Unrecognized femoral fractures during cementless total hip arthroplasty in the dog and their effect on bone ingrowth.
Uncemented straight-stemmed proximally porous-coated femoral components were press fitted into the femoral canals of seven dogs using a rasp 0.5 mm smaller than the components (press-fit group). In seven other dogs the components were fit precisely into the femoral canals using a rasp that was the same size as the components (control group). Using this technique, all of the dogs in the press-fit group developed longitudinal fractures in the femoral cortex, while none of the dogs in the control group developed fractures. None of the fractures were recognized at operation. Two of the dogs in the press-fit group displaced the fractures at 1 week and were sacrificed. The other five dogs were bearing weight on their limbs and completed the 3-week experimental period. Follow-up radiographs of these femurs showed marked periosteal new bone formation, but did not reveal any fractures. Serial sections of these femurs showed longitudinal healing fractures in the anterior cortex. The fractures had an adverse effect on the bone ingrowth into the porous surface of the press-fit group compared to the control group without fractures, and the porous surface adjacent to the fractures was ingrown with fibrous tissue. The amount of bone ingrowth expressed as a percentage of the porous coating area measured, on average, only 3.9% in the press-fit group at 3 weeks compared to 5.6% in the control group--a statistically significant difference at P < .025. This experience in the dog illustrates the inherent risk of driving a larger femoral component into a smaller cavity prepared in the femur.(ABSTRACT TRUNCATED AT 250 WORDS)
Jasty
M
M
Orthopaedic Biomechanics Laboratory, Massachusetts General Hospital, Boston 02114.
Bragdon
C R
CR
Rubash
H
H
Schutzer
S F
SF
Haire
T
T
Harris
W
W
D000818:Animals; D004285:Dogs; D005260:Female; D005264:Femoral Fractures / Q000000981:diagnostic imaging / Q000209:etiology* / Q000473:pathology; D005269:Femur / Q000473:pathology / Q000648:ultrastructure; D006622:Hip Prosthesis / Q000009:adverse effects* / Q000379:methods; D008297:Male; D008855:Microscopy, Electron, Scanning; D016348:Osseointegration / Q000502:physiology*; D011474:Prosthesis Design; D011859:Radiography