Aims. The aim of this study was to compare the biomechanical models of two frequently used techniques for reconstructing severe acetabular defects with pelvic discontinuity in revision total hip arthroplasty (THA) – the Trabecular Metal Acetabular Revision System (TMARS) and custom triflange acetabular components (CTACs) – using virtual modelling. Methods. Pre- and postoperative CT scans from ten patients who underwent revision with the TMARS for a Paprosky IIIB acetabular defect with pelvic discontinuity were retrospectively collated. Computer models of a CTAC implant were designed from the preoperative CT scans of these patients. Computer models of the TMARS reconstruction were segmented from postoperative CT scans using a semi-automated method. The amount of bone removed, the implant-bone apposition that was achieved, and the restoration of the centre of rotation of the hip were compared between all the actual TMARS and the virtual CTAC implants. Results. The median amount of bone removed for TMARS reconstructions was significantly greater than for CTAC implants (9.07 cm. 3. (interquartile range (IQR) 5.86 to 21.42) vs 1.16 cm. 3. (IQR 0.42 to 3.53) (p = 0.004). There was no significant difference between the median overall implant-bone apposition between TMARS reconstructions and CTAC implants (54.8 cm. 2. (IQR 28.2 to 82.3) vs 56.6 cm. 2. (IQR 40.6 to 69.7) (p = 0.683). However, there was significantly more implant-bone apposition within the residual acetabulum (45.2 cm. 2. (IQR 28.2 to 72.4) vs 25.5 cm. 2. (IQR 12.8 to 44.1) (p = 0.001) and conversely significantly less apposition with the outer cortex of the pelvis for TMARS implants compared with CTAC reconstructions (0 cm. 2. (IQR 0 to 13.1) vs 23.2 cm. 2. (IQR 16.4 to 30.6) (p = 0.009). The mean centre of rotation of the hip of TMARS reconstructions differed by a mean of 11.1 mm (3 to 28) compared with CTAC implants. Conclusion. In using TMARS, more bone is removed, thus achieving more implant-bone apposition within the residual acetabular bone. In CTAC implants, the amount of bone removed is minimal, while the implant-bone apposition is more evenly distributed between the residual acetabulum and the outer cortex of the pelvis. The differences suggest that these implants used to treat pelvic discontinuity might achieve short- and long-term stability through different biomechanical mechanisms. Cite this article: Bone Joint J 2024;106-B(5 Supple B):74–81

Aims. In computer simulations, the shape of the range of motion (ROM) of a stem with a cylindrical neck design will be a perfect cone. However, many modern stems have rectangular/oval-shaped necks. We hypothesized that the rectangular/oval stem neck will affect the shape of the ROM and the prosthetic impingement. Methods. Total hip arthroplasty (THA) motion while standing and sitting was simulated using a MATLAB model (one stem with a cylindrical neck and one stem with a rectangular neck). The primary predictor was the geometry of the neck (cylindrical vs rectangular) and the main outcome was the shape of ROM based on the prosthetic impingement between the neck and the liner. The secondary outcome was the difference in the ROM provided by each neck geometry and the effect of the pelvic tilt on this ROM. Multiple regression was used to analyze the data. Results. The stem with a rectangular neck has increased internal and external rotation with a quatrefoil cross-section compared to a cone in a cylindrical neck. Modification of the cup orientation and pelvic tilt affected the direction of projection of the cone or quatrefoil shape. The mean increase in internal rotation with a rectangular neck was 3.4° (0° to 7.9°; p < 0.001); for external rotation, it was 2.8° (0.5° to 7.8°; p < 0.001). Conclusion. Our study shows the importance of attention to femoral implant design for the assessment of prosthetic impingement. Any universal mathematical model or computer simulation that ignores each stem’s unique neck geometry will provide inaccurate predictions of prosthetic impingement. Cite this article: Bone Joint Res 2021;10(12):780–789

Aims. The rationale for exacting restoration of skeletal anatomy after unstable ankle fracture is to improve outcomes by reducing complications from malunion; however, current definitions of malunion lack confirmatory clinical evidence. Methods. Radiological (absolute radiological measurements aided by computer software) and clinical (clinical interpretation of radiographs) definitions of malunion were compared within the Ankle Injury Management (AIM) trial cohort, including people aged ≥ 60 years with an unstable ankle fracture. Linear regressions were used to explore the relationship between radiological malunion (RM) at six months and changes in function at three years. Function was assessed with the Olerud-Molander Ankle Score (OMAS), with a minimal clinically important difference set as six points, as per the AIM trial. Piecewise linear models were used to investigate new radiological thresholds which better explain symptom impact on ankle function. Results. Previously described measures of RM and surgeon opinion of clinically significant malunion (CSM) were shown to be related but with important differences. CSM was more strongly related to outcome (-13.9 points on the OMAS; 95% confidence interval (CI) -21.9 to -5.4) than RM (-5.5 points; 95% CI -9.8 to -1.2). Existing malunion thresholds for talar tilt and tibiofibular clear space were shown to be slightly conservative; new thresholds which better explain function were identified (talar tilt > 2.4°; tibiofibular clear space > 6 mm). Based on this new definition the presence of RM had an impact on function, which was statistically significant, but the clinical significance was uncertain (-9.1 points; 95% CI -13.8 to -4.4). In subsequent analysis, RM of a posterior malleolar fracture was shown to have a statistically significant impact on OMAS change scores, but the clinical significance was uncertain (-11.6 points; 95% CI -21.9 to -0.6). Conclusion. These results provide clinical evidence which supports the previously accepted definitions. Further research to investigate more conservative clinical thresholds for malunion is indicated. Cite this article: Bone Jt Open 2022;3(10):841–849

Aims. The purpose of this study was to assess the prevalence of depression and anxiety symptoms in patients undergoing shoulder surgery using the National Institutes of Health (NIH) Patient-Reported Outcomes Measurement Information System (PROMIS) Depression and Anxiety computer adaptive tests, and to determine the factors associated with more severe symptoms. Additionally, we sought to determine whether PROMIS Depression and Anxiety were associated with functional outcomes after shoulder surgery. Methods. This was a retrospective analysis of 293 patients from an urban population who underwent elective shoulder surgery from 2015 to 2018. Survey questionnaires included preoperative and two-year postoperative data. Bivariate analysis was used to identify associations and multivariable analysis was used to control for confounding variables. Results. Mean two-year PROMIS Depression and Anxiety scores significantly improved from preoperative scores, with a greater improvement observed in PROMIS Anxiety. Worse PROMIS Depression and Anxiety scores were also significantly correlated with worse PROMIS Physical Function (PF) and American Shoulder and Elbow Surgeons scores (ASES). After controlling for confounding variables, worse PROMIS Depression was an independent predictor of worse PROMIS PF, while worse PROMIS Anxiety was an independent predictor of worse PROMIS PF and ASES scores. Conclusion. Mean two-year PROMIS Depression and Anxiety scores improved after elective shoulder surgery and several patient characteristics were associated with these scores. Worse functional outcomes were associated with worse PROMIS Depression and Anxiety; however, more severe two-year PROMIS Anxiety was the strongest predictor of worse functional outcomes. Cite this article: Bone Joint J 2022;104-B(4):479–485

Dislocation following total hip arthroplasty (THA) is a well-known and potentially devastating complication. Clinicians have used many strategies in attempts to prevent dislocation since the introduction of THA. While the importance of postoperative care cannot be ignored, particular emphasis has been placed on preoperative planning in the prevention of dislocation. The strategies have progressed from more traditional approaches, including modular implants, the size of the femoral head, and augmentation of the offset, to newer concepts, including patient-specific component positioning combined with computer navigation, robotics, and the use of dual-mobility implants. As clinicians continue to pursue improved outcomes and reduced complications, these concepts will lay the foundation for future innovation in THA and ultimately improved outcomes. Cite this article: Bone Joint J 2022;104-B(1):8–11

The kinematic alignment (KA) approach to total knee arthroplasty (TKA) has recently increased in popularity. Accordingly, a number of derivatives have arisen and have caused confusion. Clarification is therefore needed for a better understanding of KA-TKA. Calipered (or true, pure) KA is performed by cutting the bone parallel to the articular surface, compensating for cartilage wear. In soft-tissue respecting KA, the tibial cutting surface is decided parallel to the femoral cutting surface (or trial component) with in-line traction. These approaches are categorized as unrestricted KA because there is no consideration of leg alignment or component orientation. Restricted KA is an approach where the periarthritic joint surface is replicated within a safe range, due to concerns about extreme alignments that have been considered ‘alignment outliers’ in the neutral mechanical alignment approach. More recently, functional alignment and inverse kinematic alignment have been advocated, where bone cuts are made following intraoperative planning, using intraoperative measurements acquired with computer assistance to fulfill good coordination of soft-tissue balance and alignment. The KA-TKA approach aims to restore the patients’ own harmony of three knee elements (morphology, soft-tissue balance, and alignment) and eventually the patients’ own kinematics. The respective approaches start from different points corresponding to one of the elements, yet each aim for the same goal, although the existing implants and techniques have not yet perfectly fulfilled that goal

Aims. The Patient-Reported Outcomes Measurement Information System (PROMIS) has demonstrated faster administration, lower burden of data capture and reduced floor and ceiling effects compared to traditional Patient Reported Outcomes Measurements (PROMs). We investigated the suitability of PROMIS Mobility score in assessing physical function in the sequelae of childhood hip disease. Methods. In all, 266 adolscents (aged ≥ 12 years) and adults were identified with a prior diagnosis of childhood hip disease (either Perthes’ disease (n = 232 (87.2%)) or Slipped Capital Femoral Epiphysis (n = 34 (12.8%)) with a mean age of 27.73 years (SD 12.24). Participants completed the PROMIS Mobility Computer Adaptive Test, the Non-Arthritic Hip Score (NAHS), EuroQol five-dimension five-level questionnaire, and the Numeric Pain Rating Scale. We investigated the correlation between the PROMIS Mobility and other tools to assess use in this population and any clustering of outcome scores. Results. There was a strong correlation between the PROMIS Mobility and other established PROMs; NAHS (rs = 0.79; p < 0.001). There was notable clustering in PROMIS at the upper end of the distribution score (42.5%), with less seen in the NAHS (20.3%). However, the clustering was broadly similar between PROMIS Mobility and the comparable domains of the NAHS; function (53.6%), and activity (35.0%). Conclusion. PROMIS Mobility strongly correlated with other tools demonstrating convergent construct validity. There was clustering of physical function scores at the upper end of the distributions, which may reflect truncation of the data caused by participants having excellent outcomes. There were elements of disease not captured within PROMIS Mobility alone, and difficulties in differentiating those with the highest levels of function. Cite this article: Bone Jt Open 2021;2(12):1089–1095

Objectives. To date, no study has considered the impact of acromial morphology on shoulder range of movement (ROM). The purpose of our study was to evaluate the effects of lateralization of the centre of rotation (COR) and neck-shaft angle (NSA) on shoulder ROM after reverse shoulder arthroplasty (RSA) in patients with different scapular morphologies. Methods. 3D computer models were constructed from CT scans of 12 patients with a critical shoulder angle (CSA) of 25°, 30°, 35°, and 40°. For each model, shoulder ROM was evaluated at a NSA of 135° and 145°, and lateralization of 0 mm, 5 mm, and 10 mm for seven standardized movements: glenohumeral abduction, adduction, forward flexion, extension, internal rotation with the arm at 90° of abduction, as well as external rotation with the arm at 10° and 90° of abduction. Results. CSA did not seem to influence ROM in any of the models, but greater lateralization achieved greater ROM for all movements in all configurations. Internal and external rotation at 90° of abduction were impossible in most configurations, except in models with a CSA of 25°. Conclusion. Postoperative ROM following RSA depends on multiple patient and surgical factors. This study, based on computer simulation, suggests that CSA has no influence on ROM after RSA, while lateralization increases ROM in all configurations. Furthermore, increasing subacromial space is important to grant sufficient rotation at 90° of abduction. In summary, increased lateralization of the COR and increased subacromial space improve ROM in all CSA configurations. Cite this article: A. Lädermann, E. Tay, P. Collin, S. Piotton, C-H Chiu, A. Michelet, C. Charbonnier. Effect of critical shoulder angle, glenoid lateralization, and humeral inclination on range of movement in reverse shoulder arthroplasty. Bone Joint Res 2019;8:378–386. DOI: 10.1302/2046-3758.88.BJR-2018-0293.R1

Aims. Patient-reported outcome measures have become an important part of routine care. The aim of this study was to determine if Patient-Reported Outcomes Measurement Information System (PROMIS) measures can be used to create patient subgroups for individuals seeking orthopaedic care. Methods. This was a cross-sectional study of patients from Duke University Department of Orthopaedic Surgery clinics (14 ambulatory and four hospital-based). There were two separate cohorts recruited by convenience sampling (i.e. patients were included in the analysis only if they completed PROMIS measures during a new patient visit). Cohort #1 (n = 12,141; December 2017 to December 2018,) included PROMIS short forms for eight domains (Physical Function, Pain Interference, Pain Intensity, Depression, Anxiety, Sleep Quality, Participation in Social Roles, and Fatigue) and Cohort #2 (n = 4,638; January 2019 to August 2019) included PROMIS Computer Adaptive Testing instruments for four domains (Physical Function, Pain Interference, Depression, and Sleep Quality). Cluster analysis (K-means method) empirically derived subgroups and subgroup differences in clinical and sociodemographic factors were identified with one-way analysis of variance. Results. Cluster analysis yielded four subgroups with similar clinical characteristics in Cohort #1 and #2. The subgroups were: 1) Normal Function: within normal limits in Physical Function, Pain Interference, Depression, and Sleep Quality; 2) Mild Impairment: mild deficits in Physical Function, Pain Interference, and Sleep Quality but with Depression within normal limits; 3) Impaired Function, Not Distressed: moderate deficits in Physical Function and Pain Interference, but within normal limits for Depression and Sleep Quality; and 4) Impaired Function, Distressed: moderate (Physical Function, Pain Interference, and Sleep Quality) and mild (Depression) deficits. Conclusion. These findings suggest orthopaedic patient subgroups differing in physical function, pain, and psychosocial distress can be created from as few as four different PROMIS measures. Longitudinal research is necessary to determine whether these subgroups have prognostic validity. Cite this article: Bone Jt Open 2021;2(7):493–502

Aims. This study aims to investigate the effects of posterior tibial slope (PTS) on knee kinematics involved in the post-cam mechanism in bi-cruciate stabilized (BCS) total knee arthroplasty (TKA) using computer simulation. Methods. In total, 11 different PTS (0° to 10°) values were simulated to evaluate the effect of PTS on anterior post-cam contact conditions and knee kinematics in BCS TKA during weight-bearing stair climbing (from 86° to 6° of knee flexion). Knee kinematics were expressed as the lowest points of the medial and lateral femoral condyles on the surface of the tibial insert, and the anteroposterior translation of the femoral component relative to the tibial insert. Results. Anterior post-cam contact in BCS TKA was observed with the knee near full extension if PTS was 6° or more. BCS TKA showed a bicondylar roll forward movement from 86° to mid-flexion, and two different patterns from mid-flexion to knee extension: screw home movement without anterior post-cam contact and bicondylar roll forward movement after anterior post-cam contact. Knee kinematics in the simulation showed similar trends to the clinical in vivo data and were almost within the range of inter-specimen variability. Conclusion. Postoperative knee kinematics in BCS TKA differed according to PTS and anterior post-cam contact; in particular, anterior post-cam contact changed knee kinematics, which may affect the patient’s perception of the knee during activities. Cite this article: Bone Joint Res 2020;9(11):761–767

Aims. The extensive variation in axial rotation of tibial components can lead to coronal plane malalignment. We analyzed the change in coronal alignment induced by tray malrotation. Methods. We constructed a computer model of knee arthroplasty and used a virtual cutting guide to cut the tibia at 90° to the coronal plane. The virtual guide was rotated axially (15° medial to 15° lateral) and with posterior slopes (0° to 7°). To assess the effect of axial malrotation, we measured the coronal plane alignment of a tibial tray that was axially rotated (25° internal to 15° external), as viewed on a standard anteroposterior (AP) radiograph. Results. Axial rotation of the cutting guide induced a varus-valgus malalignment up to 1.8° (for 15° of axial rotation combined with 7° of posterior slope). Axial malrotation of tibial tray induced a substantially higher risk of coronal plane malalignment ranging from 1.9° valgus with 15° external rotation, to over 3° varus with 25° of internal rotation. Coronal alignment of the tibial cut changed by 0.07° per degree of axial rotation and 0.22° per degree of posterior slope (linear regression, R. 2. > 0.99). Conclusion. While the effect of axial malalignment has been studied, the impact on coronal alignment is not known. Our results indicate that the direction of the cutting guide and malalignment in axial rotation alter coronal plane alignment and can increase the incidence of outliers. Cite this article: Bone Joint J 2020;102-B(6 Supple A):43–48

We report our experience of using a computer navigation system to aid resection of malignant musculoskeletal tumours of the pelvis and limbs and, where appropriate, their subsequent reconstruction. We also highlight circumstances in which navigation should be used with caution. We resected a musculoskeletal tumour from 18 patients (15 male, three female, mean age of 30 years (13 to 75) using commercially available computer navigation software (Orthomap 3D) and assessed its impact on the accuracy of our surgery. Of nine pelvic tumours, three had a biological reconstruction with extracorporeal irradiation, four underwent endoprosthetic replacement (EPR) and two required no bony reconstruction. There were eight tumours of the bones of the limbs. Four diaphyseal tumours underwent biological reconstruction. Two patients with a sarcoma of the proximal femur and two with a sarcoma of the proximal humerus underwent extra-articular resection and, where appropriate, EPR. One soft-tissue sarcoma of the adductor compartment which involved the femur was resected and reconstructed using an EPR. Computer navigation was used to aid reconstruction in eight patients. Histological examination of the resected specimens revealed tumour-free margins in all patients. Post-operative radiographs and CT showed that the resection and reconstruction had been carried out as planned in all patients where navigation was used. In two patients, computer navigation had to be abandoned and the operation was completed under CT and radiological control. The use of computer navigation in musculoskeletal oncology allows accurate identification of the local anatomy and can define the extent of the tumour and proposed resection margins. Furthermore, it helps in reconstruction of limb length, rotation and overall alignment after resection of an appendicular tumour. . Cite this article: Bone Joint J 2015;97-B:258–64

Dissatisfaction following total knee arthroplasty is a well-documented phenomenon. Although many factors have been implicated, including modifiable and nonmodifiable patient factors, emphasis over the past decade has been on implant alignment and stability as both a cause of, and a solution to, this problem. Several alignment targets have evolved with a proliferation of techniques following the introduction of computer and robotic-assisted surgery. Mechanical alignment targets may achieve mechanically-sound alignment while ignoring the soft tissue envelope; kinematic alignment respects the soft tissue envelope while ignoring the mechanical environment. Functional alignment is proposed as a hybrid technique to allow mechanically-sound, soft tissue-friendly alignment targets to be identified and achieved. Cite this article: Bone Joint J 2020;102-B(3):276–279

Aims. The coronavirus disease (COVID)-19 pandemic forced an unprecedented period of challenge to the NHS in the UK where hip fractures in the elderly population are a major public health concern. There are approximately 76,000 hip fractures in the UK each year which make up a substantial proportion of the trauma workload of an average orthopaedic unit. This study aims to assess the impact of the COVID-19 pandemic on hip fracture care service and the emerging lessons to withstand any future outbreaks. Methods. Data were collected retrospectively on 157 hip fractures admitted from March to May 2019 and 2020. The 2020 group was further subdivided into COVID-positive and COVID-negative. Data including the four-hour target, timing to imaging, hours to operation, anaesthetic and operative details, intraoperative complications, postoperative reviews, COVID status, Key Performance Indicators (KPIs), length of stay, postoperative complications, and the 30-day mortality were compiled from computer records and our local National Hip Fracture Database (NHFD) export data. Results. Hip fractures and inpatient falls significantly increased by 61.7% and 7.2% respectively in the 2020 group. A significant difference was found among the three groups regarding anaesthetic preparation time, anaesthetic time, and recovery time. The mortality rate in the 2020 COVID-positive group (36.8%) was significantly higher than both the 2020 COVID-negative and 2019 groups (11.5% and 11.7% respectively). The hospital stay was significantly higher in the COVID-positive group (mean of 24.21 days (SD 19.29)). Conclusion. COVID-19 has had notable effects on the hip fracture care service: hip fracture rates increased significantly. There were inefficiencies in theatre processes for which we have recommended the use of alternate theatres. COVID-19 infection increased the 30-day mortality and hospital stay in hip fractures. More research needs to be done to reduce this risk. Cite this article: Bone Joint Open 2020;1-9:530–540

The use of artificial intelligence (AI) is rapidly growing across many domains, of which the medical field is no exception. AI is an umbrella term defining the practical application of algorithms to generate useful output, without the need of human cognition. Owing to the expanding volume of patient information collected, known as ‘big data’, AI is showing promise as a useful tool in healthcare research and across all aspects of patient care pathways. Practical applications in orthopaedic surgery include: diagnostics, such as fracture recognition and tumour detection; predictive models of clinical and patient-reported outcome measures, such as calculating mortality rates and length of hospital stay; and real-time rehabilitation monitoring and surgical training. However, clinicians should remain cognizant of AI’s limitations, as the development of robust reporting and validation frameworks is of paramount importance to prevent avoidable errors and biases. The aim of this review article is to provide a comprehensive understanding of AI and its subfields, as well as to delineate its existing clinical applications in trauma and orthopaedic surgery. Furthermore, this narrative review expands upon the limitations of AI and future direction.

Cite this article: Bone Joint Res 2023;12(7):447–454.

Objectives. Unicompartmental knee arthroplasty (UKA) is one surgical option for treating symptomatic medial osteoarthritis. Clinical studies have shown the functional benefits of UKA; however, the optimal alignment of the tibial component is still debated. The purpose of this study was to evaluate the effects of tibial coronal and sagittal plane alignment in UKA on knee kinematics and cruciate ligament tension, using a musculoskeletal computer simulation. Methods. The tibial component was first aligned perpendicular to the mechanical axis of the tibia, with a 7° posterior slope (basic model). Subsequently, coronal and sagittal plane alignments were changed in a simulation programme. Kinematics and cruciate ligament tensions were simulated during weight-bearing deep knee bend and gait motions. Translation was defined as the distance between the most medial and the most lateral femoral positions throughout the cycle. Results. The femur was positioned more medially relative to the tibia, with increasing varus alignment of the tibial component. Medial/lateral (ML) translation was smallest in the 2° varus model. A greater posterior slope posteriorized the medial condyle and increased anterior cruciate ligament (ACL) tension. ML translation was increased in the > 7° posterior slope model and the 0° model. Conclusion. The current study suggests that the preferred tibial component alignment is between neutral and 2° varus in the coronal plane, and between 3° and 7° posterior slope in the sagittal plane. Varus > 4° or valgus alignment and excessive posterior slope caused excessive ML translation, which could be related to feelings of instability and could potentially have negative effects on clinical outcomes and implant durability. Cite this article: K. Sekiguchi, S. Nakamura, S. Kuriyama, K. Nishitani, H. Ito, Y. Tanaka, M. Watanabe, S. Matsuda. Bone Joint Res 2019;8:126–135. DOI: 10.1302/2046-3758.83.BJR-2018-0208.R2

Cite this article: Bone Joint Res 2023;12(8):494–496.