Retrospective Study
Copyright ©The Author(s) 2025. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Orthop. Jun 18, 2025; 16(6): 107292
Published online Jun 18, 2025. doi: 10.5312/wjo.v16.i6.107292
Pure high-offset stems can cause an unexpected increase in femoral length in robotic-assisted primary total hip arthroplasty
Wei-Shao Tung, Aidin Eslam Pour, Johannes Sieberer, Claire A Donnelley, Steven M Tommasini, Daniel H Wiznia
Wei-Shao Tung, Aidin Eslam Pour, Johannes Sieberer, Claire A Donnelley, Steven M Tommasini, Daniel H Wiznia, Department of Orthopaedics and Rehabilitation, Yale University, New Haven, CT 06510, United States
Johannes Sieberer, Department of Mechanical Engineering and Material Science, School of Engineering and Applied Science, Yale University, New Haven, CT 06510, United States
Author contributions: Tung WS, Eslam Pour A, Sieberer J, Donnelley CA, Tommasini SM, and Wiznia DH contributed to the study design, data acquisition and analysis, drafting, and final approval of the manuscript; and all authors thoroughly reviewed and endorsed the final manuscript.
Institutional review board statement: This study was approved by the Medical Ethics Committee of Yale University, approval No. 2000032304.
Informed consent statement: Informed consent was obtained from all individual participants included in the study, as required by the Institutional Review Board.
Conflict-of-interest statement: All the authors report no relevant conflicts of interest for this article.
Data sharing statement: Not Applicable.
Open Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: https://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Wei-Shao Tung, Research Fellow, Department of Orthopaedics and Rehabilitation, Yale University, No. 47 College Street, New Haven, CT 06510, United States. weishao.tung@gmail.com
Received: March 30, 2025
Revised: April 17, 2025
Accepted: May 24, 2025
Published online: June 18, 2025
Processing time: 82 Days and 22.9 Hours
Abstract
BACKGROUND

Certain implant combinations change leg length and offset in primary total hip arthroplasty (THA). Poor restoration of leg biomechanics is a frequently cited reason for patient dissatisfaction following primary THA. A pure high-offset stem should provide direct lateralization without affecting femoral length when compared to a standard stem. However, clinical experience with preoperative planning software based on computed tomography-based three-dimensional-models reveals that using pure high-offset stems in THA may cause a difference between expected (no change in femoral length) and actual (small increase) in postoperative femoral length.

AIM

To elucidate the causes of these femoral length discrepancies using preoperative planning software.

METHODS

Preoperative templating for 43 robotic-assisted THAs, optimizing acetabular size and orientation, center of rotation, stem size and offset, and prosthetic head diameter were obtained. The preoperative planning software was used to calculate differences between preoperative and postoperative femoral length for standard and pure high-offset stems, unique to each patient.

RESULTS

Whilst the increase in femoral length between standard and high-offset stems was not significant (P = 0.93), 35 femurs (81.4%) experienced a 1-mm increase, and 3 (7.0%) experienced a 2-mm increase in femoral length while using high-offset stem compared to the standard stem. The incidence of femoral length increase was lower for patients with shorter femurs (18/22; 81.8%) compared to patients with longer femurs (20/21; 95.2%).

CONCLUSION

When pure high-offset stems were used in preoperative planning software, we demonstrated an unexpected increase in leg length between 1-2-mm in 88.4% of patients. This unexpected increase in femoral length is due to a function of the preoperative planning software’s planned stem alignment with the anatomical axis, and not an inherent fault in the stem design. With expanding accessibility of robotic-assisted THA platforms, all potential sources of postoperative leg length discrepancy should be identified during preoperative templating and necessary alterations to the surgical plan should be made to accommodate this unexpected difference when using a pure high-offset stem.

Keywords: Three-dimensional modelling; Total hip arthroplasty; Robotic-assisted surgery; Leg length; Anatomical mechanical femoral angle

Core Tip: Discrepancies in leg length can result in patient dissatisfaction, complications, or even a need for revision. Surgeons should be aware of this unexpected increase in femoral length when using a pure high-offset stem in robotic-assisted total hip arthroplasty, especially for patients who may benefit from precise restoration of lower extremity biomechanics. With expanding accessibility of computer-navigated and robotic-assisted total hip arthroplasty platforms, any potential sources of postoperative leg length discrepancy should be identified during preoperative templating and necessary alterations to the surgical plan should be made to accommodate this unexpected difference when using a pure high-offset stem.