Compensatory changes in lower limb alignment following total knee arthroplasty: large valgus knee correction (≥ 10°) demonstrates substantial alterations in ankle and subtalar joint alignment.

INTRODUCTION

Total knee arthroplasty can substantially affect global lower limb alignment. However, its specific impacts on ankle and subtalar joint alignment remain poorly understood. This study investigates changes in ankle and subtalar alignment following varying degrees of varus/valgus knee correction in order to further our understanding of this association.

MATERIALS AND METHODS

This retrospective study included 100 patients who underwent surgery for primary osteoarthritis. Patients diagnosed with conditions other than primary knee OA and those with incomplete or poor-quality imaging were excluded. Patients were categorized into four groups by the degree of intraoperative coronal knee alignment correction: Group 1 (< 10° varus, n = 37), Group 2 (≥ 10° varus, n = 30), Group 3 (< 10° valgus, n = 18), and Group 4 (≥ 10° valgus, n = 15). Hip-knee-ankle angle, tibial plafond inclination, talar inclination, tibiotalar tilt, and subtalar varus-valgus angle, were measured preoperatively and postoperatively on full-length, standing, anteroposterior X-ray images.

RESULTS

TKA resulted in postoperative changes in all measured angles regardless of the degree of varus/valgus correction. Notably, ≥ 10° valgus correction led to statistically significant postoperative alterations in ankle and subtalar alignment: tibial plafond inclination from 84.9 to 89.5° (Δ 4.6, range,1.5-7.8, P <.01), tibiotalar tilt from 83.1 to 89.3° (Δ 6.2, range,1.1-9.6, P =.02), and subtalar varus-valgus angle from 66.4 to 72.6° (Δ 6.2, range,1.9-12.1, P <.01).

CONCLUSION

While knee deformity correction during TKA generally realigns the ankle and subtalar joint, our study has shown that large valgus knee correction (≥ 10°) during TKA significantly alters ankle and subtalar joint alignment. Thus, potentially leading to unfavorable postoperative outcomes in patients with abnormal or stiff joints. We recommend that future studies investigate the long-term effects of large valgus knee corrections during TKA on ankle and subtalar joint alignment and their impact on postoperative outcomes.