Outcome of Revision Hip Arthroplasty for Instability: Risk Factors for Failure and Reoperation

Introduction: Postoperative instability after total hip replacement (THR) is a common complication with a rate of 1% to 28% after primary or revision total hip replacements, respectively. Several surgical options are available; however, few comparative studies report on these revision outcomes. The purpose of this study was to evaluate outcome of revision THR for instability and to specifically evaluate for risk factors associated with failure and reoperation.

Methods: A review of our database identified 402 revision THR procedures performed for recurrent instability with a minimum of two years of follow-up, or who were deceased more than one year after surgery. Failure was defined as an aseptic re-revision of the hip or recurrent dislocation. Multivariate proportional hazard model was constructed to predict treatment failure. Results are reported as hazard ratio (HR) and its 95% confidence interval (95% CI).

Results: The analysis included 387 operations, of these 91 (22.6%) had aseptic revision or recurrent dislocation. Most failures identified were: 65 (71.4%) failures were re-revisions due to dislocation and 11 (12.1%) due to dislocation with no re-revision surgery.

Multivariate analysis identified the following factors as significant for increased risk of failure; the use of fully constrained liner (HR=1.77, 95%CI=1.009-3.121, p=0.046), augmented liners (lipped, oblique and high offset liners, HR=1.833, 95% CI=1.130-2.974, p=0.014), periprosthetic fracture of the femur (HR=2.743, 95%CI=1.33-5.644), age over 65 (HR=0.672, 95%CI=0.436-1.035, p=0.071), and pelvic discontinuity requiring the use of a cage (HR=3.216, 95%CI=1.452-7.121, p=0.003). In patients with abductor dysfunction the use of a focal constrained liners was found to decrease the risk of failure (HR=0.147, 95%CI=0.020-1.079, p val=0.059).

Discussion and Conclusions: It has been shown that fully circumference and augmented liners (lipped, oblique or high offset liners) are associated with the highest failure rates. Focal constrained liners might offer a good alternative for abductor deficient patients.