C. Byron; A. Stewart; B. Benson; B. Tennent-Brown; J. Foreman Veterinary and Comparative Orthopaedics and Traumatology 2009 22 2 113-118 Objective: To investigate the effects of radial extracorporeal shock wave therapy (RESWT) on radiographic and scintigraphic variables in horses with clinical pain referable to the palmar heel. Methods: Eight clientowner horses with palmar heel pain were treated with RESWT for a total of three treatments. Nuclear scintigraphy and radiography were repeated at the beginning and completion of the study. Scintigram region of interest (ROI) density ratios were calculated and compared between treated limbs, untreated limbs, and a population of comparison limbs from eight horses free of lameness. Radiographs were scored for whole navicular bone appearance as well as distal border synovial fossae number and severity. Results: There was not any pre- versus post-treatment difference in scintigraphic navicular pool phase or delayed phase ROI density ratios in treated limbs, or between treated and untreated limbs. Delayed phase ROI density was increased in the central navicular region in treated limbs compared to comparison limbs from non-lame horses at both time points. Radiographic scores remained unchanged. Clinical significance: RESWT as applied in the present study has no effect on acute palmar heel region scintigraphic or radiographic parameters. Any acute clinical benefit may be due to analgesic effects rather than stimulation of local tissue metabolism.