RESUMEN
PURPOSE: Variation in rib numbering has been noted in adolescent idiopathic scoliosis (AIS), but its effect on the reporting of fusion levels has not been studied. We hypothesized that vertebral numbering variations can lead to differing documentation of fusion levels. METHODS: We examined the radiographs of 161 surgical AIS patients and 179 control patients without scoliosis. For AIS patients, the operative report of fusion levels was compared to conventional vertebral labeling from the first thoracic level and proceeding caudal. We defined normal counts as 12 thoracic (rib-bearing) and five lumbar (non-rib-bearing) vertebrae. We compared our counts with data from 181 anatomic specimens. RESULTS: Among AIS patients, 22 (14 %) had an abnormal number of ribs and 29 (18 %) had either abnormal rib or lumbar count. In 12/29 (41 %) patients, the operative report differed from conventional labeling by one level, versus 3/132 (2 %) patients with normal numbering (p < 0.001). However, there were no cases seen of wrong fusion levels based on curve pattern. Among controls, 11 % had abnormal rib count (p = 0.41) compared to the rate in AIS. Anatomic specimen data did not differ in abnormal rib count (p = 1.0) or thoracolumbar pattern (p = 0.59). CONCLUSIONS: The rate of numerical variations in the thoracolumbar vertebrae of AIS patients is equivalent to that in the general population. When variations in rib count are present, differences in numbering levels can occur. In the treatment of scoliosis, no wrong fusion levels were noted. However, for both scoliosis patients and the general population, we suggest adherence to conventional labeling to enhance clarity.
RESUMEN
BACKGROUND: A relationship between spinal distraction and correction of the curvature of scoliosis has long been recognized. While attempts have been made to define the height that is lost with progression of scoliosis, much less information is available to define the height that is gained as a result of surgical correction of the curve and to quantify additional spinal growth after spine fusion. METHODS: The present study included 116 patients (mean age, 14.8 years) who underwent spinal instrumentation and fusion for the treatment of idiopathic scoliosis. The study group included ninety-one female patients and twenty-five male patients; all Lenke curve types were represented. The Cobb angle and the T1-L5 spinal height were evaluated on preoperative, postoperative, and two-year follow-up radiographs. Kyphosis, lordosis, and T1-L5 spinal length were measured on lateral radiographs. The Scoliosis Research Society (SRS) questionnaire was completed prior to surgery and at each visit. Multivariate linear regression defined the relationship between spinal height gain, Cobb angle correction, and other variables as well as final spinal height. RESULTS: The mean spinal height gain due to surgery was 27.1 mm (median, 25.1 mm; interquartile range, 14.5 to 37.9 mm; range, -3.8 to 66.1 mm). The magnitude of curve correction (mean, 38.2°; range, 6° to 67°), the number of vertebral levels fused (mean, 9.9; range, three to sixteen), and the preoperative stature (standing height) of the patient were all significant predictors (p < 0.01) of spinal height gain (R2 = 0.8508 for multivariate model). The mean changes in kyphosis and lordosis were small and were not significant predictors. An additional 4.6 mm of mean spinal height was gained at the time of the two-year follow-up; this increase was significantly related to young age, male sex, shorter fusions, and a Risser stage of ≤2 at the time of surgery (p < 0.01 for all in multivariate analysis). The SRS-30 scores improved significantly (p < 0.0001), independent of spinal height gain. CONCLUSIONS: Patients undergoing surgical correction of idiopathic scoliosis gain substantial height related to the magnitude of surgical correction, the number of levels fused, and preoperative stature. Continued spine growth by two years after surgery is associated with shorter fusions, skeletal immaturity, young age, and male sex. Height gain is a quantifiable outcome of the surgical correction of scoliosis.