Evaluation of the optimal plate position for the fixation of supraglenoid tubercle fractures in warmbloods

Summary

Objectives: To determine scapular cortex thickness, distal scapular bone density and describe the exact suprascapular nerve course to evaluate the best plate position for the fixation of supraglenoid tubercle fractures in horses.

Methods: Twelve equine cadaveric shoulders were examined with computed tomography. Computed tomography morphometry and density measurements (Hounsfield units [HU]) of the scapula were recorded. Statistical comparisons were made between the cranial and caudal aspects of the scapula. Dissection of each shoulder was performed and the suprascapular nerve course was described morphometrically and morphologically.

Results: The suprascapular nerve was found on the periosteum and embedded in connective tissue at the cranial aspect of the scapula. It ramified proximally and distally into the supraspinatus muscle, coursed caudo laterally at a median of 2 cm (1–2 cm) distal to the scapular spine and ramified proximally and distally into the infraspinatus muscle. The scapular cortex measurements (HU) cranially were significantly larger than caudally at most levels of the scapula. The bone density of the distal scapula cranially (651.3 ± 104.2) was significantly lower than caudally (745.7 ± 179.1).

Clinical significance: For surgical access to the supraglenoid tubercle, knowledge of the anatomy is important. It is easiest to avoid the suprascapular nerve at the most cranial aspect of the scapula, where it has not yet ramified. For a stable fixation, knowledge of the characteristics of the equine scapula, such as scapular cortex thickness, is important.

Keywords

Supraglenoid tubercle fractures - scapula - suprascapular nerve - plates - computed tomography - horse - plate fixation - equine

• References

• 1 Frei S., Fürst AE., Sacks M.. et al. Fixation of supraglenoid tubercle fractures using distal femoral locking plates in 3 Warmblood horses. Vet Comp Orthop Traumatol 2016; 29: 246-252.
• 2 Richardson DW.. AOVET course in Equine Advanced Techniques in Fracture Management. 2015. April 16-19. Columbus, Ohio, USA.:
• 3 Auer JA., Fürst AE.. Fractures of the scapula. Equine Vet Educ 2015. Dec 10 2015
• 4 Salomon F-V.. Bewegungsapparat. In: Salomon F-V., Geyer H., Gille U.. editors. Anatomie für die Tiermedizin [Anatomy for Veterinary Medicine]. 3^rd vol Stuttgart: Enke Verlag; 2015: 36-230.
• 5 Auer JA.. Principles of Fracture Treatment. In: Auer JA., Stick JA.. editors. Equine Surgery. 4^th ed Missouri: Elsevier Saunders; 2012: 1047-1080.
• 6 Leitch M.. A review of treatment of tuber scapulae fractures in the horse. Journal of Equine Medicine and Surgery 1977; 1: 234-240.
• 7 Stashak TS.. Lahmheit [Lameness]. In: Stashak TS.. editor. Adams Lahmheit bei Pferden [Adams Lameness in Horses]. 4th vol. Hannover: M. & H Schaper 2010; 486-785.
• 8 Salomon F-V.. Nervensystem, Systema nervosum [Nervous System, Systema nervosum]. In: Salomon F-V., Geyer H., Gille U.. editors: Anatomie für die Tiermedizin [Anatomy for Veterinary Medicine]. 3^rd Vol Stuttgart: Enke Verlag; 2015: 477-589.
• 9 Adams SB.. Surgical repair of a supraglenoid tubercle fracture in a horse. J Am Vet Med Assoc 1987; 191: 332-334.
• 10 Dart AJ., Snyder JR.. Repair of a supraglenoid tuberosity fracture in a horse. J Am Vet Med Assoc 1992; 201: 95-96.
• 11 Yamada K., Sato F., Higuchi T.. et al. Experimental investigation of bone mineral density in Thoroughbreds using quantitative computed tomography. J Equine Sci 2015; 26: 81-87.
• 12 Drum MG., Les CM., Park RD.. et al. Comparison of mean bone densities of three preparations of the distal portion of the equine third metacarpal bone measured by use of quantitative computed tomography. Am J Vet Res 2008; 69: 891-893.
• 13 Vallance SA., Spriet M., Stover SM.. Catastrophic scapular fractures in Californian racehorses: pathology, morphometry and bone density. Equine Vet J 2011; 43: 676-685.
• 14 Devine DV., Jann HW., Payton ME.. Gait abnormalities caused by selective anesthesia of the suprascpular nerve in horses. Am J Vet Res 2006; 67: 834-836.