ABSTRACT
STUDY DESIGN: This study is a prospective, clinical study assessing the efficacy of selective decompression of the level responsible in a two-level stenosis in accordance with the neurological findings defined by the gait load test with a treadmill. PURPOSE: To clarify the clinical features of multilevel lumbar spinal stenosis (LSS) regarding the neurological level responsible for the symptoms, neurogenic claudication, and outcomes of selective decompression. OVERVIEW OF LITERATURE: Most spine surgeons have reported that multilevel compression of the cauda equina induces a more severe impairment of the nerve function than a single-level compression. However, the clinical effects of multilevel LSS on the cauda equine and nerve roots are unknown. METHODS: A total of 21 patients with lumbar spinal canal stenosis due to spondylosis and degenerative spondylolisthesis were selected. The level responsible for the symptoms in the two-level stenosis was determined from the neurological findings on the gait load test and functional diagnosis based on a selective nerve root block. All patients underwent a prospective, selective decompression at the level neurologically responsible only. The average follow-up period was 2.6 years (range, 1 to 6 years). The postsurgical outcome was defined using the Visual Analogue Scale (VAS) at the post-gait load test, 2 weeks after surgery, 3 months after surgery and at the last follow up. RESULTS: Before surgery, the mean threshold distance and mean walking tolerance was 34.3 m and 113 m, respectively. All patients had neurogenic claudication and 19 of the patients had cauda equina syndrome, including hypesthesia in 11 cases, muscle weakness in 5 cases and radicular pain in 7 cases. Selective nerve blocks to determine the level responsible for the lumbosacral symptoms in 2 cases revealed a mean VAS score of 7.1, 2.61, 3.04, and 3.47 at the post-gait load test, 2 weeks after surgery, 3 months after surgery and at the last follow up, respectively. All subjects underwent surgery. After the operation, neurogenic claudication with or without cauda equna syndrome subsided in all patients. CONCLUSIONS: The gait load test allows an objective and quantitative evaluation of the gait characteristics of patients with lumbar canal stenosis and is useful for determining the appropriate level for surgical treatment.