ABSTRACT

Objective: Adjacent segment disease (ASD) is a complication commonly associated with spinal instrumentation; it usually requires further surgery and deteriorates the quality of life of patients. Although many studies have been conducted regarding the risk factors of ASD in short-segment surgeries, the literature regarding long-segment posterior instrumentation with pelvic screws and transforaminal lumbar interbody fusion is limited. Therefore, this study evaluated the incidence, cause, and outcome of ASD in such cases.

Materials and Methods: This retrospective study included 127 patients who underwent long-segment posterior instrumentation between January 2010 and December 2017. Among them, 15 developed symptomatic ASD requiring revision surgery. The diagnostic criteria encompassed >20% intervertebral disc height reduction, >5° angulation on flexion-extension X-rays, >3 mm sagittal translation, and facet joint degeneration.

Results: The overall revision rate was 11%. The median follow-up duration was 107 months, with mean of 114±23 months. There were 9 females and 6 males in the ASD cohort, with a mean age of 65.7±5.3 years, compared with a mean age of 62.9±7.6 years for non-ASD patients. The most common level for ASD to occur was T9-10 (p<0.05). Advanced age, degenerative changes, and the absence of vertebroplasty or cemented screws had a significant contribution.

Conclusion: ASD is a significant complication of long-segment posterior instrumentation. The strategy for identifying high-risk patients, particularly by modifiable factors like age >65, smoking, and determination of the upper instrumented vertebra, has important implications for prevention. Prophylactic vertebroplasty and use of cemented screws may reduce ASD risk.