The therapeutic efficacy of scoliosis is influenced by many factors, such as the severity of deformity, spine flexibility, patient's age, type of deformity, and combined other deformities. Severe scoliosis is more difficult to treat than usual ones. As the spine deformity is severe and stiff, and the spinal cord has poor tolerance to the traction. It is difficult to complete the correction, and the probability of nerve deficit increases. Moreover, because severe scoliosis is usually combined with heart or lung disfuncitons, the operation is of relatively high risk.
The scoliosis severity is the chief factor that may affect the outcomes of deformity correction. Usually, if the coronal Cobb's angle is more than 80° and the spine flexibility is less than 20%, anterior loosen combined with halo-pelvic traction should be accepted, then followed by posterior correction in the second stage. (Fig 1, 2, 3, 4, 5, 6, 7, 8) For the patients with neurological symptoms preoperatively, halo-pelvic traction can also be used to prevent the neurological deficit from aggravating. As the spinal cord can creep slowly, and the halo-pelvic traction can provide gentle correction on spine, a good correction can be achieved. Furthermore, even if neurological complication appears during traction, the halo-pelvic device can be adjusted to relieve it. Therefore, although the halo-pelvic device has some disadvantages (e.g. hardware complicated and nursing problems), it is an alternative method to the prevention of neurovascular complications in the treatment of severe and rigid scoliosis without any major or permanent neurological deficit.
For those cases with the spine flexibility less than 10%, remained Cobb angle more than 60~70° after halo-pelvic traction, nerve deficit reappear in the later stage of traction, and most severe congenital scoliosis up the adolescent age, it is difficult to get a good correction only using the posterior bar rotation in the second stage, so osteotomy should be used(Fig 9, 10, 11, 12, 13, 14, 15). According to this research, the spine flexibility of the first group is obviously less than the second group; however, the correction rate has no significant difference between the two teams. It is proved that osteotomy is very effective for the correction of the severe scoliosis.
Though osteotomy is useful in the treatment of scoliosis, it can bring some complications, especially the nerve deficit. Bradford etc. had performed 24 cases of osteotomy, and 3 of those had nerve deficit (12.5%) [10]. Among the 3 cases, muscle strength of ankle flexion weakened in 2 cases, and quadriceps femoris weakened in 1 case. Considering the possible rather too big local lumbar curve, vertebral canal decompression was performed, and a good recovery was achieved 6 months later. Berven etc. reported a series of 13 cases undergoing osteotomy [11]. Leg palsy happened in 4 cases (30.8%). These cases got complete reablement half a year later. As to our research, of the 2 cases with leg sensory motor dysfunction, 1 case had undergone osteotomy. The reason was probably that too big range of osteotomy, the spinal cord shrinked after the gap closed, so the vertebral canal was relatively narrow. For this case, SEP showed the latent period increased (>30%), and the wave amplitude decreased (>50%) during operation monitoring. The symptoms disappeared 1 week later after the enlarged decompression of vertebral canal and other treatment postoperatively. All of the cases in this research and other literatures had no nonreversible nerve deficit due to osteotomy.
Current literatures say on the standard of care for severe scoliosis that the treatment approach is different to the subjects in this paper. Dr.Luhmann SJ, and Dr.Lenke LG recently address that anterior and posterior spinal fusion of large thoracic curves allows greater coronal correction of thoracic curves between 70 degrees and 100 degrees, when compared with PSF alone using thoracic hook constructs, but not with the use of thoracic pedicle screw constructs[12]. Scoliosis surgeons not using pedicle screw constructs need to decide if the modest improvement in coronal correction with a combined approach justifies its routine use in this patient population.
Dobbs MB and Lenke LG said in their patient population with often restrictive preoperative pulmonary function [13], a posterior-only approach with the use of an all-pedicle screw construct has the advantage of providing the same correction as an anterior/posterior spinal fusion, without the need for entering the thorax and more negatively impacting pulmonary function.
One of the main technical problems we encountered in this mode of treatment is how to protect spinal cord during pedical subtraction osteotomy. Procedures such as osteotomy may be associated with a significant threat of neurological complications. In my experiences, we must stick to 3 key points (1) A temporary rod must be used inserting to the convex side after osteotomy on this side to prevent shear forces; (2) Do the additional decompression after derotation and closing of the osteotomy gap to confirm there is no compression to the cord; (3) SEP or MEP monitoring and wake-up test during and after the derotation correction. Because experiences with this procedure are fairly recent, longer follow-up is required to confirm whether this technique is reliable and efficacious.