Spondylolisthesis, forward sliding of a vertebra over the underlying vertebra, secondary to a fracture in the pars interarticularis, is known as isthmic spondylolisthesis. Pars interarticularis is a tubular bone connecting the upper and lower facet joints of the vertebrae. Isthmic spondylolisthesis is more common in the lower spine. Weightlifters, football players and gymnasts are commonly affected.
Pars interarticularis fracture usually occurs due to repetitive stress on the bone by activities such as heavy lifting, stooping or twisting. The fracture causes a detachment of the front portion from the back portion of the vertebra making the segment unstable causing it to slide forward leading to isthmic spondylolisthesis.
As the front part of the vertebra is more commonly involved, narrowing of the spinal canal is less likely. Hence, even though a majority of patients with isthmic spondylolisthesis have displaced vertebrae, they usually experience only mild back pain and leg pain, on exertion. A few patients may, however, experience symptoms similar to stenosis, which may include back pain, leg pain, weakness of arm or leg, numbness or tingling sensation in the legs, muscle spasms, tight hamstring muscles and improper gait or limp. In rare cases it may also result in loss of bladder or bowel function which is a medical emergency.
Diagnosis of Isthmic spondylolisthesis includes medical history, physical and neurological examinations. X-ray of the spine is ordered to confirm the diagnosis. An X-ray can detect a loss of height of the discs, presence of bone spurs and the displaced vertebra. Other imaging tests such as MRI and CT scans may also be performed. MRI is usually performed to assess the compression of nerves.
Surgery is rarely required for the management of isthmic spondylolisthesis. Nonsurgical treatment including brief period of rest, activity modification, pain medications, non-steroidal anti-inflammatory drugs (NSAIDs), muscle relaxants, spinal injection and physical therapy may be beneficial. Back braces may also be recommended to support the back and reduce mechanical pain. Acupuncture may also be beneficial in few cases.
Spinal surgery is rarely recommended for this condition but may be necessary in patients who do not improve with non-surgical treatment after 3 to 6 months or those with spinal instability and neurologic dysfunction.
The surgery for isthmic spondylolisthesis comprises of laminectomy and spinal fusion. Laminectomy relaxes the spinal canal reducing the pressure on the nerves providing symptomatic relief while spinal fusion stabilizes the spine by the fusion of the painful displaced vertebrae into one unit with the help of screws.
Consult your doctor for any queries about isthmic spondylolisthesis and its treatment.