Diagnosis of hip joint pathology

[injuryupdate]

Interesting abstract from the American Journal of Sports Medicine, suggesting that getting a local injection (under imaging) into the hip is a more reliable way of finding that the problem comes from the hip joint than most imaging modalities (e.g. MRI):

The American Journal of Sports Medicine 32:1668-1674 (2004)
© 2004 American Orthopaedic Society for Sports Medicine

Diagnostic Accuracy of Clinical Assessment, Magnetic Resonance Imaging, Magnetic Resonance Arthrography, and Intra-articular Injection in Hip Arthroscopy Patients
J. W. Thomas Byrd, MD* and Kay S. Jones, MSN, RN

Background: Hip arthroscopy has defined elusive causes of hip pain.

Hypothesis/Purpose: It is postulated that the reliability of various investigative methods is inconsistent. The purpose of this study is to evaluate the diagnostic accuracy of these methods.

Study Design: Retrospective review of prospectively collected data.

Methods: Five parameters were assessed in 40 patients: clinical assessment, high-resolution magnetic resonance imaging, magnetic resonance imaging with gadolinium arthrography, intra-articular bupivacaine injection, and arthroscopy. Using arthroscopy as the definitive diagnosis, the other parameters were evaluated for reliability.

Results: Hip abnormality was clinically suspected in all cases with 98% accuracy (1 false positive). However, the nature of the abnormality was identified in only 13 cases with 92% accuracy. Magnetic resonance imaging variously demonstrated direct or indirect evidence of abnormality but overall demonstrated a 42% false-negative and a 10% false-positive interpretation. Magnetic resonance arthrography demonstrated an 8% false-negative and 20% false-positive interpretation. Response to the intra-articular injection of anesthetic was 90% accurate (3 false-negative and 1 false-positive responses) for detecting the presence of intra-articular abnormality.

Conclusions: In this series, clinical assessment accurately determined the existence of intra-articular abnormality but was poor at defining its nature. Magnetic resonance arthrography was much more sensitive than magnetic resonance imaging at detecting various lesions but had twice as many false-positive interpretations. Response to an intra-articular injection of anesthetic was a 90% reliable indicator of intra-articular abnormality.

Key Words: hip arthroscopy • evaluation • magnetic resonance imaging (MRI) • magnetic resonance arthrography • hip pathology

[hhh]

Won't it depend on what you are trying to image? eg Plain X-ray is effective at diagnosing most intra-articular disorders -Perthes disease, CHD, SFCE, MRI will hit osteonecrosis, cancer, pigmented villonodular synovitis and synovial chondromatosis as a source of pain etc

I read that arthroscopy as a diagnostic tool should be reserved for those patients with an intra-articular source of pain without a clear diagnosis after careful history, physical examination and radiographic studies. But agree that for certain conditions arthrocopy is superior to the MRI and its variants.

[injuryupdate]

Good points. I think X-ray is pretty much a given in anyone with a suspected hip joint problem and can cover most of the disaster type problems as an early screen.

I think the point of this paper is that whilst MRI is becoming more and more common (and justifiably so) it is not the holy grail as far as saying that "this person has a significant hip joint problem". MRI has lots of false positives and false negatives.

The technique of local anaesthetic injection is a good one for the patient with a normal X-ray, equivocal MRI, who is in pain and wants to know whether he/she should consider hip arthroscopy. If the injection takes the pain away for half a day, then an arthroscopy of the joint may be a good move. If the injection doesn't help, then the diagnosis is probably something else (soft tissue) and arthroscopy is best avoided.

[hhh]

What about a labrum injury? - arthroscopy currently represents the gold standard in both the diagnosis and treatment of this injury

[injuryupdate]

I would agree that arthroscopy is the gold standard for diagnosis, but perhaps local injection is better than MRI at saying 'yes this pain is coming from the hip joint'.

Problem with labral injuries is that we don't know:
(1) how many asymptomatic ones there are out there.
(2) whether arthroscopy leads to better long-term results than conservative management.

My view on labral tears is:
(1) diagnosis is useful, if they can be seen on MRI or suspected by local injection block.
(2) long-term prognosis after surgery is perhaps progression of joint degeneration.
(3) therefore, if the patient can live with the pain of a labral tear (i.e. still play sport) then surgery is best avoided. If the pain keeps the patient out of sport, if it is coming from the hip then do an arthroscopy.

Of note, it seems that hip arthroscopy is a lot more popular in Melbourne than Sydney.

[hhh]

On the other hand, early diagnosis of labral tears is important as they may be linked to the progression of hip osteoarthritis (particularly in athletes). If in fact the labrum is a weight bearing structure one would suspect that labral disruption would lead to non-symmetric force distribution on the acetabulum and femoral head.

Furthremore, conventional MRI is not thought to be of use in the visualization of labral tears. Diagnostic confidence is limited by the normal variability in labral size and shape, by the joint capsule collapsed against the acetabular rim and by the difficulty in distinguishing tears of the labrum from pseudotears caused by the normal labral articular cartilage interface

The problem is that only recently has the acetabular labrum been recognized within the orthopedic literature as a source of hip pain. Data from cadaveric studies indicate that labral lesions are a common occurrence. The short-term results of arthroscopic debridement of labral tears have been favorable

Future research must investigate the long-term outcomes of partial labrectomy, as well as the efficacy of conservative approaches to care