An evaluation of prosthetic femoral head impact on acetabular articular cartilage in a hemiarthroplasty model.
OBJECTIVE
The quantitation of the impact of hemiarthroplasty currently involves clinical outcome measures and radiographic evaluation. This study used in vivo and in vitro means in order to evaluate articular cartilage changes following hemiarthroplasty in the sheep.


METHODS
Radiostereometric analysis (RSA) was utilized in order to quantitate migration (penetration) in vivo of the femoral head into the articular cartilage of the acetabulum. Dynamic stiffness of retrieved specimens was quantitated in vitro using a handheld device. Chondrocyte viability was assessed using live/dead cell staining and quantitated using image analysis techniques. Saffranin-O staining provided histological assessment of the cellular response to hemiarthroplasty.


RESULTS
RSA showed rapid penetration of the femoral head into the acetabular cartilage over six months. Significantly higher levels of dynamic stiffness were observed in the acetabula following hemiarthroplasty. Confocal imagery highlighted changes in chondrocyte distribution and morphology. A loss of metachromasia, fibrovascular tissue invasion and apoptosis were observed histologically.


CONCLUSIONS
RSA and measurement of the dynamic mechanical characteristics of cartilage provide a means of evaluating the development of degenerative articular cartilage changes in response to hemiarthroplasty.
Field
J R
JR
Comparative Orthopaedic Research Surgical Facility, School of Medicine, Flinders University, Bedford Park, South Australia, 5042, Australia. lantbruks@bigpond.com
Stanley
R
R
Appleyard
R
R
McGee
M
M
Callary
S
S
Nilsson
K
K
D000077:Acetabulum / Q000000981:diagnostic imaging / Q000473:pathology; D000818:Animals; D019644:Arthroplasty, Replacement, Hip / Q000662:veterinary*; D002358:Cartilage, Articular / Q000000981:diagnostic imaging / Q000473:pathology*; D002470:Cell Survival; D019902:Chondrocytes / Q000473:pathology*; D004195:Disease Models, Animal; D005270:Femur Head / Q000000981:diagnostic imaging / Q000473:pathology*; D006622:Hip Prosthesis; D007150:Immunohistochemistry / Q000662:veterinary; D008297:Male; D011859:Radiography; D012756:Sheep; D013997:Time Factors; D016896:Treatment Outcome