Anterior occipital condyle screw placement through the endonasal corridor: proof of concept study with cadaveric analysis.

PURPOSE: Odontoidectomy for ventral compressive pathology may result in O-C1 and/or C1-2 instability. Same-stage endonasal C1-2 spinal fusion has been advocated to eliminate risks associated with separate-stage posterior approaches. While endonasal methods for C1 instrumentation and C1-2 trans-articular stabilization exist, no hypothetical construct for endonasal occipital instrumentation has been validated. We provide an anatomic description of anterior occipital condyle (AOC) screw endonasal placement as proof-of-concept for endonasal craniocervical stabilization. METHODS: Eight adult, injected cadaveric heads were studied for placing 16 AOC screws endonasally. Thin-cut CT was used for registration. After turning a standard inferior U-shaped nasopharyngeal flap endonasally, 4 mm × 22 mm AOC screws were placed with a 0° driver using neuronavigation. Post-placement CT scans were obtained to determine: site-of-entry, measured from the endonasal projection of the medial O-C1 joint; screw angulation in sagittal and axial planes, proximity to critical structures. RESULTS: Average site-of-entry was 6.88 mm lateral and 9.74 mm rostral to the medial O-C1 joint. Average angulation in the sagittal plane was 0.16° inferior to the palatal line. Average angulation in the axial plane was 23.97° lateral to midline. Average minimum screw distances from the jugular bulb and hypoglossal canal were 4.80 mm and 1.55 mm. CONCLUSION: Endonasal placement of AOC screws is feasible using a 0° driver. Our measurements provide useful parameters to guide optimal placement. Given proximity of hypoglossal canal and jugular bulb, neuronavigation is recommended. Biomechanical studies will ultimately be necessary to evaluate the strength of AOC screws with plate-screw constructs utilizing endonasal C1 lateral mass or C1-2 trans-articular screws as inferior fixation points.

Risk of Infection Associated with Transmucosal Placement of Instrumentation in Clean-Contaminated Field: Systematic Analysis.

Instability of the craniovertebral junction (CVJ) following odontoidectomy is relatively common. Traditionally, separate stage posterior atlantoaxial ± occipitocervical fusion is used for treatment. A transmucosal approach using a clean-contaminated route is associated with hypothetical risks of infectious complications. There is a paucity of information in the literature assessing the risk of surgical site infection (SSI) using the transmucosal approach for hardware placement. The authors conducted a literature search through PubMed identifying patients with pathology requiring transmucosal (i.e., transnasal or transoral) CVJ fixation. Studies that described 1) cases requiring a transmucosal approach and 2) associated infectious complications were included. Rates of SSIs, device removal, unplanned reoperation, and hardware failures were analyzed. Descriptive statistics and odds ratios (ORs) were used to compare complications. Nine studies with a total of 431 patients were identified. There were 4 (0.93%) superficial SSIs and 4 (0.93%) deep SSIs. In total, 1.86% of patients experienced SSI. There were 18 (4.18%) cases of unplanned reoperation, 4 (0.93%) related to SSI. Five (1.16%) patients required removal of their anterior fixation device, 4 (0.93%) related to SSI. ORs comparing our results with Medvedev et al's retrospective National Surgical Quality Improvement Program study assessing the risk associated with posterior cervical fixation showed no statistical difference between postoperative infection rates (OR = 0.72, P = 0.36). An extensive review of the literature found no evidence to suggest placement of spinal hardware via transmucosal corridor is associated with an increased risk of SSI.