Imagine this clinical scenario: your client competes in amateur-level showjumping with her 12-year-old Trakehner (Warmblood) gelding. The animal is presented to you with an acute injury to the medial branch of the right forelimb suspensory ligament, which you confirm with ultrasonography. You advise a course of conservative treatment, including rest, icing, cold water hosing and controlled exercise. However, your client asks if high-intensity laser therapy (HILT) could accelerate the gelding’s return to competition.
You decide to consult the evidence regarding the use of HILT to treat equine desmopathy in comparison with conservative management.
The evidence
Two peer-reviewed controlled studies were critically appraised: a non-randomised controlled clinical trial (Zielińska et al.,2020) and a randomised controlled experimental study (Pluim et al., 2020).
Controlled experimental study
Pluim et al. (2020) studied a sample of 12 warmblood horses aged 5 to 12 years without lameness that had normal results from an ultrasound examination of the suspensory ligament branches of all four limbs. Each horse was given one surgically induced lesion of the lateral branch of the suspensory ligament on each of its limbs, making for 48 lesions studied overall.
The right or left diagonal limb pair from each horse was randomly assigned to the control group, with the other limbs receiving 20 minutes of HILT per day for four weeks post-surgery. All horses had controlled exercise, including 20 minutes of hand-walking daily on a hard surface. Half of the subjects were studied for four weeks, and half were studied for six months, with lameness evaluations carried out weekly for four weeks, then monthly.
Other outcomes studied were general clinical signs, lesion heat, lesion size, swelling, pain, colour Doppler signal and echogenicity percentage on magnetic resonance imaging (MRI) scans.
Controlled clinical trial
Zielińska et al. (2020) studied a sample of 26 warmblood horses aged 5 to 24 years with 29 naturally occurring tendon and ligament lesions. All horses had a clinical diagnosis of either tendinopathy or desmopathy, which were confirmed by ultrasound and had not been treated previously. Of the 29 lesions sampled, 23 were randomly assigned to the treatment group.
The treatment group received 15 sessions of HILT, with the time between successive groups of sessions gradually increasing from one to four days. All patients (treatment and control) received conservative treatment, including 20 minutes of walking on a hard surface per day and daily cold-water hosing of the lesion.
The outcomes studied were pain on palpation, lameness assessment, relative swelling, lesion echogenicity and lesion percentage.
Limitations of the evidence
The overall strength of evidence is weak as each study has design, methodological, statistical analysis and reporting issues that reduce reliability and external validity.
Neither paper considers the impact of HILT on return to function in horses, which weakens the evidence specific to the clinical question of this piece
Firstly, neither paper considers the impact of HILT on return to function in horses, which weakens the evidence specific to the clinical question of this piece.
The publication by Pluim et al. (2020) also had the following limitations:
- Studying surgically induced lesions may have led to different outcomes than naturally occurring lesions
- The variance of the surgically induced lesions is not stated
- The lameness detection system was not specified
- The sample size was small
- The laser device software was custom to this study and details were not provided
- The method of randomisation and the method of assignment to evaluation groups was not reported
- Sample size calculations were not undertaken
Further, rationales for the selected study design and the different post-treatment evaluation groups were not provided. There were also additional reporting and test description omissions.
The publication by Zielińska et al. (2020) also had limitations, including the likelihood of selection bias, the possibility for allocation bias, questionable methods of randomisation, lack of sample size calculations and lack of reporting on the distribution of lesions. There were additional limitations to the methodology and reporting, including the risk of confirmation bias, subjective outcome measures, lack of post-treatment follow-up, reporting weaknesses relating to HILT treatment and a lack of confidence intervals.
Summary of findings
The findings of the two papers provide weak evidence to suggest that HILT is beneficial to the treatment of soft tissue injuries in horses. Additionally, neither study observed any adverse effects of HILT; however, this must be considered alongside the extensive limitations detailed above.
Neither study observed any adverse effects of HILT; however, this must be considered alongside the extensive limitations detailed above
In the study by Pluim et al. (2020), cross-sectional area (CSA) enlargement and circumference enlargement of lesions (based on ultrasound measurements at week four minus week one values) were both significantly smaller in the treatment group compared to control. The mean lesion transverse size of the treatment group was also significantly smaller than that of the control after two months. Similarly, in both the short- and long-term treatment groups, the mean lesion CSA from MRI was significantly smaller than that in the control group. Additionally, Doppler signal scores were significantly higher in the treatment group than in the control group during the treatment period.
Zielińska et al. (2020) found statistically significant differences between the treatment and control groups for each outcome measured. The treatment group had significantly lower pain and lameness scores, and mean relative swelling, echogenicity and lesion percentage.
Conclusion
There is weak evidence that horses treated with HILT and conservative management return to primary function sooner than horses treated with conservative management alone. While both studies demonstrated beneficial effects of HILT on treatment of equine soft tissue injuries, there were significant limitations that weakened the overall quality of evidence.
There is weak evidence that horses treated with HILT and conservative management return to primary function sooner than horses treated with conservative management alone
Further studies are required to improve the strength of the evidence on this topic, which incorporate improved study design, larger sample sizes, clearer reporting and more thorough statistical analysis.
| The full Knowledge Summary can be read in RCVS Knowledge’s open access journal Veterinary Evidence. |
Disclaimer
The application of evidence into practice should take into account multiple factors, not limited to individual clinical expertise, patient’s circumstances, owner’s values, the individual case in front of you, the availability of therapies and resources, and the country, location or clinic where you work.
Knowledge Summaries are a resource to help reinforce or inform decision making. They do not override the responsibility or judgement of the practitioner to do what is best for the animal in their care.
