Background: Short-stem (SS) prostheses require less resection of the femoral neck, produce a more physiological load pattern in the proximal femur, reduce stress shielding, and aid bone conservation and are, therefore, beneficial for young patients. Conventional cementless implants in total hip arthroplasty (THA) have shown excellent clinical results; however, it is unclear whether SS prostheses can obtain the same clinical and radiological outcomes. We conducted a meta-analysis of randomized controlled trials (RCTs) to evaluate whether SS prostheses are superior to conventional implants after primary THA.
Methods: We reviewed the literature published up to June 2016 from PubMed, Web of Science, and the Cochrane Library to find relevant RCTs comparing SSs and conventional stems in primary THA. Quality assessment was performed by 2 independent reviewers. The RevMan 5.3 software program of the Cochrane Collaboration was used to analyze the data. Random- or fixed-effect models were used to calculate standardized mean differences (SMDs) and 95% confidence intervals (CIs) for each comparison.
Results: Six RCTs involving 552 patients with 572 hips were identified. Strong evidence indicated that SS prostheses were more effective for reducing thigh pain than conventional implants (I = 46%, P = 0.002; risk ratio [RR], 95% CI 0.15, 0.04-0.49). However, there were no significant differences between the 2 groups in Harris Hip Scores (I = 0%, P = 0.84; SMD, 95% CI 0.02, -0.15-0.18), Western Ontario and McMaster Universities Osteoarthritis Index Scores (I = 0%, P = 0.35; SMD, 95% CI 0.09, -0.10-0.27), femoral offset of stem (I = 0%, P = 0.57; SMD, 95% CI 0.06, -0.16-0.29), and leg-length discrepancy (I = 79%, P = 0.88; SMD, 95% CI 0.04, -0.44-0.51).
Conclusion: SS prostheses achieve the same clinical and radiological outcomes as conventional implants, and were superior in terms of reducing thigh pain. But whether the postoperative thigh pain applied in 2nd-generation cementless prosthesis still needs further large-scale multicenter studies with longer follow-up to confirm.