Biomechanical behavior of MRI-signal-inducing bone cements after vertebroplasty in osteoporotic vertebral bodies: An experimental cadaver study.
BACKGROUND
Conventional water-free polymethylmethacrylate cements are not MRI visible due to the lack of free protons. A new MRI-visible bone cement was developed through the addition of a contrast agent and either a saline solution or a hydroxyapatite (Wichlas et al., 2010). The purposes of the study were to examine the influence of the two MRI-signal-inducing cements on the biomechanical behavior of cadaveric osteoporotic vertebral bodies after vertebroplasty and to compare the performance of the cements with conventional polymethylmethacrylate cement.


METHODS
Three different cements were used: standard polymethylmethacrylate cement and two modified MRI-signal-inducing cements that were mixed with either a 0.9% saline solution or a hydroxyapatite. The modulus of elasticity for the standard polymethylmethacrylate cement was 2040MPa, and the moduli for the MRI-signal-inducing cements that were mixed with a 0.9% saline solution and a hydroxyapatite were 1477 and 1225MPa, respectively. The lumbar vertebral bodies from nine osteoporotic spines (mean age=87 years, range=78-99 years) of female cadavers were examined. Three groups were formed: polymethylmethacrylate cement with saline solution (n=14), polymethylmethacrylate cement with hydroxyapatite (n=12) and polymethylmethacrylate cement (n=13). The vertebral bodies were biomechanically tested before and after vertebroplasty. Stiffness was chosen as the primary biomechanical parameter.


RESULTS
The vertebral body stiffness was nearly two-fold greater after vertebroplasty, and this increase was statistically significant for every group. All the groups had similar vertebral body stiffness value before and after the vertebroplasty. The UNIANOVA test for multivariate analysis of variance showed no influence of lumbar level, injected cement volume and initial vertebral body stiffness.


CONCLUSIONS
The elastic moduli of the cements appear to exert little influence on the biomechanical values when the cement is in the vertebral body. Based on the direct comparison with the classic polymethylmethacrylate cement, we believe that the implementation of such cements for MRI-guided vertebroplasties is feasible.
Center for Musculoskeletal Surgery, Charité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353, Berlin, Germany.
Florian
F
Wichlas
Center for Musculoskeletal Surgery, Charité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353, Berlin, Germany.
Heidi
H
Trzenschik
Center for Musculoskeletal Surgery, Charité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353, Berlin, Germany; Berlin-Brandenburg Center for Regenerative Therapies/BSRT, Charité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353, Berlin, Germany. Electronic address: serafeim.tsitsilonis@charite.de.
Serafim
S
Tsitsilonis
Julius Wolff Institut, Charité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353, Berlin, Germany.
Antonius
A
Rohlmann
Clinic for Traumatology and Orthopedics, Nuremberg Hospital South, Breslauer Str. 201, 90471, Nuremberg, Germany.
Hermann-Josef
HJ
Bail
D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena / Q000502:physiology; D001843:Bone Cements / Q000737:chemistry / Q000627:therapeutic use*; D002102:Cadaver; D003287:Contrast Media; D004548:Elasticity; D005260:Female; D006801:Humans; D006882:Hydroxyapatites / Q000737:chemistry / Q000627:therapeutic use; D008159:Lumbar Vertebrae; D008161:Lumbosacral Region; D008279:Magnetic Resonance Imaging; D010024:Osteoporosis / Q000628:therapy*; D019904:Polymethyl Methacrylate / Q000737:chemistry / Q000627:therapeutic use; D016103:Spinal Fractures / Q000628:therapy; D054854:Vertebroplasty / Q000379:methods*
D001843:Bone Cements; D003287:Contrast Media; D006882:Hydroxyapatites; C475044:hydroxyapatite cement; D019904:Polymethyl Methacrylate
Cementoplasty; MRI-guided surgery; Pathologic spinal fractures; Polymethylmethacrylate cement; Stiffness; Vertebroplasty