Computer-assisted gait analysis in equine orthopaedic practice: the case for inverse dynamic analysis.

The research article details the use of computer-assisted gait analysis in diagnosing lameness in horses, comparing its efficacy to traditional observational methods. The authors focus on the potential of inverse dynamic analysis using software and force platforms, implying it offers a significant advancement over older techniques.

Understanding Equine Gait Analysis

• Equine gait analysis has been a cornerstone of diagnosing lameness in horses for centuries, but modern techniques offer objective measurements missing from observational analysis.
• High-speed photography in the 19th century began the trend toward quantifiable equine gait analysis, but despite the advantages of objective information and increased spatio-temporal resolution, it has not replaced the clinician’s eye.
• The authors note the potential of catching small gait abnormalities with modern methods, as equine gait is highly reproducible and fixed at an early age.

Computer-Assisted Gait Analysis

• Computer-assisted gait analysis has been deployed successfully in human orthopedic practice, mainly because it faced less resistance from established observation-based methods.
• Kinematic variables like joint angles, angular velocities, and marker trajectories have been useful in quantifying gait, but they only offer essentially the same information available to the human eye.

Force-based Gait Analysis

• Kinetic variables, those related to forces, provide new additional insights into gait analysis, as forces are largely invisible to the human eye except through their effects on acceleration and deformation.
• Force platforms that measure forces between the hoof and ground have been used since the 1970s and can help quantify lameness. However, they don’t always provide good diagnostic information beyond identifying the affected limb.

Inverse Dynamic Analysis

• Inverse dynamic analysis takes gait analysis further by analyzing the locomotor system as a series of linked rigid segments, with hypothetical torque motors representing the muscle action at each joint.
• Joint torques are directly related to the combination of muscle forces acting across the joint, offering insights into muscle coordination and potential abnormalities.
• The authors caution that results from inverse dynamic analysis can be sensitive to data collection and analysis methods and may also be approximations due to embodied limitations and measurement errors.

Future Directions and Applications

• The authors assert that for similar applications to be adopted in equine practice, valid test protocols and normative data collection methods must be established.
• Finally, they acknowledge the contribution of the work by Clayton et al., stating it as the first attempt to use inverse dynamic analysis for the equine forelimb during a trot, an effort that could facilitate the development of effective clinical tools.