Radial-sequence magnetic resonance imaging in evaluation of acetabular labrum

Do normal radiographs exclude asphericity of the femoral head-neck junction?

Asphericity of the femoral head-neck junction is one cause for femoroacetabular impingement of the hip. However, the asphericity often is underestimated on conventional radiographs. This study compares the presence of asphericity on conventional radiographs with its appearance on radial slices of magnetic resonance arthrography (MRA). We retrospectively reviewed 58 selected hips in 148 patients who underwent a surgical dislocation of the hip. To assess the circumference of the proximal femur, alpha angle and height of asphericity were measured in 14 positions using radial slices of MRA. The hips were assigned to one of four groups depending on the appearance of the head-neck junction on anteroposterior pelvic and lateral crosstable radiographs. Group I (n = 19) was circular on both planes, Group II (n = 19) was aspheric on the crosstable view, Group III (n = 4) was aspheric on the anteroposterior view, and Group IV (n = 13) was aspheric on both views. In all four groups, the highest alpha angle was found in the anterosuperior area of the head-neck junction. Even when conventional radiographs appeared normal, an increased alpha angle was present anterosuperiorly. Without the use of radial slices in MRA, the asphericity would be underestimated in these patients.

Magnetic resonance imaging of the hip

Standard magnetic resonance imaging (MRI) as well as MR arthrography (MRA) have been important diagnostic tools to assess for a spectrum of clinical presentations related to the hip. MRA has allowed the radiologist to closely examine intracapsular structures such as the acetabular labrum. In this article, we provide a general review of soft tissue and osseous anatomy of hips, especially focusing on the MR appearances of the acetabular labrum and the osseous morphology of the greater trochanter and ischial tuberosity with their muscle and tendon attachments. In addition, current topics in recent literature will be discussed such as femoroacetabular impingement (FAI) and rotator cuff tears of the hip.

Usefulness of radial contrast-enhanced computed tomography for the diagnosis of acetabular labrum injury

PURPOSE

The purpose of this study was to evaluate the usefulness of radial contrast-enhanced computed tomography (CT) in the diagnosis of acetabular labrum injury.

METHODS

We studied 21 hip joints in 21 patients (8 joints in 8 male patients and 13 joints in 13 female patients), aged between 16 and 81 years (mean, 43 years) at examination, who underwent both radial contrast-enhanced CT and hip arthroscopy. Plain radiography showed no abnormalities in the bone and joint in 19 joints and acetabular dysplasia in 2 joints. When we performed radial contrast-enhanced CT, a mixture of 5 mL of 2% lidocaine chloride and 10 mL of 64% iotrolan was injected intra-articularly under x-ray fluoroscopy. CT was conducted with a 4-slice multidetector CT system operated at a voltage of 120 kilovolt peak, current of 300 mA, collimation beam of 2 mm, field of view of 320 mm, slice thickness of 0.5 mm, table speed of 44 mm/s, and helical pitch of 5.5. Images were reconstructed by computer software for radial slices at 15 degrees intervals perpendicular to the labral rim. The mean interval between the CT scan and arthroscopy was 13.2 days.

RESULTS

By contrast-enhanced CT, acetabular labrum tears were observed in 12 joints, loss of acetabular labrum was found in 1 joint, and no abnormalities were present in 8 joints. By arthroscopy, acetabular labrum tears were observed in 13 joints, loss of acetabular labrum was found in 1 joint, and no abnormalities were present in 7 joints. When the results of the 2 methods were compared, 12 joints had true-positive findings, 8 joints had true-negative findings, and 1 joint had a false-negative finding. Therefore contrast-enhanced CT had a sensitivity of 92.3%, specificity of 100%, and accuracy of 95.2%.

CONCLUSIONS

The sensitivity, specificity, and accuracy of radial contrast-enhanced CT for the diagnosis of acetabular labrum injury are 92.3%, 100%, and 95.2%, respectively. We recommend radial contrast-enhanced CT for the diagnosis of acetabular labrum injury in patients in whom magnetic resonance imaging is contraindicated.

LEVEL OF EVIDENCE

Level IV, diagnostic study.

Evaluation of radial-sequence imaging in detecting acetabular labral tears at hip MR arthrography

OBJECTIVE

In recent years, radial imaging has been advocated for improved visualization of the acetabular labrum in magnetic resonance arthrography of the hip. The purpose of this study was to investigate whether radial imaging demonstrates labral tears not visible on standard imaging planes.

METHODS

Fifty-four consecutive magnetic resonance (MR) arthrograms of the hip that included radial imaging over 2 years were retrospectively analyzed by two radiologists. Standard imaging planes and radial imaging were reviewed for identification of labral tears in four specific areas of the labrum: anterosuperior, posterosuperior, anteroinferior, and posteroinferior. The standard imaging sequences include fat-saturated spin-echo T1-weighted images in the coronal and oblique axial planes, non-fat-saturated T1-weighted images in the coronal and sagittal planes, and T2-weighted sequence in the axial plane. Radial imaging was performed as previously described using fat-saturated T1-weighted sequences.

RESULTS

Using standard imaging planes, 50 anterosuperior, 31 posterosuperior, 10 anteroinferior, and 9 posteroinferior labral tears were detected in 54 MR arthrograms of the hip. Using radial sequences alone, 44 anterosuperior, 25 posterosuperior, 9 anteroinferior, and 5 posteroinferior labral tears were detected. In all four areas of the labrum, the radial imaging did not show any labral tear not seen on standard imaging planes.

DISCUSSION

In MR arthrography of the hip, radial imaging did not reveal any additional labral tears. Standard imaging planes sufficiently demonstrate all acetabular labral tears.

Hip pain in adults: MR imaging appearance of common causes

To determine the exact origin of hip pain can be challenging. Symptoms apparently originating from the hip may arise from the pelvis, the sacroiliac joint, the lumbar spine, periarticular structures such as muscles and bursae, or from unexpected sites such as the abdominal wall, the genitourinary tract, or the retroperitoneal space. This article reviews the differential diagnosis of hip pain arising from the hip and surrounding structures and the role of different imaging methods with emphasis on magnetic resonance imaging where most recent advances have occurred.

Relationship between acetabular labrum evaluation by using radial magnetic resonance imaging and progressive joint space narrowing in mild hip dysplasia

OBJECTIVE

The aim of this study was to investigate the relationship between abnormal acetabular labrum depicted by radial magnetic resonance and progressive joint space narrowing (JSN) of hip dysplasia.

METHODS

Subjects were 23 joints [21 patients; mean age: 35.1 years (16-53 years)] that had acetabular dysplasia with lateral center-edge angle of Wiberg (CE angle) greater than 5 degrees and smaller than 25 degrees (mean, 16.4 degrees ), which did not show any arthrotic changes on plain radiograms and were followed up for 3 years or longer. Radial images of acetabular labrum were classified into three stages.

RESULTS

Progression of JSN was not significantly related to CE angle but to progression of MRI stage (P=.006). In multivariate analysis, one rank progression of MRI stage was significantly associated with progression of JSN (adjusted OR=11.41, 95% CI: 1.51-86.24, P=.018).

CONCLUSION

Our findings showed that in patients whose acetabular dysplasia has 5-25 degrees CE angle, MRI staging based on radial MRI is a better factor for prediction of progression of JSN than CE angle.

Imaging of the Acetabular Labrum

The acetabular labrum is a critical structure within the hip joint. It is a significant cause of pain, and it plays an integral role in the development of osteoarthritis. This article reviews the normal anatomy, imaging techniques, and normal MR appearance of the labrum. The clinical presentation of labral tears and their association with developmental dysplasia and femoroacetabular impingement are discussed. The controversy regarding the presence or absence of a sublabral sulcus also is addressed.

Bombelli's valgus-extension osteotomy for osteoarthritis due to acetabular dysplasia: results at 10 to 14 years

Severe osteoarthritis due to acetabular dysplasia (n = 17) was treated with valgus-extension osteotomy, and the patients' clinical outcomes 10-14 years after operation were evaluated according to clinical factors (Japanese Orthopaedic Association hip score; JOA score) and by roentgenography. The mean JOA score 10 years or later had improved by 22 points compared with the preoperative score. On roentgenography, joints which had preoperative roof osteophyte had better postoperative formation of roof osteophyte. The JOA score was higher in the 12 joints which had osteophyte 5 mm or longer than in those joints with osteophyte that was 5 mm or shorter. Postoperative joint space widening occurred in 15 joints (88.2%) 3-6 months postoperatively, and it reached the maximum at 3-5 years. In patients who had a large bone cyst in the femoral head preoperatively, the cyst collapsed, and deformation of femoral head occurred after operation, but remodeling of the joint surface occurred naturally and the congruity improved. In the 6 joints in which the preoperative acetabular head index was less than 60% and the acetabular angle was larger than 30 degrees, the JOA score at 10 years or later was lower than that of the other joints. Based on these findings, valgus-extension osteotomy was evaluated as a useful surgical method for advanced or terminal osteoarthritis in young or middle-aged patients. Predictive factors for long-term prognosis would be the preoperative length of roof osteophyte, joint space widening, and the degree of femoral head covering.

Radial magnetic resonance imaging and pathological findings of acetabular labrum in dysplastic hips

Radial MRI findings and pathological changes were comparatively examined in the acetabular labrum of 11 hips of 11 patients, who underwent total hip arthroplasty for osteoarthritis due to acetabular dysplasia. Diffuse high signal pattern on the radial MR images corresponded to histological degeneration of the labrum. High signal pattern which was equivalent to the synovial fluid, showed an intralabral tear. In the obscure areas of MR images, severe impairment of the labrum such as rupture, detachment, and displacement were found.