Postoperative femoral anteroposterior position while standing correlates with the posterior tibial slope and posterior femoral condylar offset in medial pivot total knee arthroplasty

Article type: Research Article

Authors: Takahashi, Yuki^a | Sato, Takashi^a; | Mochizuki, Tomoharu^b | Watanabe, Satoshi^a | Tanifuji, Osamu^b | Katsumi, Ryota^b | Endo, Naoto^b

Affiliations: [a] Department of Orthopaedic Surgery, Niigata Medical Center, Niigata, Niigata, Japan | [b] Division of Orthopedic Surgery, Department of Regenerative and Transplant Medicine, Niigata University Graduate School of Medical and Dental Science, Niigata, Niigata, Japan

Correspondence: [*] Corresponding author: Takashi Sato, Department of Orthopedic Surgery, Niigata Medical Center, 3-27-11 Kobari Nishi-ku, Niigata City, Niigata 950-2022, Japan. Tel.: +81 25 232 0111; Fax: +81 25 232 3431; E-mail: [email protected]

Abstract: BACKGROUND:After total knee arthroplasty (TKA), the femur tends to be located posteriorly under weight-bearing (WB) conditions, and a paradoxical femoral anterior motion occurs, leading to joint instability. OBJECTIVE:We aimed to clarify factors which affect the postoperative femoral anteroposterior position relative to the tibia under WB conditions (A-P position) in medial pivot (MP) TKA. METHODS:Among 126 knees (81 women) with primary TKA using MP prosthesis for varus osteoarthritic knees, 70 knees had cruciate-retaining inserts (CR) with the reduced conformity and 56 knees had cruciate-substituting inserts (CS) with the full conformity. Using the three-dimensional (3D) assessment system, the associations between the A-P position and the factors including pre- and postoperative lower extremity alignment, component positions, and posterior femoral condylar offset (PCO), were assessed regarding the type of inserts. RESULTS:Significant correlations were seen between the A-P position and posterior tibial slope (PTS), medial PCO, and lateral PCO. Regarding the difference between the two inserts, the PTS, medial PCO, and lateral PCO significantly correlated with the A-P position in the CR, but only the PTS correlated in the CS. CONCLUSIONS:The increased PTS and decreased PCO were the dominant factors for the A-P position in MP TKA.

Keywords: Femoral anteroposterior position, three-dimensional lower extremity alignment assessment system, posterior tibial slope, posterior condylar offset, total knee arthroplasty

DOI: 10.3233/BME-211299

Journal: Bio-Medical Materials and Engineering, vol. 33, no. 1, pp. 51-64, 2022