title: Enduring improvement in Oswestry Disability Index outcomes following lumbar microscopic interlaminar decompression: An appraisal of prospectively collected patient outcomes.
abstract: OBJECTIVE
  Our present study aims to assess the short and long-term postoperative outcome of microscopic interlaminar decompression from a neurosurgical center in a developing country and also aims to further determine any predictors of functional outcome.
  
  
  METHODS
  All patients with moderate to severe symptomatic stenosis undergoing elective posterior lumbar spinal decompression were prospectively enrolled in a database. Preoperative, 2 weeks and 2 years postoperative Oswestry Disability Index (ODI) scores were determined for all patients. These scores were retrospectively compared using repeated measures analysis of variance. Further, linear regression modelling was applied to determine the effect of preoperative ODI, body mass index, age, prior physiotherapy, duration of symptoms, and single or multiple level decompression on the change in ODI at 2 weeks and 2 years follow-up respectively.
  
  
  RESULTS
  A total of 60 consecutive patients (40 males, 20 females) were included for statistical analysis. The percentage of patients with a minimum clinically important difference (MCID), using an ODI threshold value of 10, was 86.7% (n = 52) at the 2 weeks postoperative follow-up. At the 2 years follow-up assessment, 3.3% (n = 2) patients who had earlier not achieved MCID did so, 78.3% (n = 47) of patients were found to have a change in ODI score of <10 or no change, while 18.3% (n = 11) reported a deterioration in their ODI scores. The preoperative ODI score was an independent predictor of change in ODI score at 2 weeks and 2 years respectively (P < 0.0005). The duration of symptoms prior to surgery was found to predict the change in ODI at 2 years follow-up (P = 0.04).
  
  
  CONCLUSIONS
  The evidence regarding the long-term and short-term efficacy of microscopic interlaminar decompression in symptomatic lumbar stenosis is overwhelming. Preoperative ODI scores and duration of symptoms prior to surgery can predict postoperative outcomes.
authors.affiliation: Department of Surgery, Section of Neurosurgery, Aga Khan University Hospital, Karachi, Sindh, Pakistan.
authors.forename: Muhammad Babar
authors.initials: MB
authors.lastname: Khan
authors.affiliation: Department of Surgery, Section of Neurosurgery, Aga Khan University Hospital, Karachi, Sindh, Pakistan.
authors.forename: Muhammad Umair
authors.initials: MU
authors.lastname: Bashir
authors.affiliation: Department of Surgery, Section of Neurosurgery, Aga Khan University Hospital, Karachi, Sindh, Pakistan.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Kumar
authors.affiliation: Department of Surgery, Section of Neurosurgery, Aga Khan University Hospital, Karachi, Sindh, Pakistan.
authors.forename: Syed Ather
authors.initials: SA
authors.lastname: Enam
keywords: Functional outcome; Oswestry Disability Index; interlaminar decompression; lumbar spinal stenosis; microscope; minimally invasive surgery; spinal decompression