Athletic Performance of Horses with Surgically Repaired Olecranon Fractures

Juvenile racehorses that have undergone internal fixation of an olecranon fracture have a favorable prognosis for maintaining athletic soundness and the ability to race. A significant difference was noted during 2- and 4-yr-old race seasons; however, during the 3-yr-old race year, minimal difference was detected in performance quality among operated horses and their maternal siblings.

1. Introduction

Olecranon fracture is a common diagnosis seen in foals and weanlings presented with forelimb lameness [1]. This fracture commonly results from traumatic injury, in which many different treatment options are available depending on the classification of the fracture and the degree of lameness present [2-6]. The most common surgical repair is the application of dynamic compression plates, tension band wires, and the Association for Osteosynthesis/Association for the Study of Internal Fixation (AO/ASIF) hook plate [2-8]. Conservative management in horses that need surgical attention yields a poor success rate in regards to bone healing and returning to athletic soundness [9]. The goals of this report were to quantitatively assess the racing performance of 20 juvenile Thoroughbreds (principals) who underwent surgical repair of olecranon fractures and to compare their performance with 90 maternal siblings (controls) who did not have olecranon fractures.

2. Materials and Methods

Complete medical records of foals that underwent internal fixation of olecranon fractures between January 1996 and December 2001 were reviewed. Signalment, radiographic findings, classification of the fracture, size and type of implant used, and follow-up results were recorded. Follow-up information was obtained through re-evaluation of horses on the farms, telephone communications, and racing records retrieved from the Jockey Club. Information recorded for the principals and controls included starting status; number of 2-, 3-, and 4-yr-old starts; career earnings; earnings per start; and starts percentile ranking number (SPR). Outcome by fracture classification was also determined. Surgical treatment was considered successful if the fracture completely healed, allowing the horse to maintain athletic soundness and start a race. Outcome was considered unsuccessful if the horse never started a race or was euthanized.

Null hypothesis stated there would be no difference in the athletic outcome as measured by starts and earnings among principals and controls. Means ± SD were calculated. Differences among the principals and controls were detected using a paired, two-tailed t-test; additionally, the equality of distributions of measured endpoints was compared among principals and controls using Χ2 tests. Results were considered significant when p < 0.05.

3. Results

Olecranon fractures in 7 fillies and 13 colts, ranging from 2 wk to 11 mo of age, were repaired using open reduction and an internal fixation technique. AO/ASIF classification of the fractures included type 1a (four horses), type 1b (one horse), type 2 (three horses), type 4 (seven horses), and type 5 (five horses) fractures. Internal fixation with a dynamic compression plate was used in 18 foals. Tension band wires were used in one foal, and an AO/ASIF hook plate was used in one foal. Eighteen of 20 fractures (90%) healed. Postoperative complications directly attributable to the implant devices were encountered in two colts, resulting in euthanization. Humeroulnar subluxation was detected in three foals secondary to radioulnar fixation. The growth disparity as a percentage of the radial epiphyseal width in these three foals was 8%, 22%, and 44%. The foals with 8% and 22% growth disparity pursued a racing career, whereas the remaining foal became a broodmare. Long-term follow-up was available for 18 foals. Of the original 20 principals, 5 fillies and 8 colts (65%) maintained athletic soundness and performed at the racetrack. Sixty-eight of 90 (75%) controls (43 fillies, 47 colts) pursued a racing career. Five principals (25%) raced as 2 yr olds, 10 (50%) raced as 3 yr olds, and 5 (25%) raced as 4 yr olds. In comparison, 39 controls (43%) raced as 2 yr olds, 64 (71%) raced as 3 yr olds, and 44 (49%) raced as 4 yr olds. Number of starts during each respective race season revealed a statistically non-significant difference among 2-, 3-, and 4-yr-old principal and controls. No statistical significant difference in earnings among 2- and 4-yr-old principals and controls was noted; however, a significant statistical difference in earnings was detected in the 3-yr-old race season. On average, principals earned less money than controls. Mean difference in earnings per start among principals ($2900 ± $9904) and controls ($5169 ± $12,039) was significant. Significant difference was evident in the mean SPR between principals (29 ± 32) and controls (50 ± 49).

Internal fixation of type 5 olecranon fractures resulted in superior overall racing performance in comparison with other olecranon fracture classifications. A significant statistical advantage was present with type 5 fractures in regard to starts, earnings, and SPR in the 2- and 3-yr-old horses; no horses sustaining type 5 fractures raced as 4 yr olds. Eighty percent of horses sustaining type 5 fractures started a race in comparison with 60% of horses undergoing surgery for other olecranon fracture classifications. Minimal difference was determined between type 1a, 1b, 2, and 4 fractures in 2-, 3-, and 4-yr-old horses when evaluating starts, earnings, and SPR.

4. Discussion

This report evaluated the racing performance of juvenile racehorses after internal fixation of olecranon fractures compared with a control population. Objective assessment of performance among juvenile racehorses can be difficult because of the number of variables involved in the racing industry. Three major characteristics were evaluated to quantitate performance in this study: the ability to train and start in a race (starting status), duration or longevity of race career (number of starts), and quality of performance (earnings, earnings per start, and SPR). The high success rate can be attributed to the juvenile horses represented in this study; the size and age of the patient are important factors when repairing olecranon fractures with any of the available implant techniques. Comparison of olecranon fracture classification revealed superior racing performance after repair of type 5 fractures. This association is because of fracture location, minimal displacement, and less articular involvement. Other fracture classifications are complicated by more difficult stabilization because of the variable degree of proximal fragment distraction and major articular involvement. Fractures involving the articular surface may be expected to have more long-term complications; the ensuing degenerative osteoarthritis that may develop with articular fractures may prevent horses from starting a race more so than the fracture configuration itself. Overall, approximately two-thirds of the principals started at least one race in their career. During the 3-yr-old race season, which is the most prestigious year in Thoroughbred racing, minimal differences in starts and earnings among principals and controls were detected. In conclusion, Thoroughbreds that have undergone internal fixation of an olecranon fracture as a juvenile have a favorable prognosis for maintaining their athletic soundness and the ability to race.