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Study design: A prospective cohort study.

Objective: The aim was to investigate changes in lumbar lordosis (LL) and its association to changes in patient reported outcome measures (PROMs) after decompressive surgery for lumbar spinal stenosis (LSS).

Summary of background: Few studies have addressed change in LL after decompression surgery for LSS in relation to outcomes.

Method: Pre- and postoperative data from 310 patients having standing x-ray both before and 2 years after surgery were included. The patients were grouped based on the change in LL preoperatively to 2 years after surgery; group 1: <5 degrees (n=196), group 2: ≥5 <10 degrees (n=55) or group 3: ≥10 degrees (n=59) of change in LL. The changes in function, disability and pain were assessed by the Oswestry Disability Index (ODI), Numeric Rating Scale (NRS), and the Zurich claudication questionnaire (ZCQ). The three groups were compared regarding baseline variables using the ANOVA test for continuous variables and the chi-square test for categorical variables. The groups were further compared with a likelihood ratio test in relation to changes in PROMs 2 year after surgery and outcomes were adjusted for respective baseline PROMs, age, sex, smoking, BMI, Schizas and Pfirrmann scores.

Results: LL was significantly changed at group level 2 years after surgery with a mean difference of 2.2 (SD 9.4) degrees (P=0.001). The three LL change groups did not show any significant differences in patient characteristics, function, disability, and pain at baseline. The two groups with a change of more than 5 degrees in LL 2 year after surgery (group 2 and 3) had significantly greater improvements in ODI (P=0.022) and ZCQ function (P=0.016) in the adjusted analyses, but was not significant for back and leg pain

Conclusion: Changed LL after decompressive surgery for LSS was associated with improved ODI and physical function.