187 CLINICAL ORTHOPAEDICS AND RELATED RESEARCH Number 388, pp. 187–199 © 2001 Lippincott Williams & Wilkins, Inc. Pigmented villonodular synovitis affecting the hip is rare. Seven new patients are presented and 117 cases from the literature are reviewed. Among the new patients, two refused treatment; in one patient, severe bone loss was observed af- ter a radiographic followup of 21 years; the sec- ond patient showed no radiographic changes 2 years after diagnosis. One patient underwent a synovectomy and had a recurrence 9 years later, requiring a total hip replacement. The remain- ing four patients underwent synovectomy and primary total hip replacement with no recur- rences detected after an average followup of 13 years (range, 2–23 years). Among 117 cases pub- lished, 62 patients (53%) did not have enough information for analysis. A metaanalysis using the remaining 55 patients was done. In nine pa- tients (16%; nine of 55) the diagnosis was made with a preoperative biopsy. Treatment consisted of synovectomy in 26 patients (47%; 26 of 55), arthroplasty in 24 (43%; 24 of 55), arthrodesis in two (4%; two of 55), and hindquarter ampu- tation in a patient misdiagnosed as having sy- novial sarcoma (2%; one of 55). Two patients (4%; two of 55) were not treated. Ten patients had a recurrence (19%; 10 of 53); nine in the synovectomy group (35%; nine of 26) and one in the joint replacement group (4%; one of 24). Synovectomy is recommended for patients with preserved articular cartilage and total hip re- placement is recommended for patients with secondary osteoarthritis. Removal of all macro- scopic tumors including careful curetting of the osteolytic lesions should be done as they may constitute a source of recurrence. Pigmented villonodular synovitis is an un- common benign neoplastic process of the sy- novial membrane presumed to be of histiocytic origin. 19 In one hospital involved in this study, pigmented villonodular synovitis was diag- nosed histologically in 250 patients from 1994 to 1999; the hip was affected in only nine pa- tients (3.6%; nine of 250) with five patients having incidental findings. 54 Jaffe et al 27 proposed the name pigmented villonodular synovitis in 1941 and described two forms: small, peduncular lesions (localized nodular synovitis), and lesions with diffuse in- Pigmented Villonodular Synovitis of the Hip 2- to 23-Year Followup Study Alejandro González Della Valle, MD*; Francisco Piccaluga, MD*; Hollis G. Potter, MD**; Eduardo A. Salvati, MD**; and Rodolfo Pusso, MD* From the *Instituto de Ortopedia y Traumatología, Car- los E. Ottolenghi Hospital Italiano de Buenos Aires, Ar- gentina; and **Cornell Medical College and Hospital for Special Surgery, New York, NY. Reprint requests to Alejandro González Della Valle, MD, Instituto de Ortopedia y Traumatología, Carlos E. Ot- tolenghi Hospital Italiano de Buenos Aires, 4215 Potosi Street, Buenos Aires, C1199ACK. Argentina. Received: January 28, 2000. Revised: May 19, 2000; October 5, 2000. Accepted: October 26, 2000.