W P Yau1, K Y Chiu, W M Tang, T P Ng. 1. Division of Joint Replacement Surgery, Department of Orthopedics and Traumatology, The University of Hong Kong, Pokfulam, Hong Kong. peterwpy@hkucc.hku.hk
Abstract
PURPOSES: To study the incidence of femoral or tibial bowing in the coronal plane in a Chinese population, and how it affects the accuracy of bone cuts for total knee replacement when an intramedullary alignment system is used. METHODS: Standing radiographs of the entire lower limb of each patient with end-stage primary osteoarthritis of the knee were analysed. All radiographs were digitised and the extent of bowing in the coronal plane measured. A bowing was marked if an angulation was more than 2 degrees. The projected error of cutting was then calculated. RESULTS: Of 93 lower limbs, 58 (62%) of the femurs had marked bowing in the coronal plane; 41 (44%) had a mean lateral bowing of 5.3 (standard deviation [SD], 3.2) degrees; 17 (18%) had a mean medial bowing of 4.4 (SD, 1.9) degrees. Marked tibial bowing in the coronal plane was less common (30 tibias, 32%). If a cutting error of more than 2 degrees was considered unacceptable, significantly more unacceptable cuts would ensue in the groups with marked bowing (p=0.003 for femurs and p<0.001 for tibia, respectively). CONCLUSION: The incidence of femoral or tibial bowing in the coronal plane was high in a Chinese population with end-stage osteoarthritis of the knee. This phenomenon may increase bone cut errors in total knee replacement if an intramedullary alignment system is used and the extent of bowing is not recognised.
PURPOSES: To study the incidence of femoral or tibial bowing in the coronal plane in a Chinese population, and how it affects the accuracy of bone cuts for total knee replacement when an intramedullary alignment system is used. METHODS: Standing radiographs of the entire lower limb of each patient with end-stage primary osteoarthritis of the knee were analysed. All radiographs were digitised and the extent of bowing in the coronal plane measured. A bowing was marked if an angulation was more than 2 degrees. The projected error of cutting was then calculated. RESULTS: Of 93 lower limbs, 58 (62%) of the femurs had marked bowing in the coronal plane; 41 (44%) had a mean lateral bowing of 5.3 (standard deviation [SD], 3.2) degrees; 17 (18%) had a mean medial bowing of 4.4 (SD, 1.9) degrees. Marked tibial bowing in the coronal plane was less common (30 tibias, 32%). If a cutting error of more than 2 degrees was considered unacceptable, significantly more unacceptable cuts would ensue in the groups with marked bowing (p=0.003 for femurs and p<0.001 for tibia, respectively). CONCLUSION: The incidence of femoral or tibial bowing in the coronal plane was high in a Chinese population with end-stage osteoarthritis of the knee. This phenomenon may increase bone cut errors in total knee replacement if an intramedullary alignment system is used and the extent of bowing is not recognised.