Reconstruction of noncontained distal femoral defects with polymethylmethacrylate and crossed-screw augmentation: a biomechanical study.
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.
Toy
Patrick C
PC
Department of Orthopaedic Surgery, University of Tennessee-Campbell Clinic, 1211 Union Avenue, Suite 510, Memphis, TN 38104, USA. ptoy@utmem.edu
France
Jeff
J
Randall
R Lor
RL
Neel
Michael D
MD
Shorr
Ronald I
RI
Heck
Robert K
RK
D000368:Aged; D001696:Biomechanical Phenomena; D001843:Bone Cements / Q000627:therapeutic use*; D001858:Bone Nails; D001859:Bone Neoplasms / Q000503:physiopathology / Q000601:surgery*; D001863:Bone Screws; D002102:Cadaver; D016022:Case-Control Studies; D003475:Curettage; D004548:Elasticity; D005264:Femoral Fractures / Q000145:classification / Q000503:physiopathology; D005269:Femur / Q000503:physiopathology / Q000601:surgery*; D006801:Humans; D019904:Polymethyl Methacrylate / Q000627:therapeutic use*; D019651:Plastic Surgery Procedures; D016474:Weight-Bearing / Q000502:physiology
D001843:Bone Cements; D019904:Polymethyl Methacrylate