This study investigates the mobilization of cranial nerves in the upper clival region to improve surgical approaches. Cadaveric specimens (n = 20) were dissected to examine the oculomotor, trochlear, and abducens nerves. Dissection techniques focused on the nerves' intradural course and their relationship to surrounding structures.
Pre-dissection revealed the nerves' entry points into the clival dura and their proximity to each other. Measurements were taken to quantify these distances. Following intradural dissection, measurements were again obtained to assess the degree of nerve mobilization.
Dissection showed that the abducens nerve takes three folds during its course: at the dural foramen, towards the posterior cavernous sinus, and lastly within the cavernous sinus. The trochlear nerve enters the dura and makes two bends before entering the cavernous sinus. The oculomotor nerve enters the cavernous sinus directly and runs parallel to the trochlear nerve. Importantly, intradural dissection increased the space between the abducens nerves (by 4.21 mm) and between the oculomotor and trochlear nerves (by 3.09 mm on average). This indicates that nerve mobilization can create wider surgical corridors for approaching lesions in the upper clivus region.
This study provides a detailed anatomical analysis of the oculomotor, trochlear, and abducens nerves in the upper clivus. The cadaveric dissections and measurements demonstrate the feasibility of mobilizing these nerves to achieve wider surgical corridors. This information can be valuable for surgeons planning endoscopic or microscopic approaches to lesions in the upper clivus region.
To evaluate both the short-term and long-term outcomes of odontoid screw fixation (OSF), identifying potential risk factors for implant-related complications in patients with odontoid fractures.
This is a retrospective observational cohort study. Inclusion criteria were as follows: 1) Type II fractures and rostral Type III fractures, according to the Anderson and D’Alonzo classification; 2) patients older than 15 years. Exclusion criteria were: 1) other Type III injuries; 2) osteoporosis confirmed by densitometry or a CT bone density score below 100 Hounsfield units; 3) odontoid fractures related to tumors or aneurysmal bone cysts.
In total, 56 patients were considered for the analysis of short-term results, and 26 patients were evaluated for long-term outcomes. No significant differences were observed in the preoperative imaging data and intraoperative features of OSF between patients with Type II and rostral Type III fractures. The mean operative duration was 63.9 ± 20.9 min, and the mean intraoperative blood loss was 22.1 ± 22.9 ml.
Screw cut-out was identified in four patients with rostral Type III fractures (p = 0.04). The rate of screw cut-out was found to correlate with the degree of dens fragment displacement. The bone fusion rate was 95.7%. CT scans identified stable pseudarthrosis in two cases. We observed C2–C3 ankylosis in all cases following partial disc resection. One third of patients with screws placed through the anterior lip of C2 showed no C2–C3 ankylosis. A strong trend towards lateral joint ankylosis formation in patients with a median lateral mass dislocation of 11.9 mm was observed. Most SF-36 scores either matched or exceeded the corresponding normal median values in the published reference database.
OSF is a reliable treatment method of Type II and rostral Type III odontoid fractures with fragment displacement of 4 mm or less. The minimally invasive OSF through the anterior-inferior lip of C2, using monocortical screw placement and cannulated instruments, without rigid intraoperative head immobilization, is sufficient to achieve favorable clinical and fusion results. This technique reduces the risk of ankylosis in the C2–C3 segment. OSF restore the quality of life for patients with odontoid fractures to levels comparable to those of the general population norm.