Slightly reduced early subsidence with similar outcomes and complications rate in collared stems - A systematic review of randomized clinical trials

Background: There is a growing trend towards using femoral stems with a medial calcar collar during total hip arthroplasty (THA). Purpose: Systematically review the literature comparing a femoral collared stem and femoral collarless stem on subsidence, patient-reported outcomes (PROs), and revision rate. Study design: Systematic Review, Level of Evidence 1. Methods: A literature search of Pubmed and Medline was according to Preferred Reporting Items for Systematic Reviews and Meta -Analyses guidelines. Randomized controlled trials that evaluated collared and collarless stems, subsidence and PROs for adult patients undergoing total hip arthroplasty (THA) were included. Additional data collection included patient demographics, stem-calcar contact, canal-fill ratio (CFR), stem orientation, surgical approach, Dorr Type, complications, and revisions. Results: Five studies met inclusion criteria. 674 patients (704 hips) were included. Mean patient ages ranged 58.5-72.4 years old, and mean BMI ranged 26.6-29.8 kg/m2. Mean reported follow-up of the included clinical trials ranged 1-9.6 years. Two studies reported mean early subsidence at two weeks postoperatively, which was 0.36, 0.99 mm for collared stems and 0.52, 3.22 mm for collarless stems, proving to be statistically significant (P = 0.023), (P = 0.05). All studies demonstrated improved PROs at most recent follow-up. Revision rates ranged from 4 to 11.3 %, but these were not statistically significant. Conclusions: Implantation of collared stems compared to collarless may reduce early post -operative subsidence, while no substantial effect on aseptic loosening, thigh pain, proximal femoral fracture, and revision is seen. When measuring patient-reported outcomes, the collared femoral stem was not superior to the collarless femoral stem as both resulted in similar improvement preoperatively to postoperative state.