谁有最难的英语听力材料?

Norway has a public healthcare system with equal distribution of resources and uniform training and licensing of healthcare staff. The population is homogeneous and stable. In general the departments that participated in this study have one preferred surgical strategy for lumbar spinal stenosis without radiological instability. Patients are usually treated at the hospital serving their residential address, limiting referral bias.
We collected data through the Norwegian Registry for Spine Surgery (NORspine), a comprehensive registry for quality control and research. In total, 36 of 40 centres performing lumbar spine surgery in Norway report to the registry. NORspine is linked to the National Registry and Statistics Norway, which contain information on everyone who either is or has been a resident in Norway. According to the Norwegian Directorate of Health approximately 65% of all patients who undergo lumbar spine surgery in Norway are included in NORspine. The inclusion rate is presumably higher for lumbar spinal stenosis related surgery as most of these procedures are scheduled. Participation in the registration by providers or patients was not mandated, nor was participation required as a necessary condition for a patient to gain access to healthcare or for a provider to be eligible for payment. We screened patients who underwent surgery between October 2006 and December 2011 for eligibility. Follow-up time from the date of the operation was one year.
We considered patients to be eligible for the study if they had a diagnosis of central stenosis of the lumbar spine, surgery was at one or two lumbar levels with either open laminectomy or microdecompression, and their data were included in the NORspine registry. Patients were excluded who had undergone previous surgery of the lumbar spine, undergone discectomy as part of the decompression, or had associated spinal conditions (disc herniation, spondylolisthesis, or degenerative scoliosis).

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