The effect of obesity on surgery depends on the spinal condition


A study published ahead of print in Spine shows that obesity does not affect surgical outcome in patients with lumbar stenosis but is associated with poorer outcome after surgery in patients with degenerative spondylolisthesis.

Jeffrey Rihn, Rothman Institute, Department of Orthopedic Surgery, Thomas Jefferson University, Philadelphia, USA, and others reported that a “clear link” between obesity and increased complication rates after surgery has been established and there remains “much controversy as to whether obesity influences the outcome of surgical treatment of spinal disease.” In their study, using data from SPORT (Spinal Patients Outcome Research Trial), they hypothesized: “Obesity will be associated with a worse outcome after treatment of lumbar spinal stenosis and degenerative spondylothisthesis.”

However, after four years of follow-up, they did not find any significant differences in three primary outcome measures (bodily pain, physical function domains of the SF-36, and the Oswestry Disability Index) between obese (≥30 Body Mass Index) surgically treated, spinal stenosis, patients (261) and surgical treated spinal stenosis patients (373) who were not obese. Additionally, there were no differences in operation time, blood loss, length of hospital stay, rate of complications, and need for additional surgeries between the two patient groups.

Differences were observed, however, between obese surgically treated, degenerative spondylothisthesis, patients (225) and non-obese surgically treated, degenerative spondylothisthesis, patients (376). Rihn et al wrote: “The change in primary outcome measures in the surgically treated degenerative spondylothisthesis patients demonstrated that obese patients had significantly less improvement from baseline compared to the non-obese patients in regards to the SF36 physical function scores (22.1 vs. 27.9, four-year follow-up; p=0.022).” Obesity was also associated with a significantly longer operating time (mean 220.2 minutes vs. 197.2 minutes; p=0.008) and a trend towards an increased rate of wound infection (5% vs. 1%; p=0.051) compared with non-obesity. Rihn et al observed that, surprisingly, obese patients had a lower rate of intraoperative complications, particularly the incidence of dural tear (5% vs. 14%; p=0.007).

The investigators also reviewed the effect of non-surgical management in obese patients. They found that non-surgical management was not effective for either spinal stenosis or degenerative spondylothisthesis. For both spinal conditions, the treatment effect for the SF36 physical function score was significantly greater in obese patients (compared with non-obese patients), which the investigators said was “largely” due to the relatively poor outcome observed in non-surgically treated obese patients. Rihn et al said that the explanation for the poor outcome was not “readily apparent.” They added: “It is possible that current non-operative interventions are not as effective in obese patients and that alternative non-operative treatments should be developed and investigated for this patient population.”

Rihn told Spinal News International: “It is evident from the study that surgical treatment of lumbar stenosis and degenerative spondylolisthesis in obese patients can still offer significant benefit over non-operative treatment options in relieving pain and restoring function. Obese patients with degenerative spondylolisthesis may not do as well with surgery than non-obese patients and may have an increased risk of wound infection. Nonetheless, surgery still provides a significant advantage over the non-surgical treatment options. Current non-operative treatment strategies used in this study were not very effective in the obese patients.”