Osteoarthritis is a chronic, progressive disease characterized by the degradation of articular cartilage with accompanying alterations of the joint, including sclerosis and thickening of subchondral bone, osteophyte production, and alterations of the synovium.1 Findings of early osteoarthritis research suggested that even in the first stages of the disease, changes in the articular cartilage were accompanied by changes in the bone.2,3
The role of subchondral bone in the initiation and progression of osteoarthritis has been examined. Specifically, alterations of the subchondral bone have been reported in later stages of osteoarthritis,4–6 and increased turnover of the subchondral bone has been shown to predict osteoarthritis progression (worsening) over time.7–9 As yet, it is uncertain whether the onset of these bony changes precedes or follows injury to the articular cartilage.10
Hip dysplasia results in subluxation of the hip joint and is a common cause of osteoarthritis in dogs11; thus, it is a model for naturally occurring disease. The use of this model facilitates the study of articular cartilage lesions and bone alteration in the incipient stages of hip joint osteoarthritis and has the advantage of being nonsurgically induced. Further, hip dysplasia in dogs is an important disease in veterinary medicine, being a common cause of osteoarthritis with associated pain and loss of function in that species.11
The use of CT for the assessment of BMD has been described.12 This technique has been applied to the elbow joint of clinically normal dogs.13 By use of a routine CT scan that includes a density-standard phantom in the field of view, the dipotassium phosphate eBMD of defined ROIs can be derived.12 Because a CT scan provides cross-sectional images, precise anatomic localization of an ROI is possible; therefore, this modality is ideal for localizing changes in the subchondral region of bone in a noninvasive manner.
The purpose of the study of this report was to compare the BMD of the proximal portion of the femur in dogs with and without early osteoarthritis secondary to hip dysplasia. We hypothesized that the subchondral bone density of the femoral head of dogs with hip joint osteoarthritis would be greater than that of dogs without hip joint osteoarthritis.
Equivalent bone mineral density
Region of interest
Orthopedic Foundation for Animals
Veterinary pentothal, Abbott Laboratories, North Chicago, Ill.
Diprivan, Zeneca Pharmaceuticals, Wilmington, Del.
Halothane, Halocarbon Labs, River Edge, NJ.
PennHIP, University of Pennsylvania, Philadelphia, Pa.
Picker PQS, Picker International, Cleveland, Ohio.
Cann-Genant K2HPO4 phantom (0, 50, 100, and 200 mg/mL), Boston, Mass.
Hydroxyapatite rod (800 mg/mL), CIRS, Norfolk, Va.
Voxel Q, Picker International, Cleveland, Ohio.
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