In vivo evaluation of biomechanical anterior cervical plate failure

Abstract

Anterior cervical plate (ACP) failure is rarely addressed in the literature. In this retrospective, observational, longitudinal, cohort study, the objectives were to (1) identify incidences of in vivo biomechanical failure in commercially available, US Food and Drug Administration-approved ACP systems, (2) describe modes of failure, (3) suggest structural explanations for system failure, and (4) discuss complications and treatment of patients with failed ACP systems. Investigators retrospectively identified patients who underwent anterior cervical procedures followed by use of ACP as a fusion adjunct and showed evidence of ACP failure on plain radiographs. Components of the ACP system that led to failure were identified and examined. A total of 240 patients received ACP supplementation of anterior cervical fusion constructs during the 9.5-y study period. Evidence of ACP failure was noted in 7 patients (3.3%), and an eighth patient was referred for evaluation after ACP failure. Screw-plate interface failure occurred in all 8 cases. The biomechanical method by which the bone screw head was secured into the vertebral body, or against the ACP, the use of hybrid systems, the surgical technique selected, and host factors were used to determine the rate of failure. Concern for esophageal or other tissue injury often necessitated ACP removal. Screw-plate interface failure, which was found to be the most common mode of biomechanical ACP failure, may occur in hybrid constructs and in systems that do not create a rigid interface between the screw head and the ACP. Surgical technique and patient host factors may also influence the rate of biomechanical construct failure.

Advanced Multi-Axis Spine Testing: Clinical Relevance and Research Recommendations

“…Minimum pre-clinical testing standards for new spinal instrumentation are well-established in terms of wear, fatigue, and yield testing standards, but it is not within the scope of these standards to assess the efficacy of a new device, nor to subject a device to the entirety of in-vivo loading conditions and possible clinical scenarios. This disconnect can lead to the failure of commercially available and FDA-approved devices, 139 but can also lead to limited clinical improvement of new devices over existing products over the long-term. 7,8 It is important that both communities (basic science and clinical) continue to refine efficacy testing protocols through standardized procedures, so that instrumentation is tested under a variety of physiologically relevant conditions, including "worst-case" scenarios.…”

“…The results can be used to compare different component designs in terms of the relative mechanical parameters." 11 There is anecdotal evidence of plate failure at the screw-plate interface, 139 and reported cases of screw failure. 140,141 Human cadaveric testing, under physiological loading conditions prior to clinical use, may have provided valuable data regarding such failures, and allowed a greater understanding of how they may be avoided.…”