American Humane Association Veterinary Student Scientists Program Final Report – Summer 2012 Prevalence of and Predisposing Factors to Distal Phalanx Fractures in Foals Michelle L. Crupi Western University of Health Sciences College of Veterinary Medicine Abstract – The occurrence of distal phalanx (P3) fractures in foals is much more prevalent than previously thought.1,2 The fractures tend to heal quickly in foals, but it is uncertain as to the complications that these horses may subsequently experience. With greater than 30% of equine lameness estimated to stem from hoof problems, it is likely that these P3 fractures do lead to future complications.2,3 The following study evaluated the prevalence of P3 fractures in foals and examined corresponding distal limb and hoof capsule conformation over the period of one year. The distal forelimbs of 19 foals, age 8-25 weeks, were radiographed and photographed every 2 months over the period of one year. Distal limb and hoof capsule parameters were measured from the radiographs and photographs, and comparisons were made between fractured and non-fractured limbs as well as between the parameters measured and presence of fracture. Since this is an ongoing project, final results are not available at this time. However, our preliminary data has revealed that during the one year period, 12 out of the 19 radiographed foals (approximately 63.15%) had suffered at least one forelimb P3 fracture. Completion of the statistical analysis will reveal possible conformational predisposing factors to these fractures and will add to the understanding of the conformational development of the distal forelimb and hoof in growing foals. Goals/Objectives – The objectives for this study are: (1) to examine the prevalence of forelimb P3 fractures in foals within their first year of life; (2) to examine any correlation between the foals’ distal limb conformation and the incidence of P3 fracture; (3) to identify any additional predisposing factors to P3 fractures in foals; and (4) quantitative assessment of hoof capsule changes over the period of one year. Materials & Methods Horses – Nineteen healthy foals (4 Thoroughbreds, 7 Quarter horses, and 8 Arabians; 11 fillies and 8 colts) born between February 6 and May 29, 2011 were included in this study. All foals were housed and cared for by their owners at three different equestrian farms throughout Southern California. Farrier service for the foals varied between farms and none of the owners reported a history of lameness for any of the animals studied. All foals were weaned between 4 and 5 months of age. One Thoroughbred foal and the 7 Quarter horse foals were moved from their farms in January 2012, and subsequent data on these animals was not collected. The protocol for this study was reviewed and approved by the Institutional Animal Care and Use Committee (Western University of Health Sciences) and was performed in compliance with its guidelines. Radiography – Dorsopalmar (DP), lateromedial (LM), dorso 60° proximal-palmarodistal oblique (D60PrPaDiO), dorso 60° proximal 45° lateral-palmarodistal medial oblique (D60Pr45L-PaDiMO), and dorso 60° proximal 45° medial-palmarodistal lateral oblique (D60Pr45M-PaDiLO) views of both forelimb distal phalanges were taken approximately every 8 weeks with a portable digital radiograph machine. Both forelimb hooves were thoroughly cleaned prior to radiographs to minimize the chance of artifact. The DP and LM views were taken with both forelimbs placed on equal-sized wooden blocks. For the LM view a vertical metal rod marked the center of the dorsal hoof wall, with the proximal aspect of the rod positioned at the coronary band. For both the LM and DP views a metal pin (thumb tack) was placed at the apex of the frog on the sole of each front hoof. For the D60Pr-PaDiO, D60Pr45L-PaDiMO, and D60Pr45M-PaDiLO views, Play-doh™ was used to fill the sulci on the solar aspect of each front hoof to minimize the chance of air obstruction/artifact on the radiographs. In all views a radio-opaque marker was present at the level of the hoof to enable calibration of the image once imported into the appropriate image analysis software. Radiographs were reviewed by 3 clinicians for the presence of palmar process
fractures or other abnormalities of the distal phalanx. Using the image analysis software, 36 variables were obtained for each forelimb from the radiographs. Assessment of hoof conformation – Five photographs (dorsal, lateral, medial, palmar, and solar views) of each forelimb hoof were obtained by use of a digital camera approximately every 8 weeks, concurrently with the radiographs. A ruler was placed at the level of the hoof in each image to enable calibration. Using the image analysis software, a total of 31 conformational parameters were measured on each foot. Statistical Analysis – Statistical analysis of the data is currently being performed. It will enable the assessment of the growth and development of P3 and the hoof capsule. It will also enable the assessment of any correlation between the foals’ distal forelimb conformation and the incidence of P3 fractures. Results – Since this is an ongoing project, final results are not available at this time. However, our preliminary data has revealed interesting findings. Throughout a one year period, we observed forelimb P3 fractures in 12 out of the 19 radiographed foals (approximately 63.15%). Five of the 12 foals had bilateral forelimb P3 fractures, while the other seven foals had unilateral P3 fractures. Summary – This project will continue throughout the next few months. All of the data collection, image analysis, and conformational measurements have been completed. Upon completion of the statistical analysis, which will assess any correlation between the foals’ distal forelimb conformation and the incidence of P3 fractures, we will review our results and have a better understanding of possible predisposing factors to these fractures in foals. Our preliminary data shows that approximately 63.15% of the foals radiographed obtained forelimb P3 fractures. Further review of the radiographs by the clinicians will reveal even more exciting results, such as the amount of time it took on average for these fractures to heal. Completion of the statistical analysis will add to the understanding of the conformational development of the distal forelimb and hoof in growing foals. This study will aid in the clarification and understanding of the contributing factors to the P3 fractures in foals. The significance of determining any of these factors would lie in the preventative actions that would be taken to avoid these kinds of injuries in the future. References 1. Kaneps, A.J., S.M. Stover, T.R. O’Brien, R.R. Pool, and N.H. Willits. “Radiographic characteristics of the forelimb distal phalanx and microscopic morphology of the lateral palmar process in foals 3-32 weeks old.” Veterinary Radiology & Ultrasound 1995; 36.3: 179-187. Print. 2. Bhatnagar, Adrienne S, et al. “Hoof Conformation and Palmar Process Fractures of the Distal Phalanx in Warmblood Foals.” Journal of Equine Veterinary Science 2010; 30.7: 349-355. Print. 3. Floyd, Andrea E. and R.A. Mansmann. Equine podiatry. St Louis: WB Saunders Co, 2007; 141.