The Experimental Study Of Restoration Of Bone Fragments With The Intraoperative CT Assistance In The Thoracolumbar Burst Fractures

BackgroundThoracic and lumbar burst fractures are a severe spinal trauma. There are13.3-45.9persons with spinal trauma in every1000000persons every year in thedeveloped countries. In China the morbidity of spinal trauma is4.8-6.63%in the allfractures, while in the war or earthquake, it is10.2-14.8%. Ninety percent of all spinalfractures occur in the thoracolumbar region, and burst fractures contribute toapproximately10–20%of such injuries. It is one of the most common causes forspinal cord injury, and the frequency of neurological deficits in all thoracolumbarburst fractures (TLBF) can reach up to50–60%. Car accidents accounted for43%ofthe fractures, followed by falls in25%and incident of violence in16.5%in thedeveloped countries. In China falls accounted for38.8%of the fractures, followed bycar accidents in30.1%and minor trauma in11%. Hospital charges amounted to anaverage of$46,3006±31,400per patient with uncompleted neurological deficits, thehighest cost is$62900±38900. While the charges amounted to an average of$67400±31500per patient with completed neurological deficits.In1979Vidal reported that ligamentotaxis is a method of indirect reduction offracture by the application of a strong distraction force which is transmitted throughintact ligaments and capsules and helps to restore skeletal anatomy. But Muellerfound that trapezoid-shaped fragments resisted reduction by ligamentotaxis. Gertzbeinfound these indirect reduction techniques are not as effective in the patient withthoracolumbar fracture resulting in>67%compromise of the spinal canal because theannular ligament attachments to the extruded fragments are less likely to be intact.Although many researchers acquired different results, they do not descripe the detailsof fragments and reasons of affecting the reposition of bone fragments.ObjectiveTo determine the reasons of affecting reposition of bone fragments in theposterior surgical process of thoracolumbar burst fractures with ligamentotaxis of posterior longitudinal ligament(PLL) with intraoperative CT assistance.Methods and Material1. Retrospectively analyze the patients with thoracolumbar burst fractures treated inour hospital from2009to2011.2. Exclusion criteria: patients with multiple spinal vertebrae fractures, orosteoporosis, or tumor metastasis, or spondylolisthesis, or spinal dislocation.Inclusion criteria: single thoracolumbar burst fractures caused by trauma andintake PLL.3. Assess the position of bone fragments according to the image of CT scan.4. Measured parameters: mid-sagittal canal diameter (MSD), transverse canaldiameter (TCD), anterior vertebral body compression ratio (AVBCR), middlevertebral body compression ratio (MVBCR), posterior vertebral bodycompression ratio (PVBCR), posterior distance between injury and abovevertebras (DIA), posterior distance between injury and below vertebras (DIB),local kyphosis (LK), rotational angle of bone fragments in the sagittal-plane(SRA), rotation angle of bone fragments in the axial-plane (ARA), mid-sagittalcanal diameter compression ratio (MSDCR), cross-sectional area compressionratio (CSACR), height of bone fragments(HOBF), width of bonefragments(WOBH).5. Instrument: Siemens Sensation Open40double slide rail intraoperative CT.Scanning voltage:120kv, electricity:180-230mAs, pitch:0.9, thickness:10mm,reconstruction thickness:1.5mm.Result1. Bone fragments uncovered by PLL can not be repositioned by the ligamentotaxis.2. There were not significant difference on SRA(t=1.154，P=0.254>0.05) andARA(t=0.845， P=0.402>0.05) between repositional and non-repositionalfragments, but were significant difference on LOBF(t=2.341,P=0.023<0.05),WOBF(t=3.38,P=0.001<0.05), RLBVPW(u=2.668,P=0.008<0.05), andRWBTCD(t=4.38,P=0.0001<0.05) between repositional and non-repositionalfragments. When RLBVPW>47%and RWBTCD>75%, bone of fragments were difficulty to be repositioned by ligamentotaxis of PLL.3. MSD, MSDCR, TCD, CSACR and PVBCR were correlation to reposition ofbone fragments.4. There were not significant difference on DIA(t=1.192,P=0.238>0.05), DIB(t=-1.218,P=0.228>0.05), AVBC(t=-1.126,P=0.260>0.05),MVBCR(t=-1.309,P=0.195>0.05) and LK(t=-0.706, P=0.483>0.05) betweenrepositional and non-repositional fragments, but were significant difference onMSD(t=2.952,P=0.004<0.05), TCD(t=-2.353,P=0.022<0.05),MSDCR(t=-4.375,P=0.000<0.05), CSACR(t=-2.673,P=0.010<0.05) and PVBCR(t=-2.306,P=0.025<0.05) between repositional and non-repositional fragments.When MSD<7.7mm, TCD<20mm, MSDCR>60%, CSACR>44%andPVBCR>18%, bone of fragments were difficulty to be repositioned byligamentotaxis of PLL.Conclusion1. When bone fragments were not covered by PLL, they can not be repositioned bythe ligamentotaxis.2. When bone fragments were covered by PLL, RLBVPW>47%andRWBTCD>75%, bone of fragments were difficulty to be repositioned byligamentotaxis of PLL.3. AO classification was correlation to reposition of bone fragments in thethoracolumbar burst fractures.4. When MSD<7.7mm, TCD<20mm, MSDCR>60%, CSACR>44%andPVBCR>18%, bone of fragments were difficulty to be repositioned byligamentotaxis of PLL.