CT-based simulation of impingement-free mechanical hip motion after unilateral total hip arthroplasty.
4 affiliations
- 1Center for Frontier Medical Engineering, Chiba University, 1-33 Yayoi-cho, CFME room#B201, Inage-ku, Chiba, 263-8522, Japan.
- 2Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba city, 260-0856, Japan. [email protected].
- 3Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba city, 260-0856, Japan.
- 4Department of Orthopedic Surgery, Toho University Sakura Medical Center, 564-1 Shimoshizu, Sakura, 285-8741, Japan.
Abstract
Background
Range of motion (ROM) after total hip arthroplasty (THA) is influenced by implant-related parameters such as femoral head diameter, neck length, and stem offset. However, the quantitative effects of these parameters on ROM, leg length discrepancy (LLD), and femoral offset discrepancy remain unclear. This study aimed to quantify the effects of implant-related parameters on simulated impingement-free mechanical ROM after unilateral THA.Methods
A computed tomography (CT) -based three-dimensional (3D) simulation was performed in 100 patients who underwent unilateral THA with a clinically and radiographically healthy contralateral hip. The contralateral healthy hip was also evaluated as a patient-specific comparator. Implant configurations were simulated by varying femoral head diameter, neck length, and stem offset. Femoral head diameters of 36 mm and 32 mm, neck lengths from - 3.5 mm to + 7 mm, and standard-offset and lateral-offset stems were evaluated. Simulated impingement-free mechanical ROM was assessed in maximum flexion, maximum extension, internal rotation at 90° of flexion, and external rotation at 10° of extension. Simulated LLD and femoral offset discrepancy relative to the contralateral healthy hip were also quantified.Results
Increasing neck length improved simulated mechanical ROM in all evaluated directions, with median increases of 6.3° in flexion and 5.3° in extension for every 3.5-mm increment. Lateral offset stems further increased flexion by 16.3° compared with standard stems. Femoral head enlargement from 32 mm to 36 mm modestly improved simulated mechanical ROM, increasing flexion by approximately 2.5°. However, neck lengthening increased LLD by a median of 2.3 mm per 3.5-mm increment. The contralateral healthy hips showed median simulated ROM values of 119° in flexion, 66° in extension, 31° in internal rotation, and 48° in external rotation.Conclusions
Increasing neck length and lateral offset improved simulated impingement-free mechanical ROM after unilateral THA, whereas neck lengthening increased LLD. Femoral head enlargement also improved simulated mechanical ROM, but its effect was limited compared with those of neck length and stem offset. The contralateral healthy hip may provide contextual patient-specific information for interpreting simulated mechanical ROM in unilateral THA.
Related
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BibTeX
@article{kazuma2026ctbased,
title = {{CT-based simulation of impingement-free mechanical hip motion after unilateral total hip arthroplasty.}},
author = {Bando Kazuma and Nakamura Junichi and Hagiwara Shigeo and Kawarai Yuya and Ohtori Seiji and Orita Sumihisa},
journal = {BMC musculoskeletal disorders},
year = {2026},
month = jul,
doi = {10.1186/s12891-026-10311-3},
url = {https://europepmc.org/article/MED/42958240},
note = {CC BY},
}
RIS
TY - JOUR
TI - CT-based simulation of impingement-free mechanical hip motion after unilateral total hip arthroplasty.
AU - Bando Kazuma
AU - Nakamura Junichi
AU - Hagiwara Shigeo
AU - Kawarai Yuya
AU - Ohtori Seiji
AU - Orita Sumihisa
PY - 2026
DA - 2026/07/31
JO - BMC musculoskeletal disorders
DO - 10.1186/s12891-026-10311-3
UR - https://europepmc.org/article/MED/42958240
AB - Background Range of motion (ROM) after total hip arthroplasty (THA) is influenced by implant-related parameters such as femoral head diameter, neck length, and stem offset. However, the quantitative effects of these parameters on ROM, leg length discrepancy (LLD), and femoral offset discrepancy remain unclear. This study aimed to quantify the effects of implant-related parameters on simulated impingement-free mechanical ROM after unilateral THA.Methods A computed tomography (CT) -based three-dimensional (3D) simulation was performed in 100 patients who underwent unilateral THA with a clinically and radiographically healthy contralateral hip. The contralateral healthy hip was also evaluated as a patient-specific comparator. Implant configurations were simulated by varying femoral head diameter, neck length, and stem offset. Femoral head diameters of 36 mm and 32 mm, neck lengths from - 3.5 mm to + 7 mm, and standard-offset and lateral-offset stems were evaluated. Simulated impingement-free mechanical ROM was assessed in maximum flexion, maximum extension, internal rotation at 90° of flexion, and external rotation at 10° of extension. Simulated LLD and femoral offset discrepancy relative to the contralateral healthy hip were also quantified.Results Increasing neck length improved simulated mechanical ROM in all evaluated directions, with median increases of 6.3° in flexion and 5.3° in extension for every 3.5-mm increment. Lateral offset stems further increased flexion by 16.3° compared with standard stems. Femoral head enlargement from 32 mm to 36 mm modestly improved simulated mechanical ROM, increasing flexion by approximately 2.5°. However, neck lengthening increased LLD by a median of 2.3 mm per 3.5-mm increment. The contralateral healthy hips showed median simulated ROM values of 119° in flexion, 66° in extension, 31° in internal rotation, and 48° in external rotation.Conclusions Increasing neck length and lateral offset improved simulated impingement-free mechanical ROM after unilateral THA, whereas neck lengthening increased LLD. Femoral head enlargement also improved simulated mechanical ROM, but its effect was limited compared with those of neck length and stem offset. The contralateral healthy hip may provide contextual patient-specific information for interpreting simulated mechanical ROM in unilateral THA.
SN - 1471-2474
ER -