Outcome of short versus conventional stem for total hip arthroplasty in the femur with a high cortical index: a five year follow-up prospective multicentre comparative study

Background: The uncemented total hip arthroplasty (THA) has become the choice for many hip surgeons. Although conventional uncemented femoral components have a proven track record, there remain concerns about the rate of thigh pain, proximal stress shielding, and consequent loss of bone stock at revision surgery. Methods: Inclusion criteria were the following: patients between 50 and 85 years old undergoing primary THA with implant of short (group 1) or conventional (group 2) femoral stem and with femoral shape type A, according to Dorr classification. Clinical follow-up was registered using OHS, HHS, and Womac scores. The radiographic scans were evaluated in order to compare component positioning and bone remodeling at five year follow-up. Results: We included in the analysis 60 subjects in group 1 and 67 in group 2. No differences were registered between the groups comparing demographic and operative data. One case in group 1 (1.7%) and three cases in group 2 (4.5%) reported an intra-operative fracture. There was a significant improvement in the functional scores in both groups with no significant difference at final follow-up. The incidence of reported thigh pain at follow-up was 14.9% in group 2 and 3.3% in group 1 (p = 0.033). Radiographic analysis documented a difference in terms of stress shielding and thinning of medial and lateral cortex in favour of group 1. Moreover, patients of group 1 showed a higher varus angle at six month follow-up. Conclusion: In patients with high cortical index, a short stem shows better clinical and radiological outcomes at five year follow-up.