The effect of pre-existing degeneration at adjacent segment on postoperative adjacent segment degeneration and surgical clinical outcomes

English Keywords:Lumbar fusion  Adjacent segment degeneration  Sagittal balance  Central canal stenosis grades

English Abstract:

  【Abstract】 Objectives: To analyze the effect of pre-existing adjacent segment degeneration(ASD) and its treatment on postoperative ASD and surgical clinical outcomes. Methods: Patients with lumbar spinal stenosis who received surgical treatment in Peking University Third Hospital from July 2015 to December 2017 were prospectively included. The inclusion criteria were: the responsible segment in L4-S1, and no unstable factor in adjacent segments of the responsible segment. Lumbar spinal X-ray and MRI before and after surgery were completed to evaluate the segmental degeneration. All patients were divided into three groups according to the preoperative ASD and different surgical treatments. Group A, L3/4 central canal stenosis grade is 0 before operation and the responsible segment L4-S1 simply fused. Group B, L3/4 central canal stenosis grade ≥1 before operation, and the responsible segment L4-S1 simply fused. Group C, L3/4 scentral canal stenosis grade ≥1 before operation, adjacent degenerative segment(L3/4) and responsible segment(L4-S1) fused together. There was at least 1 year follow-up. The followings were recorded: age, gender, BMI, ASA classification, follow-up time, operative data, clinical scores and measurements before operation and in the follow-up including Oswestry disability index(ODI), Japanese Orthopaedic Association Scores(JOA), visual analogue scale(VAS) for low back and leg pain, pelvic incidence(PI), pelvic tilt(PT), sacral slope(SS), and lumbar lordosis(LL). Adjacent segment degeneration was diagnosed according to preoperative and follow-up MRI and X-ray changes. Results: A total of 98 patients were enrolled in group A, 85 patients in group B, 87 patients in group C. Patients in group B and group C were significantly older than those in group A(P<0.05), and the amount of operation time and intraoperative blood loss in group C was significantly than those in group A and group B(P<0.05). There was no significant difference in gender, body mass index(BMI), ASA classification, follow-up time, hospital stays time and incidence of perioperative complications among the three groups. ASD was found in 21(21/98, 21.4%) patients in group A, 53(53/85, 62.4%) patients in group B, and 42(42/87, 48.3%) patients in group C. The incidence of ASD in group B and group C was significantly higher than that in group A(P<0.01), and there was no significant difference between group B and group C(P>0.05). The main pathological type of ASD was spinal stenosis aggravation. No patient in the three groups showed adjacent segment disease. The clinical scores in all three groups were significantly improved at the last follow-up. The ODI improvement rates of group A and group B were significantly higher than that of group C(P<0.05). There was no significant difference in JOA and VAS improvement rate between the three groups. The patients were divided into ASD group and non-ASD group at the last follow-up, and there was no significant difference of spinal-pelvic sagittal parameters between the two groups before operation and at the last follow-up(P>0.05). BMI and preoperative central canal stenosis grades were the influencing factors of adjacent segment degeneration during early follow-up. Conclusions: The incidence of early postoperative ASD in patients with preoperative ASD was significantly higher than that in patients without preoperative ASD. Surgical choice treating the responsible segment and adjacent segment together did not get better clinical outcomes. The sagittal parameters did not influence the ASD, and the sagittal balance was not related to ASD at the last follow-up.