No clinical benefit of gender-specific total knee arthroplasty: A systematic review and meta-analysis of 6 randomized controlled trials

Background and purpose

There is no consensus regarding the clinical relevance of gender-specific prostheses in total knee arthroplasty (TKA). We summarize the current best evidence in a comparison of clinical and radiographic outcomes between gender-specific prostheses and standard unisex prostheses in female patients.

Methods

We used the PubMed, Embase, Cochrane, Science Citation Index, and Scopus databases. We included randomized controlled trials published up to January 2013 that compared gender-specific prostheses with standard unisex prostheses in female patients who underwent primary TKAs.

Results

6 trials involving 423 patients with 846 knee joints met the inclusion criteria. No statistically significant differences were observed between the 2 designs regarding pain, range of motion (ROM), knee scores, satisfaction, preference, complications, and radiographic results. The gender-specific design (Gender Solutions; Zimmer Inc, Warsaw, Indiana) reduced the prevalence of overhang. However, it had less overall coverage of the femoral condyles compared to the unisex group. In fact, the femoral prosthesis in the standard unisex group matched better than that in the gender-specific group.

Interpretation

Gender-specific prostheses do not appear to confer any benefit in terms of clinician- and patient-reported outcomes for the female knee.Women account for almost two-thirds of knee arthroplasties (Kurtz et al. 2007). Recently, a possible effect of gender on functional outcomes and implant survivorship has been identified (Vincent et al. 2006, Ritter et al. 2008, Kamath et al. 2010, Parsley et al. 2010, O’Connor 2011). Gender differences in the anatomy of the distal femur are well documented (Conley et al. 2007, Yue et al. 2011a, b, Yan et al. 2012, Zeng et al. 2012). Women tend to have a less prominent anterior condyle (Conley et al. 2007, Fehring et al. 2009), a higher quadriceps angle (Q-angle) (Hsu et al. 1990, Woodland et al. 1992), and a reduced mediolateral to anteroposterior aspect ratio (Chin et al. 2002, Chaichankul et al. 2011). Investigators have found that standard unisex knee prostheses may not equally match the native anatomy in male and female knees (Clarke and Hentz 2008, Yan et al. 2012). A positive association between the femoral component size and the amount of overhang was observed in females, and femoral component overhang (≥ 3 mm) may result in postoperative knee pain or reduced ROM (Hitt et al. 2003, Lo et al. 2003, Mahoney et al. 2010).The concept of gender-specific knee prostheses was introduced to match these 3 anatomic differences in the female population (Conley et al. 2007). It includes a narrower mediolateral diameter for a given anteroposterior dimension, to match the female knee more closely. Additionally, the anterior flange of the prothesis was modified to include a recessed patellar sulcus and reduced anterior condylar height (to ovoid “overstuffing” during knee flexion) and a lateralized patellar sulcus (to accommodate the increased Q-angle associated with a wider pelvis).Several randomized controlled trials (RCTs) have failed to establish the superiority of the gender-specific prosthesis over the unisex knee prosthesis in the female knee (Kim et al. 2010a, b, Song et al. 2012a, Thomsen et al. 2012, von Roth et al. 2013). In contrast, other studies have found higher patient satisfaction and better radiographic fit in the gender-specific TKAs than in the standard unisex TKAs (Clarke and Hentz 2008, Parratte et al. 2011, Yue et al. 2014). We therefore performed a systematic review and meta-analysis to compare the clinical and radiographic results of TKA in female patients receiving gender-specific prostheses or standard unisex prostheses.