Abstract
Introduction Current concepts in the treatment of degenerative disc disease include disc replacement. Disc replacement may restore height and lordosis while maintaining motion. This paper reviews the design criteria, biomechanical and biological (wear and safety) testing of the Maverick total disc arthroplasty. The surgical technique and early clinical results of the initial implantations were reviewed (Mathews HH, et al; Spine J. 2004).
Methods The Maverick total disc arthroplasty is a semi-constrained, chrome cobalt metal-on-metal, ball and socket design prosthesis designed to resist shear forces. Various prosthetic sizes allow precise end plate coverage to help prevent subsidence and selective restoration of lordosis and disc height. The posterior location of the ball-and–socket articulation approximates the normal centre of rotation.
The Maverick disc was subjected to axial compression, cadaveric motion, wear testing, and shock transmission studies. Early clinical outcomes were reviewed.
Results Biomechanical testing resulted in no failures, cracks, loss of height or other mechanical damage after subjecting the components to 10 million loading cycles. Cadaveric testing showed maintenance of a range of motion in all planes with no statistically significant (p=.05) differences between the stiffness or range-of-motion measurements in any mode except for extension. Maverick tested at 10 million repetitions of significant bends, estimated to be equivalent to 31.5 years of clinical use, generated only 12 to 14 mm3 of debris. This represents approximately 9% of the anticipated debris of a metal-on-metal hip arthroplasty. No difference in shock transmission between metal-on-metal and metal-on-polyethylene prosthesis designs was demonstrated.
Clinically at 2 years, at least three-quarters of patients obtained an Oswestry success of 15 points or more usually by 3 months after the procedure. Recovery and improvement was significantly quicker when compared to the historical arthrodesis controls. A few approach-related complications and technical failures have been reported. There have been no implant-related failures.
Discussion The most clinically relevant concept in disc replacement may be restoration of spinal balance rather than preservation of motion. Laboratory testing confirms the design rationale of the Maverick disc. Early clinical results are encouraging. Longer term results and more careful study are needed to confirm its efficacy.
The abstracts were prepared by Professor Bruce McPhee. Correspondence should be addressed to him at Orthopaedics Division, The University of Queensland, Clinical Sciences Building, Royal Brisbane & Women’s Hospital, Herston, Qld, Australia
