| Part one The clinical significance of anatomic characteristics of lower thoracic and lumbar pedicles[Objective]To measure and analysis the anatomic architecture and the clinical significance of lower thoracic and lumbar pedicles using spiral Computerized Tomography(CT),and to provide references for clinical surgery.[Methods]Six human adult spines(T9~L5) were gathered from preservative cadavers. Spiral CT was used to scan from T9 to L5.The measurement data included pedicle isthmus height and width,the isthmus endsteal width and height,the cortical thickness of the superior,inferior,medial and lateral walls,the proportion of pedicle trabecular core,pedicle transverse angle,pedicle sagittal angle,pedicle length and pedicle chord length.[Result]The pedicle isthmus height and width of thoracolumbar increased gradually from T9 to T12,after a slight decrease at L1 and L2,and the heightest and widthest of pedicle ithsmus were seen in L5.The height and width of cancellous bone showed similar trends. The cancellous core was more than twice as large as the cortical shell, with a range from 69.3% to 87.9% with respect to the pedicle height, and 67.9% to 79.4% with respect to the pedicle width. There was no difference between the cortical thickness of superior and that of inferior,but all were thicker than the medial and lateral wall.The medial wall was thicker than the lateral wall throughout T9~L5,these differences were highly significant(P< 0.001) .The pedicle sagittal angle was decrease gradually T9 to L5.And pedicle transverse angle was seen minimum in T12 and maximum in L5.The longest and shortest of pedicles were seen in L2 and L5 respectively,and the longest and shortest of pedicle chord length were in L2 and T11.[Conclusion]The anatomical characteristics of different segments thoracolumbar pedicles are different but with some regularity. A better understanding of the complicated structure of the pedicle isthmus guarantees safety and accuracy in transpedicular screw procedures.[Objective]To design a pedicle perforator and to evaluate the accuracy and safety of the device in comparison with techniques commonly used for pedicle cannulation in pedicle screw placement,and to measure the penetration strength of pedicle using the device.[Methods]Six human adult spines(T9~L5) were gathered from preservative cadavers,108 pedicles. For each spine specimen,the pedicles of one side(left pedicles,n=54) were cannulated with the new pedicle perforator-pedicle finder, then were placed pedicle screws. For the other side of specimen(right pedicles,n=54),the pedicles were cannulated with conventional placement technique using Kirschner wire.Once cannulated,a pedicle screw was inserted into the pilot hole.By direct observation,the misplacement of screws were recorded and the magnitude of the invasive cortical was measured with a vernier caliper. The penetration strength test of cancellous bone and medial and lateral wall of pedicle using the pedicle perforator was performed.[Result]By direct observation,17 of 108 screws(15.7%) violated the pedicle wall: seven(6.5%) medially and ten(9.3%) laterally.Of the 54 pedicle screws with pedicle perforator,4(7.4%)were classified as perforated pedicle.Of the 54 pedicle screws inserted using Kirschner wire,13(24.1%)were classified as perforated pedicle.The difference in frequency of screw misplacement between the procedure using pedicle perforator and that using Kirschner-wire was statistically significant(P<0.05). The average penetration strengths using the pedicle perforator to penetrate the medial and lateral were (165.16±21.76)N and (74.66±15.32)N respectively,and the penetration strength of cancellous bone was (14.05±2.81)N(P<0.0001).[Conclusion]In vitro study demonstrates that the new pedicle perforator can safely and effectively establish the pedicle screw channel, and also smoothly penetrate the cancellous bone and difficultly perforate the cortical bone.And it may represent an alternative to traditional pedicle cannulation techniques in the thoracolumbar. |
PDF Full Text Request