SPORT Subgroup Analysis Shows Discectomy Outcomes Vary by Herniation Level
BY LAUREN UZDIENSKI, SEPTEMBER 2, 2008
A new study published in JBJS evaluated results from one arm of the SPORT trial to see if herniation level affected discectomy outcomes. The authors undertook the study after a recent randomized trial conducted by Dr. Heikki Osterman et al showed no benefit for patients receiving discectomy at L5-S1, conflicting with SPORT's overall determination that there was a slight benefit for patients receiving discectomy over nonoperative care.
The SPORT study was comprised of 646 L5-S1 herniations, 456 L4-L5 herniations, and 88 upper lumbar (L2-L3 or L3-L4) herniations, with outcomes assessed by pain and function and a modified Oswestry Disability Index at six weeks, three months, six months, one year and two years.
Results showed that upper level patients showed a greater benefit with discectomy than L4-L5 patients, who in turn showed better outcomes than the L5-S1 patients. Though the upper-level group was too small to pack any strong statistical punch, there was a 10-15 point difference on pain and function and ODI scores between the upper level group and the L5-S1 group. The authors did identify a benefit for the L5-S1 patients, countering the result from the Osterman study, which the authors attributed to SPORT's larger sample size. Despite the range of outcomes, this subgroup analysis did not undermine SPORT's determination that better results were associated with surgery.
The authors suggest that the varied treatment effects could be due to, among other reasons, smaller spinal canal area at upper levels, which can intensify herniation symptoms and the position of the herniation (i.e., whether it was foraminal, posterolateral or central). Though the authors controlled for this, herniations in the upper-level group were more likely to occur in the far lateral and foraminal positions than herniations at the lower two levels, which could have contributed to the difference in outcomes.
