| Objective:To explore and determine the correlation between CT values of thoracolumbar vertebral segments and bone mineral density(BMD)of the corresponding vertebral segments in young adults so as to indirectly evaluate BMD of the vertebral body through CT values of their corresponding thoracolumbar vertebral segments;To measure the difference of regional CT values in the vertebral body,apply it in clinical treatment of thoracolumbar vertebral fractures and improvement of bone graft fusion range,and explore their clinical significance.Methods:The study contains three sub-studies to explore the correlation between the internal CT values of the thoracolumbar vertebral segments and their corresponding vertebral BMD,identify the differences in regional CT values of the thoracolumbar vertebral body and evaluate their guiding significance in clinical treatment of thoracolumbar vertebral fractures and improvement in bone graft fusion range.In the first,a total of 60 young adults who underwent both thoracolumbar CT and bone mineral density(BMD)examinations within 3 months were enrolled to study the correlation between CT values of thoracolumbar CT examination and BMD.These adults were excluded if they had spinal inflammation,trauma,tumors,tuberculosis,or other underlying diseases including immune diseases,diabetes,hyperthyroidism,and hypothyroidism,and took hormones for a long time.The thoracolumbar segments,which could be effectively measured for CT values and BMD after excluding relevant influencing factors,were selected as the study objects.The obtained BMD and CT values of the corresponding vertebral segments were statistically analyzed to determine the correlation between CT values and BMD of the corresponding vertebral segmentsin the thoracolumbar region.Secondly,60 healthy young adults who had thoracolumbar CT performed from December 2015 to October 2017 and did not have spinal fractures,tumors,inflammation,tuberculosis,severe diabetes,hyperthyroidism,hypothyroidism,osteoporosis and systemic immune diseases and take long-term hormone therapeutics were enrolled.These subjects were at age of 22–59 with an average of 46.3 years old.Among them,37 were males and 23 were females.The T11-L2 thoracolumbar body was subjected to3-dimensional CT and classified into upper,middle and lower regions using a three-dimensional imaging system.In order to reduce human errors,each region was roughly divided into four quadrants at each level to avoid the influences of cortical bone,hyperosteogenetic zone and vertebral venous sinus.A total of four regions,one in each quadrant,were taken as the regions of interest to measure their CT values.Each image was measured by radiologists and clinicians with more than 10 years of clinical experiences in a double-blind manner to avoid the influence of subjective factors on the measurement results.Because three-dimensional reconstruction of lumbar vertebrae was the major reconstruction,most images were taken up to T12 with a few to T11.Among the 60 subjects,8 had images up to T11,28 up to T12,58 down to L1,and 52 down to L2.The differences in CT values among the upper,middle and lower regions of the thoracolumbar body and between the anterior and posterior thoracolumbar vertebral bodies were statistically analyzed.In the last,a total 178 young adult patients with thoracolumbar fractures who admitted to the Department of Orthopedics of our hospital from December 2016 to January 2018 were enrolled.Their information and clinical treatment results were summarized and analyzed.Among them,a total of 97 patients with simple burst fractures and simple compression fractures were subjected to image analysis.The results showed that all fractures were located in the upper anterior thoracolumbar body.In addition,127patients with vertebral compression fractures and burst fractures who underwent operation were also analyzed.The results showed they belonged to A1.1,A1.2.1,A1.2.2,A1.3,A2,A3.1.1,A3.2.1,B1.1,B1.2 and B1.3 in AO classification.Among the 127patients,31 had simple compression fractures and underwent operation via transdermal or multi-fissure intermuscular approach,simple fracture reduction,and USS internal fixation,but not spinal canal decompression and bone graft fusion;50 patients with severe upper and lower vertebral fractures who enrolled earlier underwent surgeries for fracture reduction and USS internal fixation as well as non-traditional range posterior lateral bone graft fusion,i.e.,fusion of the diseased vertebrae with upper and lower vertebral body;and 46 patients with thoracolumbar fractures with heavier compression,burst fracture or nerve injury who enrolled later in the study were treated using modified bone graft fusion range approach.They were at age of 19–61 with an average of 46.5 years old and included 33 males and 13 females.Among the 46 patients,18 were injured in car accidents,21 were injured by fall from height and 7 were injured due to bury,5 had T11fracture,14 had T12 fracture,17 L1 fracture and 10 had L2 fracture.Most of the thoracolumbar fractures were burst fractures with manifestations of upper anterior burst,commutation and posterior superior edge protruding into the spinal canal,in combination of spinal canal stenosis and partial spinal cord injury.Moreover,According to Frankel classification,5 patients were classified as grade A before operation,10 as grade B,8 as grade C,16 as grade D,and 7 as grade E.According to TLICS scoring system,4 patients had score 4,7 had score 5,9 had score 6,16 had score 7,7 had score 8and 3 had score 9.Nine patients were treated with emergency surgery and the remaining37 patients were subjected to operation within 7 days after the injury.The postoperative outcomes were observed in follow-up,including short-term and long-term fixation effects,long-term fracture healing,bone graft fusion effects,and spinal function recovery.ResultsThe results of the first part of the study showed that 128 effective thoracolumbar images were obtained in 60 subjects,including 58 L2 vertebral images,52 L1 vertebral images,and 18 T12 vertebral images.Their CT values and BMD were measured and expressed as mean plus standard deviation(x±s).The CT values(Hu)were 213.7±45.1for T12 images,226.4±53.2 for L1,247.3±57.7 for L2 and 234.3±65.2 for overall images.The BMD was 664.4±80.1 mg/cm~3 for T12,722.7±76.6 mg/cm~3 for L1,832.3±90.5 mg/cm~3 for L2,and 774.3±98.7 mg/cm~3in average.The linear regression analysis of correlation between BMD of the three segments of vertebral body and their corresponding CT values showed that there were positive linear correlations between BMD and cancellous bone CT values of T12,L1 and L2 vertebral bodies,r=0.942,0.936and 0.909,respectively,p=0.019.In general,the cancellous bone CT values of thoracolumbar body were positively correlated with BMD of thethoracolumbar body,r=0.834,p=0.023.The higher the BMD was,the higher the CT value,indicating a significant positive correlation between the two.The results of the second part of the study showed that in a single vertebral body of the thoracolumbar region,the CT values of the vertebral body gradually increased from top segment to bottom segment;the CT value of the upper one third of the vertebral body was the highest,followed by that of the middle one third,and the CT value of the lower one third of the vertebral body was the lowest,showing significant differences among the three(P<0.01);the CT value of the anterior segment was significantly lower than that of the posteriorsegment(P<0.01).Measurement of BMD using each intervertebral disc and one third of its adjacent two vertebrae as a motor unit showed that BMD of the upper unit was higher than that of the lower unit,but the difference was not statistically significant(P>0.05).The results of the third part of the study showed that all the 46 patients who were subjected to operation via improved bone graft fusion range approach were followed up for 6–34 months,with an average of 18 months.All of them obtained complete bone healing within 4–8 months,with an average of 6 months.Auxiliary examinations of posterolateral bone graft fusion and second surgery confirmed that most of the bone grafts achieved good fusion.After operation,one patient had a pedicle screw fracture on the side of the lower vertebra.All other patients had no obvious loosening of the fixers.By contrary,loosening of the internal fixers occurred in 5 patients who were not subject to bone graft fusion.Among these 5 patients,three had broken nails occurred above the fractured vertebra.After the second operationin follow-up to remove the internal fixers,motor function of the lumbar vertebrae was preserved and well recovered without losing the anterior height of the injured vertebral body.The height of the anterior border of the fractured vertebral body was measured before the pedicle screw was installed and after the pedicle screw was taken out.Analysis performed by SPSS13.0 statistical analysis software showed no significant difference in the heights of the anterior border of the fractured vertebral body before installing the pedicle screws and after removal of the pedicle screws(P>0.05).Conclusions1.The study showed that there was a significant positive correlation between cancellous bone CT values of the thoracolumbar body and BMD of the corresponding vertebral body,and CT values can be used to indirectly reflect the vertebral BMD.2.The high volume CT value of the thoracolumbar body can replace BMD measurement to more accurately evaluate the vertebral BMD,to determine the degree of rarefaction of bone,and to diagnose osteoporosis.3.This study measured the regional CT value of the vertebral body and found there were regional differences in CT values of the vertebral body.The results clearly showed that the CT value of the upper vertebral body was lower than that of the lower vertebral body,and the CT value of the anterior vertebral body was lower than that of the posterior vertebral body.These findings could be used to explain why in clinics,the vertebral compression fractures often occurs in the anterior vertebral body rather than the posterior vertebral body.4.The findings that there are regional differences in the CT values of the vertebral body,the CT value of the upper vertebral body was lower than that of the lower vertebral body,and the CT value of the anterior vertebral body was lower than that of the posterior vertebral body were used to guide the treatment of thoracolumbar vertebral fractures and improve the posterolateral bone graft fusion range of thoracolumbar vertebral fractures so as to obtain better bone graft fusion rate,retain the spinal motor function to the greatest extent and reduce the degeneration of adjacent segments. |
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