Biomechanical comparison of kyphoplasty with different bone cements.
METHODS
Ex vivo biomechanical study.


OBJECTIVE
To compare the biomechanical properties of isolated, fractured, osteoporotic vertebral bodies after treatment by kyphoplasty with one of two cements: alpha-tri-calcium phosphate cement (Biopex-R; Mitsubishi Materials Corp., Tokyo, Japan) or polymethylmethacrylate (Simplex P; Stryker-Howmedica-Osteonics, Mahwah, NJ).


BACKGROUND
Kyphoplasty and vertebroplasty typically use polymethylmethacrylate cements for the treatment of osteoporotic compression fractures. Scant information exists regarding the use of alternative cements in kyphoplasty.


METHODS
Simulated compression fractures were created in 24 vertebral bodies (T6-T9, L2-L5) harvested from three female cadavers. Vertebral bodies were assigned to one of two groups: kyphoplasty with Biopex-R or kyphoplasty with Simplex P. The kyphoplasty treatment consisted of inserting bone tamps bipedicularly into each vertebral body, inflating the tamp, and filling the created void with Biopex-R or Simplex P. Pretreatment and post-treatment heights were measured, and the repaired vertebral bodies were recompressed to determine posttreatment strength and stiffness values. Differences were checked for significance (P < 0.05) using a repeated-measures analysis of variance followed by Tukey's test.


RESULTS
Kyphoplasty with Biopex-R restored strength in the lumbar and thoracic vertebral bodies. Kyphoplasty with Simplex P displayed significantly greater posttreatment strength than initial strength in the thoracic region. Vertebral bodies augmented with either cement were significantly less stiff than their initial conditions, except for the thoracic vertebrae treated with Simplex P, in which stiffness was restored. There was no significant difference in percentage of height restored between the cement treatments.


CONCLUSIONS
Kyphoplasty with either cement restored initial strength. In general, stiffness was not restored.
Tomita
Seiji
S
Orthopaedic Instrumentation Laboratory, Department of Orthopaedic Surgery, Johns Hopkins University/Johns Hopkins Bay-view Medical Center, Baltimore, MD 21224-2780, USA.
Molloy
Sean
S
Jasper
Louis E
LE
Abe
Muneaki
M
Belkoff
Stephen M
SM
D000368:Aged; D001696:Biomechanical Phenomena; D001843:Bone Cements; D002130:Calcium Phosphates; D005260:Female; D006801:Humans; D020366:Methylmethacrylate; D010024:Osteoporosis / Q000150:complications; D011859:Radiography; D016103:Spinal Fractures / Q000209:etiology / Q000503:physiopathology / Q000628:therapy*; D013131:Spine / Q000000981:diagnostic imaging / Q000503:physiopathology
D001843:Bone Cements; D002130:Calcium Phosphates; C485828:alpha-tricalcium phosphate; D020366:Methylmethacrylate