Comparison of biomechanical studies of disc repair devices based on a systematic review.

BACKGROUND CONTEXT: A variety of solutions have been suggested as candidates for the repair of the annulus fibrosis (AF), with the ability to withstand physiological loads of paramount importance. PURPOSE: The objective of our study was to capture the scope of biomechanical test models of AF repairs. We hypothesized that common test parameters would emerge. STUDY DESIGN: Systematic Review METHODS: PubMed and EMBASE databases were searched for studies in English including the keywords "disc repair AND animal models," "disc repair AND cadaver spines," "intervertebral disc AND biomechanics," and "disc repair AND biomechanics." This list was further limited to those studies which included biomechanical results from annular repair in animal or human spinal segments from the cervical, thoracic, lumbar and/or coccygeal (tail) segments. For each study, the method used to measure the biomechanical property and biomechanical test results were documented. RESULTS: A total of 2,607 articles were included within our initial analysis. Twenty-two articles met our inclusion criteria. Significant variability in terms of species tested, measurements used to quantify annular repair strength, and the method/direction/magnitude that forces were applied to a repaired annulus were found. Bovine intervertebral disc was most commonly used model (6 of 22 studies) and the most common mechanical property reported was the force required for failure of the disc repair device (15 tests). CONCLUSIONS: Our hypothesis was rejected; no common features were identified across AF biomechanical models and as a result it was not possible to compare results of preclinical testing of annular repair devices. Our analysis suggests that a standardized biomechanical model that can be repeatably executed across multiple laboratories is required for the mechanical screening of candidates for AF repair. CLINICAL SIGNIFICANCE: This literature review provides a summary of preclinical testing of annular repair devices for clinicians to properly evaluate the safety/efficacy of developing technology designed to repair annular defects after disc herniations.