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.
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.
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.
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.