Introduction: This study aims to investigate risk factors for cage subsidence following minimally invasive lateral corpectomy for osteoporotic vertebral fractures.Methods: Eight males and 13 females (77.2 ± 6.0 years old) with osteoporotic vertebral fractures who underwent single corpectomy using a wide-footprint expandable cage with at least a 1-year follow-up were retrospectively included. The endplate cage (EC) angle was defined as the angle between the vertebral body's endplate and the cage's base on the cranial and caudal sides. A sagittal computed tomography scan was performed immediately after surgery and at the final follow-up, with cage subsidence defined as subsidence of ≥2 mm on the cranial or caudal side. Risk factors were analyzed by dividing cases into groups with (n = 6) and without (n = 15) cage subsidence.Results: No significant differences were noted in age, bone mineral density, number of fixed vertebrae, sagittal parameters, preoperative and final kyphosis angle, amount of kyphosis angle correction, bone union, screw loosening, and number of other vertebral fractures preoperatively and 1-year postoperatively between the two groups. No difference was noted in cranial EC angle, but a significant difference was noted in caudal EC angle in the group with (10.7 ± 4.1°) and without (4.7 ± 4.2°) subsidence (P = 0.008). Logistic regression analysis with the dependent variable as presence or absence of subsidence showed that caudal EC angle (>7.5°) was a significant factor (odds ratio: 20, 95% confidence interval: 1.655–241.7, P = 0.018).Conclusions: In minimally invasive lateral corpectomy for osteoporotic vertebral fractures, a cage tilted more than 7.5° to the caudal vertebral endplate is a risk factor for cage subsidence. The cage should be placed as perpendicular to the endplate as possible, especially to the caudal vertebral body, to avoid cage subsidence.

Computer vision plays an important role in various applications. However, the accuracy of computer vision is often degraded by specular reflection. To solve this problem, a system utilizing a high-speed camera and a strobe for removing specular reflection has been shown to be effective. This method utilizes a principle of estimation using images with luminances varied by the flickering of a strobe. However, the method generates noise due to the difference in position of specular reflection among images in video imaging. In this paper, the authors propose a method combining optical flow with the above-mentioned method. The proposed method enables the removal of specular reflection for video imaging without generating noise. Experimental results and comparison with other methods of specular reflection removal show the effectiveness of the proposed method.