Age / Sex : 30 / F

Synovial chondromatosis

Discussion

Findings: Radiograph, CT and MR images show extensive extrinsic bone erosion of left femur head and neck, medial wall of left acetabulum. CT images show low density conglomerated lesions with calcifications in the left hip joint. Coronal MR images show conglomerated lesions which are intermediate to high signal intensity on T2-weighted image and low signal intensity on T1-weighted image and subtle peripheral linear enhancement on post contrast T1-weighted image with fat saturation in left hip joint.

Differential Diagnosis:

Diagnosis: Synovial chondromatosis (patient underwent total hip replacement and pathologic finding revealed mature cartilaginous proliferation, consistent with synovial chondromatosis)

Discussion:  

Synovial chondromatosis has been divided into primary and secondary forms. Primary synovial chondromatosis was originally considered to represent chondroid metaplasia in the synovium of a joint with resultant formation of multiple intraarticular chondral bodies. However, current cytogenetic evaluation demonstrates that primary synovial chondromatosis is a benign neoplastic process. Secondary synovial chondromatosis is associated with joint abnormalities, such as mechanical or arthritic conditions, that cause intraarticular chondral bodies. The knee is the most frequently affected articulation. Other commonly involved joints are the hip, elbow, shoulder, and ankle. Radiographic features include multiple intraarticular chondral bodies with “ring-and-arc” chondroid mineralization and extrinsic erosion of bone on both sides of the joint. CT is the optimal radiologic modality to identify and characterize these calcified intraarticular fragments and extrinsic erosion of bone. MR imaging appearance of synovial chondromatosis is variable owing to the extent of mineralization and ossification of the chondral bodies. The noncalcified regions of hyaline cartilage neoplasia typically demonstrate high signal intensity on T2-weighted MR images because of the high water content of this tissue. The most frequent pattern was characterized as lobulated, homogeneous, intermediate, intraarticular signal intensity similar to that of muscle on T1-weighted images, with high signal intensity on T2-weighted images and focal areas of low signal intensity with all pulse sequences. The areas of signal void corresponded to regions of calcification on radiographs or CT scans. The contrast material enhancement of primary synovial chondromatosis is typical of hyaline cartilage neoplasms, which have a characteristic peripheral and septal pattern.

Treatment of choice for primary synovial chondromatosis is surgical synovectomy with removal of chondral fragments. Malignant transformation of primary synovial chondromatosis to chondrosarcoma is unusual and can be difficult to distinguish from benign disease, both pathologically and radiologically. However, multiple recurrences with development of marrow invasion should be viewed as representing malignant transformation.

References:

1.     Imaging of synovial chondromatosis with radiologic-pathologic correlation. Radiographics. 2007 Sep-Oct;27(5):1465-88.

2.     Synovial chondrosarcoma complicating synovial chondromatosis: report of a case and review of the literature. J Bone Joint Surg Am1987;69:1084–1088.

3.     Synovial chondromatosis. J Bone Joint Surg Br1988;70:807–811.