8 Long-Term Outcomes of Operative Management in Adolescent Idiopathic Scoliosis
The history of surgical treatment for adolescent idiopathic scoliosis (AIS) dates back 100 years ago. 1 After the advent of metallic spinal implants to correct spinal deformity in the middle of 20th century, the ability to correct spinal deformity has shown significant improvement. 2 Because most patients who undergo surgical treatment of AIS are younger than 20 years of age, their life expectancy after the primary surgery is longer than 50 years. To assess the lifelong value of deformity correction surgery for AIS, long-term follow-up studies on the effects of surgical treatment on patients’ health-related parameters are indispensable. This chapter discusses the long-term clinical results of posterior and anterior surgery for AIS, based on studies with a minimum of 10 years of follow-up ( Table 8.1 ). The parameters addressed include the correction rate of scoliotic deformity in each surgical procedure, surgery-related complications, rates and causes of revision surgery, long-term pulmonary function, and lumbar disk degeneration below the lowest instrumented vertebra (LIV). The purpose of surgery in the adolescent is to prevent the consequences of deformity progression in adulthood. An important question remains regarding whether surgical treatment for AIS in children would prevent further progression of lumbar disk degeneration and residual spinal deformity and would help avoid severe deformity-related clinical problems in later years.
History of Surgical Treatment for Adolescent Idiopathic Scoliosis
In the 1910s and 1920s, Russell Hibbs 1 performed long, uninstrumented insitu posterior spinal fusion followed by a long-lasting immobilization with a cast. At the end of 1950s, Paul Harrington 2 was the first to use metallic spinal implants to correct spinal deformity and to enhance spinal fusion. He introduced a hook and rod system for concave-distraction and convex-compression ( Fig. 8.1 ). The next development was initiated by Eduardo Luque, 3 who uses sublaminar stainless-steel wires in combination with L-shaped rods in the 1970s. He used the implant for treatment of neuromuscular scoliosis and later for idiopathic scoliosis. The next generation of spinal instrumentation surgery was introduced by Cotrel and Dubousset 4 (CD instrumentation) at the beginning of the 1980s. They introduced a new concept of deformity correction, the rod rotation maneuver, to correct not only scoliosis but also rotational deformity of the deformed spine. CD instrumentation incorporates a frame construct consisting of two rods with multiple hooks ( Fig. 8.2 ). Similar spinal instrumentation systems, including the Texas Scottish Rite Hospital (TSRH) instrumentation (Dallas, TX), Isola Spine System (Raynham, MA) ( Fig. 8.3 ), and Moss-Miami system (DePuy, Warsaw, IN), had been introduced subsequently around the year 1990. These instruments consisted of two rods with multiple hooks, sublaminar wires, and pedicle screws. Modern sublaminar implants such as titanium cables and high-molecular polyester bands have been developed recently to prevent metal corrosion and to protect the spinal cord.
After Suk et al 5 reported the use of pedicle screws (PSs) for scoliosis correction in 1995, PS instrumentation became a standard operative technique for idiopathic scoliosis around the year 2000 ( Fig. 8.4 ). This transpedicular fixation systems enabled the surgeon to achieve better three-dimensional correction of scoliosis than with previous systems by allowing surgeons to use all available corrective techniques, such as derotation, translation, segmental distraction–compression, and insitu bending of rods. 6 During the past 10 years, there have been significant developments in PS instrumentation with new correction techniques such as direct vertebral rotation (DVR), 7 simultaneous dual rod rotation, and others. 8
With regard to anterior instrumentation for AIS, the Dwyer system was the first system introduced in 1970s. 9 Anterior systems consist of vertebral screws introduced on the convexity of the curve, with a flexible cable between the screws on which a compression force was applied on the convex side of the curve. This system was modified by Zielke with a threaded rod, and with a solid rod in the TSRH system. In the 1980s, the Kaneda device was developed for thoracolumbar-lumbar burst fractures. In 1989, the Kaneda device was modified to a multisegmental anterior spinal system and was used for correction of thoracolumbar scoliosis. 10 A unique character of Kaneda device was that it consisted of two rods and two vertebral screws in each vertebral body for biomechanical superiority and restoration of sagittal alignment of the spine ( Fig. 8.5 ). As a minimally invasive surgery for thoracic curves, video-assisted thoracoscopic techniques (VATSs) have been utilized since the 1990s. 11 The technique involves anterior diskectomy and fusion with single rod instrumentation under endoscopic guidance, and it is commonly used for mild thoracic curves. Due to the recent development of posterior correction surgery, the current practice is that anterior surgery for AIS is conducted in selective cases with thoracolumbar and lumber curves.