In veterinary medicine, osteoarthritis (OA) is the most commonly diagnosed joint disease, with a high healthcare cost and impact on patients’ quality of life and welfare.1 The medical approach to OA aims to slow disease progression; relieve symptoms, particularly pain; and improve overall function.2,3 NSAIDs are frequently the first line of treatment in OA and are the mainstay of treatment of hip OA. Their popularity is probably due to a rapid efficacy in palliating pain in animals with OA and relative ease of administration.4 Meloxicam is a cyclooxygenase-2 selective, with potent anti-inflammatory activity and low gastrointestinal and renal toxicity,4 improving ground reaction forces in treated animals up to normal values.5 Photobiomodulation therapy (PBMT) uses red/near infrared light to produce a clinical effect. Commonly attributed effects of PBMT include stimulation of tissue healing, analgesia, reduced inflammation, and a noninvasive nature allied with a lack of adverse effects.6 PBMT helps to modulate cellular functions and is defined as the nonthermal interaction of monochromatic radiation with a target site. This photobiostimulation upregulates the production of ATP, nitric oxide, and reactive oxygen species within cells, alters gene transcription, and increases cell proliferation, cellular motility, and growth factor production.7 It has been described in the management of canine elbow osteoarthritis, chronic gingivostomatitis, wound healing, and postoperative period.8–11 Despite the increasing number of reports on the potential uses of PBMT, there is still a need to outline specific protocols for the different conditions being treated.10
Pain is a multidimensional experience, encompassing more than just a functional aspect.12 Several clinical metrology instruments (CMI) have been developed to approach these multiple dimensions, embodying a patient-centered view. There are several CMIs validated in dogs, such as the Liverpool Osteoarthritis in Dogs (LOAD), the Hudson Visual Analogue Scale (HVAS), the Canine Brief Pain Inventory (CBPI), and the Canine Orthopaedic Index (COI). Some can encompass several dimensions: the CBPI (divided into a pain severity score [PSS] and a pain interference score [PIS]) and the COI (divided into 4 scores: stiffness, gait, function, and quality of life [QOL]).2,13–19 Thermal imaging is a modality under increased interest, and recent studies20–25 in dogs have assessed different diseases in the hip, stifle, elbow, intervertebral disc, and bone neoplasia. It relies on identifying changes in heat in tissues due to disruptions of tissue morphology or physiological functions. These changes, in turn, relate to skin temperature control.26 Injuries to tissues are often associated with variations in blood flow on the affected site, changing the temperature at the skin level.27 During the physical examination of patients, muscle mass evaluation is a standard procedure since muscular atrophy is a consistent finding that may be evident within a few weeks of OA onset.28,29 Additionally, a restricted range of motion (ROM) is usually present.28,30 The evaluation of asymmetry, muscle atrophy level, and joint ROM measurement has been described as the most valid and sensitive physiotherapeutic evaluation method.31,32
We aimed to evaluate the effectiveness of PBMT in Police working dogs with hip OA compared with treatment with the NSAID meloxicam. We hypothesize that PBMT can reduce pain scores in police working dogs with hip OA-related pain.
Materials and Methods
The study’s protocol was approved by the Ethical Review Group of the Association of Veterinary Anaesthetists (No. 2019-017) and complies with the NIH Guidelines for Humane Care and Use of Animals. Written, informed consent was obtained from the institution responsible for the animals (Guarda Nacional Republicana, Portuguese Gendarmerie).
To be included in the study, animals should have a history (difficulty rising and jumping and stiffness), physical examination (pain during joint mobilization and reduced range of motion), and radiographic findings (Orthopedic Foundation for Animals, hip scores of mild, moderate, or severe) consistent with bilateral hip OA. Additionally, they should be over 2 years, have a body weight ≥ 20 kg, and a body condition score of 4 or 5 on the LaFlame scale.33 They could not have received another treatment protocol or nutritional supplement > 6 weeks. Exclusion criteria included suspected or documented orthopedic, neurological, or other concomitant disease. These diseases we ruled out through physical examination, complete blood count, and serum chemistry profile. All animals worked actively during and after the study.
Forty joints (n = 40) from 20 dogs with bilateral disease comprised the sample for this study, constituting a convenience sample, and were randomly assigned to 2 groups using the statistical analysis software, according to the treatment being administered. Both joints of each animal received the same treatment. Twenty joints constituted a positive control group (CG) and received meloxicam (Acticam; Ecuphar) for 21 days, at a dose of 0.2 mg/kg, PO, q 24 h. On the same days as the treatment group, they were submitted to a sham laser therapy session (the operator conducted the same procedures as if a lasertherapy session was conducted without starting the laser, 0 J/cm2). Twenty other joints were assigned to a treatment group (TG) and received PBMT with a therapeutic laser (CTC Class IV Laser; Companion, Litecure LLC). PBMT parameters can be observed in Table 1. Sessions were conducted for 3 consecutive weeks in the following fashion: on week 1, 3 sessions every other day; on week 2, 2 sessions, 2 days apart; and on week 3, a single session. They also received a 21-day course of a placebo with the physical appearance of the meloxicam pill, to be administered according to the manufacturer’s indications for meloxicam. Both meloxicam and placebo were packed in a similar fashion.
Photobiomodulation therapy treatment parameters.
| Light parameters (dose) | Notes | |
|---|---|---|
| Wavelength (nm) | 980 (for patients with dark coat color) | Blend consists of 80% of 980 nm and 20% of 808 nm |
| 980/808 blend (for patients with light to medium coat color) | ||
| Radiant Power (W) | 6.5–8 | |
| Irradiance (W/cm2) at skin surface | 4.2–5.2 | Depending on patient size, with smaller/thinner patients being treated at lower power; irradiance increased with increase in power |
| Fluence (J/cm2) | 14.3–19.5 (average over treated area) | |
| Treatment Protocol | Continuously moving grid pattern in contact over the area of the greater trochanter at a speed of 2.5–7.5 cm/s, according to manufacturer recommendations | |
| Treatment Area (cm2) | 225 | |
| Treatment Time | Between 4 min, 35 s to 5 min, 5 s |
Before collecting digital thermography images, patients were maintained for 30 minutes in a room with a controlled temperature set at 21°C. They were then positioned standing still, as symmetrically as possible, with the handler outside the image and without touching the dog’s torso. All thermographic images included the area from the last lumbar vertebra to the first coccygeal vertebra at a distance of 0.6 m.34 Lateral views were taken with the greater trochanter in the center of the image, also at a distance of 0.60 m, perpendicular to the long axis of the limb. All images were registered with the same camera (ThermaCAM E25; FLIR Systems, Inc), with a range of temperature set at 15 to 40°C and emissivity at 0.98. A free software (Tools; FLIR Systems, Inc) was used to analyze thermographic images with a Rainbow HC color pallet.25 Temperature boxes of equal size were placed on the hip joint’s anatomical area on both views to determine mean and maximal temperatures. A dorsoventral image was captured before and after that period, and mean and maximal results were compared to assess changes induced by the acclimatization period. The thigh girth was determined with a Gullick II measuring tape and obtained at a distance of 70% thigh length, as measured from the greater trochanter’s tip, with the leg in an extended position while in lateral recumbency and the dog relaxed.35 ROM of the hip joints was obtained at extension and flexion with a goniometer (Veterinary Instrumentation, UK).36 Each measurement was performed 3 times, and a mean value was determined. The same researcher, blinded to the dog’s treatment group, performed all evaluations.
The CMIs were completed in sequence by the same handler in each assessment. This procedure was conducted in a quiet room with as much time as needed to answer all items. Handlers did not know their previous answers and were blinded to the treatment group the dog was allocated to. As CBPI has 2 sections (PSS and PIS) and COI has 4 dimensions (stiffness, function, gait, and QOL), all sections and dimensions were considered in the analysis. Since an improvement with HVAS consists of an increased score, while the opposite occurs in the remaining CMIs, HVAS scores were inverted by subtracting the result from 10 (the higher possible range score) to facilitate interpretation of the results.
Scheduled follow-up evaluations were conducted at +8, +15, +30, and +90 days after the initial treatment. At these moments, all described evaluations were repeated. Additional evaluations were performed as needed if the animal exhibited a decrease in performance, showed signs of pain during exercise or physical examination, or had a decrease in the results of the CMI, returning to the initial values, at which point rescue analgesia would be instituted.
Normality was assessed with a Shapiro-Wilk test. CMI between groups scores were compared using a Mann-Whitney Test in each evaluation moment. Digital thermography, goniometry, and ROM between groups results were compared with repeated measures ANOVA, with a Huynh-Feldt correction. As for HVAS, LOAD, and COI, no specific measure of success is published, the outcome considered was a return to or drop below the initial values of CMI scores at the +90-day evaluation. This particular outcome was selected as it was the point that motivated the need for medical assistance.37,38 With the CBPI, a specific measure of success has been defined, set as a reduction of ≥ 1 in PSS and ≥ 2 in PIS.39 For that reason, for these scores, the Kaplan-Meier test was used to evaluate the score’s time to drop below these measures of success levels. Patients with scores above baseline values at the final evaluation moment were censored. The Kaplan-Meier was performed to generate survival curves, and survival probability and results were compared with the Breslow test. All results were analyzed with commercially available software (IBM SPSS Statistics version 20), and a significance level of P < 0.05 was set.
Results
The sample included 40 pelvic limbs (n = 20 left and 20 right) of 20 active police dogs. They had a mean age of 8.3 ± 1.9 years and a body weight of 29.8 ± 5.5 kg, representing both sexes (n = 22 in male; 18 in female). Four dog breeds were represented, similarly distributed between CG and PBMT: German Shepherd Dogs (n = 8, 5 in CG and 3 in PBMT), Labrador Retriever (6, 3 in CG and 3 in PBMT), Belgian Malinois Shepherd Dogs (3, 1 in CG and 2 in PBMT), and Dutch Shepherd Dog (3, 1 in CG and 2 in PBMT). At the initial evaluation, 26 (n = 14 in CG and 12 in PBMT) joints were classified as having moderate OA and 14 (6 in CG and 8 in PBMT) as severe. All patients were followed up to the 90 days evaluation moment, and during this period, no additional treatment or medications was administered. CMI scores for both groups are presented in Table 2. An improvement was observed in most CMI scores in PBMT from +8 days, and this beneficial effect weaned off after the end of the treatment sessions. Table 3 presents each group’s joint range of motion and tight girth measurements. Significant improvements were observed in flexion and extension in PBMT, starting at +15 days up to the last evaluation point. Results of the Kaplan-Meier estimators with each evaluation method are presented in Table 4, and Figure 1 presents Kaplan Meier plots for the COI gait dimension. PBMT showed more extended periods with better results, with patients taking longer to return to baseline values and scores. The results of the digital thermography evaluation are presented in Table 5. Lower values were recorded in both thermographic views of joints in the PBMT during the treatment period. Digital thermography evaluations were significantly different before and after the acclimatization period (P < 0.01), being lower after it. No side effects were recorded in either group.
Evolution of mean clinical metrology instrument scores (±SD) by group and moment.
| T0 | +8 d | +15 d | +30 d | +60 d | +90 d | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Clinical metrology instrument/group | Score | SD | P | Score | SD | P | Score | SD | P | Score | SD | P | Score | SD | P | Score | SD | P |
| CBPI | ||||||||||||||||||
| PIS | ||||||||||||||||||
| CG | 5.4 | 1.4 | 0.50 | 5.3 | 1.5 | 0.21 | 5.3 | 1.5 | 0.02* | 5.3 | 1.9 | 0.04* | 5.1 | 1.5 | 0.13 | 5.2 | 1.3 | 0.71 |
| PBMT | 4.5 | 2.7 | 4.3 | 2.6 | 3.6 | 2.7 | 3.8 | 2.8 | 4.3 | 3.2 | 4.8 | 3.5 | ||||||
| PSS | ||||||||||||||||||
| CG | 5.1 | 1.7 | 0.17 | 5.6 | 1.7 | 0.007* | 5.6 | 1.7 | 0.009* | 4.9 | 1.9 | 0.04* | 4.7 | 1.3 | 0.23 | 5.2 | 1.3 | 0.22 |
| PBMT | 4.2 | 1.9 | 3.9 | 1.9 | 3.8 | 2.4 | 3.4 | 2.4 | 4.2 | 2.9 | 4.7 | 3.4 | ||||||
| HVAS | ||||||||||||||||||
| CG | 4.1 | 0.5 | 0.39 | 4.3 | 0.9 | 0.02* | 4.3 | 0.9 | 0.03* | 4.6 | 1.0 | 0.006* | 4.2 | 0.7 | 0.08 | 4.1 | 0.8 | 0.35 |
| PBMT | 4.4 | 0.9 | 3.4 | 1.2 | 3.2 | 1.0 | 3.4 | 1.2 | 3.5 | 1.4 | 4.3 | 2.1 | ||||||
| LOAD | ||||||||||||||||||
| CG | 19.5 | 7.0 | 0.35 | 23.3 | 7.2 | 0.07 | 23.3 | 7.2 | 0.04* | 26.0 | 9.3 | 0.04* | 23.6 | 8.2 | 0.24 | 22.9 | 8.9 | 0.26 |
| PBMT | 21.1 | 8.2 | 18.4 | 9.7 | 17.4 | 7.6 | 18.3 | 9.3 | 20.8 | 12.7 | 20.8 | 11.2 | ||||||
| COI | ||||||||||||||||||
| Stiffness | ||||||||||||||||||
| CG | 5.8 | 1.9 | 0.58 | 6.9 | 2.2 | 0.07 | 6.9 | 2.2 | 0.02* | 7.8 | 3.4 | 0.06 | 6.6 | 2.3 | 0.22 | 6.9 | 2.6 | 0.39 |
| PBMT | 5.9 | 3.1 | 5.2 | 3.1 | 4.3 | 2.9 | 5.0 | 2.8 | 5.3 | 5.3 | 5.7 | 5.4 | ||||||
| Function | ||||||||||||||||||
| CG | 7.0 | 3.5 | 0.46 | 8.0 | 4.0 | 0.04* | 8.0 | 4.0 | 0.012* | 8.8 | 3.6 | 0.013* | 7.5 | 2.6 | 0.13 | 7.6 | 3.5 | 0.26 |
| PBMT | 5.3 | 4.5 | 4.8 | 4.6 | 3.8 | 3.6 | 5.2 | 4.0 | 5.5 | 6.4 | 5.8 | 5.8 | ||||||
| Gait | ||||||||||||||||||
| CG | 8.9 | 3.3 | 0.96 | 10.1 | 3.5 | 0.06 | 10.1 | 3.5 | 0.08 | 11.2 | 2.9 | 0.013* | 9.8 | 3.2 | 0.15 | 9.3 | 3.8 | 0.34 |
| PBMT | 8.8 | 3.9 | 6.7 | 4.7 | 6.3 | 4.8 | 6.4 | 5.0 | 6.9 | 5.7 | 7.7 | 6.1 | ||||||
| QOL | ||||||||||||||||||
| CG | 5.6 | 1.7 | 0.72 | 6.3 | 1.9 | 0.16 | 6.3 | 1.9 | 0.20 | 6.3 | 2.4 | 0.35 | 6.1 | 2.1 | 0.54 | 5.8 | 2.2 | 0.85 |
| PBMT | 5.9 | 2.1 | 5.0 | 2.3 | 5.4 | 2.8 | 5.2 | 3.2 | 5.8 | 3.5 | 5.8 | 3.7 | ||||||
| Overall | ||||||||||||||||||
| CG | 27.3 | 9.0 | 0.58 | 31.3 | 10.2 | 0.04* | 31.3 | 10.2 | 0.03* | 34.2 | 11.7 | 0.02* | 30.0 | 9.2 | 0.23 | 29.5 | 11.4 | 0.28 |
| PBMT | 25.9 | 12.9 | 21.7 | 13.9 | 19.6 | 13.5 | 21.9 | 13.9 | 23.4 | 20.2 | 25.0 | 20.6 | ||||||
CBPI + Canine Brief Pain Inventory. CG = Control group. COI = Canine Orthopedic Index. HVAS = Hudson Visual Analogue Scale. LOAD = Liverpool osteoarthritis in dogs. PBMT = Photobiomodulation group. PIS = Pain interference score. PSS = Pain severity score. QOL = quality of life. T0 = Time 0.
Significance when comparing groups at each follow-up moment.
Evolution of mean values joint range of motion (in degrees) and tight girth measurements (in cm) (±SD) by group and moment.
| T0 | +8 d | +15 d | +30 d | +60 d | +90 d | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Measurement/group | Score | SD | P | Score | SD | P | Score | SD | P | Score | SD | P | Score | SD | P | Score | SD | P |
| ROM | ||||||||||||||||||
| Flexion | ||||||||||||||||||
| CG | 56.80 | 4.30 | 0.15 | 57.30 | 2.30 | 0.12 | 57.00 | 4.30 | < 0.001* | 54.70 | 2.60 | 0.03* | 52.60 | 2.60 | < 0.001* | 51.60 | 2.20 | < 0.001* |
| PBMT | 57.20 | 3.30 | 55.40 | 3.00 | 54.70 | 4.80 | 52.10 | 2.70 | 55.50 | 1.00 | 53.30 | 3.40 | ||||||
| Extension | ||||||||||||||||||
| CG | 154.80 | 5.30 | 0.26 | 150.00 | 4.30 | 0.58 | 149.80 | 3.60 | 0.08 | 150.20 | 3.40 | < 0.001* | 150.50 | 3.20 | < 0.001* | 152.10 | 2.80 | 0.03* |
| PBMT | 149.20 | 2.50 | 150.60 | 3.60 | 152.40 | 3.30 | 152.90 | 2.10 | 154.00 | 2.50 | 154.80 | 3.70 | ||||||
| Thigh girth | ||||||||||||||||||
| CG | 31.00 | 2.24 | 0.27 | 31.10 | 3.12 | < 0.001* | 30.50 | 3.14 | < 0.001* | 30.30 | 2.97 | 0.69 | 31.10 | 2.78 | 0.06 | 31.50 | 2.42 | 0.06 |
| PBMT | 27.50 | 3.11 | 26.60 | 1.10 | 27.40 | 2.86 | 26.80 | 2.90 | 27.30 | 3.77 | 28.10 | 3.66 | ||||||
Significance when comparing groups at each follow-up moment.
Time (in days) to clinical metrology instrument scores to return to baseline values, calculated with Kaplan-Meier estimators and compared with the Breslow test.
| Group | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| CG | PBMT | ||||||||||
| Clinical metrology instrument | Breslow test | Mean | Median | SD | 95% CI | Mean | Median | SD | 95% CI | ||
| CBPI | |||||||||||
| PSS | 0.12 | 65.6 | 8.0 | 7.5 | 500.8 | 80.4 | 72.5 | 90.0 | 2.1 | 29.9 | 115.1 |
| PIS | 0.01* | 45.3 | 8.0 | 9.9 | 25.7 | 64.8 | 77.9 | 90.0 | 6.1 | 65.9 | 89.9 |
| HVAS | 0.00* | 24.7 | 8.0 | 7.7 | 9.6 | 39.9 | 83.3 | 90.0 | 4.8 | 74.0 | 92.6 |
| LOAD | 0.00* | 39.0 | 8.0 | 8.3 | 22.8 | 55.2 | 65.7 | 60.0 | 6.9 | 52.1 | 79.3 |
| COI | |||||||||||
| Stiffness | 0.00* | 24.8 | 8.0 | 7.7 | 9.6 | 39.9 | 50.6 | 30.0 | 7.1 | 36.7 | 64.4 |
| Function | 0.11 | 48.0 | 30.0 | 9.1 | 30.2 | 65.8 | 64.3 | 90.0 | 7.5 | 49.7 | 78.9 |
| Gait | 0.00* | 37.8 | 8.0 | 8.6 | 20.8 | 54.7 | 69.4 | 90.0 | 7.8 | 54.1 | 84.7 |
| QOL | 0.00* | 23.8 | 8.0 | 5.7 | 12.5 | 34.8 | 64.3 | 90.0 | 7.5 | 49.7 | 78.9 |
| Overall | 0.16 | 48.0 | 30.0 | 9.5 | 29.4 | 66.9 | 59.7 | 90.0 | 8.6 | 43.1 | 76.7 |
Significance.
Kaplan-Meier curve demonstrating a significant difference between control group and photobiomodulation therapy (PBMT) group in time for the gait dimension of the Canine Orthopedic Index to return to baseline values (P = 0.00).
Citation: American Journal of Veterinary Research 83, 8; 10.2460/ajvr.22.03.0036
Kaplan-Meier curve demonstrating a significant difference between control group and photobiomodulation therapy (PBMT) group in time for the gait dimension of the Canine Orthopedic Index to return to baseline values (P = 0.00).
Citation: American Journal of Veterinary Research 83, 8; 10.2460/ajvr.22.03.0036
Kaplan-Meier curve demonstrating a significant difference between control group and photobiomodulation therapy (PBMT) group in time for the gait dimension of the Canine Orthopedic Index to return to baseline values (P = 0.00).
Citation: American Journal of Veterinary Research 83, 8; 10.2460/ajvr.22.03.0036
Evolution of digital thermography evaluation mean and maximal values (±SD), a dorsoventral (DV) and lateral (Lat) views, by group and moment.
| T0 | +8 d | +15 d | +30 d | +60 d | +90 d | |||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| View/group | Score | SD | Score | SD | P | P | Score | SD | P | P | Score | SD | P | P | Score | SD | P | P | Score | SD | P | P |
| DV | ||||||||||||||||||||||
| Mean | ||||||||||||||||||||||
| CG | 25.4 | 1.04 | 24.3 | 1.47 | 0.01* | 1.00 | 26.7 | 0.88 | 0.10 | < 0.01* | 25.3 | 1.63 | 0.42 | < 0.01* | 25.9 | 1.37 | 0.09 | 0.66 | 25.2 | 1.22 | 0.18 | < 0.01* |
| PBMT | 25.1 | 1.37 | 26.2 | 1.69 | 0.00* | 24.8 | 3.70 | 0.00* | 24.6 | 0.48 | 0.00* | 26.1 | 1.84 | 0.01* | 27.9 | 1.88 | 0.00* | |||||
| Max | ||||||||||||||||||||||
| CG | 25.7 | 1.71 | 25.3 | 1.73 | 0.06 | 0.42 | 28.6 | 1.30 | 0.47 | 0.01* | 26.1 | 2.24 | 0.42 | < 0.01* | 27.2 | 1.44 | 0.04* | 0.79 | 31.4 | 1.75 | 0.47 | < 0.01* |
| PBMT | 26.0 | 1.80 | 28.7 | 2.16 | 0.00* | 25.9 | 3.82 | 0.00* | 25.2 | 0.68 | 0.00* | 27.4 | 2.10 | 0.04 | 29.2 | 2.85 | 0.01* | |||||
| Lat | ||||||||||||||||||||||
| Mean | ||||||||||||||||||||||
| CG | 26.4 | 2.54 | 31.3 | 2.27 | 0.00* | < 0.01* | 29.3 | 2.94 | 0.04* | 0.05 | 30.2 | 2.00 | 0.00* | < 0.01* | 28.5 | 2.06 | 0.00* | 0.07 | 27.3 | 1.96 | 0.56 | < 0.01* |
| PBMT | 25.6 | 4.02 | 26.3 | 4.02 | 0.00* | 25.7 | 4.31 | 0.12 | 25.8 | 4.10 | 0.01* | 27.2 | 3.52 | 0.05 | 29.3 | 2.39 | 0.00* | |||||
| Max | ||||||||||||||||||||||
| CG | 28.5 | 2.63 | 34.7 | 1.03 | 0.00* | < 0.01* | 34.8 | 0.66 | 0.00* | <0.01* | 34.1 | 1.07 | 0.00* | < 0.01* | 30.8 | 2.02 | 0.00* | 0.06 | 29.6 | 2.17 | 0.31 | < 0.01* |
| PBMT | 27.6 | 4.12 | 28.4 | 3.75 | 0.00* | 28.1 | 3.66 | 0.16 | 28.9 | 4.83 | 0.02* | 28.8 | 3.70 | 0.13 | 31.4 | 2.28 | 0.00* | |||||
Significance when comparing groups at each follow-up moment.
Discussion
Osteoarthritis is the most commonly diagnosed joint disease in veterinary medicine, leading to an impaired mechanical function of the joint and pain.1 Our results show that PBMT can reduce pain levels and improve clinical findings in dogs with hip OA.
The effect of PBMT in the management of canine elbow OA has been described, and treated patients showed significant improvements in lameness and pain scores compared with control.8 Our results show that PBMT can have a similar effect in managing hip OA, even in very active working dogs. This improvement was observed in most CMI scores considered from the first evaluation point, at +8 days. PIS and stiffness scores were exceptions, which only improved after the +15-day evaluation, similar to joint ROM. This delayed improvement may be attributed to these scores reflecting a functional aspect of OA and following clinical findings. The beneficial effect weaned off after the end of the treatment sessions, with these improvements still being observed at +30 days, but not at +60 and +90 days, where no differences were observed between groups. This same phenomenon can be observed in Table 3, where nearly the same number of patients have returned to baseline values around the +60 days evaluation. The mean number of days that joints in the PBMT took to return to baseline values was significantly higher than in CG. PBMT group also showed an improvement in joint ROM. This is a commonly performed measurement,17,40 and its improvement was still observed at the +90-day evaluation point.
When comparing group results, although a significant difference was observed between CG and PBMT, the changes observed were lower than what has been described previously with these outcome measures, including a lack of improvements in the CG.39,41 One of the reasons for this finding may be related to the nature of the sample, composed exclusively of active working dogs. For these dogs, as their musculoskeletal structures are under increased effort compared to a companion animal, managing the disease with a single modality as NSAIDs may provide a lower level of control over the signs and symptoms of OA, as has been described previously.42,43 In addition, since large breed dogs of ideal body condition were included in the sample, results may differ in dogs with different sizes and conformations. However, the use of PBMT with an NSAID may lower its dose requirement in patients with elbow OA.8 Also, mean pain scores in both groups showed that animals had a moderate pain level, making it harder to reduce pain levels significantly. The fact that no improvements were observed in the CG can also contribute to the significant differences observed between groups. In addition, although undoubtedly useful, central tendency measures may not always adequately represent the condition/response of individual patients. This is particularly true in conditions such as OA, where the severity of clinical signs can vary significantly between individuals. For that reason, we chose to conduct survival analysis, where individual results are considered,39 and with this approach, significant differences between groups were still observed. Still, published measures of success are only published for the CBPI.39 For the remaining CMIs, we set as an outcome a return to or drop below the initial values of CMI scores, as it was the point that motivated the need for medical assistance.37,38 Further studies should aim to determine specific outcome measures.
The beneficial effects of PBMT are in contrast to what was recorded in CG. We used a set treatment dose of 10 J/cm2, which seems to be a good starting point in managing hip OA, similarly to what has been described for elbow OA.8 In addition to determining an appropriate treatment dosage, an individual evaluation of treatment frequency should also be performed. We chose a set number of sessions with decreasing frequency to compare a standard treatment protocol. It is possible that a different treatment frequency can produce different results, which should be addressed in future studies.
OA is a chronic low inflammatory-driven disease.44 PBMT has a documented anti-inflammatory effect, attributed to an improvement in circulation,45,46 while also aiding in slowing degenerative myelopathy progression.47 This anti-inflammatory effect may be responsible for the part of the effect we observed in PBMT. The same effect may also be why lower values were recorded in both thermographic views of joints in the PBMT during the treatment period and was still recorded at the +30-day evaluation. After the treatment was discontinued, this effect weened, and no differences were observed at the +60-day evaluation point. The characteristics of the breed’s coats being evaluated must also be considered. A previous study showed that German Shepherd dogs have lower values during thermographic evaluation than the other considered breeds.48 The animals included in this study had short hair, and some had a double coat. The breeds included were similarly distributed between groups, which may help balance these differences. Our results also show that an acclimatization period is required before thermographic evaluation in dogs since a significant difference was observed in thermographic values before and after this period. Although significant differences in muscle masses have been observed between the 2 groups, the difference between the 2 treatments is small. Since no specific exercises were introduced to increase muscle masses, it is possible that more time would be required for that event to take place. It also may indicate that both treatments could stop muscle loss, despite a slight initial decrease observed in PBMT at the +8-day evaluation moment.
NSAIDs have well-known side effects, such as gastrointestinal toxicity and increased risk of interdrug interactions.49 When misused, therapeutic lasers have the potential to be hazards to the eyes and skin.50 We did not observe any side effects in either group. A reason for using NSAIDs as a first line of treatment in animals with OA is their relative ease of administration.4 It is undoubtedly something clinicians must consider, as PBMT requires frequent visits, at least at an initial treatment phase, which may influence compliance to treatment.
The study presents some limitations, namely the size of the considered sample and the fact that it included a majority of moderate OA joints. Including many animals and a more significant proportion of the remaining hip grades would be interesting. While extremely useful in a clinical setting, subjective scales are more susceptible to bias than objective measures. An example is the case of the caregiver placebo effect from both owners and assisting veterinarians.51,52 For that reason, and since a positive control was used and both groups were receiving active treatment, the handlers completing the CMIs may be expecting to see an improvement. Still, the handlers were blinded to the assigned group of their dog, and an improvement was only observed in the PBMT. Although all CMIs considered have been validated with an objective measure as a reference, future studies should include force plait gait analysis or weight-bearing distribution evaluation. A limitation of the CMIs is also related to the fact that what constitutes a significant improvement has only been determined for the CBPI. For that reason, we chose to consider a return to the value of the initial evaluation since it was the moment that motivated the need for veterinary assistance and, for that reason, was significant for that animal. An additional limitation is the inclusion of 2 joints from each dog, as an association may occur between limbs.53,54 Still, the inclusion of contralateral limbs from the same patient is common in animal models,16,55,56 and in dogs with hip OA, major weight shifts occur to the contralateral thoracic limb rather than side-to-side compensation.57 Further studies should also evaluate the effect of PBMT in combination with other commonly used therapeutic approaches to OA.
In conclusion, this prospective, positive-controlled, double-blinded study showed that PBMT reduced pain levels and improved clinical findings in dogs with hip OA compared to the NSAID meloxicam. This beneficial effect weaned off after the end of the treatment sessions. Photobiomodulation therapy may present a noninvasive, cost-effective, low-risk treatment option for canine hip OA.
Acknowledgments
The authors declare that they have no competing interests. No third-party funding or support was received in connection with this study or the writing or publication of the manuscript.
The authors thank Manuel Pereira for the assistance in the data analysis.
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