We injected methylene blue dye into 32 of the facet joints immediately above the defects in 17 consecutive patients with bilateral spondylolysis (34 defects). In 30 of these the dye flowed into a central cavity in the defect of the pars interarticularis and in 20 it passed into the facet joint below the defect. We found macroscopic cavities in 32 of the defects which communicated with the adjacent facet joints and had fibrous capsules. Histological examination showed focal areas of synovial lining consistent with a synovial pseudarthrosis. In most patients requiring surgery for spondylolysis, the defect is a synovial pseudarthrosis which communicates with the facet joint above it, and less often with the facet joint below it. We suggest that stress fractures of the pars may fail to heal because of the presence of
There have been very few reports in the literature of gout and pseudogout of the spine. We describe six patients who presented with acute sciatica attributable to spinal stenosis with cyst formation in the facet joints. Cytopathological studies confirmed the diagnosis of crystal arthropathy in each case. Specific formation of a synovial cyst was identified pre-operatively by MRI in five patients. In the sixth, the diagnosis was made incidentally during decompressive surgery. Surgical decompression alone was undertaken in four patients. In one with an associated degenerative spondylolisthesis, an additional intertransverse fusion was performed. Another patient had previously undergone a spinal fusion adjacent to the involved spinal segment, and spinal stabilisation was undertaken as well as a decompression. In addition to standard histological examination material was sent for examination under polarised light which revealed deposition of urate or calcium pyrophosphate dihydrate crystals in all cases. It is not possible to diagnose gout and pseudogout of the spine by standard examination of a fixed specimen. However, examining dry specimens under polarised light suggests that crystal arthropathy is a significant aetiological factor in the development of symptomatic spinal stenosis associated with cyst formation in a facet joint.
