equis - Articles
Middle phalanx: fracture
Synonym(s): Split pastern
Introduction
- Cause: fast work with abrupt stops and turns, eg polo, Western performance horses or stock work.
- Signs: acute, moderate - severe lameness Musculoskeletal: gait evaluation; pain on manipulation Musculoskeletal: manipulative tests; pastern swelling, chronic lameness due to degenerative joint disease Musculoskeletal: osteoarthritis (joint disease).
- Diagnosis: clinical signs, radiography of pastern Forelimb: radiography Hindlimb: radiography, CT Computed tomography if comminuted fractures are being repaired, intra-articular anesthesia (forelimb Forelimb: joint anesthesia or hindlimb Hindlimb: joint anesthesia) in osteochondral chip fractures.
- Treatment: conservative - cast Musculoskeletal: external fixation - casts as a low cost salvage procedure. Removal of osteochondral fragments via arthroscopy Fetlock: arthroscopy. Internal fixation Bone: internal fixation - screws or PIP arthrodesis PIP joint: arthrodesis.
- Prognosis: good for osteochondral chips; guarded for other fracture.
Repair of comminuted fractures is challenging and comes with a poor-guarded prognosis for future performance.
Presenting signs
- Osteochondral chip fractures - poor performance.
- Uni-axial fracture of the medial or lateral palmar or plantar eminence - moderate to severe acute lameness.
- Bi-axial eminence fracture - non-weightbearing lameness, instability.
- Comminuted middle phalangeal fracture → non-weightbearing lameness, instability.
Acute presentation
- Severe lameness often non-weightbearing.
Age predisposition
- Generally adult animals in work.
Breed/Species predisposition
- Performance Quarterhorses Quarterhorse.
- Polo ponies Polo Pony.
Cost considerations
- Veterinary treatment, including surgery.
- Loss of use of horse during convalescence.
- Loss of horse.
Special risks
- Unstable biaxial palmar or plantar eminence or comminuted fractures require emergency stabilization Musculoskeletal: fracture - first aid before evaluation.
- Failure to stabilize fracture or use of perineural analgesia may result in the horse attempting to bear weight on an unstable fracture → movement of sharp bone fragments → substantial further soft tissue damage, eg digital sheath and deep digital flexor tendon lacerations.
Pathogenesis
Etiology
- Polo games.
- Western performance classes.
- Stock work.
- Free paddock exercise.
Predisposing factors
Specific
- Abrupt stops, with/without abrupt turns increases bending and torsional forces within the lower limb. Often performed by western performance horses and polo ponies which have the highest incidence of these fractures.
- Hindlimb fractures are up to three times more common than forelimb.
Pathophysiology
- Proximal interphalangeal joint (pastern) is high load, low motion joint.
- Distal articulation with distal phalanx and navicular bone (coffin joint) is high motion joint.
- Hyperextension of the proximal interphalangeal joint → insertions of the superficial digital flexor tendon, superficial distal sesamoidean ligament, and palmar and plantar ligaments of the pastern joint → tensile forces on palmar and plantar eminences → eminence fractures - vary in ize from small chips to those large enough for internal fixation.
- In addition, sudden pastern extension, eg sliding stops → distal displacement of the proximal phalanx → axial compression focused on the palmar or plantar aspect of the eminences → shear forces contribute to fracture. Eminence fractures are almost exclusively seen in the hindlimb:
- Uni-axial fractures → no compromise of proximal interphalangeal joint stability.
- Bi-axial fractures or complete avulsion of fibrous tissue attachments leads to instability and subluxation or luxation of proximal interphalangeal joint PIP joint: luxation. Fracture extends from near the junction of the middle and palmar/plantar thirds of the articular surface to the distal aspect of the palmar/plantar eminences, extending in the frontal plane across the bone. Attempts by the horse to weight bear on the injured limb may cause significant injury to the digital sheath and DDFT.
- Axial compression, bending and torsion forces at the same time, eg hoof fixed relative to digit → comminuted fracture. Use of shoes with caulks or rims may increase the risk of these injuries. These are the most common configuration of fracture in the middle phalanx (38 of 47 in one survey). Comminution is more common in the forelimb.
- Hyperextension of the proximal interphalangeal joint → partial avulsion with fibrous tissue attachments → osteochondral chip fractures. These are uncommon. Besides Quarterhorses Quarterhorse also noted in Thoroughbred Thoroughbred racehorses. Can be incidental and careful consideration of significance is required.
Timecourse
- Usually acute presentation.
Diagnosis
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Treatment
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Prevention
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Outcomes
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Further Reading
Publications
Refereed papers
- Recent references from PubMed and VetMedResource.
- McCormick J D & Watkins J P (2017) Double plate fixation for the management of proximal interphalangeal joint instability in 30 horses (1987-2015). Equine Vet J 49 (2), 211-215 PubMed.
- Radcliffe R M et al (2008) Arthroscopic removal of palmar/plantar osteochondral fragments from the proximal interphalangeal joint in four horses. Vet Surg 37 (8), 733-740 PubMed.
- Lescun T B et al (2007) Evaluation of transfixation casting for treatment of third metacarpal, third metatarsal, and phalangeal fractures in horses: 37 cases (1994-2004). J Am Vet Med Assoc 230 (9), 1340-1349 PubMed.
- Joyce J et al (2006) Use of transfixation pin casts to treat adult horses with comminuted phalangeal fractures: 20 cases (1993-2003). J Am Vet Med Assoc 229 (5), 725-730 PubMed.
- Galuppo L D, Stover S M & Willits N H (2000) A biomechanical comparison of double-plate and Y-plate fixation for comminuted equine second phalangeal fractures. Vet Surg 29 (2), 152-162 PubMed.
- Rose P L, Seeherman H & O'Callaghan M (1997) Computed tomographic evaluation of comminuted middle phalangeal fractures in the horse. Vet Radiol Ultrasound 38 (6), 424-429 PubMed.
- Schneider R K et al (1994) Arthroscopic removal of osteochondral fragments from the proximal interphalangeal joint of the pelvic limbs in three horses. JAVMA 205, 79-82 PubMed
- Welch R D & Watkins J P (1991) Osteochondral fracture of the proximal palmar middle phalanx in a Thoroughbred. Equine Vet J 23, 67-69 PubMed.
Other sources of information
- Watkins J P (2020) Fractures of the Middle Phalanx. In: Equine Fracture Repair. Ed: A J Nixon. 2nd edn. Wiley Blackwell, USA.