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.

Introduction: Adequate bone in the femoral head and neck is a prerequisite in ensuring the longevity of a surface arthroplasty. The pistol grip deformity is one of the most common bony abnormalities of the femoral head encountered at the time of resurfacing. Severe flattening results in segmental bone loss requiring adjustments in the alignment of the femoral component to achieve optimal orientation. However, very little is known as to how the femoral implant positioning will be affected by increasing deformity. The purpose of this study was to classify the deformity of the femoral head to better understand how it influences the alignment of the femoral component during surface arthroplasty. This classification was then used to determine whether the femoral implant can be safely inserted with optimal alignment despite progressive deformity of the femoral head and neck. Methods: The classification was developed using plain radiographs and computer tomography scans from 61 patients (66 hips) who presented with primary osteoarthritis prior to hip resurfacing. Surface arthroplasty simulations were generated with three-dimensional computed tomography to quantify the change in femoral component orientation from the neutral position that would allow optimal alignment. The biomechanical parameters were also calculated to determine the influence of the deformity on the final implant position. Results: There were 47 men and 14 women, with a mean age of 50.3 years (range, 33 to 63 years). Three categories of femoral head deformity were created using a modified femoral head ratio (Normal ≥0.9, Mild = 0.75 – 0.9 and Severe < 0.75). There were a total of 32 normal hips (48%), 23 hips (35%) with mild deformity and 11 hips (17%) with severe deformity of the proximal femur. A severe deformity required significantly more superior translation of the entry point (p=0.027) and greater reaming depth (p=0.012) to allow safe insertion in relative valgus without notching. This could be achieved while preserving length discrepancy (p=0.17) and minimizing the component-head size difference (p=0.16), although femoral offset was significantly reduced (p=0.025). Conclusion: A classification of femoral head deformity was created to better understand how progressive deformity influences the alignment of the femoral component during surface arthroplasty. This classification is simple and easily measured using standard AP radiographs of the hip. We found that the femoral component can be safely inserted with optimal alignment during surface arthroplasty by modifying the surgical technique in the face of severe deformity

Background: Deformity of the femoral head after open reduction for developmental dislocation of the hip (DDH) influences the outcome of pelvic osteotomy as a final correction for residual dysplasia to prevent secondary osteoarthritis. The purpose of this study was to review long-term outcomes after open reduction using a medial approach for DDH. The correlation between age at the time of operation and femoral head deformity at skeletal maturity was specifically evaluated. Methods: Forty-two hips in 40 patients with more than 10 years of follow-up were assessed radiologically. The mean age at the time of surgery was 14.3 (range, 6–31) months, and the postoperative follow-up period ranged from 10 to 27 (mean, 15.8) years. The round and enlargement indices of the femoral head were measured on follow-up radiographs to evaluate deformity and enlargement of the femoral head at skeletal maturity. Results: Severin classification was I and II in 16 hips; III, IV, and V in 23; and II at the final follow-up in the 3 hips treated by osteotomy less than 10 years after open reduction. Mean round index at follow-up was 58.3 ± 8.3 (range, 47–79); it showed correlation with age at the time of operation (r = 0.68, p < 0.001). Mean enlargement index at follow-up was 113.4 ± 11.8 (range, 93–137) and showed no correlation with age at the time of operation (r = 0.009, p = 0.96). Conclusions: At more than 10 years’ follow-up, the occurrence of deformity of the femoral head correlated with increased age at the time of operation. Indications for use of a medial approach in the correction of DDH in older patients must take into account the risk of subsequent femoral head deformity at skeletal maturity

The most important outcome predictor of Legg-Calvé-Perthes disease (LCPD) is the shape of the healed femoral head. However, the deformity of the femoral head is currently evaluated by non-reproducible, categorical, and qualitative classifications. In this regard, recent advances in computer vision might provide the opportunity to automatically detect and delineate the outlines of bone in radiographic images for calculating a continuous measure of femoral head deformity. This study aimed to construct a pipeline for accurately detecting and delineating the proximal femur in radiographs of LCPD patients employing existing algorithms. To detect the proximal femur, the pretrained stateof-the-art object detection model, YOLOv5, was trained on 1580 manually annotated radiographs, validated on 338 radiographs, and tested on 338 radiographs. Additionally, 200 radiographs of shoulders and chests were added to the dataset to make the model more robust to false positives and increase generalizability. The convolutional neural network architecture, U-Net, was then employed to segment the detected proximal femur. The network was trained on 80 manually annotated radiographs using real-time data augmentation to increase the number of training images and enhance the generalizability of the segmentation model. The network was validated on 60 radiographs and tested on 60 radiographs. The object detection model achieved a mean Average Precision (mAP) of 0.998 using an Intersection over Union (IoU) threshold of 0.5, and a mAP of 0.712 over IoU thresholds of 0.5 to 0.95 on the test set. The segmentation model achieved an accuracy score of 0.912, a Dice Coefficient of 0.937, and a binary IoU score of 0.854 on the test set. The proposed fully automatic proximal femur detection and segmentation system provides a promising method for accurately detecting and delineating the proximal femoral bone contour in radiographic images, which is necessary for further image analysis

LCPD can cause femoral head deformity and osteoarthritis requiring total hip replacement (THR). Currently, there is little data on how patients are functioning after a THR from patients’ perspective. The purpose of this study was to collect a large patient-reported outcome data set on adults with LCPD, including those who had a THR, using a Web-survey method and to compare their outcomes to a normative population. An English REDCap-based survey was built and made available on a LCPD study group website. The survey included childhood and adult LCPD history, SF-36 Health Survey, and the Hip Disability and Osteoarthritis Outcome Score (HOOS). Statistical analysis included t-test and linear and proportional odds regressions. Of the 1182 participants who completed the survey, 261 participants (89 M, 172 F) had a THR. The mean age at survey was 44.6±12.4 years (range 20–79). The mean duration since THR was 7.2±8 years (median 4, range 0–43). Gender and age matched analysis showed that THR participants had significantly lower HOOS Quality-of-Life and Sports scores (p<0.0001) for all age groups in comparison to a normative cohort. In women, the HOOS Symptoms, Daily Living, and Pain scores were also significantly lower in the <55 age groups (p<0.05). Similarly, SF-36 scores were significantly lower (p<0.05) in female <45 age groups in 5 out of 8 SF-36 scales. Overall, hip dysplasia and the number of years-from-THR were the main factors associated with worse SF-36 and HOOS scores. In comparison to the non-THR participants, THR participants had higher scores in some of the HOOS and SF-36 scales. LCPD participants with THR had significantly worse HOOS and SF-36 scores in most of the scales studied than a normative cohort, especially in women. There is significant disability even after a THR, warranting continued efforts to improve treatment and outcome

Femoroacetabular impingement (FAI) – enlarged, aspherical femoral head deformity (cam-type) or retroversion/overcoverage of the acetabulum (pincer-type) – is a leading cause for early hip osteoarthritis. Although anteverting/reverse periacetabular osteotomy (PAO) to address FAI aims to preserve the native hip and restore joint function, it is still unclear how it affects joint mobility and stability. This in vitro cadaveric study examined the effects of surgical anteverting PAO on range of motion and capsular mechanics in hips with acetabular retroversion. Twelve cadaveric hips (n = 12, m:f = 9:3; age = 41 ± 9 years; BMI = 23 ± 4 kg/m2) were included in this study. Each hip was CT imaged and indicated acetabular retroversion (i.e., crossover sign, posterior wall sign, ischial wall sign, retroversion index > 20%, axial plane acetabular version < 15°); and showed no other abnormalities on CT data. Each hip was denuded to the bone-and-capsule and mounted onto a 6-DOF robot tester (TX90, Stäubli), equipped with a universal force-torque sensor (Omega85, ATI). The robot positioned each hip in five sagittal angles: Extension, Neutral 0°, Flexion 30°, Flexion 60°, Flexion 90°; and performed hip internal-external rotations and abduction-adduction motions to 5 Nm in each position. After the intact stage was tested, each hip underwent an anteverting PAO, anteverting the acetabulum and securing the fragment with long bone screws. The capsular ligaments were preserved during the surgery and each hip was retested postoperatively in the robot. Postoperative CT imaging confirmed that the acetabular fragment was properly positioned with adequate version and head coverage. Paired sample t-tests compared the differences in range of motion before and after PAO (CI = 95%; SPSS v.24, IBM). Preoperatively, the intact hips with acetabular retroversion demonstrated constrained internal-external rotations and abduction-adduction motions. The PAO reoriented the acetabular fragment and medialized the hip joint centre, which tightened the iliofemoral ligament and slackenend the pubofemoral ligament. Postoperatively, internal rotation increased in the deep hip flexion positions of Flexion 60° (∆IR = +7°, p = 0.001) and Flexion 90° (∆IR = +8°, p = 0.001); while also demonstrating marginal decreases in external rotation in all positions. In addition, adduction increased in the deep flexion positions of Flexion 60° (∆ADD = +11°, p = 0.002) and Flexion 90° (∆ADD = +12°, p = 0.001); but also showed marginal increases in abduction in all positions. The anteverting PAO restored anterosuperior acetabular clearance and increased internal rotation (28–33%) and adduction motions (29–31%) in deep hip flexion. Restricted movements and positive impingement tests typically experienced in these positions with acetabular retroversion are associated with clinical symptoms of FAI (i.e., FADIR). However, PAO altered capsular tensions by further tightening the anterolateral hip capsule which resulted in a limited external rotation and a stiffer and tighter hip. Capsular tightness may still be secondary to acetabular retroversion, thus capsular management may be warranted for larger corrections or rotational osteotomies. In efforts to optimize surgical management and clinical outcomes, anteverting PAO is a viable option to address FAI due to acetabular retroversion or overcoverage

Introduction. Legg-Calvé-Perthes disease (LCPD) often results in femoral head deformity and leg length discrepancy (LLD). Objective of this study was to analyse femoral morphology in LCPD patients at skeletal maturity to assess where the LLD originates, and evaluate the effect of contralateral epiphysiodesis for length equalisation on proximal and subtrochanteric femoral lengths. Materials and Methods. All patients treated for LCPD in our institution between January 2013 and June 2020 were retrospectively reviewed. Patients with unilateral LCPD, LLD of ≥5mm and long leg standing radiographs at skeletal maturity were included. Total leg length, femoral and tibial length, articulotrochanteric distance (ATD) and subtrochanteric femoral length were compared between LCPD side and unaffected side. Furthermore, we compared leg length measurements between patients who did and who did not have a contralateral epiphysiodesis. Results. 79 patients were included, 21/79 underwent contralateral epiphysiodesis for leg length correction. In the complete cohort the average LLD was 1.8cm (95% CI 1.5 – 2.0), average ATD difference was 1.8cm (95% CI −2.1 – −1.9) and average subtrochanteric difference was −0.2cm (95% CI −0.4 – 0.1). In the epiphysiodesis group the average LLD before epiphysiodesis was 2.7 (1.3 – 3.4) cm and 1.3 (−0.5 – 3.8) cm at skeletal maturity. In the non-epiphysiodesis group the average LLD was 2.0 (0.5 – 5.1), p=0.016. The subtrochanteric region on the LCPD side was significantly longer at skeletal maturity in the epiphysiodesis group compared to the non-epiphysiodesis group: −1.0 (−2.4 – 0.6) versus 0.1 (−1.0 – 2.1), p<0.001. Conclusions. This study concludes that LLD after LCPD originates from the proximal segment only. In patients who had had a contralateral epiphysiodesis, the subtrochanteric femoral region was significantly longer on the LCPD side. These anatomical changes need to be considered by paediatric surgeons when advising leg length equalisation procedures, and by arthroplasty surgeons when LCPD patients present for hip arthroplasty

Perthes disease is a childhood disorder often resulting in femoral head deformity. Categorical/dichotomous outcomes of deformity are typical clinically, however quantitative, continuous measures, such as Sphericity Deviation Score (SDS), are critical for studying interventions. SDS uses radiographs in two planes to quantify femoral head deformity. Limitations of SDS may include non-orthogonal planes and lost details due to projections. We applied this method in 3D, with specific objectives to: 1. Develop SDS-like sphericity measures from 3D data 2. Obtain 2D and 3D sphericity for normal and Perthes hips 3. Compare slice-based (3D) and projection-based (2D) sphericity CT images of 16 normal (8 subjects) and 5 Perthes hips (4 subjects) were segmented to create 3D hip models. Ethics board approval was obtained for this study. SDS consists of roundness error (RE) in two planes and ellipsoid deformation (ED) between planes. We implemented a modified SDS which was applied to (a) orthogonal projections simulating radiographs (sagittal/coronal; 2D-mSDS), and (b) largest radii slices (sagittal/coronal; 3D-mSDS). Mean 2D-mSDS was higher for Perthes (27.2 (SD 11.4)) than normal (11.9 (SD 4.1)). Mean 3D-mSDS showed similar trends, but was higher than 2D (Perthes 33.6 (SD 5.3), normals 17.0 (SD 3.1)). Unlike 2D-mSDS, 3D-mSDS showed no overlap between groups. For Perthes hips, 2D-mSDS was consistent with SDS. For normal hips, 2D-mSDS was higher than expected (similar to Stulberg II). Projection-based (2D) measures may produce lower mSDS due to spatial averaging. Slice-based (3D) measures may better distinguish between normal and Perthes shapes, which may better differentiate effectiveness of treatments

Method. The anteroposterior pelvic radiographs of 84 children (87 hips with developmental dysplasia) seen between 1995 and 2004 were reviewed retrospectively. Each radiograph was photographed digitally and converted to the negative using Microsoft Photo Editor. Arthrograms were also assessed at the time of femoral head reduction. The acetabular index (AI) and femoral head deformity were assessed. Acetabular response was measured using the AI at 6 and 12 months post-reduction. Results. Mean age at presentation was 11 months for the closed reduction group, versus 19 months for those with an arthrographic soft tissue obstruction requiring open reduction. Additionally, the average age of the children that underwent open reduction who later required a Salter osteotomy was 27 ± 3 months compared to an average of 14 ± 1.5 months for those who did not. The acetabular response was maximal during the first 6 months following treatment. Closed reduction (24 hips) gave comparable results to open reduction (63 hips), although the initial AI was greater in those requiring open reduction (39.5 ± 6.3° versus 36.1 ± 4.6°). Using two separate Bonferroni pairwise comparisons revealed no statistical difference in response between closed and open reduction. Arthrography revealed that hips requiring open reduction were more deformed, with spherical femoral heads in 29% as opposed to 68% in the closed reduction group. The AI was also slightly less (36.6 ± 3.2°) when the femoral head was spherical in comparison to those hips with an aspherical femoral head (38.0 ± 6.6°). Conclusion. Age at presentation and femoral head deformity therefore influence the outcome of reduction, but the acetabular index improves to a similar degree whether closed or open reduction is required

The hip-shelf procedure is less often indicated since the introduction of peri-acetabular osteotomy (PAO). Although this procedure does not modify pelvic shape, its influence on subsequent total hip arthroplasty (THA) is not known. We performed a case-control study comparing THA after hip-shelf surgery and THA in dysplastic hips to determine: 1) its influence on THA survival, 2) technical issues and complications related to the former procedure. We performed a retrospective case-control study comparing 61 THA cases done after hip-shelf versus 63 THA in case-matched dysplastic hips (control group). The control group was matched according to sex, age, BMI, ASA and Charnley score, and bearing type. We compared survival and function (Harris, Oxford-12), complications at surgery, rate of bone graft at cup insertion, and post-operative complications. The 13-year survival rates for any reason did not differ: 89% ± 3.2% in THA after hip shelf versus 83% ± 4.5% in the controls (p = 0.56). Functional scores were better in the control group (Harris 90 ± 10, Oxford 41/48) than in the hip-shelf group (Harris 84.7 ± 14.7, Oxford 39/48) (p = 0.01 and p = 0.04). Operative time, bleeding and rate of acetabular bone grafting (1.6 hip-shelf versus 9.5 control) were not different (p > 0.05). Postoperative complication rates did not differ: one transient fibular nerve palsy and two dislocations (3.2%) in the hip-shelf group versus four dislocations in the control group (6.3%). The hip-shelf procedure does not compromise the results of a subsequent THA in dysplastic hips. This procedure is simple and may keep its indications versus PAO in severely subluxed hips or in case of severe femoral head deformity

Severe femoral head deformities due to Perthes' disease are characterized by limitation of ROM, pain, and early degeneration, eventually becoming intolerable already in early adulthood. Morphological adaptation of the acetabulum is substantial and complex intra- and extraarticular impingement sometimes combined with instability are the underlying pathologies. Improvement is difficult to achieve with classic femoral and acetabular osteotomies. Since 15 years we have executed a head size reduction. With an experience of more than 50 cases no AVN of the femoral head was recorded. In two hips fracture of the medial column of the neck has been successfully treated with subsequent screw fixation. The clinical mid-term results are characterized by substantial increase of hip motion and pain reduction. Surgical goal is to obtain a smaller head, well contained in the acetabulum. It should become as spherical as possible and the gliding surface should be covered with best available cartilage. Together, it has to be accomplished under careful consideration of the blood supply to the femoral head. In the majority of cases acetabular reorientation is necessary to optimize joint stability. Femoral head segment resections without guidance is difficult. Therefore, 3D-simulation for cut direction and segment size including the implementation of the resultant osteotomy configuration was developed using individually manufactured cutting jigs. First experience in five such cases have revealed good results. The forthcoming steps are the improvement of computer algorithm and automation. Goal is that with first cut decision the other cuts are automatically determined resulting in optimal head size and sphericity

Introduction and Aims: In a radiological study we evaluated the outcome of the Chiari osteotomy as a primary method of femoral head containment in patients with Perthes’ disease presenting at the age of eight years or older. Even when Salter’s prerequisites are met, the results of a Salter osteotomy is known to be poor in this group. Method: Thirteen patients underwent a Chiari osteotomy at a mean age of nine years and four months. The osteotomy was performed before femoral head deformity had occurred. The hip was considered to be at risk because of the late onset of the disease. Measurements were made on the pre-operative x-ray, the pre-operative arthrogram and the latest follow-up x-rays. Patients have been followed up for an average of five years and four months. On the pre-operative arthrogram there was no femoral head deformity or hinging on abduction. At the time of surgery it was too early in the disease process to assign a hip reliably to a particular classification. During the follow-up period, 12 hips manifested as a Catterall group IV. Eleven hips became Herring type B and two Herring type C. Results: At latest follow-up all hips could be reliably graded according to the Stulberg classification. Currently, eight hips were a Stulberg type II and five a Stulberg type III, but this might change as skeletal maturity is reached. It is clear that none of the hips will be a Stulberg type IV or V, which is seen in a significant number of untreated hips at this age. Conclusion: The Chiari osteotomy achieves a congruent hip in this specific group of patients where a poor outcome would otherwise be anticipated

In a radiological study, we evaluated the outcome of the Chiari osteotomy as a primary method of femoral head containment in a distinct group of patients with Perthes’ disease. Even when Salter’s prerequisites are met, the results of a Salter osteotomy are known to be poor in this particular group of patients. At the time of operation, the mean age of the 13 patients who underwent Chiari osteotomy was 9 years 4 months. The osteotomy was performed early in the disease process, before femoral head deformity had occurred. The hip was considered to be at risk because of the relatively late onset of the disease. Measurements were made on the preoperative and latest follow-up X-rays, and on the preoperative arthrogram. Patients were followed up for a mean of 3 years 4 months. On the preoperative arthrogram there was no femoral head deformity or hinging on abduction. At the time of surgery, it was too early to assign a hip reliably to a particular lateral or Herring lateral pillar group. However, during the follow-up period, 12 of the hips manifested as Catterall group IV and one as Catterall group II. Further, 11 hips advanced to become lateral pillar type B, and two to become lateral pillar type C. At follow-up, nine hips could be reliably graded according to the Stulberg classification: five were Stulberg type II and four Stulberg type III. It was clear that none of the remaining hips would be Stulberg type IV or V. The Chiari osteotomy achieves a congruent hip in a specific group of patients where a poor outcome would otherwise be anticipated

Femoral head deformity can be a devastating outcome in a small percentage of patients with Perthes' disease. Deformities usually start during the fragmentation stage. In this study, we aimed to determine the effects of Vitamin D deficiency on the natural history of Perthes' disease. Patients with Perthes' disease and Vitamin D deficiency presenting to our unit in the last 3 years were identified. All X-rays were reviewed retrospectively to determine the duration of the fragmentation and ossification stages. Treatment methods were obtained from the notes. Late presenters (i.e. after fragmentation stage) were excluded. In our unit, Vitamin D deficiency is diagnosed if levels <72 nmol/L. Fifteen patients (17 hips) with Perthes' disease were found to be Vitamin D deficient. Levels ranged from (18–71 nmol/L). The mean length of the fragmentation stage was 15.7 months which is significantly higher than quoted literature figures (8 months). Ossification stage duration was 18.8 months which was comparable to quoted figures. However, patients with severe Vitamin D deficiency (< 52 nmol/L) were found to have longer ossification stage (20.6 months) compared with patients with mild deficiency (52–72 nmol/L) (16.4 months). Seven out of 16 patients (44%) required surgical containment which is significantly higher than the usually low rates of surgical intervention. The critical fragmentation stage in Vitamin D deficiency is significantly longer putting the femoral head at higher risk of deformity and extrusion. This leads to higher rates of surgical containment. Also the severity of Vitamin D deficiency might be an important determinant of the period of time required for ossification and healing. Vitamin D level is an important prognostic factor and must be measured in all patients with Perthes' disease. Prescribing Vitamin D supplements is advisable in this group of patients. However, the effects of these supplements on the course of the disease requires further research. Level of evidence: III

Aim: To assess the outcome for Perthes disease in children over eight treated by observation, varus osteotomy, abduction plasters and acetabular augmentation. Methods and results: A retrospective case note review of prospectively collected data for 44 children (48) hips with Catterall grades 2, 3 or 4 Perthes’ disease with onset age eight or older and followed to maturity was performed. The groups were demographically similar. For all groups combined 60% had a satisfactory Stulberg grade I to III outcome. Poorer outcomes (as assessed by Stulberg, centre edge angle and Reimer’s migration index) were associated with increasing age, greater initial head deformity and greater head involvement. Initial head deformity did not remodel for any treatment group. Indeed, progressive head deformity occurred despite plaster treatment or varus osteotomy but not after acetabular augmentation. Hips managed by acetabular augmentation also had better outcomes than the other groups for Stulberg, Reimer’s index and centre-edge angle. Conclusions: Whatever the treatment the outcome for Perthes’ disease in children over eight is poorer with increasing age. No treatment offers the prospect of a good result in the older child with significant head involvement or significant initial deformity but acetabular augmentation seems to improve Stulberg, Reimer’s migration and centre-edge angle outcomes and prevents progressive femoral head deformity compared with observation, varus osteotomy and plaster treatment

The changes of stress distribution in the femoral head with Perthes disease were observed under several condition. Finite element models were constructed referring to X-ray images and magnetic resonance images of the intact hip joint. The model was divided into five parts: cancellous bone, articular cartilage, necrotic bone, cortical bone, physeal cartilage. Material properties were alloted to these components by the past literature. The body weight and abductor muscle force were applied as loading. The model was altered to study the effect of age, the extent of necrosis, and lateralization of the fomoral head. Analysis were performed on a digital computer PC-9821(NEC) using the finite element program. There was no significant difference in stress distribution patterns regardless of age or extent of necrosis. However, compressive stresses were concentrated on the lateral portion of the epiphysis by lateralization of femoral head. The femoral head deformity in Perthes disease was more affected by the lateralization than by the age and the extent of necrosis

Open reduction for developmental dislocation of the hip (DDH) is invasive and sometimes results in femoral head deformity while open reduction has been the first choice in case non-operative reduction is failed in. We treated 3 patients with 3 affected hips using minimum invasive arthroscopic reduction method. Pre-operative MRIs represented these 3 hips had obstruction of interposed thick limbus. The average age of patients treated by this method was 23 months. This method consists of arthrogram, arthroscopic limboplasty, and arthroscopic reduction. This series of maneuvers was able to lead unreducable hips to the reduction position. Post-operative MRIs represented that the interposed thick limbus had been removed to the outside of acetabulum and the limbus covered the reduced femoral head. There were no signs of residual subluxation of the hips in radiographic examination. This new minimum invasive arthroscopic reduction method have a possibility to take the place of the invasive open reduction in the treatment of DDHs with obstruction of interposed thick limbus

Cam-type femoroacetabular impingement (cam-FAI) can be treated with femoral neck osteochondroplasty to increase the clearance between the femoral head/neck and the acetabular rim. Because femur-acetabulum contact is very difficult to assess directly in patients, it is not clear if this surgery achieves its objective of reducing femur-acetabulum contact, and it is not clear how much of the femoral head/neck region should be resected to allow clearance in all activities. Our research question was: “Does femoral neck osteochondroplasty increase femur-acetabulum clearance in an extreme hip posture in patients with cam FAI?”. We recruited 8 consecutive patients scheduled to undergo arthroscopic femoral neck osteochondroplasty to treat cam-type FAI. We assessed clearance between the acetabulum and the femoral neck before surgery and at 6 months post-op using an upright open MRI scanner that allowed the hip to be scanned in flexed postures. We scanned each subject in a supine hip flexion (90 degree), adduction and internal rotation (FADIR) posture. We measured the beta angle, which describes clearance between the acetabular rim and the femoral head/neck deformity. Osteochondroplasty increased clearance from a mean beta angle of −9.4 degrees (SD 19.3) to 4.4 degrees (SD 16.2°) (p<0.05). This finding suggests that femoral neck osteochondroplasty increases femur-acetabulum clearance substantially for a posture widely accepted to provoke symptoms in patients with cam-FAI

Femoral head deformity with flattening and lateral protrusion can occur secondary to epiphyseal dysplasia or avascular necrosis of any aetiology in childhood. This causes painful impingement of the lateral femoral head on the acetabular lip, a phenomenon known as hinge abduction. We aimed to review our experience of valgus extension osteotomy in the treatment of hinge abduction in children and young adults with avascular necrosis. Twenty patients undergoing valgus osteotomy for hinge abduction performed by a single specialist were clinically and radiologically reviewed. The aetiology was Perthes disease in 16 patients and treatment of DDH in 4 patients. The indication for the procedure was pain and limited abduction. The mean follow-up was 4.5 years. Patients were assessed using modified Iowa hip scores at final follow-up. The procedure corrected some leg shortening and improved the abduction range of the affected hip. Overall 80 % of patients did well. The mean Iowa hip score in Perthes group was 84 at final follow-up. Four patients preoperatively had cysts/ defects in their femoral head. These were seen to fill up during their postoperative follow-up. Poorer outcome was associated with preoperative hip stiffness and surgery before stabilisation of the avascular process. Conclusion: Valgus osteotomy is an effective procedure for relieving hinge abduction with associated additional benefits including improvement of leg shortening and improvement in hip abduction. The procedure should be avoided in stiff hips

Aims

Though the pathogenesis of Legg-Calve-Perthes disease (LCPD) is unknown, repetitive microtrauma resulting in deformity has been postulated. The purpose of this study is to trial a novel upright MRI scanner, to determine whether any deformation occurs in femoral heads affected by LCPD with weightbearing.