2025 ISAKOS Biennial Congress ePoster
Support Instruments Provide Remarkable Stability in Medial Closed Wedge Distal Femoral Osteotomy -A Finite Element Analysis-
Umito Kuwashima, MD, PhD, Tokyo JAPAN
Masafumi Itoh, MD, PhD, Tokyo JAPAN
Junya Itou, MD, PhD, Tokyo JAPAN
Ken Okazaki, MD, PhD, Tokyo JAPAN
Department of Orthopaedic surgery, Tokyo Women's Medical University, Tokyo, JAPAN
FDA Status Not Applicable
Summary
This study provided that the support instruments, both screws and plates, provided stability to the hinge site and reduced the equivalent stress of the main plate in MCWDFO with hinge fracture.
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Abstract
Objectives: Medial closed wedge distal femoral osteotomy (MCWDFO) is an effective treatment for valgus osteoarthritis of the knee with femoral deformity. However, lateral hinge fracture may increase the risk of non-union and loss of correction. Few studies have assessed the mechanical impact of hinge fracture in MCWDFO. The aim of this study was to evaluate the influence of hinge fracture and support instruments on MCWDFO using finite element analysis.
Methods
Computed tomography (CT) data of patients with knee osteoarthritis who had undergone CT scanning at our institute were adopted. Five femur models were developed using Mechanical Finder 11.0 FEA software (Research Centre of Computational Mechanics Inc.). This study was approved by the Institutional Ethics Commission, and informed consent was obtained. We produced a 1 mm osteotomy gap as a simulated postoperative bi-plane MCWDFO. A load of 2,400 N was applied to the femoral head at an angle of 15° relative to the femoral axis, and a load of 1,200 N was applied to the greater trochanter at an angle of 20°. We simulated the following models: only a medial locking plate (MLP) (group A); an MLP with a lateral support screw (group B); and an MLP with a lateral support plate (group C). The equivalent stress around the hinge was evaluated and the percentage of the plastic deformation zone was calculated for the hinge area in the no-hinge fracture model. The equivalent stress of the MLP and the degree of displacement were calculated using the hinge fracture model. Data normality was checked using the Kolmogorov–Smirnov test. Repeated measures ANOVA was performed using a paired t-test (Bonferroni correction) to compare the three groups. A p-value of <0.05 was considered indicative of statistical significance.
Results
The percentages of the plastic deformation zone in groups A, B, and C were 18.0 ± 11.7%, 3.3 ± 2.4%, and 2.3 ± 2.8%, respectively. The percentages tended to be lower in groups B and C than in group A, although there were no significant differences between the groups. In the hinge fracture model, the mean equivalent stress of the MLP in group C was significantly less than that in group A (p < 0.05).
In terms of the mean degree of displacement, group A showed more than 1 mm of displacement, which was significantly larger than that of the other groups (p < 0.05).
Discussion
This study provided that the support instruments, both screws and plates, provided stability to the hinge site and reduced the equivalent stress of the main plate in MCWDFO with hinge fracture. These instruments could also notably limit plastic deformation at the hinge area in the intact hinge model. No significant difference was observed between the two instruments in terms of stability. Surgeons should consider additional support fixation when hinge fractures are suspected in MCWDFO.