JOA - 2026-04-15 - Journal Article
Calcar Resorption is Commonly Seen with a Modern Triple-Tapered Collared Stem in Primary Total Hip Arthroplasty.
Fox JA, Ingawa HS, Newby JB, Chandrashekar AS, Vesperman RI, Browne JA, Pelt CE, Martin JR
Topics
Key Takeaway
79.1% of patients receiving a triple-tapered collared cementless stem in primary THA demonstrated calcar resorption, with mean calcar width decreasing from 5.9 mm to 3.3 mm at mean 2.3-year follow-up.
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Summary
This two-institution retrospective study examined calcar remodeling patterns in 182 patients undergoing primary direct anterior THA with a triple-tapered collared cementless stem at minimum one-year follow-up. Calcar resorption occurred in 144/182 patients (79.1%), with mean calcar width decreasing from 5.9 mm to 3.3 mm and mean collar overhang increasing from 0.8 mm to 3.4 mm. These findings indicate that despite collar presence, metaphyseal fixation dominates and the collar provides minimal sustained load transfer to the calcar after osseointegration.
Key Limitation
The absence of a collarless stem comparator group makes it impossible to determine whether the observed calcar resorption rate or magnitude differs meaningfully from that seen with equivalent collarless designs.
Original Abstract
INTRODUCTION
The impacts of load transfer between the collar of modern triple-tapered collared hip stems and the femoral calcar remain unknown. The aim of this study was to determine whether the calcar remodels in response to stress loading or stress shielding in the setting of a well-fixed modern triple-tapered collared stem.
METHODS
We conducted a retrospective review of patients from two institutions who underwent primary direct anterior total hip arthroplasty using collared cementless stems, with a minimum one-year follow-up (n = 182). Statistical analyses were performed to determine associations between patients who demonstrated calcar resorption compared to those who did not. The mean follow-up was 2.3 years (range, one to 6.2), and the mean patient age was 64.2 years (range, 18 to 83).
RESULTS
Calcar remodeling, more specifically resorption, occurred in 144 of 182 patients (79.1%). In patients who had resorption, the mean initial postoperative calcar width was 5.9 mm (standard deviation (SD), 1.89), decreasing to a mean final width of 3.3 mm (SD, 1.84). The mean initial postoperative collar overhang was 0.8 mm (SD, 1.44), increasing to a mean final collar overhang of 3.4 mm (SD = 2.6).
CONCLUSION
Our results demonstrate that 79.1% of patients who undergo primary total hip arthroplasty (THA) with a well-fixed triple-tapered collared cementless stem exhibit calcar resorption in the form of both calcar thinning and increasing collar overhang. These findings suggest that collared stems primarily achieve metaphyseal fixation. While the collar may decrease axial and rotational forces early on, the collar likely provides minimal load transfer to the calcar with stem ingrowth. Clinical implications of calcar thinning in the setting of a collared stem are yet to be fully understood. Future study of this finding is warranted.