Study design:

Cost-effectiveness analysis.

Objective:

To determine if bariatric surgery prior to posterior lumbar decompression and fusion (PLDF) for degenerative spondylolisthesis (DS) is a cost-effective strategy.

Summary of background data:

Obesity poses significant perioperative challenges for DS. Treated operatively, obese patients achieve worse outcomes relative to non-obese peers. Concomitantly, they fare better with surgery than with nonoperative measures. These competing facts create uncertainty in determining optimal treatment algorithms for obese patients with DS. The role of bariatric surgery merits investigation as a potentially cost-effective optimization strategy prior to PLDF.

Methods:

We simulate a Markov model with two cohorts of obese individuals with DS. 10,000 patients with BMI ≥ 30 in both arms were candidates for both bariatric surgery and PLDF. Subjects were assigned either to 1) no weight loss intervention with immediate operative or non-operative management (“Traditional arm”) or 2) bariatric surgery two years prior to entering the same management options (“combined protocol”).Published costs, utilities, and transition probabilities from the literature were applied. A willingness to pay threshold of $100,000/QALY was used. Sensitivity analyses were run for all variables to assess the robustness of the model.

Results:

Over a ten-year horizon, the combined protocol was dominant ($13,500 cheaper, 1.15 QALY more effective). Changes in utilities of operative and non-operative treatments in non-obese patients, the obesity cost-multiplier, cost of bariatric surgery and the probability of success of non-operative treatment in obese patients led to decision changes. However, all thresholds occurred outside published bounds for these variables.

Conclusions:

The combined protocol was less costly and more effective than the traditional protocol. Results were robust with thresholds occurring outside published ranges. Bariatric surgery is a viable, cost-effective preoperative strategy in obese patients considering elective PLDF for DS.Level of Evidence: 3.