Stress fracture of the palmar, distal cortex of the third metacarpal bone: A diagnostic challenge with a good prognosis.

The research explores the stress fracture in the third metacarpal bone in racehorses, its symptoms, common clinical traits and diagnosis challenges, and outlook after treatment, based on a retrospective analysis of cases from the Hong Kong Jockey Club.

Objective of the Study

• The study sought to identify the typical traits of the transverse stress fracture of the palmar cortex of the distal aspect of the third metacarpal bone (TSF PCD McIII) in racehorses. The objective was to record common clinical and radiological signs, along with the prognosis, given the fracture is poorly documented. The researchers formulated a retrospective hospital-based case series with follow-up of racing records.

Methods Used

• The researchers identified all cases of TSF PCD McIII diagnosed among racehorses in training at the Hong Kong Jockey Club between 2011 and 2019. They reviewed and documented signs from clinical records for each case, also listing findings from predefined radiological features.
• The team used descriptive statistics to indicate the age and training profile of horses, the clinical and radiological findings, and time taken for horses to return to ridden exercise.

Results Achieved

• Twenty-three cases of TSF PCD McIII were discerned. Noticeably, a majority (57%) of the cases had recently returned to training after a break or had just started. Furthermore, approximately a third (35%) had not yet initiated timed gallops at the time of their injury.
• Most horses (87%) manifested lame symptoms, with nearly 39% exhibiting severe lameness. Localised swelling of superficial soft tissues was reported in 65% cases.
• Pain on palpation of the distal McIII and in response to fetlock flexion was reported in 65% and 52% cases, respectively. Radiographic examination showed diffuse, localized increase in radiopacity, alterations in the outline of the bone periosteal surface, and outward displacement of the button of the splint bone as common features (70%, 67%, and 67% of all cases).
• Majority cases (61%) initially received a wrong diagnosis. However, post-treatment, most horses (about 78%) resumed training and racing after a median of 83 and 246 days.

Conclusions Drawn

• The study finds clinical notes vary between different cases, and radiographs were taken at different times. Horses commencing training are at risk of TSF PCD McIII, which presents with confusing clinical signs and subtle radiological findings.
• Despite initial misdiagnosis and confusion in symptoms, the long-term prognosis for the condition is favorable, as most horses could go back to training and racing after recovering.