Objective: To explore the relationship between the compression depth and compressive stress of the anterior and posterior cervical spinal cord in different sports positions. Methods: Specimens of ten intact fresh cervical spine (C₁-T₁) from adult cadaver were collected. In order to simulate cervical disc degeneration and abnormal ligamentum flavum, we placed two hemispherical steel balls into the anterior and posterior side of the cervical spinal cord through the bone window of the C_{4, 5}. The measurement was conducted in 10%, 20%, 30%, 40%, 50%, and 60% of the sagittal diameter for the compressive stress of the anterior and posterior cervical spinal cord under different compression depths of flexion, neutral, and posterior extension. Results: The anterior depth of a certain pressure with the posterior pressure depth was increasing in neutral position, the stress on the anterior of the cervical cord-meningeal complex (CCMC) had no significant change, while the stress on the posterior of the CCMC increased greatly with the increasing of the degree of canal occlusion. The stress on the posterior of the CCMC varied insignificantly between 10% and 20% depth of canal occlusion (P>0.05). However, there was remarkable significance among 30% and 60% (P<0.05). In extension or flexion position, the stress on the anterior of the CCMC had no significant change, while the stress on the posterior of the CCMC increased greatly with the increasing of the degree of canal occlusion. The stress on the posterior of the CCMC varied insignificantly between neighboring depths of canal occlusion from 10% (P>0.05). However, there was remarkable significance among 20% and 60% (P<0.05). The posterior depth of a certain pressure with the anterior pressure depth was increasing in neutral position. The stress on the anterior of the CCMC increased greatly with the increasing of the degree of canal occlusion. The stress on the anterior of the CCMC varied insignificantly between 10% and 20% depth of canal occlusion(P>0.05). However, there was remarkable significance among 30% and 60% (P<0.05). The stress on the posterior of the CCMC had no significant change. In extension or flexion position, the stress on the anterior of the CCMC increased greatly with the increasing of the degree of canal occlusion. The stress on the anterior of the CCMC varied insignificantly between neighboring depths of canal occlusion from 10% (P>0.05). However, there was remarkable significance among 20% and 60% (P<0.05). The stress on the posterior of the CCMC had no significant change. Compared with the neutral position, the anterior flexion position and the posterior extension position had different trends in the compressive stress in the anterior and posterior aspect of the cervical spinal cord. Conclusion The stress on the anterior and the posterior of the CCMC has a closely nonlinear relationship with the depth of canal occlusion. With the increase of the depth of canal occlusion, the stress is increasing, especially running over the 30% depress of canal occlusion under neutral position. However, the stress is increased, especially running over the 20% depress of canal occlusion under the flexion and extension position.

Objective: To develop a new type of triple-leaf-enhanced cervical spine plate system, to study its biomechanical properties, perform clinical preliminary applications, and observe clinical effects. Methods: Twelve fresh goat specimens were used, and the high-precision digital display grating displacement sensor system was used to compare the stability, fatigue strength and tensile strength of the fixation of the anterior nailing of the new type of triple-leaf-enhanced cervical spine plate system. All of 92 patients with cervical spondylosis who underwent cervical anterior decompression, cage or titanium mesh fusion, with new PRUNUS spine plate system or Atlantis spine plate system internal fixation were selected from January 2015 to January 2018. Comparative study recorded intraoperative blood loss, operative time, preoperative cervical Cobb angle, pain visual analogue scale (VAS), and Japanese Orthopaedic Association (JOA) spinal function score, and neurological improvement ratewas calculated. Frankel grading was used to evaluate pre and postoperative functional status of the anterior and posterior nerves, so as to comprehensively evaluate the initial clinical efficacy of the new PRUNUS spine plate system. Results: The biomechanical tests showed that: 1) The flexion, extension, left bending, right bending, left rotation and right rotation ROM after fixing with the new PRUNUS spine plate system were 1.02°±0.13°, 1.32°±0.11°, 0.96°±0.23°, 1.03°±0.19°, 1.37°±0.17° and 1.05°±0.08°. ROM after fixation of Atlantis spine plate system were 0.99°±0.11°, 1.08°±0.23°, 0.83°±0.21°, 0.82°±0.13°, 1.18°±0.43°, 1.17°±0.17°, respectively. There was no significant statistical difference between the two groups; 2) The fatigue life of the new PRUNUS spine plate system and Atlantis spine plate system were 6.3×10⁵ and 6.1×10⁵, and the fatigue strengths were 512.12 Mpa and 502.85 Mpa respectively. There was no statistical difference between the two groups. 3) The maximum pull-out force of the new PRUNUS spine plate system was 483.62±39.14 N, and the maximum pull-out force of the Atlantis spine plate system was 396.55±22.79 N. The difference between the two groups was statistically significant. In the clinical application, the new PRUNUS spine plate system was used, the average operation time was 102.8±13.6 min, and the average blood loss was 56.8±14.1 ml. Using the Atlantis spine plate system, the average operation time was 132.8±15.7 min, and the average blood loss was 76.8±19.1 ml. The difference between the two groups was statistically significant; Using the new PRUNUS spine plate system, the VAS score was reduced from 5.42±1.17 before surgery to 1.58±0.44, the preoperative JOA score was 8.13±1.26, and the JOA score was 14.71±1.16 at the last follow-up. Using the Atlantis spine plate system, the VAS score was 6.94±1.06 before surgery. dropped to 1.75±0.35, the preoperative JOA score was 9.26±1.32, and the JOA score was 14.96±1.56 at the last follow-up. There was no significant difference between the two groups. Conclusion The new PRUNUS spine plate system has good biomechanical properties and has a good effect on the stability of the cervical vertebra, especially for the postoperative renovations and osteoporosis patients. The operation is simple and convenient, safe and effective, and worthy of clinical promotion.

0bjective: To explore the feasibility and clinical efficacy of cervical vertebral dome expansion laminoplasty.. Methods: Our hospital from February 2017 to 2018 Sep 16 cases with cervical spinal canal dome of cervical spinal stenosis angioplasty in treatment of cervical spinal cord due to the medical records of patients, including 14 males and 2 females; Aged 49- 76 years old, average age 57.3±1.7 years old. The course of disease was 7-48 months, with an average disease duration 17.75±1.90 months. Of the 16 patients, 5 had multi-segment cervical disc herniation and 11 had long segmental ossification of the posterior longitudinal ligament. All the 16 patients underwent cervical C_3-7 dome-type spinal canal enlargement; the position, stability and spinal cord compression of the internal fixation were evaluated according to the patient's imaging data (X-ray, CT and MRI). The neck and upper extremity pain was evaluated by visual analogue scale (VAS) before and after operation. The cervical spinal cord function was evaluated by the Japanese Orthopaedic Association (JOA) spinal cord function score, and the rate of improvement of neurological function was calculated. The Frankel grading was used to evaluate the neurological function of patients before and after surgery. Results: Cervical X-ray, CT and MRI were performed in all patients before and after surgery. Operation time 55-110 min, mean 65±12 min, bleeding 100-220 ml, mean 110±20 ml. The cross-sectional area of the spinal canal and the median sagittal diameter of the spinal canal were significantly increased compared with the preoperative. All patients were followed up for an average of 10.9±1.4 months (3-20 months). Imaging examination showed that 16 patients had no loosening and fracture after internal fixation, and no re-closure occurred. MRI T2WI images showed continuous recovery of cerebrospinal fluid signal in the spinal cord of C_3-7 range. The preoperative VAS score was 7.3±0.9 points, the average VAS score at the last follow-up was 1.6±0.4 points, the preoperative JOA score was 6.9±1.1 points, and the last follow-up JOA score was 13.4±1.3 points. The improvement rate was 87.23%±3.81%; Frankel grade D before surgery, and Frankel grade E after surgery. Conclusion Cervical spinal canal domed simple angioplasty operation, spinal canal full, satisfactory clinical efficacy, and can effectively reduce the incidence of related complications, it is a safe and feasible method for the treatment of cervical spinal stenosis.