Search

The variety of techniques used to measure the cross-sectional area of soft connective tissues during mechanical testing lead to inconsistencies in elastic descriptions. This study compares the numerical differences between finite elasticity (Eularian and Lagrangian formulations) and infinitesimal elasticity when considering stress, strain and elastic modulus of ligamentous tissue. Our results found stress differences (Cauchy versus Kirchhoff) of 22.4%, strain differences (engineering versus Green versus Almansi) as large as 14% and elastic modulus differences (Eularian versus Lagrangian) of 44% from ligament tissue sampled from rats. It is therefore critical to maintain consistent (energy conjugate) elastic formulations for reporting mechanical evaluation of soft hydrated tissue.

Multidirectional and unidirectional glenohumeral instability constitute an important clinical problem, particularly in the athlete. Numerous methods have been described for treatment of glenohumeral instability, including closed management, open and arthroscopic procedures, but none have achieved universal success. The purpose of this study was to evaluate the effect of laser energy at non-ablative energy densities on the mechanical properties of joint capsular tissues in a rabbit model. Femoropatellar joint capsular tissues from 12 mature New Zealand white rabbits were harvested and divided using a randomized block design into three treatment groups with laser at 5 W, 10 W and 15 W, and one control group. Mechanical testing was performed before and after application of laser energy. The application of laser energy resulted in 9%, 26% and 38% reduction in capsular tissue length for the 5-W, 10-W and 15-W group, respectively. Laser energy caused a significant decrease in tensile stiffness in the 10-W and 15-W groups only (P0.05). Laser energy did not change the relaxation properties of capsular tissue at any energy density. The loads required to return specimens to their original length were significantly lower for the 5-W group than for the 10-W and 15-W groups. This study demonstrates that significant capsular shrinkage can be achieved with the application of non-ablative Ho:YAG laser energy without detriment to the relaxation properties of the tissue, although at higher energy densities, laser energy did lessen capsular stiffness properties.