Tumor biology and incidence
- Condition of synovial membrane
- Characterized by presence of inflammation and hemosiderin deposition in synovium
- Controversy: Is PVNS a neoplastic or an inflammatory process?
- Traditionally described as neoplastic process due to unrelenting growth pattern, capacity to erode surrounding boneand joint tissue, and high recurrence rate after resection
- Newer reports consider PVNS to be an inflammatory process
- Two disease entities: localized form and diffuse form
- Virtually identical histologically
- Vary significantly in clinical presentation, prognosis, and response to treatment
- Probably co-exist along a continuum of a single disease process
- Usually monoarticular
- Estimated incidence of PVNS is 1.8 cases/million; diffuse form is more common
- Etiology unknown
- Inflammatory versus neoplastic origin
- Histologic samples have tested positive for markers of chronic inflammation, while excess iron has been seen to transform synoviocytes and fibroblasts into cells with macrophage-like characteristics
- Reports have linked PVNS to trisomy 7 and have identified presence of clonal DNA
- Literature describes potential malignant transformations and metastasis
- Mechanical versus metabolic sources of trauma
- Mechanical trauma causing recurrent local hemorrhage into joint seen in hemophiliacs
- Suffer from progressive erosive arthropathies, with similar lobular synovitis and hemosiderin deposition
- Hemophiliacs, however, lack lipid-laden histiocytes and giant cells considered classic indications of PVNS
- Trauma associated with in less than one-third of cases of PVNS
- Altered local metabolic environment creates insults to the synovium leading to chronic inflammation.
Age
Often appears in third and fourth decades of life
Gender
M:F = 1:1
Presentation/physical findings
- Slow, insidious onset of pain, swelling, and stiffness in involved joint
- If knee joint involved, local form commonly has symptoms that mimic meniscal pathology
- Diffuse form presents with global joint problems; poorly localized pain with a greater intensity and associated swelling
- Can also manifest extra-articular extensions that encroach on major neurovascular structures, creating a mass effect.
Plain films
- Plain radiographs nonspecific and insensitive as a diagnostic tool; 30% or fewer patients present with radiographic findings
- If findings are present on plain radiographs, generally appear as periarticular erosions, with a thin rim of reactive bone
- Reciprocal bony lesions on opposite sides of the joint, despite articular preservation, highly suggestive of PVNS, but can be seen in other conditions
- Late finding of joint space narrowing on plain radiograph indicates articular cartilage loss; can be difficult to distinguish from primary osteoarthritis
Site
- Combined, the two forms of PVNS most often affect the knee (approximately 80%); the hip, ankle, and shoulder are less commonly affected
- Local form targets knee's anterior compartment at meniscocapsular junction (anterior horn of the medial meniscus)
- Diffuse form, while affecting knee's entire synovial surface, primarily affects posterior compartment
- Considered separately, the localized form occurs most frequently in fingers -- especially volar aspect of first 3 fingers
- Most common soft tissue tumor of the hand
Size
Variable
Soft tissue mass
- Localized form pedunculated and lobular; localized to one area of synovium
- Diffuse form involves most, if not all, of the joint's synovium
Bone scan
Increased uptake of TI-201, although bone scan not commonly used in PVNS
CT scan
- Lesions have high attenuation and appear hyperdense secondary to presence of intracellular and extracellular hemosiderin
- Affected synovium hypervascular and generally enhances following administration of radiographic contrast
MRI
- Preferred imaging modality; can be highly sensitive and specific
- Useful in determining extent of disease involvement and in distinguishing diffuse PVNS from local PVNS
- Typical MRI findings for local PVNS:
- Periarticular or synovial nodular mass with varying degrees of bone erosion
- Sporadic or extensive low signal on T1 and T2 (secondary to high hemosiderin content)
- Joint effusion
- "Dark on dark" on T1- and T2-weighted images, but early inflammatory lesions with less hemosiderin may have large amounts of high signal on T2 sequences
- High signal on fat-suppressed images (hemosiderin cannot be seen)
- Hemosiderin seen on fast field echo sequences
- Lesions enhance with contrast
Differential diagnosis
- Synovial osteochondromatosis
- Synovial hemangioma
- Hemochromatosis
- Hemophiliac arthropathy
- Secondary osteoarthritis
- Amyloid arthropathy
- Gout
- Tuberculosis
Natural history
- Continued chronic pain in localized form, possibly resulting in significant disability
- Local form has more favorable prognosis with lower recurrence rate following treatment
- In diffuse from, progressive destructive changes continue to attack joint and affect articular surface, leading to degenerative joint disease (necessitating total joint arthroplasty or arthrodesis)
- 8% recurrence rate following surgical excision in diffuse form
Pathology
Histological sections characterized by lipid-laden macrophages, multinucleated giant cells, hemosiderin deposition, and stromal and fibroblast cell proliferation
Diagnosis and treatment
- Diagnosis made on combination of clinical exam and radiologic/imaging findings
- Synovial fluid aspiration commonly used for early diagnosis; brownish-stained bloody fluid indicative of PVNS
- Method lacks specificity and sensitivity
- Treatment goal: Eradicate all abnormal synovial tissue, removing source of pain and reducing risk of joint destruction and recurrence
- Treatment modalities
- Arthroscopic synovectomy with external beam radiation
- No significant advantage compared with surgical synovectomy alone
- Significant complications have been reported: skin reactions, poor wound healing, joint stiffness, sarcomatous transformation
- Local recurrence rate of 14%, comparable to rate for open total synovectomy
- Modality can be highly useful in managing refractory cases of PVNS or in those with extensive extra-articular involvement
- Surgical synovectomy with intra-articular radiation
- Mixed results in the literature
- Series of 30 patients treated with adjuvant intra-articular radiation at a standard dose after combined open anterior and posterior synovectomy: recurrence rate 17%, compared to 0% for open synovectomy alone
- Other studies demonstrated eradication of residual disease following intra-articular radiation and MRI follow-up
- Arthroscopic synovectomy
- Associated with better functional results and lower rates of postoperative stiffness than open techniques
- Improper application of technology, however, associated with unacceptable recurrence rates in some instances (ie, surgeon inexperience or attempts to debride extensive, diffuse PVNS lesions)
- No clinical trials compare open with arthroscopic synovectomy for treatment of localized PVNS
- Extensive joint involvement and extra-articular spread may result after failed arthroscopic management
- Currently recommended for local disease only
- Open synovectomy (anterior and combined anterior/posterior)
- May be required to access difficult areas affected by diffuse form of disease
- Main drawback: significant postoperative stiffness, up to 24% of the patients.
- Combination open/arthroscopic synovectomy
- Uses combination of open posterior approach and arthroscopic anterior debridement
- No additional benefits shown in literature
Complications
Osteoarthritis secondary to articular cartilaginous erosions, necessitating total joint arthroplasty (few reports on long-term outcomes in those with total joint arthroplasty and concomitant PVNS)
Recommended reading
Tyler WK, Vidal AF, Williams RJ, Healey JH. Pigmented villonodular synovitis. J Am Acad. Ortho Surg 2006;14(6):376-85.