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Multilevel Spinal Growth Modulation With an Anterolateral Flexible Tether in an Immature Bovine Model

Newton, Peter O. MD*; Faro, Fran D. MD; Farnsworth, Christine L. MS*; Shapiro, Gary S. MD; Mohamad, Fazir MD; Parent, Stefan MD, PhD*; Fricka, Kevin MD§

doi: 10.1097/01.brs.0000188267.66847.bf
Basic Science

Study Design. A bovine model was used to evaluate the effects of a multilevel anterolateral flexible tether in a growing spine.

Objective. To evaluate the radiographic changes in a growing spine with a multilevel anterolateral tether.

Summary of Background Data. Spinal growth modulation has long been considered as a conceptually attractive and elegant possible alternative to arthrodesis in the treatment of idiopathic scoliosis. Although some experimental studies have described spinal growth modulation, few have described a purely mechanical tether. Clinical studies of spinal epiphysiodesis have described inconsistent curve stabilization and/or correction.

Methods. A total of 33 one-month-old male calves underwent a single thoracotomy and placement of vertebral screws at T6–T9. In 11 animals, one screw per level was connected by a 3/16 in. stainless steel cable (single tether). In 11 animals, two screws per level were connected by two cables (double tether). In the remaining 11 animals, single screws in each level were left unconnected (control). After 6 months, the spines were harvested and underwent radiographic analysis.

Results. In the control group, there was little change in the coronal and sagittal measurements during the survival period. In the single tether group, there was variable instrumentation fixation and inconsistent creation of coronal deformity, which ranged from 0° to 31°. The double-tether group had more consistent creation of deformity, ranging from 23° to 57°.

Conclusions. Given adequate bony fixation, a flexible lateral spinal tether can affect growth modulation. This technique of growth modulation may serve as a future fusionless method of correction in a growing patient with scoliosis.

Single-cable anterolateral tethers of four vertebrae in growing bovine spines were compared with double-cable tethers and sham controls. After 6 months, spines instrumented with the double-cable construct revealed consistent deformity creation (concave toward the tether), illustrating the growth modulation potential of an adequately fixed flexible spinal tether.

From the *Children’s Hospital and Health Center, San Diego, CA; †Illinois Bone and Joint Institute, Chicago, IL; ‡Hospital Kuala Lumpur, Kuala Lumpur, Malaysia; and §University of California–San Diego, San Diego, CA.

Acknowledgment date: July 23, 2004. First revision date: November 9, 2004. Acceptance date: December 17, 2004.

Supported by grants from the Orthopedic Research and Education Foundation and DePuy Spine.

The device(s)/drug(s) that is/are the subject of this manuscript is/are not intended for human use.

Corporate/Industry and Foundation funds were received in support of this work. One or more of the author(s) has/have received or will receive benefits for personal or professional use from a commercial party related directly or indirectly to the subject of this manuscript: e.g., royalties, stocks, stock options, decision making position.

Address correspondence and reprint requests to Peter O. Newton, MD, Children’s Hospital San Diego, 3030 Children’s Hospital, Suite 410, San Diego, CA 92123; E-mail: pnewton@chsd.org

© 2005 Lippincott Williams & Wilkins, Inc.