Il Seok Park1, Alvin Ong2, Chang Hyun Nam1, Nong Kyum Ahn1, Hye Sun Ahn1, Su Chan Lee1, Kwang Am Jung3. 1. Joint & Arthritis Research, Department of Orthopaedic Surgery, Himchan Hospital, Seoul, Korea. 2. Rothman Institute, NJ, USA. 3. Joint & Arthritis Research, Department of Orthopaedic Surgery, Himchan Hospital, Seoul, Korea. Electronic address: kwangamj@gmail.com.
Abstract
BACKGROUND: Adequate rotation of the femoral component in total knee arthroplasty is mandatory for prevention of numerous adverse sequelae. Therefore, we investigate whether there is the distal femoral deformity in knees with tibia vara. The purpose of this study was to evaluate the reliability of the transepicondylar axis as a rotational landmark in knees with tibia vara. METHODS: We retrospectively reviewed and selected 101 osteoarthritic knees with proximal tibia vara and 150 osteoarthritic knees without tibia vara for inclusion in this study. The transepicondylar axis (TEA), anteroposterior (AP) axis and posterior condylar (PC) line were measured using the axial image from magnetic resonance imaging axial images. We compared the external rotation angle of the TEA relative to the PC line between groups in order to investigate the presence of distal femoral anatomical adaptation in the tibia vara group. RESULTS: The TEA in the tibia vara group had 6.1º of external rotation relative to the PC line, which was not significantly different from the 6.0º of external rotation in the non-tibia vara group. The line perpendicular to the AP axis in the tibia vara group had 6.1º of external rotation relative to the PC line, which was not significantly different from the 5.4º of external rotation in the non-tibia vara group. Distal femoral geometry was unaffected by the tibia vara deformity. CONCLUSIONS: The use of transepicondylar axes in determining femoral rotation may produce flexion asymmetry in knees with tibia vara. LEVEL OF EVIDENCE: Level III.
BACKGROUND: Adequate rotation of the femoral component in total knee arthroplasty is mandatory for prevention of numerous adverse sequelae. Therefore, we investigate whether there is the distal femoral deformity in knees with tibia vara. The purpose of this study was to evaluate the reliability of the transepicondylar axis as a rotational landmark in knees with tibia vara. METHODS: We retrospectively reviewed and selected 101 osteoarthritic knees with proximal tibia vara and 150 osteoarthritic knees without tibia vara for inclusion in this study. The transepicondylar axis (TEA), anteroposterior (AP) axis and posterior condylar (PC) line were measured using the axial image from magnetic resonance imaging axial images. We compared the external rotation angle of the TEA relative to the PC line between groups in order to investigate the presence of distal femoral anatomical adaptation in the tibia vara group. RESULTS: The TEA in the tibia vara group had 6.1º of external rotation relative to the PC line, which was not significantly different from the 6.0º of external rotation in the non-tibia vara group. The line perpendicular to the AP axis in the tibia vara group had 6.1º of external rotation relative to the PC line, which was not significantly different from the 5.4º of external rotation in the non-tibia vara group. Distal femoral geometry was unaffected by the tibia vara deformity. CONCLUSIONS: The use of transepicondylar axes in determining femoral rotation may produce flexion asymmetry in knees with tibia vara. LEVEL OF EVIDENCE: Level III.