Secondary cleft sign as a marker of injury in athletes with groin pain: MR image appearance and interpretation.
PURPOSE: To determine whether the secondary cleft sign demonstrated in the symphysis pubis at magnetic resonance (MR) imaging is a marker of injury in athletes presenting with groin pain. MATERIALS AND METHODS: Ethics review board approval was not required for studies involving retrospective image or case record review; informed consent for review was not required. Eighteen male athletes (mean age, 24 years; age range, 19-32 years) were included for study. All patients underwent radiography and MR imaging (coronal fast spin-echo T1-weighted, transverse fast spin-echo T2-weighted, and coronal turbo short inversion time inversion-recovery [STIR] imaging) of the pelvis. Subsequent image-guided nonionic contrast material injection was followed by a 0.5% bupivacaine hydrochloride (1 mL) and methyprednisolone acetate (20 mg) injection into the central cleft of the symphysis pubis. Comparison was made between imaging findings at symphyseal cleft injection and appearances at preprocedure MR imaging, with specific reference to the presence of a secondary cleft. The sensitivity and specificity of MR imaging in demonstrating the secondary cleft sign were compared with those of the reference standard, imaging at symphyseal cleft injection. MR images from a reference group of 70 asymptomatic athletes who underwent STIR imaging of the pelvis were analyzed for evidence of a secondary cleft. RESULTS: Osteitis pubis was diagnosed in six patients on the basis of radiography and/or MR imaging. A secondary cleft was identified in 12 of 18 patients at MR imaging, was best visualized at coronal STIR imaging, and was confirmed in each patient during contrast material injection into the central physiologic symphyseal cleft. In no patient was a secondary cleft identified at symphyseal cleft injection and not identified at MR imaging (sensitivity and specificity, 100%). In each patient, the side of the secondary cleft corresponded to the side of symptoms that responded to local anesthetic and steroid injection. Four of the six patients with osteitis pubis had evidence of a secondary cleft. In one patient, a secondary cleft was not identified at MR imaging or symphyseal cleft injection, but adductor avulsion was identified at MR imaging. No evidence of a secondary cleft sign at MR imaging was identified in the reference group. CONCLUSION: The secondary cleft sign demonstrated at MR imaging is a marker of groin injury in athletes presenting with groin pain.