Elbow dysplasia is a heritable disease that results in chronic, debilitating OA of the elbow joints in dogs. Multiple theories have been advanced regarding the cause of the clinical and radiographic changes in dogs with elbow dysplasia, but no definitive explanation for the origin of this condition is available.1,2 Treatment options include surgical and medical approaches, but none of the currently available options stop the progression of OA. Some patients improve clinically, whereas others remain chronically lame.3–10 Therefore, additional treatments to palliate chronic pain in dogs with elbow dysplasia are needed.
Complementary and alternative medical treatment options have increased in popularity in the human and veterinary medical fields in recent years.11,12 Of the complementary and alternative medical treatment options currently available, acupuncture is one of the most common. Acupuncture activates endogenous opioid mechanisms in the brain that then alter nociceptive processing and pain perception,13–15 and the National Institutes of Health Consensus Development Panel has stated that needle acupuncture has clear evidence of effect for human use for postoperative pain and chemotherapy-induced nausea and vomiting.16 The National Institutes of Health has also concluded that acupuncture has moderate benefits in the treatment of dental pain,16 but information on the effects of acupuncture for the treatment of chronic pain conditions is equivocal.
The criteria to evaluate responses to treatment in clinical trials should be the same, regardless of whether traditional medical or complementary and alternative medical approaches are used. Force plate gait analysis has been used as an objective measure of lameness in dogs with elbow dysplasia,3,8 and there is good evidence that force plate gait analysis can be used to evaluate the improvement in lameness in dogs with OA that have been treated with nonsteroidal anti-inflammatory drugs.17–21 To the authors' knowledge, only a single study22 has used force plate gait analysis to evaluate responses following use of acupuncture to treat lameness in dogs. In that study,22 gold bead acupuncture was used to treat dogs with hip dysplasia and no differences in GRFs were found between dogs treated with acupuncture and sham-treated dogs. However, some researchers have argued that because individual patients have individual responses, use of a crossover design would have been a better test of efficacy.
There are several ways to deliver acupuncture (eg, dry needling, manual pressure, injection of fluid, and cold or heat stimulation), and the delivery method can be expected to affect the results obtained. Electrostimulated acupuncture involves application of low-frequency (2 to 15 Hz) electricity to acupuncture needles during stimulation. There is some evidence that lowfrequency stimulation, which releases β-endorphin and met-enkephalin in the brain and dynorphin in the spinal cord, is superior to other methods in alleviating deep and chronic pain.14 In addition, ESA was found to be more effective than manual acupuncture in humans with lateral elbow pain.23
We hypothesized that ESA will decrease pain in dogs with chronic elbow OA secondary to elbow dysplasia, resulting in a lessening of the severity of lameness. Specifically, the purpose of the study reported here was to determine whether use of ESA would result in significant improvements in ground reaction forces and lameness scores in dogs with chronic elbow OA secondary to elbow dysplasia.
Materials and Methods
Study design—The study was designed as a randomized, controlled, single-crossover, clinical trial. Ten dogs were enrolled in the study, but 1 did not complete the study because of illness unrelated to the forelimb lameness. Thus, only 9 dogs completed the study. All of the dogs that completed the study had clinical signs of forelimb lameness and radiographic evidence of elbow OA at the time of enrollment; in all dogs, signs had been present for > 1 year. There were 6 Labrador Retrievers, 1 Golden Retriever, 1 German Shepherd Dog, and 1 mixed-breed dog. For 3 of the 9 dogs, body condition score was > 5 on a scale from 1 to 9; for the other 6, body condition score was ≤ 5. Eight had bilateral elbow OA, and 1 had unilateral elbow OA. Five of the 9 dogs had undergone surgery for treatment of elbow dysplasia when < 1 year old and were reported by their owners to have shown some improvement following surgery. Three dogs had concurrent radiographic evidence of OA of the hip joints but did not have clinically evident hind limb lameness at the time of the study. One dog had previously undergone surgery for treatment of bilateral cranial cruciate ligament tears. An interval of 6 months separated the 2 surgeries, and the second surgery had been performed > 1 year prior to the present study. All dogs were removed from analgesic medications and nutraceuticals during all phases of the study. This study was approved by the institutional animal care and use committee, and owner consent was obtained for all dogs enrolled in the trial. Owners were instructed to maintain a constant activity level for their dogs throughout the study and, in particular, to avoid allowing their dogs to exercise more because they were apparently feeling better.
The study consisted of 3 phases. The first phase consisted of a 2- to 3-week-long control phase during which dogs were allowed to become acclimated to the force plate and baseline GRF data were collected. Dogs were then randomly assigned to undergo a 3-week-long acupuncture treatment phase followed by a 3-week-long sham treatment phase (5 dogs) or to undergo a 3-week-long sham treatment phase followed by a 3-week-long acupuncture treatment phase (4 dogs). Owners were blinded to the treatments administered during the second and third phases of the study.
During the control phase, force plate gait analysis was performed at weekly intervals a minimum of 3 times. Dogs were trotted over a commercial force platea by 1 of 2 trained investigators (PDM, MYP), and GRF data were collected with standard software.b Trials were considered valid when the dog's velocity was between preset limits of 1.6 and 1.9 m/s; the acceleration was ± 0.5 m/s2 (measured via photocells); and only the ipsilateral forelimb and hind limb struck the force platform completely, which was confirmed by 2 investigators observing the trial. Ground reaction forces for all 4 limbs were measured; for each force, the mean value for the first 5 valid trials for each limb was used in data analysis. All forces were recorded as a percentage of the dog's body weight.
During the acupuncture treatment phase, ESA was performed with a commercial unitc once weekly for 3 treatment sessions. Each treatment session lasted 20 minutes. Acupuncture needles (0.22 × 25 mm) were inserted at the TH13, TH10, LU5, PC3, PC6, HT7, baihui, GB33, GB34, BL10, and GV14 points. Needles were stimulated beginning at a frequency of 2 Hz, and stimulation frequency was increased until local muscle contraction was observed; stimulation frequency was then maintained at that level for the remainder of the treatment session. The 8 dogs with bilateral elbow OA were treated bilaterally, whereas the 1 dog with unilateral elbow OA was treated only on the affected side.
During the sham treatment phase, a sham treatment was administered once weekly for 3 sessions. The sham treatment consisted of placement of a single, unstimulated dermal needle at the top of the dog's head, away from any acupuncture point recognized by the International Veterinary Acupuncture Society.
All acupuncture and sham treatments were performed by 1 of 2 authors (MT, JB), who were blinded to results of force plate gait analyses. All force plate analyses were performed by a single author (ASK), who was blinded to treatment.
During the acupuncture and sham treatment phases, force plate gait analysis was performed on all dogs before and between 1 and 3 hours after administration of acupuncture or the sham treatment. Prior to each force plate gait analysis during the control phase and prior to each treatment session during the acupuncture and sham treatment phases, owners were asked to complete a form regarding clinical condition of their dogs. On the form, owners were asked to indicate, on a 10-cmlong line, the severity of pain for the dog at a walk, after it was playing, and when it was getting up and down and the dog's general attitude and well-being. In addition, owners were asked to provide 1 or 2 sentences describing their dogs' activity level and summarizing their dogs' performance during the preceding week. Owners were required to complete and submit new forms each week so they could not compare their responses to previous weeks' responses. At the end of the study, each owner was asked to guess during which 3-week period his or her dog received acupuncture versus the sham treatment.
Statistical analysis—Because dogs were examined on a weekly or nearly weekly basis, data collection sessions within subjects were ordered as visits 1 through 9. Data for the affected limbs of each dog were compared over time. Therefore, differences in severity of lameness between individual dogs were not factored into analyses of GRF data over time. Graphical presentations of the data were prepared with standard software,d and GRF data and VAS scores were analyzed with standard software.e Outcomes were modeled as repeated-measures data; linear mixed-model techniques were used.
Mean values for GRF data for each limb (left forelimb, right forelimb, left hind limb, and right hind limb) were analyzed separately. Only data collected during force plate gait analyses performed prior to each treatment session were used in these analyses, as analyses in which data from force plate gait analyses performed after each treatment session were included did not reveal any additional effects.
A linear mixed-models method was used for analysis of GRF data. First, a covariance structure was selected by modeling each of the 6 forces as a function of visit with a subject-level random intercept and random treatment coefficient for each limb. Covariance structures that were considered included independence, compound symmetry, autoregressive, and unstructured, and the most appropriate covariance structure was selected on the basis of the Bayes information criterion, with lower criterion value indicating a better model.24 Once a covariance structure was selected, a model with factors for treatment (control, sham, or acupuncture), visit number, and the interaction between treatment and visit number was created. The Wald test was used to test whether the interaction between treatment and visit number was significant, with the interaction term removed from the model if the P value was > 0.05. Treatment was determined to have a significant effect by examining P values obtained from the Wald χ2 test for the significance of the treatment factor coefficient.
Ground reaction force data were also analyzed by means of summary measures. For this analysis, 2 data sets were created. The first data set contained data obtained during the control phase and data obtained during the acupuncture treatment phase. The second data set contained data obtained during the control phase and data obtained during the sham treatment phase. For each data set, therefore, data for all 9 dogs obtained during the control phase were included. Data were graphed to allow visual assessment of any potential changes in GRFs over time.
For each dog, values for each of the 4 VAS scores obtained during each treatment session were tabulated, and scores were analyzed by use of linear mixed models containing factors for treatment, visit number, and the interaction between treatment and visit number. Because owners are likely to have heterogeneous interpretations of pain, a random intercept effect was included in each model to adjust for potential differences in scoring and VAS scores were treated as repeated measures. An appropriate correlation structure was selected by use of the Bayes information criterion. Significance of the interaction term was examined by use of the Wald test, and the interaction term was removed if P was > 0.05. Treatment was determined to have a significant effect by examining P values obtained from the Wald χ2 test for the significance of the treatment factor coefficient.
The binomial test was used to analyze owner responses when asked at the end of the study to guess during which 3week period their dogs received acupuncture versus the sham treatment. A value of P < 0.05 was considered significant.
Results
Force plate gait analysis—Linear mixed models for a treatment effect on GRFs converged to solutions with difficulty unless an independent covariance structure was assumed. Neither treatment (control, acupuncture, or sham) nor visit number was found to have a significant effect on peak vertical force, vertical impulse, peak braking force, braking impulse, peak propulsion force, or propulsion impulse for any limb (Figure 1).
Pain scores and owner assessments—For all 4 VAS scores, the Bayes information criterion indicated that an autoregressive covariance structure was most appropriate.
Analysis of the linear mixed models indicated that there was not a significant interaction between treatment and visit number for any of the 4 VAS scores, although for all 4 scores, P values (interaction of treatment × time) were close to the cutoff for significance (signs of pain at a walk, P = 0.080 [Figure 2]; signs of pain after playing, P = 0.067; signs of pain when getting up and down, P = 0.122; and general attitude, P = 0.063).
Eight of the 9 owners correctly identified when their dogs received acupuncture rather than the sham treatment, which was significantly (P = 0.04) higher than the proportion expected on the basis of chance alone. Weekly written comments from the owners during the acupuncture and sham treatment phases included statements to the effect that dogs had better attitudes, were less lame and more willing to exercise, and were overall improved, compared with the control phase. Some owners did not provide written comments during some weeks.
Scatterplots of peak vertical force expressed as a percentage of body weight in the left forelimb (LF), right forelimb (RF), left hind limb (LH), and right hind limb (RH) in 9 dogs with bilateral (n = 8) or unilateral (1) chronic elbow OA. Force plate gait analysis was performed approximately weekly during a 3-week control acclimation period and while dogs were receiving electrostimulated acupuncture or a sham treatment. Lines represent smoothed mean values (because not all visits occurred on the same day) during the control phase (solid line), acupuncture treatment phase (dashed line), and sham treatment phase (dotted line).
Citation: Journal of the American Veterinary Medical Association 228, 9; 10.2460/javma.228.9.1350
Scatterplots of peak vertical force expressed as a percentage of body weight in the left forelimb (LF), right forelimb (RF), left hind limb (LH), and right hind limb (RH) in 9 dogs with bilateral (n = 8) or unilateral (1) chronic elbow OA. Force plate gait analysis was performed approximately weekly during a 3-week control acclimation period and while dogs were receiving electrostimulated acupuncture or a sham treatment. Lines represent smoothed mean values (because not all visits occurred on the same day) during the control phase (solid line), acupuncture treatment phase (dashed line), and sham treatment phase (dotted line).
Citation: Journal of the American Veterinary Medical Association 228, 9; 10.2460/javma.228.9.1350
Scatterplots of peak vertical force expressed as a percentage of body weight in the left forelimb (LF), right forelimb (RF), left hind limb (LH), and right hind limb (RH) in 9 dogs with bilateral (n = 8) or unilateral (1) chronic elbow OA. Force plate gait analysis was performed approximately weekly during a 3-week control acclimation period and while dogs were receiving electrostimulated acupuncture or a sham treatment. Lines represent smoothed mean values (because not all visits occurred on the same day) during the control phase (solid line), acupuncture treatment phase (dashed line), and sham treatment phase (dotted line).
Citation: Journal of the American Veterinary Medical Association 228, 9; 10.2460/javma.228.9.1350
Mean VAS scores assigned by owners of 9 dogs with chronic elbow joint arthritis for severity of pain at a walk during a control acclimation period (solid line) and while receiving acupuncture (dashed line) or a sham treatment (dotted line).
Citation: Journal of the American Veterinary Medical Association 228, 9; 10.2460/javma.228.9.1350
Mean VAS scores assigned by owners of 9 dogs with chronic elbow joint arthritis for severity of pain at a walk during a control acclimation period (solid line) and while receiving acupuncture (dashed line) or a sham treatment (dotted line).
Citation: Journal of the American Veterinary Medical Association 228, 9; 10.2460/javma.228.9.1350
Mean VAS scores assigned by owners of 9 dogs with chronic elbow joint arthritis for severity of pain at a walk during a control acclimation period (solid line) and while receiving acupuncture (dashed line) or a sham treatment (dotted line).
Citation: Journal of the American Veterinary Medical Association 228, 9; 10.2460/javma.228.9.1350
Discussion
In the present study, ESA did not have any significant effects on severity of lameness, as determined by measurement of GRFs, or severity of pain, as determined by VAS scores, in dogs with chronic elbow OA secondary to elbow dysplasia. Thus, we were unable to provide objective data to support the hypothesis that ESA would be effective in treating lameness induced by elbow dysplasia in dogs.
Because of the considerable bias both for and against the use of acupuncture, the present study was designed as a randomized, controlled, crossover clinical trial. A particular problem involved in evaluating the efficacy of acupuncture is the lack of definitive guidelines or data regarding the most appropriate acupuncture points, needle lengths, duration and frequency of treatment, and type of electrical stimulus for treatment of individual conditions.25,26 Thus, it is possible that the frequency or duration of treatment used in the present study was insufficient, the acupuncture points that were selected were inappropriate for the individual patients, or the electrical stimulus and duration were not optimal. In addition, it is possible, but unlikely, that the sham treatment elicited a biological response and therefore may not have been an appropriate control.16 Finally, it is possible that force plate gait analysis was not performed and VAS scores were not collected at optimal intervals.
Two other important limitations of the present study were the low number of dogs enrolled in the study and the lack of a positive control treatment (ie, treatment with standard parenteral or local analgesics). Because of the lack of a positive control treatment, we could not definitively determine whether measurement of GRFs was sufficiently sensitive to detect alterations in gait associated with treatment. However, gait analysis has previously been shown to be sufficiently sensitive to detect treatment effects in dogs with OA treated with nonsteroidal anti-inflammatory drugs versus a placebo.17–20 Also, there is evidence that measurement of GRFs is a more sensitive method of evaluating lameness than is observation by a trained observer.27
There is a lack of consensus as to how well VAS and other pain scores can be used to distinguish pain in dogs.28–31 It is difficult to compare results of previous studies because of variability in how scores are assigned and who is assigning them. Recently, however, a study32 comparing results of a VAS questionnaire with GRFs identified 11 questions for which VAS scores correlated with GRF data. In the present study, we used 4 of these 11 questions, although we did not specifically attempt to correlate VAS scores for specific questions with measured GRFs.
The VAS scores may have been the most interesting result of the present study. Owners were blinded to whether their dogs received acupuncture or the sham treatment during their weekly visits but did know when the treatment part of the study was begun. Questionnaires were collected during each weekly visit so that owners could not compare VAS scores from one week to the next. Nevertheless, all but 1 owner provided higher ratings for their dogs during the middle of both the sham and the acupuncture treatment phases but not during the control phase. However, this might have been no more than a placebo effect.33 During the control phase, the dogs' interaction with people was limited to force plate gait analysis, whereas during the acupuncture and sham treatment phases, dogs were handled and subjected to human attention for at least 30 minutes. Although some dogs resisted initial needle placement, most appeared to enjoy the positive reinforcement (petting and verbal input) they received during acupuncture or sham treatment. Dogs were given more attention during acupuncture than during sham treatment sessions in the present study, which raises the question of whether attention itself or the duration or type of attention has any influence on the outcome of treatment for pain. In a study34 evaluating the effect of acupuncture on pulmonary function tests in horses with heaves, improvements in horses that received acupuncture were similar to those seen in horses that were only petted for the same duration.
Owners of dogs enrolled in the present study were asked at the end of this study during which 3 weeks they thought their dogs were receiving acupuncture versus the sham treatment. Surprisingly, 8 of the 9 owners guessed correctly, and all 8 of these owners indicated that they thought that acupuncture had been successful in treating their dogs' pain. These owners, therefore, viewed acupuncture as a successful treatment modality despite the lack of objective evidence to support its efficacy. It is possible that acupuncture might make dogs feel better as a result of endorphin release without significantly affecting the discomfort associated with OA, with the result that GRFs are unchanged. However, endorphin concentrations were not measured, and it is unclear whether acupuncture or the sham treatment would affect concentrations. In horses and sheep, a different ESA protocol had a variable effect on plasma endorphin concentrations and the association between increased concentration and cutaneous analgesia was not consistent.35–37
In conclusion, although we did not identify any significant effects in the present study, the limitations of the study combined with the perception by most owners that acupuncture had merit suggest that a larger trial with more dogs might have produced different results. Thus, additional studies are warranted.
ABBREVIATIONS
| OA | Osteoarthritis |
| ESA | Electrostimulated acupuncture |
| GRF | Ground reaction force |
| VAS | Visual analog scale |
Kistler Instrument Corp, Amherst, NY.
Version 7.20e, Sharon Software, Dewitt, Mich.
DiagnoMetre Basic, MED Servi-systems Canada Ltd, Sittsville, ON, Canada.
R 1.8.0, R Development Core Team. Available at: www.r-project.org/. Accessed Feb 27, 2006.
SAS, version 9.1, SAS Institute Inc, Cary, NC.
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