Biomechanical evaluation of kyphoplasty with calcium sulfate cement in a cadaveric osteoporotic vertebral compression fracture model.
BACKGROUND
Vertebral compression fractures can cause deformity, pain, and disability. Kyphoplasty involves percutaneous insertion of an inflatable balloon tamp into a fractured vertebra followed by injection of polymethylmethacrylate (PMMA) bone cement. PMMA has several disadvantages such as potential thermal necrosis and monomer toxicity. Calcium sulfate cement (CSC) is nontoxic, osteoconductive, and bioabsorbable.


OBJECTIVE
To evaluate the biomechanical performance of CSC for kyphoplasty in cadaveric osteoporotic vertebral bodies.


METHODS
Destructive biomechanical tests using fresh cadaveric thoracolumbar vertebral bodies.


METHODS
Thirty-three vertebral bodies (T9 to L4) from osteoporotic cadaveric spines were disarticulated, stripped of soft tissue, and measured for height and volume. Each vertebral body was compressed at 0.5 mm/s using a hinged plating system on a materials testing machine to create an anterior wedge fracture and reduce the anterior height by 25%. Pretreatment strength and stiffness were measured. Two KyphX inflatable balloon tamps were used to reexpand each vertebral body. After randomization, three groups were created: Group A-no cement; Group B-PMMA; Group C-calcium sulfate cement. Groups B and C were filled with the corresponding cement to 25% of the vertebral body volume. All vertebral bodies were then recompressed by 25% of the post-kyphoplasty anterior height to obtain posttreatment strength and stiffness.


RESULTS
Treatment with PMMA restored vertebral strength to 127% of the intact level (4168.2 N+/-2288.7) and stiffness to 70% of the intact level (810.0 N/mm+/-380.6). Treatment with CSC restored strength to 108% of the intact level (3429.6 N+/-2440.7) and stiffness to 46% of the intact level (597.7 N/mm+/-317.5). CSC and PMMA were not significantly different for strength restoration (p=.4). Significantly greater strength restoration was obtained with either PMMA or CSC, compared with the control group (p=.003 and .03, respectively). Stiffness restoration tended to be greater with PMMA than for CSC, but this difference was not statistically significant (p=.1). Both cements had significantly greater stiffness when compared with the control group (p=.001 and p=.04, respectively).


CONCLUSIONS
Use of CSC for kyphoplasty yields similar vertebral body strength and stiffness as compared with PMMA. It may be a useful alternative bone cement for kyphoplasty. Further studies are required to assess the bioabsorption of CSCs after kyphoplasty in vivo.
Perry
Andrew
A
Veterans Administration and University of California, San Diego, 3350 La Jolla Village Drive, San Diego, CA 92161, USA.
Mahar
Andrew
A
Massie
Jennifer
J
Arrieta
Noemi
N
Garfin
Steven
S
Kim
Choll
C
D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D001843:Bone Cements; D002102:Cadaver; D002133:Calcium Sulfate / Q000008:administration & dosage*; D005260:Female; D050815:Fractures, Compression / Q000209:etiology / Q000503:physiopathology / Q000628:therapy*; D006801:Humans; D066298:In Vitro Techniques; D008159:Lumbar Vertebrae / Q000293:injuries* / Q000503:physiopathology; D008297:Male; D010024:Osteoporosis / Q000150:complications*; D019904:Polymethyl Methacrylate; D016103:Spinal Fractures / Q000503:physiopathology / Q000628:therapy*; D013904:Thoracic Vertebrae / Q000293:injuries* / Q000503:physiopathology
D001843:Bone Cements; D019904:Polymethyl Methacrylate; D002133:Calcium Sulfate