Evaluation Using Hoof Wall Strain Gauges of a Therapeutic Shoe and a Hoof Cast with a Heel Wedge as Potential Supportive Therapy for Horses with Laminitis
¨ HH, FLORIAN BUCHNER, DVM, PhD, JURGEN HALLER, GERHARD WINDISCHBAUER, DI Dr
Objective—To evaluate using strain gauges, a hoof cast with heel wedge, and atherapeutic shoe with unsupported toe for their effectiveness in redistribution of load from the dorsal hoof wall. Study Design—In vitro biomechanical study. Sample Population—Twenty forelimb specimens. Methods—Rosette strain gauges were placed on the dorsal and lateral hoof wall of 20 normal shaped hooves. Limbs were loaded vertically using a tensile testing machine with a 1 Hz sinusoidally cyclingload up to 3000 N during 15 seconds. Mean values of principal strain and direction at 2500 N load were calculated for 3 experimental conditions (unshod, therapeutic shoe with unsupported toe, and hoof cast with heel elevation) and tested by ANOVA (Po.05). Results—Vertical limb loading in an unshod hoof leads to a biaxial compression of the dorsal wall with high longitudinal compression (e2 ¼ À1515mm/m). Principal strain at the dorsal wall (e2) was decreased by 23% with the therapeutic shoe and by 59% with the hoof cast. On the lateral hoof wall principal strain was unchanged with the shoe, but increased by 34% with the cast. Conclusions—Strain measurements indicate unloading of the dorsal hoof wall by both methods with the cast being more effective than the shoe. Clinical Relevance—The hoofcast with wedge offers substantial unloading of the dorsal wall, but increases load on the quarter. Therefore a hoof cast would likely be most helpful in acute laminitis when palmar structures can still bear load. The therapeutic shoe offers rehabilitation and regrowth of the dorsal wall without increased load on the quarter wall. r Copyright 2005 by The American College of Veterinary Surgeons Keywords: horse, laminitis, strain gauges, hoof wall, laminitis therapy, therapeutic shoe, hoof cast.
INTRODUCTION QUINE LAMINITIS is a complex systemic disease that involves digital vascular changes, ischemia, and necrosis of the dermal lamellae.1 Lamellar damage results in a breakdown of the interdigitating system of primary and secondary lamellae with subsequent separation of the distalphalanx from the hoof wall.2 Depending on the
extent of damage and the biomechanical forces acting on the hoof, the distal phalanx can ‘‘sink’’ (vertical displacement) or ‘‘rotate’’, or the hoof capsule can slough completely. Acute laminitis is an emergency that requires systemic treatment and specific management of the feet.3,4 Therapy is based on intensive medical care that tries to eliminateor minimize any causative factor, provide analgesia, and limit damage at the lamellar junction.2,4–6
From the Department for Small Animals and Horses and the Department for Natural Sciences, University of Veterinary Medicine Vienna, Vienna, Austria. Supported by a grant of the Hochschuljubilaeumsstiftung H-83/99, Vienna, Austria. Address reprint requests to Dr. HHF Buchner DVM, PhD, Departmentfor Small Animals and Horses, University of Veterinary Medicine Vienna, Veterinaerplatz 1, A-1210 Vienna, Austria. E-mail: Florian.Buchner@vu-wien.ac.at. Submitted October 2004; Accepted January 2005 r Copyright 2005 by The American College of Veterinary Surgeons 0161-3499/04 doi:10.1111/j.1532-950X.2005.00023.x
HANSEN ET AL
Hoof support that reduces stress on the dorsal hoofwall is considered important to prevent or minimize progression of lamellar injuries, prevent compression of the circumﬂex artery and solar plexus, and reduce pain.7 In addition to shoe removal and stall conﬁnement on deep bedding, there is general agreement that heel elevation to decrease the pull of the deep digital ﬂexor tendon (DDFT) and support of the palmar areas of hoof and frog to...