The assessment of immediate post-operative scoliosis correction using pedicle screw system by utilising the fulcrum bending technique

Assessment of the curve flexibility is a crucial step in a surgeon's pre-operative planning for scoliosis surgery. Many techniques have been described. These include traction films, supine side bending films, push prone techniques, traction under general anaesthesia as well as fulcrum bending film. In this study, we studied the pre- and immediate post-operative radiographs of twenty eight adolescent idiopathic scoliosis (AIS) patients who were corrected using pedicle screw systems between January 2004 and August 2006. There were twenty two females and six male patients. The mean age of the patients were 17.5 years with a range of 12 to 38 years. Skeletal maturity of the patients was assessed by Risser's score. The majority was Risser 4 (15 cases, 53.6%). Based on King and Moe's classification, the most common curve was type 3 curve (15 cases, 53.6%). Among the twenty eight patients, twenty three patients underwent only posterior correction, while 5 patients underwent additional anterior release surgery. The mean pre-operative Cobb's angle for the posterior surgery group was 65.5 +/- 13.9 degrees and the mean post-operative Cobb's angle was 32.9 +/- 12.6 degrees. There was no difference between the mean correction estimated by fulcrum bending films (Fulcrum Flexibility) and the post- operative Correction Rate figures (44.2% vs. 49.9%). The mean Fulcrum Bending Correction Index (FBCI) in this group of patients is 112.8%. In the group of patients who underwent additional anterior release, their curves were noted to be larger and less flexible with the mean pre-operative Cobb's angle and Fulcrum Flexibility of 90.4 degrees +/- 9.3 degrees and 23.4% respectively. The Fulcrum Bending Correction Index (FBCI) for this group of patients was significantly higher than the posterior surgery group: i.e. 164.0% vs 112.8%. Thus, anterior release does help to improve the correction significantly. The fulcrum bending films give good pre-operative estimation of the amount of correction to be expected post-operatively. The fulcrum bending films can help to identify the curve types which might require anterior release in order to improve the scoliosis correction. Using the Fulcrum Bending Correction Index (FBCI) will also enable surgeons to quantify more accurately the amount of correction achieved by taking into account the inherent flexibility of the spine.