1. Introduction
Osteoarthritis (OA) is a common cause of lameness and poor performance in horses.Lameness due to OA is the most common cause of early retirement of pleasure and performance horses.1,2 The use of viscosupplementation, like intra-articular injections of hyaluronic acid, has been implemented in the treatment of OA in humans3, as well as in animals, especially horses.4 PAAG (Polyacrylamide hydrogel)5, a is recently used to intra-articularly treat OA in horses; however, no prospective study on its efficacy has been reported. The purpose of the present study was to investigate the effect of a PAAG in improving clinical signs of OA in the fetlock or carpus.
2. Materials and methods
Thirty three horses older than 2 years with a confirmed symptomatic OA in only one joint (fetlock or carpus) based on clinical evaluation, intra- articular anesthesia and imaging (radiography, MRI or arthroscopy) have been included in this clinical trial. Horses were injected with 2 ml of PAAG in the affected joint and were followed up at 1, 3, and 6 months. Efficacy of the treatment was evaluated by clinical assessment of lameness in the affected joint. Data relating to the following variables: age, sex, breed, type of activity, joint and leg involved, lameness duration, previous joint treatment, lameness scoring at baseline and at 1, 3, and 6 months, joint effusion scoring, radiographic scoring, and owner assessment were recorded. Safety assessment of the joint was also evaluated through recording of any adverse reaction following joint injection. Statistical variables potentially associated with the outcome measure ”lameness scoring” were analyzed using generalized linear mixed model for ordinal regression with random effect of horse (Variance component: 5.25; Likelihood ratio: 27.51, with p < 0.0001). A P value of <0.05 was considered significant. It was hypothesized that PAAG would significantly decrease the lameness scoring in the OA affected joints.
3. Results
The study population included 25 Warmbloods, 2 Thoroughbreds, 2 Trotters, and 4 miscellaneous breeds. There were 13 females, 13 geldings and 7 intact males. The age ranged between 2 and 16 years with an average age of 9.5 years (s.d. ± 4.3 years). Horse activities were: dressage (13), show jumping (10), racing (4) and miscellaneous activities (6). Radiographic score of OA before the treatment was 1 (mild), 2 (moderate) and 3 (marked), in 13 (39.4%), 8 (24.3%) and 12 (36.3%) horses respectively. In addition, 17 of 33 horses (51.5%) underwent MRI or arthroscopy, or both modalities for the diagnosis of OA. Before treatment, the proportion of horses with lameness score 1, 2, 3 and 4 was 27.3%, 33.3%, 33.3% and 6.1% respectively. The estimated proportion of horses with lameness improvement at 1, 3, and 6 months was 81%, 88% and 87% respectively. The estimated proportion of sound horses at 1, 3 and 6 months was 53%, and 58% and 70% respectively.
For the statistical model used, only the time point (p<0.0001) and the activity (p=0.0005) variables were significant. There was a statistically significant decrease in lameness score from baseline to 1 month, and from 1 to 3 months (Odds ratios= 214), but lameness score was constant from 3 to 6 months. At 6 months, 81.8% of the owners were satisfied or highly satisfied with the outcome of the treatment, whereas 18.2% of the owners were slightly satisfied or not satisfied with the outcome of the treatment. In addition, no side effect was observed in the treated joints.
4. Discussion and conclusion
The inclusion criteria in the present study were strict in order to maximize the validity of the results. Study limitations include, a low number of horses, a lack of comparison treatment, and a variety of clinicians performing the diagnostic. The statistical analysis of this study indicates a beneficial effect of PAAG, which, however, remains to be verified in a randomized clinical trial including a control group.
Preliminary results of this prospective study have shown that PAAG significantly alleviated lameness in OA affected joints, as assessed by standard veterinary lameness evaluation. No side effect was observed in the treated joints. PAAG is a promising treatment for symptomatic OA in horses; however its further evaluation is warranted.
Acknowledgments:
The authors would like to acknowledge the great help of Bente Brünner.
This study has been approved by the Danish Board for Animal Experimentation.
a Arthramid Vet, Contura International A/S, Søborg, Denmark.