Biomechanics Research Today is a free monthly online journal that collates and summarizes the latest research about Biomechanics, including details on mechanics of living organisms, movement, locomotion, prosthetic limbs.

Multidirectional testing of one- and two-level ProDisc-L versus simulated fusions.

Panjabi M, Henderson G, Abjornson C, Yue J

Biomechanics Research Laboratory, Department of Orthopaedics and Rehabilitation, Yale University School of Medicine, New Haven, CT 06520-8071, USA. manoharpanjabi@gmail.com

STUDY DESIGN: An in vitro human cadaveric biomechanical study. OBJECTIVES: To evaluate intervertebral rotation changes due to lumbar ProDisc-L compared with simulated fusion, using follower load and multidirectional testing. SUMMARY OF BACKGROUND DATA: Artificial discs, as opposed to the fusions, are thought to decrease the long-term accelerated degeneration at adjacent levels. A biomechanical assessment can be helpful, as the long-term clinical evaluation is impractical. METHODS: Six fresh human cadaveric lumbar specimens (T12-S1) underwent multidirectional testing in flexion-extension, bilateral lateral bending, and bilateral torsion using the Hybrid test method. First, intact specimen total range of rotation (T12-S1) was determined. Second, using pure moments again, this range of rotation was achieved in each of the 5 constructs: A) ProDisc-L at L5-S1; B) fusion at L5-S1; C) ProDisc-L at L4-L5 and fusion at L5-S1; D) ProDisc-L at L4-L5 and L5-S1; and E) 2-level fusion at L4-L5 to L5-S1. Significant changes in the intervertebral rotations due to each construct were determined at the operated and nonoperated levels using repeated measures single factor ANOVA and Bonferroni statistical tests (P < 0.05). Adjacent-level effects (ALEs) were defined as the percentage changes in intervertebral rotations at the nonoperated levels due to the constructs. RESULTS: One- and 2-level ProDisc-L constructs showed only small ALE in any of the 3 rotations. In contrast, 1- and 2-level fusions showed increased ALE in all 3 directions (average, 7.8% and 35.3%, respectively, for 1 and 2 levels). In the disc plus fusion combination (construct C), the ALEs were similar to the 1-level fusion alone. CONCLUSIONS: In general, ProDisc-L preserved physiologic motions at all spinal levels, while the fusion simulations resulted in significant ALE.

Published 22 May 2007 in Spine, 32(12): 1311-9.
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