Load redistribution after desmotomy of the accessory ligament of the deep digital flexor tendon in adult horses

Abstract

Summary An analysis of joint moments was used to study the biomechanical implications, load redistribution and kinematic pattern following desmotomy of the accessory ligament of the deep digital flexor tendon (AL) in adult horses. Recordings of 6 sound horses were made before and 10 days after desmotomy of the AL of the right forelimb at the walk and the trot. Kinematic recordings of the right forelimb and the left distal forelimb were made using the CODA-3 system. Kinetic recordings of the ground reaction forces in both forelimbs were made using a Kistler force plate simultaneously with the kinematic recordings. Radiographic localisation of the CODA-3 markers in both distal limbs allowed an analysis of coffin and fetlock joint moments, moment arms and forces in the digital flexor tendons. No transfer of load from the operated to the contralateral limb was found. In the operated limb the total joint moment of the coffin joint decreased substantially due to a reduced moment arm of the vertical ground reaction force component during the entire stance phase, while the fetlock joint moment decreased only slightly. To compensate for the loss of AL function, the superficial digital flexor tendon (SDFT) took a higher load during midstance, while at the end of the stance phase, the deep digital flexor tendon (DDFT) carried a higher load with a marked load peak just before heel off. While the compensation was adequate during midstance (no changes in maximal hyperextension of the fetlock joint), a prolonged hyperextension of the fetlock joint together with a rapid flexion at the start of the swing phase indicated that the DDFT was unable to compensate completely for the loss of AL function. It was concluded that the changes in total joint moments and increases in loading of the SDFT and DDFT allow locomotion without serious overloading of the compensating tendons following AL desmotomy.

Biomechanical effects of rocker‐toed shoes in sound horses

“…, but it confirms the results of Buchner et al(3) and Jansen et al(7). At 65% of the stance-phase, the hoof is positioned flat on the ground(Figure 3).…”

Hindlimb response to tactile stimulation of the pastern and coronet

“…Lateral radiographs of the hind hooves were taken with the hoof markers in place and with the horses standing on wooden blocks. During post processing, custom software was used to locate the centre of rotation of the distal interphalangeal (DIP) joint (Buchner et al. 1996b) and to determine hoof segment angulation based on the hoof marker positions.…”

Determination of passive mechanical properties of the superficial and deep digital flexor muscle-ligament-tendon complexes in the forelimbs of horses

“…[2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] Induced strains on the SDF tendon, DDF tendon, and AL DDF during phases of gait have been determined via measurement of localized stretch with implanted transducers [2][3][4][5] or estimation of overall stretch by use of geometric models and measured limb kinematics. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] Induced strains on the SDF tendon, DDF tendon, and AL DDF during phases of gait have been determined via measurement of localized stretch with implanted transducers [2][3][4][5] or estimation of overall stretch by use of geometric models and measured limb kinematics.…”

“…6,7 The passive resistance generated during stretch has been measured for isolated SDF 4,7-10 and DDF 4,7 tendons, as well as the AL DDF . 12, 13 The role of the accessory ligament in supporting the tendon loads has also been investigated for the AL SDF 14,15 and AL DDF . Alternatively, tendon loads have been estimated on the basis of each tendon' s contribution to joint moments calculated from kinematics and ground reaction force data.…”

“…7,11 With this information, forces can be estimated in each structure as the limb is loaded. 13 Although the roles of activated SDF and DDF muscles in overall limb compliance have been investigated, 16 data regarding the force-length properties of these muscles are limited. 12, 13 The role of the accessory ligament in supporting the tendon loads has also been investigated for the AL SDF 14,15 and AL DDF .…”