Work

Tibia‐only planning to 3° valgus implies mechanical medial proximal tibial angle ≥94° in about two‐thirds of varus knee osteoarthritis radiographs

Year: 2026

Type: article

Abstract: Purpose: To estimate the proportion of radiographic records from patients with varus knee osteoarthritis in which tibia-only planning targeting a hip-knee-ankle angle (HKA) of 183° (3° valgus) yielded a calculated mechanical medial proximal tibial angle (mMPTA) of at least 94°. Methods: In a retrospective database, 1426 knee-specific records were screened. Eligible records came from adults with standardised standing full-length lower-limb radiographs. Exclusions covered hip and foot deformities, spontaneous femoral condyle osteonecrosis, previous lower-limb surgery, malignancy, major trauma, poor image quality and excessive rotation. Symptomatic knee osteoarthritis, numerical quality control and HKA below 176.5° defined the analytical cohort. Alignment was measured using an artificial intelligence-assisted system. Correction was assigned entirely to the tibia. The mechanical lateral distal femoral angle and joint line convergence angle were held constant. The primary target was 3° valgus; 1°, 2°, 4°, 5° and 6° of valgus were supplementary targets. Analyses were descriptive, with two-sided 95% Wilson confidence intervals for proportions. Results: The analysis included 627 records from 392 patients (mean age, 67.3 ± 9.2 years; 28.6% men). At the 3° valgus target, the mean calculated mMPTA was 96.0 ± 3.7°; 424/627 records reached at least 94° (67.6%; 95% confidence interval, 63.9%-71.2%). The most frequent deformity-source patterns were intraarticular alone (24.7%) and tibial-side plus intraarticular (24.4%). Conclusions: At a 3° valgus target, tibia-only planning implied an mMPTA of at least 94° in about two-thirds (67.6%) of records from this varus knee osteoarthritis cohort. Preoperative planning should therefore assess local tibial joint-line orientation and deformity source alongside the whole-limb alignment target. Level of Evidence: Level IV, retrospective radiographic geometry study.

Source: Journal of Experimental Orthopaedics

DOI: 10.1002/jeo2.70977