Left hind limb lameness in a 13-month-old spayed female German Shepherd Dog.

Companion Notes

Case report of medial epiphyseal artery occlusion in a dog resulted in osteonecrosis and collapse of the femoral head

Introduction on medial epiphyseal artery occlusion in the dog in this case report

- in dog in this report had infarcted cancellous bone and intertrabecular fatty marrow

- both underwent necrosis

- low oxygen tension due to the infarction resulted in the following:

- activation of mesenchymal stem cell (MSC)-derived stromal cells

- these began to form fibrous stroma to repair the necrotic adipose tissue

- activation of neovascular invasion of repair vessels

(from the surface of the bone)

- these activations together would form a cancellous bone-remodeling unit

- new vascular bed provides osteoclasts to remove dead bone

- activated MSC-derived stromal cells provide osteogenic repair cells

- recent studies show functional evidence for the presence of stem cells

- in the superficial layer of articular cartilage

Case report of a 13-month-old, 29.3 kg [64.6 lb] neutered sex:F large breed dog

- history of progressive lameness beginning at 5 months of age

- more severe on the left

- no history of trauma

- with acute worsening of lameness 2 days prior to presentation

- at referral for left hindlimb lameness

- physical examination: no significant findings

- CBC and serum biochemistry: no abnormalities

- orthopedic examination

- coxofemoral pain on hip extension, bilateral

- more severe on left

- muscle atrophy, thigh muscles, bilaterally

- most notable in biceps femoris and quadriceps muscle groups

- more extensive on left side

- indicative of chronicity

- lameness, left hindlimb, marked

- with palpable sub-luxation

- survey sedated hip radiography

- coxofemoral osteoarthritis with sub-luxation, bilaterally

- marked architectural changes of the following:

- proximal left femur

- femoral head

- acetabulum

- enthesophytes extended from cranial poles of the acetabula

- shallow acetabula with acetabular filling

- and dorsal acetabular rim wear

- flattened, incomplete left capital epiphysis

- no evidence of femoral head remnants in the acetabulum

- displaced left greater trochanter, medially

- proximal femoral medullary sclerosis

- left femoral diaphyseal cortical hypoplasia or atrophy

- due to chronicity

- increased density of cancellous bone

- medial two-thirds in the femoral neck

- proximal to a narrow defect in the medial cortex

- corresponding to the entrance of the epiphyseal artery

- increased medial density in femoral neck reflects the following:

(both can contribute to the increased bone sclerosis radiodensity)

- infarction of cancellous bone

- undergoing dystrophic mineralization

- infarcted marrow fat

- treatment

- left total hip replacement

- atypical gross findings in the exposed hip

- misshapen acetabular architecture

- flattened, subluxated femoral head

- overview

- subchondral collapse due to infarction seen only on left side

- possibly the greater instability on the left damaged the medial epiphyseal artery

(where artery entered the medial surface of the femoral neck)

- this occluded the epiphyseal blood supply causing infarction

- resulting in medial epiphyseal osteonecrosis remodeling of bone

- which progressed to the following:

- femoral head collapse

- proximal femoral sclerosis

- increased radiodensity

- morphologic diagnosis

- medial epiphyseal artery occlusion

- resulting in osteonecrosis and collapse of the femoral head

- secondary to subchondral necrosis

- outcome 6 months postop: limb had normal hip function

“In cases such as this, the definitive diagnosis of osteonecrosis could have gone undetermined after the total hip replacement if the specimen would have been simply discarded or presumed to be a different and more common diagnosis such as avascular necrosis of the femoral head (Legg-Perthes disease).”