilitates the growth of new bone tissue through the pores.

An attempt has been made in this study by employing the Deshpande and Fleck constitutive model, which is available in the ABAQUS software as the crushable foam material model, to reflect the stress-strain behavior of dental implants made of titanium foam (Ti-foam) under fatigue loading. For comparison purposes, solid Ti has also been considered in the study. Before proceeding to the study of fatigue loading effect on the implant, the modelling approach has been tested with the results of a compression test available in the open literature. Equivalent plastic strain, effective stress, and hydrostatic stress qualities have been generated for various porosity levels. Fatigue loadings corresponding to all three directions namely, lingual, axial, and mesio-distal directions have been applied on the implant for 50 load cycles in order to observe the fatigue loading effect on the implant. It has been observed from the simulation results that under identical conditions, stress generated in the Ti-foam material is less and Ti-foam can also transfer more loads to the surrounding bones as compared to the correspondings of solid Ti material. Therefore, Ti-foam based implant can solve the stress shielding effect and hence Ti-foam is a suitable alternative of the solid Ti for fabricating dental implants.

Background Finite element analysis has suggested that stemless implants may theoretically decrease stress shielding. The purpose of this study was to assess the radiographic proximal humeral bone adaptations seen following stemless anatomic total shoulder arthroplasty. Methods A retrospective review of 152 prospectively followed stemless total shoulder arthroplasty utilizing a single implant design was performed. Anteroposterior and lateral radiographs were reviewed at standard time points. Stress shielding was graded as mild, moderate, and severe. The effect of stress shielding on clinical and functional outcomes was assessed. Also, the influence of subscapularis management on the occurrence of stress shielding was determined. Results At 2 years postoperatively, stress shielding was noted in 61 (41%) shoulders. A total of 11 (7%) shoulders demonstrated severe stress shielding with 6 occurring along the medial calcar. There was one instance of greater tuberosity resorption. At the final follow-up, no humeral implants were radiographically loose or migrated. There was no statistically significant difference in clinical and functional outcomes between shoulders with and without stress shielding. Patients undergoing a lesser tuberosity osteotomy had lower rates of stress shielding, which was statistically significant ( p = 0.021) Discussion Stress shielding does occur at higher rates than anticipated following stemless total shoulder arthroplasty, but was not associated with implant migration or failure at 2 years follow-up. Level of evidence IV, Case series.

Femur bone fracture is mainly caused by sports injuries or accidents and has become serious attention in orthopedic trauma. The unique cortical bone microstructures and features contribute to complex fracture behavior. This paper presents the investigation of Type 2 and Type 3 arch-shaped microcrack penetration based on von Mises stress and stress intensity factor (SIF) parameters around the microcrack tips penetration in Haversian system cortical bones. The fracture model was constructed based on bone continuum mechanics theory named Kachanov theory of elastic interaction. It aims to determine the level of stress amplification and stress shielding for the transition of Type 2 to Type 3 for heterogeneous cortical bone fracture model. A total of eight microcrack extension points (CP1–8) were constructed based on 1-mm2 Haversian system model, subjected to the force of 10 N in Mode I and Mode II loading. Finite element (FE) analysis was then performed to evaluate the von Mises stress around the crack end tips and SIF under the assumption of bone damage, $$D$$ < 1. The study found that the greatest von Mises stress value was observed at the CP4 (175.766 MPa) and CP8 (213.264 MPa) for Mode I loading and CP4 (106.037 MPa) for Mode II loading. In terms of fracture parameter, the critical SIF magnitude was peaked at CP4 (1272.8 MPa*m1/2) and CP8 (1369.0 MPa*m1/2) for Mode I loading and CP5 (402.29 MPa*m1/2) for Mode II loading. The results show that the transition of Type 2 (straight crack) to Type 3 (arch crack) microcrack penetration in Haversian system experienced the multilevel of stress amplification (CP1–CP4, CP6–8) and stress shielding (CP4–CP6) to represent the bone micro-damage level.

The term stress-shielding is frequently used to mention the reduction in mechanical stimulus in the surrounding bone due to the presence of a biomaterial inert implant whose mechanical properties are superior to bone. As the natural consequence of this, mineral loss occurs in the bone over time and creating subsequent weakness. One of the methods to reduce stress-shielding problem is to develop hip-stem implant designs that will transfer the load more to the bone. Therefore, in this study, multi-lattice designs were developed to reduce the stress-shielding effect in hip implant applications. For this, the proximal part of the hip implant stems has been divided into three parts. Simple cubic, body centered cubic, and face centered cubic lattice structures were created on the upper parts. Inner vertical and inner vertical + inner horizontal beams were added to the lattice structure of the upper part for middle and lower parts, respectively. Due to the multi-lattice designs, the maximum von Mises stress values on the hip implant stem were reduced from 289 to 189 MPa, as well as a weight reduction of up to 25.89%. Stress-shielding signals were obtained by determining the change in strain energy per unit bone mass caused by the presence of the femoral hip implant stem and its ratio to intact bone. In the case of using hip-stems having multi-lattice designs, there is a significant increase (max. 150.47%) in stress-shielding signals from different zones of the femur.

Background Endoprosthetic reconstruction after oncologic resection of bone tumors requires stable fixation between the prosthesis and residual host bone. Compressive osseointegration has been developed as an alternative to traditional stemmed implants to address the challenges and complications of achieving this fixation. Sufficient time has now passed from the advent of compressive implants to allow for an assessment of the intermediate-term and long-term results of this form of fixation. Questions/purposes At a minimum follow-up of 10 years after implantation of a compressive osseointegration device for oncologic reconstruction: (1) What is the risk of periprosthetic fracture, aseptic loosening, or implant breakage resulting in revision surgery for endoprosthesis removal? (2) What is the long-term cortical response at the host-endoprosthesis interface as visualized on plain radiographs? Methods A single-center, retrospective study was performed between 2002 and 2010, in which 110 patients with primary bone sarcoma of the proximal or distal femur were considered for oncologic resection and reconstruction. Patients were considered for a compressive osseointegration endoprosthesis if they were 50 years of age or younger, had not previously received femoral radiation, had no metabolic disease impairing bone healing, were not diagnosed with metastatic disease, and had life expectancy greater than six months. Of the 110 patients, 25 were treated with a compressive osseointegration implant of the proximal or distal femur, and 85 patients were treated with conventional stemmed implants or amputation because of older age, advanced disease, metabolic comorbidities, inability to tolerate a nonweightbearing postoperative period, or in the case of rotationplasty, patient preference. All patients who received this device during the period of study were considered eligible for inclusion in this review. The median (range) age was 18 years (7 to 50), and 13 of 25 patients were men. Five patients died of disease before the minimum follow-up duration of 10 years; two underwent amputation due to local recurrence and three died with the implant in situ, leaving 20 patients for complete analysis. Median follow-up was 144 months, and all 20 surviving patients had a minimum follow-up of 10 years (121 to 230 months). The primary endpoint was reoperation and implant removal for periprosthetic fracture, aseptic loosening, or mechanical breakage of any component of the compressive device in the endoprosthesis. In final analysis, death was considered a competing event to revision surgery, and cumulative incidence was reported after competing-event analysis. A secondary aim was radiographic evaluation of the host-implant interface to assess the long-term cortical response to compressive osseointegration. Results Spindle fracture or loosening was noted in three patients, and the remaining 17 patients maintained the compression device until the final follow-up. The risk of reoperation for aseptic loosening, periprosthetic fracture, or mechanical breakage of the implant using a competing risks estimator was 12% at 10 years (95% CI 0% to 26%). These complications occurred within 29 months of the index surgery; no patients had implant loosening or mechanical breakdown after this initial period. On radiographic assessment, 14 patients demonstrated cortical hypertrophy of the bone-implant interface, six patients had maintenance of the native cortical contour, and no patients had cortical atrophy or narrowing at the implant interface.Conclusion Long-term follow-up in patients with compressive osseointegrative endoprosthetic devices demonstrated no late revisions because of periprosthetic fracture, aseptic loosening, or implant breakage in this cohort with a minimum 10-year follow-up. There was no evidence of late-onset cortical atrophy or stress shielding at the host-implant interface. This study supports the long-term stability of the interface between host bone and the endoprosthesis in compressive osseointegration devices. Level of evidence Level IV, therapeutic study.

Short stems have constantly gained popularity in primary total hip arthroplasty (THA) over the last decade. Although cementless short stems are not primarily designed to be used as revision implants, there may be certain indications for which downsizing the femoral component in failed conventional THA is potentially advantageous.In this single center retrospective case series, six patients who underwent revision using a calcar-guided short stem after failed THA are presented. The mean follow-up was 3.32 years (SD 0.63 years). The health status was evaluated by the EQ-5D-5L score. Patient reported outcome measurements (PROM) were recorded using the Harris hip score (HHS) and The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Pain and satisfaction were assessed using a visual analogue scale (VAS). Radiographic analysis was performed by evaluating osteolysis, stress shielding, alignment and signs of aseptic loosening. Complications were documented.At last follow-up the mean EQ-5D-5L index was 0.851 (SD 0.098). Clinical outcome was excellent (HHS ≥ 90) in 4 patients and moderate (HHS 71 and 79) in 2 patients. The mean WOMAC score was 9.20% (SD 12.61%). Pain and satisfaction on VAS were 1.00 (SD 1.15) and 9.17 (SD 0.37), respectively. No major complications occurred. To date, no further revision surgery was needed. Radiologically, no signs of subsidence, aseptic loosening, stress shielding and fractures were obvious.The present case series indicates that in failed conventional THA downsizing may be considered a treatment option, using short stem THA in selected cases.HINTERGRUND: Kurzschäfte haben in der primären Hüfttotalendoprothetik (Hüft-TEP) im letzten Jahrzehnt stetig an Popularität gewonnen. Obwohl zementfreie Kurzschäfte nicht primär für den Einsatz als Revisionsimplantate konzipiert sind, stellt das „Downsizing“ der Femurkomponente bei fehlgeschlagener konventioneller Hüft-TEP bei ausgewählten Indikationen potenziell eine Behandlungsalternative dar.In dieser retrospektiven Fallserie werden 6 Patienten vorgestellt, die nach einer fehlgeschlagenen Hüft-TEP unter Nutzung eines kalkargeführten Kurzschafts revidiert wurden. Die mittlere Nachbeobachtungszeit betrug 3,32 Jahre (SD 0,63). Der Gesundheitszustand wurde mit dem EQ-5D-5L-Score bewertet. Die von den Patienten berichteten Ergebnisse (PROMs) wurden mit dem Harris Hip Score (HHS) und dem Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) erfasst. Schmerz und Zufriedenheit wurden mit Hilfe der visuellen Analogskala (VAS) erfasst. Die radiologische Analyse erfolgte durch die Bewertung hinsichtlich, Sinterung, Osteolysen, „stress shielding“ und Anzeichen von aseptischer Lockerung. Komplikationen wurden dokumentiert.Beim letzten Follow-up betrug der mittlere EQ-5D-5L-Index 0,851 (SD 0,098). Die klinischen Ergebnisse waren bei 4 Patienten ausgezeichnet (HHS ≥ 90) und bei 2 Patienten befriedigend (HHS 71 und 79). Der mittlere WOMAC-Score betrug 9,20 % (SD 12,61). Schmerz und Zufriedenheit auf der VAS lagen bei 1,00 (SD 1,15) bzw. 9,17 (SD 0,37). Es traten keine größeren Komplikationen auf. Bis heute war keine weitere Revisionsoperation erforderlich. Radiologisch zeigten sich keine Anzeichen von Sinterung, aseptischen Lockerungen, „stress shielding“ und Frakturen.Die vorliegende Fallserie legt nahe, dass bei fehlgeschlagener konventioneller Hüft-TEP das „Downsizing“ als Behandlungsoption in ausgewählten Fällen in Betracht gezogen werden kann.

During total hip replacement (THR), prosthesis material is stiffer than the bone tissue, decreasing load transmission to the host tissue around the prosthesis. After a THR, the aim is to achieve stress distribution along the femur close to normal physiological stress distribution for all loads transferred across the hip joint. In this study, we analyzed the advantages of using a collared stem over collarless one with the finite element method (FEM), strain gauges (SGs), and the digital image correlation (DIC) system. In the biomechanical tests, we implanted composite femurs and loaded them with the stance configuration in a universal testing machine (Instron). We compared the predicted strains with the strains recorded experimentally in the same regions of the femur. The results revealed that for collarless stems, a high level of stress concentration is observed in the distal region of the implant but not in the proximal region. The collared case presents a strain distribution closer to that of a healthy bone proximal zone that was almost two times better than in case of the collarless stem, whereas stresses in the distal part of the femur corresponded to a healthy state. Finally, the numerical results for the bone adaptation around the implant provided clear evidence that the collar design strongly influences the proximal resorption because of better load transmission. According to both the numerical and experimental results, a collar that connects to the bone cut may decrease the proximal stress shielding effect and distal cortical hypertrophy.

A three dimensional finite element (FE) model of a novel carbon fibre polyamide 12 composite hip stem was used to compare with two commerically available (Exeter and Omnifit) hip stems to minimize stress shielding and bone resorption. A virtual axial load of 3000N was applied to the FE model which replicated the experimental study. Strain and stress distributions were computed and compared with experimental results. Experimentally, three hip stems had their distal portions rigidly mounted and had strain gauges placed along the surface at 3 medial and 3 lateral locations. From the FE analysis, the von mises stress range for the composite hip stem was 200% and 45% lower than that in the Omnifit and Exeter implants, respectively. The aggregate average difference between FE and experimental microstrains for four proximal strain gauge locations were 7.5% (composite), 11.5% (Exeter), 14.6% (Omnifit), and the composite hip stem's stiffness (1982N/mm) was lower than the metallic hip stem stiffnesses (Exter, 2460N/mm; Omnifit, 2543 N/mm). This study showed considerable improvement in stress transfer to bone tissue.

INTRODUCTION Short stems seem to be a good alternative for young patients as they offer promising results, rapid recovery and preservation of metaphyseal bone stock. This is one of the few studies in the literature to report medium-term clinical-radiological results for short hip stems. MATERIALS AND METHODS This prospective study evaluated 68 short femoral stems in 63 patients treated with total hip replacement. Clinical, functional and quality-of-life outcomes were measured at 6 and 12 months, and annually thereafter until the end of follow-up. The radiological analysis included measurements of potential leg length discrepancies, stem alignment and signs compatible with stress shielding. RESULTS Fifty-four males (59 hips) and nine females (9 hips) of an average age of 44.3 years (range, 25-68) were studied. The most common diagnosis was osteoarthritis (51.5%). Mean overall follow-up was 7.8 years (range, 5.8-9.8). The overall survival rate was 97.1% (95% CI 88.7-99.7%). Surgery resulted in an increase of 42.3 ± 1.1 points in the modified Harris Hip Score and 21.9 ± 0.6 points in the Oxford Hip Score (p

Despite the prevalence of low back pain (LBP) in society, the pathomechanism of LBP continues to elude researchers. LBP patients have demonstrated morphological and material property changes to their lumbar soft tissues, potentially leading to irregular load sharing within the lumbar spine. This study aims to analyze potential stress shielding consequential of augmented soft tissue properties via the comparison of a healthy and LBP finite element models. The models developed in this study include the vertebrae, intervertebral discs and soft tissues from L1-S1. Soft tissue morphology and material properties for the LBP model were augmented to reflect documented clinical findings. Model validation preceded testing and was confirmed through comparison to the available literature. Relative to the healthy model, the LBP model demonstrated an increase in stress by 15.6%, with 99.8% of this stress increase being distributed towards the thoracolumbar fascia. The majority of stress skewed towards the fascia may indicate a potential stress allocation bias whereby the lumbar muscles are unable to receive regular loading, leading to stress shielding. This load allocation bias and subsequent stress shielding may potentially contribute to the progression and pathomechanism of LBP but prospective studies would be required to make that link.

Introduction Recent innovations in reverse shoulder arthroplasty (RSA) have presented 2 distinct humeral stem designs: an onlay system that rests above the anatomic neck and an inlay component that rests within the metaphysis. The purpose of this study is to compare clinical and radiographic outcomes between inlay and onlay-designed humeral stems in lateral center of rotation RSA implant systems. Methods A retrospective cohort study was performed on primary RSA patients treated by 2 surgeons at 2 separate hospitals with a minimum 2-year follow-up. Patients were categorized based on treatment with an onlay or inlay humeral design and matched 1:1 by indication and age. Patient-reported outcome measures (PROMs), including the Simple Shoulder Test, American Shoulder and Elbow Surgeons, and Visual Analog Score for pain, as well as active motion (forward elevation, internal rotation) were recorded at pre- and postoperative intervals. An Inlay-Onlay index assessed the degree of inset or offset of each particular implant referencing the anatomic neck. Radiographic analysis focused on scapular notching, bone resorption around the humeral stem, and acromion stress fractures. Results A total of 92 patients participated in the 1:1 matched analysis (46 each group). Cohorts were similar in age, gender, indication, follow-up length, and preoperative PROMs, with the exception of Simple Shoulder Test. At the most recent follow-up, there were no differences in all PROMs between groups. There were no differences in active internal rotation, but patients with an onlay-configuration demonstrated greater external rotation (P Conclusion There were no differences in clinical outcomes or incidence of acromial fractures following RSA with an onlay- or inlay-style humeral stem prosthesis. Bone resorption of the proximal humerus occurred more frequently in patients with an onlay prosthesis, suggesting that an inlay prosthesis may afford better prevention of humeral stress shielding. Level Of Evidence Level III; Retrospective Comparative Study

Short-stem prostheses in hip arthroplasty have emerged as an alternative to conventional stems, especially in younger patients. The purpose of this study was to compare functional and radiological results of a short metaphyseal fitting cementless stem versus a conventional stem implant, in patients younger than 60 years. All patients operated from January 2006 to April 2013 were included, obtaining a minimum follow-up of 7 years. Harris Hip Score (HHS) and SF-36 (quality of life) questionnaires were applied and the presence of “thigh pain” was specifically assessed. We also compared complication rate, revision rate and average prosthesis survival. Femoral stress shielding (Gruen scale), stem subsidence, varus-valgus tilt and implant stability (Engh scale) were also compared. A total of 101 short-stem and 74 conventional arthroplasties were included, with an average follow-up of 9.82 (7–14) years. HHS functional score and SF-36 were excellent in both implants and no significant difference between them (p > 0.05) was found. However, “thigh pain” was present in 7 patients with conventional stems and none with short-stems (p

With the development of economy and the progress of medical science and technology, artificial prosthesis replacement has become an important means to improve the dysfunction caused by human bone diseases. However, there are still some loose phenomena caused by stress shielding. To solve the complications of aseptic loosening after calcaneal prosthesis replacement, an optimal design method for the prosthesis was proposed. The prosthesis was designed and optimized according to the real bone shape and the replacement requirements by the combination of computed tomography (CT) technology, computer-aided design, finite element analysis, and power flow theory. CT data were imported into MIMICS and Geomagic Studios. UG was used to obtain the geometric model of the human skeleton. Then, the 3D finite element model of the prosthesis was established by combining the finite element software Abaqus, and a series of finite element analysis was carried out. The prosthesis was topologically optimized and filled with a porous structure. The prosthesis was implanted by computer simulation. Finally, the power flow method was used to compare the dynamic performance and energy transfer before and after the prosthesis replacement to verify the rationality of the prosthesis design. In this paper, this method was used to optimize the design of the calcaneal prosthesis, and the research shows that this method can reduce the stress shielding effect of the calcaneal prosthesis. From the case of calcaneal prosthesis optimization, this method is not only a supplement to the contemporary biomechanical theory but also can guide the design of bone prosthesis in bone prosthesis replacement surgery.

Objective To investigate whether the periprosthetic bone environment could be affected by activity during the early rehabilitation period after primary total hip arthroplasty (THA) and to evaluate the safety and efficacy of activity during the early rehabilitation period. Methods This random clinical trial was conducted from January 2017 to July 2017. A total of 22 selected patients with advanced osteonecrosis of the femoral head (ONFH) who underwent primary unilateral THA were randomized (1:1) to a high activity level group (HA group) or a low activity level group (LA group). The HA group included nine men and two women, aged 53.18 ± 13.29 years. The LA group included five men and six women, aged 55.73 ± 11.73 years. The intervention was different postoperative daily walking distances guided by researchers: 1727.27 ± 564.08 m 0–2 months and 4272.73 ± 904.53 m 3–6 months postoperation for the HA group and 909.09 ± 583.87 m 0–2 months and 2409.09 ± 1068.13 m 3–6 months postoperation for LA group. The primary outcomes were radiographic evaluation (prosthetic stability and stress shielding based on the Engh scale) and bone mineral density (BMD) with a femoral prosthesis (individual and intergroup comparison using seven Gruen zones) at 6 months postoperatively. Secondary outcomes were set to confirm the safety and efficacy of activity during early rehabilitation, including day 1 erythrocyte sedimentation rate (ESR), day 1 hypersensitive C‐reactive protein (CRP), length of hospital stay (LOS), and the Harris hip score (HHS) at discharge, 2 months postoperatively, and 6 months postoperatively. Results Patients were followed up for 6 months after surgery. Regarding primary outcomes, all prostheses were assessed as stable, with bone in‐growth. There were no adverse events in any cases. The HA group had a higher incidence of stress shielding than the LA group, but there was no statistical significance (63.64% vs 18.18%; P > 0.05). The degree of stress shielding had a different distribution for the two groups (P 0.05). The HHS on day of discharge was higher in the HA group than in the LA group (60.73 ± 5.37 points vs 51.18 ± 8.05 points, P 0.05) and 6 months (90.45 ± 5.24 points vs 91.55 ± 4.03 points, P > 0.05). Conclusion High activity levels during early rehabilitation after primary THA accelerate the process of bone remodeling and aggravate stress shielding, with no significant benefits for functional recovery., X‐rays of three patients with osteonecrosis of the femoral head (ONFH). Femoral collapse and acetabular arthritis were evident in preoperative X‐rays (A1, B1, and C1). Stress shielding levels of 0, 1, and 2 were apparent on X‐rays 6 months postoperatively (A2, B2, and C2).

Implants, including artificial joints, bone fixation devices, and other orthopedic implants, oral implants, and vascular interventional devices, are used to repair or replace human tissues or organs and restore their functions. Since biodegradable implants have advantage of avoiding long-term complications (including bone stress shielding, restenosis, thrombosis, and secondary surgery) while remaining safe and productive, personalized biodegradable implants will be an irresistible trend in the clinic for implantable and interventional medical devices. However, innovation of personalized biodegradable implants faces several challenges, including the interaction between the implant and its surrounding tissues or cells, the coordination of structural strength of implants and its degradation, the topological microstructure of implant and its fatigue properties, reliability, and safety. In this review, we introduced critical progresses achieved in the fields related to implants, including mechanical properties of materials, interaction between implants and host tissue, effect of stress on degradation; furthermore, we highlighted the optimized design and manufacture of implants as well as the evaluation of their reliability.

Three-dimensional (3D)-printed titanium cups used in primary total hip arthroplasty (THA) were developed to combine the benefits of a low elastic modulus with a highly porous surface. The aim was to improve local vascularization and bony ingrowth, and at the same time to reduce periprosthetic stress shielding. Additive manufacturing, starting with a titanium alloy powder, allows serial production of devices with large interconnected pores (trabecular titanium), overcoming the drawbacks of tantalum and conventional manufacturing techniques. To date, 3D-printed cups have achieved dependable clinical and radiological outcomes with results not inferior to conventional sockets and with good rates of osseointegration. No mechanical failures and no abnormal ion release and biocompatibility warnings have been reported. In this review, we focused on the manufacturing technique, cup features, clinical outcomes, open questions and future developments of off-the-shelf 3D-printed titanium shells in THA.

Study Design: This retrospective case series enrolled 13 patients who underwent posterior fixation with both transdiscal screws for diffuse idiopathic skeletal hyperostosis (TSDs) and pedicle screws (PSs) to treat spinal injury accompanied by diffuse idiopathic skeletal hyperostosis (DISH). Purpose: To describe the usefulness, feasibility, and biomechanics of TSD. Overview of Literature: Vertebral bodies accompanied by DISH generally have lower bone mineral density than normal vertebral bodies because of the stress shielding effect. This phenomenon tends to makes screw fixation challenging. To our knowledge, solutions for this issue have not previously been reported. Methods: Patients were assessed using the data on surgical time, estimated intraoperative blood loss, mean number of stabilized intervertebral segments, number of screws used, perioperative complications, union rate, and the three-level EuroQol five-dimensional questionnaire (EQ5D-3L) score at the final follow-up. The Hounsfield unit (HU) values of the screw trajectory area, and the actual intraoperative screw insertion torque of TSDs and PSs were also analyzed and compared. Results: The surgical time and estimated intraoperative blood loss were 165.9±45.5 minutes and 71.0±53.4 mL, respectively. The mean number of stabilized intervertebral segments was 4.6±1.0. The number of screws used was 4.9±1.3 for TSDs and 3.0±1.4 for PSs. One death occurred after surgery. The union rate and EQ5D-3L scores were 100% and 0.608±0.128, respectively. The HU value and actual intraoperative screw insertion torque of TSDs were significantly better than those of PSs (p

Contains fulltext : 250067.pdf (Publisher’s version ) (Open Access) Currently, steel implants are used for osteosynthesis of (comminuted) fractures and intra-articular bone defects. These osteosyntheses can sometimes be complicated procedures and can have several drawbacks including stress shielding of the bone. A bone glue might be a safe and effective alternative to current materials. Despite numerous animal studies on bone adhesives, no such material is clinically applied yet. We have conducted a systematic review to summarize the evidence in experimental animal models used in research on bone adhesive materials for trauma and orthopedic surgery. Additionally, we analysed the efficacy of the different bone adhesives for different experimental designs. A heterogeneity in experimental parameters including animal species, defect types, and control measurements resulted in a wide variety in experimental models. In addition, no standard outcome measurements could be identified. Meta-analysis on bone regeneration between adhesive treatment and nonadhesive treatment showed a high heterogeneity and no statistically significant overall effect (M: -0.71, 95% confidence interval [CI]: -1.63-0.21, p = 0.13). Besides, currently there is not enough evidence to draw conclusions based on the effectiveness of the individual types of adhesives or experimental models. A positive statistically significant effect was found for the adhesive treatment in comparison with conventional osteosynthesis materials (M: 2.49, 95% CI: 1.20-3.79, p = 0.0002). To enhance progression in bone adhesive research and provide valuable evidence for clinical application, more standard experimental parameters and a higher reporting quality in animal studies are needed. Statement of Clinical Significance: Current materials restoring anatomical alignments of bones have several drawbacks. A (biodegradable) adhesive for fixating bone defects can be a treatment breakthrough. Although numerous bone adhesives have been researched, most seemed to fail at the preclinical stage. An overview in this field is missing. This systematic review highlights the relevant parameters for design of experimental bone adhesive studies. It demonstrates evidence regarding benefit of bone adhesives but also that the quality of reporting and the risk of bias in studies need to be improved. The results will aid in designing better quality animal studies for bone adhesive research with higher translational value.

Background There is great design variability on short femoral stems available on the market. This study aims to evaluate the short-term clinical and radiological results of two different design short femoral stems, both classified as shortened tapered stems. Methods From March 2016 to March 2018, a prospective, randomized, parallel-group design study was conducted to compare functional and radiological outcomes of 45 patients underwent THA using the Tri-Lock Bone Preservation Stem and 45 patients underwent THA with the Minima S stem at a minimum 2 years of follow-up. Patients were assessed clinically and radiographically prior to surgery as well as at 3, 6, 12, and 24 months postoperatively. Primary outcomes were the change in health-related quality of life assessed with Western Ontario and McMaster Universities Osteoarthritis Index and 36-Item Short Form Health Survey and also the incidence of all hip-related complications. Secondary aims included hip function evaluated with the Harris hip score, rates of patient satisfaction, and the outcomes of a detailed radiological analysis. Results There were no significant differences between the 2 study groups in terms of patient-reported outcomes measurements, satisfaction scores, and complication rates at any of the measurement times. In both groups, stable fixation and radiographic osseointegration were achieved. However, analysis of the calcar region showed that 57.8% and 28.9% of patients had grade 1 or 2 stress shielding, in Tri-Lock and Minima S implantation group, respectively (p=0.015). Regarding coronal alignment, stems were placed in slight varus, valgus, and neutral position in 51.1%, 13.3%, and 35.6% of patients, respectively, in Tri-Lock BPS group. The Minima S stem was implanted at slight varus and valgus in 60% and 40% of patients, respectively, and neither stem in the exact neutral position. Conclusions Both different design short femoral stems demonstrated excellent clinical performance at short-term follow up. Nevertheless, concerns were raised regarding the incidence of stress shielding phenomenon and mild discrepancies in coronal stem alignment during implantation. The clinical impact of these observations should be further evaluated through larger cohorts and longer follow-up. Trial registration ISRCTN registry, ISRCTN10096716. Registered on May 8, 2018—Retrospectively registered

Background Reverse shoulder arthroplasty (RSA) has seen a recent transition from cemented to press-fit humeral stems. Several press-fit designs have focused on proximal fixation, yet there remains a paucity of data on their performance. The purpose of this study is to report early radiographic and clinical results of a third-generation RSA system, featuring metaphyseal porous metal fixation. Methods A retrospective review was performed on primary RSA patients treated with a single third-generation standard-length implant system incorporating proximal osteointegration features with a minimum 2-year follow-up. Patient-reported outcome measures, including the Simple Shoulder Test, American Shoulder and Elbow Surgeons, Visual Analog Scale for pain, and Single Assessment Numeric Evaluation, as well as measured active motion (forward elevation, external, and internal rotation) were recorded at pre- and postoperative intervals. Immediate postoperative radiographs were used to measure filling ratios at the epiphyseal, metaphyseal, and diaphyseal levels. Most recent radiographs were also reviewed for bone adaptations, acromial fractures, scapular notching, and humeral loosening. Results There were 90 patients included in the study, with an average age of 73 years (± 7.23) and clinical follow-up of 32 months (± 7.25). Indications included osteoarthritis with a rotator cuff tear (51%), osteoarthritis without a cuff tear (40%), fracture sequelae (2%), and locked anterior dislocation (2%). There were significant improvements in all measured motions and patient-reported outcome measures at the most recent follow-up, with good to excellent satisfaction in 91.1% of patients. High mean epiphyseal (0.90 ± 0.06) and metaphyseal (0.83 ± 0.07) filling ratios together with low mean diaphyseal filling ratio (0.48 ± 0.07) represented proximal fixation. There were 6 cases with scapular notching, 5 postoperative acromial fractures, and 2 with temporary postoperative neuropathy. Proximal bone resorption was seen in 18.9% of cases, and there were no cases of humeral loosening, baseplate failure, or need for revision. Conclusion Primary RSA with a third-generation press-fit humeral component with metaphyseal fixation provides excellent early outcomes with no loosening and low rates of proximal stress-shielding. Results of this study support the use of an inlay humeral component with osteointegration features that facilitate proximal stem fixation. Level of Evidence Treatment Study

The fully porous long stem could be used for diaphyseal locking and achieve bypass fixation in revision total hip arthroplasty (THA). This study evaluated long-term results for fully porous long stems made of titanium alloy in revision THA. Between 2003 and 2010, 45 consecutive femoral revisions were performed using fully porous long stems. Thirty-eight hips had complete clinical and radiographic data for a mean of 13.8 years (range, 10–16.7 years). Femoral bone loss was Paprosky type II in 14 hips, type IIIA in 18 hips, and type IIIB in six hips. Clinical results were analyzed using the Merle d’Aubigne and Postel scoring system. Femoral stress shielding was graded. Radiological loosening of the femoral component was evaluated. Kaplan-Meier survival analysis was performed with revision for any reason as the end-point. Mean Merle d’Aubigne and Postel score improved significantly from 10.7 before revision to 14.5 at latest follow-up (p < 0.001). Third-degree stress shielding was found in seven hips, and fourth degree in 11 hips. Radiological femoral loosening occurred in one hip, which was revised. Another hip was revised for stem fracture. Kaplan-Meier cumulative survival rate was 94.7% at both ten and 15 years. Although stress shielding is a concern with fully porous stems, this stem was useful in revision THA and provided satisfactory long-term results in hips with Paprosky types II, IIIA, and IIIB.

Instrumentation during metastatic spine tumor surgery (MSTS) provides stability to the spinal column in patients with pathologic fracture or iatrogenic instability produced while undergoing extensive decompression. Titanium is the current implant material of choice in MSTS. However, it hinders radiotherapy planning and generates artifacts, with magnetic resonance imaging and computed tomography scans used for postoperative evaluation of tumor recurrence and/or complications. The high modulus of elasticity of titanium (110 GPa) results in stress shielding, which may lead to construct failure at the bone-implant interface. Polyether ether ketone (PEEK), a thermoplastic polymer, is an emerging alternative to titanium for use in MSTS. The modulus of elasticity of PEEK (3.6 GPa) is close to that of cortical bone (17-21 GPa), resulting in minimal stress shielding. Its radiolucent and nonmetallic properties cause minimal interference with magnetic resonance imaging and computed tomography scans. PEEK also causes low-dose perturbation for radiotherapy planning. However, PEEK has reduced bioactivity with bone and lacks sufficient rigidity to be used as rods in MSTS. The reduced bioactivity of PEEK may be addressed by 1) surface modification (introducing porosity or bioactive coating with hydroxyapatite [HA] or titanium) and 2) forming composites with HA/titanium. The mechanical properties of PEEK may be improved by forming composites with HA or carbon fiber. Despite these modifications, all PEEK and PEEK-based implants are difficult to handle and contour intraoperatively. Our review provides a comprehensive overview of PEEK and modified PEEK implants, with a description of their properties and limitations, potentially serving as a basis for their future development and use in MSTS.

Background In current clinical practice, the most commonly used fusion cage materials are titanium (Ti) alloys. However, titanium alloys are non-degradable and may cause stress shielding. ZK60 is a bio-absorbable implant that can effectively avoid long-term complications, such as stress shielding effects, implant displacement, and foreign body reactions. In this study, we aimed at investigating the biomechanical behavior of the cervical spine after implanting different interbody fusion cages. Methods The finite element (FE) models of anterior cervical disc removal and bone graft fusion (ACDF) with a ZK60 cage and a Ti cage were constructed, respectively. Simulations were performed to evaluate their properties of flexion, extension, lateral bending, and axial rotation of the cervical spine. Moreover, a side-by-side comparison was conducted on the range of motion (ROM), the deformation of cages, the stress in the cages, bone grafts, and cage-end plate interface. Simultaneously, according to the biomechanical analysis results, the microporous structure of the ZK60 cage was improved by the lattice topology optimization technology and validation using static structure. Results The ROMs in the current study were comparable with the results reported in the literature. There was no significant difference in the deformation of the two cages under various conditions. Moreover, the maximum stress occurred at the rear of the cage in all cases. The cage’s and endplate-cage interface’s stress of the ZK60 group was reduced compared with the Ti cage, while the bone graft stress in the ZK60 fusion cage was significantly greater than that in the Ti fusion cage (average 27.70%). We further optimized the cage by filling it with lattice structures, the volume was decreased by 40%, and validation showed more significant biomechanical properties than ZK60 and Ti cages. Conclusion The application of the ZK60 cage can significantly increase the stress stimulation to the bone graft by reducing the stress shielding effect between the two instrumented bodies. We also observed that the stress of the endplate-cage interface decreased as the reduction of the cage’s stiffness, indicating that subsidence is less likely to occur in the cage with lower stiffness. Moreover, we successfully designed a porous cage based on the biomechanical load by lattice optimization.

AIMS: Metaphyseal cones and sleeves are components used in revision knee arthroplasty to ensure load transfer, encourage bone on-growth and prevent stress shielding. Additive manufacturing of titanium alloy implants is a novel technique with limited clinical outcome reports in the literature. The aim of this study was to determine radiographic evidence of osseointegration and early results of a single manufacturer porous titanium metaphyseal components in the proximal tibia. METHODS: We retrospectively reviewed the prospectively collected database of two institutions. Patients who underwent revision knee arthroplasty using porous titanium components by a single manufacturer were identified. Immediate post-operative and latest follow-up radiographs were independently analysed by 2 reviewers to determine metaphyseal bone contact and level of osseointegration in relevant Knee Society Radiographic Evaluation and Scoring System zones. RESULTS: 22 patients (15 males; 7 females) with a mean age of 71 (49–92) years were included. The mean follow-up period was 14 months (2–44 months). Cones were used in 16 patients and sleeves in 6. Interobserver reliability assessment showed substantial agreement (weighted Kappa 0.71, (95% CI: 0.60, 0.81). There was significant correlation between the bone contact in the immediate postop radiograph and osseointegration at final follow-up (kendall’s tau-b: 0.698, p

To assess the clinical and radiological results of a metaphyseal reverse total shoulder arthroplasty (rTSA) without diaphyseal stem, in rheumatoid arthritis (RA) patients. Forty-five shoulders in 36 consecutive RA patients (2005–2015) underwent rTSA with a bone impaction technique. Patients were assessed clinically and radiographically preoperatively, at 3 weeks, 3 months, 6 months, 12 months post-operatively, and yearly thereafter, using constant score (CS), pain score, subjective shoulder value (SSV) and patient satisfaction score. Forty-four shoulders with mean follow-up of 67 months (range 24 m-146 m (12y)) were available for follow-up. Mean age at surgery was 68.7 years (range 39–86). CS improved from 17.5 ± 10.5(SD) (age/sex adjusted 23.9 ± 14.5(SD)) preoperatively to 60.9 ± 17.4 (SD) (age/sex adjusted 86.5 ± 24.5 (SD)) at last follow-up (P

As a larger elderly human population is expected worldwide in the next 30 years, the occurrence of aging-associated illnesses will also be increased. The use of prosthetic devices by this population is currently important and will be even more dramatic in the near future. Hence, the design of prosthetic devices able to reduce some of the problems associated with the use of current components, such as stress shielding, reduced mobility, infection, discomfort, etc., becomes relevant. The use of additive manufacturing (AM) and the design fabrication of self-supported cellular structures in the biomedical area have opened up important opportunities for controlling the physical and mechanical properties of hip implants, resulting in specific benefits for the patients. Different studies have reported the development of hip prosthetic designs employing AM, although there are still opportunities for improvement when it comes to customized design and tuning of the physical and mechanical properties of such implants. This work shows the design and manufacture by AM of a personalized stainless-steel partial hip implant using tomography data and self-supported triply periodic minimal surface (TPMS) cell structures; the design considers dimensional criteria established by international standards. By employing tomography data, the external dimensions of the implant were established and the bone density of a specific patient was calculated; the density and mechanical properties in compression of the implant were modulated by employing an internal gyroid-type cell structure. Using such a cell structure, the patient's bone density was emulated; also, the mechanical properties of the implant were fine-tuned in order to make them comparable to those reported for the bone tissue replaced by the prosthesis. The implant design and manufacturing methodology developed in this work considered the clinical condition of a specific patient and can be reproduced and adjusted for different types of bone tissue qualities for specific clinical requirements.

Objective To compare the clinical and radiographic outcomes between the Tri‐Lock Bone Preservation Stem (BPS) and the conventional standard Corail stem in primary total hip arthroplasty (THA). Methods From March 2012 to May 2014, we retrospectively reviewed 84 patients (104 hips) who received Tri‐Lock (BPS) and 84 patients (115 hips) who received conventional standard Corail stem in THA. Their mean ages were 53.12 ± 2.32 years and 52.00 ± 2.11 years, respectively. The clinical outcomes were assessed by Western Ontario and McMaster University Osteoarthritis Index (WOMAC), Pain Visual Analogue Scale (VAS) and Harris Hip Score (HHS). The radiological outcomes were evaluated by the radiological examination. Accordingly, Intraoperative and postoperative complications were observed as well. Results The mean follow‐up time was 48.23 ± 2.91 months in the Tri‐Lock (BPS) group and 49.11 ± 2.11 months in the Corail group, respectively. The bleeding volumes in two groups were comparable (169.22 ± 58.11 mL vs 179.30 ± 59.14 mL, P = 0.003), with more bleeding volume in Corail group patients, while no statistically significance with respect to operation time was observed (65.41 ± 6.24 min vs 63.99 ± 6.33 min, P = 0.567). The rates of intraoperative fracture was 8% for the Corail group while 1% for the Tri‐Lock (BPS) group (8% vs 1%, P = 0.030). At final follow‐up, no statistical differences in regard to HHS, WOMAC, and Pain VAS were revealed between the two groups (P > 0.05). The rate of thigh pain was higher in Corail group than in Tri‐lock (BPS) group (5% vs 0%, P = 0.043). However, incidence of stress shielding in grade 1 was higher in Tri‐Lock (BPS) than in the Corail group (76% vs 23%, P, This study demonstrated that the Tri‐lock (BPS) has similar performances in clinic outcomes compared to the Corail stem. Furthermore, the Tri‐lock (BPS) stem has lower incidence of thigh pain, stress shielding and intra‐operative fracture. In addition, taking into account of patients factors, including bone deficiency and convenience of extraction of the stem in hip revision, we recommend the Tri‐lock (BPS) stem may be a good alternative.

Purpose Total hip arthroplasties (THAs) are rising worldwide, as the functional request of patients who undergo this procedure. The trabeculae oriented pattern (TOP) is a modern cup, which follows the philosophy of the tissue sparing surgery (TSS). Focusing on clinical and radiological results and complications, the authors aim to highlight the outcomes of the TOP at a long-term follow-up (FU). Methods A retrospective analysis was completed on THA performed with the TOP cup between 1997 and 2015. Five hundred and eighty-eight patients sustained surgery, for a total of 662 cup implanted. Four hundred and sixty patients (524 hips) were examined. Mean FU was 12 ± 4.9 years (range 5–22). Clinical (HHS, OHS and VAS) and radiological data were obtained. Every complication, reoperation or revision was recorded and analyzed. Results Clinical evaluation revealed a HHS of 87.1 ± 13.8 an OHS of 41.3 ± 5.4, and a VAS of 1.2 ± 1.1. Acetabular osteolysis was observed in 53 hips. Overall survival rate of the cup was 90.5% (50 revisions), the main causes of cup substitution being aseptic loosening (AL) of the cup combined with the stem (26), of the cup only (13 cases) and periprosthetic joint infection (7 cases). Conclusion TOP cup has demonstrated a good overall survivorship at a long-term FU, even compared with other coated cups, providing excellent clinical result with low rate of complications. Its association with a neck sparing stem permits a physiologic load transmission, reducing the stress shielding effect that could cause early implant mobilization.

AimsIt has been hypothesized that proximal radial neck resorption (PRNR) following press-fit radial head arthroplasty (RHA) is due to stress-shielding. We compared two different press-fit stems by means of radiographs to investigate whether the shape and size of the stems are correlated with the degree of PRNR.MethodsThe radiographs of 52 RHAs were analyzed both at 14 days postoperatively and after two years. A cylindrical stem and a conical stem were implanted in 22 patients (group 1) and 30 patients (group 2), respectively. The PRNR was measured in the four quadrants of the radial neck and the degree of stem filling was calculated by analyzing the ratio between the prosthetic stem diameter (PSD) and the medullary canal diameter (MCD) at the proximal portion of the stem (level A), halfway along the stem length (level B), and distally at the stem tip (level C).ResultsOverall, 50 of the 52 patients displayed PRNR. The mean PRNR observed was 3.9 mm (0 to 7.4). The degree of endomedullary stem filling at levels A, B, and C was 96%, 90%, and 68% in group 1, and 96%, 72%, and 57%, in group 2, with differences being significant at levels B (p < 0.001) and C (p < 0.001). No significant correlations emerged between the severity of PRNR and the three stem/canal ratios either within each group or between the groups.ConclusionPRNR in press-fit RHA appears to be independent of the shape and size of the stems. Other causes besides stem design should be investigated to explain completely this phenomenon. Cite this article: Bone Joint J 2021;103-B(3):530–535.

Bone-patellar tendon-bone autograft for anterior cruciate ligament (ACL) reconstruction has the most data to support its use. However, there may still be room for improvement, and younger age, insufficient rehabilitation, altered neuromuscular patterns, and precocious return to play can increase risk of graft failure. High strength suture augmentation of soft-tissue repair or reconstruction has gained traction in a variety of applications for the knee, including medial collateral and posteromedial corner, lateral collateral ligament, posterior cruciate ligament, and ACL. For ACL reconstruction, the technique consists of using either suture or suture tape fixed at the femoral and tibial ACL footprints to allow for independent tensioning to back up the separately tensioned ACL reconstruction. The static augment serves as a load-sharing device, allowing the graft to see more strain during earlier levels of graft strain, until graft elongation occurs to a critical level whereby the augment will experience more strain than the graft. Hence, the “seat belt” analogy. This is distinct from static augmentation, where the high strength suture is fixed to the graft. Static augmentation (without tensioning separately from the graft) results in a load-sharing device and increased stiffness, but potential stress shielding compared with the “seat belt.” If suture tape augmentation improves patient outcome, it is a worthwhile to “click it.”

Background: The objective is to compare, by the means of finite elements analysis, the biomechanical behavior of a conventional stem of proven performance with a short stem based on the same fixation principles. Methods: A 3D femur was modeled from CT scan data, and real bone density measures were incorporated into it. Load stresses were applied to that bone in 3 different scenarios: without prosthesis, with the conventional stem, and with the short stem. Different bone loading patterns were compared by Gruen''s zones both visually and statistically using Welch''s test. Results: The implantation of a stem generates a certain degree of stress shielding in the surrounding bone, but the pattern of the change is very similar in the compared stem models. Although there is statistical significance (P < 0.01) in the mean stress variation in most of the Gruen''s zones, the magnitude of the difference is always under 2 MPa (range: 0.01 – 1.74 MPa). Conclusions: The bone loading patterns of the traditional stem and the short stem are very similar. Although there is no evidence of a link between biomechanics and clinical outcomes, our results may suggest that theoretical advantages of short stems can be exploited without the fear of altering bone loading patterns.

Cellular biomaterials with highly controlled microstructures are auspicious materials for medical orthopedics applications either as scaffold or implants due to their capability of encouraging better osseointegration and cell proliferation. This work focuses on the design and optimization of the hip implant by introducing a cellular structure into a solid implant to allow bone tissue ingrowth and reduce stress shielding. The cellular hip implant is incorporated with vintiles lattice topologies having different strut thickness and unit cell sizes to achieve the requirements of bone ingrowth and biomechanical mimic strength. All four optimized cellular hip implants with different unit cell size and porosity were manufactured via selective laser melting (SLM) using the Ti6Al4V material. To predict the mechanical property of hip cellular implant, finite element analysis (FEA) was employed and optimization methods were used for improving the mechanical performance of the hip cellular implant. To evaluate the reduction in stiffness of hip cellular implants, experimental tests were performed based on ISO 7206-4(2010) under static loading conditions. The experimental and simulation force-displacement results show that the optimized cellular hip implant has 62% lower stiffness than its solid counterpart. Moreover, the cellular hip implant was 50% lower in weight than the solid implant. Finally, the result of this study shows that the cellular implants with porosity of 56% and 58% have the potential to be used in orthopedic and prosthetic applications to improve osseointegration.

About 10 million fractures occur worldwide each year, of which more than 60% are long bone fractures. It is generally agreed that intramedullary nails have significant advantages in rigid fracture fixation. Metal intramedullary nails (INs) can provide strong support but a stress shielding effect can occur that results in nonunion healing in clinic. Nondegradable metals also need to be removed by a second operation. Could INs be biodegradable and used to overcome this issue? As current degradable biomaterials always suffer from low strength and cannot be used in Ins, herein, we report a novel device consisting of biodegradable IN (BIN) made for the first time with bioceramics. These BINs have an extremely high bending strength and stable internal and external structure. Experiments show that the BINs could not only fix and support the tibial fracture model, but also promote osteogenesis and affect the microenvironment of the bone marrow cavity. Therefore, they could be expected to replace traditional metal IN and become a more effective treatment option for tibial fractures.

Objective The aim of study was to evaluate periprosthetic bone mineral density (BMD) changes of proximal femur, osseointegration and clinical outcomes after implantation of short-stemmed and conventional straight-stemmed prostheses. Methods This prospective, randomized study included 50 patients with unilateral total hip replacement. The patients were randomized into 2 cohorts: patients with a cementless short stem Metha (n=25) and patients with a cementless conventional straight stem Bicontact evaluated as the control (n=25). Periprosthetic BMD changes were measured using a DEXA performed at one-week, 3-monts, 6-months and 1-year follow up. Clinical evaluation with Harris hip score (HHS) and radiographic assessment were performed through a 1 year follow up. Results Compared to 1-week postoperative assessment, there were differences in BMD changes between the groups at the final follow-up in all ROIs, with statistical significances in ROI 1, 2, 3, 6 and 7. The loss of periprosthetic BMD in all ROIs around straight stems at each time-point was observed. There was a tendency towards a regain of BMD in all ROIs at 1-year follow-up compared to the 3-months postoperative assessment with the short stems. Less pronounced bone loss was observed around the short stems that the straight stems in ROI 1 (‒2.9 % % vs ‒16.2 %), 5 (‒4.7 % vs ‒8.9 %) and 7 (‒8.6 % vs ‒20 %). The periprosthetic BMD exceeded baseline values in the short stem cohort in ROI 2 (+4.4 % vs ‒5 %), 3 (+5.6 % vs ‒2.5 %) and 6 (+4.3 % vs ‒10 %). All stems had a radiographically stable fixation. Stress shielding-related bone resorption was markedly lower in the short stem cohort. The HHS score was comparable between the two cohorts. Conclusion The implant-specific stress shielding altered the proximal loading condition for both stems; however, the results of this study suggest a more physiological strain distribution with the short stems versus the straight stems (Tab. 3, Fig. 3, Ref. 25).

Background Although the outcomes of total ankle arthroplasty (TAA) have improved, unsolved problems such as stress shielding remain. Although dual energy X-ray absorptiometry (DEXA) is the “gold standard” for evaluation of these issues, it is rarely used in patients after TAA. This study aimed to establish a scan technique and to assess the mechanical changes in bone density caused by bone stock preparation. Methods Eight fresh-frozen cadaver legs were investigated by DEXA before TAA, with implant in situ, and after implant removal. Scan surface, bone mineral content, and bone mineral density were analysed to assess mechanical bone mass changes. Results We examined data for density changes by bone compression after TAA, and found “good” results for internal reliability but only “acceptable” results for external reliability. Conclusions The results were reliable and reproducible. Using the present data, mechanical and biological processes can be considered together to understand the postoperative phases of bone remodelling after TAA.

Bone fractures are increasing day by day through numerous reasons. Tissue engineering is promising solution for bone tissue loss that current strategies cannot treat well or achieve satisfactory clinical outcomes. The scaffolds with required shape, size, physical, chemical and natural features for upgraded performance and for regenerating complex bone fracture is always in demand. Three-dimensional (3D) printing can create customized scaffolds that are profoundly alluring for bone tissue engineering. Over the previous decade, it is currently conceivable to create novel bone tissue scaffolds with designing structure with modified shape, large scale production, wettability, mechanical strength and cell reactions. The challenges of the scaffolds include sufficient mechanical strength and matching the mechanical properties of the scaffolds near to the bone properties. The stress shielding phenomenon also rises due to mismatch in elastic modulus. The elastic modulus of the cortical bone of human lies in the range of 2 to 16 GPa. The Elastic modulus of the steel used for biomedical application lies in the range of ∼ 200 GPa, which leads to encourage stress shielding. Bioabsorbable polymeric have unique properties such as matched mechanical strength with the natural bone, controlled rate of degradation, maintain porosity to make passage for interconnected neo bone regeneration. In case of adding bioactive nano filler materials, it was observed that the increase in the concentration of Hydroxyapatite, agglomeration observed. In order to avoid this, many technologies such as freeze drying, 3D printing, and other additive methods has been recommended. This article gives a review of ongoing advances in the scaffold fabrication techniques, functional scaffolds by adding useful nanomaterial and targeted application for particularly bone tissue regeneration.

Metaphyseal sleeves have shown an improved fixation in Revision Total Knee Arthroplasty (R-TKA) leading to a reduced aspetic loosening rate compared to other stem based fixation options. In the majority of these studies sleeve have been used with stems. Due to that is was not clear how much of this improved fixation could be rated to the sleeve and how much to the additional sleeves. In this review article we analysed the results of sleeve-only obtained in in-vitro or in-vivo studies. In Vitro models showed independent of the set-up a dominant fixation of the sleeve, an additional stem was not adding a lot to the overall fixation. Undersized additional stems showed an increased micromotion and the stem tip, while distal engaging stems showed a proximal stress shielding effect. Very interestingly an increased BMI had not a significant effect on primary fixation of the sleeve. Reduced bone quality on the other hand had and this effect was increased in cases with an increased BMI. In vivo results of sleeve-only patients showed comparable good results to sleeve and stem constructs. In particular on the femoral side the use of an additional stem is required only in a few scenarios. It has to be stated that the numbers of sleeves-only in rotating hinges is too low, to give any recommendation for this high constraint implants. Majority of cases was done with PS and VVC constraint. So far no in vivo data exist on the limitations of sleeve-only in patients with reduced bone quality and increased body weight. In conclusion we can state, that Sleeve-only is an option for R-TKA. In majority of cases the aspetic loosening rate is as low as with additional stems. The borderlines in terms of constraint, bone quality and body weight need to be investigated in future in vivo studies. The in vitro results look so far encouraging.

Background Reverse shoulder arthroplasty normally has adequate functional outcomes in patients with cuff tear arthropathy. The present study aimed to investigate the midterm clinical outcomes of reverse shoulder arthroplasty in Japanese patients with rheumatoid arthritis. Methods Between July 2014 and May 2016, reverse shoulder arthroplasty was performed in 14 rheumatic shoulders with joint destruction and rotator cuff tears. The range of motion, Constant score, and Shoulder36, which is a patient-reported outcome measure, were compared preoperatively and postoperatively. The prevalence of subscapular notching, subscapular osteophytes, postoperative fractures, and stress shielding of the humeral stem were evaluated by X-ray. Results Range of motion significantly improved from 77 to 122 degrees in flexion and from 67 to 111 degrees in abduction at four years. The Constant score significantly improved from 27 to 62, and each domain of Shoulder36 also significantly increased at four years. There was no dislocation, infection, or loosening of the prosthesis. Three shoulders presented scapular notching, and three cemented humeral stems showed stress shielding in the proximal humeral cortical bone. Conclusion Reverse shoulder arthroplasty performed in Japanese patients with rheumatoid arthritis not only decreased the pain and improved the function of the shoulder joint but also significantly improved patients' health and activity of daily living in midterm results.

The recent reverse total shoulder arthroplasty (TSA) implant designs employ shorter humeral component stems; some designs even eliminate the stem completely. The short stem provides several advantages: preserved bone, less stress shielding, ease of revision surgery, and freedom of humeral component location due to the minimal stem length and non-complex shape. However, due to the reduction in contact surface and frictional fixation, this stemless design may cause failure of the implant, especially during early stages following surgery. In this study, the effect of fin shape and fin length of stemless humeral components were investigated, and hypothesis was that stress and micromotion would decrease as the ratio of fin length to baseplate radius increases and the overall size of the humerus component increased. 15 different 3D models of stemless humeral components, 5 different lengths and 3 different shapes, within reverse TSA systems were developed. Each humerus component was analyzed using finite element analysis (FEA) to investigate the effects of stem length and fin shape on the initial stability of the component. The highest stress and micromotion were observed at the shortest fin length; lowest stress and micromotion were found at the longest fin length. Results suggest that the length of the fin affects the stress at the bone as well as the amount of micromotion; 20–30% longer fin length than baseplate radius would be ideal for the stemless humeral component design. However, the various fin shapes showed mixed effects on the results and further investigation is required.

In biomedical applications, the nature of biomaterials is transferred from bio-inert to make the metallic biomaterials biodegradable and multifunctional such as antibacterial, anti-proliferation, and anti-cancer, to eliminate secondary operation for implant removal. In the human body, Cortical and Cancellous are the two most important types of bone. Cortical bone is also known as the compact bone due to its dense structure and provides mechanical strength to the bone, whereas cancellous is the internal porous supporting structure. For a material that mimics the bone scaffold and acts as biomaterials, it should be non-toxic, possess good mechanical strength, helps in tissue growth, bone regeneration, and controlled biodegradation rate without any adverse effect. Many metals (Ti, Si, stainless steels), polymers, and ceramics are conventionally used as replacement biomaterials for broken or infected bone (orthopedic implants), but due to their unsatisfactory results for a long time use such as toxic metal ions release and stress shielding leading to secondary surgeries. Recently, researchers are focussing on biodegradable materials that do not need to be explanted from the organism. This review highlights the recent advancement in biodegradable materials i.e., magnesium, zinc, and iron, their manufacturing technique, challenges with present biomaterials, and some improvements that can help resolve the problems with current biomaterials.

INTRODUCTION The proximal humerus is a common location for primary and non-primary tumors. Reconstruction of the proximal humerus is commonly performed with an endoprosthesis with low rates of structural failure. The incidence and risk factors for stress shielding are under reported. METHODS Thirty-nine (19 male, 20 female) patients underwent resection of the proximal humerus and reconstruction with a cemented modular endoprosthesis between 2000 and 2018. The mean resection length was 12 ± 4 cm and was most commonly performed for metastatic disease (n = 26, 67%). RESULTS Stress shielding was observed in 9 (23%) patients at a mean of 29 (6-132) months postoperatively. Patients with stress shielding were noted to have shorter intramedullary stem length (87 vs. 107 mm, p