In developmental dysplasia of the hip (DDH), a bone defect is often observed superior to the acetabulum after the reconstruction at the level of the true acetabulum during total hip replacement (THR). However, the essential amount of uncemented acetabular component coverage required for a satisfactory outcome remains controversial. The purpose of this study was to assess the stability and function of acetabular components with a lack of coverage > 30% (31% to 50%). A total of 760 DDH patients underwent THR with acetabular reconstruction at the level of the true floor. Lack of coverage above the acetabular component of > 30% occurred in 56 patients. Intra-operatively, autogenous morcellised bone grafts were used to fill the uncovered portion. Other than two screws inserted through the acetabular shell, no additional structural supports were used in these hips. In all, four patients were lost to follow-up. Therefore, 52 patients (52 hips, 41 women and 11 men) with a mean age of 60.1 years (42 to 78) were available for this study at a mean of 4.8 years (3 to 7). There were no instances of prosthesis revision or marked loosening during the follow-up. The Harris hip score improved from a mean of 40.7 points (. sd. 12.2) pre-operatively to 91.1 (. sd. 5.0) at the last follow-up. Radiological analysis with medical imaging software allowed us to calculate the extent of the uncoverage in terms of the uncovered arc of the implant as viewed on the anteroposterior pelvic radiograph. From this we propose that up to 17 mm of lateral undercoverage in the presence of a stable initial implantation in the presence of bone autografting, with an inclination angle of the acetabular component between 40° and 55°, is acceptable. This represents undercoverage of ≤ 50%. Cite this article: Bone Joint J 2013;95-B:1178–83

Aims

We compared the clinical outcomes of curved intertrochanteric varus osteotomy (CVO) with bone impaction grafting (BIG) with CVO alone for the treatment of osteonecrosis of the femoral head (ONFH).

Severe acetabular dysplasia with established dislocation of the hip represents a common problem in cerebral palsy. Once significant dysplasia is present little remodeling of the acetabulum occurs with femoral osteotomies alone. Pelvic osteotomies should address the problem of acetabular deficiency in order to restore optimal coverage of the femoral head. Standard innominate oste-otomies are not recommended for neuromuscular hip dysplasia. To address the lack of postero-lateral coverage in this population, a modified periacetabular osteotomy was performed. Between 1991 and 2000 a total of forty-four patients (fifty-two hips) with total body involvement CP underwent this procedure at a mean age of nine, four yrs. The modification includes only one bicortical cut at the posterior corner at the sciatic notch. The cut extends down to the triradiate cartilage, if present, and through the former site of the triradiate cartilage after closure of the acetabular growth plate in adolescence. Additional procedures included: open reduction, femoral varus osteotomy, and soft tissue releases. Follow-up included a subjective and clinical evaluation. Radiographic assessment included measurements of the migration percentage and acetabular index, evidence of AVN, and premature closure of the triradiate cartilage. The mean follow-up period for these patients was 3.5 years (1.0 to 8,1 yrs) after surgery, and 70% of the patients had reached skeletal maturity at that time. The median acetabular index improved from 30% pre-operatively to 18% at follow-up. The median migration percentage was 71% preoperatively, and zero at follow-up. A re-dislocation occurred in one hip, and a re-subluxation in another. All other hips were stable and well contained at follow-up. There were three hips showing signs of postoperative femoral head defects . Premature closure of the triradiate cartilage was not noted. The care-givers had the impression that the surgery had improved personal care, positioning/transferring, and comfort. This osteotomy reduces the volume of the elongated acetabulum and provides coverage by articular cartilage. It provides coverage particularly at the posterior part of the acetabulum. Compared to other techniques this modified periacetabular osteotomy has only one posterior cortical cut which extends down to the sciatic notch. Since this cut is cortical, the fragment can be mobilized extensively and it allows placement of a graft and a better posterior coverage

Objective: Severe acetabular dysplasia with established dislocation of the hip represents a common problem in cerebral palsy. Once significant dysplasia is present little remodeling of the acetabulum occurs with femoral osteotomies alone. Pelvic osteotomies should address the problem of acetabular deficiency in order to restore optimal coverage of the femoral head. Standard innominate osteotomies are not recommended for neuromus-cular hip dysplasia. To address the lack of postero-lateral coverage in this population, a modified periacetabular osteotomy was performed. Methods: Between 1991 and 2000 a total of 44 patients (52 hips) with total body involvement CP underwent this procedure at a mean age of 9,4 yrs. The modification includes only one bicortical cut at the posterior corner at the sciatic notch. The cut extends down to the trira-diate cartilage, if present, and through the former site of the triradiate cartilage after closure of the acetabu-lar growth plate in adolescence. Additional procedures included: open reduction, femoral varus osteotomy, and soft tissue releases. Follow-up included a subjective and clinical evaluation. Radiographic assessment included measurements of the migration percentage and acetab-ular index, evidence of AVN, and premature closure of the triradiate cartilage. Results: The mean follow-up period for these patients was 3.5 years (1.0 to 8,1 yrs) after surgery, and 70% of the patients had reached skeletal maturity at that time. The median acetabular index improved from 30% pre-operatively to 18% at follow-up. The median migration percentage was 71% preoperatively, and 0 at follow-up. A re-dislocation occurred in 1 hip, and a re-subluxation in another. All other hips were stable and well contained at follow-up. There were 3 hips showing signs of postoperative femoral head defects . Premature closure of the triradiate cartilage was not noted. The caregivers had the impression that the surgery had improved personal care, positioning/transferring, and comfort. Conclusions: This osteotomy reduces the volume of the elongated acetabulum and provides coverage by articular cartilage. It provides coverage particularly at the posterior part of the acetabulum. Compared to other techniques this modified periacetabular osteotomy has only one posterior cortical cut which extends down to the sciatic notch. Since this cut is cortical, the fragment can be mobilized extensively and it allows placement of a graft and a better posterior coverage

Aims

What represents clinically significant acetabular undercoverage in patients with symptomatic cam-type femoroacetabular impingement (FAI) remains controversial. The aim of this study was to examine the influence of the degree of acetabular coverage on the functional outcome of patients treated arthroscopically for cam-type FAI.