Accuracy Of X-ray Assessment Of The Position Of Subaxial Cervical Pedicle Screw Implanted In Abumi’s Method

Objective:To evaluate the accuracy and feasibility of assessment of subaxial cervical pedicle screw implanted in Abumi’s method with anteroposterior and oblique X-ray films using specific standard through retrospective analysis.Method:Ten patients,who were diagnosed with subaxial diseases,underwent subaxial internal fixation and possessed imaging data of X-ray and CT scan with relative reconstruction,were chosen. The ten patients included five cases of degenerative diseases,three cases of trauma,two cases of neoplastic diseases. All these cases included44subaxial cervical pedicle screws,which were divided into3groups(Group A:C3-5,Group B:C6,Group C:C7),according to the anatomical and imaging parameters of different segments of subaxial cervical pedicles.There were22screws in Group A,12screws in Group B,10screws in Group C.After operation, all the patients underwent X-Ray and CT examination to get the anteroposterior and oblique X-ray films and CT films of the axial,the sagittal and the coronary sections. As to the X-ray assessment,the relationship between screws and superior and inferior walls of pedicles was assessed by the oblique films,which rely on the relatively long radial line on the oblique films;The relationship between screws and medial and lateral walls of pedicles was assessed by the anteroposterior films,with the head of the screw which was located between the medial and lateral margin of uncovertebral joint as the standard.As to the CT assessment,the relationship between screws and superior and inferior walls of pedicles was assessed by the CT films of the consecutive sagittal reconstruction;The relationship between screws and medial and lateral walls of pedicles was assessed by the CT films of consecutive axial section.Then,with the outcome of the CT assessment as the standard,the relative sensitivity,specificity and accuracy of the X-ray assessment were calculated.Meanwhile,the accuracy of the three groups about the relationship between screws and every wall of pedicle was compared.Result:The relative sensitivity and specificity of the assessment were high(sensitivity about medial wall:Group A100%, Group B100%,Group C lack of positive data;specificity about medial wall:Group A95.5%, Group B100%,Group C100%;sensitivity about lateral wall:Group A100%, Group B88.9%,Group C100%;specificity about lateral wall:Group A100%, Group B100%,Group C75.0%;sensitivity about superior wall:Group A100%, Group B100%,Group C lack of positive data;specificity about superior wall:Group A90.9%, Group B100%,Group C100%;sensitivity about inferior wall:Group A lack of positive data, Group B lack of positive data,Group C100%;specificity about inferior wall:Group A100%, Group B100%,Group C66.7%).The relative accuracy about medial wall was95.5%in Group A,100%in Group B,100%in Group C;The relative accuracy about lateral wall was100%in Group A,91.7%in Group B,90.0%in Group C;The relative accuracy about superior wall was95.5%in Group A.100%in Group B,100%in Group C;The relative accuracy about inferior wall was100%in Group A,100%in Group B,80.0%in Group C.There were no statistically significant differences in accuracy among the3groups,except for the accuracy about inferior wall of Group A and CConclusion:This way relying on anteroposterior and oblique X-ray films to assess the accuracy of subaxial cervical pedicle screws,with the CT assessment as the standard,has high relative sensitivity,specificity and accuracy.lt can basically satisfy the clinical need with advantages including low radiation exposure,saving time and money.