Abstract
BackgroundLumbar floating fusion occasionally causes postoperative adjacent segment disorder (ASD) at lumbosacral level, causing L5 spinal nerve disorder by L5-S1 foraminal stenosis. The disorder is considered to be one of the major outcomes of L5-S1 ASD, which has not been evaluated yet. The present study aimed to evaluate the incidence and risk factors of postoperative L5 spinal nerve disorder after lumbar interbody fusion extending to the L5 vertebra.MethodsWe evaluated 125 patients with a diagnosis of spondylolisthesis who underwent floating fusion surgery with transforaminal lumbar interbody fusion with average postoperative period of 25.2 months. The patients were regarded as symptomatic with postoperative L5 spinal nerve disorder such as radicular pain/numbness in the lower limbs and/or motor dysfunction. We estimated and compared the wedging angle (frontal view) and height (lateral view) of the lumbosacral junction in pre- and postoperative plain X-ray images and the foraminal ratio (ratio of the narrower foraminal diameter to the wider diameter in the craniocaudal direction) in the preoperative magnetic resonance image. Risk factors for the incidence of L5 spinal nerve disorder were explored using multivariate logistic regression.ResultsEight of the 125 patients (6.4 %) were categorized as symptomatic, an average of 13.3 months after surgery. The wedging angle was significantly higher, and the foraminal ratio was significantly decreased in the symptomatic group (both P < 0.05) compared to the asymptomatic group. Multivariate logistic regression analysis of possible risk factors revealed that the wedging angle, foraminal ratio, and multileveled fusion were statistically significant.ConclusionsHigher wedging angle and lower foraminal ratio in the lumbosacral junction were significantly predictive for the incidence of L5 nerve root disorder as well as multiple-leveled fusion. These findings indicate that lumbosacral fixation should be considered for patients with these risk factors even if they have few symptoms from the L5-S1 junction.
Highlights
Lumbar floating fusion occasionally causes postoperative adjacent segment disorder (ASD) at lumbosacral level, causing L5 spinal nerve disorder by L5-S1 foraminal stenosis
One reason for the controversy is the presence of adjacent segment disease (ASD), which mainly occurs at the adjacent intervertebral disc after fusion surgery and decreases adjacent intervertebral disc height
Patient selection and surgical indication Following institutional review board approval, 125 adult patients who underwent primary posterior lumbar decompression and instrumented transforaminal lumbar interbody fusion (TLIF) stopping inferiorly at L5 were included in the study; surgeries were conducted between January 2005 and December 2008
Summary
Lumbar floating fusion occasionally causes postoperative adjacent segment disorder (ASD) at lumbosacral level, causing L5 spinal nerve disorder by L5-S1 foraminal stenosis. The present study aimed to evaluate the incidence and risk factors of postoperative L5 spinal nerve disorder after lumbar interbody fusion extending to the L5 vertebra. Some patients with no symptom from L5-S1 junction undergo lumbar floating fusion surgery terminating at the L5 level. The indication for L5-S1 arthrodesis in patients with an asymptomatic L5-S1 junction is sometimes controversial [1,2,3,4]. One reason for the controversy is the presence of adjacent segment disease (ASD), which mainly occurs at the adjacent intervertebral disc after fusion surgery and decreases adjacent intervertebral disc height.
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