Spondylolysis is a fracture of the pars interarticularis in the lumbar spine. The pars articularis is also known as the pedicle. It’s the area of bone between the upper and lower facet (spine) joints.
Motion at the site of the fracture can create a pseudoarthrosis or false joint. Low back pain is common with this condition. But the exact cause of the pain remains a mystery. Some experts suggest the extra motion at the wrong place causes the pain. Others believe the fibrocartilage that fills in the defect has nerve endings.
Japanese scientists studied the spondylitic tissue removed from 17 patients. All patients were adults with low back and/or leg pain from spondylolysis. Tissue samples were prepared, stained, and studied under a light microscope.
X-rays of flexion-extension motion were also taken and studied. Severity of low back pain was recorded. Both of these measures were compared to the tissue samples taken.
They found the spondylolytic tissue was made of the same type of tissue found in tendons and ligaments. It was dense, fibrous tissue made up of collagen fibers. There were no nerve endings or nerve tissue. There were some elastic fibers present. These were part of the normal ligament along the spine and not really part of the spondylolytic defect.
The authors were unable to find the cause of pain associated with spondylolysis. The healing spondylolytic tissue was not linked with low back pain. Neither was the loose lamina (tissue next to the pedicles). The ligament-like tissues that form to stabilize the fractured pedicles may be the cause of the pain, but more study is needed to find the exact link.