We read with great interest the recent article by Samartzis et al on the association of lumbar intervertebral disc degeneration on magnetic resonance imaging (MRI) with body mass index (BMI) in overweight and obese adults. The authors obtained lumbar spine MRIs performed on 2,599 southern Chinese volunteers. The results of the study showed a significant association between the presence, extent, and global severity of disc degeneration and weight in overweight and obese adults (Samartzis D, Karppinen J, Chan D, Luk KD, Cheung KM. The association of lumbar intervertebral disc degeneration on magnetic resonance imaging with body mass index in overweight and obese adults: a population-based study. Arthritis Rheum 2012;64:1488–96).
Low back pain with or without radicular pain due to sciatica is a major cause of morbidity and is associated with considerable financial costs. Currently, we are conducting a pilot prospective study of the association of BMI and lumbar disc degeneration with clinical outcome in patients who undergo surgery for lumbar disc herniation. As previously described by Pfirrmann and colleagues, we graded the degree of disc degeneration on T2-weighted sagittal MR images using a 5-point scale (Pfirrmann CW, Metzdorf A, Zanetti M, Hodler J, Boos N. Magnetic resonance classification of lumbar intervertebral disc degeneration. Spine 2001;26:1873–8). Preoperative pain and postoperative pain were assessed using a visual analog scale (VAS). After evaluating 64 patients, we found a significant positive correlation of both BMI and age with disc degeneration grade (P = 0.012 and P = 0.035, respectively). Sex, exercise, and smoking habits were not correlated with grade of disc degeneration.
A significant correlation between BMI and the VAS score at 3 months after surgery (P = 0.03) was demonstrated, suggesting that obese patients had a poorer outcome. Consequently, weight loss counseling is of major importance, and patients with lumbar disc herniation should receive preoperative and postoperative counseling. Although our study included only a small number of patients, we concur with Samartzis et al that there is an association between the severity of disc degeneration and BMI. Further studies are needed to clarify the relationship between BMI and treatment outcomes in patients with lumbar disc herniation and to explore a possible relationship between BMI and risk of recurrent disc herniation.