Zhenming Zhang1,2, Chaochao Zhou1,3, Zhitao Rao1, Timothy Foster1,4, Hany Bedair1,4,3, Guoan Li5,6. 1. Orthopaedic Bioengineering Research Center, Newton-Wellesley Hospital, 159 Wells Ave, Newton, MA, 02459, USA. 2. Department of Orthopaedics, China-Japan Union Hospital of Jilin University, Changchun, Jilin, China. 3. Department of Orthopaedic Surgery, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA. 4. Department of Orthopedic Surgery, Newton-Wellesley Hospital, Newton, MA, USA. 5. Orthopaedic Bioengineering Research Center, Newton-Wellesley Hospital, 159 Wells Ave, Newton, MA, 02459, USA. gli1@partners.org. 6. Department of Orthopedic Surgery, Newton-Wellesley Hospital, Newton, MA, USA. gli1@partners.org.
Abstract
BACKGROUND: Gap balance of the knee at 0° and 90° of flexion has been pursued in total knee arthroplasty (TKA) with the trans-epicondyle axis (TEA) as a reference. This study investigated the height changes of the tibiofemoral articulation and compared the data with the femoral condyle height changes measured using different flexion axes. MATERIALS AND METHODS: Twenty healthy knees were investigated during an in vivo weightbearing flexion using a technique combining MRI and a dual fluoroscopic imaging system (DFIS). The tibiofemoral contact points and the femoral condyle heights [measured using: TEA, geometric center axis (GCA), and iso-height axis (IHA)] were determined at each flexion angle. The height changes of the articular contact points and the femoral condyles were compared along the flexion path. RESULTS: The changes of the medial and lateral contact point heights were within 2.5 mm along the flexion path. The changes of the medial and lateral condyle heights were within 8.9 mm for TEA, within 4.2 mm for GCA and within 3.0 mm for IHA. The height changes measured by the contact points and IHA are similar (p > 0.05), and both are significantly smaller than those measured using the TEA and GCA (p < 0.05). CONCLUSIONS: The TEA and GCA measured varying femoral condyle heights, but the IHA resulted in minimal condyle height changes and could better represent the articulation characteristics of the knee. The data suggested that the IHA could be used as an alternative reference to guide surgical preparation of gap balance along the knee flexion path during TKA surgeries.
BACKGROUND: Gap balance of the knee at 0° and 90° of flexion has been pursued in total knee arthroplasty (TKA) with the trans-epicondyle axis (TEA) as a reference. This study investigated the height changes of the tibiofemoral articulation and compared the data with the femoral condyle height changes measured using different flexion axes. MATERIALS AND METHODS: Twenty healthy knees were investigated during an in vivo weightbearing flexion using a technique combining MRI and a dual fluoroscopic imaging system (DFIS). The tibiofemoral contact points and the femoral condyle heights [measured using: TEA, geometric center axis (GCA), and iso-height axis (IHA)] were determined at each flexion angle. The height changes of the articular contact points and the femoral condyles were compared along the flexion path. RESULTS: The changes of the medial and lateral contact point heights were within 2.5 mm along the flexion path. The changes of the medial and lateral condyle heights were within 8.9 mm for TEA, within 4.2 mm for GCA and within 3.0 mm for IHA. The height changes measured by the contact points and IHA are similar (p > 0.05), and both are significantly smaller than those measured using the TEA and GCA (p < 0.05). CONCLUSIONS: The TEA and GCA measured varying femoral condyle heights, but the IHA resulted in minimal condyle height changes and could better represent the articulation characteristics of the knee. The data suggested that the IHA could be used as an alternative reference to guide surgical preparation of gap balance along the knee flexion path during TKA surgeries.