2015 ISAKOS Biennial Congress ePoster #823

Tensile Properties of the Human Acetabular Labrum and Hip Labral Reconstruction Grafts

Fernando Portilho Ferro, MD, Goiania, GO BRAZIL
Marc J. Philippon, MD, Vail, CO UNITED STATES
Matthew T. Rasmussen, BS, Vail, CO UNITED STATES
Sean David Smith, MSc, Vail, CO UNITED STATES
Robert F. LaPrade, MD, PhD, Chanhassen, MN UNITED STATES
Coen Abel Wijdicks, PhD, München, Bavaria GERMANY

Steadman Philippon Research Institute, Vail, CO, USA

FDA Status Not Applicable

Summary: An in vitro biomechanical research model was developed and utilized to compare the tensile properties of the human acetabular labrum with those of several grafts that are used for labral reconstruction surgery

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Abstract:

Background

In cases where the acetabular labrum is severely damaged and irreparable, labral reconstructions are becoming an increasingly preferred means of preserving the fluid seal effect of the labrum. With the advent of labral reconstructions, multiple soft tissue graft options have been proposed; however, the graft that most closely replicates the biomechanical properties of the native labrum remains undetermined.

Purpose

The purpose of this study was to characterize the tensile properties of the native labrum, as well as iliotibial band, semitendinosus, gracilis, and anterior tibialis grafts, and determine which grafts more closely replicate the biomechanical behavior of the native labrum.

Methods

Five groups – 1) native labrum, 2) iliotibial band, 3) semitendinosus, 4) gracilis, and 5) anterior tibialis – with eight specimens per group were tested. Grafts were tested using a material testing system in response to a step-wise sinusoidal cyclic loading protocol. Uniaxial tensile loads were initially applied from 20-50 N for 100 cycles at 0.5 Hz, followed by incremental increases of 50 N in the upper force every 100 cycles until failure or successful completion of 100 cycles at 300 N. This protocol was designed to be representative of the progressive loading experienced during rehabilitation. Cyclic displacement was recorded following 100 (50 N), 200 (100 N), 300 (150 N), 400 (200 N), 500 (250 N) and 600 (300 N) cycles.

Results

The mean elongations following 100 cycles from 20-50 N (non-dysplastic hip, walking )were similar for all groups: 0.68 mm [95% Confidence Interval, 0.57, 0.78] for the native labrum, 0.68 mm [0.47, 0.89] for the iliotibial band, 0.68 mm [0.51, 0.84] for the semitendinosus, 0.62 mm [0.46, 0.79] for the gracilis, and 0.66 mm [0.58, 0.73] for the anterior tibialis. Following 100 cycles from 20-300 N (dysplastic hip, jogging) (600 cycles total), the mean elongation of the labrum was 4.53 mm [3.71, 5.35] and that of the IT-band, semitendinosus, gracilis, and anterior tibialis were 4.65 mm [3.23, 6.07], 4.41 mm [3.45, 5.36], 5.12 [3.09, 7.16], and 5.33 mm [4.40, 6.25], respectively. The gracilis graft had the lowest average diameter and the highest standard deviation for elongation.

Conclusion

All tested grafts resulted in similar amounts of elongation during a progressive cyclic loading protocol that simulated how a graft would be loaded after a labral reconstruction procedure. Because of the lowest average diameter, the gracilis may not be preferable for larger hips.

Clinical Relevance: All tested grafts exhibited similar cyclic elongation behavior to the native labrum and should be considered viable acetabular labrum reconstruction graft options.

Keywords: hip arthroscopy; labrum; reconstruction; graft elongation; iliotibial band; semitendinosus; gracilis