INTRODUCTION: Adjacent segment degeneration (ASD) has been considered a potential long‐term complication of spinal arthrodesis. However, few studies have analyzed the impact of unilateral or bilateral instrumented lumbar fusion on ASD.
METHODS: Sixty patients who underwent L4/5 posterior lumbar interbody fusion (PLIF) for L4 degenerative spondylolisthesis without severe ASD and have more than 5 years of follow‐up were subjects of this study. Pedicle screw fixation was performed bilaterally for the first 30 patients (Group‐B) and unilaterally for the second 30 patients (Group‐U). Two groups were comparable with regard to age and sex. UCLA grading scale was used to evaluate the ASD on radiograph preoperatively, postoperatively, and at the final follow‐up.
RESULTS: Pain on VAS and walking distance improved significantly (P < 0.001) at 5 years follow‐up. There was no significant difference between the 2 groups. Patients' satisfaction was as high as 80% in Group‐B and 93% in Group‐U responded that they would undergo the same procedure again. Radiographically, bony fusion was obtained in 29 patients (97%) in Group‐B and 25 patients (83%) in Group‐U. In Group‐U, 3 patients showed slight screw‐loosening at the follow‐up without any symptoms. ASD occurred in 50% (15/30 cases) in Group‐B, whereas in 17% (5/30 cases) in Group‐U. Among them, 8 cases (27%) in Group‐B and 1 case (3%) in Group‐U had progressed more than 2 levels of degenerative grade. Although two patients in Group‐B underwent revision surgery for ASD, no patient needed any additional surgery in Group‐U. The severer the change of the degenerative grade was, the worse the patient satisfaction was (P < 0.05).
DISCUSSION: The clinical results of PLIF with unilateral instrumentation were comparable to bilateral instrumentation. Bilateral instrumentation was superior in terms of fusion rate, but inferior in terms of patients' satisfaction because of the development of ASD.