Abstract
BackgroundHigh primary stability is the key prerequisite for safe osseointegration of cementless intervertebral disc prostheses. The aim of our study was to determine the primary stability of intervertebral disc prostheses with two different anchoring concepts – keel and spike anchoring.MethodsTen ActivL intervertebral disc prostheses (5 x keel anchoring, 5 x spike anchoring) implanted in human cadaver lumbar spine specimens were tested in a spine movement simulator. Axial load flexion, extension, left and right bending and axial rotation motions were applied on the lumbar spine specimens through a defined three-dimensional movement program following ISO 2631 and ISO/CD 18192-1.3 standards. Tri-dimensional micromotions of the implants were measured for both anchor types and compared using Student’s T-test for significance after calculating 95 % confidence intervals.ResultsIn the transverse axis, the keel anchoring concept showed statistically significant (p < 0.05) lower mean values of micromotions compared to the spike anchoring concept. The highest micromotion values for both types were observed in the longitudinal axis. In no case the threshold of 200 micrometers was exceeded.ConclusionsBoth fixation systems fulfill the required criteria of primary stability. Independent of the selected anchorage type an immediate postoperative active mobilization doesn’t compromise the stability of the prostheses.
Highlights
High primary stability is the key prerequisite for safe osseointegration of cementless intervertebral disc prostheses
In the longitudinal axis the highest values for micromotions were observed, which lay in any case below threshold of 200 μm
Osteoporosis is a surgical contraindication for implantation of intervertebral disc prosthesis [11]
Summary
High primary stability is the key prerequisite for safe osseointegration of cementless intervertebral disc prostheses. The aim of our study was to determine the primary stability of intervertebral disc prostheses with two different anchoring concepts – keel and spike anchoring. In contrast to spinal fusion techniques, the implantation of an artificial disc is intended to maintain the segmental mobility and to avoid an adjacent level disease. There is increased medical interest for a successful treatment of disc diseases such as the use of artificial discs. This surgical treatment aims at restoring height of the segment and improving its biomechanical function. The development of cementless implants in the last years has led to different anchoring concepts. The micromotion at the implant–bone interface has a significant effect on the primary stability of the prosthesis and can be determinant for obtaining long-term stability through adequate osseointegration
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