Equine shock wave therapy - where are we now?

Over the past three decades, electrohydraulic extracorporeal shock wave therapy (ESWT) as a treatment modality for equine orthopaedic disorders has sparked exponential interest among practitioners, but its clinical applications are quickly evolving and a current review highlighting modernised equine clinical use is lacking. The objective of this review is to summarise the most current ESWT technology, evidence for its use, proposed mechanisms of action and clinical applications in horses while also highlighting the areas requiring further investigation. The three ways to generate a shock wave are through electrohydraulic, electromagnetic or piezoelectric mechanisms, but over the last decade, electrohydraulic systems have predominated due to the ability to focus and control a therapeutic waveform. Shock waves' primary physical effect is believed to be via mechanotransduction leading to cellular activation and downstream signalling. Experimentally, ESWT's effects on osseous, connective tissue and wound healing via various mechanisms of action have been reported both in the human and veterinary literature. Clinical trials have investigated ESWT's orthopaedic application including osteoarthritis, thoracolumbar pain, navicular syndrome, tendinopathy and proximal suspensory desmopathy, with its concomitant use with biologics representing an area of active research. Direct ESWT protocol comparisons in terms of long-term efficacy with variables of energy, depth and exposed tissue types are still lacking with evidence-based recommendations being largely anecdotal. Technical advancements to facilitate the safe and judicious use of ESWT include human and equine hearing protection, light sedation and/or patient restraint. Efforts to ensure the safe and judicious use of ESWT and its analgesic effects are ongoing.