[The reconstruction of extended acetabular bone defects in revision hip arthroplasty--risk factors for migration and loosening using the pedestal cup]

Review of the outcomes of complex acetabular reconstructions using a stemmed acetabular pedestal component

Aim

Until now, there has been no consensus as to whether stemmed acetabular components are appropriate for use in patients undergoing revision total hip arthroplasty (THA) who have major acetabular defects or pelvic discontinuity. We wished to address this deficiency in the literature.

Patients and Methods

We carried out a retrospective study of 35 patients (six men and 29 women) with a mean age of 68 years (37 to 87), with major acetabular defects who underwent revision THA between 2000 and 2012.

Results

At a mean follow-up of 63 months (24 to 141), a total of 15 patients (43%) had required at least one further operation. Six implants (17%) loosened aseptically, four (11%) were further revised for infection and two (6%) for technical failure. By taking revision for any reason as the endpoint, the rate of survival of the implant was 61% after five years; by taking revision for aseptic loosening as the end point, it was 78%. The cumulative five-year survival for aseptic loosening was 94% in patients without pelvic discontinuity, and 56% in those with pelvic discontinuity.

Conclusion

These results indicate a significantly worse survival in patients with pelvic discontinuity (p = 0.020) and we advise caution in the use of the pedestal component in patients with major acetabular defects and pelvic discontinuity who require revision THA. As a result of these findings we have stopped using this implant and prefer to use particulate bone grafts protected with an anti-protrusion cage and posterior column plate fixation, if necessary. Take home message: Based on these poor results, we advise caution if using the pedestal component in patients with major acetabular defects with the presence of a pelvic discontinuity. Cite this article: Bone Joint J 2016;98-B:772–9.

[Percutaneous iliosacral screw fixation for pelvis insufficiency fracture after implantation of a pedestal cup: case report]

Insufficiency fractures of the sacrum are frequently overlooked injuries especially in postmenopausal women with an osteoporotic bone structure and without a history of significant trauma. Plain radiographs are frequently inadequate in showing insufficiency fractures of the sacrum. Regarding this a fracture of a pubic ramus combined with appropriate clinical symptoms should raise the suspicion of a concomitant sacral injury. Therefore, further investigations including a CT scan are necessary.The case of an osteoporotic female patient with bilateral insufficiency fractures of the sacrum and a fracture of the right superior and inferior pubic ramus 5 weeks after primary total hip arthroplasty and implantation of a pedestal cup due to an intraoperative fracture of the right acetabulum is presented. To ensure early mobilization as well as avoidance of further concomitant morbidities a percutaneous iliosacral screw fixation was performed. This approach has been established as an operative treatment for minimally or non-displaced insufficiency fractures of the sacrum.

[Comparison of different cup revision systems]

Aseptic loosening of hip cups results in cranial and medial migration, which induces bone resorption and defects. Despite these defects, it is the aim in cup revision arthroplasty to get a stable fixation and a restoration of the hip center. Depending on the size of the defect, which can be classified by different scoring systems, various strategies requiring an experienced surgeon can be used to reach this aim. If defects are localized, bigger primary cemented or cement-free cups can be used. Larger defects may need bone transplantation or special designs such as oval cups or reinforcement rings. They can be used with or without plates in combination with cement for inlay fixation. In the case of bigger defects or pelvic discontinuity, modular systems or a socket cup may be necessary.

[Acetabular revision surgery with the oblong revision cup : clinical and radiological results of 217 cases]

BACKGROUND

Deficiencies of the acetabular bone stock are an increasing and challenging problem in revision hip surgery. The LOR oblong revision cup is a valuable option in revision hip surgery. The purpose of this study was to assess outcomes with the LOR revision cup in hips with acetabular bone deficiency, analyze the complications, and identify predictors of survival rate.

PATIENTS AND METHODS

From 1996 to 2002, 217 revision surgeries were performed with LOR cups. The mean patient age at operation was 67.5 years (range 29-87 years). The mean postoperative follow-up was 4 years (range 4-100 months). The patients were evaluated clinically and with the Harris hip score (HHS), UCLA score, and WOMAC index. A continuous radiographic assessment was done to detect heterotopic ossifications and radiolucencies or loosening on the basis of the Mayo hip score. Predictors of survival rate were estimated using Kaplan-Meier survivorship analysis.

RESULTS

Twenty-four patients (7.4%) died during the study period. Seven patients (3.1%) had revisions because of aseptic loosening and two patients (0.9%) because of infection. Clinical assessment at follow-up showed a significantly improved mean HHS from 45 points preoperatively to 78 points postoperatively. At the most recent follow-up, patients with a body mass index below 30 or those classified as Charnley A had a significantly better HHS. Because of migration on the latest radiographs, revision was indicated in 4.8% of the cases. The survival rate of all LOR implants based on implant removal was 96% after 40 months and 87% after 80 months. Based on radiographic evidence of loosened implants, the survival rate was 94% after 40 months and 79% after 80 months. Patients with more than two revisions had reduced implant survivorship compared with those having one or two revisions. The factors "age at operation", "gender", "obesity", "ASA score", "Charnley score", and "activity according to the UCLA score" did not influence the survival rate.

CONCLUSION

We recommend this component in revision surgery on the basis of satisfactory clinical and radiological results at a mean of 48 months of follow-up. We identified the number of revisions as a predictor of survival rate.