[An in vitro biomechanical evaluation of effect of augmentation pedicle screw fixation with polymethylmethacrylate on osteoporotic spine stability].
OBJECTIVE
To ascertain whether augmentation pedicle screw fixation with polymethylmethacrylate (PMMA) can enhance the stability of unstable thoracolumbar burst fractures of osteoporotic spine.


METHODS
Six fresh frozen female osteoporotic spines (T10-L5) were harvested and an anterior and posterior column unstable model of L1 was made. Each specimen was fixated with plate and the stability test were performed by flexion, extension, axial rotation and lateral bending. The test of fatigue was done with MTS 858. The tests were repeated after screws were augmented with PMMA. To compare the biomechanical stability of 6 different conditions: a. normal specimens (control), b. defect model fixed with plate, not augmented and not fatigued, c. after fatigued, not augmented, d. screws augmented with PMMA, not fatigued, e. after augmented and fatigued.


RESULTS
In b., d. and e. conditions, the ranges of motion (ROM) were 6.23 +/- 1.56, 4.49 +/- 1.00, 4.46 +/- 1.83 in flexion and 6.60 +/- 1.80, 4.41 +/- 0.82, 4.46 +/- 1.83 in extension. There was no significant difference (P > 0.05), they were significantly smaller than those in a. and c. conditions (8.75 +/- 1.88, 1.47 +/- 2.25 and 8.92 +/- 2.97, 12.24 +/- 3.08) (P < 0.01).


CONCLUSIONS
The results demonstrated that augmentation pedicle screws fixation with PMMA can increase the stability of osteoporotic spine.
Fan
Shicai
S
Department of Orthopaedic Surgery, Shajing People's Hospital, Shenzhen, Guangdong, 518104, P. R. China.
Liu
Shixue
S
Deng
Yuexing
Y
D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D001843:Bone Cements; D015519:Bone Density; D001863:Bone Screws; D002102:Cadaver; D005260:Female; D006801:Humans; D016268:Internal Fixators; D008159:Lumbar Vertebrae / Q000502:physiology / Q000601:surgery*; D008875:Middle Aged; D009038:Motion; D010024:Osteoporosis / Q000503:physiopathology / Q000601:surgery*; D019904:Polymethyl Methacrylate; D011859:Radiography; D013123:Spinal Fusion / Q000295:instrumentation* / Q000379:methods; D013131:Spine / Q000000981:diagnostic imaging / Q000601:surgery; D016896:Treatment Outcome
D001843:Bone Cements; D019904:Polymethyl Methacrylate