Aims. The aim of this study was to explore why some calcar screws are malpositioned when a proximal humeral fracture is treated by internal fixation with a locking plate, and to identify risk factors for this phenomenon. Some suggestions can be made of ways to avoid this error. Methods. We retrospectively identified all proximal humeral fractures treated in our institution between October 2016 and October 2018 using the hospital information system. The patients’ medical and radiological data were collected, and we divided potential risk factors into two groups: preoperative factors and intraoperative factors. Preoperative factors included age, sex, height, weight, body mass index, proximal humeral bone mineral density, type of fracture, the condition of the medial hinge, and medial metaphyseal head extension. Intraoperative factors included the grade of surgeon, neck-shaft angle after reduction, humeral head height, restoration of medial support, and quality of reduction. Adjusted binary logistic regression and multivariate logistic regression models were used to identify pre- and intraoperative risk factors. Area under the curve (AUC) analysis was used to evaluate the discriminative ability of the multivariable model. Results. Data from 203 patients (63 males and 140 females) with a mean age of 62 years (22 to 89) were analyzed. In 49 fractures, the calcar screw was considered to be malpositioned; in 154 it was in the optimal position. The rate of malpositioning was therefore 24% (49/203). No preoperative risk factor was found for malpositioning of the calcar screws. Only the neck-shaft angle was found to be related to the risk of screw malpositioning in a multivariate model (with an AUC of 0.72). For the fractures in which the neck-shaft angle was reduced to between 130° and 150°, 91% (133/46) of calcar screws were in the optimal position. Conclusion. The neck-shaft angle is the key factor for the appropriate positioning of calcar screws when treating a proximal humeral fracture with a locking plate. We recommend reducing the angle to between 130° and 150°. Cite this article: Bone Joint J 2020;102-B(12):1629–1635

Purpose of the study: The extramedullary anatomy of the femur must be reproduced during total hip arthroplasty in order to ensure correct tension on the gluteus muscles. This requires:. correct offset of the femur, measured as the distance between the center of the head and the anatomic axis of the shaft;. offset of the center of rotation, measured as the distance between the center of the head and the pubic symphesis. Addition of these two offsets gives the overall offset. The purpose of this work was to analyze postoperative offset after standard total hip arthroplasty as a function of the preoperative head-shaft angle. Material and methods: Prospective study of 150 files of patients who underwent first-intention total hip arthroplasty. A prosthesis with matched increasing head size was implanted. The head-shaft angle was 135°. Mean offset was 41.7 mm (range 33–47 mm) for the 0 head-neck. The preoperative neck-shaft angle was measured on the upright ap view (comparable rotation of the two hemipelvi). Pre- and postoperative femur and center of rotation offset were noted. Results: The preoperative neck-shaft angle varied from 118° to 1400. Mean preoperative femur offset was 40.2 mm (range 29–52 mm). Mean postoperative femur offset was 42.2 mm. This gave a 2 mm lateralization of the femur, which was apparently negligible, favorable, and therefore satisfactory. Mean offset was 90.5 mm preoperatively and 84.5 mm postoperatively, medializing the center of rotation 6°. Mean overall offset was thus displaced medially (6 mm minus 2 mm = 4 mm). This was considered acceptable. Among these 150 files, 24 were coxa vara hips with a neck-shaft angle 125°. For these 25 coxavara hips, the mean preoperative femur offset was 44.5 mm. The mean postoperative femur offset was 42.2 mm. This produced, inversely, a medial displacement of the postoperative femur offset of 2.3 mm. The center of rotation was displace medially 6 mm. Thus globally the medial displacement was 6 mm plus 2.3 mm = 8.3 mm. This appeared to be excessive. Discussion: The postoperative offset of the femur is prosthesis-dependent. The majority of implants currently marketed have a mean offset in the 40–45mm range. The offset of the center of rotation is operator-dependent: as the acetabular reaming is accentuated, the center of rotation is displaced medially. Acetabular reaming is necessary to reach the subchondral bone. The medial offset can be limited but at least some displacement is inevitable. Thus in the event of a coxavara hip, it is very difficult to limit excessive overall medial offset when using a standard prosthesis. If the goal is to mimic the anatomic femur offset, it would appear justified to use prostheses with a smaller neck-shaft angle for patients with coxavara. A 10° reduction, from 135° to 125° would increase the femur offset 5 mm and thus enable reproduction of the preoperative anatomy

Impingement of total hip replacements (THRs) can cause rim damage of polyethylene liners, and lead to dislocation and/or mechanical failure of liner locking mechanisms[1]. Previous work has focussed on the influence of femoral neck profile on impingement without consideration of neck-shaft angle. This study assessed the occurrence of impingement with two different stem designs (Corail standard [135°] and coxa vara [125°]) under different activities with varying acetabular cup orientation (30° to 70° inclination; 0° to 50° anteversion) using a geometric modelling tool. The tool was created in a computer aided design software programme, and incorporated an individual's hemi-pelvis and femur geometry[3] with a THR (DePuy Synthes Pinnacle. ®. shell and neutral liner; size 12 Corail. ®. standard or coxa vara and 32mm head). Kinematic data of activities associated with dislocation[2], such as stooping to pick an object from the floor was applied and incidences of impingement were recorded. Predicted implant impingement was influenced by stem design. The coxa vara stem was predicted to cause implant impingement less frequently across the range of activities and cup orientations investigated, compared to the standard stem [Fig. 1]. The cup orientations predicted to cause impingement the least frequently were at lower inclination and anteversion angles, relative to the standard stem [Fig. 1]. The coxa vara stem included a collar, while the standard stem was collarless; additional analysis indicated that differences were due to neck angle and not the presence of a collar. This study demonstrated that stem neck-shaft angle is an important variable in prosthetic impingement in THR and surgeons should be aware of this when choosing implants. Future work will consider further implant design and bone geometry variables. This tool has the potential for use in optimising stem design and position and could assist with patient specific stem selection based on an individual's activity profile. For any figures or tables, please contact the authors directly

Hip resurfacing arthroplasty (HRA) in patients with a varus deformity of the femoral neck-shaft angle (NSA) has been cited in the literature as contributory factor towards a poorer outcome. Our experience has not reflected this. We examined the outcomes of patients with varus hips against a normal cohort. Measurement of the femoral neck-shaft angle was undertaken from standard antero-posterior radiographs pre-operatively. The mean NSA was 128.5 degrees (SD 6.3). Patients less than 122.2 were deemed varus and those above 134.8 valgus. These parameters were consistent with the published literature. The varus cohort consisted of 23 patients, mean NSA 118.7 (range 113.6-121.5), mean follow-up 49 months (range 13-74), mean OHS & HHS, 16 & 93.5 respectively. Complications included 2 cases of trochanteric non-union; no femoral neck fractures or revisions. The normal cohort consisted of 125 patients, mean NSA 128 degrees, mean follow-up 41 months (range 6-76), mean OHS & HSS, 18.8 & 88.9 respectively. Complications included 5 cases of trochanteric non-union and 1 revision. Statistical analysis demonstrated no difference between the cohorts OHS (p=0.583) or HHS (p=0.139). Our experience in patients with a varus femoral neck has been positive. Our analysis has demonstrated no difference in outcomes between the cohorts

Hip resurfacing arthroplasty (HRA) in patients with a varus deformity of the femoral neck-shaft angle (NSA) is associated with poorer outcomes. Our experience has not reflected this. We examined the Oxford Hip Scores (OHS), Harris Hip Scores (HHS) and outcomes of patients with varus hips against a normal cohort to ascertain any significant difference. We identified 179 patients. Measurement of the femoral neck-shaft angle was undertaken from antero-posterior radiographs pre-operatively. The mean NSA was 128.5 degrees (SD 6.3). Patients with a NSA of less than 122.2 were deemed varus and those above 134.8 valgus. These parameters were consistent with published anatomical studies. The varus cohort consisted of 23 patients, mean NSA 118.7 (range 113.6-121.5), mean follow-up 49 months (range 13-74). Mean OHS and HHS were 16 and 93.5 respectively. Complications included 2 cases of trochanteric non-union; no femoral neck fractures, early failures or revisions. Normal cohort consisted of 125 patients, mean NSA 128 degrees, mean follow-up 41 months (range 6-76). The OHS and HSS were 18.8, 88.9 respectively. Complications included 5 trochanteric non-unions and 1 revision due to an acetabular fracture following a fall. Statistical analysis demonstrated no statistical difference between the cohorts OHS (p=0.583) or HHS (p=0.139). Our experience in patients with a varus femoral neck has been positive. Our analysis has demonstrated no statistical difference in hip scores between the cohorts. We have not yet experienced any femoral neck fractures, which we believe is due to the use of the Ganz trochanteric flip and preservation of blood supply

Optimal entry point for antegrade femoral intramedullary nailing (IMN) remains controversial in the current medical literature. The definition of an ideal entry point for femoral IMN would implicate a tenseless introduction of the implant into the canal with anatomical alignment of the bone fragments. This study was undertaken in order to investigate possible existing relationships between the true 3D geometric parameters of the femur and the location of the optimum entry point. A sample population of 22 cadaveric femurs was used. Computed-tomography sections every 0.5 mm for the entire length of femurs were produced. These sections were subsequently reconstructed to generate solid computer models of the external anatomy and medullary canal of each femur. Solid models of all femurs were subjected to a series of geometrical manipulations and computations using standard computer-aided-design tools. In the sagittal plane, the optimum entry point always lied a few millimeters behind the femoral neck axis (mean=3.5±1.5 mm). In the coronal plane the optimum entry point lied at a location dependent on the femoral neck-shaft angle. Linear regression on the data showed that the optimal entry point is clearly correlated to the true 3D femoral neck-shaft angle (R2=0.7310) and the projected femoral neck-shaft angle (R2=0.6289). Anatomical parameters of the proximal femur, such as the varus-valgus angulation, are key factors in the determination of optimal entry point for nailing. The clinical relevance of the results is that in varus hips (neck-shaft angle • 120o) the correct entry point should be positioned over the trochanter tip and the use stiff nails is advised. In cases of hips with neck-shaft angle between 120o and 130o, the optimal entry point lies just medially to the trochanter tip (at the piriformis fossa) and the use of stiff implants is safe. In hips with neck-shaft angle over 130o the anatomical axis of the canal is medially to the base of the neck, in a “restricted area”. In these cases the entry point should be located at the insertion of the piriformis muscle and the application of more malleable implants that could easily follow the medullary canal should be considered

Introduction. Reverse total shoulder arthroplasty (RTSA) can partially restore lost range of motion (ROM). Active motion restoration is largely a function of RTSA joint constraint, limiting impingement, and muscle recruitment; however, it may also be a function of implant design. The aim of this computational study was to examine the effects of implant design parameters, such as neck-shaft (N-S) angle and glenoid lateralization, on impingement-free global circumduction range of motion (GC-ROM). GC-ROM summarizes the characteristically complex, wide-ranging envelope of glenohumeral motion into a single quantity for ease of comparison. Methods. Nine computational models were used to investigate implant parameters. The parameters examined were N-S angles of 135°, 145°, and 155° in combination with glenoid lateralizations (0, 5, and 10 mm). Static positioning of the humerus was defined by an elevation direction angle, elevation angle, and rotation. The humerus was rotated from the neutral position (0° of rotation and elevation), and then elevated in different elevation directions until impingement was detected. Abduction occurred at an elevation direction angle of 0°, while flexion and extension occurred at elevation direction angles of 90° and −90°, respectively. Elevation direction angles ranged from −180° to 180°. Elevation ranged from 0° and 180°. Rotations ranged from −45° to 90°, where negative and positive rotations represented external and internal rotation, respectively. For each rotation angle, a plot of maximum elevation in each elevation plane was created using polar coordinates (radius = elevation, angle = elevation direction). The area enclosed by the resulting points, normalized with respect to the implant with a 145° N-S angle and 5 mm lateralization, was calculated. The sum of these areas defined the GC-ROM. Results. Figure 1 depicts the maximum ROM curves at each angle of rotation for a 145° N-S angle humeral implant with 5 mm of glenoid lateralization. Table 1 shows the normalized areas within the maximum ROM curves for each implant configuration at each angle of rotation, where 0% indicates that the corresponding angle of rotation could not be achieved without impingement. The effect of varying N-S angle (constant lateralization of 5 mm) and lateralization (constant N-S angle of 145°) is shown for 0° rotation (Figures 2A and 2B, respectively). Conclusions. In general, increasing glenoid lateralization increases GC-ROM; however, the unintuitive poor performance of all 10 mm lateralized configurations at rotations of −90° highlights the complex relationships between implant parameters and ROM. Interestingly, the 135° N-S implant had greater flexion and extension ROM, while the 155° N-S implant had greater abduction ROM, suggesting that there are trade-offs between N-S angles pertaining to the elevation direction in which maximum elevation is obtained. The results of this study highlight the need to incorporate multi-directional motion when assessing the effect of varying implant parameters on the impingement-free GC-ROM. Future studies will include the application of the presented technique to a broader range of implant and surgical parameters

Atypical femoral fracture non-union (AFFNU) is both, rare (3–5 per 1000 proximal femur fractures) and difficult to treat. Lack of standardised guidelines leads to a variability in fixation constructs, use of bone grafting and restricted weight bearing protocols, which are not evidence based. We hypothesised that there is no change in union rates without the use of bone grafting and immediate weight bearing post-operatively does not lead to increased complications. Materials & Methods. A retrospective review of all consecutively treated AFFNU cases between March 2015 to December 2019 was carried out. 9 patients with a mean age of 63.87 years and M:F ratio of 7:2 met the inclusion criteria. Primary outcome variable was radiographic union at 12 months after revision surgery. All surgeries were carried out by a single surgeon. Fixation construct, neck-shaft angle, use of bone graft and immediate postoperative weight bearing protocols were recorded. Results. Radiographic union was achieved in 7 of 9 patients (78%) after first revision surgery. 1 patient achieved union after 2nd revision surgery and 1 patient died in the early post-operative period due to pulmonary embolism. No bone grafting was used in any of the patients and weight-bearing as tolerated was allowed from the first post-operative day. The mean neck-shaft angle after non-union surgery was 136 degrees. Conclusions. In this case series, the union rate was comparable to those reported in literature previously and achieved without any form of bone grafting. To our knowledge, this is the only case series where no bone grafting was used in the management of AFFNU. Limited by a small sample size and retrospective study design, still, this study brings into question the efficacy of practice of bone grafting and restricted weight-bearing in the management of AFFNU. Bone grafting is associated with the risk of infection at donor site, postoperative pain, and morbidity, while early weight bearing is critical in elderly patients. There is no evidence supporting restricted weight-bearing and it should not be adopted as the default practice as it may even be detrimental to patients

Aims. To evaluate how abnormal proximal femoral anatomy affects different femoral version measurements in young patients with hip pain. Methods. First, femoral version was measured in 50 hips of symptomatic consecutively selected patients with hip pain (mean age 20 years (SD 6), 60% (n = 25) females) on preoperative CT scans using different measurement methods: Lee et al, Reikerås et al, Tomczak et al, and Murphy et al. Neck-shaft angle (NSA) and α angle were measured on coronal and radial CT images. Second, CT scans from three patients with femoral retroversion, normal femoral version, and anteversion were used to create 3D femur models, which were manipulated to generate models with different NSAs and different cam lesions, resulting in eight models per patient. Femoral version measurements were repeated on manipulated femora. Results. Comparing the different measurement methods for femoral version resulted in a maximum mean difference of 18° (95% CI 16 to 20) between the most proximal (Lee et al) and most distal (Murphy et al) methods. Higher differences in proximal and distal femoral version measurement techniques were seen in femora with greater femoral version (r > 0.46; p < 0.001) and greater NSA (r > 0.37; p = 0.008) between all measurement methods. In the parametric 3D manipulation analysis, differences in femoral version increased 11° and 9° in patients with high and normal femoral version, respectively, with increasing NSA (110° to 150°). Conclusion. Measurement of femoral version angles differ depending on the method used to almost 20°, which is in the range of the aimed surgical correction in derotational femoral osteotomy and thus can be considered clinically relevant. Differences between proximal and distal measurement methods further increase by increasing femoral version and NSA. Measurement methods that take the entire proximal femur into account by using distal landmarks may produce more sensitive measurements of these differences. Cite this article: Bone Jt Open 2022;3(10):759–766

Aims. Hip displacement, common in patients with cerebral palsy (CP), causes pain and hinders adequate care. Hip reconstructive surgery (HRS) is performed to treat hip displacement; however, only a few studies have quantitatively assessed femoral head sphericity after HRS. The aim of this study was to quantitatively assess improvement in hip sphericity after HRS in patients with CP. Methods. We retrospectively analyzed hip radiographs of patients who had undergone HRS because of CP-associated hip displacement. The pre- and postoperative migration percentage (MP), femoral neck-shaft angle (NSA), and sphericity, as determined by the Mose hip ratio (MHR), age at surgery, Gross Motor Function Classification System level, surgical history including Dega pelvic osteotomy, and triradiate cartilage status were studied. Regression analyses using linear mixed model were performed to identify factors affecting hip sphericity improvement. Results. A total of 108 patients were enrolled. The mean preoperative MP was 58.3% (SD 31.7%), which improved to 9.1% (SD 15.6%) at the last follow-up. NSA and MHR improved from 156.5° (SD 11.5°) and 82.3% (SD 8.6%) to 126.0° (SD 18.5°) and 89.1% (SD 9.0%), respectively. Factors affecting the postoperative MHR were preoperative MP (p = 0.005), immediate postoperative MP (p = 0.032), and history of Dega osteotomy (p = 0.046). Conclusion. We found that hip sphericity improves with HRS. Preoperative MP, reduction quality, and acetabular coverage influence femoral head remodelling. We recommend that surgeons should consider intervention early before hip displacement progresses and that during HRS, definite reduction and coverage of the femoral head should be obtained. Cite this article: Bone Joint J 2021;103-B(1):198–203

Objective. To three-dimensionally reconstruct the proximal femur of DDH (Developmental dysplasia of the hip) and measure the related anatomic parameters, so that we could have a further understanding of the morphological variation of the proximal femur of DDH, which would help in the preoperative planning and prosthesis design specific for DDH. Methods. From Jan.2012 to Dec.2014, 38 patients (47 hips) of DDH were admitted and 30 volunteers (30 hips) were selected as controls. All hips from both groups were examined by CT scan and radiographs. The Crowe classification method was applied. The CT data were imported into Mimics 17.0. The three-dimensional models of the proximal femur were then reconstructed, and the following parameters were measured: neck-shaft angle, neck length, offset, height of the centre of femoral head, height of the isthmus, height of greater trochanter, the medullary canal diameter of isthmus(Di), the medullary canal diameter 10mm above the apex of the lesser trochanter(DT+10), the medullary canal diameter 20mm below the apex of the lesser trochanter(DT-20), and then DT+10/Di, DT-20/Di and DT+10/DT-20 were calculated. Results. There is no significant difference in neck-shaft angle between Crowe I-III DDH and the control group, while the neck-shaft angle is much smaller in Crowe IV DDH. The neck length of Crowe IV DDH is much smaller than those of Crowe I-III DDH. As for Di there is neither significant difference between Crowe I DDH and the control group, nor significant difference between CroweII-III and Crowe IV, but the difference is significant between the first two groups and the latter two groups. DT+10/DT-20 and the offset have no significant difference between the control group and DDH groups. DT-20, DT+10, DT+10/Di and DT-20/Di are much smaller in Crowe IV DDH than that in Crowe I-III and the control groups. Height of greater trochanter in Crowe IV is larger than those in Crowe I-III and the control group. Height of the centre of femoral head in Crowe IV DDH is smaller than those in Crowe I-III DDH and the control group. The height of the isthmus in Crowe IV is much smaller than those in Crowe I-III DDH and the control group. Conclusion. The neck-shaft angle in DDH groups is not larger than that in the control group, while in contrast, it's much smaller in Crowe IV DDH than that in the control group. Comparing to Crowe I-III DDH and the control group, Crowe IV DDH has a dramatic change in the intramedullary and extramedullary parameters. The isthmus and the great trochanter are higher and there is apparent narrowing of the medullary canal around the level of the lesser trochanter

With the growing number of individuals with asymptomatic cam-type deformities, elevated alpha angles alone do not always explain clinical signs of femoroacetabular impingement (FAI). Differences in additional anatomical parameters may affect hip joint mechanics, altering the pathomechanical process resulting in symptomatic FAI. The purpose was to examine the association between anatomical hip joint parameters and kinematics and kinetics variables, during level walking. Fifty participants (m = 46, f = 4; age = 34 ± 7 years; BMI = 26 ± 4 kg/m²) underwent CT imaging and were diagnosed as either: symptomatic (15), if they showed a cam deformity and clinical signs; asymptomatic (19), if they showed a cam deformity, but no clinical signs; or control (16), if they showed no cam deformity and no clinical signs. Each participant's CT data was measured for: axial and radial alpha angles, femoral head-neck offset, femoral neck-shaft angle, medial proximal femoral angle, femoral torsion, acetabular version, and centre-edge angle. Participants performed level walking trials, which were recorded using a ten-camera motion capture system (Vicon MX-13, Oxford, UK) and two force plates (Bertec FP4060–08, Columbus, OH, USA). Peak sagittal and frontal hip joint angles, range of motion, and moments were calculated using a custom programming script (MATLAB R2015b, Natick, MA, USA). A one-way, between groups ANOVA examined differences among kinematics and kinetics variables (α = 0.05), using statistics software (IBM SPSS v.23, Armonk, NY, USA); while a stepwise multiple regression analysis examined associations between anatomical parameters and kinematics and kinetics variables. No significant differences in kinematics were observed between groups. The symptomatic group demonstrated lower peak hip abduction moments (0.12 ± 0.08 Nm/kg) than the control group (0.22 ± 0.10 Nm/kg, p = 0.01). Sagittal hip range of motion showed a moderate, negative correlation with radial alpha angle (r = −0.33, p = 0.02), while peak hip abduction moment correlated with femoral neck-shaft angle (r = 0.36, p = 0.009) and negatively with femoral torsion (r = −0.36, p = 0.009). With peak hip abduction moment in the stepwise regression analysis, femoral torsion accounted for a variance of 13.3% (F(1, 48) = 7.38; p = 0.009), while together with femoral neck-shaft angle accounted for a total variance of 20.4% (R² change = 0.07, F(2, 47) = 6.01; p = 0.047). Although elevated radial alpha angles may have limited sagittal range of motion, the cam deformity parameters did not affect joint moments. Femoral neck-shaft angle and femoral torsion were significantly associated with peak hip abduction moment, suggesting that the insertion location of the abductor affects muscle's length and its resultant force vector. A varus neck angle, combined with severe femoral torsion, may ultimately influence muscle moment arms and hip mechanics in individuals with cam FAI

Introduction. Reverse total shoulder arthroplasty continues to have a high complication rate, specifically with component instability and scapular notching. Therefore, the purpose of this study was to quantify the effects of humeral component neck angle and version on impingement free range of motion. Methods. A total of 13 cadaveric shoulders (4 males and 9 females, average age = 69 years, range 46 to 96 years) were randomly assigned to two studies. Study 1 investigated the effects of humeral component neck angle (n=6) and Study 2 investigated the effects of humeral component version (n=7). For all shoulders, Tornier Aequalis® Reversed Shoulder implants (Edina, MN) were used. For study 1, the implants were modified to 135, 145 and 155 degree humeral neck shaft angles and for Study 2 a custom implant that allowed control of humeral head version were used. For biomechanical testing, a custom shoulder testing system that permits independent loading of all shoulder muscles with six degree of freedom positioning was used. (Figure 1) Internal control experimental design was used where all conditions were tested on the same specimen. Study 1. The adduction angle and internal/external humeral rotation angle at which impingement occurred were measured. Glenohumeral abduction moment was measured at 0 and 30 degrees of abduction, and anterior dislocation forces were measured at 30 degrees of internal rotation, 0 and 30 degrees of external rotation with and without subscapularis loading. Study 2. The degree of internal and external rotation when impingement occurred was measured at 0, 30 and 60 degrees of glenohumeral abduction in the scapular plane with the humeral component placed in 20 degrees of anteversion, neutral version, 20 degrees of retroversion, and 40 degrees of retroversion. Statistical analysis was performed with a repeated measures analysis of variance with a Tukey post-hoc test with a significance level of 0.05. Results. Study 1. Adduction deficit angles for 155, 145, and 135 degree neck-shaft angle were 2 ± 5 degrees of abduction, 7 ± 4 degrees of adduction, and 12 ± 2 degrees of adduction (P <0.05), respectively. Impingement-free angles of humeral rotation and abduction moments were not statistically different between the neck-shaft angles. The anterior dislocation force was significantly higher for the 135degree neck-shaft angle at 30 degrees of external rotation and significantly higher for the 155 degree neck shaft angle at 30 degrees of internal rotation (P<.01). The anterior dislocation forces were significantly higher when the subscapularis was loaded (P <0.01). Study 2. Maximum external rotation was the limiting position for impingement particularly at 0 degrees of abduction. Maximum external rotation before impingement occurred increased significantly with increasing humeral retroversion (p < 0.05) (Figure 2). No impingement or subluxation occurred at any humeral version in 60 degrees of glenohumeral abduction. Conclusion. In reverse shoulder arthroplasty, 155 degree neck-shaft angle was more prone to impingement with adduction but had the advantage of being more stable. In addition, 40 degrees of retroversion has the largest range of humeral rotation without impingement

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

Scapular notching is a common problem following reverse shoulder arthroplasty (RSA). This is due to impingement between the humeral polyethylene cup and scapular neck in adduction and external rotation. Various glenoid component strategies have been described to combat scapular notching and enhance impingement-free range of motion (ROM). There is limited data available detailing optimal glenosphere position in RSA with an onlay configuration. The purpose of this study was to determine which glenosphere configurations would maximise impingement free ROM using an onlay RSA prosthesis. A three-dimensional (3D) computed tomography (CT) scan of a shoulder with Walch A1, Favard E0 glenoid morphology was segmented using validated software. An onlay RSA prosthesis was implanted and a computer model simulated external rotation and adduction motion of the virtual RSA prosthesis. Four glenosphere parameters were tested; diameter (36mm, 41mm), lateralization (0mm, 3mm, 6mm), inferior tilt (neutral, 5 degrees, 10 degrees), and inferior eccentric positioning (0.5mm, 1.5mm. 2.5mm, 3.5mm, 4.5mm). Eighty-four combinations were simulated. For each simulation, the humeral neck-shaft angle was 147 degrees and retroversion was 30 degrees. The largest increase in impingement-free range of motion resulted from increasing inferior eccentric positioning, gaining 15.0 degrees for external rotation and 18.8 degrees for adduction. Glenosphere lateralization increased external rotation motion by 13. 6 degrees and adduction by 4.3 degrees. Implanting larger diameter glenospheres increased external rotation and adduction by 9.4 and 10.1 degrees respectively. Glenosphere tilt had a negligible effect on impingement-free ROM. Maximizing inferior glenosphere eccentricity, lateralizing the glenosphere, and implanting larger glenosphere diameters improves impingement-free range of motion, in particular external rotation, of an onlay RSA prosthesis. Surgeons’ awareness of these trends can help optimize glenoid component position to maximise impingement-free ROM for RSA. Further studies are required to validate these findings in the context of scapulothoracic motion and soft tissue constraints

Aims. Metal-on-metal hip resurfacing (MoM-HR) has seen decreased usage due to safety and longevity concerns. Joint registries have highlighted the risks in females, smaller hips, and hip dysplasia. This study aimed to identify if reported risk factors are linked to revision in a long-term follow-up of MoM-HR performed by a non-designer surgeon. Methods. A retrospective review of consecutive MoM hip arthroplasties (MoM-HRAs) using Birmingham Hip Resurfacing was conducted. Data on procedure side, indication, implant sizes and orientation, highest blood cobalt and chromium ion concentrations, and all-cause revision were collected from local and UK National Joint Registry records. Results. A total of 243 hips (205 patients (163 male, 80 female; mean age at surgery 55.3 years (range 25.7 to 75.3)) with MoM-HRA performed between April 2003 and October 2020 were included. Mean follow-up was 11.2 years (range 0.3 to 17.8). Osteoarthritis was the most common indication (93.8%), and 13 hips (5.3%; 7M:6F) showed dysplasia (lateral centre-edge angle < 25°). Acetabular cups were implanted at a median of 45.4° abduction (interquartile range 41.9° - 48.3°) and stems neutral or valgus to the native neck-shaft angle. In all, 11 hips (4.5%; one male, ten females) in ten patients underwent revision surgery at a mean of 7.4 years (range 2.8 to 14.2), giving a cumulative survival rate of 94.8% (95% confidence interval (CI) 91.6% to 98.0%) at ten years, and 93.4% (95% CI 89.3% to 97.6%) at 17 years. For aseptic revision, male survivorship was 100% at 17 years, and 89.6% (95% CI 83.1% to 96.7%) at ten and 17 years for females. Increased metal ion levels were implicated in 50% of female revisions, with the remaining being revised for unexplained pain or avascular necrosis. Conclusion. The Birmingham MoM-HR showed 100% survivorship in males, exceeding the National Institute for Health and Care Excellence ‘5% at ten years’ threshold. Female sex and small component sizes are independent risk factors. Dysplasia alone is not a contraindication to resurfacing. Cite this article: Bone Jt Open 2023;4(11):853–858

The primary goals of successful rTSA (Reverse Total Shoulder Arthroplasty) are pain relief, improved shoulder motion and function with the restoration of patient independence. These goals can be achieved by optimal prosthesis design and surgical technique. Historically there have been two predominant reverse shoulder design philosophies: the traditional valgus 155-degree neck-shaft angle with a medialised center of rotation introduced by Dr. Grammont, and the more recent varus 135-degree neck-shaft angle with a lateralised center of rotation, developed by Dr. Frankle. The latter design has reported lower incidences of scapular notching, coupled with improved adduction and external rotation. Over time, an understanding of the factors which resulted in clinical complications and those that contributed to the clinical success of both these design philosophies has been analyzed and widely publicised. With the currently available reverse prostheses the surgeon is required to be committed to one design philosophy or the other. This commitment to one singular design may hinder surgeons from the ability to individualise each case regardless of patient anatomy, rotator cuff condition, arthritic state and post-operative expectation. Recently, a system has been launched which offers both design philosophies in one system, providing unsurpassed intra-operative flexibility. This allows the surgeon to adapt to each individual case and choose either design philosophy based on patient condition and anatomy, thus optimizing patient outcome. The treatment of proximal humeral fractures has historically included Hemi Arthroplasty (HA) or Total Shoulder Arthroplasty (TSA). However, rTSA has recently become the surgery of choice for many fracture treatments based on more reproducible results. Certain implant characteristics are gaining favor in the treatment of proximal humerus fractures namely:. Press fit humeral stems - which avoid the risks of cement in-between the tuberosities which has been reported to compromise healing. Proximal ‘box-shape’ geometry - which enables rotational stability especially in cases with proximal bone loss to promote reconstruction leading to improved healing. 135-degree neck-shaft angle - allowing a higher and more anatomic tuberosity position for more stable fixation maintains anatomical integrity of the tuberosities which has been reported as a critical factor for retaining rotator cuff function

Summary. Anatomical variations in hip joint anatomy are associated with both the presence and location of tibiofemoral osteoarthritis (OA). Introduction. Variations in hip joint anatomy can alter the moment-generating capacity of the hip abductor muscles, possibly leading to changes in the magnitude and direction of ground reaction force and altered loading at the knee. Through analysis of full-limb anteroposterior radiographs, this study explored the hypothesis that knees with lateral and medial knee OA demonstrate hip geometry that differs from that of control knees without OA. Patients and Methods. This cross-sectional study is an ancillary to the Multicenter Osteoarthritis Study (MOST), an observational cohort study of incident and progressive knee OA in community-dwelling men and women, ages 50–79 years. We report on 160 knees with lateral OA (LOA), 168 knees with medial OA (MOA), and 336 controls. All participants with LOA at the baseline MOST visit were included. An equal number of knees with MOA, and twice the number of control knees were then randomly selected. In participants with bilateral eligibility, a single knee was randomly selected so that all participants contributed only one case or one control knee to the analysis. Case knees were identified as having Kellgren/Lawrence (K/L) ≥ 2 with joint space narrowing (JSN) ≥ 1 in the specified compartment with no JSN in the adjoining compartment. Controls had no radiographic OA (K/L=0 or 1 and JSN=0) in either compartment. Hip joint anatomy parameters were assessed from full-limb standing radiographs using custom OsiriX software by an author (AB) blinded to knee OA status, and unreadable radiographs (N = 8) were discarded prior to unblinding. We measured parameters that influence the abductor moment arm of the hip, including: abductor lever arm, femoral offset, femoral neck length, femoral neck-shaft angle, height of hip centre, body weight lever arm, acetabular version, and abductor angle. All hip measurements were taken from the ipsilateral side of the knee in interest. Each variable was then compared independently among the three groups via analysis of covariance (ANCOVA), controlling for age, sex, and body mass index (BMI), and followed up with a post-hoc Bonferroni analysis to distinguish pairwise group differences. Results. The ANCOVA analysis showed a significant difference in height of hip centre (p=0.001), femoral neck-shaft angle (p=0.009), and abductor angle (p=0.001). Compared to controls, knees with LOA had an increased height of hip centre (p=0.001) and knees with MOA had a decreased abductor angle (p=0.046). Compared to knees with MOA, those with LOA had a more valgus neck-shaft angle (p=0.007) and increased abductor angle (p=0.001). Conclusion. Our study demonstrates that variations in hip geometry that affect the moment-generating capacity of the hip abductors are associated with the presence and compartmental distribution of tibiofemoral OA in the ipsilateral knee. Anatomical arrangements that reduce the hip abductor moment arm are more strongly associated with LOA than with MOA

Introduction. Acetabular and spino-pelvic (SP) morphological parameters are important determinants of hip joint dynamics. This study aims to determine whether acetabular and SP morphological differences exist between hips with and without cam morphology and between symptomatic and asymptomatic hips with cam morphology. Patients/Materials & Methods. A prospective cohort of 67 patients/hips was studied. Hips were either asymptomatic with no cam (Controls, n=18), symptomatic with cam (n=26) or asymptomatic with cam (n=23). CT-based quantitative assessments of femoral, acetabular, pelvic and spino-pelvic parameters were performed. Measurements were compared between controls and those with a cam deformity, as well as between the 3 groups. Morphological parameters that were independent predictors of a symptomatic Cam were determined using a regression analysis. Results. Hips with cam deformity had slightly smaller subtended angles superior-anteriorly (87° Vs 84°, p=0.04) and greater pelvic incidence (53° Vs 48°, p=0.003) compared to controls. Symptomatic Cams had greater acetabular version (p<0.01), greater subtended angles superiorly and superior-posteriorly (p=0.01), higher pelvic incidence (p=0.02), greater alpha angles and lower femoral neck-shaft angles compared to asymptomatic cams (p<0.01) and controls (p<0.01). The four predictors of symptomatic cam included antero-superior alpha angle, femoral neck-shaft angle, acetabular depth and pelvic incidence. Discussion. Symptomatic hips had a greater amount of supero-posterior coverage; which would be the contact area between a radial cam and the acetabulum, when the hip is flexed to 90°. Furthermore, individuals with symptomatic cam morphology had greater PI. Acetabular- and SP parameters should be part of the radiological assessment of femoro-acetabular impingement. Conclusion. Because of the association between a high PI and an increased risk of hip OA (also shown to be increased with c-FAI), the relationship between the PI and FAI should be taken into consideration in prospective longitudinal studies looking at factors influencing the formation of cam morphology as well as those at risk of developing symptoms and degenerative changes

This retrospective study was to investigate radiographic and clinical outcomes in treatment of hip instability in children and young adults undergoing periacetabular osteotomy (PAO) with or without femoral osteotomy. 19 patients (21 hips) with CP were treated with PAO with or without femoral osteotomy The mean age was 16.2 years old (7 to 28 years). Five patients (5 hips) received PAO, Six patients (7 hips) PAO with femoral derotation osteotomy, Eight patients (9 hips) PAO with varus derotational osteotomy (VDRO). Anteroposterior pelvic radiographs and CT were taken to assess the migration percentage (MP), lateral center-edge angle (LCEA), Sharp angle, femoral neck anteversion, neck-shaft angle. Gross Motor Function Classification System (GMFCS) was assessed pre- and post-surgery. Complications were recorded. The mean follow-up time was 41.2 months (range, 24 to 86 months). All hips but one were pain free at final visit. The GMFCS improved by one level in 10 of 19 patients. MP improved from a mean of 76.6% to 18.6% at the final follow-up(p<0.001). The mean pre-operative LCEA and Sharp angle were −33.5 ? and 35 ? respectively, improved to 21.5 ? and 11.8 ? at the final follow-up (p < 0.001). There were six patients (7 hips) had re-subluxation at latest follow-up. Nervus cutaneus femoris lateralis was impaired in four patients after surgery. There was no re-dislocation, AVN, or infections in this group. Satisfactory clinical and radiologic results can be obtained by PAO with or without femoral osteotomy minor complications