Patients undergoing surgery for lumbar spinal stenosis experience unique courses of pain and disability: A group-based trajectory analysis

Abstract

ObjectiveIdentify patient subgroups defined by trajectories of pain and disability following surgery for degenerative lumbar spinal stenosis, and investigate the construct validity of the subgroups by evaluating for meaningful differences in clinical outcomes.MethodsWe recruited patients with degenerative lumbar spinal stenosis from 13 surgical spine centers who were deemed to be surgical candidates. Study outcomes (leg and back pain numeric rating scales, modified Oswestry disability index) were measured before surgery, and after 3, 12, and 24 months. Group-based trajectory models were developed to identify trajectory subgroups for leg pain, back pain, and pain-related disability. We examined for differences in the proportion of patients achieving minimum clinically important change in pain and disability (30%) and clinical success (50% reduction in disability or Oswestry score ≤22) 12 months from surgery.ResultsData from 548 patients (mean[SD] age = 66.7[9.1] years; 46% female) were included. The models estimated 3 unique trajectories for leg pain (excellent outcome = 14.4%, good outcome = 49.5%, poor outcome = 36.1%), back pain (excellent outcome = 13.1%, good outcome = 45.0%, poor outcome = 41.9%), and disability (excellent outcome = 30.8%, fair outcome = 40.1%, poor outcome = 29.1%). The construct validity of the trajectory subgroups was confirmed by between-trajectory group differences in the proportion of patients meeting thresholds for minimum clinically important change and clinical success after 12 postoperative months (p < .001).ConclusionSubgroups of patients with degenerative lumbar spinal stenosis can be identified by their trajectories of pain and disability following surgery. Although most patients experienced important reductions in pain and disability, 29% to 42% of patients were classified as members of an outcome trajectory subgroup that experienced little to no benefit from surgery. These findings may inform appropriate expectation setting for patients and clinicians and highlight the need for better methods of treatment selection for patients with degenerative lumbar spinal stenosis.

Preoperative Factors Predict Postoperative Trajectories of Pain and Disability Following Surgery for Degenerative Lumbar Spinal Stenosis

“…We previously reported the results of a univariate group-based trajectory model that demonstrated three distinct leg pain groups, with 36.1% of patients categorized as experiencing a poor outcome (Figure 2 ). 10 Similarly, the multi-trajectory model of overall clinical outcome (leg pain, back pain, and disability) estimated that 30.5% of patients experienced an excellent clinical outcome and 41.9% of patients experienced a good clinical outcome. In total, 27.6% of patients were classified as following pain and disability trajectories indicative of poor overall outcome (Table 3 , Figure 3 ).…”

“…We previously reported the results of our group-based trajectory model that identified three distinct leg pain trajectory groups. 10 …”

“… 27 , 28 We have reported additional information regarding out trajectory modeling approach for the univariate models elsewhere. 10 …”

“… 9 However, recent evidence suggests that many patients do not follow the average course of symptoms, with approximately one in three patients following an unfavorable postoperative pain or disability trajectory. 10 …”

Trajectories of Disability and Low Back Pain Impact

“…We identified two studies that reported trajectories of levels of disability in patients with back pain. 11 , 12 In a sample of elderly patients seeking primary care, 6% showed functional recovery after 12 months’ follow-up, whereas others remained at stable levels of disability. A shorter pain duration, higher confidence in improvement pretreatment, and less comorbidities were associated with improvement in LBP-related disability.…”