TOTAL HIP ARTHROPLASTY: TREATMENT OF CHRONIC INSTABILITY USING A DOUBLE-MOBILITY CUP

Abstract

Purpose: Dislocation of total hip arthoplasties is a sad reality. The incidence of this complication is estimated from 0.6 to 8%. Dislocation can be a single event that never recurs, but half of all dislocations will reoccur again. We analysed outcome after treating chronically unstable total hip arthroplasties using a double-mobility cup.

Material and methods: Between 1990 and 2000, we treated 42 cases of recurrent dislocation of total hip arthroplasties. Five were immediate, 33 early, and four late; five dislocations on the average. The prosthesis was implanted via the posterolateral approach for 36 patients. Thirteen patients treated in our unit had already had surgical treatment for chronic instability: 1 trochanteoplasty, 8 bone blocks, 5 restraining cups. A standing AP view of the pelvis was obtained in all patients before surgery to analyse shortening (gluteus medius insufficiency), cup tilt and anteversion, and stem lateralisation. Likewise a CT scan was performed systematically to analyse stem and cup anteversion. No position anomaly was found in 17 patients; at least one anomaly was found in the others. All patients were reoperated via the posterolateral approach. A double-mobility cup was implanted systematically without changing the stem.

Results: Among the 42 patients, we had two with recurrent dislocation, one in a neurologic patient and one in a patient with major anomalies in the position of the femoral component that was not changed. The incidence of recurrent dislocation was thus 4.75%.

Discussion: The therapeutic method used here can be compared with other solutions (trochanteroplasty, anti-dislocation crescent, antidislocation bone block, bipolar replacement). The double-mobility cup is particularly interesting for high-risk patients: neck fracture, tumour surgery, neurological disease, antecedent non-prosthetic surgery (dearthrodesis prosthesis). We advocate revision surgery after three dislocations.

Conclusion: The double-mobility cup appears to be a valid therapeutic option, both for the treatment and prevention of chronic instability of total hip arthroplasty.