The Journal of Bone and Joint Surgery (American) 86:948-955 (2004)
© 2004 The Journal of Bone and Joint Surgery, Inc.
Long-Term Results of Segmental Prosthesis Fixation by Extracortical Bone-Bridging and Ingrowth
Edmund Y.S. Chao, PhD1,
Bruno Fuchs, MD1,
Charles M. Rowland, MS1,
Duane M. Ilstrup, MS1,
Douglas J. Pritchard, MD1 and
Franklin H. Sim, MD1
1 Departments of Orthopedic Surgery (E.Y.S.C., B.F., D.J.P., and F.H.S.) and
Health Sciences Research (C.M.R. and D.M.I.), Mayo Clinic, 200 First Street
S.W., Rochester, MN 55905. E-mail address for F.H. Sim:
sim.franklin{at}mayo.edu
Investigation performed at the Departments of Orthopedic Surgery and
Health Sciences Research, Mayo Clinic, Rochester, Minnesota
In support of their research or preparation of this manuscript, one or more
of the authors received a grant from the National Institutes of Health
(NIH-NIC Grant CA 23751). None of the authors received payments or other
benefits or a commitment or agreement to provide such benefits from a
commercial entity. No commercial entity paid or directed, or agreed to pay or
direct, any benefits to any research fund, foundation, educational
institution, or other charitable or nonprofit organization with which the
authors are affiliated or associated.
Background: The technique of extracortical bone-bridging and
ingrowth fixation with a porous coating over the shoulder region of the
implant and augmentation by autogenous bone-grafting was introduced to improve
the longevity of implant fixation. The potential advantages of this technique
are that new-bone formation across the bone-prosthesis junction may share
stress and may prevent osteolysis by sealing off this critical region against
the infiltration of wear particles. The objectives of this study were to
examine the prevalence of stem-loosening with use of the extracortical
bone-bridging and ingrowth technique, the amount of bone formation over the
porous-coated region of this prosthesis, and the characteristics of bone
formation over the porous-coated region and adjacent bone.
Methods: Forty-three patients who had prosthetic reconstruction with
the extracortical bone-bridging and ingrowth technique from 1976 to 1990 were
included in this retrospective study. The mean length of follow-up was 9.7
years (range, two to twenty-one years). All but one patient were managed with
autogenous bone graft; five, with allograft and autograft; and one, with
allograft only. Extracortical bone formation was measured over a 2-cm length
of the porous-coated region of the prosthesis in four zones (the medial and
lateral aspects on anteroposterior radiographs and the anterior and posterior
aspects on lateral radiographs) and was reported as the percentage of the
total length (8 cm) covered by extracortical bone with a thickness of >1
mm. The Spearman rank coefficient was used to assess the correlation between
pairs of continuous variables.
Results: The final average percentage of the porous-coated region
that was covered by extracortical bone formation was 76% ± 34% for all
patients and anatomical sites of reconstruction. Use of bone cement was
associated with less bone formation (p = 0.04), and this value remained lower
at the final measurement (p = 0.06). One stem had aseptic loosening, but no
sign of osteolysis was found. The radiographic appearance of the bone
formation had stabilized at two years of follow-up. All patients with
allograft augmentation had greater bone formation. The amount of extracortical
bone formation did not differ in relation to the type of porous coating,
anatomical sites, pathological disorder, sex or age of the patient, or length
of reconstruction.
Conclusions: As shown by the low prevalence of stem-loosening (two
of fifty-six stems or one of forty-three patients), the use of the
extracortical bone-bridging and ingrowth fixation technique is associated with
improved stem fixation in segmental bone-replacement prostheses applied for
limb salvage. In the demanding biomechanical environment and with the risk of
stress and particle-related bone resorption, the extracortical bone-bridging
and ingrowth fixation is an attractive method to provide long-lasting implant
fixation.
Level of Evidence: Therapeutic study, Level IV (case
series [no, or historical, control group]). See Instructions to Authors for a
complete description of levels of evidence.

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J. Fukuroku, N. Inoue, B. Rafiee, F. H. Sim, F. J. Frassica, and E. Y.S. Chao
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J. Bone Joint Surg. Am.,
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