Three-week history of non-weight bearing thoracic limb lameness
| A five-year-old female crossbreed pig presented for three-week history of non-weight bearing thoracic limb lameness, which was not responsive to anti-inflammatory medication. No known injury occurred, although she was housed with other pigs. On physical examination, there was also pain and swelling on palpation of the right thoracic limb.
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• Extending through the base of the right anconeal process is a thick (0.2cm) hypoattenuating (-4 to -352HU) band. The anconeal process remains normally positioned.
• The right elbow joint has a large amount of lobular periarticular and juxtarticular bone formation, worst along the anconeal process and caudal of the humeral condyle. The right elbow intracapsular soft tissues are thick and rounded. The elbow joint capsule is cranially bulging, and there is loss of intra-articular fat attenuation.
• The left elbow joint is congruent and the anconeal process is intact. Tiny osteophytes and enthesophytes are along the medial aspect of the radioulnar joint and the medial humeral epicondyle.
• Lameness is attributed to right fragmented anconeal process with severe degenerative joint disease and moderate to severe intracapsular swelling; acute exacerbation of chronic degenerative joint disease is suspected. Given the severity of intracapsular swelling, septic arthritis is possible. No osteomyelitis is detected.
• Mild left elbow degenerative joint disease
• The patient was discharged with dietary management (lower carbohydrate and no high fructose treats) with meloxicam. A surgery consult was recommended, but the patient was lost to follow up.
• The normal ossification of the porcine anconeal process is reported to be pyramidal from the proximal ulna (Bittergeko and Arnbjerg; Nakano et al.). The porcine anconeal process is normally ossified by 6-7 months (Bittegeko and Arnbjerg).
• In a postmortem study of lame adolescent boars, several (8/25) had a cartilage plate between the anconeal process and the ulnar diaphyses, and this was fractured in 7. Trauma was a proposed cause for formation of this cartilage plate (Nakano et al).
• Another study showed fragmented/separated anconeal processes in 15 pigs. These lesions had progressive healing with age (healed in all pigs at 25-26 months). These authors postulated that porcine anconeal process fragmentation occurs in the cartilaginous model, after which the cartilaginous fragments act as separate ossification centers (Bittegeko and Arnbjerg).
• Bittegeko SBP and Arnbjerg J. The sequelae of fragmented anconeal process (FAP) lesion in pigs: a radiologic, macroscopic, and histopathological investigation. J Vet Med 1996.
• Nakano et al. Observations of abnormalities and age-related changes in the anconeal processes of swine. Am J Vet Res 1982.