RESUMO
PURPOSE: Tibial bowing in valgus knees with arthritis can lead to component malplacement during total knee arthroplasty (TKA). Incidence of valgus knees with medial tibial bowing, its effect on tibial component placement during primary TKA and methods to improve accuracy of the component placement were studied. METHODS: Full-length weight-bearing alignment radiograph was taken in 117 patients (149 knees) with valgus deformity undergoing TKA. In these cases, the proximal tibial reference for extramedullary jig placement was planned preoperatively with reference to the tibial spines and classified as four zones. RESULTS: The mean preoperative hip-knee-ankle (HKA) angle was 192.9° (180.3-234.5°). Bowing >3° was considered significant (p < 0.001) and at this level of bowing, the proximal tibial reference was shifted from centre to medial. Tibial bowing <3° was considered straight and >3° as tibia valga. Tibia was bowed in 70 knees (46.97%). Severity of valgus deformity had strong positive correlation with the tibia valga (p < 0.001). The post-operative medial proximal tibial angle (MPTA) and HKA angle were 91.63° (87.9-95.7°) and 182.6° (178.1-189.7°), respectively. The mean MPTA and post-operative HKA angle in bowed and straight tibiae were 90.35° versus 89.78° (p = 0.547) and 181.5° versus 180.7° (p = 0.5716), respectively, and the difference was not statistically significant. CONCLUSION: Medial tibial bowing is very common in valgus knees. Tibia valga has a strong positive correlation with the severity of valgus deformity. Accurate tibial component placement can be achieved with a medialized reference point for extramedullary tibial cutting jig in knees with significant tibia valga. The study has been registered in clinical trials registry - India (CTRI/2018/03/012283).
