The biomechanical function of the patellar tendon during in-vivo weight-bearing flexion

Abstract

Few studies have investigated the function of the patellar tendon in-vivo. This study quantified the three-dimensional (3D) kinematics of the patellar tendon during weight-bearing flexion.Eleven subjects were imaged using magnetic resonance (MR). Sagittal plane images were outlined to create a 3D model of the patella, tibia, and femur and included the attachment sites of the patellar tendon. Each attachment site was divided into central, medial, and lateral thirds. Next, the subjects were imaged using fluoroscopy from two orthogonal directions while performing a single-leg lunge. The models and fluoroscopic images were used to reproduce the motion of the patella, tibia, and femur. The apparent elongation, sagittal plane angle, and coronal plane angle of each third of the patellar tendon was measured from the relative motion of the attachment sites.All three portions of the patellar tendon deformed similarly with flexion. The length of the patellar tendon significantly from full extension to 30°. From 30°-110°, no significant change in the length of the patellar tendon was observed. The patellar tendon was oriented anteriorly at flexion angles less than 60° and posteriorly thereafter. From full extension to 60°, the medial orientation of the patellar tendon decreased significantly with flexion. These data may have important implications for anterior cruciate ligament reconstruction using patellar tendon autografts and for the design of rehabilitation regimens for patients of patellar tendon repair.

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

“…The data on the sagittal plane angle are consistent with the previous in vitro cadaveric studies within 1208 of flexion 27-29 and in vivo weight-bearing results 18,24 with knees flexed below 1108. The changes in the sagittal plane angle observed in our study might be related to tibiofemoral kinematics.…”

“…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 to investigate the patellar tendon kinematics of healthy subjects during weight-bearing deep knee bend up to 1508. Specifically, the 3D characteristics of the patellar tendon orientation/elongation and the tendon's interaction with the anterior tibial surface were investigated.…”

“…20 The patellar tendon insertion sites at the tibial tubercle and the distal patella were also segmented. 18 After MRI, each subject performed single leg knee bend up to maximum flexion in the field of view of two orthogonally positioned fluoroscopes (BV Pulsera; Philips, Bothell, WA). The subjects were instructed to hold the position for a second at each selected angle and allowed to use the contralateral leg and a handrail to maintain balance.…”

“…Ultrasound studies reported that patellar tendon strain during in vivo isometric knee extension at 908 of flexion was within 7%. 13,26 DeFrate et al 18 reported patellar tendon elongation during in vivo weight-bearing knee flexion from 08 to 1108, where the patellar tendon increased its length from 50 to 56 mm in the central portion. Gejo et al 17 used foil strain gages to measure tendon strain during intra-operative passive flexion from 458 to 1358, and found that the maximum strain was within 300 microstrain at 1358.…”

The Role of Mechanical Loading in Tendon Development, Maintenance, Injury, and Repair

“…Given the highly organized, hierarchical collagen structure ( Fig. 1), tendons exhibit high tensile strength [4][5][6] , allowing for the efficient transmission of large loads, a result of the local cell population to adapt to changes in loading conditions 7 . Further contributing to the structure and biomechanical properties are proteoglycans and glycoproteins, which function to regulate the process of collagen fibrillogenesis and control fibril diameter throughout tendon development and homeostasis [8][9][10][11][12][13] .…”