Determinants of outcome in lumbar spinal stenosis surgery

Abstract: Lumbar spinal stenosis (LSS) is a degenerative disorder of the spine that predominantly affects the elderly. LSS is the most common spinal disorder leading to surgery in Sweden. Recent randomized controlled studies have showed better outcome with surgery compared to conservative treatment. However, after surgery, health related quality of life (HRQoL) and function continue to be inferior to that of the background population. Many patients experience residual leg or back pain and 60-70% of patients are satisfied with the outcome. Knowledge on what characterizes the different subtypes of spinal stenosis and to which extent the stenosis type influences pain, function and HRQoL is lacking. Little is also known about the relationship between degree of stenosis and outcome. In earlier studies, patients with predominant back pain (back pain ≥ leg pain) reported inferior outcomes, but the role of spinal fusion in patients with predominant back or leg pain has not been investigated. For this thesis two clinical databases were used. A Department of Orthopedics in Lund database which included radiological data (MRI) and patient related outcome measures for 140 patients and the Swedish Spine Register which contains data on more than 15,000 patients operated for three different forms of LSS; lateral recess stenosis (LRS), central spinal stenosis (CSS) and LSS with degenerative spondylolisthesis (DS). In Study I, we showed spinal measurements, including central dural sac area, multilevel stenosis, and DS to have a limited correlation to pain, function and HRQoL. In Study II, we showed preoperative duration of symptoms exceeding two years and poor preoperative function to predict poor outcome of surgery. Back pain was often experienced by patients scheduled for spinal stenosis surgery and HRQoL and function was low irrespective of whether back or leg pain was predominant in LRS, CSS and DS (Study III). In Study IV, predominant back pain (PB) was associated with inferior outcome of surgery for CSS. In Study IV, patients with PB operated with fusion had a marginally better outcome than patients decompressed only. However, this advantage diminished when we adjusted for confounders. At the two year follow-up no significant benefit for fusion was observed. In Study V, DS patients with fusion and PB benefited from fusion compared with patients with decompression only as the fused patients improved more in terms of leg and back pain as well as function at the one year follow-up. Patients with predominant leg pain appeared to have better outcome in terms of back pain with fusion but significant baseline differences in back pain between the treatment groups precluded firm conclusions regarding this benefit. In conclusion, decompression supplemented with fusion may lead to improved outcome in highly selected patients with CSS and predominant back pain. Further studies are needed to identify this subgroup. Adding fusion leads to superior one year outcome in DS patients with predominant back pain. Degree of dural sac stenosis has limited impact on symptoms and outcome but early surgery for LSS should be considered, before severe functional deterioration occurs.