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Objectives and questions: The influence of femoral offset on the survival of cementless femoral stems in total hip arthroplasty (THA) remains unclear. This study aimed to evaluate the influence of total femoral offset (TFO – stem + head) on the risk of revision for early aseptic femoral loosening (AFL) and all-cause revision (ACR).

Material and methods: A retrospective cohort study was conducted using data from the Swiss National Implant Registry (SIRIS) for all primary, cementless THAs performed for osteoarthritis between 2012 and 2024 with the five most common stem designs. The final cohort consisted of 93,027 hips. The primary exposure was TFO, analyzed as both a continuous variable and as three categories (<42 mm, 42–48 mm, and >48 mm). The primary endpoint was revision surgery for AFL, and the secondary endpoint was ACR. Kaplan-Meier survival analyses and multivariable Cox proportional hazards models were used to estimate survival and hazard ratios (HRs) while adjusting for confounders.

Results: A total of 419 revisions for AFL and 2,592 for ACR were observed. The 10-year implant survival for AFL was significantly lower in the high-offset group (98.9%, 95% CI 98.6–99.1%) compared to the standard (99.3%, 95% CI 99.2–99.4%) and low-offset groups (99.5%, 95% CI 99.4–99.6%; p < 0.001). After adjusting for confounders, the risk of revision for AFL increased by 4.1% for every 1-mm increase in TFO (HR 1.04, 95% CI 1.02–1.06). The high-offset group (>48 mm) had a significantly increased risk of revision for AFL (HR 1.83, 95% CI 1.28–2.63) and ACR (HR 1.20, 95% CI 1.04–1.38). Most common causes of revision Infection 23.7%. Aseptic femoral loosening 14.5%. Femoral periprosthetic fracture Vancouver type B 12.2%. Dislocation/instability 11.9%. Leg length discrepancy due to acetabular malposition 7.9%.

Discussion and conclusions: In this registry population, higher TFO combinations are associated with an 83% and 20% increased risk of revision for aseptic femoral loosening and a risk of all-cause revision, following cementless THA. Collars were associated with a 50% reduction in revision risk.