Abstract
Introduction
Luk (Luk et al. Spine vol 23(21) 2303-2307 1998) has shown that in posterior surgery, the correction achieved can be predicted by fulcrum bending films. The relevance to anterior correction has been disputed, as this commonly involves shortening the spine by the removal of intervertebral discs. The aim of the study was to see whether the pre-operative bending angle reflected the degree of correction achieved.
Method
91 patients with a structural thoracic curve had an anterior endoscopic correction using a single rod. The mean age was 16.1 years. (range 10-46) The majority of curves were Lenke type 1 (79%) or Type 2 (8%). In all cases disc clearance and bone grafting were performed. All had pre-operative fulcrum bending films.
The mean Cobb angle achieved at the pre-operative bending film was compared with the post-operative correction at 2 months. The FBCI (Fulcrum Bending Correction Index) and correction rates were also calculated. The FBCI is calculated by dividing the correction rate by the fulcrum flexibility and expressed as a percentage. It takes into account the pre-operative flexibility of the curve.
Results
The mean Cobb angle achieved at the pre-operative bending film was 20.4 degrees. The mean Cobb angle of the corrected curve at 2 months following surgery was 20.4 degrees, (p=0.96). The mean FBCI was 107%. The overall correction rate was 60.1%.
Conclusion
In our series fulcrum bending films have been highly predictive of the correction achieved following anterior endoscopic correction. The correction rate of 60.1% is in keeping with other series. In addition, the FBCI was 107%. The instrumentation had corrected to the flexibility achieved at the time of the pre-operative bending films. This implies that the discectomies performed at time of surgery had not significantly increased the correction achieved.
