The accuracy of off-incidence ultrasonography as a method for scar-tissue detection in the equine superficial digital flexor tendon

Introduction Superficial digital flexor tendonitis is common amongst race and sports horses; accounting for 89-93% of all tendon injuries (Ely et al 2009) and potentially career ending. Diagnosis is achieved through on-incidence, transverse and longitudinal ultrasonography; shown to accurately represent tendon pathology (Marr et al 1993). Off-incidence, transverse ultrasound has been proposed for detecting collagen type III in the superficial digital flexor tendon (SDFT) (Smith 2010) however has yet to be validated. The study aimed to evaluate the accuracy of off-incidence, transverse and longitudinal ultrasonography for the detection and assessment of scar-tissue in the SDFT through a comparison of ultrasonographical, gross and histological findings. Materials and Methods Ten pairs of Thoroughbred cadaver forelimbs were assessed ultrasonographically, grossly and histologically at six recognised anatomical levels (Smith and Webbon 1994); scar-tissue within each method of assessment was assigned a value on a scale of severity. Mean scar-tissue values were calculated and compared using Wilcoxon’s Matched Pairs on SPSS version 18.0. Results Scar-tissue was visible through gross and histological examination, and through off-incidence, transverse and longitudinal ultrasonography. Anatomical levels proximal and distal to the mid-metacarpal region were found to present with the largest prevalence of scar-tissue and a bilateral tendency for scar-tissue pathology was found. No significant difference (P>0.05) was found between ultrasonographic and gross scar-tissue evaluation, ultrasonographic and histological evaluation and on gross and histological evaluation. Discussion and Conclusion The findings suggest that ultrasonography, in both the off-incidence, transverse and longitudinal views, is an accurate method for the detection of scar-tissue in the equine superficial digital flexor tendon. This research could aid further investigation into subclinical evaluation using ultrasonography as a method of preventing the occurrence of clinical injury and consequently helping to reduce the Thoroughbred wastage rates amongst the racing industry. Acknowledgments Thanks go to Andy Bathe and Alistair Foote at Rossdales Equine Hospital and Beaufort Cottage Laboratories and to John Baxter for provision of the sample. References Ely, E.R., Avella, C.S., Price, J.S., Smith, R.K.W., Wood, J.L.N. and Verheyen, K.L.P. (2009) Descriptive epidemiology of fracture, tendon and suspensory ligament injuries in National Hunt racehorses in training. Equine Veterinary Journal 41 (4): 372-378 Marr, C.M., McMillan, I., Boyd, J.S., Wright, N.G. and Murray, M. (1993b) Ultrasonographic and histopathological findings in equine superficial digital flexor tendon injury. Equine Veterinary Journal 25 (1): 23-29 Smith, R.K.W. (2010) Principles of musculoskeletal ultrasonography and normal anatomy of the metacarpus/metatarsus and pastern. BEVA Equine Musculoskeletal Ultrasound Course Proceedings