Viscosupplementation with hyaluronic acid in hip osteoarthritis (a review).

Background: Viscosupplementation (VS) with hyaluronic acid (HA) is largely used for knee osteoarthritis therapy, but the evidences for its usefulness in hip osteoarthritis (OA) are limited. Methods: In this review, an extensive search of published trials on VS in hip OA was performed. From the selected papers the following data were extracted: sample size, inclusion / exclusion criteria, treatment procedures, evaluation methods, follow-up duration and clinical outcomes. Results: The level of evidence was low in quite all the trials (no placebo controlled groups). A reduction of pain and an improvement of function after 3 months, persistent in the long term (12 - 18 months), was observed. Patients with mild morphological alterations responded better to therapy. Side effects were negligible, and were limited to pain and a sensation of heaviness in the injection site. No clear differences among Low (LMW) and High Molecular Weight (HMW) HA preparations were found in the clinical outcomes. However, for HMW-HA preparations, a lower number of injections was, in general, necessary in order to reach the therapeutic effect. Conclusions: Despite the initial promising results, some questions still remain open : 1) the characteristics of responders must be more precisely defined; 2) the treatment schedules, at present mainly based on the individual clinical experience, need a proper and accepted standardization. Finally, larger and placebo controlled trials are necessary to confirm the efficacy of VS in hip OA.