A Retrospective Evaluation of Femoral Stem Subsidence in Patients undergoing Cementless Total Hip Replacement

Introduction: The purpose of this study was to evaluate and compare subsidence and factors that may contribute to subsidence in patients undergoing THR with the traditional BFX, collared BFX, and BFX lateral bolt femoral stems. We hypothesized that patients undergoing THR with the lateral bolt stem would experience less stem subsidence compared with patients receiving a traditional BFX or collared stem.

Materials and Methods: Radiographs of 68 hips undergoing THR were evaluated. Parameters measured included subsidence, canal flare index, stem canal fill, stem orientation, and complications detected on radiographs. A proportion based on actual stem length, radiographically measured stem length and radiographically measured stem position was used to correct measured stem position on the craniocaudal view. An ANOVA was used to compare subsidence and canal fill.

Results: The lateral bolt stem group experienced significantly less subsidence than the collared group (p = 0.018) and the BFX group (p = 0.004). There was no significant difference in subsidence between collared and BFX groups. A significant difference was identified in coronal CF between the BFX and collared groups (p = 0.031), and between all three groups for sagittal canal fill.

Discussion/Conclusion: BFX stems had the highest coronal canal fill but still experienced the greatest subsidence. Addition of a lateral bolt may increase implant resistance to subsidence in the presence of a slightly undersized femoral stem. We accept our hypothesis as patients undergoing THR with a lateral bolt stem experienced less stem subsidence compared with patients receiving a traditional BFX or collared stem.

Acknowledgement: There was no proprietary interest or funding provided for this project.

No conflict of interest has been declared by the author(s).