Development of a new critical size defect model in the paranasal sinus and first approach for defect reconstruction-An in vivo maxillary bone defect study in sheep.

Fractures of the paranasal sinuses often require surgical intervention. Persisting bone defects lead to permanent visible deformities of the facial contours. Bone substitutes for reconstruction of defects with simultaneous induction of new bone formation are not commercially available for the paranasal sinus. New materials are urgently needed and have to be tested in their future area of application. For this purpose critical size defect models for the paranasal sinus have to be developed. A ≥2.4 cm large bilateral circular defect was created in the anterior wall of the maxillary sinus in six sheep via an extraoral approach. The defect was filled with two types of an osteoconductive titanium scaffold (empty scaffold vs. scaffold filled with a calcium phosphate bone cement paste) or covered with a titanium mesh either. Sheep were euthanized after four months. All animals performed well, no postoperative complications occured. Meshes and scaffolds were safely covered with soft tissue at the end of the study. The initial defect size of ≥2.4 cm only shrunk minimally during the investigation period confirming a critical size defect. No ingrowth of bone into any of the scaffolds was observed. The anterior wall of the maxillary sinus is a region with low complication rate for performing critical size defect experiments in sheep. We recommend this region for experiments with future scaffold materials whose intended use is not only limited to the paranasal sinus, as the defect is challenging even for bone graft substitutes with proven osteoconductivity. Graphical abstract.

Predictors and impact of early cerebral infarction after aneurysmal subarachnoid hemorrhage.

BACKGROUND AND PURPOSE: Cerebral infarction is a frequent and serious complication of aneurysmal subarachnoid hemorrhage (SAH). This study aimed to identify independent predictors of the timing of cerebral infarction and clarify its impact on disease course and patients' outcome. METHODS: All consecutive patients with SAH admitted to our institution from January 2005 to December 2012 were analyzed. Serial computed tomography (CT) scans were evaluated for cerebral infarctions. Demographic, clinical, laboratory and radiological data of patients during hospitalization as well as clinical follow-ups 6 months after SAH were recorded. RESULTS: Of the 632 analyzed patients, 320 (51%) developed cerebral infarction on CT scans. 136 patients (21.5%) with early cerebral infarction (occurring within 3 days after SAH) had a significantly higher risk of unfavorable outcome than patients with late infarction [odds ratio (OR) 2.94; P = 0.008], a higher in-hospital mortality (OR 3.14; P = 0.0002) and poorer clinical outcome after 6 months (OR 0.54; P < 0.0001). The rates of decompressive craniectomy (OR 1.96, P = 0.0265), tracheostomy (OR 1.87, P = 0.0446), the duration of intensive care unit stay and mechanical ventilation were significantly higher in patients with early infarction. In multivariate analysis, Hunt and Hess grades 4 and 5 (OR 2.06, P = 0.008), Fisher grades 3 and 4 (OR 3.99, P = 0.014), sustained elevations of intracranial pressure >20 mmHg (OR 5.95, P < 0.0001) and early vasospasm on diagnostic angiograms (OR 3.01, P = 0.008) were predictors of early cerebral infarction. CONCLUSION: Early cerebral infarction after SAH is associated with severe clinical course and unfavorable outcome and can be reliably predicted by poor initial clinical condition, thick subarachnoid clot, early angiographic vasospasm and sustained elevations of intracranial pressure.

Piezosurgery for safe and efficient petrous bone cutting in cerebellopontine angle and petroclival meningioma surgery.

Intradural petrous bone drilling has become a widespread practice, providing extended exposure in the removal of cerebellopontine angle (CPA) or petroclival tumors. Adjacent neurovascular structures are at risk, however, when drilling is performed in this deep and narrow area. Hence, this study evaluates the use of Piezosurgery (PS) as a non-rotating tool for selective bone cutting in CPA surgery. A Piezosurgery® device was used in 36 patients who underwent microsurgery for extra-axial CPA or petroclival tumors in our Neurosurgical Department between 2013 and 2019. The clinical and radiological data were retrospectively analyzed. The use of PS was evaluated with respect to the intraoperative applicability and limitations as well as efficacy and safety of the procedure. Piezosurgical petrous bone cutting was successfully performed in the removal of meningiomas or extra-axial metastases arising from the dura of the petroclival region (21 patients) or petrous bone (15 patients). PS proved to be very helpful in the deep and narrow CPA region, considerably reducing the surgeon's distress toward bone removal in close proximity to cranial nerves and vessels in comparison to common rotating drills. The use of PS was safe without injuries to neurovascular structures. Gross total resection was achieved in 67% of petroclival and 100% of petrous bone tumors. Piezosurgery proved to be an effective and safe method for selective petrous bone cutting in CPA surgery avoiding rotating power and associated risks. This technique can particularly be recommended for bone cutting in close vicinity to critical neurovascular structures.

Determining the Orientation of Directional Deep Brain Stimulation Electrodes Using 3D Rotational Fluoroscopy.

BACKGROUND AND PURPOSE: New deep brain stimulation leads with electrode contacts that are split along their circumference allow steering of the electrical field in a predefined direction. However, imaging-assisted directional stimulation requires detailed knowledge of the exact orientation of the electrode array. The purpose of this study was to evaluate whether this information can be obtained by rotational 3D fluoroscopy. MATERIALS AND METHODS: Two directional leads were inserted into a 3D-printed plaster skull filled with gelatin. The torsion of the lead tip versus the lead at the burr-hole level was investigated. Then, 3 blinded raters evaluated 12 3D fluoroscopies with random lead orientations. They determined the lead orientation considering the x-ray marker only and considering the overlap of the gaps between the contact segments. Intraclass correlation coefficients and an extended version of the Bland-Altman plot were used to determine interrater reliability and agreement of the measurements of the different raters. RESULTS: Electrode torsion of up to 35° could be demonstrated. Evaluation of the lead rotation considering the x-ray marker only revealed limits of agreement of ±9.37° and an intraclass correlation coefficient of 0.9975. In addition, taking into account the lines resulting from overlapping of the gaps between the electrode segments, the limits of agreement to the mean were ±2.44° and an intraclass correlation coefficient of 0.9998. CONCLUSIONS: In directional deep brain stimulation systems, rotational 3D fluoroscopy combined with the described evaluation method allows for determining the exact orientation of the leads, enabling the full potential of imaging-assisted personalized programming.