Articulaciones En Estres

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IN DEPTH:

PODIATRY

Functional Anatomy of the Equine Interphalangeal Joints
J.-M. Denoix, DVM, PhD

During locomotion, the interphalangeal joints undergo a variety of combined movements in the sagittal, frontal, and transverse planes, especially on uneven surfaces or during turns. Each movementinduces specific stresses on the articular surfaces and ligaments. Asymmetric elevation of one quarter induces collateromotion and sliding on the same side and rotation on the opposite direction. With this knowledge, the biomechanical causes of every injury of the interphalangeal joint structures can be determined, and a rational corrective shoeing procedure can be established. Author’s address:Clinique Equine, U.P. Anatomie, U.M.R. INRA ‘‘Biomecanique du Cheval,’’ Ecole ´ Veterinaire d’Alfort 7, avenue du General de Gaulle F-94704, Maisons-Alfort Cedex, France. ´ ´ ´ ´ 1999 AAEP.

1.

Introduction

2. A.

Materials and Methods Contact Articular Surfaces on Isolated Forelimbs

The distal forelimb of the horse undergoes high stresses during locomotion, particularly during unevenfoot bearing. The distal interphalangeal joint (DIPJ) is one of the most affected joints in the horse, the most influenced by hoof placement and orientation, and the most directly manipulated by hoof trimming and shoeing. The purpose of this study was to evaluate the extent and distribution of the contact articular surfaces within the interphalangeal joints under different circumstances of loading,limb attitude, and foot orientation, reproducing physiological stresses during natural gaits and jump and sport exercises. It was also to correlate experimental findings on isolated limbs and live horses with clinical applications and corrective shoeing.

Forty-nine isolated thoracic limbs of adult horses and foals were used in the study. These limbs were sectioned at the mid-forearm to preservethe stay apparatus and especially the proximal insertion of the accessory ligament of the superficial digital flexor tendon (proximal check ligament). For each test limb attitude (landing, support, or propulsion) and foot orientation (horizontal surface or surface that slopes down from medial to lateral or lateral to medial) were carefully chosen to reproduce one of the physiological circumstancesof the horse weight-bearing limb during locomotion. The load was applied with a hydraulic workshop press and

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174

1999 9 Vol. 45 9 AAEP PROCEEDINGS

Proceedings of the Annual Convention of the AAEP 1999

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IN DEPTH: ranged between 200 and 1000 daN. As soon as the limb was positioned andloaded, lateromedial and dorsopalmar radiographs of the digit were taken and a colored solution of methyl violet (dilution 1%) was injected within the cavities of the distal and proximal interphalangeal as well as metacarpophalangeal joints, until distension of all synovial recesses was present. Then, an extensive lavage of the joints was performed to eliminate the excessive colored solution andprotect the contact articular surfaces from coloration during the ultimate phases of the procedure. The latter included removal of the load and joint disarticulation under water. Then the synovial membrane, joint capsule, and ligaments were removed and, for the precise experimental conditions used, colored as well as noncolored articular surfaces of contact were identified and photographed. For eachlimb the size and situation of the contact articular surfaces were correlated to the conditions of loading, limb attitude, and foot orientation.
B. Radiographic Studies on Live Horses

PODIATRY

surface dorsally on the glenoidal surface of P3 and distal sesamoid bone (DSB-navicular bone). In this limb attitude, because of the DIPJ flexion only the distal part of the DSB articular surface is...