Dual mobility cup in revision total hip arthroplasty: dislocation rate and survival after 5 years.

BACKGROUND: Dislocation is a common complication of total hip arthroplasty (THA), particularly when performed as revision surgery. Dual mobility cups (DMCs) minimize the risk of instability when implanted during primary THA. However, their usefulness and survival in revision THA remain unclear. We therefore conducted a retrospective study to assess DMC stability and survival at a minimal follow-up period of 5years after revision THA. HYPOTHESIS: The dislocation rate associated with DMCs for revision THA is similar to that seen after primary THA. MATERIALS AND METHODS: Cup exchange with implantation of a DMC was performed in 71 patients (74 hips) between 2000 and 2007, for the following reasons: recurrent dislocation (n=22), aseptic loosening (n=38), and infection (n=14). The DMCs were cemented in 47 cases and cementless in 27 cases. The clinical variables (Merle d'Aubigné-Postel score and Harris Hip Score) and radiological findings were collected retrospectively from the medical records and compared with those obtained at the last follow-up visit. RESULTS: Of the 74 cases, 2 were lost to follow-up. At last follow-up, the mean Merle d'Aubigné-Postel score was 15.2 (11-18) and the mean Harris Hip Score was 80.4 (51-98). Of the 8 failures, 2 (2/72, 2.7%) were related to mechanical factors (1 case each of aseptic loosening and dislocation) and 6 were changed because of infection (recurrent infection, n=4). Mechanical failure was not linked to a specific reason for revision THA. A radiolucent line was visible in 4 cases but this finding was not associated with clinical manifestations. When failure was defined as cup revision for any non-infectious complication, 5-year implant survival was 99% (95% confidence interval, 93-100%). DISCUSSION: Use of a DMC in revision THA was associated with a slightly higher dislocation rate (1/72, 1.4%) than in primary THA, whereas 5-year survival was comparable. Cemented DMCs were not associated with a greater risk of loosening. CONCLUSION: DMCs are useful to decrease the risk of dislocation in revision THA performed for any reason. The low rate of loosening indicates that DMCs do not result in high stresses at the bone-implant interface. LEVEL OF EVIDENCE: IV, retrospective study.

Knee osteochondral fractures in skeletally immature patients: French multicenter study.

INTRODUCTION: Femoral or patellar osteochondral fractures complicating patellar dislocation are more frequently observed in adolescents than in adults. These incidental lesions of vulnerable joint cartilage are often neglected in the initial phase, which is regrettable given their good capacity for healing after repositioning. The objective of this study was to investigate the characteristics and analyze the results of repositioning these fractures in skeletally immature patients. MATERIAL AND METHODS: This retrospective multicenter study grouped 14 patients and knees (seven females). The mean age at the time of the accident was 12.9 years (range, 11.2-14.9 years) for the girls and 14 years (range, 12.2-15 years) for the boys. These fractures involved the lateral condyle in nine cases and the patella in five cases. The injury mechanism was secondary to demonstrated patellar dislocation (n=9) or a direct impact (n=4). In nine cases out of 14, a leisure sports accident was the cause. The injury was treated a mean 5.2 days (range, 0-20 days) after the accident. All of the detached fragments were repositioned surgically with screw fixation (n=5), resorbable pins (n=5), or pull-out suture (n=4). Biological glue was added for six patients. Patellar stabilization was associated during the same procedure in two cases. RESULTS: No postoperative complications were observed. The results at the mean follow-up of 30 months (range, 15-89 months) showed no revision for failure, with all of the fractures demonstrating union at the final examination. The mean IKDC 2000 subjective score was 88±6 (range, 79-98) out of 100 points. The subjective satisfaction level was very satisfied in two cases and satisfied in the 12 others. The final IKDC score was A for eight patients, B for five patients, and C for one patient. Three patients underwent secondary patellar stabilization surgery. CONCLUSION: Better knowledge of this fracture and attentive reading of the radiographic images of a knee with hemarthrosis should result in more frequent diagnosis of this condition and adapted treatment. Unexplained hemarthrosis in a context of trochlear dysplasia should be considered to be associated with an OCF until proof of the contrary. A fragment released in a weightbearing zone should ideally be repositioned within 10 days but remains possible at 2 months. It regularly provides bone union and good results in children.