Other limitations of this experimental scoliosis model are apparent when contrasting the biomechanics and anatomy of animals and humans32. The postural differences between a quadruped goat and a bipedal human likely create forces on the spine that are not directly comparable. The anatomy of the goat thorax is also more pyramidally shaped and stiffer than the cubical human thorax. However, there are many similarities between the goat thorax and the human thoracic spine, making the goat thorax a reasonable enough approximation of a juvenile human spine that it can provide useful information for the study of progressive scoliosis and its treatment.
Previous attempts to correct scoliosis with anterior fusionless techniques have been disappointing51,52. Nachlas and Borden52 were initially optimistic about their ability to create and correct lumbar scoliosis in a canine model using a (rather weak) staple spanning several vertebral segments. The enthusiasm for this new treatment waned after the application of their staple in three children with progressive scoliosis met with poor results. Other investigators in the past51 have also been dissatisfied with convex stapling as a means of controlling progressive scoliosis.
More recent investigations of convex vertebral body stapling, both in animal models and in juvenile and adolescent scoliosis, however, have offered promising early results with use of improved implants and techniques23,25,43. The use of a shape memory alloy staple tailored to the size of the vertebral body, the application of several staples per level, the instrumentation of all levels of curvature, and the employment of minimally invasive endoscopic approaches all offer substantial improvements over previous fusionless techniques. Patient selection may also play a role in the current success of these fusionless treatments, with perhaps the ideal candidates for this intervention possessing smaller and more flexible single thoracic curves. Yet, with the early clinical success of these stapling procedures, no basic-science data are available to assist in the evaluation of these implants and their effect on the surrounding tissues.
The model used in this study provides a unique environment for the evaluation of novel fusionless techniques with use of objective radiographic, histological, and biomechanical analyses to compare various strategies. Improvements in implant design in this experimental model, with a specific focus on optimizing the fixation to bone and maximizing the tethering effect, may lead to greater control of idiopathic scoliosis in children. ▪
NOTE: The authors would like to thank Michelle Swenson for her technical assistance with the collection of the data.
In support of their research or preparation of this manuscript, one or more of the authors received grants or outside funding from Medtronic Sofamor Danek (Memphis, Tennessee). In addition, one or more of the authors received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity (Medtronic). No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.
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