RÉSUMÉ
Objective:To evaluate the outcomes of transforaminal lumbar interbody fusion (TLIF) for patients with lumbar spinal stenosis (LSS) and diffuse idiopathic skeletal hyperostosis (DISH).Methods:This study recruited 33 patients (15 male and 18 female) with LSS and DISH who underwent TLIF surgery from January 2010 to July 2018. The mean age was 65.1±11.2 years old and the instrumented segments averaged 1.45±0.42 levels. Another group of LSS patients without DISH were well matched to the DISH group at a 1∶1 ratio in terms of age, sex, and instrumented levels. Lumbar lordosis, local lordosis as well as lowerlumbarlordosis were measured on X-ray taken before and after surgery. According to Pfirrmann's classification, the degree of preoperative disc degeneration was evaluated on preoperative MRI, and the incidence of postoperative fusion cage subsidence was recorded during follow-up. Oswestry disability index (ODI) was used to evaluate the lumbar function and visual analogue scale(VAS) scores for low back pain and leg pain were used to evaluate the quality of life.Results:There were no significant difference between two groups in terms of age, bone mineral density, operative time, postoperative bleeding volume, fusion levels and postoperative follow-up time. Compared with the non-DISH group (3.20±0.95), the DISH group had higher degeneration disc according to Pfirrmann's classification (3.82±0.64) ( t=3.109, P=0.002), lower lumbar lordosis(37.4°±8.5° vs. 45.2°±12.2°, t=3.013, P=0.003), and lower lower lumbar lordosis (18.3°±3.9° vs. 21.9°±5.4°, t=3.104, P=0.002). After TLIF surgery, lumbar lordosis was significantly improved in both groups. During follow-up, notable correction loss was noted in DISH group in terms of lumbar lordosis (43.6°±9.7° vs. 50.1°±10.2°, t=2.652, P=0.010), lower lumbar lordosis (19.1°±4.7° vs. 22.9°±5.2°, t=2.540, P=0.013) as well as local lumbar lordosis (17.4°±6.5° vs. 22.7°±7.2°, t=3.138, P=0.002). Moreover, these above value in the DISH group were significantly lower than those in the non-DISH group. At the latest follow-up, 12 patients in the DISH group were identified with cage subsidence, which were significantly higher than in the non-DISH group (36.3% vs. 12.1%, χ2=5.280, P=0.022). Till the latest follow-up, both groups had considerable improvement of the ODI score, back pain and leg pain VAS score. However, the back pain VAS scores in the DISH group were significantly higher than that in the non-DISH group ( t=2.862, P=0.005). Conclusion:Compared with LSS patients without DISH, LSS patients with DISH are more likely to have cage subsidence and loss of correction of lumbar lordosis angle after TLIF surgery. Moreover, the VAS score of low back pain in LSS patients with DISH was lower than those without DISH.