Distribution characteristics of stress on the vertebrae following different ranges of excision during Modified Anterior Cervical Discectomy and Fusion: A correlation study based on finite element analysis.

BACKGROUND: Modified Anterior Cervical Discectomy and Fusion with specific resection ranges is an effective surgical method for the treatment of focal ossification of the posterior longitudinal ligament (OPLL). Herein, we compare and analyse the static stress area distribution by performing different cuts on an original ideal finite element model. METHOD: A total of 96 groups of finite element models of the C4-C6 cervical spine with different vertebral segmentation ranges (width: 1-12 mm, height: 1-8 mm) were established. The same pressure direction and size were applied to observe the size and distribution area of stress following various ranges of excision of the C5 vertebral body. RESULTS: Different cutting areas had similar stress aggregation points. As the contact area decreased, the stress and the bearing above area increased. The correlation of stress area variation was highest between the 1-2 MPa and 6 MPa-Max regions (Rho = - 0.975). In the surface visualisation model fitting, the width and height were of different ratios in different stress regions. The model with the best fitting degree was the 1-2 MPa group, and the equation fitting (Rho = 0.966) was as follows: Area = 908.80 - 25.92 × Width + 2.71 × Height. CONCLUSION: Modified Anterior Cervical Discectomy and Fusion with different resection ranges exhibited different stress areas. In a specific resection range of the cervical spine (1-12 mm, 0-8 mm), area conversion occurred at a threshold of 4 MPa. Additionally, the stress was concentrated at the contact points between the vertebral body and the rigid fixator.

Modified ACDF Technique for the Treatment of Centrum Focal Ossification of the Posterior Longitudinal Ligament: A Case Report.

BACKGROUND: Anterior cervical discectomy fusion (ACDF) is a surgical procedure used to treat cervical spondylosis with anterior spinal cord compression. However, there are limitations to traditional ACDF and posterior indirect decompression when the anterior source lesion is in the center of the cervical vertebra. CASE PRESENTATION: On June 8, 2022, our department treated a patient with cervical spondylotic myelopathy-whose high posterior longitudinal ligament (OPLL) occupied the central position of the vertebral body-with modified ACDF. The preoperative surgical plan was designed based on the relevant imaging data and assay index. Also, the visual analogue scale (VAS), Japanese Orthopaedic Association (JOA) scores, and imaging parameters of neck pain were recorded and compared. Postoperative imaging data showed that cervical curvature was recovered and spinal canal compression was relieved. The VAS score for neck pain decreased from 7 preoperatively to 1.5 at the last follow-up, while the JOA score increased from 10 preoperatively to 29 at the last follow-up. The volume of the spinal canal was restored. Simultaneously, the patient's extremity muscle strength improved and muscle tension decreased. CONCLUSIONS: Modified ACDF may be an effective surgical method for resolving spinal cord compression in a specific location when bone mineral density is good. We can effectively avoid iatrogenic nerve injury and symptom recurrence by removing the vertebral body and the lesion directly.

Static mechanical analysis of the vertebral body after modified anterior cervical discectomy and fusion (partial vertebral osteotomy): a finite element model.

BACKGROUND: Modified anterior cervical discectomy and fusion (Mod ACDF) can effectively address ossification of the posterior longitudinal ligament (OPLL), which is difficult to remove directly from the posterior edge of the vertebral body, with considerably lesser damage as compared to anterior cervical corpectomy and fusion (ACCF). We compared the static mechanics of different anterior approaches by using an ideal finite element model. METHODS: A complete finite element model was established and classified into the following three surgical models according to different model cutting operations: ACDF, ACCF, and Mod ACDF. Three different bone volume situations (normal bone mineral density, osteopenia, and osteoporosis) were simulated. After fixing the lower surface of C5 or C6, a load was applied to the upper surface of C4, and the stress distribution and displacement of the upper surface of C5 or C6 were observed and the related values were recorded. RESULTS: The average Von Mises Stress and displacement levels of Mod ACDF were between those of ACDF and ACCF; with the peak Von Mises Stress occurring on the posterior side of the vertebral body (Points 1-4). The change in Von Mises Stress of the vertebral body is not significant during bone loss. However, the degree of displacement of the vertebral body surface and risk of vertebral collapse are increased (100 N: 13.91 vs. 19.47 vs. 21.62 µm; 150 N: 19.60 vs. 29.30 vs. 31.64 µm; 200 N: 28.53 vs. 38.65 vs. 44.83 µm). CONCLUSIONS: The static biomechanical effects caused by Mod ACDF are intermediate between ACDF and ACCF, and the risk of vertebral body collapse is lower than that by ACCF. Therefore, Mod ACDF may be an effective solution when targeting OPLL with poorly positioned posterior vertebral body edges.