The Journal of Bone and Joint Surgery (American) 85:2365-2370 (2003)
© 2003 The Journal of Bone and Joint Surgery, Inc.
Extracortical Bone Bridging in Tumor Endoprostheses
Radiographic and Histologic Analysis
Michael Tanzer, MD, FRCSC1,
Robert Turcotte, MD, FRCSC1,
Edward Harvey, MD, FRCSC1 and
J. Dennis Bobyn, PhD1
1 Division of Orthopaedic Surgery, McGill University, 1650 Cedar Avenue, B5.159,
Montreal, Quebec H3G 1A4, Canada. E-mail address for M. Tanzer:
mtanz{at}canada.com
Investigation performed at the Division of Orthopaedic Surgery, McGill
University, Montreal, Quebec, Canada
The authors did not receive grants or outside funding in support of their
research or preparation of this manuscript. They did not receive 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: Aseptic loosening remains a major problem following
prosthetic replacement after resection of periarticular tumors. Attempts to
decrease the rate of loosening led to the introduction of a composite
segmental prosthesis in which the shoulder of the intramedullary stem is
porous-coated to allow extracortical bone bridging and bone ingrowth. The
purposes of this study were to determine the extent of extracortical bone
bridging around, and the amount of bone growth into, the porous-coated
shoulder of endoprostheses implanted following the resection of periarticular
bone tumors and to correlate the radiographic and histologic findings.
Methods: Twenty tumor endoprostheses implanted with use of the
extracortical bone-bridging technique were evaluated radiographically to
determine the extent of extracortical bone and the amount of bone ingrowth.
Five of these endoprostheses were retrieved and subjected to histologic
analysis with backscattered electron microscopy and transmitted light
microscopy to determine the extent of bone ingrowth.
Results: At a mean of twenty-eight months postoperatively, varying
amounts of extracortical bone formation were seen radiographically in all
patients. Radiographs also appeared to show bone growth into the porous-coated
segment of all implants. However, histologic analysis of the five retrieved
prostheses revealed that none of the extracortical bone had actually grown
into the porous-coated segment of the implant.
Conclusions: This study confirmed that autogenous bone-grafting of
the bone-implant junction of a tumor endoprosthesis consistently results in
the formation of extracortical bone. Although radiographs seemed to indicate
that this bone grows into the porous coating, this was not confirmed
histologically. Growth of extracortical bone into the extramedullary,
porous-coated portion of tumor endoprostheses in humans may not be attainable
with the current prosthetic design and surgical technique.
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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