Clinical Effectiveness of Dry Needling on Myofascial Trigger Points in Horses: A Prospective Algometric Controlled Study

Abstract

Myofascial pain syndrome (MPS) is caused by trigger points (TrPs): hypersensitive spots in taut muscle bands that impair function and cause pain. Dry needling (DN) is a common treatment in humans, but evidence in horses is limited. This prospective, controlled study evaluated the effectiveness of DN in reducing TrP-related pain in the brachiocephalic muscle of horses. Of the 98 horses enrolled, 66 were allocated to a treatment group receiving weekly DN sessions for three weeks, while 32 were assigned to a control group with no intervention. Pain and function were assessed using pressure algometry, a numerical rating scale (NRS), a functional total test score (FTTS), and behavioral indicators including jump sign (JS), equine pain face (EPF), and local twitch responses (LTRs). Assessments were performed at baseline and at 0, 4, 24, and 72 h post-intervention. Results indicate a significant increase in pressure pain thresholds (p < 0.001), especially after the second and third sessions. Both NRS and FTTS improved significantly over time (p < 0.001), and LTRs progressively decreased. EPF and JS showed minimal variation. These results support the use of DN to reduce local muscle pain and improve function in horses with TrPs. Further robust studies are warranted to refine protocols and investigate long-term effects.

Keywords: algometry; dry needling; equine brachiocephalic muscle; horse; myofascial pain syndrome; pain; palpation; trigger point.

Figure 1

Design of the study. (TrPs: trigger points; DN: dry needling; NSR: numerical rate scale; FTTS: functional total test score; EPF: equine pain face; JS: Jump sign; LTRs: local twitch responses; POSTIA: immediately after; POST4 h: after 4 h; POST24 h: after24 h; POST72 h: after 72 h).

Figure 2

Maria Calatayud-Bonilla measuring pressure pain threshold with an algometer at the distal portion of the brachiocephalic muscle.

Figure 3

Dry needling procedure performed by Maria Calatayud-Bonilla. (a) Trigger point (TrP) in the distal brachiocephalic muscle identified via pincer palpation. (b) The needle was swiftly inserted through the skin, the guide tube removed, and the “Fast-in Fast-out” technique was applied to stimulate the TrP and elicit local twitch responses.

Figure 4

Box plots showing the estimated global mean values and 95% confidence intervals for algometry measurements (pressure pain threshold (PPT) kilogram-force/cm² (kgf/cm²)) in the horses in the study according to the treatment factor. ^a,b = Groups with different lower-case letters denote significant differences (p < 0.001) measured using the Tukey test.

Figure 5

Box plots showing the estimated global mean values and 95% confidence intervals for algometry measurements (PPT) (kgf/cm²)) in the horses in the study according to the treatment per week factors. ^a,b = Groups with different lower-case letters denote significant differences (p < 0.001) measured using the Tukey test.

Figure 6

Box plots showing the estimated global mean values and 95% confidence intervals for algometry measurements (PPT) (kgf/cm²)) in the horses in the study according to the treatment per week per hour factors. ^a–c = Groups with different lower-case letters denote significant differences (p < 0.001) measured using the Tukey test.

Figure 7

Box plots showing the estimated mean values and 95% confidence intervals for the functional test total score (FTTS) in the horses in the study according to time. ^a–c = Groups with different lower-case letters denote significant differences (p < 0.001) measured using the Tukey test.

Figure 8

Box plots showing the estimated mean values and 95% confidence intervals for numerical rating scales (NRS) in the horses in the study according to the time factor. ^a,b = Groups with different lower-case letters denote significant differences (p < 0.001) measured using the Tukey test.

Figure 9

Box plots showing the estimated mean values and 95% confidence intervals for number of local twitch responses (LTRs) according to time factor. ^a–c = Groups with different lower-case letters denote significant differences (p < 0.001) measured using the Tukey test.

Figure 10

Box plots showing the estimated mean values and 95% confidence intervals for number of LTRs according to the body side factor. ^a,b = Groups with different lower-case letters denote significant differences (p < 0.001) measured using the Tukey test.