Cost-effectiveness of adult spinal deformity surgery in a military healthcare system

OBJECTIVE Adult spinal deformity surgery is an effective way of treating pain and disability, but little research has been done to evaluate the costs associated with changes in health outcome measures. This study determined the change in quality-adjusted life years (QALYs) and the cost per QALY in patients undergoing spinal deformity surgery in the unique environment of a military healthcare system (MHS). METHODS Patients were enrolled between 2011 and 2017. Patients were eligible to participate if they were undergoing a thoracolumbar spinal fusion spanning more than 6 levels to treat an underlying deformity. Patients completed the 36-Item Short Form Health Survey (SF-36) prior to surgery and 6 and 12 months after surgery. The authors used paired t-tests to compare SF-36 Physical Component Summary (PCS) scores between baseline and postsurgery. To estimate the cost per QALY of complex spine surgery in this population, the authors extended the change in health-related quality of life (HRQOL) between baseline and follow-up over 5 years. Data on the cost of surgery were obtained from the MHS and include all facility and physician costs. RESULTS HRQOL and surgical data were available for 49 of 91 eligible patients. Thirty-one patients met additional criteria allowing for cost-effectiveness analysis. Over 12 months, patients demonstrated significant improvement (p < 0.01) in SF-36 PCS scores. A majority of patients met the minimum clinically important difference (MCID; 83.7%) and substantive clinical benefit threshold (SCBT; 83.7%). The average change in QALY was an increase of 0.08. Extended across 5 years, including the 3.5% discounting per year, study participants increased their QALYs by 0.39, resulting in an average cost per QALY of $181,649.20. Nineteen percent of patients met the < $100,000/QALY threshold with half of the patients meeting the < $100,000/QALY mark by 10 years. A sensitivity analysis showed that patients who scored below 60 on their preoperative SF-36 PCS had an average increase in QALYs of 0.10 per year or 0.47 over 5 years. CONCLUSIONS With a 5-year extended analysis, patients who receive spinal deformity surgery in the MHS increased their QALYs by 0.39, with 19% of patients meeting the $100,000/QALY threshold. The majority of patients met the threshold for MCID and SCBT at 1 year postoperatively. Consideration of preoperative functional status (SF-36 PCS score < 60) may be an important factor in determining which patients benefit the most from spinal deformity surgery.