Survival rates and risk factors for cephalad and L5-s1 adjacent segment degeneration after L5 floating lumbar fusion : a minimum 2-year follow-up.
OBJECTIVE
Although the L5-S1 has distinct structural features in comparison with other lumbar spine segments, not much is known about adjacent segment degeneration (ASD) at the L5-S1 segment. The aim of study was to compare the incidence and character of ASD of the cephalad and L5-S1 segments after L5 floating lumbar fusion.


METHODS
From 2005 to 2010, 115 patients who underwent L5 floating lumber fusion were investigated. The mean follow-up period was 46.1 months. The incidence of radiological and clinical ASD of the cephalad and the L5-S1 segments was compared using survival analysis. Risk factors affecting ASD were analyzed using a log rank test and the Cox proportional hazard model.


RESULTS
Radiological ASD of the L5-S1 segment had a statistically significant higher survival rate than that of the cephalad segment (p=0.001). However, clinical ASD of the L5-S1 segment was significantly lower survival rates than that of the cephalad segment (p=0.038). Risk factor analysis showed that disc degeneration of the cephalad segment and preoperative spinal stenosis of the L5-S1 segment were risk factors.


CONCLUSIONS
In L5 floating fusion, radiological ASD was more common in the cephalad segment and clinical ASD was more common in the L5-S1 segment. At the L5-S1 segment, the degree of spinal stenosis appears to be the most influential risk factor in ASD incidences, unlike the cephalad segment.
Department of Neurosurgery, Chung-Ang University College of Medicine, Seoul, Korea.
Young-Seok
YS
Lee
Department of Neurosurgery, Chung-Ang University College of Medicine, Seoul, Korea.
Young-Baeg
YB
Kim
Department of Neurosurgery, Chung-Ang University College of Medicine, Seoul, Korea.
Seung-Won
SW
Park
Cephalad segment; Clinical adjacent segment degeneration; L5-S1 segment; Radiological adjacent segment degeneration