Therapeutic failure of the lumbar medial branch block and its relation to obesity. Retrospective cohort study

Abstract

Objective: To compare the frequency of therapeutic failure of bilateral lumbar facet block in patients with chronic axial low back pain, obese with non-obese, in a chronic pain care center in western Colombia for one year. Materials and methods: An observational analytical follow-up study of a retrospective cohort was performed. electronic medical records of patients were reviewed, the patients were over 18 years old, of both sexes, bilateral lumbar facet block was performed due to chronic axial low back pain, they had a record of body mass index, and post-procedure control between the 1st of January and December 31, 2018. Pain score values were recorded by the Visual Analog Scale (VAS) before and after the procedure. Therapeutic failure was considered when the improvement in pain was less than 50 % of the initial VAS value (4), and an analysis was applied for other modifying variables reported in the literature. Results: 190 patients were included, with an average age of 56.8 years (± 13.5), 49.5 % female, 66.3 % were employees, 17.4 % housewives, 8,9 % independent, and 7,4 % pensioners. 29 % showed a normal BMI, 42.6 % overweight, and 28.4 % obesity. The most frequent monotherapy was acetaminophen in 12.1 %, a third of the patients had received physical therapy. 23.7 % had a history of previous interventionism and most of these had had a positive response. The percentage of therapeutic failure was 54.7 % (104 patients); and the variables that showed statistical association with this were: age (p = 0.014), the previous response to interventionism (p = 0.014), and time of evolution of pain (p = 0.045). The percentage of obesity among those who presented therapeutic failure was 76.9 %, while in those who did not present it, it was 64 % (p = 0.05). In the multivariate analysis, the variables that showed statistical significance against therapeutic failure were: age younger than 50 years OR 2.7, CI [1.37 - 5.34] p = 0.004; and overweight OR 2.36, IC [1.11 - 5.04], p = 0.026. Conclusion: In this study, evidence that being overweight is associated with therapeutic failure in lumbar facet block was found, although the same did not happen with obesity.