1 Department of Public Health - Department of Epidemiology, Department of Public Health, Health, Aarhus University2 Department of Clinical Medicine - The Department of Orthopaedics E, ?AS, Department of Clinical Medicine, Health, Aarhus University3 School of Economics and Management, Faculty of Social Sciences, Aarhus University, Aarhus University4 The Department of Orthopaedics E, ?AS, Faculty of Health Sciences, Aarhus University, Aarhus University5 unknown6 Institute of Clinical Medicine, Faculty of Health Sciences, Aarhus University, Aarhus University7 Department of Public Health - Department of Epidemiology, Department of Public Health, Health, Aarhus University8 Department of Clinical Medicine - The Department of Orthopaedics E, ?AS, Department of Clinical Medicine, Health, Aarhus University
How to More Effectively Determine the Onset of Distal Adding on
STUDY DESIGN: A radiographical follow-up and analysis. OBJECTIVE: To identify appropriate radiographical parameters for measuring the extent of distal adding-on and to discuss criteria for determining the onset of distal adding-on. SUMMARY OF BACKGROUND DATA: There is no consensus on how to determine the onset of distal adding-on in Lenke 1A scoliosis. Such questions as: "Which radiographical parameters should be used for measuring the extent of distal adding-on?" and "What criteria should be applied in determining the onset of distal adding-on?" need to be answered. METHODS: We reviewed all the AIS cases surgically treated in an institution from 2003 through 2009. Inclusion criteria were as follows: (1) patients with Lenke 1A curves who were treated with selective thoracic fusion; (2) age less than 30 years; (3) 2-year radiographical follow-up. Eight radiographical parameters were tested to see if they are potential instruments in the detection of distal adding-on. RESULTS: Fifty-three patients met the inclusion criteria. No pseudarthrosis or crankshaft phenomenon was observed in the current cohort. Five out of 8 radiographical parameters: thoracic Cobb, LIV-CSVL distance, LIV + 1-CSVL distance, thoracic AV-CSVL distance and LIV + 1 tilt angle, in the 2 years after surgery, showed significant increase. The remaining 3 parameters: LIV tilt angle, T1-CSVL distance and number of vertebrae within Cobb, however, did not show significant increase. In regard to the 5 parameters that have the potential to detect the onset of distal adding-on, we found a high correlation between every 2 of them. The correlation coefficients range from 0.504 to 0.962 (P = 0.001), suggesting that all of them are in a positive linear relationship. Regarding the criterion for determining the onset of distal adding-on, an increase of more than 10 mm in LIV-CSVL distance in the postoperative period can be considered as a the main criterion because it is unlikely to be induced by measurement errors. CONCLUSION: LIV-CSVL distance could be an ideal parameter for measuring the extent of distal adding-on. Distal adding-on can be determined when the LIV-CSVL distance increases by 10 mm in the postoperative period.