In vivo kinematics of cruciate-retaining total knee arthroplasty after a change of polyethylene insert configuration

• Main Authors: Shotaro Watanabe, Tetsuya Tomita, Ryuichiro Akagi, Atsuya Watanabe, Takaharu Yamazaki, Takahiro Enomoto, Ryosuke Nakagawa, Seiji Kimura, Seiji Ohtori, Takahisa Sasho
• Format: Article
• Language: English
• Published: Elsevier 2021-04-01
• Series: Asia-Pacific Journal of Sports Medicine, Arthroscopy, Rehabilitation and Technology
• Subjects: Configuration; Finite element analysis; Fluoroscopy; Kinematics; Total knee arthroplasty; Two-dimensional/three-dimensional registration
• Online Access: http://www.sciencedirect.com/science/article/pii/S2214687320300972

Background: To investigate in vivo kinematics of total knee arthroplasty (TKA) with the introduction of a mildly constrained (MC) type of polyethylene (PE). We compared the knee kinematics with a reported pattern after surgery using the same component with a conventionally constrained (CC) type of PE. Methods: Finite element analysis (FEA) was performed to examine different peak stress distribution of both types of PE. For in vivo study, patients who underwent cruciate-retaining TKA using a total knee system with MC-PE were included. Fluoroscopic surveillance was used to measure the weight-bearing deep knee bend (squatting) using a two-dimensional/three-dimensional (2-D/3-D) registration technique. Results: FEA analysis revealed the edge loading of the femoral component on PE in CC but not in MC. During the study period, 42 patients underwent TKA with MC-PE. Among them, 13 agreed to participate in the present study. In vivo kinematics analysis found that starting from an average external rotation of femur being 7.1° at 0° of flexion, the rotation slightly decreased to 6.8° at 10° of flexion, then increased with increasing knee flexion until it reached 10.8° at 80° of flexion, and finally decreased to 9.8° at 100° of knee flexion. The results indicate a modest medial pivot pattern. Although the overall pattern was similar for both MC-PE and CC-PE, a slight difference was observed. MC-PE showed a slight internal rotation of 0.3° from 0 to 10° of knee flexion, whereas CC-PE showed a gradual increase of external rotation in this range. Conclusions: Change of configuration from CC to MC did not substantially affect in vivo kinematics of knees after TKA. Considering the theoretical wider range of allowance of rotation, MC-PE is easier for knee surgeons to use.