Transoral digital reduction of complete anterior odontoid dislocation followed by fiducial-based navigated transcondylar screw fixation: illustrative case

BACKGROUND Posterior atlantoaxial dislocations (i.e., complete anterior odontoid dislocation) without C1 arch fractures are a rare hyperextension injury most often found in high-velocity trauma patients. Treatment options include either closed or open reduction and optional spinal fusion to address atlantoaxial instability due to ligamentous injury. OBSERVATIONS A 60-year-old male was struck while on his bicycle by a truck and sustained an odontoid dislocation without C1 arch fracture. Imaging findings additionally delineated a high suspicion for craniocervical instability. The patient had neurological issues due to both a head injury and ischemia secondary to an injured vertebral artery. He was stabilized and transferred to our facility for definitive neurosurgical care. LESSONS The patient underwent a successful transoral digital closed reduction and posterior occipital spinal fusion via a fiducial-based transcondylar, C1 lateral mass, C2 pedicle, and C3 lateral mass construct. This unique reduction technique has not been recorded in the literature before and avoided potential complications of overdistraction and the need for odontoidectomy. Furthermore, the use of bone fiducials for navigated screw fixation at the craniocervical junction is a novel technique and recommended particularly for placement of technically demanding transcondylar screws and C2 pedicle screws where pars anatomy is potentially unfavorable.

Subaxial lateral mass prosthesis for posterior reconstruction of cervical spine

Purpose: To obtain the relevant morphometry of the lateral mass of the subaxial cervical spine (C3-C7) and to design a series of lateral mass prostheses for the posterior reconstruction of the stability of cervical spine. Methods: The computed tomography (CT) scans of healthy volunteers were obtained. RadiAnt DICOM Viewer software (Version 2020.1, Medixant, Poland) was used to measure the parameters of lateral mass, such as height, anteroposterior dimension (APD), mediolateral dimension (MLD) and facet joint angle. According to the parameters, a series of cervical lateral mass prostheses were designed. Cadaver experiment was conducted to demonstrate its feasibility. Results: 23 volunteers with an average age of 30.1 ± 7.1 years were enrolled in this study. The height of lateral mass is 14.1 mm averagely. Facet joint angle, APD and MLD of lateral mass averaged 40.1 degrees, 11.2 mm and 12.18 mm, respectively. With these key data, a lateral mass prosthesis consists of a bone grafting column and a posterior fixation plate was designed. The column has a 4.0 mm radius, 41 degrees surface angle and adjustable height of 13, 15, or 17 mm. In the cadaver experiment, the grafting column could function as a supporting structure between adjacent facets, and it would not violate exiting nerve root (NR) or vertebral artery (VA). Conclusion: This study provided detailed morphology of the lateral mass of subaxial cervical spine. A series of subaxial cervical lateral mass prostheses were designed awaiting further clinical application.

Medial Pedicle Pivot Point Using Preoperative Computed Tomography Morphometric Measurements for Cervical Pedicle Screw Insertion: A Novel Technique and Case Series

This study describes a new and safe freehand cervical pedicle screw insertion technique using preoperative computed tomography (CT) morphometric measurements as a guide and a medial pedicle pivot point (MPPP) during the procedure. This study included 271 pedicles at 216 cervical spine levels (mean: 4.75 pedicles per patient). A pedicle diameter (PD) ≥ 3.5 mm was the cut-off for pedicle screw fixation. The presence and grade of perforation were detected using postoperative CT scans, where perforations were graded as follows: 0, no perforation; 1, perforation < 0.875 mm; 2, perforation 0.875–1.75 mm; and 3, perforation > 1.75 mm. The surgical technique involved the use of an MPPP, which was the point at which the lines representing the depth of the lateral mass and total length of the pedicle intersected, deep in the lateral mass. The overall success rate was 96.3% (261/271, Grade 0 or 1 perforations). In total, 54 perforations occurred, among which 44 (81.5%) were Grade 1 and 10 (18.5%) were Grade 2. The most common perforation direction was medial (39/54, 72.2%). The freehand technique for cervical pedicle screw fixation using the MPPP may allow for a safe and accurate procedure in patients with a PD ≥3.5 mm.

Posterior Laminectomy and Lateral Mass Screw Fixation for the Treatment of Severe Cervical Spondylotic Myelopathy

Background Severe and complex cervical spondylotic myelopathy(CSM) requires surgical treatment. The common methods of posterior cervical spine surgery are laminoplasty and laminectomy with lateral mass screw internal fixation. However, the operative effect of this surgical approach is unclear owing to the complexity and severity of CSM in patients who undergo this surgical treatment.Therefore, we aimed to evaluate the clinical effects of posterior cervical laminectomy and lateral mass screw internal fixation in patients with severe and complex CSM. Methods We retrospectively analysed 60patients (48men,12women; mean age59.7 years) with severe and complex CSM who underwent posterior cervical laminectomy and lateral mass screw internal fixation from May 2013 to June 2020. Forty-eight patients underwent laminectomy and lateral mass screw internal fixation;12 patients underwent laminectomy and lateral mass screw internal fixation with 1–2 segmental laminoplasty. C-spine radiographs, computed tomography (CT) scans, and magnetic resonance imaging (MRI) were used to detect any curvature and fusion of the cervical spine, restenosis, and loose/broken internal fixation screws.Clinical efficacy was evaluated using Japanese Orthopaedic Association (JOA)scores, neck disability index(NDI), Odom’s classification, and the visual analogue scale(VAS) for pain. Results Overall effect was satisfactory at the last follow-up (average, 3.6 years [range, 6 months–6 years]), with no restenosis or loosened, slipped, or broken internal fixations. The anterior curvature angle of lordosis (n=46)was not significantly different from baseline at the last follow-up(P>0.05). The cervical kyphosis angle (n=14)was significantly improved at the last follow-up compared with the baseline value (P<0.05), as were the JOA, NDI, and VAS scores(all P<0.05). Odom’s classifications at the last follow-up were excellent, good, and fair in 45, 12, and three patients, respectively. Conclusions Posterior cervical laminectomy and lateral mass screw internal fixation achieved satisfactory clinical results in severe and complex CSM cases.Combining this surgical method with laminoplasty of 1–2 spinal segments stabilised the cervical spine and provided spinal decompression while preventing excessive backward drift of the cervical spinal cord, resulting in fewer complications.

Morphometric Anatomy of the Posterior Aspect of the Atlas and the Vertebral Artery Groove in Relation to Lateral Mass Screw Placement

Background Atlantoaxial instability is an important disorder that causes serious symptoms such as difficulties in walking, limited neck mobility, sensory deficits, etc. Atlantal lateral mass screw fixation is a surgical technique that has gained important recognition and popularity. Because accurate drilling area for screw placement is of utmost importance for a successful surgery, we aimed to investigate morphometry of especially the posterior part of C1. Methods One hundred and fifty-eight human adult C1 dried vertebrae were obtained. Measurements were performed directly on dry atlas vertebrae, and all parameters were measured by using a digital caliper accurate to 0.01 mm for linear measurements. Results The mean distance between the tip of the posterior arch and the medial inner edge of the groove was found to be 10.59 ± 2.26 and 10.49 ± 2.20 mm on the right and left, respectively. The mean distance between the tip of the posterior arch and the anterolateral outer edge of the groove was 21.27 ± 2.28 mm (right: 20.96 ± 2.22 mm; left: 21.32 ± 2.27 mm). The mean height of the screw entry zone on the right and left sides, respectively, were 3.86 ± 0.81 and 3.84 ± 0.77 mm. The mean width of the screw entry zone on both sides was 13.15 ± 1.17 and 13.25 ± 1.3 mm. Conclusion Our result provided the literature with a detailed database for the morphometry of C1, especially in relation to the vertebral artery groove. We believe that the data in the present study can help surgeons to adopt a more accurate approach in terms of accurate lateral mass screw placement in atlantoaxial instability.

Surgical Treatment of Multilevel Degenerative Cervical Myelopathy: Open-Door Laminoplasty and Fixation via Unilateral Approach. A Feasibility Study

Objective We compared open-door laminoplasty via a unilateral approach and additional unilateral lateral mass screw fixation (uLP) with laminectomy and bilateral lateral mass screw fixation (LC) in the surgical treatment of multilevel degenerative cervical myelopathy (mDCM). Methods A retrospective cohort analysis of 46 prospectively enrolled patients (23 uLP and 23 LC). The minimum follow-up was 1 year. Neck and arm pains were evaluated with visual analog scales and disability with the Neck Disability Index (NDI). Myelopathy was rated with the modified Japanese Orthopaedic Association (mJOA) score. Cervical sagittal parameters were measured on plain and functional X-ray films with a specific software. The statistical significance was set at p < 0.05. Fusion was defined as <2 degrees of intersegmental motion on flexion/extension radiographs. Results The two groups were similar in age and comorbidities. The mean operation time and the mean hospital stay were shorter in the uLP group (p = 0.015). The intraoperative blood loss did not exceed 200 mL in both groups. At follow-up, the groups showed comparable clinical outcome data. The sagittal profile did not deteriorate in either group. Fusion rates were 67% in the uLP group and 92% in the LC group. No infections occurred in either group. In the LC group, one patient developed a transient C5 palsy. Revision surgery was required for a malpositioned screw (LC) and for one implant failure (uLP). Conclusion Laminoplasty and unilateral fixation via a unilateral approach achieved comparable clinical and radiologic results with laminectomy and bilateral fixation, despite a lower fusion rate. However, the surgical traumatization was less.