Abstract
Objective
To determine if there is a differing effect between two spinal implant systems on sagittal balance and thoracic kyphosis in adolescent idiopathic scoliosis.
Methods
Retrospective analysis of pre and post-operative radiographs to assess sagittal balance, C7-L1 kyphosis angles and metal implant density.
Group 1 (Top loading system): 11 patients (9 females, 2 males) Single surgeon NB
Group 2 (Side loading system): 17 patients (16 females, 1 male) Single surgeon ED
Total 28 patients
All single right sided thoracic curves
Comparison of pre and postoperative sagittal balance and C7-L1 kyphosis angle for each spinal system. Assessment of implant density (i.e. proportion of pedicle screw relative to number of spinal levels involved in correction).
Results
16 patients demonstrated improved sagittal balance following surgery. There was no significant difference between the pre and post op C7-L1 kyphosis angle in either group (p value 0.06 and 0.83 respectively) although a greater discrepancy was noted in Group 1. In group 1, the mean angle pre op was 33.1 (95% CI 27.3 to 38.9) and post op was 26.2 (95% CI 22.5 to 29.9). In Group 2, the mean angle pre op was 28.9 (95% CI 20.3 to 37.5) and post op was 29.6 (95% CI 22.2 to 37.0). No correlation identified between sagittal balance correction and kyphosis angle. Metal density ranged from 60-100%.
Conclusions
Although the numbers in this series are modest they do suggest that high density metal implants do not lead to a flatback deformity in the sagittal plane. There is no significant difference in the pre and post op kyphosis angles for either implant system used in this study although the results for Group 1 do approach statistical significance. Larger prospective multicentre studies are required to quantify the true significance of these results.
Ethics Approval: Audit/Service Standard in Trust
