Imaging of Synovial Chondromatosis with Radiologic-Pathologic Correlation

Abstract

Primary synovial chondromatosis represents an uncommon benign neoplastic process with hyaline cartilage nodules in the subsynovial tissue of a joint, tendon sheath, or bursa. The nodules may enlarge and detach from the synovium. The knee, followed by the hip, in male adults are the most commonly involved sites and patient population. The pathologic appearance may simulate chondrosarcoma because of significant histologic atypia, and radiologic correlation to localize the process as synovially based is vital for correct diagnosis. Radiologic findings are frequently pathognomonic. Radiographs reveal multiple intraarticular calcifications (70%-95% of cases) of similar size and shape, distributed throughout the joint, with typical "ring-and-arc" chondroid mineralization. Extrinsic erosion of bone is seen in 20%-50% of cases. Computed tomography (CT) optimally depicts the calcified intraarticular fragments and extrinsic bone erosion. Magnetic resonance (MR) imaging findings are more variable, depending on the degree of mineralization, although the most common pattern (77% of cases) reveals low to intermediate signal intensity with T1-weighting and very high signal intensity with T2-weighting with hypointense calcifications. These signal intensity characteristics on MR images and low attenuation of the nonmineralized regions on CT scans reflect the high water content of the cartilaginous lesions. CT and MR imaging depict the extent of the synovial disease (particularly surrounding soft-tissue involvement) and lobular growth. Secondary synovial chondromatosis can be distinguished from primary disease both radiologically (underlying articular disease and fewer chondral bodies of variable size and shape) and pathologically (concentric rings of growth). Treatment of primary disease is surgical synovectomy with removal of chondral fragments; recurrence rates range from 3% to 23%. Malignant transformation to chondrosarcoma is unusual (5% of cases) and, although difficult to distinguish from benign disease, is suggested by multiple recurrences and marrow invasion. Recognizing the appearances of primary synovial chondromatosis, which reflect their underlying pathologic characteristics, improves radiologic assessment and is important to optimize patient management.

Synovial chondrosarcoma

“…The treatment often involves removal of loose bodies and subtotal synoviectomy, with or without joint replacement. Local recurrence is possible after incomplete synoviectomy, inadequate removal of loose bodies or diseased synovium at the time of initial surgery (28,32,43) and it is estimated to be 23% (53).…”

“…This risk ranges from 1% to 5% according different case series (28,36,53). As the clinical and radiological features are very similar between SC and SCH, their differentiation is often difficult and represents a diagnostic problem for orthopedic surgeon, radiologist and pathologist.…”

“…Because of the differences in treatment and prognosis between the two pathologies, attempts have been made to identify features that might aid in differentiating the two entities (36). However, many authors have found significant overlap with no definitive clinical or radiologic criteria of malignancy that can be used to distinguish SC from SCH (2,27,30,34,53). Clinically, both may present with pain, swelling and restricted movement of the affected joint with longstanding symptoms.…”

“…Clinically, both may present with pain, swelling and restricted movement of the affected joint with longstanding symptoms. Several authors speculate that a rapid deterioration of a longstanding clinical history or rapid recurrence after synoviectomy may indicate malignant transformation (31,34,53).…”

Orthopaedic Case of the Month: Ossified Calf Mass in a 32-year-old Woman

“…A soft tissue mass with circumscribed or peripheral calcification and a relative lucent center typically is seen on radiographs in the subacute phase, whereas the chronic phase often reveals a more densely ossified mass with a cortex surrounding central trabecular bone [1,10], unlike the small uniform ossifications observed in this case. Synovial chondromatosis is an uncommon benign condition, which involves the synovial lining of joints, tendon sheaths, or bursae [8,9]. It is divided into two main types: primary and secondary forms.…”