Diffuse Superior Labral

Fig. 11. MR arthrogram oblique sagittal technique. (A) Lines are drawn on a coronal MR ar-throgram image to determine the optimum oblique orientation for the oblique sagittal plane. (B) Normal oblique sagittal, TI, fat-suppressed MR arthrogram image.

Fig. 12. Anterior labral tear. Sagittal (A) and oblique sagittal (B) MR arthrogram images demonstrate a tear at the base of the anterior labrum (arrow), as well as a longitudinal tear extending into the substance of the anterior labrum.

into the extracapsular tissues. This mechanism is analogous to the formation of meniscal cysts at the knee and glenoid paralabral cysts at the shoulder. These cysts exhibit typically bright, fluid signal intensity on T2-weighted scans. A substantial proportion of these cysts will not fill with the injected gadolinium mixture on MR arthrography. Therefore, the cysts will remain of low signal intensity on T1-weighted, fat-suppressed scans (Fig. 15).

PREDISPOSING CONDITIONS FOR LABRAL INJURY

FAI represents an anatomic predisposition for abnormal contact between the anterior femoral neck and anterior or superior acetabulum. Clinically, these

Acetabular Stress Fracture Mri

Fig. 13. Twenty-three-year-old college hockey goalie with right hip pain. Coronal TI, fat-suppressed, post-arthrogram MR image demonstrates a torn anterior superior labrum. Contrast tracks through the tear (arrow).

Degeneration The Labrum
Fig. 14. Anterior labral degeneration and tear. Sagittal TI, fat-suppressed, post-MR arthro-gram image demonstrates an enlarged, degenerated, amorphous appearing anterior labrum (arrow).

patients may present initially with groin pain exacerbated by athletic activity or prolonged sitting [4]. Some investigators believe that FAI is an important cause of premature osteoarthritis of the hip [4-6]. FAI may be divided into two types: cam and pincer. In cam-type impingement, there is abnormal prominence to the anterolateral femoral head-neck junction, predisposing to impaction upon the anterior acetabular rim with flexion and internal rotation (Fig. 16). Cam-type impingement is felt to be of greatest significance in the

Anterolateral Stress Fracture
Fig. 15. Paralabral cyst. Coronal T2 (A) and coronal T1, fat-suppressed (B) images post-arthrography demonstrate paralabral cyst formation (arrows) adjacent to the labrum. There is also an anterior superior labral tear and cartilage loss secondary to degenerative joint disease (arrow).
Paralabral Cyst
Fig. 16. FAI. Anteroposterior radiograph of the hips illustrates an osseous prominence along the lateral aspect of the femoral head-neck junction (arrow). This may predispose to cam-type impingement.

young athletic population. Previous slipped capital femoral epiphysis is the prototypical anatomic configuration predisposing to cam-type impingement, though in most cases the head-neck offset is more subtle. Pincer-type impingement reflects abnormally ''deepening'' of the anterior acetabular fossa, such as with acetabular retroversion or protrusion. This results in impaction of the anterior lip of the acetabulum on the femoral neck with flexion. Pincer-type impingement is typically seen in an older, nonathletic population [4,5,41].

In theory, abnormal femoral or acetabular morphologies leading to impingement result in early labral and chondral injury. Anterosuperior labral degeneration and tears have been reported by Beck and colleagues [5] as being characteristic of cam-type impingement. The labrum may be reduced in size. In addition, premature chondral injury is characteristic, typically adjacent to

Herniation Pit Mri Coronal

Fig. 17. Herniation pit, FAI. Following arthrography, coronal TI, fat-suppressed (A) and axial proton density, fat-suppressed (B) images demonstrate anterior superior labral tear (arrow). Note the lack of labral enlargement with FAI. In (B), there is an anterior femoral head herniation pit that may be associated with FAI.

Fig. 17. Herniation pit, FAI. Following arthrography, coronal TI, fat-suppressed (A) and axial proton density, fat-suppressed (B) images demonstrate anterior superior labral tear (arrow). Note the lack of labral enlargement with FAI. In (B), there is an anterior femoral head herniation pit that may be associated with FAI.

Labrum Scan

Fig. 18. DDH—MR arthrography. (A) Radiograph obtained at the completion of the arthro-gram and gadolinium injection. The image is obtained with gentle leg traction. The superior labrum is enlarged and elongated (arrow). The femoral head is uncovered laterally by the bony acetabulum. (B) Sagittal TI, fat-suppressed image. Large degenerative cyst (arrow) filled with gadolinium. There is osteoarthritis of the hip joint. The anterior labrum is swollen, markedly degenerated and amorphous (arrowhead).

Fig. 18. DDH—MR arthrography. (A) Radiograph obtained at the completion of the arthro-gram and gadolinium injection. The image is obtained with gentle leg traction. The superior labrum is enlarged and elongated (arrow). The femoral head is uncovered laterally by the bony acetabulum. (B) Sagittal TI, fat-suppressed image. Large degenerative cyst (arrow) filled with gadolinium. There is osteoarthritis of the hip joint. The anterior labrum is swollen, markedly degenerated and amorphous (arrowhead).

the anterosuperior labrum with cam-type impingement. Chondral injury at the base of the labrum may, in fact, precede a labral tear [5,41]. MR arthrography is invaluable in depicting both labral and chondral abnormalities [32,34,35,43]. Fibro-osseous defects in the anterior femoral neck, so- called ''herniation pits,'' have also been described in association with FAI (Fig. 17) [32,44]. Some herni-ation pits manifest adjacent bone marrow edema.

Ossific Densities Lateral Aspect Hip

Fig. 19. Severe DDH—MR arthrography. (A) Coronal T1, fat-suppressed MR arthrogram reveals osteoarthritis of the hip joint with severe cartilage loss (arrow) as well as a degenerated superior labrum. (B) Oblique sagittal TI, fat-suppressed image illustrates a degenerated and hypertrophied anterior labrum with a large paralabral cyst (arrow). Note the anteriorly uncovered femoral head.

Fig. 19. Severe DDH—MR arthrography. (A) Coronal T1, fat-suppressed MR arthrogram reveals osteoarthritis of the hip joint with severe cartilage loss (arrow) as well as a degenerated superior labrum. (B) Oblique sagittal TI, fat-suppressed image illustrates a degenerated and hypertrophied anterior labrum with a large paralabral cyst (arrow). Note the anteriorly uncovered femoral head.

The imaging findings in DDH differ significantly from those seen with FAI. With decreased superolateral or anterior acetabular coverage of the femoral head, the labrum may enlarge significantly, with subsequent degeneration and tear (Fig. 18) [7]. Theoretically, this hypertrophied, ''floppy''-appearing labrum is compensating for the deficient acetabular coverage. Anterior and or superior labral pathology is typically encountered. Depending on the severity of the dysplasia and intensity of athletic activity, premature chondral injury is often evident, again most prominent in the superolateral or anterior aspects of the joint (Fig. 19). In the authors' experience, many athletes who have no history of DDH detected in childhood present with hip pain and mild to moderate DDH, first recognized as adults. Many present with significant labral or chondral abnormalities.

Hip Labral Abnormalities

Fig. 20. Twenty-four-year-old downhill ski racer with right hip pain several months after an injury. (A) Coronal T1, fat-suppressed MR arthrogram. There is an osteochondral injury involving a large portion of the right femoral head with delaminated articular cartilage (arrow). (B) Oblique sagittal TI, fat-suppressed image demonstrates contrast undercutting the articular cartilage (arrow), indicating an unstable fragment. (C) Image obtained at hip arthroscopy showing a large intra-articular loose chondral fragment.

ACUTE CHONDRAL INJURY

Acute chondral and osteochondral injuries of the femoral head have been reported in athletes. They may result from impaction injury, traumatic subluxation, or shearing injury, and may accompany fractures of the acetabulum or hip dislocation [45,46]. Patients who have chronic, persistent pain following hip injury, with negative or equivocal radiographic findings, may benefit from evaluation with MRI or MR arthrography. Post-traumatic osteonecrosis may be readily diagnosed with MRI [47]. When chondral injury is suspected, MR arthrography is preferred. With cartilage flap tear, there is undercutting of the chondral surface with fluid/gadolinium on MR arthrography (Fig. 20). The detection of a discrete chondral or osteochondral defect should prompt a thorough search for a displaced intracapsular body. This manifests as a low signal intensity filling defect within the fluid-filled joint. Ossific bodies may be isointense to bone

Hip Joint Multi Planar

Fig. 21. Twenty-two-year-old college football defensive lineman, hip injured during a game. (A) Axial CT scan demonstrates an avulsed fracture fragment off the posterior rim of the acetabulum (arrow). (B). Sagittal TI MR arthrogram reveals thinning of articular cartilage (arrow) in the right hip joint caused by chondrolysis. (C) Coronal T2 MR arthrogram demonstrates medial joint space loose bodies (arrow).

Fig. 21. Twenty-two-year-old college football defensive lineman, hip injured during a game. (A) Axial CT scan demonstrates an avulsed fracture fragment off the posterior rim of the acetabulum (arrow). (B). Sagittal TI MR arthrogram reveals thinning of articular cartilage (arrow) in the right hip joint caused by chondrolysis. (C) Coronal T2 MR arthrogram demonstrates medial joint space loose bodies (arrow).

marrow. Progressive joint space narrowing in athletes who have traumatic hip subluxation, occurring in the months immediately following trauma, may indicate post-traumatic chondrolysis (Fig. 21) [46].

MONARTICULAR SYNOVIAL PROLIFERATION

Although not specific to athletes, two conditions, synovial osteochondromatosis and pigmented villonodular synovitis (PVNS), warrant brief review because of their predilection for younger individuals and their unique appearances on imaging studies.

In synovial chondromatosis, there is synovial metaplasia with formation of cartilage. Secondary ossification may occur, and these cartilaginous and osteo-cartilaginous bodies often become detached into the joint capsule. Large joints such as the hip and knee are frequently involved [48]. Erosions of the femoral neck may occur. Ossified bodies are visible on radiograph and CT. Nonossified and osseous bodies are readily visualized on MR arthography as multiple filling defects within the distended capsule (Fig. 22), and there may be extra-articular spread into adjacent bursae [49]. Multiplanar depiction of capsular anatomy and precise localization of the bodies are valuable to the surgeon, both preop-eratively and in the follow-up of treated disease.

Pigmented villonodular synovitis (PVNS) represents a synovial proliferative process that may be localized to joints, tendon sheaths, or adjacent soft tissues, or may be diffuse, typically within the capsule of large joints such as the knee or hip. Hemosiderin deposition within synovium may result in hemorrhagic effusions. The presence of hemosiderin-laden tissue results in a characteristic appearance on MRI, with low or very low signal intensity on many sequences. Femoral neck erosions may occur, though there is typically no mineralization associated with this condition, making early diagnosis on radiographs difficult (Fig. 23) [9,50-52].

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Responses

  • tuulikki
    What is diffuse labral tearing and reoption?
    3 years ago
  • mungo labingi
    What is a diffuse shoulder labral tear?
    2 years ago
  • Libera
    What is diffuse degenerative tearing of shoulder labrum?
    2 years ago
  • anke
    What is extensive labral degeneration?
    4 months ago

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