Objective:

The objective of this study was to investigate the incidence and risk factors of rod fractures (RF) after a single-level lumbar pedicle subtraction osteotomy (PSO) using a side-tightening (ST) pedicle screw system.

Methods:

Fifty-seven consecutive patients who underwent a single-level lumbar PSO for the degenerative sagittal imbalance at a single institution were retrospectively reviewed. All surgeries were performed by a single surgeon using an ST pedicle screw system. Demographic, surgical, and radiographic data were analyzed to investigate the incidence and risk factors for RF.

Results:

Seven (12.3%) patients showed RF after PSO. Four patients had bilateral RFs and three patients had unilateral RFs. The location of the RF was at the PSO level in 6 of 7 patients. The ratio of adjacent interbody fusion was significantly different between the group with RF and the group without RF (16.7% versus 74.0%, P=0.004). The preoperative segmental angle at the PSO vertebra (-6.1° ± 5.5° versus -1.7° ± 4.6°, P=0.049) and postsurgical change in lumbar lordosis (48.4° ± 8.8° versus 37.8° ± 11.9°, P=0.033) were significantly different between the two groups. Risk factor analysis using stepwise logistic regression analysis revealed that the absence of an adjacent interbody cage (odds ratio [OR] = 0.011, 95% confidence interval [CI] = 0.000-0.390, P = 0.013) was a significant risk factor.

Conclusion:

The incidence of RF after a single-level lumbar PSO using the ST pedicle screw system was 12.3% in our cohort. The absence of an adjacent interbody cage was a significant risk factor for RF.