The positive effect of posterolateral lumbar spinal fusion is preserved at long-term follow-up: a RCT with 11-13 year follow-up

Abstract

Introduction: Few studies have investigated the long-term effect of posterolateral lumbar spinal fusion on functional outcome.

Aim: To investigate the long-term result after posterolateral lumbar spinal fusion with and without pedicle screw instrumentation.

Methods: Questionnaire survey of 129 patients originally randomised to posterolateral lumbar spinal fusion with or without pedicle screw instrumentation. Follow-up included Dallas Pain Questionnaire (DPQ), Oswestry Disability Index (ODI), SF-36 and a question regarding willingness to undergo the procedure again knowing the result as global outcome parameter.

Results: Follow-up was 83% of the original study population (107 patients). Average follow-up time was 12 years (range 11-13 years). DPQ-scores were significantly lower than preoperatively in both groups (P < 0.005) and no drift towards the preoperative level was seen. No difference between the two groups were observed (instrumented vs. non-instrumented): DPQ Daily Activity mean 37.0 versus 32.0, ODI mean 33.4 versus 30.6, SF-36 PCS mean 38.8 versus 39.8, SF-36 MCS mean 49.0 versus 53.3. About 71% in both groups were answered positively to the global outcome question. Patients who had retired due to low back pain had poorer outcome than patients retired for other reasons, best outcome was seen in patients still at work (P = 0.01 or less in all questionnaires, except SF-36 MCS P = 0.08).

Discussion: Improvement in functional outcome is preserved for 10 or more years after posterolateral lumbar spinal fusion. No difference between instrumented fusion and non-instrumented fusion was observed. Patients who have to retired due to low back pain have the smallest improvement.

Fig. 1

DPQ scores preoperatively and at each follow-up in the two treatment groups. Values are mean and standard error of mean. All 12-year follow-up scores are significantly improved from preoperatively

Fig. 2

Different outcome scores for the two treatment groups. Values are mean and standard error. No significant difference between the two groups (Mann–Whitney rank-sum test) (Although MCS P = 0.0528)

Fig. 3

Scores of the eight SF36 subscales according to treatment group. Values are mean and standard error. No significant difference between the two groups in any of the scales. Data on Danish norm material is adapted from Bjørner et al. [1]

Fig. 4

Score of the different outcome measures according to employment status. P-values are Kruskal–Wallis test (with ties) that the groups are equal

Fig. 5

Scores of the eight SF36 subscales according to employment status. Values are mean and standard error. P-values are Kruskal–Wallis test (with ties) for difference between the groups