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  September 2008 Case of the Month 

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Compiled by:  Rakesh H. Patel, MD                                                                                                        

 

History:  42-year-old female with constant left hip pain since motor vehicle accident a few years ago


Exam: Left Hip MR Arthrogram  

Findings: On figures 1 (coronal T2 SPIR), 2 and 3 (coronal PD SPIR), and corresponding figures 4 and 5 (coronal T2 SPIR), a14 mm (anteroposterior) x 2 mm (depth) superior labral tear is present without evidence for labral detachment  

Images:

Figure 1
 Figure 2
Figure 3 
 Figure 4
Figure 5
  
                                                                                              

Diagnosis: Superior Labral Tear


Discussion: Acetabular labral tears are usually secondary to degeneration or traumatic injury in the 20 to 50 year-old age group. Soccer, hockey, golf, gymnastics, dancing, kickboxing, motor vehicle accidents, and developmental dysplasia of the hip are common causes. Hip pain results from a pivoting or twisting mechanism. Tear location depends on the cause. Sports-related labral tear sare usually anterosuperior (most common location) on the acetabular rim. In hip dysplasia or other disorders that disrupt articular congruence (e.g., slippedcapital femoral epiphysis), labral tear s tend to be superolateral on the acetabular rim, where the labrum is susceptibleto repeated impaction by the femoral head.  

 

Typically, the labra appear triangular in cross-section, but rounded and flattenedlabra as normal variants have been identified in 11% and 9% of nonarthrographicMR images, respectively.

 

MR Findings of Hip Labral Tears Include:

  • T1WI:   Intermediate linear or diffuse abnormal signal in the labrum, separation of the labrum, diastasis between acetabular articular cartilage and labral attachment, associated acetabular dysplasia.
  • T2WI:   Linear hyperintensity within hypointense labrum on coronal FS PD FSE or STIR images, hyperintense paralabral cyst (strong indicator of tear) +/- septations/lobulations, femoroacetabular impingement, hyperintense macerated labrum, labral displacement/bucket handle tears, hyperintense joint effusion.
  • T1C+ :   Intraarticular contrast fills the tear, promotes uplifting and separation of torn labrum from the acetabular articular cartilage.

Sagittaloblique images, which are prescribed parallel to the femoralneck from coronal images, best depict the anterosuperior acetabularlabrum, where sports-related labral tear s and associated capsulardefects usually occur. Axial T2-weighted images bestdepict intraarticular loose bodies. Chondral defects accompany approximately 30% of labral tear s and detachments.

The Czerny Classification(MR arthrography) of labral tears is as follows:

  • IA:   hyperintense intralabral signal only and presence of a perilabral sulcus
  • IB:   hyperintense intralabral signal only
  • IIA:   contrast extension into articular surface and perilabral sulcus present
  • IIB:   contrast extension into articular surface only
  • IIIA:   labral detachment with or without maintained triangular shape and sulcus
  • IIIB:   labral detachment with thickened labrum and labral hyperintensity, but without sulcus

Acetabular labral tear is a starting point for degenerativejoint disease. As the torn labral fragment becomes separatedfrom the acetabular rim, it loses its capacity for cushioningand protecting the adjacent articular cartilage. Loading forcesacross the joint are no longer distributed evenly over the entirecartilage surface. Repetitive impaction by the femoral headon the acetabulum eventually results in the development of chondraldefects and progressive osteoarthritis.

Treatment is conservative with activity modification (limiting flexion/internal rotation), anti-inflammatories, or steroid injections. Surgical treatment involves debridement and modified Bankart repair.


DDX

  • Degenerative Labrum (intralabral signal alteration only)
  • Normal Labral Attachment (fibrovascular bundles)
  • Femoroacetabular Impingement (subchondral erosions with or without labral tear)
  • Osteoarthritis                  
  • Sublabral Foramen or Normal Acetabular Cartilage Extension.
  • DDH (20% of symptomatic patients with a labral tear)
  • Normal Iliopsoas Tendon (represents a pitfall, and is located anterior to anterior labrum)

References:

1. Czerny C, Hofmann S, Neuhold A, et al. “Lesions of the acetabular labrum: accuracy of MR imaging and MR arthrography in detection and staging.” Radiology 1996; 200: 225-230
2. Stoller D, Tirman P., Bredella M. “Diagnostic Imaging : Orthopaedics.” Philadelphia, PA: Elsevier, 2004.
3. Fitzgerald RH. “Acetabular labrum tear s: diagnosis and management.” Clin Orthop 1995; 311:60-68.
4. Leucovet FE, Vande Berg BC, Malghem J, et al. “MR imaging of the acetabular labrum: Variations in 200 asymptomatic hip s.” AJR Am J Roentgenol 1996; 167: 1025-1028.
5. Steinbach L, Palmer W,   Schweitzer, M. “Special Focus Session MR Arthrography.“ Radiographics. 2002; 22: 1223-1246.
6. Petersilge, C. “ Chronic Adult Hip Pain: MR Arthrography of the Hip.”   Radiographics. 2000; 20: S43-S52.
7. Kaplan P , Helms C, Dussault R, Anderson M, Major N. “ Musculoskeletal MRI .”   WB Saunders, Philadelphia, PA, 2001.
8. Pomeranz S, et al: “ Gamuts and Pearls in MRI & Orthopedics .” MRI-EFI Publications, 1997





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