Diagnostic Accuracy of Physical Examination Tests in Core Muscle Injury

Abstract

Background: Core muscle injury (CMI), often referred to as a sports hernia, is a common cause of groin pain in athletes characterized by concomitant injury to the insertion of the adductor longus and the rectus abdominis muscles. Currently, the literature on CMI is sparse with no standardized physical examination tests used in the diagnosis of this type of injury. Purpose: To determine the diagnostic accuracy of various physical examination tests in the diagnosis of CMI. Study Design: Cohort study (Diagnosis); Level of evidence, 3. Methods: A consecutive series of patients evaluated by the senior author with symptoms consistent with CMI were included. Four physical examination tests were routinely performed in these patients by the senior author and were noted in each patient’s chart as positive or negative: (1) pain with resisted cross-body sit-up in figure-of-4 position, (2) pain with straight-leg sit-up, (3) pain with resisted hip flexion in external rotation (external rotation Stinchfield test), and (4) the presence of an adductor contracture. CMI was independently diagnosed by a reference standard (magnetic resonance imaging [MRI]). All MRI scans were read by a musculoskeletal fellowship-trained radiologist. The sensitivity and specificity of each physical examination test alone and in combination were calculated based on this reference standard. Results: A total of 81 patients were included in this study. MRI was positive for a CMI in 39 patients (48%) overall. Both the cross-body sit-up test and the presence of an adductor contracture were found to have a sensitivity of 100% (specificity, 3% for both). The external rotation Stinchfield test was found to have the highest specificity of 60% (sensitivity, 15%). The sensitivity of all 4 physical examination tests in combination was found to be 100% (specificity, 0%). Conclusion: Certain physical examination maneuvers can be used to assist in the diagnosis of a CMI. The cross-body sit-up test and the presence of an adductor contracture are highly sensitive but nonspecific tests for CMI and therefore should be used in conjunction with diagnostic imaging before deciding on an appropriate treatment course.