Effect of BMI on the clinical outcome following microsurgical decompression in over-the-top technique: bi-centric study with an analysis of 744 patients.

Purpose: Decompression is one of the most common interventions in spinal surgery. Obesity has become an increasing issue in surgical patients. Therefore, the aim of this study was to analyze the clinical outcome following lumbar microsurgical decompression in correlation with the patient's body mass index (BMI).

Materials And Methods: A toal of 744 patients with spinal claudication that were seen at two specialized spine centers were included in this study. All patients underwent a bilateral microsurgical decompression in over-the-top technique. Patients were allocated in 4 groups based in their BMI category: 18.5-24.9 (n = 204), 25.0-29.9 (n = 318), 30.0-34.9 (n = 164) and ≥ 35 (n = 58). Clinical outcome data were recorded at baseline as well as 3, 12 and 24 months thereafter within a prospective study framework. The minimum follow-up was 12 months. For statistical analysis, data were adjusted for age, length of surgery and ASA and were analyzed by generalized linear gamma-based models.

Results: Postoperative changes in all outcome parameters were clearly dependent on BMI. Patients with higher BMI were characterized by inferior baseline values for VAS Back (p < 0.05). Over the follow-up period, the groups with BMI 30-34.9 and BMI ≥ 35 benefitted significantly less from the surgery than the two slimmer groups (p < 0.05).

Conclusion: The data obtained from this large, homogenous cohort demonstrate that the quality of life improved substantially in all patients that were treated microsurgically for spinal stenosis. However, a BMI ≥ 30 may be considered as a negative predictor for a significantly inferior clinical outcome.