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Global introduction: SRS focus issue on motion preservation.

It is a testament to the open-mindedness of the Scoliosis Research Society (SRS) that the Board was receptive to the concept of a Focus Issue on “Motion Preservation.” The SRS is the oldest, most revered spine organization in the world. One cannot expect the membership of the SRS to jump headfirst into each new emerging spine technology—but it is a powerful statement that the SRS has chosen to evaluate through peer review and academic discourse the merits and possible complications of motion preservation. A cross-section of articles across a wide range of subjects is included in the 2003 SRS Spine Focus Issue. The information is divided into three major sections: 1) disc arthroplasty, lumbar and cervical; 2) restricting the number of fusion levels; and 3) emerging technologies for scoliosis, growth rods, and vertebral body stapling. The disc arthroplasty section contains a summary of wear debris, particle-induced osteolysis, and cytokine reactions that are common to all total joint replacements. These are areas that the spine surgeon needs to become knowledgeable of if he or she wants to manage the longterm effects of motion preservation—moving parts produce wear debris, and the complications of the inflammatory response escalate with time, whereas with conventional spinal arthrodesis, they dissipate. The comparative rates of porous ingrowth appear to be more favorable for spinal prostheses compared to the appendicular skeleton using animal models. Preliminary results of four series of disc replacement are presented: Bryan, Porous Coated Motion (PCM), ProDisc, and S.B. Charité types in attempt to provide a well-balanced forum. Dave Polly, MD, offers a “voice of reason” in the face of the tidal wave of enthusiasm over disc replacement. In the Clinical Deformity section, the Lenke classification of scoliosis is used to provide a template to perform selective fusions of the spine and retain as many remaining mobile segments as possible. Posterior selective instrumentation is presented as well as a series of anterior dual paravertebral rods. A paper on the effects of preserving the lumbosacral joint (L5–S1) is also included. Emerging technologies in the field of motion preservation for treating scoliosis in avoidance of fusion include: vertebral body growth plate stapling, posterior growth rods, and video-assisted thoracoscopic surgery (VATS). Another technique of anterior vertebral body osteotomy and preserving the disc spaces has the potential of retaining motion after deformity correction. No doubt these are all controversial areas, but they are also consistent with the mission statement of the Scoliosis Research Society “to foster optimum care of the patient with any disorder that may affect the shape, alignment or function of the spine, throughout life.” It is not the function of the SRS to jump on every new bandwagon, but it is a tribute to the SRS that an overview of the latest innovative motion preserving technology is provided to give the reader a framework to evaluate whether these techniques deserve more widespread application.