Optimized design of a barbed suture for flexor tendon repair under fatigue loading : experimentally informed extended finite element analysis -

Abstract

Flexor tendons are essential for hand function. Surgeries for these tendons are very serious and challenging; the repair site must endure active and passive immobilization forces in an arrangement that would guarantee the integrity of the tendon to redevelop. Early active mobilization is considered in some rehabilitation programs. This type of motion prevents tissue adhesion and results in a faster healing process. Hence, tendons must sustain forces under cyclic loading conditions. The conventional surgical technique requires tying some knots at the end of the tendon repaired site; these knots have many drawbacks that affect the tendon performance. Recently, barbed sutures are introduced to ensure the same security and strength as conventional sutures while decreasing tissue distortion and uniformly holding the forces. Previous work considered suturing with multiple strands; some work studied the validity of using a single suture but was restricted to the analysis of stresses under static loading conditions in order to attain the best suture configuration. The objective of this study is to comprehend the effect of the geometric change of the suture on its strength and to design a single suture that will tolerate the tendon force under cyclic loading. Four different elliptical aspect ratios (ratio of major to minor axis = ρ = 1-2, 1, 2, 3) suitable with the tendon’s geometry, were considered to study the strength of the suture and that of the barb. Using the extended finite element analysis in Abaqus, two loading conditions were applied on each aspect ratio, ρ, to acquire the one with the highest strength. Paris Law that uses the principles of linear elastic fracture mechanics was implemented to model the sutures under fatigue loading. Barbed suture with ρ = 2 was optimized for two cut angles (154°, 160°) and three cut depths (0.07mm, 0.12mm, 0.18mm) under a third loading condition that represents the suture-tendon interaction. Results show that the best design for a barbed