Classification of Chronic Back Muscle Degeneration after Spinal Surgery, and Its Relationship to Low Back Pain

Abstract

Introduction Back muscle injury and degeneration often occurs after posterior lumbar surgery, and back muscle degeneration may be a cause of back pain after surgery. However, the relationship between back muscle degeneration and back pain remains controversial. In the current study, we aimed to classify back muscle degeneration using MRI and investigate its relationship with back pain after surgery. Materials and Methods A total of 84 patients (average age: 65.1 years, 38 men, 46 women) with lumbar spinal stenosis underwent only posterior decompression surgery. MRI (1.5 T) was evaluated before and more than a year after surgery in all patients. Muscle on MRI was classified into three categories: low intensity in T1-weighted image, high in T2-weighted image (type 1), high in both T1- and T2-weighted images (type 2), and low in both T1- and T2-weighted images (type 3). The proportion of types and their relationship with back pain (visual analog scale: VAS) was evaluated. Results MRI revealed muscle degeneration in all patients after surgery (type 1: 6%, type 2: 82%, and type 3: 12%). Type 2 was significantly frequent as compared with types 1 and 3 ( p < 0.01). Low back pain before surgery (average: VAS 7.5) significantly improved after surgery (average: VAS 2.0) ( p < 0.01). Low back pain was not associated with any muscle degeneration MRI types after surgery ( p > 0.05). Conclusion The current study showed the pathology of back muscle degeneration was various after posterior lumbar surgery. Type 2 (fatty change) was most frequent, and some patients were classified into type 3 (scar change), and type 1 (inflammation or water-like change). Modic classification is used for bone marrow change, and type 1 is associated with inflammation and back pain. However, no type of back muscle degeneration was correlated with back pain after surgery. Disclosure of Interest None declared