Methods: We observed 141 patients (61 men, 80 women; average age, 65.8 years) who had undergone PLIF and checked for the presence of L5/S interbody fusion. We investigated factors such as age, gender, the presence of diffuse idiopathic skeletal hyperostosis (DISH), fusion level, and grade 2 osteotomy, as well as pre-, post-, and post−preoperative L5/S disk height and angle, lumbar lordosis, Visual Analog Scale (VAS) score, Japanese Orthopaedic Association (JOA) score, and pelvic incidence (PI), comparing those with and without L5/S interbody fusion. In addition, we analyzed the patients classified into short-level (n=111) and multi-level fusion groups (n=30). Results: Overall, the L5/S interbody fusion rate was 70% (short-level, 78%; multi-level, 40%). Age and pre- and post−preoperative L5/S disk angle were significantly different in each fusion level group. DISH presence, grade 2 osteotomy, and postoperative VAS and JOA scores were significantly different in the short-level fusion group, whereas PI was significantly different in the multi-level fusion group. Conclusions Incomplete union after L5/S PLIF correlates with advanced age, many fusion levels, and a large value of preoperative and a small value of post−preoperative L5/S disk angles.

Methods: A total of 400 patients (175 men, 225 women) who underwent PLIF were observed for >1 year. Factors investigated included the frequency of cage retropulsion and surgical revision. In addition, physical (age, sex, disease), surgical (fusion and PLIF levels, cage number, grade 2 osteotomy), and comorbid (DISH, existing vertebral fracture) factors were compared between patients with and without cage retropulsion. Factors related to surgical revision during the observation period were also considered. Results: Cage retropulsion occurred in 15 patients and surgical revision was performed in 11. Revisions included the replacement of pedicle screws (PSs) with larger screws in all patients and supplementary implants in 10. Among the patients with cage retropulsion, the average PLIF level was 2.7, with DISH present in nine patients and existing vertebral fractures in six. Factors affecting cage retropulsion were diagnoses of osteoporotic vertebral fracture, multilevel fusion, single-cage insertion, grade 2 osteotomy, presence of DISH, and existing vertebral fracture. Multivariable analysis indicated that retropulsion of a fusion cage occurred significantly more frequently in patients with DISH and multilevel PLIF. Conclusions DISH and multilevel PLIF were significant risk factors affecting cage retropulsion. Revision surgery for cage retropulsion revealed PS loosening, suggesting that implant replacement was necessary to prevent repeat cage retropulsion after revision.

Methods: In this study, 63 patients (21 men and 42 women) who underwent surgical treatment for OVF were enrolled. Of these patients, 26 had DISH (D+) and 37 did not have DISH (D-). Patient demographic characteristics and surgical, clinical, and radiological findings were compared between those with and without DISH. The change in their ability to perform ADL after surgery was also evaluated. Results: Age, number of comorbidities, and 1-year mortality rate were significantly higher in the D+ group (p<0.05). Postoperative Visual Analog Scale (VAS) scores were significantly higher in patients with impaired (n=6, p=0.04) abilities to perform ADL, and improvements in VAS scores were significantly higher in patients with unchanged abilities to perform ADL (n=54, p=0.03) after surgery. The average postoperative VAS scores were 2.2 for the D+ group and 2.3 for the D- group, which were not significantly different. Conclusions The frequency of OVF with DISH was higher in elderly men with multiple comorbidities and contributed to a higher 1-year mortality rate than those in patients without DISH. However, preoperative and postoperative VAS scores and improvements in VAS scores were similar between those with and without DISH. Postoperative impaired ability to perform ADL was associated with old age, high postoperative VAS scores, and little improvements in VAS scores, which were limitedly influenced by DISH. Surgical treatment of OVF combined with DISH is effective and appropriate for elderly patients.