Review of mechanisms of expandable spine surgery devices.

INTRODUCTION: Expandable devices such as interbody cages, vertebral body reconstruction cages, and intravertebral body expansion devices are frequently utilized in spine surgery. Since the introduction of expandable implants in the early 2000s, the variety of mechanisms that drive expansion and implant materials have steadily increased. By examining expandable devices that have achieved commercial success and exploring emerging innovations, we aim to offer an in-depth evaluation of the different types of expandable cages used in spine surgery and the underlying mechanisms that drive their functionality. AREAS COVERED: We performed a review of expandable spinal implants and devices by querying the National Library of Medicine MEDLINE database and Google Patents database from 1933 to 2024. Five major types of mechanical jacks that drive expansion were identified: scissor, pneumatic, screw, ratchet, and insertion-expansion. EXPERT OPINION: We identified a trend of screw jack mechanism being the predominant machinery in vertebral body reconstruction cages and scissor jack mechanism predominating in interbody cages. Pneumatic jacks were most commonly found in kyphoplasty devices. Critically reviewing the mechanisms of expansion and identifying trends among effective and successful cages allows both surgeons and medical device companies to properly identify future areas of development.

Slow blood-flow in the left atrial appendage is associated with stroke in atrial fibrillation patients.

Background: Atrial fibrillation (AF) patients are at high risk of stroke with ∼90% clots originating from the left atrial appendage (LAA). Clinical understanding of blood-flow based parameters and their potential association with stroke for AF patients remains poorly understood. We hypothesize that slow blood-flow either in the LA or the LAA could lead to the formation of blood clots and is associated with stroke for AF patients. Methods: We retrospectively collected cardiac CT images of paroxysmal AF patients and dichotomized them based on clinical event of previous embolic event into stroke and non-stroke groups. After image segmentation to obtain 3D LA geometry, patient-specific blood-flow analysis was performed to model LA hemodynamics. In terms of geometry, we calculated area of the pulmonary veins (PVs), mitral valve, LA and LAA, orifice area of LAA and volumes of LA and LAA and classified LAA morphologies. For hemodynamic assessment, we quantified blood flow velocity, wall shear stress (WSS, blood-friction on LA wall), oscillatory shear index (OSI, directional change of WSS) and endothelial cell activation potential (ECAP, ratio of OSI and WSS quantifying slow and oscillatory flow) in the LA as well as the LAA. Statistical analysis was performed to compare the parameters between the groups. Results: Twenty-seven patients were included in the stroke and 28 in the non-stroke group. Examining geometrical parameters, area of left inferior PV was found to be significantly higher in the stroke group as compared to non-stroke group (p = 0.026). In terms of hemodynamics, stroke group had significantly lower blood velocity (p = 0.027), WSS (p = 0.018) and higher ECAP (p = 0.032) in the LAA as compared to non-stroke group. However, LAA morphologic type did not differ between the two groups. This suggests that stroke patients had significantly slow and oscillatory circulating blood-flow in the LAA, which might expose it to potential thrombogenesis. Conclusion: Slow flow in the LAA alone was associated with stroke in this paroxysmal AF cohort. Patient-specific blood-flow analysis can potentially identify such hemodynamic conditions, aiding in clinical stroke risk stratification of AF patients.

Predictors of surgical site infection in glioblastoma patients undergoing craniotomy for tumor resection.

OBJECTIVE: Surgical site infections (SSIs) burden patients and healthcare systems, often requiring additional intervention. The objective of this study was to identify the relationship between preoperative predictors inclusive of scalp incision type and postoperative SSI following glioblastoma resection. METHODS: The authors retrospectively reviewed cases of glioblastoma resection performed at their institution from December 2006 to December 2019 and noted preoperative demographic and clinical presentations, excluding patients missing these data. Preoperative nutritional indices were available for a subset of cases. Scalp incisions were categorized as linear/curvilinear, reverse question mark, trapdoor, or frontotemporal. Patients were dichotomized by SSI incidence. Multivariable logistic regression was used to determine predictors of SSI. RESULTS: A total of 911 cases of glioblastoma resection were identified, 30 (3.3%) of which demonstrated postoperative SSI. There were no significant differences in preoperative malnutrition or number of surgeries between SSI and non-SSI cases. The SSI cases had a significantly lower preoperative Karnofsky Performance Status (KPS) than the non-SSI cases (63.0 vs 75.1, p < 0.0001), were more likely to have prior radiation history (43.3% vs 26.4%, p = 0.042), and were more likely to have received steroids both preoperatively and postoperatively (83.3% vs 54.5%, p = 0.002). Linear/curvilinear incisions were more common in non-SSI than in SSI cases (56.9% vs 30.0%, p = 0.004). Trapdoor scalp incisions were more frequent in SSI than non-SSI cases (43.3% vs 24.2%, p = 0.012). On multivariable analysis, a lower preoperative KPS (OR 1.04, 95% CI 1.02-1.06), a trapdoor scalp incision (OR 3.34, 95% CI 1.37-8.49), and combined preoperative and postoperative steroid administration (OR 3.52, 95% CI 1.41-10.7) were independently associated with an elevated risk of postoperative SSI. CONCLUSIONS: The study findings indicated that SSI risk following craniotomy for glioblastoma resection may be elevated in patients with a low preoperative KPS, a trapdoor scalp incision during surgery, and steroid treatment both preoperatively and postoperatively. These data may help guide future operative decision-making for these patients.