Pigmented Villonodular Synovitis of the Hip: A Systematic Review
Pigmented villonodular synovitis is a rare proliferative condition of the synovium that affects large joints. The primary treatment options are synovectomy and a combination of synovectomy and arthroplasty.
We performed a systematic review of the literature, excluding all nonclinical and review articles with follow-up of less than 2 years. Primary outcomes reported were disease recurrence, symptom progression, and revision surgery. Student t tests were used to compare outcomes after synovectomy with outcomes after synovectomy combined with arthroplasty. Twenty-one studies (82 patients) were included. All represented level IV or V evidence. Fifty-one patients (59.3%) were female. Mean (SD) age was 33.2 (12.6) years. Synovectomy alone was performed in 45 patients (54.9%), and synovectomy with arthroplasty was performed in 37 patients (45.1%). Mean (SD) follow-up was 8.4 (5.9) years. The groups’ revision rates were not significantly different (26.2% vs 24.3%; P = .17). Mean (SD) time to revision was significantly (P = .02) longer in the synovectomy-with-arthroplasty group, 11.8 (4.5) years, than in the synovectomy-only group, 6.5 (3.9) years. Study results showed revisions are common after surgery for hip pigmented villonodular synovitis, affecting 1 in 4 patients regardless of which surgery they have—either synovectomy alone or synovectomy combined with arthroplasty. Revision is required sooner in synovectomy-only patients than in patients who also undergo arthroplasty.
The high rates of bony involvement, joint destruction, and recurrence after synovectomy have prompted many surgeons to turn to arthroplasty. González Della Valle and colleagues18 theorized that joint space narrowing is more common in hip PVNS because of the poor distensibility of the hip capsule compared with that of the knee and other joints. In turn, bony lesions and arthritis present earlier in hip PVNS.14 Yoo and colleagues14 found a statistically significant increase in Harris Hip Scale (HHS) scores and a high rate of return to athletic activity after THA for PVNS. However, they also reported revisions for component loosening and osteolysis in 2 of 8 patients and periprosthetic osteolysis without loosening in another 2 patients. Vastel and colleagues16 similarly reported aseptic loosening of the acetabular component in half their patient cohort. No studies have determined which condition—PVNS recurrence or debris-related osteolysis—causes the accelerated loosening in this demographic.
Byrd and colleagues1 recently described use of hip arthroscopy in the treatment of PVNS. In a cohort of 13 patients, they found statistically significant improvements in HHS scores, no postoperative complications, and only 1 revision (THA 6 years after surgery). Although there is a prevailing perception that nodular (vs diffuse) PVNS is more appropriately treated with arthroscopic excision, no studies have provided data on this effect, and Byrd and colleagues1 in fact showed a trend of slightly better outcomes in diffuse cases than in nodular cases. The main challenges of hip arthroscopy are the steep learning curve and adequate exposure. Recent innovations include additional arthroscopic portals and enlarged T-capsulotomy, which may be contributing to decreased complication rates in hip arthroscopy in general.35
The limitations of this systematic review were largely imposed by the studies analyzed. The primary limitation was the relative paucity of clinical and radiographic data on hip PVNS. To our knowledge, studies on the treatment of hip PVNS have reported evidence levels no higher than IV. In addition, the studies we reviewed often had only 1 or 2 patient cases satisfying our inclusion criteria. For this reason, we included case reports, which further lowered the level of evidence of studies used. There were no consistently reported physical examination, survey, or radiographic findings that could be used to compare studies. All studies with sufficient data on hip PVNS treatment outcomes were rated poorly with the Modified Coleman Methodology Scoring system.29 Selection bias was minimized by the inclusive nature of studies with level I to V evidence, but this led to a study design bias in that most studies consisted of level IV evidence.
Conclusion
Although the hip PVNS literature is limited, our review provides insight into expected outcomes. No matter which surgery is to be performed, surgeons must counsel patients about the high revision rate. One in 4 patients ultimately undergoes a second surgery, which may be required within 6 or 7 years after synovectomy without arthroplasty. Further development and innovation in hip arthroscopy may transform the treatment of PVNS. We encourage other investigators to conduct prospective, comparative trials with higher evidence levels to assess the utility of arthroscopy and other treatment modalities.
