The third trochanter is a prominent tuberosity that is slightly curved in the cranial direction and is located on the lateral aspect of the proximal third of the femur. Its base provides insertion for the quadriceps femoris muscle, a strong extensor of the stifle joint, whereas the apex of the third trochanter provides insertion for the tendon of the gluteus superficialis muscle, which is mainly a flexor of the coxofemoral joint and internal rotator of the thigh.1 The superficial position (under the gluteofemoralis muscle) makes the third trochanter prone to traumatic injury such as falls, but it has been suggested that fractures may also be caused by avulsion of the tendon of the gluteus superficialis muscle.2 In the absence of physical findings and when the horse has no history of trauma, diagnosis can be difficult to achieve without nuclear scintigraphy. Lesions or injuries to the distal portion of the limb should be excluded before consideration of the pelvic or thigh regions as the source of pain.3
Reports of fractures of the third trochanter are uncommon,2–4 and to our knowledge, there is no report involving a group of horses that describes the clinical signs, imaging features, management, and outcome of horses with third trochanter fractures. The purpose of the study reported here was to determine the history; clinical, radiographic, ultrasonographic, and scintigraphic findings; management; and outcome of horses with third trochanter fractures. The hypothesis was that long-term outcome would be positive.
Increased radiopharmaceutical uptake
2. Geissbühler U, Busato A, Ueltschi G. Abnormal bone scan findings of the equine ischial tuberosity and third trochanter. Vet Radiol Ultrasound 1998; 39: 572–577.
3. Dyson SJ. Pelvic injuries in the non-racehorse. In: Dyson SJ, Ross MW, eds. Lameness in the horse. St Louis: Saunders, 2003; 491–500.
4. Butler JA, Colles CM & Dyson SJ, et al. The pelvis and femur. In: Butler JA, Colles CM, Dyson SJ, et al, eds. Clinical radiology of the horse. 2nd ed. Oxford, England: Blackwell Science, 2000;478–481.
5. American Association of Equine Practitioners. Guide for veterinary service and judging of equestrian events. Lexington, Ky: American Association of Equine Practitioners, 1991; 19.
6. Davenport-Goodall CL, Ross MW. Scintigraphic abnormalities of the pelvic region in horses examined because of lameness or poor performance: 128 cases (1993–2000). J Am Vet Med Assoc 2004; 224: 88–95.
7. Geburek F, Rotting AK, Stadler PM. Comparison of the diagnostic value of ultrasonography and standing radiography for pelvic-femoral disorders in horses. Vet Surg 2009; 38: 310–317.
8. Denoix JM, Audigie F. Imaging of the musculoskeletal system in horses. In: Hinchcliff KW, Kaneps AJ, Geor RJ, eds. Equine sports medicine and surgery. Basic and clinical sciences of the equine athlete. Philadelphia: WB Saunders Co, 2004; 161–187.