Intra-Articular Hip Injection Is a Valuable and Cost-Effective Diagnostic Tool but Replacing Advanced Diagnostic Methods Is Not Currently the Way to Go: Commentary on an article by Daniel J. Cunningham, MD, MHS, et al.
FAI syndrome was redefined in an international consensus statement and was endorsed by 25 clinical societies1. Hip pain can be the result of bone lesions and cartilage damage, as well as labral, capsular, and ligamentum teres pathology. Although the H&P and hip radiographs can identify osseous abnormalities, labral or capsular pathology is left undiagnosed, and evaluation of the cartilage is impossible without MRI. With the substantial expansion of hip arthroscopic techniques2, it is possible to address osseous and soft-tissue lesions that, if left untreated, result in deterioration of hip biomechanical function and osteoarthritis3. The novelty of and rapid progression in diagnostic and treatment modalities in hip preservation surgery have resulted in an imbalance of medical knowledge between general practitioners and hip specialists. Cunningham et al. propose that H&P with injection is more likely to be cost effective for general practitioners. Administration of hip injection requires technical expertise since severe damage can occur in the hip when performed inappropriately. The former point is reflected in the results of the study: the willingness to pay (WTP) was $57,000/quality-adjusted life year (QALY) using the injection sensitivity rate in the general practitioner scenario. This amount is almost 50% lower than the accepted WTP threshold in the United States, which is $100,000. The elimination of the use of MRI and MRA in cases of “challenging clinical scenarios” would be reasonable if the level of education was equal between general practitioners and hip specialists because characterizing a clinical scenario as “clinically challenging” relies substantially on clinical expertise, which can differ considerably even among hip specialists.
Hip joint ultrasonography in the diagnosis of FAI syndrome has attracted research interest. Ultrasound is less expensive and more accessible than MRI and MRA examination, but diagnostic accuracy depends on the examiner’s skills. Buck et al. reported that the acetabular labrum can be visualized using ultrasound, but only partially4. Evaluation of the interference of the labrum with the other joint structures during hip motion under ultrasound visualization could help to better understand the patient’s symptomatology and aid in preoperative planning. MRI has been used in studies as the gold standard to validate ultrasound for the diagnosis of cam impingement, with promising outcomes4,5, but not enough evidence exists to establish it as a reliable examination to diagnose FAI syndrome. Another advantage of preoperative MRI examination is the detection of occult malignant bone or soft-tissue tumors concomitant with FAI pathology, where arthroscopic hip intervention could cause tissue spread and subsequent metastatic disease.
While Cunningham et al. support the reduction of MRI and MRA usage to diagnose FAI syndrome, currently there is no other validated tool to diagnose hip soft-tissue and cartilage lesions.