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Anton Fürst, Wayne McIlwraith, Dean Richardson

Executive Editor

Jörg Auer

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Metacarpal/-tarsal condyles: Description and preoperative considerations

1. Authors

Gustav E. Fackelmann

This text is taken from G.E. Fackelman, J.A. Auer, D.M. Nunamaker: AO Principles of Equine Osteosynthesis

2. Description

Fractures of the distal metacarpal and metatarsal condyles were among the earliest to be repaired by internal fixation [1]. Their relationships to the distal articular surface and to the long axis of the bone are relatively simple and technical problems are few.

In general, these fractures are racehorse injuries, are more common in Thoroughbreds than in Standardbreds, and usually affect the lateral condyle.

metacarpal tarsal condyles description and preoperative considerations

Fractures of the medial condyle may appear similar radiographically, but when examined more closely, they are far more extensive and require more aggressive treatment [2].

metacarpal tarsal condyles description and preoperative considerations

As with a number of other exercise induced fractures, condylar fractures appear to occur in stages. A common anamnesis includes: signs of repeated bouts of lameness associated with pain and swelling in the fetlock region; passive flexion of the metacarpophalangeal joint appearing painful; and, possible occasional point pain detectable in the distal metaphyseal region. These 2-3 day periods of lameness alternate with periods of apparent athletic soundness. Only after repeated radiographs are taken at different intervals and from various angles does the bony defect become visible [3]. There is scintigraphic evidence that there may be some predisposing (vascular) disorder of the distal metacarpus (see image) that precedes actual bony failure [4], as has been observed in humans [5, 6]. The gradual nature of the failure may be connected with prevailing loading characteristics, as has been demonstrated in experimental animals [7]. In describing the repair procedure below, the metacarpus will be used as an example. Mention will be made of any significant deviations applicable to the same fracture form
in the metatarsus.

metacarpal tarsal condyles description and preoperative considerations

3. Preoperative considerations

The most important factor specific to these fractures to be considered preoperatively is the presence of associated lesions. Bilateral fractures, fragmentation along the fracture line, especially of the flexor surface of the condyle [3, 8], and, axial fractures of the proximal sesamoid [9] warrant particular mention. Appropriate radiographic projections should be performed to rule out these additional injuries, as they will affect the details of the operative procedure and the prognosis for its outcome. If the instability has persisted for some time, a synovitis may be present, with the possible onset of degenerative joint changes. Such changes in an animal actively engaged in competition should prompt the surgeon to ask in particular whether the horse has received intraarticular therapy of any sort. Using the AO Documentation System, this information would have been gathered as one of the preoperative "checkpoints" [10].

If the fracture affects the medial condyle a more thorough radiographic, and perhaps scintigraphic, examin tion is indicated to elucidate the true extent of pathology. These fractures, especially when located in a hind limb, may spiral all the way to the proximal articular surface. This entire plane must be brought under interfragmentary compression, and the screws employed possibly protected by the application of a neutralization plate.

4. Bibliography

[1] Meagher OM (1976)
Lateral condylar fractures of the metacarpus and metatarsus in horses.
Proc Am Assac Equine Pract; 22: 147.

[2] Richardson OW (1990)
Third metacarpal/metatarsal fractures.
In: White NA, Moore IN, editors. Current Practice of Equine Surgery. Philadelphia: J.B. Lippincott Co., 617.

[3] Hornof WJ, O'Brien TR (1980)
Radiographic evaluation of the palmar aspect of the equine metacarpal condyles: A new projection.
Vet Radiol; 21: 160.

[4] Seherman HJ (1993)
Personal communication.

[5] Bullough PG, DiCarlo EF (1990)
Subchondral avascular necrosis: a common cause of arthritis.
Ann Rheum Dis; 49:4 12-420.

[6] Marks PH, Goldenberg JA, Vezina WC (1992)
Subchondral bone infarctions in acute ligamentous knee injuries demonstrated on bone scintigraphy and magnetic resonance imaging.
J Nuc/ Med; 33:5 16.

[7] Tomatsu T, Imai N, Takeuchi N, et al. (1992)
Experimentally produced fractures of articular cartilage and bone. The effects of shear forces on the pig knee.
J Bone Joint Surg {Br}; 74:457-462.

[8] Adams SB, Turner TA, Blevins WE, et al. (1985)
Surgical repair of metacarpal condylar fractures with palmar osteochondral comminution in two Thoroughbred horses.
Vet Surg; 14: 32.

[9] Barclay WP, Foerner JJ, Phillips TN (1985)
Axial sesamoid injuries associated with lateral condylar fractures in horses.
J Am Vet Med Assoc; 186:278- 279.

[10] Fackelman GE, Peutz IP, Norris JC, et al. (1993)
The development of an equine fracture documentation system.
Vet Camp Orthop Traumata; 6:47.