Do modular tapered long stems differ in stability and function? A prospective comparison of two stems in complex femoral revision THA.

Abstract

Background: Revision total hip arthroplasty (rTHA) in the setting of substantial proximal femoral bone loss is technically challenging. Modular tapered fluted stems provide predictable diaphyseal fixation while allowing independent adjustment of version, offset, and limb length. Among these, two commonly used systems-modular tapered fluted stem Type A (Revitan^™) and Type B (LIMA Modulus^™)-have limited direct comparative evidence. This study aimed to prospectively compare radiographic stem subsidence (primary outcome), as well as functional outcomes, complications, survivorship, and secondary outcomes, between Type A and Type B modular long stems in femoral rTHA.

Methods: In this single-center randomized prospective study, 110 patients undergoing femoral revision rTHA were randomly assigned to receive either Type A (n = 55) or Type B (n = 55) stems. All procedures were performed by experienced revision surgeons under standardized perioperative and rehabilitation protocols. Radiographs were analyzed for stem subsidence, osseointegration, and limb-length restoration. Functional outcomes were assessed using the Harris Hip Score (HHS), Oxford Hip Score (OHS), and European Quality of Life Visual Analogue Scale (EQ-VAS) at baseline and final follow-up (mean 61.4 months). Complications and stem survivorship were recorded prospectively. Statistical analysis included paired and unpaired comparisons, correlation, regression, and Kaplan-Meier survival estimates.

Results: Baseline demographics and femoral defect severity were comparable. Both groups achieved high radiological stability, with mean distal subsidence of 1.3 ± 0.7 mm (Type A) and 1.5 ± 0.9 mm (Type B; p = 0.24), and osseointegration in > 92% of cases. Limb-length and offset restoration were similar. HHS improved significantly in both groups (Type A: 44.7 → 88.1; Type B: 45.1 → 87.3; p < 0.001), with > 80% achieving good-to-excellent outcomes. Complication rates were low and comparable. Five-year stem survivorship was 98.2% (Type A) and 97.6% (Type B). Early full weight-bearing and lower Paprosky defect grades independently predicted superior functional outcomes, whereas stem type did not.

Conclusions: Both Type A and Type B modular tapered fluted stems demonstrated durable fixation, minimal subsidence, low complication rates, and excellent mid-term functional recovery. Radiographic stem subsidence did not differ between groups, indicating that design variations do not significantly affect clinical outcomes. These findings support the use of modular tapered fluted stems as reliable solutions in complex femoral rTHA.