OBJECTIVE: To compare a range of clinical outcome variables (intraocular pressure, glaucoma medications, visual acuity, and complications) between two Ahmed glaucoma valve (AGV) models (S2 and FP7).
METHODS: This was a prospective and randomized clinical trial. Fifty-six patients with refractory glaucoma were randomly assigned to be implanted with either a polypropylene (S2) or silicone (FP7) Ahmed glaucoma valve. The primary outcome measure was a surgical success, defined as an IOP ≤ 16 mm Hg (without medication), and guarded success, defined as a controlled IOP ≤ 16 mmHg (with medication). Failure was defined as when the IOP lay outside of the successful range on two consecutive visits (>16 mmHg, despite medication).
RESULTS: Mean follow-up period was 398.42 ± 12.34 days (range, 380-420 days) for the S2 group and 401.75 ± 9.78 days (range, 385-420 days) for the FP7 group; these values were not significantly different (P = 0.27). After 12 months of follow-up, the baseline IOP (45.42 mmHg) fell significantly to 16.14 mmHg in the S2 group (p < 0.000); there was also a significant reduction in IOP in the FP7 group (from 44.17 mmHg to 15.18 mmHg in FP7 group, p < 0.000). At the last follow-up examination, the mean IOP in the S2 group was 16.14 ± 3.18 mmHg, while that of the FP7 group was 15.18 ± 2.75 mmHg; there was no significant difference between the two groups with this respect (p = 0.23). The mean number of medications used by patients in the S2 and FP7 groups was 2.92 ± 1.27 and 2.75 ± 1.43, respectively; there was no significant difference between the two groups with this respect (p = 0.32). There was no significant difference between the FP7 and S2 groups with regard to their relative success rate (17.89% [5/28] versus 10.7% [3/28], respectively; p = 0.38).
CONCLUSIONS: Our data show that the S2 and FP7 models of AGV were both effective in lowering IOP and reducing the need for glaucoma medications. Although these two AGV models had similar dimensions, they were constructed from different materials. However, there were no significant clinical differences between the S2 and FP7 AGV groups after 12 months of follow-up. Furthermore, our data indicate that bleb encapsulation was the primary factor responsible for failure rate and the need for glaucoma medication in both the S2 and FP7 groups. Our analysis further indicates that the S2 and FP7 Ahmed valves are associated with a high risk of failure when considered as a first-line therapy for cases experiencing trabeculectomy.
BACKGROUND: NCT04214847.

OBJECTIVE: S2 alar screw would be an alternative choice without breaking the sacroiliac joint. The aim of this study was to measure radiographic parameters for optimal placement of posterior S2 alar screw for instrumentation and fusion.
METHODS: Three-dimensional computed tomography scans of the pelvis of 60 normal adults were used to map the S2 alar screw. Entry point was typically chosen lateral and superior to the S2 dorsal foramen. Ideal S2 alar screw trajectories were explored by rotating the three-dimensional pelvis, while ensuring trajectories were of maximum length and width. After identification of an optimal trajectory, related linear anatomic parameters and sagittal and transverse angles were determined.
RESULTS: Ideal S2 alar screw trajectories were identified in each computed tomography scan. According to this morphometric study, trajectories for female patients were more lateral in the transverse plane (female 33.73 ± 5.99° vs. male 29.82 ± 4.11°, P < 0.001). Maximal length of trajectory in male patients was significantly longer than in female patients (female 40.82 ± 4.29 mm vs. male 43.42 ± 4.02 mm, P = 0.001). Fourteen S2 alar screws were used in 7 patients with high-grade spondylolisthesis, scoliosis, or nonunion at lumbosacral site. No complications occurred during S2 alar screw placement. One S2 screw failed owing to severe local osteoporosis. No patient developed local pain or wound-related problems.
CONCLUSIONS: S2 alar screw is an alternative sacral fixation point to provide additional biomechanical stability of lumbosacral constructs. A trajectory with maximum length through the S2 ala can be determined using three-dimensional computed tomography.