Current Concepts of Cervical Spine Alignment, Sagittal Deformity, and Cervical Spine Surgery.

There are not many reports on cervical spine alignment, and only a few analyze ideal surgical approaches and optimal amounts of correction needed for the various types of deformity. We comprehensively reviewed the present literature on cervical spinal deformities (with or without myelopathy) and their surgical management to provide a framework for surgical planning. A general assessment of the parameters actually in use and correlations between cervical and thoracolumbar spine alignment are provided. We also analyzed posterior, anterior, and combined cervical surgical approaches and indications for the associated techniques of laminoplasty, laminectomy and fusion, and anterior cervical discectomy and fusion. Finally, on the basis of the NDI, SF-36, VAS, and mJOA questionnaires, we fully evaluated the outcomes and measures of postoperative health-related quality of life. We found the need for additional prospective studies to further enhance our understanding of the importance of cervical alignment when assessing and treating cervical deformities with or without myelopathy. Future studies need to focus on correlations between cervical alignment parameters, disability scores, and myelopathy outcomes. Through this comprehensive literature review, we offer guidance on practical and important points of surgical technique, cervical alignment, and goals surgeons can meet to improve symptoms in all patients.

Transcranial Magnetic Stimulation in the Diagnosis of Compressive Myelopathy at the Thoracolumbar Junction.

PURPOSE: The disc level in the thoracolumbar junction at which measurement of the central motor conduction time in the lower limbs (CMCT-LL) is useful for a diagnosis remains unclear. Therefore, this study investigated the spinal vertebral level at which compressive myelopathy due to ossification of the ligamentum flavum in the thoracolumbar junction is detectable using CMCT-LL. METHODS: We preoperatively measured CMCT-LL in 57 patients (42 men, 15 women; aged 35-85 years) with a single ossification of the ligamentum flavum from the T10-11 to T12-L1 disc levels and in 53 healthy controls. Motor evoked potentials after transcranial magnetic stimulation, compound muscle action potentials, and F waves were recorded from the abductor hallucis. Central motor conduction time in the lower limbs was calculated as follows: Motor evoked potential latency - (compound muscle action potential latency + F latency - 1)/2 (ms). Central motor conduction time in the lower limbs was compared between patients and controls. RESULTS: Compressive lesions were located at the T10 to 11 level in 27 patients, the T11 to 12 level in 28, and the T12-L1 level in 2. Central motor conduction time values in the lower limbs at the T10 to 11 level (19.9 ± 4.7 ms) and T11 to 12 level (18.1 ± 3.4 ms) were significantly longer than control values (11.8 ± 1.1 ms; P < 0.01). Central motor conduction time in the lower limbs was not calculated at the T12-L1 level because motor evoked potentials were not recorded in any patient. CONCLUSIONS: We confirmed that CMCT-LL was significantly longer in patients with ossification of the ligamentum flavum at the T10 to 11 and T11 to 12 levels because the S2 segment of the spinal cord is caudal at the T12 vertebral body level. Therefore, CMCT-LL is useful for diagnosing thoracolumbar junction disorders proximal to the T12 vertebral body level.

Utilization of condoliase therapy versus surgery for lumbar disc herniation and comparison of post-treatment motor improvement.

STUDY DESIGN: Double-center retrospective study. PURPOSE: Utilization trends in interventional treatment for lumbar disc herniation (LDH) have not yet been examined. Furthermore, limited information is currently available on motor recovery with condoliase therapy. Therefore, the present study investigated utilization trends in treatment for LDH and the effects of condoliase therapy on muscle weakness. METHODS: This retrospective, double-center study involved patients with leg pain caused by LDH who received interventional treatment between September 2017 and August 2022. LDH patients were divided into two groups: an operative treatment group and condoliase therapy group. The period between September 2017 and August 2022 was divided into 5 equal parts and changes in the percentage of intervention treatment were examined. Motor recovery was also assessed in the two groups. Patients receiving condoliase therapy were divided into two groups: an effective group and non-effective group. Sex, age, the body mass index, duration of symptoms, herniation level, neurological and radiographic findings, a visual analog scale for leg pain, and the Oswestry disability index were examined in the two groups. RESULTS: Subjects included 226 males and 115 females with a mean age of 49.2 years, mean BMI of 22.8, and mean duration of symptoms of 5.0 months. The utilization of condoliase therapy for LDH surpassed surgery in the third year after its introduction. In the fourth year, condoliase therapy became the main treatment for LDH. Lower limb muscle strength improved in 76 % of cases receiving condoliase therapy. CONCLUSIONS: Condoliase therapy has become an intermediate treatment before surgery in our institutions. Motor recovery in patients receiving condoliase therapy was not inferior to that after surgery; however, in cases with severe muscle weakness with manual muscle test ≤3, the improvement rate was approximately 60 %. These results will be useful for clinicians when providing informed consent and selecting condoliase therapy.

Patient-specific mechanical analysis of pedicle screw insertion in simulated osteoporotic spinal bone models derived from medical images.

Study Design: Biomechanical study. Purpose: To investigate the mechanical characteristics of bone models created from medical images. Overview of Literature: Recent advancements in three-dimensional (3D) printing technology have affected its application in surgery. However, a notable gap exists in the analyses of how patient's dimorphism and variations in vertebral body anatomy influence the maximum insertional torque (MIT) and pullout strength (POS) of pedicle screws (PS) in osteoporotic vertebral bone models derived from medical images. Methods: Male and female patients with computed tomography data were selected. Dimensions of the first thoracic (T1), fourth lumbar (L4), and fifth lumbar (L5) vertebrae were measured, and bone models consisting of the cancellous and cortical bones made from polyurethane foam were created. PS with diameters of 4.5 mm, 5.5 mm, and 6.5 mm were used. T1 PS were 25 mm long, and L4 and L5 PS were 40 mm long. The bone models were secured with cement, and the MIT was measured using a calibrated torque wrench. After MIT testing, the PS head was attached to the machine's crosshead. POS was then calculated at a crosshead speed of 5 mm/min until failure. Results: The L4 and L5 were notably larger in female bone models, whereas the T1 vertebra was larger in male bone models. Consequently, the MIT and POS for L4 and L5 were higher in female bone models across all PS diameters than in male bone models. Conversely, the MIT for T1 was higher in male bone models across all PS; however, no significant differences were observed in the POS values for T1 between sexes. Conclusions: The mechanical properties of the proposed bone models can vary based on the vertebral structure and size. For accurate 3D surgical and mechanical simulations in the creation of custom-made medical devices, bone models must be constructed from patientspecific medical images.

Effect of posterior decompression on the spinal cord in thoracic ossification of the posterior longitudinal ligament: A Finite element analysis.

OBJECTIVE: Thoracic ossification of the posterior longitudinal ligament (T-OPLL) causes myelopathy. Although posterior decompression for T-OPLL has shown positive results, patients with kyphotic curvatures often endure poor outcomes. Posterior decompression with fusion (PDF) has demonstrated better results compared to posterior decompression alone. This study aims to evaluate the effects of the posterior procedures for T-OPLL. METHODS: A 3-dimensional finite element model of the C2-T12 spine, created from medical images, was used to develop the following T3-T4 OPLL compression models: an intact model (no surgery), 25% canal occupancy ratio (COR) OPLL (C25 OPLL), a discontinuous 25% COR OPLL (D25 OPLL), a continuous 50% COR OPLL (C50 OPLL), and a discontinuous 50% COR OPLL (D50 OPLL). These models were analyzed to evaluate the effects of posterior decompression (laminectomy: LN) with varied fixation lengths (LN T3-T4, PDF T3-T4, LN T2-T5, and PDF T2-T5) in neutral, flexion, and extension positions. RESULTS: Increased discontinuity in OPLL led to increased stress on the spinal cord. Posterior decompression reduced spinal cord stress in the neutral posture. However, in flexion and extension, spinal cord stress increased for LN T3-T4, LN T2-T5, and PDF T3-T4 compared to the neutral posture. Notably, PDF T2-T5 prevented an increase in spinal cord stress during these motions. CONCLUSIONS: Effective management of intervertebral mobility and the appropriate length of decompression are crucial for addressing the thickness and mobility of T-OPLL.