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Pigmented villonodular synovitis: A rare problem and a challenging diagnosis
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Douglas W. Jackson, MD, asks 4 questions of Joshua S. Dines, MD, about the history of PVNS.
While it is an uncommon finding, if you do enough surgery on joints, one day you will come across pigmented villonodular synovitis (PVNS). With the advent of MRI, the diagnosis and/or occurrence of this entity is usually known in advance. However, occasionally it occurs as a localized manifestation (LPVNS) which can be an unexpected finding. For this interview I asked Joshua S. Dines, MD, to share his insights into LPVNS from his work on the Sports Medicine and Shoulder Service, at The Hospital for Special Surgery in New York, N.Y.
Douglas W. Jackson, MD
Chief Medical Editor
Douglas W. Jackson, MD: What is the incidence of LPVNS of the knee and how it is characterized?
Joshua S. Dines, MD: PVNS is a proliferative condition of the synovium that most often affects the knee. There are two forms described in the literature: LPVNS and diffuse (DPVNS). It is debatable whether LPVNS and DPVNS are discrete pathologic entities or similar processes at different ends of the same disease spectrum. Either way, it is important to distinguish between the two, as the treatment and prognosis for each process differs.
Studies estimate the annual incidence of PVNS to be about 1.8 patients per one million people. Previous reports indicated that the diffuse variant was more common; however, in our recent report in Arthroscopy, we found a higher incidence of LPVNS.
The etiology is largely unknown, though there is some evidence to suggest that PVNS is a neoplastic process. Histologically, LPVNS lesions are characterized by a proliferation of polyhedral synovial-like cells with multinucleated giant cells, hemosiderin deposition, and occasional foam cells. At surgery, the nodule appears as an isolated circumscribed or pedunculated lesion arising from the synovium.
Jackson: What are some of the findings and symptoms that may raise consideration in the differential diagnosis of internal derangements? Is imaging helpful?
Dines: Due to the variety of ways in which LPVNS presents, diagnosing the condition is often difficult. Pain is the most common symptom, though it is frequently mild enough that patients tolerate it for years before seeking treatment. In our series, more than half the patients presented with an effusion. Other presenting signs and symptoms include:
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- joint line tenderness;
- decreased range of motion; and
- the presence of a palpable mass, and/or mechanical symptoms (locking, catching, giving way).
It is the presence of mechanical symptoms that lead to the presumptive diagnosis of internal derangement in the majority of cases. The differential diagnosis also includes displaced meniscal tear, loose body, osteochondral fragment, and soft-tissue mass. In many cases, preoperative imaging is helpful to make the definitive diagnosis.
Radiographs of the knee rarely reveal any abnormalities in cases of LPVNS. That being said, normal radiographs can help rule out pathologies, such as osteoarthritis, rheumatoid arthritis and gout. Occasionally, shadows from the LPVNS mass can be seen on X-ray. Magnetic resonance imaging is much more sensitive for diagnosing LPVNS. It has a characteristic appearance on MRI with focal hypointense areas on both T1- and T2-weighted images. Historically, MR was not very specific for LPVNS lesions; however new sequences have increased the specificity. We do routinely use it in almost every case of presumed internal derangement.
Jackson: What is the natural history of PVNS?
Dines: PVNS often affects people during their third or fourth decades of life. Symptoms are often intermittent and slowly progressive. Several studies show that patients may wait years from the onset of symptoms to the time they present for treatment. If the localized variant remains untreated, symptoms can continue to affect activity and function. Perhaps because the condition is so easily treated, there are no long-term studies that follow patients with untreated LPVNS. Several studies have confirmed that marginal excision of the localized lesions, which can be performed arthroscopically, results in a 0% recurrence rate. A concern does exist, however, regarding the development of secondary arthritis in patients treated for PVNS.
A recent study by Vastel et al. in 2005 showed that complete synovectomy for treatment of PVNS of the hip successfully prevented recurrence, but arthritis did develop in all patients. It is unknown if a similar natural history exists in the knee, but it seems reasonable that patients with such lesions be made aware of the potential for arthritis.
Jackson: What are some of the surgical prognostic factors and approaches that can influence outcomes?
Dines: Confirmation that the lesion is actually localized and not diffuse is the most important prognostic factor. As mentioned, the recurrence rate for documented LPVNS lesions is 0%. Diffuse lesions often require more extensive surgeries, and recurrence rates approaching 50% have been reported.
For LPVNS, arthroscopic partial synovectomy is our preferred surgical approach. The key to successful treatment hinges upon complete debridement of the lesion with a cuff of normal-appearing synovium. Most commonly, LPVNS lesions arise from the synovium adjacent to the anterior horn of the medial meniscus. This is easily accessible arthroscopically using standard anterolateral and anteromedial portals. Surgeons must be aware, however, that occasionally the nodules will be located in the posterior compartment of the knee, which may require the use of a 70° arthroscope and/or accessory portals. Successful outcomes have also been reported with open resection; so if a surgeon is not comfortable with posterior compartment arthroscopy, making an arthrotomy to perform the partial synovectomy is a viable alternative.
In terms of functional outcome, patients tend to do well. In our series, all 10 patients treated with arthroscopic excision had good to excellent results clinically. On the Lysholm knee scoring scale, all but one patient had an excellent outcome. No patient developed recurrent symptoms or required subsequent surgery on their knee. In sum, early arthroscopic treatment of documented LPVNS lesions results in reliably good outcomes.
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Image: Dines JS. |
For more information:
- Joshua S. Dines, MD, can be reached at Hospital for Special Surgery, 535 East 70th St., New York, NY 10021; e-mail: dinesj@hss.edu.
References:
- Dines JS, DeBerardino TM, Wells JL, et al. Long-term follow-up of surgically treated localized pigmented villonodular synovitis of the knee. Arthroscopy. 2007;23(9):930-937.
- Vastel L, Lambert P, De Pinieux G, et al. Surgical treatment of pigmented villonodular synovitis of the hip. J Bone Joint Surg (Am). 2005;87(5):1019-1024.