Earlier and More Extensive Thoracic Fusion is Associated with Diminished Pulmonary Function. Outcome after Spinal Fusion of 4 or More Thoracic Spinal Segments Before Age 5

• a - Synthes, Inc

Purpose: Investigate the effect of early thoracic fusion on pulmonary function, chest dimensions and height in subjects undergoing early thoracic spinal arthrodesis.

Methods: IRB approved cohort study of patients at a single pediatric institution. Patients with fusion of 4 or more thoracic spinal levels performed before age 5, with at least 5 years of follow-up were identified and called back for evaluation. Excluded were those with pre-existing chest wall defects or major anomalies, neuromuscular or pulmonary disease or follow-up less than 5 years. One patient who met criteria had died of pulmonary insufficiency at age 22. Thirteen patients meeting these criteria returned for follow-up evaluation including radiographic, CT and pulmonary function assessment and quality of life questionnaire. Mean age at fusion was 2.6 years, with 6.9 vertebral (mean) segments fused. Mean follow-up was 10.8 years.

Results: The mean FVC observed/predicted was 62% (34-95%), and the mean FEV1 observed/predicted was 62% (32-94%). Pulmonary function values as a percentage of predicted values were more diminished in those patients undergoing earlier fusion and those with arthrodesis of more vertebrae. Percent predicted FVC and FEV1 were more severely diminished with fusion at an earlier age (P=0.046, P=0.087) and a greater number of vertebrae fused (P=0.020, P=0.019), as was overall height expressed as standard deviations below normal height for age and gender (P=0.023). FEV1 was more severely affected when the center of the fusion was closer to T6 (P=0.030). Further operative intervention occurred in 3 patients. Quality of life questions revealed seven patients with persistent pain, and three patients with major complaints about functional and cosmetic limitations.

Significance: Early arthrodesis of thoracic spinal segments for progressive deformity in the very young is associated with significant reductions in pulmonary function at follow-up. Separating the effect on outcome of early fusion vs. that of the underlying condition in this uncommon and heterogeneous patient population is difficult and further complicates the evaluation of treatment alternatives. The limitations of this study include the small number of patients, many of whom did not reach maturity, and the lack of a control group (without fusion). Multicenter studies with follow-up to maturity are warranted.

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