Introduction: It is likely that the incidence of spinal stenosis will increase with ageing populations. The outcome after surgery in central spinal stenosis has been satisfying in quite many studies. The appropriateness of the indications for surgery has been found to be only around 60% however.

Recently we reported that the degree of cauda equina constriction at the most constricted level in the lumbar spine directly was related to typical preoperative symptoms like walking distance, radiating pain but also quality of life. The aim of this study was to relate the degree of preoperative constriction to the results one year postoperatively.

MATERIAL AND Methods: 35 men and 47 women, mean age 64 years with preoperative imaging of the lumbar spine, completed preoperative questionnaires and operated for central stenosis between June 2002 and May 2004 were followed up one year postop. The self administered pre- and postoperative questionnaires asked for pain intensity in the back or leg(s) (VAS), walking distance before neurogenic claudication, health related quality of life (EQ5D) etc.. In all the subjects the preoperative cross sectional area (CSA) of the most stenotic (constricted) vertebral level was determined from magnified CT or MR examinations and related to the one year postoperative

Results: Results: The average CSA for the most constricted lumbar level was 58.0 SD 23 mm2. For those with a CSA < 68 mm2 parameters like walking ability, pain intensity in the leg and back, health related QoL was improved in a statistically significant way. For those with a preoperative CSA > 68 mm2 no signifcant improvement was found one year postoperatively.

Conclusion: Subjects operated for central spinal stenosis having a pronounced cauda equina constriction (CSA) also had the best outcome one year postoperatively.