Diagnosis and Management of Tendon and Ligament Injuries of the Equine Foot

Introduction

Distal interphalangeal joint (DIPJ) arthropathy and navicular disease (podotrochlear syndrome) are well known conditions as primary causes of chronic foot lameness. Biomechanical stresses and a lot of different conditions such as chronic hoof umbalance or long toe-low hoof angle can be responsible for these conditions. Ligament and deep digital flexor tendon (DDFT) injuries are often considered in the differential diagnosis of foot problems without radiographic findings. Now a real definitive diagnosis is possible with ultrasonography and Magnetic Resonance Imaging (MRI). Collateral ligament (CL) injuries have occasionally been reported in the literature. Injuries of other ligaments of the foot may induce lamenesses which can be confused with a DIPJ arthropathy or a podotrochlear syndrome.

The purposes of this paper are to demonstrate the interest of ultrasonography in the differential diagnosis of foot injuries, to present the accuracy of this technique in the diagnosis of numerous ligament and tendon injuries in the foot and to discuss the limitations of this technique comparatively to MRI, a modality now available in some referral centers.

Materials and methods

All the clinical cases were examined clinically and were investigated with radiography ultrasonography. The most difficult cases have also been investigated with nuclear scintigraphy and/or MRI.
Ultrasound examination of the DIPJ was performed using dorsal and collateral approaches of the coronet using longitudinal and transverse sections made with 7.5 or 10 MHz linear probes. In some cases, 7.5 MHz convex or sector probes were also used to examine the 

distal insertion of injured collateral ligaments on the distal phalanx (P3). The hair of the coronet was clipped short and the skin was cleaned with hot water. Acoustic gel and a stand off pad were used to improve contact between the probe and coronet. On transverse sections, the probe was placed over the periopleum which represents a good acoustic window between the skin and hoof wall to obtain the best images.

Examination of the palmar aspect of the joint and podotrochlear apparatus (PTA: distal sesamoid bone-DSB and associated ligaments, DDFT and podotrochlear bursa) was performed with two approaches. The proximopalmar aspect of the joint was examined with a 7.5 MHz microconvex probe placed on the most distal part of the pastern. The hair of this area was clipped short and the skin was cleaned with hot water; no stand off pad was used. Images were done the toe being placed on the operator’s knee to induce extension of the DIPJ. Examination of the distopalmar aspect of the joint was performed with a 6MHz convex probe through the frog to image the PTA (DSB, distal impar sesamoidean ligament-DISL, DDFT) and distal surface of P3. To improve the contact with the frog, the most superficial part of the horn was cut to obtain a flat and clean surface over the body and dorsal part of central sulcus of the frog. [...]