In their article reporting outcomes for posterior lumbar interbody fusion (PLIF) in obese patients, Singh and colleagues suggest that reasonable outcomes can be obtained, even in those with body mass indices (BMI) above 30. Their series included 15 obese patients, 3 of whom were morbidly obese (BMI > 35), who were treated with PLIF primarily for low back pain in the setting of degenerative disk disease. They reported an improvement in the Oswestry Disability Index (ODI) of about 15 points, with a superficial infection rate of 20% and a deep infection rate of 7% (1 patient). In terms of technical complications, there was 1 durotomy, 1 malpositioned pedicle screw requiring a return to the OR for removal, and 1 instance of a cage breaking during insertion. The ODI change score was actually slightly better than that reported by Fritzell et al. (11 point improvement) in a series of low back pain patients treated for fusion who were not selected by weight.1 In contrast, the improvement was far less than that seen for the average disk herniation patient in SPORT (ODI improvement of 38 points with surgery).2 Given that one would expect relatively poor outcomes in obese patients undergoing fusion for low back pain, these outcomes seem acceptable.
The challenge in interpreting these data is that the lack of two essential control groups—non-obese patients undergoing fusion and obese patients treated non-operatively. Without these groups available for comparison, it is impossible to know if obesity affected outcomes or complication rates or the degree to which obese patients benefited from surgery compared to non-operative treatment (i.e. the treatment effect of surgery). These are really the essential questions that need to be answered in order to counsel obese patients with low back pain about their treatment options. While SPORT did not study patients with degenerative disk disease and low back pain, it did include obese and non-obese patients treated with surgery and non-operative treatment. Subgroup analysis of the disk herniation cohort revealed that while obese patients did worse with both surgery and non-operative treatment compared to non-obese patients, they had a similar treatment effect as non-obese patients (i.e. their benefit from surgery relative to non-operative treatment was similar).3 If the same held true for obese patients with low back pain, then surgery would be a reasonable treatment option. However, this answer will not be known until a trial comparing surgery to non-operative treatment for degenerative disk disease including a subgroup analysis of obese patients is performed.
How does obesity affect your surgical decision making? Will this article make you more likely to offer surgery to obese patients? Post a comment and let us know.
Adam Pearson, MD, MS
1. Fritzell P, Hagg O, Wessberg P, Nordwall A. 2001 Volvo Award Winner in Clinical Studies: Lumbar fusion versus nonsurgical treatment for chronic low back pain: a multicenter randomized controlled trial from the Swedish Lumbar Spine Study Group. Spine (Phila Pa 1976) 2001;26:2521-32; discussion 32-4.
2. Weinstein JN, Lurie JD, Tosteson TD, et al. Surgical versus nonoperative treatment for lumbar disc herniation: four-year results for the Spine Patient Outcomes Research Trial (SPORT). Spine 2008;33:2789-800.
3. Pearson AM, Lurie JN, Tosteson TD, et al. SPORT intervertebral disc herniation: indications matter most. In: ISSLS Annual Meeting; 2010; Aukland, NZ; 2010.