Pigmented villonodular synovitis (PVNS) - Orthopaedia

Tumor template based on A Clinical Guide to Primary Bone Tumors. Levesque et al.

Tumor biology and incidence

Pigmented villonodular synovitis (PVNS) is a condition of the synovial membrane that is characterized by the presence of inflammation and hemosiderin deposition in the synovium. Early descriptions focused on PVNS as a neoplastic process due to unrelenting growth pattern, capacity to erode surrounding boneand joint tissue, and high recurrence rate after resection. Later reports described the condition as an inflammatory process. Controversy still surrounds this area.

Two disease entities exist, the localized and diffuse forms. While both are virtually identical histologically, they vary significantly with respect to clinical presentation, prognosis, and response to treatment. Keeping this in mind, the two diseases probably exist along a continuum of a single disease process.

The estimated incidence of PVNS is 1.8 per million, with the diffuse form being the more common.

Etiology

The etiology of PVNS is still 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 the condition to trisomy 7 and have identified the presence of clonal DNA. In addition, literature exists that describes potential malignant transformations and metastasis.

Mechanical versus metabolic sources of trauma-

Mechanical trauma causing recurrent local hemorrhage into the joint is seen in hemophiliacs. These individuals suffer from progressive erosive arthropathies, with similar lobular synovitis and hemosiderin deposition. However, hemophiliacs lack the lipid laden histiocytes and giant cells that are considered classic indications of PVNS. Trauma has only been associated in less than one-third of the cases of PVNS. Altered local metabolic environment creates insults to the synovium leading to chronic inflammation.

Age

PVNS often appears in the third and fourth decades of life.

Gender

No gender preferences: 1:1 (M:F)

Physical Findings/Presentation

The clinical course of PVNS is notable for its slow and insidious onset of pain, swelling, and stiffness in the involved joint. When the disease involves the knee joint, the local form commonly has symptoms that mimic meniscal pathology. The diffuse form presents with global joint problems with poorly localized pain that has a greater intensity and associated swelling. The diffuse form can also manifest extra-articular extensions that encroach on major neurovascular structures - creating a mass effect.

Plain films

The majority of cases have no plain radiographic findings. As few as 30% (and less for knee pathology) present with radiographic findings. Therefore, for PVNS, plain radiography is a nonspecific and insensitive diagnostic tool.
When manifestations are present on plain radiograph, they commonly present with periarticular erosions,
with a thin rim of reactive bone. Reciprocal bony lesions on opposite sides of the joint, despite articular
preservation, are highly suggestive of PVNS but also can be seen in other conditions.
A late finding of joint space narrowing on plain radiograph indicates articular cartilage
loss, which can be difficult to distinguish from primary osteoarthritis.

Site

When the incidence of both forms of PVNS is taken into account, the joint most often affected is the knee (approximately 80%), with the hip, ankle, and shoulder being less commonly impacted. The disease usually is monoarticular. Considered separately, the localized form occurs most frequently in the fingers---in particular, in the volar aspect of the first 3 fingers. It is the most common soft-tissue tumor of the hand.
When considering only the knee, the local form targets the anterior compartment at the meniscocapsular junction (anterior horn of the medial meniscus). The diffuse form, while affecting the entire synovial surface, primarily affects the posterior compartment.

Size

Variable.

Soft Tissue Mass

Localized form takes on a pedunculated, lobular form localized to one area of the synovium, while the diffuse form involves most, if not all the joint synovium.

Bone scan

Increased uptake of TI-201 has been noted in PVNS. However, the use of bone scan is not commonly utilized.

CT Scan

Secondary to the presence of intracellular and extracellular hemosiderin, lesions have high attenuation and appear hyperdense on CT scans. In addition, affected synovium is hypervascular and generally enhances following administration of radiographic contrast. MRI is still the preferred imaging modality.

MRI

MRI can be highly sensitive and specific. It also can be helpful in determining the extent
of disease involvement and in distinguishing diffuse PVNS from local PVNS. Typical MRI findings for local PVNS include:
-          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 the localized form, with possible significant disability as a result. Local form has a more favorable prognosis with lower recurrence rates following treatment. In the diffuse from, progressive destructive changes continue to attack the joint and affect the articular surface, thereby leading to degenerative joint disease (necessitating total joint arthroplasty or arthrodesis). Early reports of recurrence rates after treatment of diffuse PVNS were as high as 46%. Improvements in surgical excision have decreased rates to 8%.

Pathology

Histological sections are characterized by lipid-laden macrophages, multinucleated giant cells, hemosiderin deposition, and stromal and fibroblast cell proliferation.

Diagnosis and treatment

Diagnosis made on a combination of clinical exam and radiologic/imaging findings. For early diagnosis, synovial fluid aspiration is a commonly reported technique. Brownish-stained bloody fluid is indicative of PVNS. However, this method lacks both specificity and sensitivity.

The principles behind the management of the local and diffuse forms are similar. The goal is to eradicate all abnormal synovial tissue, thus removing the source of pain and reducing the risk of joint destruction and recurrence.

Modalities of Treatment:

Combination of Arthroscopic Synovectomy with External beam radiation -
no significant advantage has been shown when compared to surgical synovectomy alone. However, significant complications have been reported including skin reactions, poor wound healing, joint stiffness, and sarcomatous transformation. Some reports demonstrate a local recurrence rate of 14%, comparable to rates recently reported for open total synovectomy. Therefore, this modality can be highly useful in managing refractory cases of PVNS or in those with extensive extra-articular involvement.

Combination Surgical Synovectomy with Intra-articular radiation -

studies demonstrate mixed results. In a series of 30 patients treated with adjuvant intra-articular radiation at a standard dose after combined open anterior and posterior synovectomy, the recurrence rate was 17% compared to 0% for open synovectomy alone. However, additional studies have 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. However, improper application of this technology has been associated with unacceptable recurrence rates in some instances (i.e. surgeon inexperience, or attempts to debride extensive, diffuse PVNS lesions). No clinical trials compare open with arthroscopic synovectomy for the treatment of localized PVNS. Some have found that extensive joint involvement and extra-articular spread may result after failed arthroscopic management. Currently recommended for local disease.

Open synovectomy (anterior and combined anterior/posterior) - may be required to access difficult areas affected by the diffuse form of the disease. Main drawback is significant postoperative stiffness, in up to 24% of the patients.

Combination of Open/Arthroscopic synovectomy - uses a combination of open posterior approach and arthroscopic anterior debridement. No additional benefits have been shown in the 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)