The Journal of Bone and Joint Surgery (American). 2006;88:171-178.
doi:10.2106/JBJS.D.02313
© 2006 The Journal of Bone and Joint Surgery, Inc.
Reconstruction of Noncontained Distal Femoral Defects with Polymethylmethacrylate and Crossed-Screw Augmentation: A Biomechanical Study
Patrick C. Toy, MD1,
Jeff France, MD2,
R. Lor Randall, MD3,
Michael D. Neel, MD4,
Ronald I. Shorr, MD, MS5 and
Robert K. Heck, MD1
1 Department of Orthopaedic Surgery, University of Tennessee-Campbell Clinic,
1211 Union Avenue, Suite 510, Memphis, TN 38104. E-mail address for P.C. Toy:
ptoy{at}utmem.edu
2 Appalachian Orthopaedic Association, 120 West Ravine Road, Kingsport, TN
37660
3 Huntsman Cancer Institute and Primary Children's Medical Center, University of
Utah, 30N 1900E Room 3B165, Salt Lake City, UT 84132
4 Division of Orthopaedic Oncology, St. Jude Children's Research Hospital, 332
North Lauderdale Street, Memphis, TN 38105
5 Department of Preventive Medicine, University of Tennessee, Memphis, 66 North
Pauline, Suite 633, Memphis, TN 38163
Investigation performed at the University of Tennessee-Campbell Clinic
Department of Orthopaedic Surgery, Memphis, Tennessee
The authors did not receive grants or outside funding in support of their
research for 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: Curettage and cementation with polymethylmethacrylate
are frequently used in the treatment of aggressive benign bone lesions such as
giant-cell tumors, but strength and stiffness of the reconstructed bone have
been concerns. This biomechanical study was undertaken to determine whether
augmenting the cement with crossed screws would result in a stronger
reconstruction.
Methods: Large noncontained defects were created in the medial
femoral condyles of twenty matched pairs of human cadavera. Four groups were
organized to compare three types of reconstruction: (1) polymethylmethacrylate
alone, (2) polymethylmethacrylate and intramedullary Steinmann pins, and (3)
polymethylmethacrylate with crossed screws engaging the opposite cortex. The
specimens were subjected to 2000 compressive cycles and were subsequently
monotonically loaded to failure under a controlled displacement rate. Failure
load and stiffness were determined for each femur that survived the cycling
process.
Results: Femora reconstructed with crossed screws and cement failed
at higher loads and had greater stiffness than those reconstructed with cement
alone (p = 0.025 and p = 0.0007) or cement augmented with intramedullary
Steinmann pins (p = 0.019). Failure of femora reconstructed with cement and
crossed screws occurred through an extra-articular transverse fracture, while
failure in those with cement alone and cement with Steinmann pins occurred
through an intra-articular (intercondylar) fracture.
Conclusions: In this in vitro cadaver study, augmentation of
polymethylmethacrylate cement with crossed screws resulted in a stronger
reconstruction of distal femoral tumor defects than that obtained with cement
alone or with cement and intramedullary Steinmann pins.
Clinical Relevance: The stronger and stiffer construct of cement
augmented with crossed screws might allow earlier walking and rehabilitation
after tumor resection, with a decreased risk of fracture after reconstruction.
Should a fracture occur after reconstruction with polymethylmethacrylate and
crossed screws, the results of this study suggest that the fracture is likely
to be extra-articular, which can be treated with standard fracture-fixation
methods.

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