Distinct effects of three knee-preserving surgeries on hip-knee-ankle alignment in patients with knee osteoarthritis

Abstract

Background: Unicompartmental knee arthroplasty (UKA), high tibial osteotomy (HTO), and distal femoral osteotomy (DFO) are common knee-preserving surgeries for knee osteoarthritis (KOA), yet systematic comparisons of their effects on lower limb biomechanical parameters remain limited.

Objective: To retrospectively evaluate and compare the impacts of UKA, HTO, and DFO on hip-knee-ankle alignment in KOA patients, providing evidence for personalized surgical strategy formulation. We hypothesized that these procedures would exert differential effects on specific alignment parameters.

Methods: A total of 256 patients with knee osteoarthritis were initially screened. After applying the inclusion and exclusion criteria, 150 patients were enrolled and assigned to the UKA, HTO, or DFO group (50 patients per group). Preoperative and postoperative changes in seven alignment parameters were measured: medial proximal tibial angle (MPTA), mechanical greater trochanter angle (MGTA), femorotibial anatomic angle (FTA), distal tibial femoral angle (DTTA), talar dome mechanical axis angle (TDMA), talar tilt angle (TTA), and the mechanical axis percentage (%MA). Intergroup differences in these parameters were analyzed statistically.

Results: (1) Baseline demographics and preoperative lower limb alignment parameters were comparable across groups. (2) UKA significantly changed MPTA, FTA, DTTA, TDMA, and %MA, but not MGTA or TTA. (3) DFO significantly changed MPTA, MGTA, FTA, and %MA, but not DTTA, TDMA, or TTA. (4) HTO significantly modified MPTA, MGTA, FTA, DTTA, TDMA and %MA, except for TTA. (5) UKA vs. HTO: No differences in FTA or DTTA, but significant differences in MPTA, MGTA, TDMA, TTA, and %MA. (6) UKA vs. DFO: No differences in MPTA or DTTA, but significant disparities in MGTA, FTA, TDMA, TTA and %MA.

Conclusion: UKA, HTO, and DFO each influence lower limb biomechanics in KOA patients, with distinct effects on specific alignment parameters. Surgical selection should prioritize individual anatomical and pathological characteristics to achieve personalized care.

Keywords: Biomechanics; Distal femoral osteotomy; High tibial osteotomy; Knee osteoarthritis; Knee-preserving surgery; Lower limb alignment; Unicompartmental knee arthroplasty.

Fig. 1

Angle measurements. A shows the medial proximal tibial angle (MPTA), formed by the tibial plateau and the mechanical axis of the tibia, measured medially. B illustrates the mechanical greater trochanter angle (MGTA), defined as the angle between the mechanical axis of the femur and a line drawn from the tip of the greater trochanter to the femoral head rotation center (x). This angle is formed between a constant line (greater trochanter to femoral head center) and a variable line (femoral mechanical axis). C depicts the femorotibial anatomic angle (FTA), which is the lateral angle between the anatomic axis of the femur and the anatomic axis of the tibia. D shows the distal tibial-talar angle (DTTA), the lateral angle between the line of the anatomical axis of the tibia and the line parallel to the talar dome. E represents the talar dome mechanical axis angle (TDMA), defined as the transverse angle between the mechanical axis of the lower limb and a line parallel to the talar dome. F illustrates the talar tilt angle (TTA), which is the lateral angle between a line parallel to the tibial plateau and a line parallel to the talar dome. G depicts the mechanical axis percentage (%MA), defined as the intersection point between the lower limb mechanical axis—drawn from the femoral head center to the ankle joint midpoint—and the tibial plateau on standing full-length bilateral lower limb radiographs. This parameter is quantified with the medial tibial plateau margin set at 0% and the lateral margin at 100%