| AbstractObjectives1Correlate bone mineral density (BMD)to vertebral compressive strengths.2Consummate the technique for percutaneous polymethylmethacrylate (PMMA) vertebroplasty and observe the pattern of PMMA imaging distribution.3Determine the strength and stiffness of osteoporotic with or without vertebroplasty with PMMA bone cement.4Correlation of BMD,insertion torque and pull-out strengths of pedicle screws.5Ascertain whether augmentation with PMMA bone cement can enhance pedicle screw fixation in the osteoporotic spine.6Ascertain whether augmentation pedicle screw fixation with PMMA bone cement can enhance the stability of unstable thoracolurner burst fractures of osteoporotic spine.Methods1Eighteen cadaveric lumbar were used and BMD of vertebral body was measured in a AP view using dual energy X-ray absorptiometry (DEXA). Axial compressive strength and stiffness of vertebral body was measured individually.2Fifteen fresh lumbar VBs was injected into 8m1 PMMA respectively, thickness of 1:1 (n=6), 2:3 (n6), 1:2 (n3), to observe the leakage of PMMA.3Five cadaveric thoracolumbar spines were harvested. Under CT control, percutaneous puncture of the involved vertebrae via a transpedicular approach followed by injection of PMMA. Observed the pattern of PMMA distribution.-5-4 8 fresh lumbar VBs percutaneous puncture via a transpedicularapproach followed by injection of 8ml PMMA resPectively, to measurethe temperature in the center of PMMA.5 Fresh thoracolurnbar VBs (T,,~L,) were harveSted frOm 6 old females'spines and BMD was measured uSing DEXA. All sPeciaxnens wereseparated into individual VBs and 32 VBs were divided into two groupsrandomly:l)direct vertebraplasty group (n=l6) and 2) vertebraPlasty ofpostfractured VBs group (n==l6). Each sPecimen was loaded in axialcompression until failure. The strength and stiffness were measured.6 40 VBs were harvested from different age group sPeciamens and dividedinto four groups, BMD were measured using DEXA.To measure insertiontorque and pull-out strengths.7 l6 cadaveric thoracolumbar vertebral bodies were obtained from 6 freshfrozen old females" spines(T,,-L,) at random and BMD were measuredusing DEXA. One CCD screw of 6mm diameter was imPlanted (one side).The maximum torque force was measured using torque wrench. Thescrews were pulled out from the vertebme and vertebral body wasaugmented with PMMA bone cement. TWo CCD screws were implantedbilaterally. The screws were pulkd out tWo hours later and pull-outforce were recorded.8 6 fresh frozen old females' osteoporotic spines (T,,-L,) were harvestedand Ll were defect to create an anterior and posterior column unstablemodeI. Each specimen was fixated with plate and testing were performedin flexion, extension,axial rotation,and lateral bending directions.Testing of fahgue experiments were done on MTS 858. Testing wererepeated after screws had augmented with PMMA. To observe the screwsloosening and the change of stiffness after fatigue, and to comPare thebiomechanical stability of different conditions: a)normal sPecimens,- 6 -b)defect model fixated with plate,not augmented and not fatigue, c)afterfatigue,not augmented, d)screws were augmented with PMMA,notfatigue, e)after augmented and fatigue.Results:l BMD averaged (0.9l6 i 0. l9l )g/cm' in normal contrast grouP,(0.594 f0.1l6)g/cm' in osteoporotic group and (0.402 l 0.096)g/cm' inserious osteoporotic group. The strength and stiffeess were (7 037.2ll 525.9)N, (2 16l.6l473.3)N/Inm in norma1 contrast group, (3 l58.8l749.5)N, (l 085.5 i265.2)N/mm in osteoporotic group, (l 567.0l71 l .5)N, (608.6 f 3 l5.2)N/mm in serious osteoporotic group.2 The leakage of PMMA was found in all VBs augmented withthickness of l: l,While only one was found in 2:3.3 The procedure was technically successful in all specimens, with anaverage injection axnount of 9ml PMMA per vertebral body.4 The peak temperature of vertebropl... |
