Navicular Syndrome

Accession numbers 89605 and 89621

Christina Copple, DVM

Radiology Resident

Navicular Syndrome

• Syndrome = group of symptoms, collectively indicate the presence of an underlying abnormal condition

• Navicular Syndrome = chronically progressive, intermittent, bilateral forelimb lameness due to pain arising from the navicular apparatus– Can be unilateral and can occur in the hind limb

Navicular Apparatus

• Navicular bone – distal sesamoid bone

• Collateral ligaments

• Distal sesamoidean impar ligament

• Navicular bursa

• Distal digital annular ligament

• Deep digital flexor tendon - major compressive forces

• 4-navicular bone or distal sesamoid bone• 14- deep digital flexor tendon• 8- distal sesamoidean impar ligament• 16- navicular bursa• 15- distal digital annular ligament

• 3- navicular bone or distal sesamoid bone• 8- deep digital flexor tendon• 6- distal sesamoidean impar ligament• 9a/9b- navicular bursa (proximal and distal recesses)• 11- distal digital annular ligament

Risk Factors

• Concave or undulating proximal articular margin

• Degenerative changes of palmar fibrocartilage– Physiologic vs. Non-

physiologic

• Fibrillation of DDFT• Enthesophytosis and

mineralized fragments• Primary navicular bursitis

http://www.portugalweb.com/images/Portuguese-horse-500-1.jpg

History, Clinical Signs and Diagnosis

• Insidious onset, intermittent bilateral forelimb shifting leg lameness

• Usually 7-9 yrs of age• Pain when standing at rest, pointing toe• Lameness more apparent moving in a circle with lame

limb on inside• Usually positive response to palmar digital nerve blocks

and navicular bursa analgesia• * No pathognomic findings• Diagnosis = characteristic gait, palmar foot pain,

radiographic degenerative changes of navicular bone, rule-out other possible causes of lameness

Radiographs

• Proximal border & Extremities– Enthesophytosis of

extremities– Remodeling

• Distal border– Synovial invaginations– Small osseous fragments

• Flexor cortex– Cortical erosions– DDFT mineralization

• Medullary Cavity– Radiolucent cysts– Sclerosis

Nuclear Scintigraphy

• Patterns of increased radiopharmaceutical uptake commonly associated with palmar foot pain– Focal or generalized in navicular

bone– Navicular bone and distal

phalanx at region of insertion of DDFT

– Navicular bone and palmar processes of distal phalanx

– One or both palmar processes of distal phalanx

– Distal phalanx at sites of insertion of DDFT

CT & MRI

• Both more sensitive than radiographs to further characterize structural lesions of navicular bone, primary lesions of DDFT, identify degenerative changes of DIP articular cartilage

• CT: osseous changes and surface contour of lateral wings, evaluate articular flexor surface

• MRI: 3D spoiled gradient echo, 3D T2 gradient echo, STIR and fat-saturated 3D T2*– Soft tissues lesions – fibrocartilage changes,

distension of navicular bursa, DDFT or impar ligament changes, abnormal bone marrow within navicular bone

SNORT

• 16 yr old Quarter horse gelding

• 3yr history of left forelimb lameness

• Previously diagnosed with bilateral navicular “disease”

• PE: right forelimb lame 3/5, positive on flexion tests in both forelimbs

Left Dorsolateral-Palmaromedial oblique

Left Dorsomedial-Palmarolateral oblique

Left palmaroproximal-palmarodistal oblique

Right palmaroproximal-palmarodistal oblique

Right dorsolateral-palmaromedial oblique

Right dorsomedial-palmarolateral oblique

Left STIR Right STIR

References•Ross, Mike W., DVM and Sue J. Dyson, MA, VetMB, PhD, DEO, FRCVS. Diagnosis and Management of Lameness in the Horse. Saunders. Philadelphia, PA. 2003.•Thrall, Donald E., DVM, PhD. Textbook of Veterinary Diagnostic Radiology. 5th ed. Saunders. St. Louis, MO. 2007.•Stashak, Ted S., DVM, MS. Adams’ Lameness In Horses. 5th ed. Lippincott Williams & Wilkins. Philadelphia, PA. 2002.•Denoix, J.-M. The Equine Distal Limb Atlas of Clinical Anatomy and Comparative Imaging. Iowa State University Press. Ames, IA. 2000.•Pasquini, Chris, DVM, MS, Tom Spurgeon, PhD, and Susan Pasquini, DVM. Anatomy of Domestic Animals Systemic and regional approach. 7th ed. Sudz Publishing. Pilot Point, TX. 1996.