[Risk Factors for Predicting the Need for Additional Surgery for Symptomatic Adjacent Segment Disease after Minimally...

To determine the incidence of and risk factors for symptomatic adjacent segment disease(SASD)requiring additional surgery in patients previously treated with minimally invasive surgery-transforaminal lumbar interbody fusion(MIS-TLIF)for degenerative lumbar disease.

A series of 467 consecutive patients who had undergone MIS-TLIF of one or two segments to treat degenerative lumbar disease was identified. The mean age of the patients at the time of the index operation was 67.7 years and the mean follow-up period was 33.2 months(range, 6.0-110.1 months). The incidence rate of SASD surgeries was calculated using the Kaplan-Meier method. The log-rank test and Cox regression analysis were used for risk factor analysis based on age, sex, number of fused segments, presence of laminectomy adjacent to index fusion, and L1 plumb line.

The overall incidence rate of SASD requiring additional surgery was 2.8%. Kaplan-Meier analysis predicted a disease-free rate of adjacent segments in 94.3% of the patients at 4 years and in 90.8% of the patients at 8 years after the index operation. In the analysis of risk factors, a negative L1 plumb line was associated with a 5.6 times higher incidence of SASD requiring additional surgery than that associated with a positive L1 plumb line(p=0.0096). There was no significant difference in the survival rates based on age, sex, number of fused segments, and concomitant laminectomy to adjacent segment.

Approximately 9.2% of the patients were predicted to undergo additional surgery for treating SASD within 8 years of MIS-TLIF. In this study, presence of a negative L1 plumb line indicated higher incidence of additional SASD associated surgeries than that shown by a positive L1 plumb line. Therefore, surgeons should carefully consider this factor while performing MIS-TLIF.