Summary

Partial-thickness lateral and medial patellar tenotomy after middle one-third bone patellar tendon autograft and repair could obtain the better biomechanics of extensor mechanism compares to no repair.

Abstract

Background

One of post-operative quadriceps weakness usually been found after bone-patellar tendon-bone (BPTB) autograft harvesting. Partial thickness tenotomy with gap closure was designed to create the defect healing.
Objectives: The purpose of this study was to compare the biomechanics between the donor’s tendon defect repair and conventional non-repair techniques.

Methods

Twelve cadaveric knees were randomized the side and middle third BPTB was harvested. Repair group (longitudinal partial thickness tenotomy and side-to-side repair with Ethibond) and non-repair group were measured the patellofemoral (PF) pressure and area in different knee motion. All specimens were cut and mounted to Instron 4467 machine for biomechanics tests. The tendon length, width and thickness of remained patellar tendon were collected. The biomechanics parameters were PF pressure, PF area, maximal load to failure (max load), maximal stress (max stress), stiffness, Young’s modulus and location of failure.

Results

Four male and two female specimens were recruited with mean age of 67.83 years. There was no significant difference in PF pressure and contact area between two groups. When each facet was separately analysed in different knee flexion angle, only the medial facet-PF pressure was no significantly different (Repair group=48-108 KPa, p=0.084 and non-repair group=42-108 KPa, p=0.003). Max load showed no statistically significant difference. Young’s modulus (24.02-202.47 MPa, p=0.028) and max stress (5.21-35.54 MPa, p=0.046) of the repair group were significantly increased. PF contact area, stiffness, tendon length and width were not statistically significant different. No mid-substance tear was found in both groups.

Conclusions

BPTB defect repairing did not increase PF pressure. Max load was no significantly difference between two groups. Increasing of Young’s modulus and max stress in repair group may advantage for maintain the extensor mechanism. The repair group showed better biomechanics that may advantage for maintain the extensor mechanism. Functional and clinical outcomes after reconstruction need more studied.