Anatomic Study Of The Factors About The Anterior Screw Fixation Of Upper Thoracic Spine

Objective:(1)To measure the Anterior and Posterior height of vertebral body, Upper and Lower antero- posterior diameter of vertebral body,Upper, Lower and Middle transverse diameter of vertebral body of the upper thoracic spine which from T1 to T4.Measure the Cobb's angle of the upper thoracic spine which from T1 to T4.(2)To discuss the depth of the screw of the anterior screw fixation of the upper thoracic vertebrae and the angle of the steel plate or stick before using.Method:Fifty dry specimens of upper thoracic vertebral body of native adults normal which from T1 to T4 were used to measure the relative anatomic data. Fifty center anteroposterior axial MRI photographs of upper thoracic spine of native adults normal were used to measure the Cobb's angle.Relevant measurement of lines and angles were taken with vernier caliper (0.02mm) and electronic conimeter (0.01°).Results:Measurements of Anterior and Posterior height of vertebral body, Upper and Lower antero- posterior diameter of vertebral body, Upper,Lower and The smallset transverse diameter of vertebra body of the upper thoracic vertebrae all have significant variation. All of the posterior height of the upper thoracic vertebral body(T1～T4) are higher than the anterior height of vertebral body. The antero-posterior diameter of vertebral body increases gradually which from 15.49 mm to 20.39mm.But the transverse diameter of vertebra body diminishes gradually which from 30.78 mm to 24.21mm.The Cobb's angle of the upper thoracic spine is 7.20±2.04°.Conclusion:1. All of the posterior height of the upper thoracic vertebral body(T1～T4) are higher than the anterior height of vertebral body.This is to maintain the physiological concave bending of the upper thoracic spine.2. The antero-posterior diameter of vertebral body increases gradually.The smallest one is 15.49 mm,the biggest one is 20.39mm.Because of the inclination,the depth of the screw should bigger than the antero-posterior diameter of the vertebral body.3. The transverse diameter of vertebra body diminishes gradually. The biggest one is 30.78 mm,the smallest one is 24.21mm.So we can select the suitable screw and depth in latero-anterior screw fixation of the upper thoracic spine.4. The Cobb's angle of the center anteroposterior axial MRI photographs of upper thoracic spine of native adults normal is 7.20±2.04°.So we should bend the steel plate or stick to a suitable concave angle(7.20±2.04°)before the fixation in the surgery.If we want to develop the internal fixation device of the anterior and latero-anterior of upper thoracic vertevrae,we should design the bent angle(7.20±2.04°)which suitable to the physiological concave bending of the upper thoracic spine and make sure it has a satisfactory biomechanics effcet.