Effect of Flexibility of the Femoral Stem on Bone- Remodeling and Fixation of the Stem in a Canine...

Effect of Flexibility of the Femoral Stem on Bone-Remodeling and Fixation of the Stem in a Canine Total Hip

Arthroplasty Model without Cement*

by E. J. HARVEY, J. D. BOBYN, M. TANZER, G. J. STACKPOOL, J. J. KRYGIER, and S. A. HACKING

J Bone Joint Surg AmVolume 81(1):93-107

January 1, 1999

©1999 by The Journal of Bone and Joint Surgery, Inc.

Fig. 1 Photograph showing the titanium-alloy stem (left), the composite stem (right), and the modular metal-backed acetabular cup that were used in the total hip arthroplasty.

E. J. HARVEY et al. J Bone Joint Surg Am 1999;81:93-107


Fig. 2 Graph showing bending stiffness in the coronal plane for the titanium-alloy stems and the composite stems as well as the range for six canine femora at one-centimeter intervals from the

shoulder of the implant to the tip.



Fig. 3 Anteroposterior radiograph of the femora of Dog 2, made at six months, showing a close intramedullary fit of both implants.



Fig. 4 Anteroposterior radiograph of the femora of Dog 7, made at eighteen months, showing two-millimeter undersizing of both implants.



Fig. 5-A Anteroposterior radiograph of the femora of Dog 6, made at eighteen months, showing one-millimeter undersizing of both stems.



Fig. 5-B Paired serial transverse cross sections from Dog 6, showing more marked proximal resorption in association with the titanium-alloy stem (left) at the third and fourth intervals (two

middle pairs).



Fig. 6 Paired serial transverse cross sections from Dog 2, made at six months, showing a stable interface on both sides.



Fig. 7 Paired serial transverse cross sections from Dog 3, made at six months, showing a stable interface and slightly more cortical thinning in association with the titanium-alloy stem (left) at

the most proximal three intervals.



Fig. 8-A Scanning electron micrographs of a section from a titanium-alloy stem (Fig. 8-A) and a section from a composite stem (Fig. 8-B), from a dog evaluated at six months, showing bone

ingrowth arising from new endosteal-bone formation.



Fig. 8-B Scanning electron micrographs of a section from a titanium-alloy stem (Fig. 8-A) and a section from a composite stem (Fig. 8-B), from a dog evaluated at six months, showing bone

ingrowth arising from new endosteal-bone formation.



Fig. 9 Paired serial transverse cross sections from Dog 7, in which both stems were undersized by two millimeters, showing the difference in the tissue response between the stems.



Figs. 10-A and 10-B: Backscattered scanning electron micrographs of Dog 3, made at the third interval at six months.



Fig. 10-B There is a radiopaque line on the side with the composite stem (see Fig. 7).



Fig. 10-C Backscattered scanning electron micrograph of Dog 8, made at eighteen months, showing a prominent radiopaque line around a composite stem.



Fig. 11 Bar graph showing the percentage of intracortical porosity as a function of the type of stem and the interval at which the porosity was evaluated.



Fig. 12 Graph showing the percentage difference in the cortical area of the cross sections of the composite stems relative to that of the titanium-alloy stems at six and eighteen months.



Effect of Flexibility of the Femoral Stem on Bone- Remodeling and Fixation of the Stem in a Canine...

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