The Experimental Study Of Percutaneous Vertebroplasty

Objective To investigate the local temperature of intravertebral body, intervertebral disc and epidural space, and the influence of polymerizational thermal of polymethylmethacrylate (PMMA) on intervertebral disc, vertebral body and spinal cord in percutaneous vertebroplasty (PVP). To explore the effects of bone cement injection during the procedure of PVP on intraosseous pressure (IOP) in vertebral body. To investigate the relationship between IOP in vertebral body and pulmonary fat embolism, and the relationship between cement injection velocity and PMMA leakage into epidural space in PVP. Methods 1. PVP were done in vertebral bodies (L1, L2 and L3) of four goats. Polymethylmethacrylate was injected into each vertebral body by a transpedicular approach. Injection was stopped till PMMA reach to the posterior wall of the vertebra body or PMMA leakage into the epidural space happened. Temperature of vertebral disc, inner vertebral body and epidural space was measured respectively by electronical thermoscope during PVP. The tissue of the operated vertebral body, vertebral disc and spinal cord was sent to the histological examination with HE stains. 2. Twelve goats were randomly divided into three groups (Ⅰ,Ⅱand Ⅲ). PVP of L1 and L2 and L3 were manipulated under the guidance of C-armed fluoroscope in each group. Basical intraosseous pressure of vertebral body was measured with improved pressure-monitor system through one vertebral pedicle before PMMA was injected. The speed of cement injection in group Ⅰ,Ⅱand Ⅲ was 1ml/min, 2ml/min and 4ml/min respectively. Meanwhile, IOP of inter- vertebral body was measured.Stop injecting of PMMA until PMMA close to the posterior wall of vertebral body.Then the goats were sacrificed and the leakage of PMMA into the epidural space was examined by CT scan. The tissues of upper, medium and lower parts of both lungs were taken as the specimens to examine lipid. All the results were analyzed with SPSS(11.0) software.Results 1 38.0-38.6℃ was the normal body temperature in goats , 1.0±0.4ml(0.6-1.5ml)PMMA was injected into each vertebral body. Peak temperature in vertebral body ,intervertebral disc and epidual space was 44.3±4.7℃(38.9―58.8℃),39.4±0.9℃(38.6―41.7℃)and 38.9±0.6℃(38.2―40.5℃)respectively.The endurance time of above 45℃ in vertebral body was 0.78±0.17min. No obvious histological changes of intervertebral body and intervertebral disc and spinal cord . 2 Basical IOP of vertebral body in the goats was 3~13mmHg and there was no significant difference among three groups(p<0.05).The mean valume of PMMA injected into the vertebral body in group Ⅰ,Ⅱand Ⅲ was 1.1±0.4ml, 1.0±0.5ml and 0.8±0.4ml respectively, and there is no signiferance difference of valume among three groups. Peak IOPs of vertebral body were 13.28±3.23 mmHg in groupⅠ, 18.52±5.57 mmHg in groupⅡ and 27.25±8.72 mmHg in group Ⅲ. These peak IOPs were obvious higher than the bassical IOP. Peak IOP of vertebral body among Ⅰ,Ⅱand Ⅲ showed no obvious difference(p>0.05). The IOP of vertebral body decreased to the bassical level within 15-60s after finishing injection.The occurance of lipid in pulmonary slices is 2 /24 in group Ⅰ, 3 / 24 in groupⅡand 5 / 24 in group Ⅲ; PMMA leakage into epidural space was 2 vertebral bodies in group Ⅰ, 3 in groupⅡand 7 in group Ⅲ (p<0.05).Conclusion 1. Temperature was obvious elevated in vertebral body, mild elevated in intervertebral disc and epidural space after PMMA was injected during PVP. There was no obvious histological damage to the operated vertebral body, intervertebral disc and spinal cord when the injected cement volume was within 1.5ml duing PVP in goat. 2. IOP of vertebral body would increase with injection of PMMA . The increase of pressure was temporary and there was no positive relation between IOP increase and cement injection velocity. IOP elevation in vertebral body was one possible cause of pulmonary lipid embolism. Faster the injection speed, higher the possibility of PMM...