Diagnosis by exclusion: Clinical Diagnosis of Femoroacetabular Impingement
Jeffrey J. Nepple, MD, et al.
Clinical Diagnosis of Femoroacetabular Impingement. In Journal of the American Academy of Orthopaedic Surgeons. July 2013. Vol. 21. Supplement. Pp. S16-S19.
Femoroacetabular impingement (FAI) does not have one symptom or one clinical test that confirms it to the physician. Instead, the diagnosis is one of exclusion of other hip problems with similar presentation based on patient history, clinical symptoms, physical examination, and the results of imaging studies.
In this article, orthopaedic surgeons from three well-known and well-respected medical centres (Washington University – St. Louis, Mayo Clinic and Harvard Medical School) teamed up to review the clinical diagnosis of FAI. They provide a description and discussion of the three components needed to make the differential diagnosis: patient history, a step-by-step physical examination, and imaging studies. They say that all three must be reviewed together to establish a diagnosis with certainty
Asking about activity level, especially involving repetitive hip motion, can provide clues as it is a key risk factor for FAI. Labral tears can cause similar symptoms to FAI (eg. painful clicking, popping or snapping with hip motion) but is usually associated with a specific injury, often sports-related.
Determining whether the pain or the other symptoms are intra- or extra-articular is important. Observing how the patient sits, stands, and walks might be telltale; patients with FAI tend to sit with a slouched posture to take pressure off the hip.
Limited hip internal rotation is a red flag for FAI, but most other positive findings only point to the hip as the source of the symptoms, not the actual cause. Likewise, a positive response to injection of an anaesthetic agent into the hip confirms the hip, and not the lumbar spine or the groin, as the true origin of pain.
These additional areas where pain can occur with FAI cause diagnostic confusion, which can be avoided imaging.
Change in the lateral centre-edge and alpha angles as measured on x-rays with no sign of hip dysplasia is diagnostic of deformity associated with FAI. However, MRI-evidence of labral or other cartilage damage helps rule out FAI.
The authors conclude that since there is no one test, symptom, or clinical finding that confirms a diagnosis of FAI, a thorough evaluation is required. •