Bone Infarction

Case “Inspiration”

Sambeaux Brubaker5.5 year old MC RottweilerLeft TTO surgery 7/10/08Post-op recheck 8/5/08—not progressing as well as hoped

Left stifle/tibia radiographs madeIncreased mineral opacity in tibial medullary cavityDifferential diagnoses:– Bone infarct– Indolent osteomyelitis– Panosteitis

Thrall, 2007, Sebestyen, et al, 2000, and emedicine.com

Causes of Bone Infarction

Trauma (surgery e.g.-THR)IdiopathicSmall breed terrier/Sheltie dogsHumans—Hepatic lipidosis, Sickle cell disease, chronic steroid administration, pancreatitis

Human Bone Infarct secondary to Sickle Cell Anemia

Thrall, 2007 and Marcellin-Little et al, 1999

Other Differential Dx

Metastatic neoplasiaLymphomaPanosteitisInfectionOsteopetrosis/osteosclerosis

Sebestyen, et al, 2000

Bone Infarction

Time course– Initial signs non-specific, visible within a few

months (3-6 mos)—loss of trabeculae, smooth periosteal rxn, irregular increase in opacity of medulla

– More chronic—pathognomonic changes recognizable at 1 year—irregular, serpiginous, radiopaque lines in medullary cavity

– “Smoke in the chimney”

Sebesten, et al, 2000

Bone Infarction

Prevalence– Uncommon, assc with THR– 14% of femurs with femoral prostheses

(15/110) had infarcts in 2000 study– 8/53 (15%) had uncemented THR– 7/57 (12%) had cemented THR

Sebestyen, et al, 2000

Histopathology—what’s really going on in there?

Ischemic osteonecrosisCenter (radiolucent)—dead marrow and dead osteocytes, empty lacunaePeriphery (radiopaque)—dystrophic mineralizationPeriosteal reaction—woven boneDifferent from endosteal reaction, which is live bone proliferation!

Sebestyen, et al, 2000

Pathophysiology

Trauma to nutrient arteryNutrient artery relatively more proximal in dogs than humanstrauma during THRYounger dogs may be more affected because nutrient artery provides most of blood flow (older dogs use more periosteal vessels)No clinical signs, but possibility of malignant transformation

Marcellin-Little, et al, 1999

Malignant Transformation

Humans—osteosarcoma, fibrosarcoma associated with infarcted sites1999 report of dog with bilateral femoral infarcts—OSA developed unilaterally 5 yrs post-opTrack patients especially well if they develop infarcts!

ReferencesMarcellin-Little DJ, DeYoung DJ, Thrall ED, and Merrill CL. Osteosarcoma at the site of bone infarction associated with total hip arthroplasty in a dog. Veterinary Surgery 28: 54-60. 1999.Sebestyen P, Marcellin-Little DJ, and DeYoung BA. Femoral medullary infarction secondary to canine total hip arthroplasty. Veterinary Surgery 29: 227-236. 2000.Textbook of Veterinary Radiology, 5th ed. Thrall DE, ed. 2007. pp 306, 309. www.emedicine.com “Bone infarction”