This text is taken from G.E. Fackelman, J.A. Auer, D.M. Nunamaker: AO Principles of Equine Osteosynthesis
Sagittal fractures of the proximal phalanx occur primarily in racing horses performing on solid footing such as turf or tracks with little overlying cushion [I1,2]. However, they can occur in any horse that can anchor its foot and create a torsional stress.
The fractures initiate at the sagittal groove of the proximal phalangeal articular surface and propagate distally [3, 4]. Fractures are identified in all stages, from those involving only the fetlock joint surface to those that bisect and possibly eventually lead to comminution. Most fracture planes extend from the proximal joint surface to the dorsal cortex and then down the palmar/plantar cortex, finally extending into the small medullary cavity in the distal third of the bone, bisecting the top two-thirds of the phalanx . Nearly all fractures have this component in common. More severe fractures then propagate from this medullary cavity laterally, medially, or distally and, with continued loading, may split the bone into multiple pieces.
3. Preoperative considerations
Minor fractures of only the proximal articular surface cause transient lameness and may require only exercise restriction to prevent crack proliferation and allow healing. If the fracture invades the dorsal or palmar/plantar cortex then the speed and quality of healing can be maximized by internal fixation.
High quality radiographic examination is necessary to accurately assess the full extent of the pathology present.
 Barr AR, Denny HR, Waterman AE, et al. (1988) Proximal phalangeal fractures in the horse. Vet Comp Ortho Trauma; 2:86.
 Ellis DR, Simpson OJ, Greenwood RE, et al. (1987) Observations and management of fractures of the proximal phalanx in young Thoroughbreds. Equine Vet J; 19:43--49.
 Fackelman GE (1973) Sagittal fractures of the first phalanx (P1) in the horse; Fixation by the lag screw principle. VM/SAC; 68:622.
 Gabel AA, Bukowiecki CF (1983) Fractures of the phalanges. Vet Clin North Am [Large Anim Pract]; 5:233- 260.
 Markel MD, Richardson DW (1985) Non-comminuted fractures of the proximal phalanx in 69 horses. J Am Vet Med Assoc; 186: 573.