Does periosteal scraping of the third metacarpal bone reduce the incidence of ‘bucked shins’ in young Thoroughbred racehorses?

Abstract

The occurrence of bucked shins in young Thoroughbred racehorses in North America is high. Although an altered training regime has demonstrated a significant decrease in this condition, trainers can be opposed to altering something as fundamental as their training routine. Periosteal scraping of the third metacarpal bone (McIII) is a putative prophylactic technique used to prevent bucked shins; therefore, a study to investigate the validity of the procedure is warranted. To investigate whether prophylactic McIII scraping: 1) reduces the incidence of bucked shins in juvenile Thoroughbred horses at race speeds (breeze); and 2) allows increased cumulative breeze miles before the onset of disease. Nonrandomised prospective clinical study. One hundred and seventy yearling Thoroughbreds from one farm, under one trainer, were enrolled in this study over one training season; 85 horses were treated and 85 horses were control animals. Horses were observed for bucked shins over 5 cumulative breeze miles. The objectives were evaluated by comparing incidence rates and Kaplan-Meier plots. The incidence rate for bucked shins was 0.059 cases per breezed mile in the treatment group, compared with 0.103 cases per breezed mile in the control group. Comparison of Kaplan-Meier plots of breeze miles for the 2 groups demonstrated a significant difference between groups (P = 0.035). Horses that developed bucked shins following periosteal shin scraping breezed an average of 3.52 miles before the onset of disease, compared to 2.50 miles for horses not prophylactically treated (P = 0.005). Periosteal McIII scraping reduced the incidence rate of bucked shins. The procedure allowed treated horses to breeze greater cumulative distances before an incident but failed to prevent the disease over the long term. Further investigation into this commonly used prophylactic technique is required.