Age / Sex : 77 / F

Chief complaint : Right elbow pain, intermittent locking

1) What is your impression?

Two weeks later, you can see the final diagnosis with a brief discussion of this case.

* Send Application Answers to Jae Hyuck Yi, MD ([email protected])
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Courtesy : 문승규 (Sung Gyu Moon), 건국대학교병원 (Konkuk University Medical Center)

Osteochondritis dissecans involving the trochlea

Discussion

Findings:

Figure 1. Elbow radiograph shows focal concavity at the lateral articular surface of the trochlea. This mimics a pseudointercondylar notch and can be easily overlooked as a normal finding.

Figure 2. Proton-density coronal MR image shows a subchondral defect within the lateral aspect of the trochlea. The abnormal cartilage signal is noted within the subchondral defect and superficial to the defect. Some normal fatty marrow signal is noted between the cartilage signal.

Figure 3. Fat-saturated T2-W sagittal MR image shows small amount of joint effusion and the osteochondral lesion in the trochlea, covered by intact cartilage.

Figure 4-5. Coronal and sagittal reconstruction of CT arthrogram demonstrates a well-circumscribed round defect in the trochlea. A small osseous fragment is seen within this defect. The osteochondral lesion is in continuity with host bone, covered by intact cartilage without contrast interposition. Sagittal image shows subtle flattening of the articular surface.

Differential diagnosis:

The differential diagnosis of the conditions affecting the trochlea should include Hageman disease, which is similar in pathophysiology to Panner disease and Legg-Calvé-Perthes disease. In contrast to OCD that primarily involves the subchondral bone, this entity affects the entire epiphysis, leading to sclerosis, condensation or collapse. Other entities in the differential are chondroblastoma, synovial osteochondromatosis, ossification variations and epiphyseal dysplasia. Epiphyseal dysplasia is a bilateral condition that affects the elbow and other joints in near-symmetrical fashion, whereas chondroblastoma presents as a radiolucent defect, sometimes with stippled calcification within the epiphysis. Synovial osteochondromatosis generally presents as multiple loose bodies within the joint cavity.

Diagnosis: Osteochondritis dissecans involving the trochlea

Discussion:

OCD is a condition in which the articular epiphyses fail as a result of compression, resulting in separation of the articular cartilage and the subchondral bone. Both trauma and ischemia have been implicated as the cause. Although major trauma is thought to be the initial provoking event, such history is identified in only a minority of cases. Repetitive microtrauma to a poorly vascularized bone is more likely the cause in the majority of cases.

OCD of the elbow is common with activities such as pitching or gymnastics that have frequent overuse of the elbow, characterized by repeated valgus stress, which in turn causes microtrauma or ischemia to the elbow.

Although the trochlea is an infrequent location, it is important to remember that OCD can occur there. The OCD lesions consistently occurred in the posterior inferior aspect of the lateral trochlea corresponding to a watershed zone of diminished vascularity due to the non-overlapping blood supply of the trochlea.

Plain radiography should be the first imaging study obtained in all cases. It is necessary to recognize that focal concavity at the articular surface is not normal and might represent a pseudointercondylar notch sign.

MRI can allow assessment of very early lesions and hence it has been established as the most sensitive and reliable means for assessing OCD. MRI can also help define the size, exact location and stability of the OCD. Unstable lesions generally have a peripheral rim of increased T2/STIR signal intensity around the lesion or an underlying fluid-filled cyst. In contrast to this, stable lesions demonstrate peripheral low-signal intensity on T2-W images.

The prognosis and treatment often depends on the stage at which OCD is detected and the stability and location of the lesion. Earlier stages or stable lesions can be treated conservatively, including activity modifications and muscle strengthening exercise. However, later stages, unstable lesions or stable lesions with failed conservative therapy often require surgical intervention, such as loose body extraction, debridement of the OCD lesion and drilling or microfracture of the adjacent subchondral bone.

References:

1. Pruthi S, Parnell SE, Thapa MM. Pseudointercondylar notch sign: manifestation of osteochondritis dissecans of the trochlea. Pediatr Radiol. 2009 Feb;39(2):180-3. Epub 2008 Nov 15.

 2. Marshall KW, Marshall DL, Busch MT, Williams JP. Osteochondral lesions of the humeral trochlea in the young athlete. Skeletal Radiol. 2009 May;38(5):479-91. Epub 2009 Feb 17.