The outcome of periacetabular osteotomy in dysplastic hips is dependent on the absence of preoperative osteoarthritis [OA]. The purpose of this study was to analyze whether Tonnis grading is a reliable predictor of OA in patients with hip dysplasia. Thirty patients were identified who had undergone hip arthroscopy surgery to assess their suitability for periacetabular osteotomy. Radiographs were assessed for anterior centre edge angle, lateral centre edge angle, Tonnis angle and Tonnis grade for OA changes. The radiographic grading of OA was compared with arthroscopic findings. Results. The average age at the time of arthroscopy was 34.97 [16 – 53yrs] (28 females). Tonnis grade did not correlate with arthroscopic findings (p=0.082). There was a trend for patients with a higher Tonnis grade to have more OA changes. Of the 30 patients, all 3 with grade 0 were fit for periacetabular osteotomy, while only 8 out of 24 with grade I, and 1 out of 3 with grade II were fit for periacetabular osteotomy. This study reports that even when radiographic grading showed minimal OA changes, arthroscopy findings indicated significant OA changes. Hence radiographic grading is a poor indicator of OA and other diagnostic modality should be sought before proceeding with joint preserving surgery in this highly selected subgroup of dysplastic hips

Abstract. OBJECTIVES. Although surgical periacetabular osteotomy (PAO) for hip dysplasia aims to optimise acetabular coverage and restore hip function, it is unclear how surgery affects capsular mechanics and joint stability. The purpose was to examine how the reoriented acetabular coverage affects capsular mechanics and joint stability in dysplastic hips. METHODS. Twelve cadaveric dysplastic hips (n = 12) were denuded to the capsule and mounted onto a robotic tester. The robot positioned each hip in multiple flexion angles (Extension, Neutral 0°, Flexion 30°, Flexion 60°, Flexion 90°) and performed internal-external rotations and abduction-adduction to 5 Nm in each rotational or planar direction. Each hip underwent a PAO, preserving the capsule, and was retested postoperatively in the robot. Paired sample t-tests compared the range of motion before and after PAO surgery (CI = 95%). RESULTS. Pre-operatively, the dysplastic hips demonstrated large ranges of internal-external rotations and abduction-adduction motions throughout all flexion positions. Post-operatively, the PAO slackenend the anterosuperior capsule and tightened the inferior capsule. This increased external rotation in Flexion 60° and Flexion 90° (∆. ER. = +16 and +23%) but provided lateral coverage to decrease internal rotation at Flexion 90° (∆. IR. = –15%). The PAO also reduced abduction throughout, but increased adduction in Neutral 0°, Flexion 30°, and Flexion 60° (∆. ADD. = +34, +30%, +29% respectively). CONCLUSIONS. The PAO provided crucial osseous structural coverage to the femoral head, decreasing hypermobility and adverse loading at extreme hip flexion-extension. However, it also slackened the anterosuperior capsule and increased adduction and external rotation, which may lead to ischiofemoral impingement and adductor irritations. Capsular instability may be secondary to acetabular undercoverage, thus capsular alteration may be warranted for larger corrections or rotational osteotomies. To preserve native hip and delay joint degeneration, it is crucial to preserve capsule and elucidate amount of reorientation needed without causing iatrogenic instability. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Introduction. Progressive resistance training (PRT) as a mean to reduce symptoms in patients with hip dysplasia (HD) has not yet been tried out. The aim of this study was to examine if PRT is feasible in patients with HD. A secondary purpose was to report data on changes of patient reported outcomes, muscle performance and hip muscle strength following PRT. Materials and methods. Patients diagnosed with HD on the waiting list for a periacetabular osteotomy (PAO) were offered to participate in a PRT feasibility study. The PRT intervention consisted of 8-weeks of supervised PRT consisting of 20 training sessions with exercises for the hips and knees. Feasibility was evaluated as adherence, the number of dropouts and adverse events. Furthermore, pain was reported after each exercise and one day after a training session using a 100mm visual analog scale (VAS). Pain was categorized as “safe” (VAS ≤20), “acceptable” (VAS >20–50) and “high risk” (VAS >50). Pre- and post the intervention patients completed the Copenhagen Hip and Groin Outcome Score (HAGOS), performed two hop-tests on each leg and had their peak torque of the hip extensors and flexors assessed by isokinetic dynamometry. Results. 16 patients, mean age 28 (range 22–40) years, completed the PRT intervention. Adherence was high (90.3% ±9.0%). Acceptable pain levels (VAS ≤50) were reported on average of 95% during the completed PRT sessions and after 92.3% of the sessions when assessed on the following day. Four out of six HAGOS subscales improved (P <0.05) after the intervention, as did standing distance jump and countermovement jump (8.3 cm 95% CI [1.2, 15.3], 1.8 cm [0.7, 2.9]) on the affected side. Dynamometry showed significant improved peak torque during isokinetic concentric hip flexion (15.8 Nm 95% CI [5.9, 25.8]) on the affected side. A similar improvement was seen during isometric hip flexion on the non-affected side. Conclusion. Supervised preoperative PRT is feasible in terms of drop outs, adherence, adverse events and pain levels in patients with HD scheduled for PAO. Furthermore, this feasibility study suggests that PRT may improve pain levels, patient reported outcomes, functional performance and hip flexion muscle strength

Biomechanical analysis is important to evaluate the effect of orthopaedic surgeries. CT-image based finite element method (CT-FEM) is one of the most important techniques in the computational biomechanics field. We have been applied CT-FEM to evaluate resorptive bone remodeling, secondary to stress shielding, after total hip arthroplasty (THA). We compared the equivalent stress and strain energy density to postoperative BMD (bone mineral density) change in the femur after THA, and a significant correlation was observed between the rate of changes in BMD after THA and equivalent stress. For periacetabular osteotomy cases, we investigated mechanical stress in the hip joint before and after surgery. Mechanical stress in the hip joint decreased significantly after osteotomy and correlated with the degree of the acetabular coverage. For arthroscopic osteochondroplasty cases, we examined mechanical strength of the proximal femur after cam resection using CT-FEM. The results suggested that both the depth and area of the resection at the distal part of femoral head-neck junction correlated strongly with fracture risk after osteochondroplasty. This talk consists of our results of clinical application studies using CT-FEM, and importance of application of CT-FEM to biomechanical studies to assess the effect of orthopaedic surgeries

Acetabular dysplasia was produced in 24 immature white rabbits. A rotational acetabular osteotomy was then carried out and radiological and histological studies of the articular cartilage were made.

In the hips which did not undergo osteotomy, radiographs at 26 weeks showed that residual subluxation remained and arthritic changes such as narrowing of the joint space or dislocation were still seen. However, in the operated group there was a remarkable increase in cover, but arthritic changes were not observed. After 24 weeks, the Mankin grading score in the operated group was significantly lower than that in the non-operated group. The latter hips showed an irregular surface of the cartilage, exfoliation and proliferation of synovial tissue. In those undergoing osteotomy, primary cloning of chondrocytes or hypercellularity was seen and at 24 weeks after operation and metaplasia of the cartilage in the fibrous tissue was observed in the boundary between the medial area of the acetabulum and the acetabular fossa.