Radiological and Clinical Evaluation of the Ipsilateral Ankle of Patients Who Underwent Total Knee Arthroplasty: A Prospective Study

Vollständiger Abstract

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Background/Objectives: Total knee arthroplasty (TKA) corrects coronal malalignment at the knee, but its effect on the structural status of the ipsilateral ankle is poorly characterised. This prospective study evaluated clinical, radiographic, and MRI-detected changes in the ipsilateral ankle after TKA, and tested whether such changes are related to the magnitude of mechanical axis correction. Methods: Seventy-one consecutive patients (80 operated limbs; mean age 63.9 ± 7.2 years; 83.1% female) undergoing primary TKA with a systematic neutral mechanical alignment strategy were assessed prospectively. Mechanical axis (MA) and talar tilt (TT) were measured on full-length weight-bearing radiographs, ankle-specific status was evaluated with the Foot and Ankle Outcome Score (FAOS), and ipsilateral ankle MRI was performed preoperatively, in the early postoperative period, and at follow-up (median 37 days, interquartile range (IQR) 34–44). Chondral/osteochondral findings and bone marrow oedema were recorded separately at the talus, distal tibia, and subtalar joint. Radiographic and MRI outcomes were analysed at the limb level using linear mixed-effects models and logistic generalised estimating equations with patient as the clustering variable; clinical outcomes were analysed at the patient level. Results: MA improved from 11.62 ± 5.57° to 4.29 ± 4.27° (mean change −7.34°, 95% confidence interval (CI) −8.49 to −6.18; p < 0.001), whereas TT was unchanged (−0.02 ± 1.87° to −0.22 ± 1.91°; p = 0.256). All FAOS subscales improved significantly (total 66.7 ± 27.6 to 84.4 ± 25.1; p < 0.001). Chondral/osteochondral findings were present in 41.2% of limbs preoperatively and were newly reported during follow-up in 40.4% of previously unaffected limbs. Newly reported bone marrow oedema was most frequent in the distal tibia (16/79 limbs, 20.3%), compared with the talus (8/79, 10.1%) and the subtalar joint (6/70, 8.6%). The magnitude of MA correction was not associated with change in TT (r = −0.040), change in FAOS (r = 0.023), or the development of new MRI findings (odds ratio (OR) 1.021 per degree; p = 0.682), and no dose–response gradient was observed across tertiles of correction. Conclusions: Following TKA with neutral mechanical alignment, substantial correction of the mechanical axis and significant clinical improvement occurred without a measurable change in talar tilt. MRI changes in the ipsilateral ankle were modest, concentrated in the distal tibia, and unrelated to the magnitude of alignment correction, suggesting that perioperative rather than alignment-related factors may predominate in the early postoperative period. Given the high preoperative burden of ankle degeneration and the short follow-up interval, the mechanisms and long-term significance of these findings remain uncertain.