Document Type : RESEARCH PAPER
Authors
1
Center for Orthopedic Trans-disciplinary Applied Research (COTAR), Tehran University of Medical Sciences, Tehran, Iran
2
Department of Orthopedic Surgery, Denver Health Medical Center, Denver, United States
3
Fellowship of Knee, Sport and Reconstruction Surgery, Department of Orthopedic Surgery, Shariati Hospital, Tehran University of Medical Sciences, Tehran, Iran
4
Orthopedics and trauma surgery department, Shariaty Hospitals, Tehran University of Medical Science, Tehran, Iran
5
School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran
6
School of Mechanical Eng. University of Tehran
10.22038/abjs.2025.80846.3689
Abstract
Objectives: Total knee arthroplasty (TKA) success depends on accurate soft tissue releases and bone cuts for balanced weight distribution. Current challenges include the lack of predictors to guide the extent and timing of soft tissue release during surgery. This study investigates the relationship between radiographic parameters and the valgus cut angle (VCA) of the distal femur, and their correlation with the stage of medial soft tissue release (MSTR) in TKA patients. The aim is to identify predictive factors that assist in achieving proper biomechanics and soft tissue balance.
Methods: In this prospective cohort study, preoperative standard lower limb three-joint views of 62 limbs (57 patients) were examined to explore the relationship between radiographic parameters, the stage of MSTR, and VCA. Univariate and multivariate linear regression, along with statistical analysis tools, were used to identify relationships and cut-off values.
Results: There was a notable positive correlation between VCA and medial hip offset (MHO), as well as between VCA and femoral length (FL) (both with P < .001). Patients with shorter femurs and an MHO greater than 4.35 cm required a distal femoral cut angle of 6 degrees or more, while those with longer femurs and an MHO less than 4.35 cm needed an angle of less than 6 degrees (SEN: 83%, SPE: 80%). Additionally, the jointline congruency angle (JLCA), varus angle (VA), and lateral distal femoral angle (LDFA) showed significant correlations with the stage of MSTR. Among these, the VA was the most accurate predictor (SEN: 91.7%, SPE: 100%).
Conclusion: Raising the LDFA to over 93.5°, JLCA to over 7.5°, and VA to over 19° would heighten the probability of requiring extensive MSTR. Additionally, MHO and FL are the most critical predictive factors for determining the VCA.
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