No differences in clinical and radiographic outcomes between standard versus high offset collared stems for primary total hip arthroplasty at five years follow-up.

Purpose: To compare clinical and radiographic outcomes of propensity-matched patients undergoing THA using standard versus high offset stems at five years.

Methods: The authors retrospectively reviewed a consecutive series of primary THAs performed between 01/09/2015-31/12/2017 using a fully-hydroxyapatite coated collared stem, with either a standard (n = 365) or high (n = 110) offset. Outcomes collected included: modified Harris Hip Score (mHHS), Oxford Hip Score (OHS), Forgotten Joint Score (FJS), and radiographic measurements including limb length discrepancy (LLD), stem subsidence, and stem radiolucencies.

Results: Propensity score matching resulted in 80 hips per group. Preoperatively there were no significant differences in patient demographics, surgical data and radiographic measurements, except the standard offset group had significantly smaller femoral (40.0 ± 7.5 vs 48.4 ± 6.2, p < 0.001), acetabular (92. ± 6.3 vs 94.8 ± 7.3, p = 0.011) and global (132.0 ± 10.3 vs 143.2 ± 8.2, p < 0.001) offsets compared to the high offset group. At a minimum five years follow-up, there were no significant differences in mHHS (93.2 ± 11.0 vs 93.1 ± 10.6, p = 0.553), OHS (45.1 ± 4.1 vs 45.3 ± 4.6, p = 0.623), and FJS (85.1 ± 19.3 vs 82.7 ± 23.0, p = 0.910). There were also no differences in radiographic measurements, including LLD (1.5 ± 4.8 vs 1.1 ± 3.5, p = 0.537), stem subsidence (0% vs 0%, p = 1.000), and stem radiolucencies (severe: 6% vs 1%, p = 0.152).

Conclusion: The present matched-cohort study found no significant differences between standard versus high offset straight fully-hydroxyapatite coated collared stems for primary THA in terms of clinical and radiographic outcomes at five years. These findings may suggest that uncemented collared high offset stems are not associated with an increased risk of radiolucencies and loosening compared to uncemented collared standard offset stems.