Scoliosis surgery Correcting large deformities through small incisions By Prof Wong Hee Kit and Dr John Ruiz Scoliosis is defined as a sideways bending of the spine. Although there are many types of scoliosis, the most common is idiopathic scoliosis. The spinal deformity may affect a person’s trunk balance leading to any combination of an uneven waistline, uneven shoulders, body leaning to one side, and scapular or lumbar prominence. This may have consequences on a person’s self-image, activity level, and employment potential. In its most advanced stage of deformity, scoliosis can have undesirable effects on pulmonary function. Idiopathic scoliosis primarily affects pre-pubertal boys and girls. From the national scoliosis screening programme initiated by the Health Promotion Board, it was determined that the overall prevalence rate of idiopathic scoliosis in the Singapore school population in 1997 was 0.93% in girls, and 0.25% in boys. This translates to about 3% of the population. Many factors influence the treatment plan for this condition. These include the child's age, the remaining growth potential, the curve pattern and magnitude, the anticipated rate of progression, and the person’s body appearance. Bracing is the standard treatment to prevent curve progression in moderate-sized curves in a growing child. Surgery is necessary when the curve is large (>50 degrees) and progressive, particularly in a skeletally immature child. The goals of surgery are to prevent progression of the curve and to achieve a balanced spine. Curve progression is prevented by joining the individual vertebrae in the curve together by a process called spinal fusion; while correction of the spinal deformity and restoration of spinal alignment are achieved by means of metallic implants consisting of a combination of hooks, screws, and rods. Then and now Traditional open spine surgery for scoliosis is performed either on the dorsal spine through a posterior approach, or anterior spine through thoracotomy. Both involve cutting through muscle attachments and are characterised by significant blood loss and, often, a large scar either down the centre of the back or along the side of the chest wall. Advances in surgical techniques have allowed the anterior spinal column to be accessed by minimally invasive techniques without the potential disadvantage of a formal long thoracotomy incision and splitting apart of the ribs. This minimally invasive surgical technique is basically a different surgical approach that is less morbid, but still meets all the goals and objectives of scoliosis surgery. Such methods are made possible by thoracoscopy, which combines the science of endoscopy (video-assisted surgery) with thoracotomy (access to chest, or thoracic spine). This method of treatment began in the early 1900s, starting with Jacobaeus who used it to treat chest diseases. However, it was only in the early 1990s that Regan in Dublin, Ireland began his work on thoracoscopic treatment of spinal diseases, and sometime in 1994 Rosenthal described thoracoscopic-assisted discectomy. This paved the way for the rapid evolution of this surgical method for spinal deformity that went hand-in-hand with the development of spinal implants that could be safely implanted even with a minimally invasive approach. In thoracoscopic surgery for the spine, the spine surgeon makes four to five small incisions on the right side of the chest wall – precisely located keyhole incisions – to allow access to the thoracic and even the upper lumbar spine. Specially designed endoscopic instruments pass through these keyhole incisions and are manoeuvered during surgery. The NUH experience Treating scoliosis using thoracoscopic methods at the National University Hospital (NUH) began as early as 1999. The results of this method of surgery were analysed and compared to the traditional surgical method of posterior scoliosis surgery. Because there is less tissue disrupted in reaching the spine in thoracoscopic surgery, blood loss was noted to be much less, and there was less disruption to the rib cage muscles and soft tissues. With these two observations, it was therefore expected that post-operative soreness would be much less compared to posterior scoliosis surgery. Thoracoscopic surgery also required fewer vertebrae to be fused for the same effect. Despite the fewer vertebral levels, curve correction and maintenance after thoracoscopic surgery was better compared to that in the posterior technique. In addition, the surgical scars were also dramatically less noticeable, a fact very much appreciated by the patients and their parents. In the long-term, patients who underwent thoracoscopic surgery were much more satisfied with the procedure and were happier with their final body appearance compared to those who underwent traditional posterior surgery. The main disadvantage of the thoracoscopic technique is that patients have to use a brace in the post-operative period for about 3 months. This is not necessary in traditional posterior surgical methods. The NUH experience mirrors results of the few centres in the world that perform thoracoscopic spine surgery. While these results are encouraging, not all types of scoliotic curves are amenable to this surgical technique. Idiopathic curves that require only fusion of the thoracic spine are suitable candidates. The curve should be less than 80 degrees, and should bend out to less than 45 degrees. Under these conditions, it is possible to achieve about 70% to 75% correction of the main curve, substantial reduction in the rotational deformity, and all without having a long midline scar at the back of the patient. Structural double and triple curves are not suitable for this technique. What’s there for the future? There is potential for expanded applications of this technique to other scoliotic curves. Already, advancements in metallurgy are having an effect on the production of more rigid as well as “smart” spinal implants, thus allowing the possibility of “self-correction” of the curve as well as obviating the need for the requisite 3-month post-operative bracing. Better imaging of the spine using surgical navigation could also improve the speed and safety of the procedure, reducing the traditionally long learning curve needed to master the surgical technique. Professor Wong Hee Kit is the chief and senior consultant at the Department of Orthopaedic Surgery at the National University Hospital, and a professor at the Department of Orthopaedic Surgery at the Yong Loo Lin School of Medicine at the National University of Singapore. Dr John Nathaniel M Ruiz is a medical officer at the Department of Orthopaedic Surgery at the National University Hospital, Singapore.