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Summary
  • PVNS is a locally aggressive neoplastic synovial disease (not a true neoplasm) characterized by joint effusions, expansion of the synovium, and bony erosions
  • PVNS most commonly involves the knee, and typically presents with joint pain and swelling. Diagnosis is typically confirmed with MRI.
  • Treatment usually consists of surgical synovectomy. 
Science
  • Epidemiology
    • incidence 
      • 9.2 per million per year in the United States
    • demographics
      • most commonly in adults age 30-40 but can occur at any age 
      • equal incidence in men and women
    • location
      • may occur locally (within a joint) or diffusely
      • localized (intra-articular or classic form) 
        • anterior knee is the most common site of involvement (80%) 
          • most commonly affects the patellofemoral compartment at the infrapatellar fat pad
        • knee > hip > ankle  > shoulder > elbow
      • diffuse (extra-articular extension)
        • behaves differently from localized
  • Pathophysiology
    • pathobiology
      • caused by an overexpression of CSF1 gene  
        • overexpression leads to clusters of aberrant cells creating focal areas of soft tissue hyperplasia in the synovial cells lining joints
      • a locally aggressive neoplastic synovial disease (not a true neoplasm) 
  • Genetics
    • mutations
      • locations of chromosome 1p13 in majority of cases
      • 5q33 chromosomal rearrangement 
  • Associated conditions
    • Giant Cell Tumor of Tendon Sheath  
      • also known as pigmented villonodular tumor of the tendon sheath (PVNTS)
  • Prognosis
    • PVNS is associated with a high rate of recurrence and accelerated degenerative changes of the knee ultimately requiring arthroplasty
      • TKA in patients with PVNS is associated with complication rates
Classification
 
Characteristic
Localized PVNS
Diffuse PVNS
Location
Knee > hip > ankle
Knee (75%)
Age
30-50y
<40y
Gender Male = Female Female =/> Male
Presentation
Painless, swollen joint, longstanding
Painful, swollen, tender, limited mobility
Radiograph
Osseous erosion from localized pressure
Degenerative changes on both sides of the joint
MRI
Well circumscribed soft tissue mass
Ill-defined (poorly circumscribed) soft tissue mass
Recurrence
8% after synovectomy
 30% after synovectomy
 
Presentation
  • History
    • 50% of patients will have a prior history of trauma to the area
  • Symptoms
    • common symptoms
      • insidious onsent of pain in affected joint
      • stiffness in the affected joint
      • swelling in the affected joint
    • recurrent atraumatic hemarthrosis
      • is hallmark of disorder
  • Physical exam
    • inspection
      • joint effusion
      • erythema
    • palpation
      • tenderness along joint line
    • motion
      • limited motion of affected joint
Imaging
  • Radiographs
    • recommended views
      • AP and lateral of affected joint
    • findings
      • soft tissue swelling
      • may show cystic erosion with sclerotic margins on both sides of the joint 
  • CT
    • indications
      • to evaluate for extent of cystic bone loss
    • findings
      • may show cystic erosions on both sides of the joint similar to radiographs  
  • MRI 
    • indications
      • most sensitive imaging study
      • provides excellent delineation of both intra-articular and extra-articular disease 
    • findings
      • reveals joint effusion, hemosiderin deposits, expansion of the synovium, and bony erosion 
      • low signal intensity on T1   
        • due to hemosiderin deposits
        • presence of fat signal (T1) within the lesion  
      • low signal intensity on T2  
      • "blooming artifact
        • signal loss on gradient-echo sequences 
        • because of iron in hemosiderin
      • extra-articular extension 
        • commonly see posterior extension outside of the knee joint of an intra-articular process
Studies
  • Labs
    • CRP and ESR
      • often normal despite signs of soft tissue swelling
  • Arthrocentesis
    • indication
      • recurrent hemarthrosis
    • findings
      • grossly bloody effusion 
  • Diagnostic arthroscopy
    • indications
      • gold standard for diagnosis 
      • synovial biopsy should be performed
    • findings
      • brownish or reddish inflamed synovium is typical of PVNS  
      • frond-like pattern of papillary projections
  • Histology
    • gross histology
      • shows a proliferative mass extending from the synovium  
    • low power
      • mononuclear stromal cells infiltrating the synovium 
      • highly vascular villi lined with plump hyperplastic synovial cells 
    • high power
      • hemosiderin stained multinucleated giant cells   
      • pigmented foam cells (lipid-laden histiocytes)
      • mitotic figures common
Differential
  • Synovial chondromatosis  
  • Hemophilia/hemarthrosis  
  • Rheumatoid arthritis 
  • Septic joints 
  • Other neoplasia
Treatment
  • Nonoperative
    • observation
      • indications
        • asymptomatic disease only
    • CSF-1 receptor antagonist (pexidartinib) 
      • indications
        • approved in 2019 for use in patients with extensive disease who are not likely to benefit from surgical intervention
  • Operative
    • partial synovectomy 
      • indications
        • local form of PVNS   
      • technique
        • if lesion is accessible from anterior knee, this is can be done arthroscopically
        • posterior or extra-articular lesions should be performed open
    • total synovectomy +/- external beam radiation  
      • indications
        • in grossly symptomatic and painful disease
      • technique
        • total synovectomy is classified as marginal excision 
        • techniques range from arthroscopic to fully open total synovectomy depending on extent and location of disease
      • outcomes
        • improved functional and range of motion outcomes with arthroscopic technique
        • frequent recurrence is common
          • mostly due to incomplete synovectomy
      • external beam irradiation
        • technique
          • 30-35Gy in 15 fractions, or 50Gy in 25 fractions
        • outcomes
          • when combined with total synovectomy, reduces rate of recurrence to 10-20%
    • total synovectomy and total joint arthroplasty
      • indications
        •  advanced disease with severe degenerative joint changes i knee, hip, and shoulder
    • total synovectomy and arthrodesis
      • indications
        • severe disease of the ankle
Techniques
  • CSF-1 receptor antagonist (pexidartinib)
    • technique
      • oral medication taken once daily for 24 weeks showed significant improvement of PVNS disease burden in ~40% of patients. 
    • complications
      • cholestatic hepatotoxicity was a noted side-effect of the drug
  • Arthroscopic synovectomy of knee for PVNS
    • approach 
      • routine arthroscopic portals for knee, ankle, and shoulder
    • technique
      • perform as thorough resection of synovium as possible through portals
      • can be challenging to access the posterior portions of the joint or extra-articular disease
  • Open posterior synovectomy of knee for PVNS
    • approach
      • posterior approach to the knee via transverse or S-shape incision across popliteal fossa 
      • approach between medial and lateral heads of gastrocnemius
      • retract neurovascular bundle to access posterior joint capsule
    • technique
      • disease is often seen posterior and extra-articular to the knee
      • complete posterior synovectomy and resection of extra-articular disease
    • complications
      • posterior approach to the knee places popliteal neurovascular bundle at risk
Complications
  • Recurrence 
    • incidence
      • recurrence is the most frequent complication for both intra-articular and extra-articular disease 
        • 30%-50% recurrence rate despite complete synovectomy
          • same rates for complete open vs open+arthroscopic
        • rates can be reduced with addition of external beam radiation
  • Joint destruction
    • moderate to severe joint deformity
    • treatment
      • may lead to the need for arthrodesis or amputation
  • Skin necrosis, radiation induced sarcoma
    • risk factors
      • radiation therapy

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