Endoscopic mechanical spinal hemiepiphysiodesis modifies spine growth

Study Design. An in vivo porcine model of progressive scoliosis as an inverse analog of a proposed method of early surgical treatment. Objectives. To test the hypothesis that scoliotic curvatures may be repeatedly created using anatomically based vertebral staples and thoracoscopic surgical procedures. Summary of Background Data. Staple hemiepiphysiodesis is an established method for treating knee deformities. Similar procedures have so far failed to arrest or correct deformities of the spine. While experimental studies continue to suggest that spine growth is modifiable, no prior clinically translatable method has been shown to clearly and consistently alter vertebral growth. Methods. Custom spine staples were implanted into midthoracic vertebrae of seven skeletally immature normal pigs. Each staple spanned an intervertebral disc and two growth plates and was fixed to adjacent vertebrae with screws. The animals were anesthetized biweekly for radiography during the 8-week study period. Final radiographs were taken after spine harvest. Initial and final postoperative Cobb angles were compared statistically. Results. Five animals completed the protocol with a weight increase of 142% in 8 weeks. Coronal plane curvatures increased significantly with time, from 0.8 degrees (+/- 1.8) to 22.4 degrees (+/- 2.8; P = 0.0001). On average, sagittal plane curvatures did not increase with time. Conclusions. Spinal hemiepiphysiodesis using an anatomically based implant and minimally invasive procedures repeatedly induced spine curvature in a normal porcine model. These techniques may slow, and perhaps even correct, early progressive spine deformity without long rod instrumentation or fusion.