Biomechanical and histological variables differ by site but not by lameness in equine digital cushion samples from forelimbs.

The research study focused on comparing the biomechanical and histological properties of the digital cushion (a poorly understood part of the horse’s foot) in lame and non-lame horses. It found that these properties did not differ between lame and non-lame horses, but they differed based on whether the samples were taken from the palmar or dorsal aspects of the cushion.

Developing Sampling Technique and Study Objective

• The main purpose of this research was to create an effective sampling technique and investigate whether there are differences in the biomechanical and histological properties of the digital cushion (DC) between lame and non-lame horse forelimbs. Here, ‘lame’ refers to a horse’s inability to move normally due to injury or illness in its limbs.

Data Collection and Methodology

• Prior to euthanization for reasons not related to the study, both forefeet from horses with induced carpal lameness were radiographed (x-rayed) for data collection.
• These radiographs were used to guide the extraction of two midline digital cushion samples (one dorsal and one palmar) after death, using an 8mm biopsy punch.
• All collected samples were submitted to compressive testing to ascertain their elastic modulus – a measure of a material’s ability to resist deformation under load.
• For detailed understanding of the structure and makeup of the digital cushions, histological evaluations of the samples were also performed. The quantitative assessment included the levels of collagen, adipose (fat), ground substance (components of the extracellular matrix), elastic fibers, and blood vessels.

Results and Analysis

• The investigators used either student’s t-tests or Wilcoxon signed rank tests to compare the biomechanical and histological variables between dorsaland palmar digital cushion sites and between lame and non-lame limbs.
• No significant differences were found in the properties of lame and non-lame forelimb digital cushions, indicating that lameness does not influence the makeup or mechanical properties of the digital cushion.
• However, the dorsal digital cushion site showed a higher elastic modulus (greater resistance to deformation under stress) and greater proportion of ground substance compared to the palmar site. These different features may suggest different roles played by these sites within the digital cushion.
• Lastly, the study also demonstrated that it’s possible to collect adequate DC samples for both biomechanical and histological analyses – addressing a historical challenge in horse biomechanics research.