Uppsala Spinal Stenosis Study

Background

Lumbar spinal stenosis (LSS) is characterized by low back and leg pain, walking disturbances and sometimes instability, impaired balance and numbness of the lower limbs. This condition is caused by degenerative changes in the lumbar spine including bulging discs, osteophytes from the arthritic facet joints and thickened ligamentum flavum which together cause narrowing of the spinal canal and thus affect the lumbar nerve roots. LSS affects mainly older populations and is unusual under 50 years old. This diagnosis is attracting more and more interest due to the aging population with increasing demands for physical activity. LSS is the most common indication for spinal surgery. The surgical treatment involves relieving the pressure from the nerve structures in the stenotic segments through a posterior approach. The hypertrophic ligaments and parts of the facet joints are removed (i.e., decompression). Adding fusion to the decompression for stabilization of the decompressed segment has not been shown to provide superior results than decompression alone. In several studies, surgery has been shown to have better results than the conservative treatment. However, methodological difficulties and a large proportion of cross-over in these studies indicate that there is still uncertainty about whether surgery is generally a better option.

After decompression, only 60-70% of patients reported to be satisfied with the result and a minor proportion of them experienced even no improvement at all [Strömqvist]. Conservative treatment has shown in some studies to have good results for some patient groups and other studies have shown that the benefit of the surgical treatment decreases over time and that physical exercise may reduce the need for surgery. Moreover, surgery itself has a positive placebo effect that can improve symptoms in some diseases.

It has been speculated whether the compression of the nerve roots causes in some patients permanent nerve damage with muscle denervation, while in other cases a reinnervation and recovery of the function may occur. Results from neurography and EMG studies have been shown these modalities to have a possible predictive value for the natural process of LSS. If a neurophysiological examination could be able to predict which patients are able to benefit from surgery, many patients could avoid surgery and the risks involved in it.

The degeneration of the lumbar spine is progressively impairing the spinal sagittal balance. The need to make extensive correction and fusion in addition to the decompression in order to restore the sagittal balance is debated among spinal surgeons. The experience gained from previous RCTs is that the patients' back pain is reduced by decompression only. Many patients also report that their posture improved after decompression alone.