Use of Short Femoral Stems in Primary Total Hip Arthroplasty: A Mid-Term Safety Analysis: Prospective series of 5,876 cases at 4.4-year average follow-up.

Introduction To date, no national registry has provided a dedicated report on short femoral stems (SFS) in primary Total Hip Arthroplasty (pTHA). In the historical SOFCOT hip arthroplasty multicentre registry (HAMR, now RENACOT), the first SFS used in pTHA was registered in 2011. Aims of this specific report are: 1) to evaluate the outcome of SFS-pTHAs after 13 years (2011-2023) of monitoring and, 2) to evaluate concerns regarding the increasing use of these femoral implants in older patients.Hypothesis This multicentre study indicates that use of SFS in pTHA is safe at mid-term in a French orthopaedic community.Material & Methods As of December 31, 2023, a total of 5,876 SFS-pTHAs were registered, mostly for primary osteoarthritis (4,866, 82.8%). The mean patient age was 68.7 years (SD, 11.4) with a slight female majority (3,046, 52%). Of the 14 registered SFS brands, only one (489 AMIStem C™/5,876 hips, 8.3%) was cemented. Among 733 revisions linked to a previously registered pTHAs after an average follow-up (FU) of 4.7 years, 64 (8.7%) were SFS-THAs, including 59 cementless and 5 hybrids (stem cemented) constructions. SFS performance was assessed by calculating the revision percent observed component year (Rp100ocy, with an alert threshold if >1.3) and by comparing SFS and conventional femoral stems (CFS) using Kaplan-Meier (KM) cumulative revision risk estimates.Results The leading causes of early revision among the 64 SFS-rTHAs were hip dislocation (17/64, 26.6%), periprosthetic fractures (11/64, 17.2%), aseptic loosening (10/64, 15.6%), and acute deep infection (7/64, 10.9%). The Rp100ocy for cementless and cemented SFS-pTHAs was 0.25 (95%CI: 0.19-0.31) at 4.4 years, and 0.24 (95%CI: 0.10-0.57) at 4.2 years, respectively. At 10 years, cumulative revision rates by KM were: 1 (95% CI: 0.4-2.5) for cemented SFS-THA, 1.3 (95% CI: 1.1-1.5) for cemented CFS, 1.4 (95% CI: 1.1-1.9) for cementless SFS, and 1.9 (95% CI: 1.7-2.1) for cementless CFS. The overall Rp100ocy for SFS-pTHAs was 0.246 (CI: 0.193-0.315) at 4.4 years, and 0,245 for CFS-pTHAs (CI: 0.227-0.264) at a 1-year longer follow-up (5.5 years). The revision risk for periprosthetic fracture was 17.2% (11/64) for SFS and 24.5% (164/669) for CFS-pTHAs, that is not significant (p = 0.2).Discussion Dislocation was the primary reason for revision in this SFS-pTHA series, despite the use of dual mobility cups (DMC) in 36.7% of primary cases, followed by periprosthetic fracture. Ten-year survival of SFS-pTHAs is comparable to that of CFS-pTHAs. This 13-year multicenter monitoring raises no significant concerns regarding SFS use in pTHA, even with increasing use in older patients.Level Of Evidence III; prospective comparative study.