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Background: Limiting the risk of dislocation is one of the main aims of both dual mobility and Lefèvre retentive cups. However, these devices have never been compared. The goal of our study was to compare these devices in total hip arthroplasty revisions for instability. The judgement criterion was non-recurrence of dislocation in a follow-up period of eight years., Methods: This retrospective case-control study compared two continuous paired series of total hip arthroplasty revisions for instability. These series included 63 patients and 159 patients with implantation of a Lefèvre retentive cup and a dual mobility cup, respectively., Results: The success rate at eight years (i.e., no recurrence) was 91 ± 0.05% and 95 ± 0.02% in the Lefèvre retentive cup and dual mobility groups, respectively. The difference was not statistically significant (p = 0.6)., Conclusion: It seems that the Lefèvre retentive cup provides comparable outcomes with the dual mobility cup in the total hip arthroplasty revisions for instability, avoiding recurrence in long term.

Eighty seven dislocations were seen in 1571 consecutive total hip replacements, mostly performed through a posterior approach. Nine occurred immediately after operation and most of the remainder within 5 weeks. In 26 cases further dislocation occurred, and in 11 patients another operation was required. The 87 dislocated hips have been compared with the remaining 1484. Factors predisposing to dislocation included revision operations, the experience of the surgeon and proper reconstruction of the abductor musculature. When the hip was deemed unstable at the end of an operation, dislocation occurred on 18 occasions out of 20 such cases. The position of the components in the dislocated hips was compared with that in 100 stable prostheses chosen by random sampling. A vertical acetabular prosthesis, and retroversion of the acetabular and femoral components all favoured dislocation. In 331 replacements with a 22 mm diameter head 29 dislocations were seen (8.7%), whereas in 168 replacements with 32 mm heads, 5 dislocations occurred (2.9%).

230 shelf operations were carried out between 1961 and 1985 for painful acetabular dysplasia or subluxation of the hip. 208 patients have been followed up for more than one year, with 79 for between 10 and 24 years. Substantial relief of pain was obtained in 88%. The benefits of operation usually continue for many years. Factors which may lead to a poor result are advanced age, dislocation of the hip and the presence of marked osteoarthritic changes. The results have been compared with those obtained for Chiari's osteotomy, and the relative indications for the two procedures are discussed.