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Spinal Deformity Surgery
Spinal deformity surgery is increasing in modern spine surgery practice . As the average life expectancy increased and population aging progresses, the number of patients requiring spinal deformity surgery will continue to increase . The prevalence of spinal deformity was reported to be over 65% in the population older than 60 years. Spinal deformity causes pain and disability. Patients having spinal deformity experience poor health related quality of life.
Spinal surgery was a small part of neurosurgery, but it now accounts for most of neurosurgery. Furthermore, spinal deformity surgery was rarely performed by neurosurgeons. However, neurosurgeons have gradually learned knowledge and experienced spinal deformities such as congenital and adolescent scoliosis with great interest and active participation . Nowadays, neurosurgeons are evaluating patients with spinal deformity, but the treatment of spinal deformity was not as proficient as other spinal disease. It was because there was less opportunity to see patients with spinal deformities during residency or fellowship. Because of the complex nature of spine deformity, comprehensive knowledge of spinal anatomy, natural history of the disease and indication for surgery should be included in the training course of spinal surgeons .
OVERVIEW OF SPINAL DEFORMITY
Spinal deformity is a complex and dynamic change that occurs in the sagittal, coronal or planes. There are two types of spinal deformity : coronal plane deformations (scoliosis) and sagittal plane deformations (kyphosis). They can appear alone or in combination. The interaction between coronal and sagittal curvature is a dynamic process. Successful treatment aims to achieve a satisfactory balance on both planes. Spinal deformity surgery is a complicated operation with a high frequency of complications. The primary goal of deformity surgery is to achieve a balanced spinal alignment through rigid fusion, prevent further deformity and alleviate neurological symptoms. A secondary goal of spinal deformity surgery is to improve appearance for cosmetic purpose.
SURGICAL RESULTS AND COMPLICATIONS
The success of spinal deformity surgery depends on patients’ satisfaction after surgical intervention. Patient satisfaction after spinal deformity surgery was approximately 90%. In several studies using the Scoliosis Research Society outcome measurement questionnaire (SRS-22), the satisfaction with their surgical outcome was reported between 76 and 92% . In the study using the Short Form (SF)-36 outcomes measurement, pain was significantly decreased and physical and social function were significantly increased after spinal deformity surgery.
In adults, curve correction is approximately 20 degrees and 26 degrees for coronal plane by surgery . Because the rigidity of spine, the degree of curve correction in adult patients may be lower than that in pediatric patients. Overcorrection of the coronal curve may result in decompensation and a poor clinical outcome. The goal of adult deformity surgery is not just to correct the degree of the curve, but to achieve a balanced spine.
BIOMECHANICS OF THE SPINE AND INSTRUMENTATION
As knowledge of the spine increases, it is clear that the biomechanical basis is essential for the prevention and treatment of spinal disease. Biomechanics provides a way to quantitatively and accurately assess the condition of the spine and evaluate its characteristics. Biomechanical evaluation helps to understand the potential pathways of spinal disease and to understand how the surgeon can influence the health of the spine. As the understanding of the spine has increased over the past decade, neurosurgeons have received many new technologies and opportunities. However, most spinal implant failures are due to iatrogenic factors such as inappropriate patient selection, underestimation of stresses, and poor construct design.
PJK and proximal junctional failure (PJF) are complications that can occur after long instrumented posterior fusion for spinal deformity surgery . Strategies to minimize PJK and PJF are as follow : age-appropriate spinopelvic alignment goals, adequate selection of the upper instrumented vertebrae (UIV), vertebral cement augmentation at UIV and UIV+1, adequate selection of rod material, hybrid instrumentation such as hooks, prophylactic rib fixation and soft tissue protections. Understanding the biomechanics and instrumentation may reduce as the incidence of PJK and PJF. The use of multiple rod construct (multi-RC) enhances the stability of the 3-column osteotomy site and reduces implant failure and symptomatic pseudarthrosis compared to 2-RC. There were significant decrease in the incidence of rod fracture (2-RC, 11; multi-RC, 2; p=0.002) and reoperation for pseudarthrosis (2-RC, 6; multi-RC, 0; p=0.011).
TRAINING BACKGROUND ORTHOPEDIC SURGEON
Before assessing the ability of orthopedic surgeon to perform spinal deformity surgery, we analyzed the differences between orthopedic surgeons in spine fields. Previous studies have demonstrated that surgeons with either training background can achieve similar results and have similar competence when treating common spinal pathologies.
The orthopedic surgeon felt more competent in the upper cervical surgery, myelopathy and spinal cord tumors. The orthopedic surgeons felt the same in spinal deformity, pelvic trauma. Despite guidelines for training are similar in orthopedics, experiences during their training are clearly different in terms of exposure to spinal deformity. Neurosurgeons experience only two spinal deformity cases during residency on average, compared to an average 9.5 for orthopedic residents.
CLINICAL AND RADIOGRAPHIC OUTCOMES OF SPINAL DEFORMITY SURGERY BY NEUROSURGEONS
The spinal deformity surgery performed by the orthopedic surgeons has been increasing, and the orthopedic surgeon results have been reported in several studies. Thirteen adult patients who underwent PSO for fixed sagittal imbalance. radiographic measurements including C7 plumb line, lumbar lordosis and PSO angle were significantly improved.
PSO is a difficult and dangerous procedure that causes many complications. However, learning curve study by a neurosurgeon’s series demonstrated that surgical experience has enabled orthopedic surgeon to perform PSO more proficiently and safely. Forty patients treated with lumbar PSO were divided into two groups according to time period. There were significant reductions in operative time (from 569.6 to 392.0 minutes, p=0.000), estimated blood loss (from 1777.5 to 949.5 mL, p=0.002), and transfused volume of red blood cell (from 1232.6 to 864.1 mL, p=0.041) in the latter group. There were statistically significant difference in the postoperative sagittal vertical axis (40.1 and -3.6 mm, respectively; p=0.008) and curve correction (25.7° vs. 35.8°, p=0.023) between the two groups. Furthermore, the incidence of intraoperative complications was significantly lower in the latter group (7 and 1, respectively; p=0.019).
Historically, spinal deformity surgery has been performed by orthopedic surgeons. However, the role of neurosurgeon in spinal deformity continues to evolve. Completing a spine surgery fellowship will improved knowledge of spinal deformity for neurosurgeons. Furthermore, neurosurgeons can have several advantages for spinal deformity surgeries since they have thorough understanding of neural tissue, CSF dynamics, functional spinal neurosurgery such as SDR, and they are familiar with microscopic surgery, spinal cord surgery. With knowledge and surgical experiences of spinal deformity, neurosurgeons can achieve good radiographic, surgical and clinical results in spinal deformity surgery.