title: Reliability of retrospective clinical data to evaluate the effectiveness of lumbar fusion in chronic low back pain.
abstract: METHODS
  Patients in whom a posterior spinal fusion instrumentation had been performed to treat low back pain were asked to recall their preoperative clinical status by retrospectively filling out the same 3 self-evaluation scales they had completed before surgery in a prospective fashion.
  
  
  OBJECTIVE
  To evaluate the impact of recollection error and compare outcomes using retrospective versus prospective methodologies among a cohort of patients treated with posterior spinal fusion instrumentation.
  
  
  BACKGROUND
  Literature on spine surgery from 1990 to 2000 shows a greater increase in retrospective studies as compared to randomized controlled trials and other prospective studies. Cross-sectional studies evaluate therapeutic effectiveness by comparing the current condition with the recalled (retrospectively recorded) pretreatment condition. There are no studies analyzing the characteristics of recalled data in a cohort of patients with chronic low back pain treated with posterior spinal fusion instrumentation.
  
  
  METHODS
  The preoperative clinical status of 58 patients, 33 women and 25 men, with a mean age of 48.3 years (22-84 years) was assessed prospectively with 3 self evaluation questionnaires and retrospectively at a mean of 37.5 months (2-58 months) after surgery using the same questionnaires. The Wilcoxon test was used to compare prospective and retrospective preoperative data and to compare prospective outcomes with outcomes determined from cross-sectional data. Agreement between prospective and retrospective measures was estimated with intraclass correlation coefficients for absolute agreement and consistency.
  
  
  RESULTS
  Comparisons between prospective and recalled data showed significant differences, demonstrating a worse preoperative situation when using retrospective data. Assessment of treatment effectiveness showed that cross-sectional evaluation significantly improved the real surgical outcome. Both absolute agreement and consistency intraclass correlation coefficients showed poor agreement between prospective and cross-sectional data, revealing no systematic bias. Follow-up, age, and gender did not modify agreement and cross-sectional overestimation.
  
  
  CONCLUSIONS
  Relying on a patient's recall of preoperative clinical status is not an accurate method to evaluate surgical outcome after posterior spinal fusion instrumentation. Cross-sectional studies may overestimate the effectiveness of surgery.
authors.affiliation: Unitat de Cirurgia del Raquis, Hospital Vall d'Hebron, Barcelona, Spain. 24361fpu@comb.es
authors.forename: Ferran
authors.initials: F
authors.lastname: Pellisé
authors.forename: Xavier
authors.initials: X
authors.lastname: Vidal
authors.forename: Alejandro
authors.initials: A
authors.lastname: Hernández
authors.forename: Christine
authors.initials: C
authors.lastname: Cedraschi
authors.forename: Joan
authors.initials: J
authors.lastname: Bagó
authors.forename: Carlos
authors.initials: C
authors.lastname: Villanueva
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002908:Chronic Disease; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007405:Intervertebral Disc Displacement / Q000503:physiopathology / Q000601:surgery*; D017116:Low Back Pain / Q000503:physiopathology / Q000601:surgery*; D008159:Lumbar Vertebrae / Q000601:surgery*; D008297:Male; D011939:Mental Recall; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D010147:Pain Measurement; D011446:Prospective Studies; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012655:Self-Evaluation Programs; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods*; D011795:Surveys and Questionnaires