METHODS: Three-dimensional computed tomographies of 180 subjects (60 from each ethnic) were analyzed. The length and angulations of C1LM screw and the location of internal carotid artery (ICA) in relation to C1LM were assessed and classified according to the classification by Murakami et al. The incidence of ponticulus posticus (PP) was determined and the differences among the population of these three ethnics were recorded.
RESULTS: The average base length was 8.5 ± 1.4 mm. The lengths within the lateral mass were between 14.7 ± 1.6 mm and 21.7 ± 2.3 mm. The prevalence of PP was 8.3%. 55.3% (199) of ICA were located in zone 0, 38.3% (138) in zone 1-1, 6.4% (23) in zone 1-2, and none in zone 1-3 and zone 2. The average angulation from the entry point to the ICA was 8.5° ± 6.4° laterally. The mean distance of ICA from C1 anterior cortex was 3.7 ± 1.7 mm (range: 0.6∼11.3). There was no difference in distribution of ICA in zone 1 among the three population (Chinese-47%, Indians-61%, and Malays-53%; p > 0.05).
CONCLUSIONS: No ICA is located medial to the entry point of C1LM screw. If bicortical purchase of C1LM screw is needed, screw protrusion of less than 3 mm or medially angulated is safe for ICA. The incidence of PP is 8.3% with higher prevalence among the Indian population.
PURPOSE: To study the surgical morphometry of C1 and C2 vertebrae in Chinese, Indian, and Malay patients.
OVERVIEW OF LITERATURE: C1 lateral mass and C2 pedicle screw fixation is gaining popularity. However, there is a lack of C1-C2 morphometric data for the Asian population.
METHODS: Computed tomography analysis of 180 subjects (60 subjects each belonging to Chinese, Indian, and Malay populations) using simulation software was performed. Length and angulations of C1 lateral mass (C1LM) and C2 pedicle (C2P) screws were assessed.
RESULTS: The predicted C1LM screw length was between 23.2 and 30.2 mm. The safe zone of trajectories was within 11.0°±7.7° laterally to 29.1°±6.2° medially in the axial plane and 37.0°±10.2° caudally to 20.9°±7.8° cephalically in the sagittal plane. The shortest and longest predicted C2P screw lengths were 22.1±2.8 mm and 28.5±3.2 mm, respectively. The safe trajectories were from 25.1° to 39.3° medially in the axial plane and 32.3° to 45.9° cephalically in the sagittal plane.
CONCLUSIONS: C1LM screw length was 23-30 mm with the axial safe zone from 11° laterally to 29° medially and sagittal safe zone at 21° cephalically. C2P screw length was 22-28 mm with axial safe zone from 26° to 40° medially and sagittal safe zone from 32° to 46° cephalically. These data serve as an important reference for Chinese, Indian, and Malay populations during C1-C2 instrumentation.
METHODS: 104 AIS patients with 1524 pedicle screws were evaluated using CT scan. 302 screws were inserted in dysplastic pedicles using fluoroscopic guidance technique. 155 screws were inserted using a cannulated system (Group 1), whereas 147 screws were inserted using standard screws (Group 2). The pedicle perforations were assessed using a classification by Rao et al.; G0: no violation; G1: <2 mm perforation; G2: 2-4 mm perforation; and G3: >4 mm perforation). For anterior perforations, the pedicle perforations were assessed using a modified grading system (Grade 0: no violation, Grade 1: less than 4 mm perforation; Grade 2: 4 mm to 6 mm perforation; and Grade 3: more than 6 mm perforation).
RESULTS: The perforation rate in Group 1 was 4.5% and in Group 2 was 15.6% (p = 0.001). Most of the perforations were anterior perforations (53.3%). The anterior perforation rate in Group 1 was 1.9% compared to 8.8% in Group 2 (p = 0.009). Group 1 has a medial perforation rate of 1.3% compared to Group 2, 6.1% (p = 0.031). The rate of critical pedicle perforation in Group 1 was 2.6% and in Group 2 was 6.8% (p = 0.102). In Group 1, there were no critical medial perforation but there was one G2 lateral perforation, one G2 superior perforation and two G3 anterior perforations. In Group 2, there were three G2 medial perforations, one G2 lateral perforation, one G2 anterior perforation and five G3 anterior perforations.
CONCLUSION: Usage of cannulated screw system significantly increases the accuracy of pedicle screw insertion in dysplastic pedicles in AIS.
PURPOSE: To evaluate the feasibility of a novel trajectory for C7 laminar screws and to compare it with an old trajectory.
OVERVIEW OF LITERATURE: The previously reported trajectory of C7 laminar screws has a horizontal direction without a fixed target point. Our new trajectory has a cephalad direction with a fixed target point.
METHODS: Computed tomographic scans of a total of 50 male and 50 female patients were utilized. The placement of C7 laminar screws was activated employing the new and old trajectories. The success rate, the causes of failure, and the maximum allowable length of each trajectory were compared.
RESULTS: Employing the new trajectory, the success rates of the unilaminar and bilaminar screws were 93% and 83%, respectively, which were significantly better than the old trajectory (80%, p<0.0001 and 70%, p=0.0003). The most prevalent cause of failure was laminar cortical breach followed by facet joint violation. The new trajectory also offered significantly longer maximum allowable screw length in unilaminar (32.5±4.3 mm vs. 26.5±2.6 mm, p<0.001), bilaminar cephalic (29.5±3.8 mm vs. 25.9±2.6 mm, p<0.0001) and bilaminar caudal (33.1±2.6 mm vs. 25.8±3.1 mm, p<0.001) screws than the old trajectory. With the new and old trajectories, 70% vs. 6% of unilaminar, 60% vs. 2% of bilaminar caudal, and 32% vs. 4% of bilaminar cephalic screws could be protracted perfectly into the corresponding lateral mass without any laminar cortical or facet joint violation (p<0.0001).
CONCLUSIONS: The novel trajectory possesses a substantially higher success rate, longer maximum allowable screw length, and higher chance to be extended into the lateral mass (a condition known as a lamino-lateral mass screw) than the old trajectory.
Methods: Consecutive patients with PCD were identified from the HKIBDR, and disease characteristics, treatments, and outcomes were analysed. The risks for medical and surgical therapies were assessed using Kaplan-Meier analysis.
Results: Among 981 patients with CD with 10530 patient-years of follow-up, 283 [28.8%] had perianal involvement, of which 120 [42.4%] were as first presentation. The mean age at diagnosis of PCD was 29.1 years, and 78.8% were male. The median follow-up duration was 106 months (interquartile range [IQR]: 65-161 months]. Perianal fistula [84.8%] and perianal abscess [52.7%] were the two commonest forms. Male, younger age at diagnosis of CD, and penetrating phenotypes were associated with development of PCD in multivariate analysis. Of 242 patients with fistulizing PCD, 70 [29.2%] required ≥5 courses of antibiotics, and 98 [40.5%] had ≥2 surgical procedures. Nine patients required defunctioning surgery and 4 required proctectomy. Eighty-four patients [34.7%] received biologics. Cumulative probabilities for use of biologics were 4.7%, 5.8%, and 8.6% at 12 months, 36 months, and 96 months, respectively, while the probabilities for surgery were 67.2%, 71.6%, and 77.7%, respectively. Five mortalities were recorded, including 2 cases of anal cancer, 2 CD-related complications, and one case of pneumonia.
Conclusion: Over 40% of CD patients presented with perianal disease at diagnosis. Patients with PCD had poor outcome, with young age of onset, multiple antibiotic use, and repeated surgery.