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.