Aims. A functional anterior cruciate ligament (ACL) or posterior cruciate ligament (PCL) has been assumed to be required for patients undergoing unicompartmental knee arthroplasty (UKA). However, this assumption has not been thoroughly tested. Therefore, this study aimed to assess the biomechanical effects exerted by cruciate ligament-deficient knees with medial UKAs regarding different posterior tibial slopes. Methods. ACL- or PCL-deficient models with posterior tibial slopes of 1°, 3°, 5°, 7°, and 9° were developed and compared to intact models. The kinematics and contact stresses on the tibiofemoral joint were evaluated under gait cycle loading conditions. Results. Anterior translation increased in ACL-deficient UKA cases compared with intact models. In contrast, posterior translation increased in PCL-deficient UKA cases compared with intact models. As the posterior tibial slope increased, anterior translation of ACL-deficient UKA increased significantly in the stance phase, and posterior translation of PCL-deficient UKA increased significantly in the swing phase. Furthermore, as the posterior tibial slope increased, contact stress on the other compartment increased in cruciate ligament-deficient UKAs compared with intact UKAs. Conclusion. Fixed-bearing medial UKA is a viable treatment option for patients with cruciate ligament deficiency, providing a less invasive procedure and allowing patient-specific kinematics to adjust posterior tibial slope. Patient selection is important, and while AP kinematics can be compensated for by posterior tibial slope adjustment, rotational stability is a prerequisite for this approach. ACL- or PCL-deficient UKA that adjusts the posterior tibial slope might be an alternative treatment option for a skilled surgeon. Cite this article: Bone Joint Res 2022;11(7):494–502

Abstract. Introduction. The NHS long term plan endorses ‘personalised’, ‘digitally enabled’, ‘out of hospital’ care. Multiagency guidance (CPOC(2021)/NICE(2021)/GIRFT(2021)/NHSX(2021)) advocates an integrated ‘pathway’ approach to information sharing, shared-decision making and patient support. Digital solutions are the vehicle to deliver these agendas. Methods. In 2018 we developed a digital joint pathway (DJP) spanning the surgical care pathway (prehabilitation to rehabilitation) using the GoWellHealth platform. Patients listed for joint replacement are offered the DJP as routine care. Activity and engagement are monitored using the DJP data library. We sought to evidence our DJP by assessing patient engagement, experience and outcomes (OKS/EQ5D/Readmission). Results. Engagement. Consecutive cohort of the first 1195 patients registered. Activation rates were >85% and >70% viewed content within the DJP (median=15 access/pt; mean=83 minutes on DJP/pt). Engagement was similar irrespective of age and gender (p=NS). Older patients preferred to access via a computer. Experience. Qualitative interviews (n=14) demonstrated patients felt the DJP impacted positively on their health behaviours and contributed to their recovery. They spoke positively about the use of technology and the accessibility of the DJP. Outcomes. Comparison of patients on the DJP versus those not on the DJP using adjusted regression models demonstrated improved EQ5D=0.070 (95%CI=0.004-0.135,p=0.04), OKS=5.0 (95%CI=2.2-7.8,p<0.001) and readmission rates (3.6% versus 5.6%,p<0.01) for DJP patients. Conclusions. A DJP model for information delivery and patient support, across the entirety of the surgical pathway, is feasible and demonstrates high levels of patient engagement, experience and improved patient outcomes

Abstract. Introduction. 30-day emergency readmission is an indicator of treatment related complication once discharged, resulting in readmission. A board-approved quality improvement pathway was introduced to reduce elective re-admissions. Method. The pathway involved telephone and email contact details provision to patients for any non-life threatening medical assistance, allowing for initial nurse led management of all issues. A new clinic room available 7 days, and same day ultrasound scanning for DVT studies were introduced. A capability, opportunity and behavior model of change was implemented. Readmission rates before and six months after implementation were collected from Model Hospital. A database used to document patient communications was interrogated for patient outcomes. Results. Prior to implementation, readmission rates following elective primary total knee replacement (TKR) at the 1st business quarter of 2021 (April – June 2021), was 8.7%, (benchmark 3.8%). Following implementation, readmission rates decreased to 4.1% (October – December 2021). 54% of patients making contact were managed with telephone advice. 15% of patients required face-to-face clinic. 32% of those required a same day scan to exclude DVT (1/4). 20 out of 684 TKRs performed following protocol introduction were re-admitted within 30 days. Readmissions were 41% surgical, 29% medical. 52% were unaware of the newly implemented protocol. Further improvements have been made to the protocol based on these findings. Implementation of a suitable pathway can significantly reduce re-admission rates in our center and could be used to reduce readmission rates in other national elective treatment centers

Aims. A retrospective longitudinal study was conducted to compare directly volumetric wear of retrieved polyethylene inserts to predicted volumetric wear modelled from individual gait mechanics of total knee arthroplasty (TKA) patients. Methods. In total, 11 retrieved polyethylene tibial inserts were matched with gait analysis testing performed on those patients. Volumetric wear on the articular surfaces was measured using a laser coordinate measure machine and autonomous reconstruction. Knee kinematics and kinetics from individual gait trials drove computational models to calculate medial and lateral tibiofemoral contact paths and forces. Sliding distance along the contact path, normal forces and implantation time were used as inputs to Archard’s equation of wear to predict volumetric wear from gait mechanics. Measured and modelled wear were compared for each component. Results. Volumetric wear rates on eight non-delaminated components measured 15.9 mm. 3. /year (standard error (SE) ± 7.7) on the total part, 11.4 mm. 3. /year (SE ± 6.4) on the medial side and 4.4 (SE ± 2.6) mm. 3. /year on the lateral side. Volumetric wear rates modelled from patient gait mechanics predicted 16.4 mm. 3. /year (SE 2.4) on the total part, 11.7 mm. 3. /year (SE 2.1) on the medial side and 4.7 mm. 3. /year (SE 0.4) on the lateral side. Measured and modelled wear volumes correlated significantly on the total part (p = 0.017) and the medial side (p = 0.012) but not on the lateral side (p = 0.154). Conclusion. In the absence of delamination, patient-specific knee mechanics during gait directly affect wear of the tibial component in TKA. Cite this article: Bone Joint J 2020;102-B(6 Supple A):129–137

Introduction. Surgeons commonly resect additional distal femur during primary total knee arthroplasty (TKA) to correct a flexion contracture. However, the effect of joint line proximalization on TKA kinematics is unclear. Thus, our goal was to quantify the effect of additional distal femoral resection on knee extension and mid-flexion laxity. Methods. Six computational knee models with TKA-specific capsular and collateral ligament properties were implanted with a contemporary posterior-stabilized TKA. A 10° flexion contracture was modeled to simulate a capsular contracture. Distal femoral resections of +2 mm and +4 mm were simulated for each model. The knees were then extended under standardized torque to quantify additional knee extension achieved. Subsequently, varus and valgus torques of ±10 Nm were applied as the knee was flexed from 0° to 90° at the baseline, +2 mm, and +4 mm distal resections. Coronal laxity, defined as the sum of varus and valgus angulation with respective torques, was measured at mid-flexion. Results. With +2 mm and +4 mm of distal femoral resection, the knee extended an additional 4°±0.5° and 8°±0.75°, respectively. At 30° and 45°of flexion, baseline laxity averaged 4.8° and 5.0°, respectively. At +2 mm resection, mean coronal laxity increased by 3.1° and 2.7° at 30° and 45°of flexion, respectively. At +4 mm resection, mean coronal laxity increased by 6.5° and 5.5° at 30° and 45° of flexion, respectively. Maximal increased coronal laxity for a +4 mm resection occurred at a mean 16° (range, 11–27°) of flexion with a mean increased laxity of 7.8° from baseline. Conclusion. While additional distal femoral resection in primary TKA increases knee extension, the consequent joint line elevation induces up to 8° of coronal laxity in mid-flexion in this computational model. As such, posterior capsular release prior to resecting additional distal femur to correct a flexion contracture should be considered

Introduction. Initial post-operative implant instability leads to impaired osseointegration, one of the most common reasons for aseptic loosening and revision surgery. In this study, we developed a novel murine model of implant instability and demonstrated the anabolic effect of immediate and delayed intermittent Parathyroid Hormone (iPTH) treatment in the setting of instability-induced osseointegration failure. Methods. 3D-printed titanium implants were inserted in an oversized drill-hole in the tibia of C57Bl/6 mice (n=54). After implantation, the mice were randomly divided in 3 treatment groups (control: PBS-vehicle; iPTH; delayed iPTH). Radiographic analysis was performed to confirm signs of implant loosening. Peri-implant tissue formation was assessed through histology. Osseointegration was assessed through µCT and biomechanical pullout testing. Results. Immediate iPTH treatment reduced radiolucencies and induced a distinct pedestal sign distal to the implant stem (white arrow Fig 1A). The PBS treated mice had fibrous tissue implant encapsulation, whereas new mineralized tissue and no fibrous tissue was observed with immediate iPTH treatment (Fig 1E). Delayed iPTH treatment was also able to exhibit significant peri-implant bone mineralization, osteoblasts, angiogenesis, and a reduction of fibrous tissue (Fig 2A-B). iPTH treatment increased the force required to pull out the implant significantly from 8.41 ± 8.15N in the PBS group to 21.49 ± 10.45N and 23.68 ± 8.99N, in the immediate and delayed iPTH treatment groups, respectively (Fig 2D). PBS vehicle resulted in a bone volume/trabecular volume (BV/TV) of 0.23 ± 0.03, while immediate and delayed iPTH treatment increased BV/TV significantly to 0.46 ± 0.07 and 0.34 ± 0.10, respectively (Fig 2E). Conclusion. Immediate iPTH treatment prevents peri-implant fibrous tissue formation and enhances peri-implant bone formation in our murine model of mechanical instability. Delayed iPTH treatment was able to resolve the peri-implant fibrous tissue and stimulate bone formation. This study potentially addresses a leading cause of aseptic loosening by demonstrating that initial implant instability can be rescued by iPTH even with delayed start of treatment. For any figures or tables, please contact authors directly

Objectives. Static radiostereometric analysis (RSA) using implanted markers is considered the most accurate system for the evaluation of prosthesis migration. By using CT bone models instead of markers, combined with a dynamic RSA system, a non-invasive measurement of joint movement is enabled. This method is more accurate than current 3D skin marker-based tracking systems. The purpose of this study was to evaluate the accuracy of the CT model method for measuring knee joint kinematics in static and dynamic RSA using the marker method as the benchmark. Methods. Bone models were created from CT scans, and tantalum beads were implanted into the tibia and femur of eight human cadaver knees. Each specimen was secured in a fixture, static and dynamic stereoradiographs were recorded, and the bone models and marker models were fitted to the stereoradiographs. Results. Results showed a mean difference between the two methods in all six degrees of freedom for static RSA to be within -0.10 mm/° and 0.08 mm/° with a 95% limit of agreement (LoA) ranging from ± 0.49 to 1.26. Dynamic RSA had a slightly larger range in mean difference of -0.23 mm/° to 0.16 mm/° with LoA ranging from ± 0.75 to 1.50. Conclusions. In a laboratory-controlled setting, the CT model method combined with dynamic RSA may be an alternative to previous marker-based methods for kinematic analyses. Cite this article: K. Stentz-Olesen, E. T. Nielsen, S. De Raedt, P. B. Jørgensen, O. G. Sørensen, B. L. Kaptein, M. S. Andersen, M. Stilling. Validation of static and dynamic radiostereometric analysis of the knee joint using bone models from CT data. Bone Joint Res 2017;6:376–384. DOI: 10.1302/2046-3758.66.BJR-2016-0113.R3

Cartilage repair in terms of replacement, or regeneration of damaged or diseased articular cartilage with functional tissue, is the ‘holy grail’ of joint surgery. A wide spectrum of strategies for cartilage repair currently exists and several of these techniques have been reported to be associated with successful clinical outcomes for appropriately selected indications. However, based on respective advantages, disadvantages, and limitations, no single strategy, or even combination of strategies, provides surgeons with viable options for attaining successful long-term outcomes in the majority of patients. As such, development of novel techniques and optimisation of current techniques need to be, and are, the focus of a great deal of research from the basic science level to clinical trials. Translational research that bridges scientific discoveries to clinical application involves the use of animal models in order to assess safety and efficacy for regulatory approval for human use. This review article provides an overview of animal models for cartilage repair. Cite this article: Bone Joint Res 2014;4:89–94

Aims. It is increasingly appreciated that coordinated regulation of angiogenesis and osteogenesis is needed for bone formation. How this regulation is achieved during peri-implant bone healing, such as osseointegration, is largely unclear. This study examined the relationship between angiogenesis and osteogenesis in a unique model of osseointegration of a mouse tibial implant by pharmacologically blocking the vascular endothelial growth factor (VEGF) pathway. Materials and Methods. An implant was inserted into the right tibia of 16-week-old female C57BL/6 mice (n = 38). Mice received anti-VEGF receptor-1 (VEGFR-1) antibody (25 mg/kg) and VEGF receptor-2 (VEGFR-2) antibody (25 mg/kg; n = 19) or an isotype control antibody (n = 19). Flow cytometric (n = 4/group) and immunofluorescent (n = 3/group) analyses were performed at two weeks post-implantation to detect the distribution and density of CD31. hi. EMCN. hi. endothelium. RNA sequencing analysis was performed using sorted CD31. hi. EMCN. hi. endothelial cells (n = 2/group). Osteoblast lineage cells expressing osterix (OSX) and osteopontin (OPN) were also detected with immunofluorescence. Mechanical pull-out testing (n = 12/group) was used at four weeks post-implantation to determine the strength of the bone-implant interface. After pull-out testing, the tissue attached to the implant surface was harvested. Whole mount immunofluorescent staining of OSX and OPN was performed to determine the amount of osteoblast lineage cells. Results. Flow cytometry revealed that anti-VEGFR treatment decreased CD31. hi. EMCN. hi. vascular endothelium in the peri-implant bone versus controls at two weeks post-implantation. This was confirmed by the decrease of CD31 and endomucin (EMCN) double-positive cells detected with immunofluorescence. In addition, treated mice had more OPN-positive cells in both peri-implant bone and tissue on the implant surface at two weeks and four weeks, respectively. More OSX-positive cells were present in peri-implant bone at two weeks. More importantly, anti-VEGFR treatment decreased the maximum load of pull-out testing compared with the control. Conclusion. VEGF pathway controls the coupling of angiogenesis and osteogenesis in orthopaedic implant osseointegration by affecting the formation of CD31. hi. EMCN. hi. endothelium. Cite this article: Bone Joint J 2019;101-B(7 Supple C):108–114

Aims

To explore the efficacy of extracorporeal shockwave therapy (ESWT) in the treatment of osteochondral defect (OCD), and its effects on the levels of transforming growth factor (TGF)-β, bone morphogenetic protein (BMP)-2, -3, -4, -5, and -7 in terms of cartilage and bone regeneration.

Early and accurate prediction of hospital length-of-stay (LOS) in patients undergoing knee replacement is important for economic and operational reasons. Few studies have systematically developed a multivariable model to predict LOS. We performed a retrospective cohort study of 1609 patients aged ≥ 50 years who underwent elective, primary total or unicompartmental knee replacements. Pre-operative candidate predictors included patient demographics, knee function, self-reported measures, surgical factors and discharge plans. In order to develop the model, multivariable regression with bootstrap internal validation was used. The median LOS for the sample was four days (interquartile range 4 to 5). Statistically significant predictors of longer stay included older age, greater number of comorbidities, less knee flexion range of movement, frequent feelings of being down and depressed, greater walking aid support required, total (versus unicompartmental) knee replacement, bilateral surgery, low-volume surgeon, absence of carer at home, and expectation to receive step-down care. For ease of use, these ten variables were used to construct a nomogram-based prediction model which showed adequate predictive accuracy (optimism-corrected R. 2. = 0.32) and calibration. If externally validated, a prediction model using easily and routinely obtained pre-operative measures may be used to predict absolute LOS in patients following knee replacement and help to better manage these patients. . Cite this article: Bone Joint J 2013;95-B:1490–6

Introduction. Patient-reported outcome (PRO) data are variably collected before and after total hip/knee arthroplasty (THA/TKA). We assessed the generalizability of incentivized, prospectively collected PRO data for THA/TKA patient-reported outcome performance measure (PRO-PM) development. Methods. The Centers for Medicare & Medicaid Services (CMS) received PRO data voluntarily submitted by hospitals in a bundled payment model for THA/TKA procedures. Participating hospitals who collected and successfully submitted these data received an increase in their overall quality score, possibly resulting in a positive impact on model reconciliation payments. PRO data were collected from Medicare Fee-For-Service beneficiaries >= 65 years undergoing elective primary THA/TKA procedures from July 1 to August 31, 2016 at hospitals participating in the model. Pre-operative PRO and risk variable data were collected 0 – 90 days prior to surgery, while post-operative PRO data were collected 270 – 365 days following elective THA/TKA. PRO pre-op and post-op data were matched to Medicare claims data for determination of clinically eligible procedures and clinical comorbidities. We compared the characteristics of patients submitting PRO data to other elective primary THA/TKA recipients in the US. Results. Four patient characteristics were associated with HOOS Jr. mean change scores (sex, narcotic use in past 90 days, other joint pain, and back pain) and four with KOOS Jr. mean change scores (sex, Hispanic ethnicity, other joint pain, and back pain). The frequency of simultaneous bilateral procedures, dementia, trauma, and dialysis were statistically significantly lower in patients submitting PRO data compared to other US Medicare beneficiaries undergoing elective primary THA/TKA, but no difference was greater than 1.5% absolute percentage points between groups. Conclusions. Offering financial incentives in alternative payment models to encourage PRO data collection and submission can produce generalizable data for PRO measure development. The possibility of non-respondent biases will need to be specifically considered in measure development

Objectives. An important measure for the diagnosis and monitoring of knee osteoarthritis is the minimum joint space width (mJSW). This requires accurate alignment of the x-ray beam with the tibial plateau, which may not be accomplished in practice. We investigate the feasibility of a new mJSW measurement method from stereo radiographs using 3D statistical shape models (SSM) and evaluate its sensitivity to changes in the mJSW and its robustness to variations in patient positioning and bone geometry. Materials and Methods. A validation study was performed using five cadaver specimens. The actual mJSW was varied and images were acquired with variation in the cadaver positioning. For comparison purposes, the mJSW was also assessed from plain radiographs. To study the influence of SSM model accuracy, the 3D mJSW measurement was repeated with models from the actual bones, obtained from CT scans. Results. The SSM-based measurement method was more robust (consistent output for a wide range of input data/consistent output under varying measurement circumstances) than the conventional 2D method, showing that the 3D reconstruction indeed reduces the influence of patient positioning. However, the SSM-based method showed comparable sensitivity to changes in the mJSW with respect to the conventional method. The CT-based measurement was more accurate than the SSM-based measurement (smallest detectable differences 0.55 mm versus 0. 82 mm, respectively). Conclusion. The proposed measurement method is not a substitute for the conventional 2D measurement due to limitations in the SSM model accuracy. However, further improvement of the model accuracy and optimisation technique can be obtained. Combined with the promising options for applications using quantitative information on bone morphology, SSM based 3D reconstructions of natural knees are attractive for further development. Cite this article: E. A. van IJsseldijk, E. R. Valstar, B. C. Stoel, R. G. H. H. Nelissen, N. Baka, R. van’t Klooster, B. L. Kaptein. Three dimensional measurement of minimum joint space width in the knee from stereo radiographs using statistical shape models. Bone Joint Res 2016;320–327. DOI: 10.1302/2046-3758.58.2000626

Introduction. Poor osseointegration of cementless implants is the leading clinical cause of implant loosening, subsidence, and replacement failure, which require costly and technically challenging revision surgery. The mechanism of osseointegration requires further elucidation. We have recently developed a novel titanium implant for the mouse tibia that maintains in vivo knee joint function and allows us to study osseointegration in an intra-articular, load-bearing environment. Vascular endothelial growth factor (VEGF) is one of the most important growth factors for regulation of vascular development and angiogenesis. It also plays critical roles in skeletal development and bone repair and regeneration. A specialized subset of vascular endothelium, CD31. hi. EMCN. hi. cells displaying high cell surface expression of CD31 and Endomucin, has been reported to promote osteoblast maturation and may be responsible for bone formation during development and fracture healing. Because of their potential role in osseointegration, the aim of this study was to use our mouse implant model to investigate the role of VEGF and CD31. hi. EMCN. hi. endothelium in osseointegration. Methods. Under an IACUC-approved protocol, the implant was inserted into the right tibia of 16-week-old female C57BL/6 mice (N = 38). The mice were then randomized into 2 groups: Control group (N=19) and Anti-VEGFR group (N=19). A cocktail of VEGFR-1 antibody (25mg/kg) and VEGFR-2 antibody (25mg/kg) was given to the mice in the Anti-VEGFR group by intraperitoneal injection every third day starting immediately after surgery until euthanasia. An equivalent amount of an isotype control antibody was given to the control group. Flow cytometric (N = 4/group) and immunofluorescencent (N = 3/group) analyses were performed at 2 weeks post-implantation to detect the distribution and density of CD31. hi. EMCN. hi. endothelium in the peri-implant bone. Pull-out testing was used at 4 weeks post-implantation to determine the strength of the bone-implant interface. Results. Flow cytometry revealed that Anti-VEGFR treatment decreased CD31. hi. EMCN. hi. vascular endothelium percentage in the peri-implant bone vs. control (p = 0.039) at 2 weeks post-implantation (Fig. 1). This was confirmed by the decrease of CD31 and EMCN double positive cells detected with immunofluorescence at the same time point (Fig. 2). More importantly, anti-VEGFR treatment decreased the maximum load of pullout testing compared with control (p = 0.042) (Fig. 3). Conclusion. VEGF is a key mediator of osseointegration and the development of CD31. hi. EMCN. hi. endothelium. This may provide a new drug target for the enhancement of osseointegration. We have also developed a system to run flow cytometric analysis and perform fluorescent staining on the limited tissue around the implant in this mouse model. This will be a powerful platform for future mechanistic studies on osseointegration. For any figures or tables, please contact authors directly

Objectives. Our objective in this article is to test the hypothesis that type 2 diabetes mellitus (T2DM) is a factor in the onset and progression of osteoarthritis, and to characterise the quality of the articular cartilage in an appropriate rat model. Methods. T2DM rats were obtained from the UC Davis group and compared with control Lewis rats. The diabetic rats were sacrificed at ages from six to 12 months, while control rats were sacrificed at six months only. Osteoarthritis severity was determined via histology in four knee quadrants using the OARSI scoring guide. Immunohistochemical staining was also performed as a secondary form of osteoarthritic analysis. Results. T2DM rats had higher mean osteoarthritis scores than the control rats in each of the four areas that were analysed. However, only the results at the medial and lateral femur and medial tibia were significant. Cysts were also found in T2DM rats at the junction of the articular cartilage and subchondral bone. Immunohistochemical analysis does not show an increase in collagen II between control and T2DM rats. Mass comparisons also showed a significant relationship between mass and osteoarthritis score. Conclusions. T2DM was found to cause global degeneration in the UCD rat knee joints, suggesting that diabetes itself is a factor in the onset and progression of osteoarthritis. The immunohistochemistry stains showed little to no change in collagen II degeneration between T2DM and control rats. Overall, it seems that the animal model used is pertinent to future studies of T2DM in the development and progression of osteoarthritis. Cite this article: Bone Joint Res 2014;3:203–11

Abstract

We used three-dimensional movement analysis by computer modelling of knee flexion from 0° to 50° in 14 knees in 12 patients with recurrent patellar dislocation and in 15 knees in ten normal control subjects to compare the in vivo three-dimensional movement of the patella. Flexion, tilt and spin of the patella were described in terms of rotation angles from 0°. The location of the patella and the tibial tubercle were evaluated using parameters expressed as percentage patellar shift and percentage tubercle shift. Patellar inclination to the femur was also measured and patellofemoral contact was qualitatively and quantitatively analysed. The patients had greater values of spin from 20° to 50°, while there were no statistically significant differences in flexion and tilt. The patients also had greater percentage patellar shift from 0° to 50°, percentage tubercle shift at 0° and 10° and patellar inclination from 0° to 50° with a smaller oval-shaped contact area from 20° to 50° moving downwards on the lateral facet. Patellar movement analysis using a three-dimensional computer model is useful to clearly demonstrate differences between patients with recurrent dislocation of the patella and normal control subjects

This study demonstrates a significant correlation between the American Knee Society (AKS) Clinical Rating System and the Oxford Knee Score (OKS) and provides a validated prediction tool to estimate score conversion. A total of 1022 patients were prospectively clinically assessed five years after TKR and completed AKS assessments and an OKS questionnaire. Multivariate regression analysis demonstrated significant correlations between OKS and the AKS knee and function scores but a stronger correlation (r = 0.68, p < 0.001) when using the sum of the AKS knee and function scores. Addition of body mass index and age (other statistically significant predictors of OKS) to the algorithm did not significantly increase the predictive value. The simple regression model was used to predict the OKS in a group of 236 patients who were clinically assessed nine to ten years after TKR using the AKS system. The predicted OKS was compared with actual OKS in the second group. Intra-class correlation demonstrated excellent reliability (r = 0.81, 95% confidence intervals 0.75 to 0.85) for the combined knee and function score when used to predict OKS. Our findings will facilitate comparison of outcome data from studies and registries using either the OKS or the AKS scores and may also be of value for those undertaking meta-analyses and systematic reviews. Cite this article: Bone Joint J 2015;97-B:503–9

We investigated the three-dimensional morphological differences of the articular surface of the femoral trochlea in patients with recurrent dislocation of the patella and a normal control group using three-dimensional computer models. There were 12 patients (12 knees) and ten control subjects (ten knees). Three-dimensional computer models of the femur, including the articular cartilage, were created. Evaluation was performed on the shape of the articular surface, focused on its convexity, and the proximal and mediolateral distribution of the articular cartilage of the femoral trochlea. The extent of any convexity, and the proximal distribution of the articular cartilage, expressed as the height, were shown by the angles about the transepicondylar axis. The mediolateral distribution of the articular cartilage was assessed by the location of the medial and lateral borders of the articular cartilage. The mean extent of convexity was 24.9° . sd. 6.7° for patients and 11.9° . sd. 3.6° for the control group (p < 0.001). The mean height of the articular cartilage was 91.3° . sd. 8.3° for the patients and 83.3° . sd. 7.7° for the control group (p = 0.03), suggesting a wider convex trochlea in the patients with recurrent dislocation of the patella caused by the proximally-extended convex area. The lateral border of the articular cartilage of the trochlea in the patients was more laterally located than in the control group. Our findings therefore quantitatively demonstrated differences in the shape and distribution of the articular cartilage on the femoral trochlea between patients with dislocation of the patella and normal subjects

A 5 year review of factors instigating malpractice claims and likely to result in a payout. Possible lessons for the future.