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ОглавлениеMetacarpal(-tarsal) condyles
Gustave E. Fackelman
7.2 Preoperative considerations
7.4 Surgical procedure
7.5 Postoperative care
7.6 Results
7.7 References
7.7.1 Online references
7.1 Description
Common anamnesis: repeated bouts of lameness with pain and swelling in the fetlock region, pain on passive flexion of the MC joint and point pain in the distal metaphyseal region.
Repeated radiographs and scintigraphy may be needed to make a definitive diagnosis.
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 (Fig. X7A). Fractures of the medial condyle may appear similar radiographically (Fig. X7B), but when examined more closely, they are far more extensive and require more aggressive treatment [2]. 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 (Fig. X7C) 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.
Fig. X7A: Follow-up radiographs show good fracture healing without periosteal proliferative change or degenerative joint disease.
Fig. X7B: The medial condylar fracture involves a great deal more of the shaft of the bone, and often “disappears” from radiographic views as it courses proximally.
Fig. X7C: A bone scan of the distal metacarpus in a horse showing typical premonitory signs may show intense uptake of isotope before any radiographic evidence of fracture has appeared.
7.2 Preoperative considerations
Check for additional lesions.
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 intra-articular therapy of any sort. Using the AO Documentation System, this information would have been gathered as one of the preoperative “checkpoints” [10].
Fractures of the medial condyle deserve further scutiny.
If the fracture affects the medial condyle a more thorough radiographic, and perhaps scintigraphic, examination 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 (chapter 1, Basic principles of fracture treatment).
7.3 Surgical anatomy
In nondisplaced lateral condylar fractures most, if not all, of the surgeon‘s orientation is based on soft tissue landmarks, the incision(s) being simple stab(s). These same landmarks will serve in displaced fractures, but assume less importance, since the articular surface will be directly visualized.
