In-Vivo Knee Kinematics In Individuals With Arthrofibrosis After Anterior Cruciate Ligament Reconstruction

Objective: The objective of this study was 1)to quantify the 6 degree-of-freedom(6DOF)knee kinematics during physiological conditions in the knee with arthrofibrosis after ACL reconstruction;and 2)to compare it with those of the contralateral health knee using a dual fluoroscopic imaging system(DFIS).Methods : The patients with arthrofibrosis after ACLR visiting the Department of Rehabilitation Medicine,Ninth People’s Hospital,Shanghai Jiao Tong University School of Medicine between August 1st 2019 and February 1st 2020 were screened according to the inclusion and exclusion criteria.Fifteen patients with arthrofibrosis in one knee after ACL reconstruction participated in this study.Before kinematic testing,the demographic data,the IKDC and Lysholm knee scores were collected,and knee extensor strength of both knees were measured.Computed tomography and dual fluoroscopic imaging were used to evaluate in-vivo kinematics of affected and contralateral knees under weightbearing and non-weightbearing conditions.Each patient was asked to flex the tested knee from the extended knee position to maximum flexion.Both knees of each patient were imaged using a computed tomography(CT)scanner in knee extension position.These CT images were used to create 3D anatomical models of the femur,tibia,fibula,and patella.Next,the fluoroscopic images and the 3D CT knee model were imported into a custom Matlab program(R2018a;Math Works,Inc.,Natick,MA USA).The projections of the knee model were manipulated to match the outlines of fluoroscopy images taken during the actual tests.When the 3D models best matched the fluoroscopic images,the positions of the models reproduced the relative positions of the knee at each flexion angle.Results: Patellofemoral and tibiofemoral kinematics in 6 DOF under the weightbearing condition: There were significant differences between the knees for femoral rotation and patellar superior-inferior shift at 15°,30°,45°,60° and 75° of knee flexion(p≤0.046).There were also significant differences between the knees for patellar tilt and flexion at 60° and75°of knee flexion(p≤0.03).Patellofemoral and tibiofemoral kinematics in 6 DOF under the non-weightbearing condition: There were significant differences between the knees for patellar superior-inferior shift and anterior-posterior shift at 15° of knee flexion(p≤0.03).There were significant differences between the knees for patellar flexion at 15°,30°,45°,60° and 75° of knee flexion(p≤0.02).There were also significant differences between the knees for femoral medial-lateral translation at 75° of knee flexion(p=0.045).Differences in patellofemoral kinematics between weightbearing and non-weightbearing conditions: The patellar tilt angle(p=0,007)and medial patellar shift(p=0.043)under the weightbearing condition was significantly decreased compared to the non-weightbearing task between 15° and 30° of knee flexion.The lateral patellar shift during a non-weightbearing task was significantly decreased between 60° and 75° of knee flexion(p=0.005),and the inferior patellar shift under the weightbearing condition was significantly increased between45° and 75° of knee flexion(p=0.040).Knee extensor strength and its relationship to patellofemoral kinematics in the affected knee: There was a statistically significant decrease in the knee extensor strength in the affected knee compared with the contralateral knee(p=0.008).There was a statistically significant decrease in the range of patellar superior-inferior shift(P=0.020),flexion(P=0.026),and tilt(P=0.001)in the affected knee compared with the contralateral knee from15° to 75° of knee flexion.There was a strong positive linear correlation between knee extensor strength and patellar superior-inferior shift(r = 0.747;P =.008).A knee extensor strength LSI <90% was 89% sensitive and 9% specific for limited patellar superior-inferior shift.Conclusions: 1.This study identified alternations of tibiofemoral and patellofemoral kinematics in patients with arthrofibrosis after anterior cruciate ligament reconstruction compared with the contralateral knee.2.These results indicate that patellofemoral kinematics during non-weightbearing positions do not sufficiently represent the patellar tracking during functional weightbearing activities.3.Decreased patellar mobility is common in patients with arthrofibrosis after ACL reconstruction.There is a strong linear correction between the knee extensor strength and patellar superior-inferior shift in the affected knee.