Influence of stem length on sagittal alignment in total hip arthroplasty: a comparison between short and standard stems.

Background: Total hip arthroplasty (THA), a critical surgery for hip joint pain relief and mobility restoration, involves careful consideration of various factors, including stem length. Short stems are often chosen for their potential to reduce tissue damage and thigh pain. Precise alignment is necessary to alleviate complications such as stem loosening and fractures. We aimed to compare intramedullary insertion freedom and alignment changes between short and standard stems in THA. This study is based on preoperative planning simulations, highlighting the potential clinical implications.

Methods: This retrospective study involved 102 hip joints (34 each from Dorr A, B, and C) undergoing initial THA between 2015 and 2017. A preoperative computed tomography scan was used to create three-dimensional bone models for planning virtual surgery, assessing stem insertion in flexion/extension, and measuring the anterior femoral offset. One-way repeated-measures analysis of variance was conducted to compare intramedullary insertion freedom and anterior femoral offset across the three Dorr classifications (A, B, and C). A paired t-test was used to compare intramedullary insertion freedom and anterior femoral offset between short and standard stems for each Dorr classification and between different medullary shapes.

Results: Statistically significant differences were observed between the stem types (p < 0.05). Short stems demonstrated significantly greater intramedullary insertion freedom, with averages of 7.5°, 8.2°, and 9.1° for Dorr A, B, and C, respectively, compared with 4.3°, 5.0°, and 5.8° for standard stems. Additionally, the anterior femoral offset was significantly higher in short stems, with an average increase of 2.5 mm across classifications, compared to 1.2 mm in standard stems (p < 0.05).

Conclusion: Short stems offer enhanced intramedullary insertion freedom and improved anterior femoral offset, potentially leading to better alignment outcomes in THA. However, their increased freedom necessitates precise surgical planning, particularly in patients with wider medullary morphologies. These findings emphasize the importance of simulation-based planning in understanding the impact of stem length, while clinical studies are needed to validate these results.