Fig 1.
Equine Metacarpophalangeal Joint.
Anatomy of the equine MCP joint.
Fig 2.
Phases of the stance and associated loading conditions at each phase.
Red arrows indicate vertical and horizontal acceleration and blue arrows indicate the ground reaction forces associated at each phase of the stance. The length of the arrow represents the magnitude of the acceleration and/or force at a given phase. Figure has been reproduced from Thomason and Peterson 2008 with permission.
Fig 3.
Loading on the MCP joint at Impact and Midstance phases of the stance.
Red arrows indicate loading on the distal end of MC3 from P1 under 1° impact [A] and the loading from both P1 and the PS under midstance [B]. Note the increased tension in the deep digital flexor tendon that occurs under midstance loading as indicated by the purple line.
Fig 4.
Mapped material stiffness on MC3 from μ-CT images.
Upper images, parasagittal slices at locations indicated by a line on corresponding lower image. Lower images, frontal slices at locations indicated by lines on corresponding upper images. Bone stiffness represented by colour mapping on the images and corresponds to the colour scale which is measured in MPa.
Fig 5.
Placement of pressure film within the MCP joint during ex vivo testing.
Diagram of the distal aspect of a third metacarpal. Blue areas indicate placement of pressure sensitive film within the MCP joint including P1 and PS contact area. Light blue area represents lateromedial film used to capture loading across the sagittal ridge.
Fig 6.
Regions of the distal end of MC3 used for the data analysis.
A) Regions dorsal to the transverse ridge associated with contact made by first phalanx (P1). (image credit and permission for reprint, Easton 2012) as the parasagittal groove (PSG) and medial (M) and lateral (L) condyles Areas included all data. B) Regionspalmar to the transverse ridge, associated with contact made by the proximal sesamoids (PS). as the parasagittal groove (PSG) and medial and lateral condyles (PS). Areas included all data. D: Dorsal; DLC, DMC: dorsolateral and dorsomedial condylar regions; DLPSG, DMPSG: dorsolateral and dorsomedial regions of the parasagittal groove; P: Palmar; PLC, PMC: palmar lateral and palmar medial condylar regions; PLPSG, PMPSG: palmar lateral and palmar medial regions of the parasagittal groove.
Table 1.
Difference in average von Mises stress by location between the selected model (moderate) and the fine and course resolution models.
Table 2.
Change in Average Dorsal Stress under Increased Bone Stiffness.
Fig 7.
Comparison of FEM and experimental pressures.
Distal end of MC3 of A) the FEM and B) the experimental pressure film indicating contact area and pressure (MPa) under impact loading at 3.55m/s (specimen in picture is for illustration purposes only and was not used in this study). B) The greater the intensity of the red staining on the experimental pressure film indicates a higher contact pressure at that location. Grey shading on FEM indicates an area that is over-limit based on magnitude measurable range of the pressure film.
Fig 8.
Comparison of OA and healthy FEM contact pressure.
Distal end of the third metacarpal on the healthy FEM and OA FEM indicating contact area and pressure (MPa) under impact loading at 3.55m/s.
Table 3.
Average Contact Pressure by Location of Experimental and Impact FEMs.
Table 4.
Maximum Contact Pressure by Location of Experimental and Impact FEMs.
Fig 9.
Comparison of OA and Healthy FEM surface stress.
Comparison of von Mises (MPa) surface stress (left) and a lateromedial slice (red line indicates area where slice was taken) of von Mises stress (right) between healthy and OA models under impact loading. M: Medial, L: Lateral
Fig 10.
Comparison of the average von Mises stress (MPa) at multiple locations on a lateromedial slice in the dorsal region of MC3 between the healthy and OA impact models.
DMC: Dorsal Medial Condyle, DMPSG: Dorsal Medial Parasagittal Groove, SR: Sagittal Ridge, DLPSG: Dorsal Lateral Parasagittal Groove, DLC: Dorsal Lateral Condyle
Fig 11.
Comparison of average von Mises stress (MPa) on a lateromedial slice in the palmar region of the third metacarpal across location between impact and static loading in the healthy and OA models.
PMC: Palmar Medial Condyle, PMPSG: Palmar Medial Parasagittal Groove, SR: Sagittal Ridge, PLPSG: Palmar Lateral Parasagittal Groove, PLC: Palmar Lateral Condyle.
Table 5.
Maximum Stress for Static FE Models.
Table 6.
Average Stress for Static FE Models.
Fig 12.
Comparison of average von Mises stress (MPa) on a lateromedial slice in the dorsal region of the third metacarpal across location between impact and static loading in the healthy and OA models.
DMC: Dorsal Medial Condyle, DMPSG: Dorsal Medial Parasagittal Groove, SR: Sagittal Ridge, DLPSG: Dorsal Lateral Parasagittal Groove, DLC: Dorsal Lateral Condyle.