Neck-sparing short femoral stems: A meta-analysis

Neck sparing short femoral stems are supposed to ease restoration of the proximal femoral anatomy and physiological hip biomechanics. This stem design is of particular interest as they have the potential to generate prosthetic hips that have higher functional performance with an improved lifespan, and revise more easily. Unlike previously published meta-analysis, this meta-analysis was initiated to determine if neck sparing short femoral stems compared to conventional stems: (1) resulted in improved functional performance; (2) reduced risk of thigh pain; (3) reduced risk of reoperation/revision, and 4) reduced stress shielding related bone loss in the proximal femur.

Literature databases were searched between 1st January 2005 and 30th March 2019. The primary search was conducted using the electronic databases MEDLINE, EMBASE, PubMed, Open Grey, Trip Pro, Evidence Search, and Cochrane. Eligible studies were assessed for homogeneity, with continuous outcomes expressed as standardized mean difference with 95% confidence interval and dichotomous data as odds-ratio with 95% confidence interval.

Ten randomised clinical trials were eligible; these trials included 1259 total hip arthroplasty procedures, inclusive of 616 neck sparing short stems and 643 conventional stems. We were not able to find a significant functional advantage of using neck sparing short stems based on Harris Hip scores (0.0850; 95% CI: -0.03 to 0.20 [p=0.40]) and WOMAC scores (-0.0605; 95% CI: -0.03 to 0.15 [p=0.87]). We found a trend in favour of neck sparing short stems to reduce the risk of thigh pain but this was non significant (odds ratio of 0.11; 95% CI: 0.03 to 0.43 [p=0.178]). Neck sparing short stems were associated with similar early- to mid-term dislocation and revision rates compared to conventional stems with odds ratio of 1.435 (95% CI: 0.545 to 3.780 [p=0.968]) and of 0.581 (95% CI: 0.220 to 1.532 [p=0.972]), respectively. Neck sparing short stems were found to have less bone loss in both Gruen zones 1 and 7 (3.324; 95% CI: -7.683 to 1.036 [p<0.001], and of -4.632; 95% CI: -9682 to 0.418 [p<0.001], respectively).

Neck sparing short femoral stems achieve excellent early to mid-term outcomes in both clinical and radiological outcome scores that are in keeping with conventional stems functionally. Hitherto, results from this meta-analysis suggest that neck-sparing stems may achieve better maintenance of bone mineral density than their conventional counterparts, in addition to fewer cases of thigh pain.

I; meta-analysis.