Extracorporeal shockwave therapy raises mechanical nociceptive threshold in horses with thoracolumbar pain

Although extracorporeal shockwave therapy (ESWT) is a common treatment for horses with back pain, effects on mechanical nociceptive threshold (MNT) and multifidus muscle cross sectional area (CSA) in the spine are unknown.

To evaluate effects of ESWT on spinal MNT and multifidus muscle CSA in horses with thoracolumbar pain.

Non-randomised trial.

Thoracolumbar spines of 12 horses with thoracolumbar pain were radiographed to document existing pathology. Each horse received three ESWT treatments, 2 weeks apart (days 0, 14, 28). Palpation scores were documented (days 0, 45 and 65). Ultrasonographic CSA of left and right multifidus muscles was recorded at T12, T14, T16, T18, L3 and L5 (days 0, 45 and 65). MNT was measured at the same spinal sites every 7 days (day 0-56).

Mechanical nociceptive threshold in 10/12 horses (83%) was greater at each time point compared with day 0 (P < 0.05). Mechanical nociceptive threshold increased at all time points at six sites in 2/12 (16%), at five sites in 3/12 (25%), at four sites in 4/12 (33%) and at one site in 1/12 (8%; P < 0.05). Mechanical nociceptive threshold average per cent  increase from day 0 to 56 was 64% for the thoracic region (T12-T18) and 29% for the lumbar region (L3-L5). There was no statistical difference in MNT from day 35 to 56 (P = 0.25). A bimodal analgesic trend was observed following ESWT. Degree of radiographic change was not associated with response to treatment. No significant change in multifidus muscle CSA was observed.

Small study size and lack of control group.

Three treatments of ESWT 2 weeks apart raised MNT over a 56-day period in horses with back pain, but did not influence change in CSA of the multifidus muscle. While ESWT appears justifiable for analgesia, physiotherapeutic techniques may be necessary in conjunction for concurrent muscle rehabilitation.