Early proximal migration of cups is associated with late revision in THA: a systematic review and meta-analysis of 26 RSA studies and 49 survivalstudies

Abstract

Background and purpose: The association between excessive early migration of acetabular cups and late aseptic revision has been scantily reported. We therefore performed 2 parallel systematic reviews and meta-analyses to determine the association between early migration of acetabular cups and late aseptic revision.

Methods: One review covered early migration data from radiostereometric analysis (RSA) studies, while the other focused on revision rates for aseptic loosening from long-term survival studies. Thresholds for acceptable and unacceptable migration were classified according the Swedish Hip Arthroplasty Register and the Australian National Joint Replacement Registry: < 5% revision at 10 years.

Results: Following an elaborate literature search, 26 studies (involving 700 cups) were included in the RSA review and 49 studies (involving 38,013 cups) were included in the survival review. For every mm increase in 2-year proximal migration, there was a 10% increase in revision rate, which remained after correction for age, sex, diagnosis, hospital type, continent, and study quality. Consequently, proximal migration of up to 0.2 mm was considered acceptable and proximal migration of 1.0 mm or more was considered unacceptable. Cups with proximal migration of between 0.2 and 1.0 mm were considered to be at risk of having revision rates higher than 5% at 10 years.

Interpretation: There was a clinically relevant association between early migration of acetabular cups and late revision due to loosening. The proposed migration thresholds can be implemented in a phased evidence-based introduction, since they allow early detection of high-risk cups while exposing a small number of patients.

Figure 1.

PRISMA flow chart of both reviews. Details of the 13 PF can be found in Table 1. RSA: radiostereometric analysis; THP: total hip prosthesis; FU: follow-up; PF: combination of prosthesis type and fixation method.

Figure 2.

Scatter plot showing association between 2-year proximal migration in mm and revision rate for aseptic loosening of the acetabular cup at 10 years, as a percentage. The colored lines were derived from weighted regression according to match quality, survival study quality, and RSA study quality (the coefficients and 95% CIs are given in Table 2).

Figure 3.

Scatter plot showing the relation between 2-year proximal migration and revision of the acetabular cup for aseptic loosening at 10 years. The thresholds of 0.2 mm and 1.0 mm for the three categories (acceptable, at risk, and unacceptable) are shown.

Figure 4.

Dot chart showing the pooled 2-year proximal migration ranked by the pooled 10-year revision rate for each PF: combination of prosthesis type and fixation method. The unacceptable PFs (based on their migration pattern) have been abandoned, with the Wagner cup having the worst recorded survival in the Swedish Register (Ahnfelt et al. 1990). A detailed description of each PF is given in Table 1. R10(%) is the pooled revision rate at 10-year follow-up, in percent; NA: not available. *This a best-case scenario for the Wagner cup, since the reference scene was not made directly postoperatively. Thus, the actual 2-year proximal migration is more than the observed value presented here. ** The Birmingham Hip Resurface (BHR) prostheses of the RSA study were implanted by the developer, so the migration results (and “acceptable” classification) may not apply to non-developers.