Aims. The aim of this study was to compare the clinical and radiological outcomes of reverse shoulder arthroplasty (RSA) using small and standard baseplates in Asian patients, and to investigate the impact of a mismatch in the sizes of the glenoid and the baseplate on the outcomes. Methods. This was retrospective analysis of 50 and 33 RSAs using a standard (33.8 mm, ST group) and a small (29.5 mm, SM group) baseplate of the Equinoxe reverse shoulder system, which were undertaken between January 2017 and March 2021. Radiological evaluations included the size of the glenoid, the β-angle, the inclination of the glenoid component, inferior overhang, scapular notching, the location of the central cage in the baseplate within the vault and the mismatch in size between the glenoid and baseplate. Clinical evaluations included the range of motion (ROM) and functional scores. In subgroup analysis, comparisons were performed between those in whom the vault of the glenoid was perforated (VP group) and those in whom it was not perforated (VNP group). Results. Perforation of the vault of the glenoid (p = 0.018) and size mismatch in height (p < 0.001) and width (p = 0.013) were significantly more frequent in the ST group than in the SM group. There was no significant difference in the clinical scores and ROM in the two groups, two years postoperatively (all p > 0.05). In subgroup analysis, the VP group had significantly less inferior overhang (p = 0.009), more scapular notching (p = 0.018), and more size mismatch in height (p < 0.001) and width (p = 0.025) than the VNP group. Conclusion. In Asian patients with a small glenoid, using a 29.5 mm small baseplate at the time of RSA was more effective in reducing size mismatch between the glenoid and the baseplate, decreasing the incidence of perforation of the glenoid vault, and achieving optimal positioning of the baseplate compared with the use of a 33.8 mm standard baseplate. However, longer follow-up is required to assess the impact of these findings on the clinical outcomes. Cite this article: Bone Joint J 2023;105-B(11):1189–1195

Introduction. A significant burden of disease exists with respect to critical sized bone defects; outcomes are unpredictable and often poor. There is no absolute agreement on what constitutes a “critically-sized” bone defect however it is widely considered as one that would not heal spontaneously despite surgical stabilisation, thus requiring re-operation. The aetiology of such defects is varied. High-energy trauma with soft tissue loss and periosteal stripping, bone infection and tumour resection all require extensive debridement and the critical-sized defects generated require careful consideration and strategic management. Current management practice of these defects lacks consensus. Existing literature tells us that tibial defects 25mm or great have a poor natural history; however, there is no universally agreed management strategy and there remains a significant evidence gap. Drawing its origins from musculoskeletal oncology, the Capanna technique describes a hybrid mode of reconstruction. Mass allograft is combined with a vascularised fibula autograft, allowing the patient to benefit from the favourable characteristics of two popular reconstruction techniques. Allograft confers initial mechanical stability with autograft contributing osteogenic, inductive and conductive capacity to encourage union. Secondarily its inherent vascularity affords the construct the ability to withstand deleterious effects of stressors such as infection that may threaten union. The strengths of this hybrid construct we believe can be used within the context of critical-sized bone defects within tibial trauma to the same success as seen within tumour reconstruction. Methodology. Utilising the Capanna technique in trauma requires modification to the original procedure. In tumour surgery pre-operative cross-sectional imaging is a pre-requisite. This allows surgeons to assess margins, plan resections and order allograft to match the defect. In trauma this is not possible. We therefore propose a two-stage approach to address critical-sized tibial defects in open fractures. After initial debridement, external fixation and soft tissue management via a combined orthoplastics approach, CT imaging is performed to assess the defect geometry, with a polymethylmethacrylate (PMMA) spacer placed at index procedure to maintain soft tissue tension, alignment and deliver local antibiotics. Once comfortable that no further debridement is required and the risk of infection is appropriate then 3D printing technology can be used to mill custom jigs. Appropriate tibial allograft is ordered based on CT measurements. A pedicled fibula graft is raised through a lateral approach. The peroneal vessels are mobilised to the tibioperoneal trunk and passed medially into the bone void. The cadaveric bone is prepared using the custom jig on the back table and posterolateral troughs made to allow insertion of the fibula, permitting some hypertrophic expansion. A separate medial incision allows attachment of the custom jig to host tibia allowing for reciprocal cuts to match the allograft. The fibula is implanted into the allograft, ensuring nil tension on the pedicle and, after docking the graft, the hybrid construct is secured with multi-planar locking plates to provide rotational stability. The medial window allows plate placement safely away from the vascular pedicle. Results. We present a 50-year-old healthy male with a Gustilo & Anderson 3B proximal tibial fracture, open posteromedially with associated shear fragment, treated using the Capanna technique. Presenting following a fall climbing additional injuries included a closed ipsilateral calcaneal and medial malleolar fracture, both treated operatively. Our patient underwent reconstruction of his tibia with the above staged technique. Two debridements were carried out due to a 48-hour delay in presentation due to remote geographical location of recovery. Debridements were carried out in accordance with BOAST guidelines; a spanning knee external fixator applied and a small area of skin loss on the proximal medial calf reconstructed with a split thickness skin graft. A revision cement spacer was inserted into the metaphyseal defect measuring 84mm. At definitive surgery the external fixator was removed and graft fixation was extended to include the intra-articular fragments. No intra-operative complications were encountered during surgeries. The patient returned to theatre on day 13 with a medial sided haematoma. 20ml of haemoserous fluid was evacuated, a DAIR procedure performed and antibiotic-loaded bioceramics applied locally. Samples grew Staphylococcus aureus and antibiotic treatment was rationalised to Co-Trimoxazole 960mg BD and Rifampicin 450mg BD. The patient has completed a six-week course of Rifampicin and continues on suppressive Co-Trimoxazole monotherapy until planned metalwork removal. There is no evidence of ongoing active infection and radiological evidence of early union. The patient is independently walking four miles to the gym daily and we believe, thus far, despite accepted complications, we have demonstrated a relative early success. Conclusions. A variety of techniques exist for the management of critical-sized bone defects within the tibia. All of these come with a variety of drawbacks and limitations. Whilst acceptance of a limb length discrepancy is one option, intercalary defects of greater than 5 to 7cm typically require reconstruction. In patients in whom fine wire fixators and distraction osteogenesis are deemed inappropriate, or are unwilling to tolerate the frequent re-operations and potential donor site morbidity of the Masqualet technique, the Capanna technique offers a novel solution. Through using tibial allograft to address the size mismatch between vascularised fibula and tibia, the possible complication of fatigue fracture of an isolated fibula autograft is potentially avoidable in patients who have high functional demands. The Capanna technique has demonstrated satisfactory results within tumour reconstruction. Papers report that by combining the structural strength of allograft with the osteoconductive and osteoinductive properties of a vascularised autograft that limb salvage rates of greater than 80% and union rates of greater than 90% are achievable. If these results can indeed be replicated in the management of critical-sized bone defects in tibial trauma we potentially have a treatment strategy that can excel over the more widely practiced current techniques

Revision hip surgery is about simplification. As such, a single revision stem makes sense. The most important advantage of Tapered Conical Revision (TCR) stem is versatility - managing ALL levels of femoral bone loss (present before revision or created during revision). The surgeon and team quickly gain familiarity with the techniques and instruments for preparation and implantation and subsequently master its use for a variety of situations. This ability to use the stem in a variety of bone loss situations eliminates intraoperative shuffle (changes in the surgical plan resulting in more instruments being opened), as bone loss can be significantly underestimated preoperatively or may change intraoperatively. Furthermore, distal fixation can be obtained simply and reliably. Paprosky 1 femoral defects can be treated with a primary-type stem for the most part. All other femoral defects can be treated with a TCR stem. Fully porous coated stems also work for many revisions but why have two different revision stem choices available when the TCR stems work for ALL defects?. TCR stems can be modular or monolithic but there are common keys to success. First and foremost, proper exposure is essential to assess bone defects and to safely prepare the femur. An extended osteotomy is often useful. Reaming distally to prepare a cone for fixation of the conical stem is a critical requirement to prevent subsidence (true for all revision stems). Restoration of hip mechanics (offset, leg length and stability) is fundamental to the clinical result. TCR stems have instrumentation and techniques that ensure this happens, since all this occurs AFTER distal stability is achieved. Modular TCR versions have some advantages. The proximal body size and length can be adjusted AFTER stem insertion if the stem goes deeper than the trial. Any proximal/distal bone size mismatch can be accommodated. If the surgeon believes that proximal bone ingrowth is important to facilitate proximal bone remodeling, modular TCR stems can more easily accomplish this. Further, proximal bone contact and osseointegration will protect the modular junction from stress and possible risk of fracture. Monolithic TCR versions also have some advantages. Modular junction mechanical integrity cannot accommodate smaller bone sizes. Shorter stem lengths are not available in modular versions, and shorter TCR stems are an option in many revision cases. The possibility of modular junction corrosion is eliminated and fracture of the stem at that junction, of course, is not possible. The monolithic stem option is less expensive as well. Consider Modular TCR stems in your learning curve, if you feel proximal bone osseointegration is important and if proximal/distal size mismatch is present. Consider Monolithic TCR stems after your learning curve to reduce cost, when a short stem works, and if a small stem is needed. Both Modular and Monolithic stems can be used for ALL cases with equal quality of result

Puropose. Three-dimensional (3D) templating based on computed tomography (CT) in total hip arthroplasty improves the accuracy of implant size. However, even when using 3D-CT preoperative planning, getting the concordance rate between planned and actual sizes to reach 100% is not easy. To increase the concordance rate, it is important to analyze the causes of mismatch; however, no such studies have been reported. This study had the following two purposes: to clarify the concordance rate in implant size between 3D-CT preoperative planning and actual size; and to analyze risk factors for mismatch. Materials and Methods. A single surgeon performed 149 THAs using Trident Cup and Centpillar Stem (Stryker) with CT-based navigation between September 2008 and August 2011. Minimal follow-up was 2 years. Patients with incomplete postoperative CT were excluded from this study. Based on these criteria, the study examined 124 hips in 111 patients (mean age, 60 years, mean BMI 23.2 kg/m2). The preoperative diagnosis was primary osteoarthritis in 8 hips, secondary osteoarthritis in 102 hips, osteonecrosis in 9 hips, rapidly destructive coxopathy in 4 hips and rheumatoid arthritis in 1 hip. We compared cup and stem sizes between preoperative planning and intraoperatively used components. Radiological evaluations were cortical index and canal flare index on preoperative X-rays. We evaluated preoperative planning and postoperative components for cup orientation, cup position, and stem alignment (anteversion, flexion and varus angle) on the CT-navigation system. Fixation of the stem was evaluated by X-ray radiography at 2 years postoperatively according to Engh's criteria. Statistical analysis was performed with the Mann-Whitney U test, and values of P<0.05 were considered statistically significant. Results and Discussion. The concordance rate in cup size between preoperative planning and used implants was 94.4% (117/124 hips) (CS group). A one-size larger cup was used in 4 hips (CO group), and a one-size smaller cup was implanted in 3 hips (CU group). No significant difference was seen between the CS group and the CO or CU groups in change of cup orientation and cup position from planning (P>0.05) (Table 1). The concordance rate of stem size between preoperative planning and used stem was 85.5% (106/124 hips) (SS group). A one-size larger stem than the plan was used in two hips (SO group), and a one-size smaller stem than the plan was implanted in 16 hips (SU group). Significant differences were seen between the SU and SS groups in flexion angle, varus angle, and canal flare index (P<0.05, Table 2). Extension or varus of the stem, or an increase in canal flare index, were risk factors for the used stem size being smaller than planned. On the latest follow-up X-rays, all 124 hips showed bone ingrown stability of the implants. Conclusion. The accuracy of implant size selection was 94.4% and 85.5% for the cup and stem, respectively. No factors associated with cup size mismatch were identified. Flexion angle, varus angle, and canal flare index were associated with stem size mismatch between preoperative planning and the actual used size

Recent innovations in total ankle replacement (TAR) have led to improvements in implant survivorship, accuracy of component positioning and sizing, and patient outcomes. CT-generated pre-operative plans and cutting guides show promising results in terms of placement enhancement and reproducibility in clinical studies. The purpose of this study was to determine the accuracy of 1) implant sizes used and 2) alignment corrections obtained intraoperatively using the cutting guides provided, compared to what was predicted in the CT generated pre-operative plans. This is a retrospective study looking at 36 patients who underwent total ankle arthroplasty using a CT generated pre-operative planning system between July 2015 and December 2017. Personalized pre-operative planning data was obtained from the implant company. Two evaluators took measurements of the angle corrected using pre- and post-operative weight bearing ankle AP X-rays. All patients had a minimum three-month follow-up with weightbearing postoperative radiographs. The actual correction calculated from the radiographic assessment was compared with the predicted angles obtained from pre-operative plans. The predicted and predicted alternative component sizes and actual sizes used were also compared. If either a predicted or predicted alternative size was implanted, we considered it to be accurate. Average age for all patients was 64 years (range 40–83), with a body mass index of 28.2 ± 5.6. All surgeries were performed by two foot and ankle surgeons. The average total surgical time was 110 ± 23 minutes. Pre-operative alignment ranged from 36.7 degrees valgus to 20 degrees varus. Average predicted coronal alignment correction was 0.8 degrees varus ± 9.3 degrees (range, 18.2 degrees valgus to 29 degrees varus) and average correction obtained was 2.1 degrees valgus ± 11.1 degrees. Average post-op alignment was consistently within 5 degrees of neutral. There were no significant differences between the predicted alignments and the postoperative weightbearing alignments. The predicted tibia implant size was accurate in all cases. The predicted sizes were less accurate for talar implants and predicted the actual talar implant size used in 66% of cases. In all cases of predicted talar size mismatch, surgical plans predicted 1 implant size larger than used. Preliminary analyses of our data is comparable to previous studies looking at similar outcomes. However, our study had higher pre-operative deformities. Despite that, post-op alignments were consistently within 5 degress of neutral with no significant difference between the predicted and actual corrections. Tibial implant sizes are highly accurate while talar implant sizes had a trend of being one size smaller than predicted. Moreover, this effect seems to be more pronounced in the earlier cases likely reflective of increasing surgeon comfort with the implant with each subsequent case. These results confirm that pre-operative cutting guides are indeed helpful in intra-operative implant selection and positioning, however, there is still some room for innovation

Objectives. Restoring more natural kinematics is crucial for the success of knee TKA. The relative size of the tibia to the femur may differ in each patient and requires the possibility to combine different tibia sizes for a given femur size. Therefore, TKA systems need to be designed to allow for different size combinations. In literature some report higher revision rates when the femoral size is greater than the tibia, while others find no impact of the size mismatch on the clinical outcome. The tibio-femoral kinematics resulting from different size combinations has not been analyzed yet. The Columbus Deep Dish implant (Aesculap, Tuttlingen, Germany) is designed to allow a full size compatibility. Therefore we hypothesized that the kinematics would not be affected by the different size combinations. The goal of this study was to investigate the impact on kinematics of different tibio-femoral size combinations with the Columbus Deep Dish implant. Methods. 6 fresh frozen cadavers were tested in a force controlled well established knee rig after implantation of a cruciate retaining, fixed bearing Columbus Deep Dish TKA (Aesculap, Tuttlingen, Germany). Femoro-tibial kinematics were recorded while performing a loaded squat from 30° to 130°. Specifically developed and manufactured inlays allowed simulating different tibia sizes on each bone/tibial implant. For each cadaver, a total of 4 different tibia sizes were tested (1 original size, 3 simulated different sizes). Tibio-femoral internal/external rotation and antero-posterior translation of the medial and of the lateral condyles were computed for all size combinations. The kinematics obtained with the simulated sizes were compared to the kinematics obtained with the original inlay. For each flexion angle from 30° to 130°, the difference between the rotation (resp. translation) obtained with the original inlay was subtracted from the rotation obtained with the simulated tibia size. The mean value and standard deviation of the differences were computed. Results. Each knee showed a singular kinematic pattern. This pattern remained the same for all size combinations. However the amplitude in rotation and translation varied: The mean difference reached −0,1 ±1,2° in internal/external rotation and 1,3 ± 3,3mm in translation. There was no significant difference between the used size combinations: among all knees no size combination consistently resulted in a significantly different kinematic. Conclusion. We can conclude that with a TKA system designed to allow full size compatibility the patient specific kinematic pattern is preserved when sizing up or down the tibia component with respect to the femur. For any figures or tables, please contact authors directly

A study by Harris reported a 40% incidence of femoral and acetabular dysplasia in routine idiopathic osteoarthritic patients. Due to pediatric screening in the United States, today most cases are minimally dysplastic requiring little modification from standard total hip surgical techniques. As the degree of dysplasia increases numerous anatomic distortions are present. These include high hip centers, relative acetabular retroversion, soft bone in the true acetabular area, increased femoral neck anteversion and relative posteriorly positioned greater trochanters, metaphyseal/diaphyseal size mismatch, and small femoral canals. Total hip replacements for these patients have known higher risks for earlier loosening, dislocation, and neurovascular injuries. Use of medialised small uncemented acetabular components placed in the anatomic acetabulum, modular uncemented femoral components, and diaphyseal rotational and shortening osteotomies has become a preferred method of treatment. In 2007, we reported our experience with this technique in 23 cases utilizing a subtrochanteric femoral osteotomy with a 5–14 year follow-up. There were 4 Crowe I, 3 Crowe II, 5 Crowe III, and 11 Crowe IV cases. All osteotomies healed. There were no femoral components revised. In most cases, small (mean 46 mm) hemispherical components were used without bulk allografts in all but 5 early cases. One acetabular component was revised for a recalled component. 3 acetabular liners were revised for wear (2 were very small cups with 4.7 mm poly thickness). Four patients sustained dislocations, with 2 closed and 2 open reductions. There were no neurovascular injuries. The Crowe classification is commonly used to preoperatively classify the degree of dysplasia. However, there are large variations in these anatomic distortions within each class, so it is difficult to preoperatively plan the acetabular component size needed and if one will need to do shortening and/or rotational osteotomy. So the surgeon needs to be prepared for these cases with smaller acetabular components and be prepared to perform a femoral osteotomy

Generally cemented total hip arthroplasty (THA) has become an extremely successful operation with excellent long-term results. Although it always remained a popular choice for the elderly patients in many countries, recent trends show an increased use of noncemented stems in all age populations in many national registries. So far, there has been no clear age associated recommendation, when a cemented stem should be used. Described major complications including periprosthetic fractures are usually associated with age >75 years, in many registries. Uncemented stems perform better than cemented stems in recent registries; however, unrecognised intra-operative femoral fractures may be an important reason for early failure of uncemented stems. Experimental studies have indicated that intra-operative fractures do affect implant survival, it has been shown that intra-operative and direct post-operative fractures increase the relative risk of revision during the first 6 post-operative months significantly. In addition it has been clearly shown, that uncemented stems were more frequently revised due to periprosthetic fracture during the first 2 post-operative years than cemented stems. Based on the overall femoral bone quality, especially in female patients >70 years, cemented fixation has a lower fracture risk. Based on the implant fixation type: metaphyseal vs. diaphyseal of various uncemented stems, major attention should be drawn to the intra-operative bone quality during the broaching process, especially for metaphyseal fixation stem types. Although cementless distal fixation can be achieved in thick cortices still in many patients, the incidence of associated thigh pain needs to be considered for some implant types. Furthermore small femoral canals might generate certain implant-bone size mismatch in relation to the proximal femur. In any cemented THA, a proper cementing technique is of major importance to assure longevity of implant fixation. This also includes proper implant sizing/templating, ensuring an adequate cement mantle thickness, which might be restricted in a small diameter femur. The desired outcome is a cement interdigitation into cancellous bone for 2–3 mm and an additional mantle of 2 mm pure cement. Consequently proper planning in small diameter patients, prevents sizing problems, while in few cases special/individualised stem sizes might be considered

Modern modular revision stems employ tapered conical (TCR) distal stems designed for immediate axial and rotational stability with subsequent osseo-integration of the stem. Modular proximal segments allow the surgeon to achieve bone contact proximally with eventual ingrowth that protects the modular junction. The independent sizing of the proximal body and distal stem allows for each portion to obtain intimate bony contact and gives the surgeon the ability precisely control the femoral head center of rotation, offset, version, leg length, and overall stability. The most important advantage of modular revision stems is versatility - the ability to manage ALL levels of femoral bone loss (present before revision or created during revision). Used routinely, this allows the surgeon to quickly gain familiarity with the techniques and instruments for preparation and implantation and subsequently master the use for all variety of situations. This also allows the operating room staff to become comfortable with the instrumentation and components. Additionally, the ability to use the stem in all bone loss situations eliminates intra-operative shuffle (changes in the surgical plan resulting in more instruments being opened), as bone loss can be significantly under-estimated pre-operatively or may change intra-operatively. Furthermore, distal fixation can be obtained simply and reliably. Paprosky 1 femoral defects can be treated with a primary-type stem for the most part. All other femoral defects can be treated with a TCR stem. Fully porous coated stems also work for many revisions but why have two different revision stem choices available when the TCR stems work for ALL defects?. The most critical advantage is the ability to separate completely the critical task of fixation from other important tasks of restoring offset, leg length, and stability. Once fixation is secured, the surgeon can concentrate on hip stability and on optimization of hip mechanics (leg length and offset). The ability to do this allows the surgeon to maximise patient functionality post-operatively. Modular tapered stems have TWO specific advantages over monolithic stems in this important surgical task. The proximal body size and length can be adjusted AFTER stem insertion if the stem goes deeper than the trial. Further, proximal/distal bone size mismatch can be accommodated. The surgeon can control the diameter of the proximal body to ensure proper bony apposition independent of distal fitting needs. If the surgeon believes that proximal bone ingrowth is important to facilitate proximal bone remodeling, modular TCR stems can more easily accomplish this. The most under-appreciated advantage is the straightforward instrumentation system that makes the operation easier for the staff and the surgeon, while enhancing the operating room efficiency and reducing cost. Also, although the implant itself may result in more cost, most modular systems allow for a decrease in inventory requirements, which make up the cost differential. One theoretical disadvantage of modular revision stems is modular junction fracture, which can happen if the junction itself is not protected by bone. Ensuring proximal bone support can minimise this problem. Once porous ingrowth occurs proximally, the risk of junction fracture is eliminated. Even NON-modular stems fracture when proximal bone support is missing. Another theoretical issue is modular junction corrosion but this not a clinical one, since both components are titanium. One can also fail to connect properly the two parts during surgery

A study by Harris reported a 40% incidence of femoral and acetabular dysplasia in routine idiopathic osteoarthritic patients. Fortunately most are minimally dysplastic requiring little modification from standard total hip surgical techniques. However, as the degree of dysplasia increases numerous anatomic distortions are present. These include high hip centres, relative acetabular retroversion, soft bone in the true acetabular area, increased femoral neck anteversion and relative posteriorly positioned greater trochanters, metaphyseal/diaphyseal size mismatch, and small femoral canals. Total hip replacements for these patients have known higher risks for earlier loosening, dislocation, and neurovascular injuries. Use of medialised small uncemented acetabular components placed in the anatomic acetabulum, modular uncemented femoral components, and diaphyseal rotational and shortening osteotomies has become the standard method of treatment. In 2007, we reported our experience with this technique in 23 cases utilising a subtrochanteric femoral osteotomy with a 5–14 year follow-up. There were 4 Crowe I, 3 Crowe II, 5 Crowe III, and 11 Crowe IV cases. All osteotomies healed. There were no femoral components revised. One acetabular component was revised for a recalled component. 3 acetabular liners were revised for wear (2 were very small cups with 4.7 mm poly thickness). 4 patients sustained dislocations, with 2 closed and 2 open reductions. There were no neurovascular injuries. The Crowe classification is commonly used to pre-operatively classify the degree of dysplasia. However, there are large variations in these anatomic distortions within each class, so it is difficult to pre-operatively plan the acetabular component size needed and if one will need to do shortening and/or rotational osteotomy. So the surgeon needs to bring their entire bag of tricks and tools for these surgeries

Cemented total hip arthroplasty (THA) has become an extremely successful operation with excellent long-term results. Although it always remained a popular choice for the elderly patients in many countries, recent trends show an increased use of non-cemented stems in all age populations in many national registries. So far, there has been no clear age associated recommendation, when a cemented stem should be used. Described major complications such as periprosthetic fractures are usually associated at age >75 years, in many registries. Uncemented stems perform better than cemented stems in recent registries; however, unrecognised intraoperative femoral fractures may be an important reason for early failure of uncemented stems. Experimental studies have indicated that intraoperative fractures do affect implant survival, in addition it has been shown that intraoperative and direct postoperative fractures increase the relative risk of revision during the first 6 postoperative months significantly. Furthermore it has been clearly shown, that uncemented stems were more frequently revised due to periprosthetic fracture during the first 2 postoperative years than cemented stems. Although often associated reduction of femoral bone quality in especially female patients >60 years, uncemented fixation has become the standard in most scenarios worldwide. Based on the implant fixation type: metaphyseal vs. diaphyseal of various uncemented stems, major attention should be, however, drawn to the intraoperative bone quality during the broaching process, especially for metaphyseal fixation stem types. Although cementless distal fixation can be achieved in thick cortices still in many patients, the incidence of associated thigh pain needs to be considered for some implant types. Furthermore small femoral canals might generate certain implant-bone size mismatch in relation to the proximal femur, thus nonoptimal fixation could be achieved. Consequently proper implant planning is mandatory preoperatively. In any cemented THA, a proper cementing technique is of major importance to assure longevity of implant fixation. This also includes proper implant sizing/ templating, ensuring an adequate cement mantle thickness, which might be restricted in a small diameter femur. The desired outcome is a cement interdigitation into cancellous bone for 2–3mm and an additional mantle of 2mm pure cement. Consequently proper planning in small diameter patients, prevents sizing problems, while in few cases special/individualised stem sizes might be considered. In summary attention needs to be drawn on small diameter stems, to prevent fractures and achieve proper implant fixation, in both uncemented and cemented fixation types. Proper implant planning preoperatively might be more important than in usual cases, while sometimes individual /small implant types might become necessary

SUMMARY. We report a prospective study of clinical data collected pre, intra and post operation to remove both cup and head components of 118 failed, current generation metal on metal (MOM) hips. Whilst component position was important, the majority were unexplained failures and of these the majority (63%) had cup inclination angles of less than 55 degrees. Poor biocompatibility of the wear debris may explain many of the failures. BACKGROUND. Morlock et al reported a retrospective analysis of 267 MOM hips but only 34 head and cup couples (ie most were femoral neck fractures) and without data necessary to define cause of failure. The commonest cause of failure in the National Joint Registry (NJR) is unexplained. METHODS. We categorised the cause of failure, as defined by the NJR, of all MOM hips received over an 18 month period that had a full set of pre, intra and post op data. A group of 40 patients with unilateral well functioning MOM hips was used for comparison. RESULTS. In the retrieval group, the median age was 61 years (25 to 87) and there were 80 females and 38 males. The median time between primary and revision operation was 35 months (4 to 121). Femoral head size was <50mm in 89 and >=50mm in 29. The causes of failure were: unexplained in 75; aseptic loosening (acetabular) in 12; aseptic loosening (femoral) in 7; dislocation/subluxation in 1; infection in 11; periprosthetic femoral fracture in 2; malalignment in 6; size mismatch in 3; other in 1. 47 (63%) of unexplained failures had cup inclination angles of less than 55 degrees. The unexplained failures had increased blood metal ions (p <0.0001) and cup inclination angle (p <0.005) but a decreased femoral head size (p <0.0001) when compared to well functioning MOM hip patients. CONCLUSION. The commonest cause of failed MOM hips was unexplained. Comparison to well functioning hips revealed that the mechanism may involve high blood metal ions but high cup inclination angle was not found in the majority of cases. Further biological and mechanical investigation into the underlying mechanism of failure is required

Literature surrounding artificial intelligence (AI)-related applications for hip and knee arthroplasty has proliferated. However, meaningful advances that fundamentally transform the practice and delivery of joint arthroplasty are yet to be realized, despite the broad range of applications as we continue to search for meaningful and appropriate use of AI. AI literature in hip and knee arthroplasty between 2018 and 2021 regarding image-based analyses, value-based care, remote patient monitoring, and augmented reality was reviewed. Concerns surrounding meaningful use and appropriate methodological approaches of AI in joint arthroplasty research are summarized. Of the 233 AI-related orthopaedics articles published, 178 (76%) constituted original research, while the rest consisted of editorials or reviews. A total of 52% of original AI-related research concerns hip and knee arthroplasty (n = 92), and a narrative review is described. Three studies were externally validated. Pitfalls surrounding present-day research include conflating vernacular (“AI/machine learning”), repackaging limited registry data, prematurely releasing internally validated prediction models, appraising model architecture instead of inputted data, withholding code, and evaluating studies using antiquated regression-based guidelines. While AI has been applied to a variety of hip and knee arthroplasty applications with limited clinical impact, the future remains promising if the question is meaningful, the methodology is rigorous and transparent, the data are rich, and the model is externally validated. Simple checkpoints for meaningful AI adoption include ensuring applications focus on: administrative support over clinical evaluation and management; necessity of the advanced model; and the novelty of the question being answered.

Cite this article: Bone Joint J 2022;104-B(12):1292–1303.

INTRODUCTION. Knee simulators are being used to evaluate wear. The current international standards have been developed from clinical investigations of the normal knee [1, 2] or from a single TKA patient [3, 4]. However, the forces and motions in a TKA patient differ from a normal knee and, furthermore, the resulting kinematic outcomes after TKA will depend on the design of the device [5]. Consequently, these standard tests may not recreate in-vivo conditions; therefore, the goal of this study was to perform a novel wear simulation using design-specific inputs that have been derived from fluoroscopic images of a deep knee bend. METHODS. A wear simulation was developed using fluoroscopic data from a pool of eighteen TKA patients performing a deep knee bend. All patients had a Sigma CR Fixed Bearing implant (DePuy) and were well functioning (Knee Society Score > 90). A single patient was selected that represented the typical motions, which was characterized by early rollback followed by anterior motion with an overall modest internal tibial rotation (Figure 1). The relative motion between the femoral and tibial components was transformed to match the coordinate system of an AMTI knee wear simulator [6] and a compressive load input was derived using inverse dynamics [7]. The resulting force and motions (Figure 2) were then applied in a wear simulation with 5 MRad crosslinked and remelted polyethylene for 3 Mcyc at 1 Hz. Components were carefully positioned and each joint (n=3) was tested in 25% bovine calf serum (Hyclone Laboratories), which was recirculated at 37±2°C [3]. Serum was supplemented with sodium azide and EDTA. Wear was quantified gravimetrically every 0.5 Mcyc using a digital balance (XP250, Mettler-Toledo) with load soak compensation. RESULTS. The knee simulator was able to recreate the in-vivo input kinematics. The femoral low point location revealed good agreement between in-vivo and in-vitro conditions and the overall pattern of the motion from full extension to maximum knee flexion was replicated (Figure 3). The measured wear from these inputs was very low (0.7 ± 0.2 mg/Mcyc). DISCUSSION. We have performed a device-specific wear simulation for a deep knee bend. Surprisingly, the wear associated with this activity was very low. It is possible that abnormal kinematics, including paradoxical anterior slide and reverse rotation, would generate higher wear. The deviations the between in-vivo and in-vitro kinematics (Figure 3) are likely due to a size mismatch across the transformation process. In a previous study [7] we recreated the in-vivo motions with better fidelity (RMS error = 0.6mm) using size matched components. Further work is needed to improve the transformation technique for different sized components. Also, similar approaches will be used in future investigations to study the effect of abnormal kinematics as well as other designs including rotating platform and cruciate substituting devices

Aims

The survival of humeral hemiarthroplasties in patients with relatively intact glenoid cartilage could theoretically be extended by minimizing the associated postoperative glenoid erosion. Ceramic has gained attention as an alternative to metal as a material for hemiarthroplasties because of its superior tribological properties. The aim of this study was to assess the in vitro wear performance of ceramic and metal humeral hemiarthroplasties on natural glenoids.

Periprosthetic fractures in total hip arthroplasty lead to considerable morbidity in terms of loss of component fixation, bone loss and subsequent function. The prevention, early recognition and appropriate management of such fractures are therefore critical. The pathogenesis of periprosthetic factors is multi-factorial. There are a number of intrinsic patient influences such as bone stock, biomechanics and compliance. There are also a host of extrinsic factors over which the surgeon has more control. The prevention of periprosthetic fractures requires careful pre-operative planning and templating, the availability of the necessary expertise and equipment, and knowledge of the potential pitfalls so that these can be avoided both intra-operatively and in follow-up. The key issues here are around identifying the risk, choosing the correct implant, understanding the anatomy, understanding the possible risks and avoiding them and using appropriate technique. There are a number of recognized risk factors for periprosthetic hip fractures. The prevalence of intra-operative fractures during total hip arthroplasty is higher in the patient with osteopenia/osteoporosis. Other conditions causing increased bone fragility, such as osteomalacia, Paget's disease, osteopetrosis, and osteogenesis imperfecta are also at a higher risk of intra-operative fracture. The use of more and more press fit cementless components has also increased the number of periprosthetic femoral fractures because of the force required to obtain such a fit. Complex deformities of the proximal femur, particularly when associated with a narrow medullary canal, as seen in secondary degenerative joint disease following developmental dysplasia of the hip may also increase the risk of intra-operative fractures. Revision surgery is associated with a higher risk of intra-operative fracture than primary hip replacement surgery. These fractures typically occur during hip dislocation, cement extraction, or reaming through old cement. Other risk factors for post-operative femoral fractures include loosening of the prosthesis with cortical bone loss, local osteolysis, stress risers within the cortex, such as old screw holes, the ends of plates, or impingement of a loose stem against the lateral femoral cortex. Periprosthetic acetabular fractures are increasingly recognized. This is in part due to the popularity of press fit components, which increase fracture risk both at the time of insertion and later due to medial wall stress shielding and pelvic osteolysis, and partly due to the increasing frequency of severe defects encountered at the time of revision surgery. Both over- and under-reaming are significant risk factors for acetabular fractures during total hip replacement. It is imperative to deal with the osteopenic patient gently and appropriately, being aware of the rim on the acetabular side and having the capacity for screw fixation where needed, having an understanding of where you wish to place your components and creating the appropriate runways for them, thinking about the stability of an implant as it is inserted and understanding that an implant that is less stable than expected probably is associated with either a size mismatch, a fracture or an implant that will not sit properly probably requires more or a different direction of reaming rather than harder blows with a hammer. A typical example where extra care is required is the scenario of a fractured neck of femur that requires total hip arthroplasty. The virgin native acetabulum in a patient likely to have some bony deficiency may be more difficult to deal with as it has a higher fracture risk. Pre-operative templating helps to identify the correct entry point for preparation of the lateral runway for linear insertion of a femoral stem. If resistance is met during insertion, the situation should be re-appraised to ensure that the direction and level of the rasp and prosthesis are the same. This reduces the risk of varus/valgus positioning which increases the risk of intra- and post-operative fractures. It is also important to avoid a change of version during insertion of the prosthesis as this can lead to high stresses

Introduction: Accurate size-matching of meniscal allografts is essential to maintain tibiofemoral congruity, and therefore function, especially when the surgical technique of using a bony bridge is employed. Methods of accurately assessing the required dimensions of an ideal meniscal allograft for each patient are limited. One popular method used is to choose the appropriate graft according to the bony tibial plateau dimensions of the patient, as determined from plain radiographs. Aims: To correlate meniscal dimensions with the bony dimensions of donor tibial plateaus. Methods: 22 left and right pairs of donor tibial plateaus with intact meniscal allografts were obtained, giving a total of 88 individual meniscal allografts. Using a digital micrometer, the following meniscal dimensions were measured: anteroposterior length, medial-lateral width, and the radial width at the mid-point of the meniscal body. Peripheral circumference was measured using flexible steel wire. Medial and lateral bony tibial plateau width and length, and total plateau width were also recorded. Linear regression analysis was used to obtain a formula, relating each meniscal dimension to the various bony plateau measurements. The resulting equations were used to calculate an expected meniscal dimension from the measured plateau dimensions, and this was compared to the size of the actual dimension measured. Results: The magnitude of the meniscal dimensions measured approximately fitted a normal distribution amongst all the specimens studied. The tibial plateau widths ranged from 69.2mm to 88.4mm (mean 78.5mm, s.d. 5.4mm), a 28% difference. The mean difference between meniscal measurements between the left and right knee of each pair was 7.3%. However, the greatest individual difference observed was 41.8%. The mean percentage error between meniscal dimensions calculated from specific compartmental tibial plateau dimensions, and the actual measured meniscal dimensions was 5.3% (s.d. 4.1%). When using just total bony tibial plateau width to calculate meniscal dimensions, the percentage error was 6.2% (s.d. 4.9%). This difference was not statistically significant. The maximum error between calculated and actual meniscal dimensions was 32%. Conclusions: This anatomical study shows that the use of plateau dimensions as a determinant for the sizing of meniscal allografts can be used to predict meniscal dimensions. However, mean errors are in the region of 5% – 6%, and can be as high as 32%. The potential mechanical effects of such graft to host size mismatching must be carefully borne in mind

Aims

Unicompartmental knee arthroplasty (UKA) has a higher risk of revision than total knee arthroplasty (TKA), particularly for younger patients. The outcome of knee arthroplasty is typically defined as implant survival or revision incidence after a defined number of years. This can be difficult for patients to conceptualize. We aimed to calculate the ‘lifetime risk’ of revision for UKA as a more meaningful estimate of risk projection over a patient’s remaining lifetime, and to compare this to TKA.

Aims

Proximal femoral endoprosthetic replacements (PFEPRs) are the most common reconstruction option for osseous defects following primary and metastatic tumour resection. This study aimed to compare the rate of implant failure between PFEPRs with monopolar and bipolar hemiarthroplasties and acetabular arthroplasties, and determine the optimum articulation for revision PFEPRs.