To compare intra-articular morphine or bupivacaine against no treatment following unilateral elbow joint arthroscopy using force plate analysis and pain scoring.
Thirty-one dogs were randomly allocated to receive 0•1 mg/kg intra-articular morphine, 0•5 mg/kg bupivacaine or no treatment following elbow arthroscopy. Force plate analysis, pain scoring and kinematic evaluation were performed before anaesthesia, 4 and 24 hours after surgery. Peak vertical force index, symmetry index, rate of loading, rate of unloading, stance time and range of motion were obtained from gait analysis. Pain scoring was performed every 4 hours and interventional analgesia (0•3 mg/kg methadone) was administered if necessary.
Of 29 dogs analysed, peak vertical force index (P<0•001), symmetry index (P=0•01) and rate of unloading (P=0•01) decreased significantly over time in each group; however, this was not affected by treatment. No significant differences were observed in stance time or rate of loading over time. Kinematic (range of motion) evaluation was not complete for all dogs. Pain scores increased significantly at both time points postoperatively in the no treatment group (P=0•007) and in morphine-treated dogs at 4 hours compared to baseline (P=0•03). For intra-articular bupivacaine significant increases in pain scores were not detected (P=0•28).
No benefit to intra-articular bupivacaine or morphine was detected using peak vertical force index from force plate analysis. Bupivacaine prevented increases in pain scores at both time points as did morphine at the 24-hour evaluation, compared to no treatment.