Magnetic resonance imaging of the hip has revealed a number of pathological entities that were unknown until relatively recently. High-resolution scanners in particular (1.5 and 3 Tesla) give us valuable information about the soft tissues of the joint. The great capability of magnetic resonance imaging has led to the treatment of many conditions by hip arthroscopy. Even so, in many cases there is a discrepancy between the findings of hip arthroscopy and those of magnetic resonance imaging, which is due to the inability of the latter to demonstrate soft-tissue lesions in the fine anatomical structures of the joint. This gap is filled by MR arthrography (MRA-MR arthrography).
In cases of femoroacetabular impingement, which account for the large majority of the patients who go on to hip arthroscopy, the diagnosis can readily be made on plain radiographs. However, the accompanying lesions, such as a tear of the labrum, lesions of the articular cartilage or a tear of the ligamentum teres, are not always visible on plain magnetic resonance imaging and require MR arthrography. MR arthrography consists of obtaining a magnetic resonance scan of the joint into which we have first injected a contrast medium.
A recent study published in the journal “Joints” set out to assess the diagnostic accuracy of MR arthrography in detecting the intra-articular lesions of the hip in patients with femoroacetabular impingement syndrome, using hip arthroscopy as the reference standard.
The material consisted of 29 consecutive hip arthroscopies performed in 24 patients. The patients had a mean age of 38.3 years. Various magnetic resonance acquisition techniques were used (such as T2 and T1 sequences, and multiple planes, sagittal, coronal, axial and so on). The sensitivity, the specificity, the positive predictive value and the negative predictive value of MR arthrography were assessed and compared with the findings of hip arthroscopy for the following conditions: chondral lesions of the acetabulum and of the femoral head, degeneration of the labrum, tears of the labrum, synovitis, tears of the ligamentum teres, cam-type lesions, pincer-type lesions, loose bodies and osteophytes.
The sensitivity, the specificity, the positive predictive value and the negative predictive value of MR arthrography were 100, 68.4, 72.7 and 100% respectively for chondral lesions of the acetabulum, 100, 50, 47.3 and 100% respectively for chondral lesions of the femoral head, 33, 85, 20 and 91.6% respectively for tears of the acetabular labrum, 95, 71, 91.3 and 83.3% respectively for degeneration of the labrum, 100, 88, 57.1 and 100% respectively for tears of the ligamentum teres, 33.3, 85, 50 and 73.9% respectively for pincer-type lesions, 50, 96, 66.6 and 92.3%, respectively for loose bodies and 100, 73.9, 50 and 100% respectively for osteophytes.
The authors concluded that MR arthrography plays an important role in detecting the intra-articular lesions associated with femoroacetabular impingement. This investigation is a considerable help in preoperative planning before hip arthroscopy.
Source: “Joints”, June 2018