MRA effective in detecting ligamentum teres tears
Axial T2-weighted MR Arthrogram images of normal ligamentum teres (top) marked with arrows and an abnormal hypertrophied partially torn ligamentum teres (bottom). Note the marked enlargement, increased signal and irregular margins of the partial torn ligamentum teres.
By Elaine Fiedler
Magnetic resonance arthrography (MRA) of the hip can effectively detect partial tears of the ligamentum teres, according to a study presented by the authors of Paper 346. Their paper found that MRA substantially agrees with surgical findings and that the foveal axial area is key in the evaluation.
Advancements in hip arthroscopy have provided new awareness of injuries to the ligamentum teres, especially in athletes. Individuals who participate in high-impact sports (football or hockey) or in sports that require excessive range of motion (ballet or martial arts) may be particularly susceptible to these injuries.
Hypertrophic changes of ligamentum tears are at risk for impingement and tearing. Symptoms can include pain, clicking, stiffness, and/or giving way. Although hip arthroscopy is the “gold standard” for evaluating ligamentum teres injuries, this IRB-approved, retrospective Level II study found that MRA can also be useful in diagnosing partial tears.
The study involved 68 patients (45 females and 23 males) with a mean age of 35.1 years (range: 15 years to 60 years). All had arthroscopic hip surgery for the primary diagnosis of a labral tear. All surgeries were performed by a single surgeon; complete surgical records and an electronic MRA for each patient was available for review.
Arthroscopic evaluation showed that 58 patients had partial tears of ligamentum teres and 10 were normal. The MRAs were evaluated by a single musculoskeletal radiologist who was blinded to results. The ligament was assessed for the presence of partial tears based on changes in signal and morphology. Several tests were used to compare the MRA findings with surgical findings.
The overall agreement between MRA and surgical findings was 93 percent. To reduce the effect of chance, researchers applied a kappa coefficient, which resulted in a “substantial” (0.72) measure of agreement. Researchers also measured sensitivity, specificity and positive/negative predictive values. Results showed:
• 96 percent of patients (55 of 57) with positive MRA had a partial tear identified during surgery.
• 73 percent of individuals (8 of 11) with a negative MRA did not have a partial tear identified during surgery.
“In addition to finding that MRA of the hip seems accurate in detecting partial tears of the ligamentum teres,” wrote the authors, “this study also found that the perifoveal cross-sectional area was larger in individuals with partial tears. This finding implies that this is a key area to evaluate in individuals with hip symptoms who are referred for an MRA.”
Although preoperative identification of ligamentum teres tears has been difficult, the authors hope that as surgeons and radiologists familiarize themselves with the concept of ligamentum teres pathologies, preoperative detection will increase.
Based on their findings, the authors conclude that “MRA assessment of the hip should include the perifoveal area of the ligamentum teres on the diagnostic checklist to help guide clinical evaluation and preoperative planning.” They are planning prospective studies that will include consensus reading to help eliminate interpretative bias and assess the ability of those without subspecialty training to reproduce the results.
The investigative team included Marc J. Philippon, MD, and Bryan Kelly, MD, of Vail, Colo., and Derek R. Armfield, MD; Jeffrey D. Towers, MD; Douglas D. Robertson, MD, and Robroy Martin, PhD—all of Pittsburgh. Dr. Philippon serves as a consultant to Smith & Nephew and receives research support, funding and royalties from the company. Dr. Kelly received funding from Smith & Nephew.