Introduction. Several studies have reported that diffuse idiopathic skeletal hyperostosis (DISH) is a risk factor for revision surgery following posterior spinal decompression for lumbar spinal stenosis. Therefore, DISH may also affect the surgical outcomes of fusion surgery for lumbar degenerative disease with DISH. The purpose of this study was to assess the mid-term surgical outcomes of posterior lumbar interbody fusion (PLIF) for lumbar spondylolisthesis with DISH.
Methods. We retrospectively reviewed 324 consecutive patients who underwent 1- or 2-level PLIF for lumbar spondylolisthesis at our institution. Patients with failed back syndrome and/or follow-up <2 years were excluded. PLIF was recommended for LSS patients with anterior slippage of >15%, posterior opening of >5° during flexion, and/or lateral slippage of >3mm. DISH was diagnosed using preoperative standing whole-spine radiographs according to the Resnick criteria. Only vertebral segments with complete bridging of the disc space (Mata score grade 3) were defined as contiguous vertebral segments. We investigated demographic data, perioperative factors, preoperative and postoperative (at 2-year and final follow-up) visual analog scale (VAS) and Japanese Orthopaedic Association Back Pain Evaluation Questionnaire (JOABPEQ), and the rates of revision surgery at final follow-up and compared between the DISH (D) group and the non-DISH (N) group.
Results. A total of 129 patients (mean age: 66.0 years, mean follow-up period: 58.4 months) were included for analysis. Of the 129 patients, 33 (25.6%) patients with DISH and 96 patients without DISH were classified as the D group and the N group. Of the 33 patients in the D group, 13 patients (10.1%) had DISH extended to the lumbar segment. There were no statistical differences in age, past history, follow-up period, and number of fused segments between the 2 groups. All postoperative VAS scores at 2-year and final follow-up significantly improved compared with preoperative scores in both of the 2 groups, whereas postoperative VAS scores at 2-year and final follow-up were comparable between the 2 groups. Regarding JOABPEQ, the effective rate of all domains at 2-year follow-up showed no statistical differences between the 2 groups. Meanwhile, the effective rate in the walking ability domain at final follow-up was significantly lower in the D group than in the N group (D: 54.5%, N:78.9%, P = 0.007). The decrease of the effective rate in the walking ability was observed in 15 out of 33 cases with DISH. Among these cases, there were 6 patients with adjacent segment disease, 4 patients with residual lower limbs numbness persisting from the preoperative state, 4 patients with the onset of new cervical myelopathy, and 1 patient with the impact of drop foot due to peroneal nerve paralysis. The revision rate was higher in the D group, but not significant (D: 15.2%, N: 5.2%, P = 0.077).
Discussion. The surgical outcomes of PLIF for lumbar spondylolisthesis with DISH are favorable at 2-year follow-up, although poorer than non-DISH patients at final follow-up, particularly in terms of walking ability. Long-term follow-up is crucial to evaluate the surgical outcomes of fusion surgery for lumbar spondylolisthesis with DISH.