Yohei Haruta1, Shinya Kawahara2, Kanenobu Tsuchimochi1, Akihiko Hamasaki1, Toshihiko Hara1. 1. Department of Orthopedic Surgery, Aso-Iizuka Hospital, 3-83 Yoshio-machi, Iizuka-city, Fukuoka 820-8505, Japan. 2. Department of Orthopedic Surgery, Aso-Iizuka Hospital, 3-83 Yoshio-machi, Iizuka-city, Fukuoka 820-8505, Japan. Electronic address: kawahara@ortho.med.kyushu-u.ac.jp.
Abstract
BACKGROUND: An intramedullary (IM) rod is used to resect the distal femur vertically to the femoral mechanical axis in the coronal plane in many cases of total knee arthroplasties (TKA). The valgus angle between the mechanical axis and the anatomical axis of the distal femur is estimated preoperatively. It is known the deviation of the IM rod in the femoral canal could influence the femoral component alignment. However, there is no published data regarding how many degrees of deviation to make with the IM rod. The purpose of this study is to measure each deviation of the IM rod using three-dimensional (3D) computer simulations. METHODS: Preoperative CT scans on 30 knees undergoing TKA were studied. The line connecting central points at 10 and 20 cm proximal from the intercondylar notch was defined as the anatomical axis and the point at which the anatomical axis intersects the surface of the distal femur was considered as the entry point of the IM rod. The medio-lateral (ML) and antero-posterior (AP) deviations between the anatomical axis and the IM rod were measured. RESULTS: The ML and AP deviations were 0.8 and 1.1° on average. The IM rod was deviated medio-laterally more than 1.0° in three knees (10%). CONCLUSION: Surgeons should note the ML difference of the resection thickness of the distal femur for coronal alignment. If the ML difference varies greatly from the preoperative planning, they need to adjust at most 1.0° of valgus angle to achieve the appropriate coronal alignment. Level of evidence III, Therapeutic.
BACKGROUND: An intramedullary (IM) rod is used to resect the distal femur vertically to the femoral mechanical axis in the coronal plane in many cases of total knee arthroplasties (TKA). The valgus angle between the mechanical axis and the anatomical axis of the distal femur is estimated preoperatively. It is known the deviation of the IM rod in the femoral canal could influence the femoral component alignment. However, there is no published data regarding how many degrees of deviation to make with the IM rod. The purpose of this study is to measure each deviation of the IM rod using three-dimensional (3D) computer simulations. METHODS: Preoperative CT scans on 30 knees undergoing TKA were studied. The line connecting central points at 10 and 20 cm proximal from the intercondylar notch was defined as the anatomical axis and the point at which the anatomical axis intersects the surface of the distal femur was considered as the entry point of the IM rod. The medio-lateral (ML) and antero-posterior (AP) deviations between the anatomical axis and the IM rod were measured. RESULTS: The ML and AP deviations were 0.8 and 1.1° on average. The IM rod was deviated medio-laterally more than 1.0° in three knees (10%). CONCLUSION: Surgeons should note the ML difference of the resection thickness of the distal femur for coronal alignment. If the ML difference varies greatly from the preoperative planning, they need to adjust at most 1.0° of valgus angle to achieve the appropriate coronal alignment. Level of evidence III, Therapeutic.
Authors: Kai Lei; Li Ming Liu; Yi Xiang; Xin Chen; Hua Quan Fan; Yang Peng; Jiang Ming Luo; Lin Guo Journal: J Orthop Surg Res Date: 2020-12-09 Impact factor: 2.359
Authors: Jai Thilak; Balu C Babu; Mohan Thadi; Vipin Mohan; T Arun Kumar; Prajwal P Mane; Greeshma C Ravindran Journal: Indian J Orthop Date: 2021-01-04 Impact factor: 1.251