716 AJVR, Vol 69, No. 6, June 2008 T he canine forelimb foot has 8 palmar MCP sesa- moid bones, with a pair associated with each of the 4 primary digits. These bones, numbered 1 through 8 in a medial to lateral direction, are anatomically sesa- moids of the interosseous muscles but are functionally associated with the digital flexor tendons and serve to provide a smooth surface over which the tendons can glide. 1–4 The 8 bones vary in size and shape, with sesa- moids 2 and 7 (and especially 1 and 8) being smaller and wider than the central bones 3 to 6. 1,3,4 The bones are roughly triangular in cross section with a flat abax- ial surface, a convex palmaroaxial (flexor) surface, and a dorsal articular surface. Because the dorsal surface is covered with articular cartilage and the flexor surface is mostly embedded in the thick fibrocartilaginous inter- sesamoidean ligament, only a limited amount of surface is suitable for the exchange of blood via the variably abundant vascular foramina that penetrate each bone. 3 A degenerative syndrome of the palmar MCP sesa- moid bones of large-breed dogs is a recognized disorder. It is characterized by fragmentation of the sesamoids and secondary degeneration of adjacent articular car- Vascular foramina of the metacarpophalangeal sesamoid bones of Greyhounds and their relationship to sesamoid disease Alison Daniel, BSc; Richard A. Read, BVSc, PhD; Martin A. Cake, BVMS, PhD Objective—To apply a novel technique and use the number and size (diameter and mean area) of vascular foramina to estimate potential blood supply in the metacarpophalangeal bones of dogs. Animals—28 Greyhounds. Procedures—The forelimb sesamoid bones of 23 dogs were obtained after dogs were eu- thanized. Bones were isolated and examined by scanning electron microscopy. The number, diameter, and area of vascular foramina were determined by image analysis. Arterial distri- bution was assessed by use of resin injection in the sesamoid bones of 5 additional dogs. Results—Sesamoids 2 and 7 had significantly fewer foramina (mean ± SE, 38.9 ± 2.5) and lower total foramen area (0.55 ± 0.04 mm 2 ), compared with values for other sesamoids (70.4 ± 3.3 foramina and 1.43 ± 0.06 mm 2 , respectively). Mean area and diameter of foram- ina of sesamoids 2 and 7 were also smaller in some regions. Comparison of the foramen distribution in dogs with sesamoid disease and clinically normal dogs revealed that for sesamoids 2 and 7, intact sesamoids from dogs with sesamoid disease had a significantly lower total foramen area (20 sesamoids from 9 dogs, 0.45 ± 0.04 mm 2 ), compared with sesamoids in clinically normal dogs (59 sesamoids from 14 dogs, 0.58 ± 0.03 mm 2 ). How- ever, for sesamoids other than 2 and 7, dogs with sesamoid disease had a significantly greater foramen area. Conclusions and Clinical Relevance—The restriction of vascular foramina in sesamoids 2 and 7 appeared to mirror the disease distribution and disease risk for specific dogs. (Am J Vet Res 2008;69:716–721) tilage 2,4 and almost exclusively affects sesamoids 2 and 7. 2,3,5–9 Clinical signs may include acute lameness (often of short duration), signs of pain elicited during joint manipulation, and joint effusion. In some affected dogs, lameness may become chronic or, alternatively, there may be no clinical signs. 8 This condition is described as being distinct from the traumatic fragmentation of the MCP sesamoids in dogs 2,6,9 ; however, pathogenesis of this degenerative syndrome of the sesamoids remains unclear. In other studies, investigators have proposed that the condition is caused by a congenital ossification anomaly, 6 degenerative joint disorder, 2 or secondary pressure from the digital flexor tendons. 3,5,10 Another possible cause of sesamoid disease in dogs has been proposed. 4 On the basis of the extent of bone necrosis evident during histologic examination of af- fected bones, investigators in that study 4 suggested that vascular compromise leading to bone ischemia may be the primary cause of the disease. However, regional osteonecrotic syndromes are, in general, poorly under- stood and rarely associated with any particular causative mechanism. Instead, osteonecrosis is often idiopathic and believed to be the final common outcome of a num- ber of putative conditions that lead to impairment or Received August 20, 2007. Accepted October 24, 2007. From the Department of Anatomy, School of Veterinary and Biomedical Sciences, Murdoch University, Perth, WA 6150, Australia. Address correspondence to Dr. Cake. ABBREVIATION MCP Metacarpophalangeal Unauthenticated | Downloaded 08/19/22 10:00 PM UTC