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A Classification of Growth Friendly Spine Implants

Skaggs, David L. MD*; Akbarnia, Behrooz A. MD; Flynn, John M. MD; Myung, Karen S. MD, PhD*; Sponseller, Paul D. MD§; Vitale, Michael G. MD; Approved by the Chest Wall and Spine Deformity Study Group, the Growing Spine Study Group, Pediatric Orthopaedic Society of North America and the Scoliosis Research Society Growing Spine Study Committee

Journal of Pediatric Orthopaedics: April/May 2014 - Volume 34 - Issue 3 - p 260–274
doi: 10.1097/BPO.0000000000000073
Spine

Background: Various types of spinal implants have been used with the objective of minimizing spinal deformities while maximizing the spine and thoracic growth in a growing child with a spinal deformity.

Purpose: The aim of this study was to describe a classification system of growth friendly spinal implants to allow researchers and clinicians to have a common language and facilitate comparative studies. Growth friendly spinal implant systems fall into 3 categories based upon the forces of correction the implants exert on the spine, which are as follows: Distraction-based systems correct spinal deformities by mechanically applying a distractive force across a deformed segment with anchors at the top and bottom of the implants, which commonly attach to the spine, rib, and/or the pelvis. The present examples of distraction-based implants are spine-based or rib-based growing rods, vertical expandable titanium rib prosthesis, and remotely expandable devices. Compression-based systems correct spinal deformities with a compressive force applied to the convexity of the curve causing convex growth inhibition. This compressive force may be generated both mechanically at the time of implantation, as well as over time resulting from longitudinal growth of vertebral endplates hindered by the spinal implants. Examples of compression-based systems are vertebral staples and tethers. Guided growth systems correct spinal deformity by anchoring multiple vertebrae (usually including the apical vertebrae) to rods with mechanical forces including translation at the time of the initial implant. The majority of the anchors are not rigidly attached to the rods, thus permitting longitudinal growth over time as the anchors slide over the rods. Examples of guided growth systems include the Luque trolley and Shilla.

Conclusions: Each system has its benefits and shortcomings. Knowledge of the fundamental principles upon which these systems are based may aid the clinician to choose an appropriate treatment for patients. Having a common language for these systems may aid in comparative research. Vertical expandable titanium rib prosthesis is used with humanitarian exemption. The other devices mentioned in this manuscript are not approved for growing constructs by the Food and Drug Administration and are used off-label.

*Children’s Orthopaedic Center, Children’s Hospital Los Angeles, Los Angeles

San Diego Center for Spinal Disorders, Rady Children’s Hospital, La Jolla, San Diego, CA

Children’s Hospital of Philadelphia, Philadelphia, PA

§Johns Hopkins Children’s Center, Baltimore, MD

Morgan Stanley Children’s Hospital, New York, NY

All figures in this manuscript are used with permission of the Children’s Orthopaedic Center.

D.L.S.: Grants: POSNA and SRS: Grants paid to Columbia University. Consulting: Biomet; Medtronic; BeachBody LLC. Board Membership: Pediatric Orthopaedic Society of North America, Growing Spine Study Group, Scoliosis Research Society, Growing Spine Foundation. Expert testimony: legal expert in medical med. Mal. Cases (<5% of income). Payment for lectures including service on speakers bureaus: Biomet; Medtronic; Stryker. Patents: Biomet (osteotome). Royalties: Biomet; Medtronic. Other: Institutional support from Medtronic. B.A.A: Royalties: DePuy Spine Nuvasive. Consultant: Nuvasive, K2M, Ellipse, K Spine. Stock/stock options: Nuvasive, Ellipse, K Spine, Nocimed. Research support: DePuy Spine, Nuvasive. Board member: Growing Spine Foundation Scoliosis Research Society Pediatric Orthopaedic Society San Diego Spine Foundation. J.M.F.: Royalties: Biomet; Wolters Kluwer Health - Lippincott Williams & Wilkins. Board member: Pediatric Orthopaedic Society of North America; Scoliosis Research Society; AAOS. P.D.S.: Royalties: Globus Medical; DePuy, A Johnson & Johnson Company; Journal of Bone and Joint Surgery oakstone medical. Consultant: DePuy, A Johnson & Johnson Company. Research support: DePuy, A Johnson & Johnson Company. Board member: Scoliosis Research Society. M.G.V.: Royalties: Biomet. Consultant for: Biomet; Stryker. Research support: Synthes. Board Member: Chest Wall and Spinal Deformity Study Group; Scoliosis Research Society; Pediatric Orthopaedic Society of North America; American Academy of Pediatrics-Orthopedic Section. K.S.M. declares no conflict of interest.

Reprints: David L. Skaggs, MD, Children’s Orthopaedic Center, Children’s Hospital of Los Angeles, 4650 Sunset Blvd., Mailstop #69, Los Angeles, CA 90027. E-mail: dskaggs@chla.usc.edu.

© 2014 by Lippincott Williams & Wilkins