MR imaging of early hip joint degeneration

Advanced Magnetic Resonance Imaging in Osteoarthritis

Osteoarthritis (OA) is one of the most common causes of disability throughout the world. Current therapeutic strategies are aimed at preventing the development and delaying the progression of OA, as well as repairing or replacing worn articular surfaces, because the regeneration of lost hyaline articular cartilage is not currently a clinically feasible option. Imaging is useful in formulating treatment strategies in patients at risk for OA, allowing assessment of risk factors, the degree of preexisting tissue damage, and posttreatment monitoring. Magnetic resonance imaging (MRI), in particular, provides in-depth evaluation of these patients, with optimal clinical sequencing allowing sensitive assessment of chondral signal and morphology, and the addition of advanced MRI techniques facilitating comprehensive evaluation of joint health, with increased sensitivity for changes in articular cartilage and surrounding joint tissues.

Magnetic Resonance Imaging of the Hip

Hip pain is common in all age groups, and osteoarthritis of this joint is an increasingly recognized problem particularly in aging populations. One of the primary goals in the diagnostic evaluation in patients with hip pain is to identify and correct pathologies that could progress to osteoarthritis. Magnetic resonance imaging (MRI) has become an important noninvasive method for characterizing hip anatomy and pathology in these patients. Improvements in MRI hardware and techniques have allowed high spatial and contrast resolution imaging to detect subtle abnormalities, such as acetabular labral and articular cartilage injuries, which often contribute to patient symptoms. Newer MRI techniques, such as delayed gadolinium-enhanced MRI of cartilage and T2 mapping, can give insight into the biochemical structure of tissues such as the articular cartilage. In turn, these can allow quantitative assessment and enable imagers to more directly compare the findings of patients at earlier stages of disease. It is important to understand the fundamental principles of various MRI techniques and their limitations to know when these techniques can best be applied. In addition, understanding of normal hip anatomy and common anatomic variants is useful for being able to accurately detect and localize areas of pathology and to prevent misinterpreting normal structures as diseased. The aims of this work were to briefly review normal hip anatomy and common anatomic variants seen on routine MRI examination, to discuss principles often used in high-resolution hip MRI and newer techniques for biochemical evaluation, and to examine several intra-articular pathologic conditions of the hip joint that are of current clinical interest.

Imaging SCFE: diagnosis, treatment and complications

Slipped capital femoral epiphysis (SCFE) is a common orthopedic disorder in children. It can lead to avascular necrosis, cartilage loss, femoroacetabular impingent (FAI) and early osteoarthritis. The consequences of SCFE are worsened by delays in diagnosis and proper management. Radiography is the primary imaging modality used to evaluate SCFE; however, MR, CT and bone scintigraphy have important roles. Preoperatively, these modalities assist in surgical planning and predicting prognosis; postoperatively, they provide assessment of hardware failure, ischemic necrosis and morphology predisposing to FAI. Emphasizing a multimodality approach, this review addresses the imaging diagnosis of SCFE, the expected postoperative appearances and the findings of immediate and long-term complications.

MRI of hip cartilage: joint morphology, structure, and composition

BACKGROUND

Accurate, reproducible, and noninvasive assessment of hip cartilage is clinically relevant and provides a means by which to assess the suitability of candidates for arthroscopic or open surgical procedures and the response to such interventions over time. Given the relatively thin cartilage of the hip and the complex spherical anatomy, however, accurately assessing the cartilage poses a challenge for traditional MRI techniques.

QUESTIONS/PURPOSES

We assessed the current status of imaging articular cartilage of the hip through a comprehensive review of recent literature.

METHODS

We performed a literature review using PubMed. Topics included quantitative MRI, imaging of the hip cartilage and labrum, femoroacetabular impingement syndrome, and osteoarthritis of the hip. WHERE ARE WE NOW?: With the use of high in-plane and through-plane resolution, reproducible assessment of hip cartilage and labrum is clinically feasible. More recent quantitative MR techniques also allow for noninvasive assessment of collagen orientation and proteoglycan content in articular cartilage, thus providing insight into early matrix degeneration. These techniques can be applied to cohorts at risk for osteoarthritis, helping to predict cartilage degeneration before symptoms progress and osteoarthritic changes are visible on radiographs. WHERE DO WE NEED TO GO?: Prospective longitudinal data registries are necessary for developing predictive models of osteoarthritis and subsequent joint failure to assess the results of surgical intervention and predict the timing of arthroplasty. HOW DO WE GET THERE?: By establishing more hip cartilage registries, a correlation can be made between subjective measures and morphologic MRI to assess the cartilage, labrum, bone, and synovial lining of the hip.

Are extra-labral MR findings useful in the diagnosis of a labral tear?

OBJECTIVE

To determine diagnostic performance statistics of extra-labral magnetic resonance (MR) findings for detection of labral tears in a population of patients with clinical suspicion of this diagnosis.

MATERIALS AND METHODS

Seventy-nine patients clinically suspected of having a labral tear (who underwent arthroscopy) had their MR studies retrospectively reviewed to determine the presence of lateral acetabular oedema-like marrow signal, ganglia, dysplastic femoral bumps, synovial herniation pits and geodes. These findings were then correlated with the arthroscopic presence (or absence) of a labral tear.

RESULTS

All findings (lateral acetabular oedema-like marrow signal, ganglia, dysplastic femoral bumps, synovial herniation pits and geodes) had a specificity and positive predictive value (PPV) of 100%. Lateral acetabular oedema-like marrow signal had a sensitivity of 35% and 20% negative predictive value (NPV). This was the only statistically significant finding (P < 0.05). The sensitivity and NPV of ganglia were 12% and 16%, dysplastic femoral bumps (12%, 16%), synovial herniation pits (4%, 14%) and geodes (6%, 15%) respectively, (P > 0.05).

CONCLUSION

Lateral acetabular oedema-like marrow signal is a useful sign (100% PPV) in the MR diagnosis of a labral tear, if one is clinically suspected. The other findings (ganglia, dysplastic femoral bumps, synovial herniation pits and geodes) were not statistically significant. Further studies are required to evaluate these.