In‐vivo patellar tendon kinematics during weight‐bearing deep knee flexion

Abstract

This study quantified in-vivo 3D patellar tendon kinematics during weight-bearing deep knee bend beyond 1508. Each knee was MRI scanned to create 3D bony models of the patella, tibia, femur, and the attachment sites of the patellar tendon on the distal patella and the tibial tubercle. Each attachment site was divided into lateral, central, and medial thirds. The subjects were then imaged using a dual fluoroscopic image system while performing a deep knee bend. The knee positions were determined using the bony models and the fluoroscopic images. The patellar tendon kinematics was analyzed using the relative positions of its patellar and tibial attachment sites. The relative elongations of all three portions of the patellar tendon increased similarly up to 608. Beyond 608, the relative elongation of the medial portion of the patellar tendon decreased as the knee flexed from 608 to 1508 while those of the lateral and central portions showed continuous increases from 1208 to 1508. At 1508, the relative elongation of the medial portion was significantly lower than that of the central portion. In four of seven knees, the patellar tendon impinged on the tibial bony surface at 1208 and 1508 of knee flexion. These data may provide useful insight into the intrinsic patellar tendon biomechanics during a weight-bearing deep knee bend and could provide biomechanical guidelines for future development of total knee arthroplasties that are intended to restore normal knee function. ß 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30: [1596][1597][1598][1599][1600][1601][1602][1603] 2012 Keywords: patellar tendon elongation; patellar tendon orientation; deep knee flexion; weight-bearing activity; knee kinematics Maximum flexion of the knee reaches beyond 1508. 12 Restoration of knee function in the entire flexion range after total knee arthroplasty (TKA) has been challenging. 3 While most follow-up studies reported that knee flexion after TKA of between 110 to 1208, 4 many studies investigated knee biomechanics in deep flexion to understand the biomechanical factors that may affect flexion capabilities. 1,2,5-9 Among these factors, the function of the patellar tendon, an essential component of the extensor mechanism, plays a critical role.Numerous in vitro studies reported the material properties, 10,11 orientation, and/or moment arms of the patellar tendon. 12 In vivo studies measured patellar tendon elongation using ultrasound 13 and MRI. 14 MRI was also used to determine the orientation and moment arms of the patellar tendon. 15,16 Foil strain gages were used to measure the mid-point patellar tendon strain intra-operatively. 17 Recently, DeFrate et al. 18 investigated patellar tendon kinematics using a combined MRI and dual fluoroscopic image technique. However, most of these studies examined patellar tendon biomechanics within the range of knee flexion up to 1108. 18,19 Quantitative data on the patellar tendon function in deep knee flexion are still unclear.Our objective was ...

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In Vivo Kinematics of the Extensor Mechanism of the Knee During Deep Flexion

“…Our previous study showed that in general, the patella shifted laterally and tilted laterally along the flexion path of the knee [10]. After 60 deg of flexion, the patellar shift and tilt were almost constant while the patellar tilted medially at 150 deg.…”

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Automatic determination of an anatomical coordinate system for a three-dimensional model of the human patella

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