Managing navicular bone fractures

Fractures of the navicular bone have been well described already many decades ago^1,2. The following configurations are observed: avulsion fractures of the distal margin, dorsal/frontal plane fractures, comminuted fractures and simple parasagittal fractures³ . While fragments at the distal margin are part of chronic degenerative navicular disease, dorsal/frontal plane fractures occur very rarely. The prognosis for comminuted fractures is poor. The most common configuration is a simple parasagittal fracture with the front limbs being more commonly affected. The fracture line usually goes through the narrowest part of the bone, about 1/3 of the length of the bone from lateral or medial. They can be mildly oblique and are usually not or only mildly displaced⁴ .

These fractures should not be confused with bi- or tripartite navicular bones⁵ .

Simple parasagittal fractures can occur as a pathological fracture secondary to degenerative chronic navicular disease but most commonly, they occur in healthy horses after a single traumatic event. They usually cause significant lameness. Conservative treatment options are rest which can be combined with application of a hoof cast/Nanric shoe/heel wedges or orthopaedic shoes that elevate the heels and have quarter clips. Healing takes usually 10-12 months but osseous union is rarely achieved. Horses treated conservatively usually remain chronically lame and have a guarded prognosis for use at pleasure riding level⁶ .

Palmar digital neurectomy can be used as a salvage procedure. However, results have been disappointing in a case series and the authors speculated that this surgery should not be performed before 6-12 weeks after the fracture occurred and that horses should only be used at a moderate level long-term^2,6 .

The poor results achieved with conservative management motivated equine surgeons in the 1980`s to attempt lag screw repair of simple parasagittal fractures despite the difficult approach and challenges concerning surgical navigation⁷. [...]