A magnetic resonance image (MRI) alone may not be enough to accurately diagnose the existence or extent of degenerative spondylolisthesis, a common and often painful spine condition.
The study was presented at the 29th Annual Meeting of the North American Spine Society (NASS). “Previous studies have suggested that if we rely solely on conventional supine MRIs to diagnosis spondylolisthesis, we may not have the full picture and could miss opportunities to quickly identify their source of pain,” says Charles Reitman, professor and vice chairman of Orthopaedic Surgery at Baylor College of Medicine and NASS Annual Meeting Program Chair. “This new study is interesting because it quantifies the difference between the results of a supine MRI and standing lateral flexion-extension (SLFE) radiographs in patients with DS at L4-5.”
In “Sensitivity of MRI in the diagnosis of L4-5 degenerative spondyloisthesis,” a retrospective imaging study, 103 patients diagnosed with L4-5 DS with SLFE films as well as supine MRI were evaluated. Exclusion criteria included previous lumbar surgery, trauma, tumour, infection, spondylolysis, adjacent spondylolisthesis, scoliosis and imaging dates over one year apart.
The researchers found that the conventional supine MRI had a sensitivity of 78% for detecting degenerative spondylolisthesis compared to 100% for flexion-extension and 98% for lateral standing films. Significant differences in slip distance, slip percentage and disc height between lateral radiographs and MRIs were also observed. Patients with mobile degenerative spondylolisthesis were more likely to have a greater slip percentage. The researchers defined “mobile” as a slip reduction of 3% or more, supine versus standing.
“Because MRIs are conventionally done when the patient is lying on their back, with no axial load, there is a tendency for the spondylolisthesis to either reduce entirely or reduce in part, minimising the extent of spondylolisthesis that you see,” says Benjamin Kuhns, a fourth-year medical student at Case Western, who presented the study findings. “So, if you only get an MRI, you might be either under-diagnosing spondylolisthesis or not seeing it in its true context. This may have implications on the type of surgery performed on the patient.”
Based on their research, Kuhns and his colleagues suggest that physicians should also include SLFE radiography as part of the complete workup of patients in whom degenerative spondylolisthesis is suspected.
