Abscess on the lateral epicondyle of the humerus as a cause of lameness in a horse.

This research article documents a case of a young horse that had a bone abscess or infection in its humerus—contributing to its lameness. The abscess, which was detected through a series of investigations and tests, was successfully treated through surgery, leading to the horse’s full recovery.

Case Presentation and Diagnosis

• The subject of the study was an 18-month old male Holsteiner breed horse which was brought in due to a lameness issue that had lasted for three months. Attempts to locate the cause of the lameness were initially unsuccessful due to the lack of visible abnormalities in radiography and the ineffectiveness of anesthesia.
• However, a nuclear scintigraphy test was performed which involves using radioactive isotopes that are taken up by the body’s tissues. This test revealed an unusual level of isotope absorption at the lateral epicondyle of the left humerus of the horse, indicating a problem in that area.
• Follow-up radiographs taken three weeks later revealed a 1.5-cm focal lucency (an area of increased radiolucency), surrounded by a 1.0-cm rim of necrotic, or dead, bone. These findings pointed towards a bone abscess or encapsulated osteomyelitis— a serious infection in the bone.

Treatment and Outcome

• The horse went through surgery for the bone abscess under general anesthesia. The procedure involved adopting a lateral approach to the affected site on the humerus. The abscess or cyst contents were removed through curettage (a surgical method for removing tissue by scraping or scooping), and the cavity that was left behind was packed with cancellous bone, a type of spongy bone, gathered from the tuber coxae.
• Postoperative cultures taken from the abscess identified the presence of a coagulase-negative Staphylococcusorganism was responsible for the infection.
• The horse showed dramatic improvement three weeks after surgery, appearing sound or free from lameness. Additionally, radiographs taken 10 months post-surgery showed ossification (formation of new bone) and adjacent sclerosis (hardening or scarring of tissues) at the surgical site, indicating successful healing.

Implications

• This case highlights that bone abscesses can be a cause of significant lameness in horses. The condition could exist as solitary cystic lesions in the long bones.
• The use of nuclear scintigraphy, as demonstrated in this case, can provide an early diagnostic capability for such conditions when other test results are inconclusive. This improves the chances of successful treatment.
• The research also provides evidence that curettage and cancellous bone grafting may be conductive surgical procedures for the effective treatment of bone abscesses.