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An in vivo kinematic comparison of dynamic lumbar stabilization to lumbar discectomy and posterior lumbar fusion using radiostereometric analysis

Soo-An Park, MD, PhD,1 Amir H. Fayyazi, MD,2 Kenneth S. Yonemura, MD,3 Bruce E. Fredrickson, MD,4 Nathaniel R. Ordway, MS5

1Spine Center, Seoul St Mary's Hospital, The Catholic University of Korea, College of Medicine, Seoul, South Korea 2VSAS Orthopaedics, Institute for Advanced Healthcare, Allentown, PA 3Wasatch Neurological Surgery, Bountiful, UT 4Department of Orthopedics, Syracuse VA Medical Center, Syracuse, NY 5Department of Orthopedic Surgery, SUNY Upstate Medical University, Syracuse, NY

Abstract 

Background

Biomechanical studies have shown that dynamic stabilization restores the neutral zone and stabilizes the motion segment. Unfortunately, there are limitations to clinical measurement of lumbar motion segments when using routine radiographs. Radiostereometric analysis is a 3-dimensional technique and can measure the spinal motion segment more accurately than techniques using plain film radiographs. The purpose of this study was measure and compare the range of motion after dynamic stabilization, posterior lumbar fusion (PLF), and lumbar discectomy.

Methods

Four patients who underwent lumbar decompression and dynamic stabilization (Dynesys; Zimmer Spine, Inc., Warsaw, Indiana) for treatment of lumbar spondylosis were compared with 4 patients with a similar diagnosis who were treated by PLF and pedicle screw fixation (PLF group) and 8 patients who had undergone lumbar microdiscectomy (discectomy group) for treatment of radiculopathy. During the surgical procedure, 3 to 5 tantalum beads were placed into each of the operative segments. The patients were followed up postoperatively at 1 month, 1 year, and 2 years. At each follow-up time point, segmental motions (flexion, extension, and total sagittal range of motion [SROM]) were measured by radiostereometric analysis.

Results

Flexion, extension, and SROM measured 1.0° ± 0.9°, 1.5° ± 1.3°, and 2.3° ± 1.2°, respectively, in the Dynesys group; 1.0° ± 0.6°, 1.1° ± 0.9°, and 1.5° ± 0.6°, respectively, in the PLF group; and 2.9° ± 2.4°, 2.3° ± 1.5°, and 4.7° ± 2.2°, respectively, in the discectomy group. No significant difference in motion was seen between the Dynesys and PLF groups or between the Dynesys and discectomy groups in extension. Significant differences in motions were seen between the PLF and discectomy groups and between the Dynesys and discectomy groups in flexion (P = .007) and SROM (P = .002). There was no significant change in the measured motions over time.

Conclusions

In this study a significantly lower amount of motion was seen after dynamic stabilization and PLF when compared with discectomy. A future study with a larger cohort is necessary to examine what effect, if any, these motions have on clinical outcomes.

keywords: 
Spine surgery, RSA, range of motion, kinematics
Volume 6
doi: 
10.1016/j.ijsp.2012.02.003