Abstract
Aim
To evaluate the effect of corrective surgery for adolescent idiopathic scoliosis on pelvic morphology.
Introduction
Pelvic incidence increases linearly with age during childhood and adolescence before stabilising in adulthood. Most scoliosis surgery occurs before adulthood. We tested the hypothesis that during growth, scoliosis surgery alters the normal linear relationship between pelvic incidence and age.
Methods
One hundred patients with 200 radiographs who had undergone surgery for scoliosis were identified. Thirty-eight patients were excluded due to other diagnoses. All patients had posterior surgery for adolescent idiopathic scoliosis. Pre and post-operative lateral radiographs taken at 6 weeks were assessed. Spino-pelvic indices measured were Pelvic Incidence (PI), Sacral Slope (SS), Pelvic Tilt (PT) and the C7 plumb line.
Results
There were 62 patients: 58 females and 4 males. Median age was 14 (range 12-17).
Median pelvic parameters pre-operatively were 49, 39 and11 degrees for PI, SS and PT respectively. Post operative median values were 48, 36 and14 degrees for PI, SS and PT.
Statistical analysis showed no significant differences in pelvic incidence, pelvic tilt or the C7 plumbline between pre- and post-operative values. There was a significant decrease in sacral slope from a median of 39 degrees pre-operatively to 36 degrees post operatively (p=0.007).
There was no statistical difference between these variables when analysed by age or gender, nor were there any correlations between the change in variables.
All values fell within the normal ranges for age related spino-pelvic parameters.
Conclusion
Corrective surgery for adolescent idiopathic scoliosis does not alter pelvic morphology even in the growing adolescent group. Previous studies have documented the pre and post operative correlation between pelvic geometry and spinal alignment in normal and surgical subjects. This study investigates whether surgery affects pelvic morphology during its developmental stages. This to our knowledge has not been described previously.
