Biomechanical studies on cervical total disc arthroplasty: A literature review

BackgroundMany models of cervical disc prostheses are currently commercially available or under clinical trial, and are based on several design concepts and built employing different materials. This paper is targeted to the understanding of the possible relationships between the geometrical, mechanical and material properties of the various cervical disc prostheses and the restoration of a correct biomechanics of the implanted spine.MethodsPapers about cervical disc arthroplasty, based on ex vivo testing, mathematical models, and radiographic measurements, were included in the present review.FindingsAlthough disc arthroplasty was found to be generally able to preserve a nearly physiological motion in the cervical spine, several alterations in the spine biomechanics due to disc arthroplasty were reported in the literature. An increase of the range of motion at the implanted level was observed in some ex vivo studies. Loss of mobility and heterotopic ossification were reported in radiographic investigations. Loss of lordosis at the implanted level was detected as well. Wear debris was usually found very limited and device stability seemed not to be an actual problem.InterpretationThe possible relationships between the observed alterations in the spine biomechanics after disc arthroplasty and the properties of the various cervical disc prostheses have been reviewed. Clinical studies are needed to assess the validity of the considerations inferred from the biomechanical papers.