Pigmented villonodular synovitis (PVNS)

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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.


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