Subsidence rate and long-term outcome of a calcar-guided short stem: A prospective 10-year follow-up study

Background : Several studies have reported good to excellent mid-term outcomes for various types of calcar-guided or metaphyseal-anchoring short stems. In our current long-term study, we investigated the subsidence rate of the optimys stem at 10-year follow, correlated the data with clinical outcome and identified potential risk-factors for failure. Methods : In our cohort we included 41 patients with 43 hips with an average age of 62.5 years and a minimum follow-up of ten years. Ein-Bild-Roentgen-Analyse (EBRA) was used to detect potential subsidence. Clinical outcome and complication rate were analyzed. Results : We found an average subsidence of 0.66 mm (SD 0.60) at 3 months, 0.92 (SD 0.88) at 12, 1.5 (SD 1.19) at 60 and 1.8 (SD 1.47) at 120 months respectively. We identified increased femoral offset (2.19mm vs 0.90 p = 0.0099) and head size (28, 0.34mm vs. 32 1.48 Vs. 36 2.50, p = 0.0052), as well as gender (female 1.21mm vs. male 2.35, p = 0.0067) as risk factors for increased subsidence. The amount of subsidence did not impact clinical outcome. Conclusions: The evaluated calcar-guided short stemshows an average subsidence of 1.8mm at 10-year follow up, with most pronounced subsidence within the first 3 months and stabilizing thereafter. In our study male gender and offset seem to be more susceptible to pronounced subsidence whereas this did not correlate with revision rate or inferior clinical outcome in terms of Harris Hip Score (HHS), patient satisfaction and pain. Trial registration: This prospective study was approved by the ethics commission board of northwest- and central- Switzerland (BASEC Nr 2023-00375).