Subjective and objective gait analysis describing the effects of diagnostic analgesia in naturally occurring equine lameness

Abstract

INTRODUCTION: Lameness in horses is a clinical sign of musculoskeletal pain. Use of objective gait analysis could aid in the evaluation of lameness and monitoring the response to diagnostic analgesia in addition the traditional equine subjective clinical lameness exam.OBJECTIVE: The objective of this study was to describe the effects of diagnostic analgesia on the kinematic and kinetic variables in cases of naturally-occurring lameness and to describe the compensatory changes in the other limbs in response to diagnostic analgesia in the primary lame limb. METHODS: Eight horses from the teaching herd at the University of Minnesota were evaluated for lameness. Objective gait analysis was performed at the time of subjective exam. Kinematic evaluation was performed using a body mounted inertial sensor system (BMISS) at the trot and 2D sagittal plane extension of the fetlock at the walk. Kinetic evaluation was performed using an in-ground force plate at the walk and trot. Diagnostic analgesia with a local anesthetic was performed based on subjective evaluation. Subjective evaluation was repeated to determine if diagnostic analgesia improved lameness. Objective analysis was repeated after diagnostic analgesia and analyzed retrospectively after completion of the exam and diagnostic imaging. Diagnostic imaging of the identified region was performed after diagnostic analgesia was deemed successful for localizing the source of pain. RESULTS: All eight horses were found to have musculoskeletal pain. Diagnostic analgesia was performed in the forelimbs in four horses and in the hindlimbs of four horses. Two horses had lameness that was localized to feet of the forelimbs. One horse had lameness localized to a single forelimb fetlock and one horse had lameness localized to a single carpus. Three horses had lameness localized to the distal tarsal joints bilaterally and one horse had lameness localized to the medial femorotibial joints bilaterally. BMISS data showed alterations in head and pelvis asymmetry in response to diagnostic analgesia. Head asymmetry was decreased in the single forelimb lameness cases after diagnostic analgesia and head asymmetry switched between forelimbs after diagnostic analgesia of the lame limb in cases of bilateral forelimb lameness. Changes in asymmetry of the pelvis were variable in cases where hindlimb diagnostic analgesia was performed. There were increases in peak vertical force and vertical impulse at the trot in the lame limb in response to diagnostic analgesia. There was increase an in vertical impulse at the walk in the forelimb in response to diagnostic analgesia. There was an alteration in the distribution of force between the heel and midstance phases of the stride at the walk-in response to diagnostic analgesia in the hindlimb.