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Deep digital flexor tendon force and digital mechanics in normal ponies and ponies with rotation of the distal phalanx as a sequel to laminitis
Author(s) -
McGUIGAN M. P.,
WALSH T. C.,
PARDOE C. H.,
DAY P. S.,
WILSON A. M.
Publication year - 2005
Publication title -
equine veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.82
H-Index - 87
eISSN - 2042-3306
pISSN - 0425-1644
DOI - 10.2746/0425164054223859
Subject(s) - laminitis , hoof , phalanx , anatomy , ground reaction force , navicular bone , rotation (mathematics) , interphalangeal joint , materials science , orthodontics , medicine , mathematics , physics , horse , biology , geometry , paleontology , kinematics , classical mechanics
Summary Reasons for performing study : Previous studies have implicated tension in the deep digital flexor tendon (DDFT) in the rotation of the distal phalanx (DP) after the breakdown of the dorsal laminae caused by laminitis. Howeveer, once the DP has rotated, the DDFT should become shorter, reducing the force it exerts on the DP. Objective : To compare DDFT force and ground reaction forces (GRFs) in normal ponies and ponies with rotation of the DP as a sequel to laminitis. Methods : Six normal ponies ( Group 1 ) and 6 sound ponies with 6‐13° of rotation of the DP in relation to the dorsal hoof wall ( Group 2 ) were assessed at trot using forceplate and motion analysis. The force in the DDFT was calculated by assuming that the extending moment at the distal interphalangeal (DIP) joint resulting from the GRF was equal to the flexing moment created by the force in the DDFT during the stance phase (inverse dynamics). Results : In early stance, the peak DDFT force (mean ± s.d.) in the normal ponies was 1.92 ± 1.63 N/kg. However, in Group 2 , the point of zero moment was palmar to the centre of rotation of the DIP joint for the first 40% of stance and hence DDFT force was zero. Force in the DDFT reached a peak of 10.00 ± 3.56 N/kg at 60.7 ± 5.6% of stance in Group 1 and 6.41 ± 1.37 N/kg at 79.2 ± 9.6% of stance in Group 2.Conclusions : DDFT force in Group 2 laminitic ponies was much reduced until late stance, when it neared normal values. Potential relevance : Further studies of ponies with rotation of the DP as a sequel to laminitis should assist farriery aimed at reducing the force in the DDFT through the breakover phase of stance to protect damaged dorsal laminae.