To ensure adequate function after orthopedic tumor reconstruction, it is important to reattach the remaining soft tissue to the implant. This study aimed at obtaining mechanical properties of textile muscle-implant and muscle-bone connections in a preliminary test. Two groups of soft-tissue attachment were mechanically tested and compared: Native bone-muscle samples obtained from human femora and muscles attached to a prosthetic implant by means of Trevira® attachment tubes. Additionally, muscle samples were tested with muscle fibers aligned parallel and perpendicular to the tension load. A uniaxial load was exerted upon all samples. Failure loads of 26.7 ± 8.8 N were observed for the native bone-muscle group and of 18.1 ± 9.9 N for the Trevira® group. Elongations of 94.8 ± 36.2 % were observed for the native bone-muscle group and 79.3 ± 51.8 % for the Trevira® group. The location of failure was mainly observed in the central area of the muscle fibers. Muscle fibers with parallel fiber orientation (47.6 ± 11.5 N) yielded higher tensile strength than those with perpendicular fiber orientation (14.8 ± 4.1 N). Our experiments showed that higher forces were transmitted in the origin and insertion areas than in areas of flat soft tissue reconstruction using attachment tubes. The data indicate that the tested material allows reattaching muscles, but without reinforcing the insertion site. Therefore, attachment tubes with region-dependent and potentially anisotropic material behavior might be advantageous to optimize muscle-bone load transmission after surgery, which may allow lower complication rates and shorter physical recovery.

OBJECTIVE: The placement of a ventricular catheter, that is, an external ventricular drain (EVD), is a common and essential neurosurgical procedure. In addition, it is one of the first procedures performed by inexperienced neurosurgeons. With or without surgical experience, the placement of an EVD according to anatomical landmarks only can be difficult, with the potential risk for inaccurate catheter placement. Repeated corrections can lead to avoidable complications. The use of mixed reality could be a helpful guide and improve the accuracy of drain placement, especially in patients with acute pathology leading to the displacement of anatomical structures. Using a human cadaveric model in this feasibility study, the authors aimed to evaluate the accuracy of EVD placement by comparing two techniques: mixed reality and freehand placement. METHODS: Twenty medical students performed the EVD placement procedure with a Cushing’s ventricular cannula on the right and left sides of the ventricular system. The cannula was placed according to landmarks on one side and with the assistance of mixed reality (Microsoft HoloLens 2) on the other side. With mixed reality, a planned trajectory was displayed in the field of view that guides the placement of the cannula. Subsequently, the actual position of the cannula was assessed with the help of a CT scan with a 1-mm slice thickness. The bony structure as well as the left and right cannula positions were registered to the CT scan with the planned target point before the placement procedure. CloudCompare software was applied for registration and evaluation of accuracy. RESULTS: EVD placement using mixed reality was easily performed by all medical students. The predefined target point (inside the lateral ventricle) was reached with both techniques. However, the scattering radius of the target point reached through the use of mixed reality (12 mm) was reduced by more than 54% compared with the puncture without mixed reality (26 mm), which represents a doubling of the puncture accuracy. CONCLUSIONS: This feasibility study specifically showed that the integration and use of mixed reality helps to achieve more than double the accuracy in the placement of ventricular catheters. Because of the easy availability of these new tools and their intuitive handling, we see great potential for mixed reality to improve accuracy.

OBJECTIVE: Current application of mixed reality as a navigation aid in the field of spinal navigation points to the potential of this technology in spine surgery. Crucial factors for acceptance include intuitive workflow, system stability, reliability, and accuracy of the method. The authors therefore aimed to investigate the accuracy of the system in visualization of anatomical structures using mixed reality in the example of pedicles of the thoracic spine in a human cadaveric study. Potential difficulties and limitations are discussed. METHODS: CT scans of a human cadaveric spinal column specimen were performed. After segmentation and import into the advanced HoloLens 2 software, the vertebrae were exposed. The vertebral arches were preserved on one side for a landmark-based surface registration, whereas pedicles were exposed on the other side in order to measure and evaluate deviation of the overlay holographs with regard to the exact anatomical structure. Accuracy was measured and statistically evaluated. RESULTS: In this work it was demonstrated that the overlay of the virtual 3D model pedicles with the real anatomical structures with anatomical landmark registration was within an acceptable surgical accuracy with the mean value of 2.1 mm (maximum 3.8 mm, minimum 1.2 mm). The highest accuracy was registered at the medial and lateral pedicle wall, and the measurement results were best in the region of the middle thoracic spine. CONCLUSIONS: The accuracy analysis for mixed reality (i.e., between the virtual and real anatomical situation of the thoracic spine) showed a very good agreement when focus was on the pedicles. This work is thus a rare proof of the precision of segmentation to the potential surgical area. The results encourage researchers to open up mixed reality technology in its development and application for spinal navigation.

Dislocation following total hip arthroplasty has to date not been resolved satisfactorily. Previous work has shown that using a less-invasive adaption of Bauer’s lateral transgluteal approach with capsular repair significantly reduces dislocation rates in primary total hip arthroplasty. The aim of this retrospective cohort study was to assess whether this approach also helps to reduce the dislocation rate in revision total hip arthroplasty. We analyzed revision total hip arthroplasty cases performed between 10/2005 and 12/2013 in our department, classifying capsular repair cases as study group and capsular resection cases as control group. The WOMAC score, the dislocations and the revisions were observed. A total of 259 cases were included, 100 in the study group and 159 in the control group. In the 12-month follow-up, dislocation rates were significantly lower in the study group (3%, n = 3) compared to the control group (21.4%, n = 34; p = 0.001). Overall follow-up periods were 49 and 79 months, revision frequencies were 10 and 29%, pain improvements were 5.5 compared to 4.4 and the WOMAC global scores averaged 2.0 ± 2.1 and 2.9 ± 2.6 for the study group and the control group, respectively. The modified, less-invasive, lateral transgluteal approach with capsular repair was accompanied by an 86% reduction in dislocation rates when compared to the conventional technique with capsular resection via the anterolateral Watson-Jones-approach. Capsular repair is possible in about 60% of the revision total hip arthroplasty cases, may be considered as beneficial to avoid dislocation and can therefore be recommended.

Introduction. The main purpose of this study is to develop an efficient technique for generating FE models of pelvic ring fractures that is capable of predicting possible failure regions of osteosynthesis with acceptable accuracy. Methods. Patient-specific FE models of two patients with osteoporotic pelvic fractures were generated. A validated FE model of an uninjured pelvis from our previous study was used as a master model. Then, fracture morphologies and implant positions defined by a trauma surgeon in the preoperative CT were manually introduced as 3D splines to the master model. Four loading cases were used as boundary conditions. Regions of high stresses in the models were compared with actual locations of implant breakages and loosening identified from follow-up X-rays. Results. Model predictions and the actual clinical outcomes matched well. For Patient A, zones of increased tension and maximum stress coincided well with the actual locations of implant loosening. For Patient B, the model predicted accurately the loosening of the implant in the anterior region. Conclusion. Since a significant reduction in time and labour was achieved in our mesh generation technique, it can be considered as a viable option to be implemented as a part of the clinical routine to aid presurgical planning and postsurgical management of pelvic ring fracture patients.

Medial sphenoid wing meningiomas (MSWM) are surgically challenging skull base tumors. Irregular tumor shapes are thought to be linked to histopathology. The present study aims to investigate the impact of tumor shape on postoperative functioning, progression-free survival, and neuropathology. This monocentric study included 74 patients who underwent surgery for primary sporadic MSWM (WHO grades 1 and 2) between 2010 and 2021. Furthermore, a systematic review of the literature regarding meningioma shape and the MIB-1 index was performed. Irregular MSWM shapes were identified in 31 patients (41.9%). Multivariable analysis revealed that irregular shape was associated with postoperative cranial nerve deficits (OR: 5.75, 95% CI: 1.15–28.63, p = 0.033). In multivariable Cox regression analysis, irregular MSWM shape was independently associated with tumor progression (HR:8.0, 95% CI: 1.04–62.10, p = 0.046). Multivariable regression analysis showed that irregular shape is independently associated with an increased MIB-1 index (OR: 7.59, 95% CI: 2.04–28.25, p = 0.003). A systematic review of the literature and pooled data analysis, including the present study, showed that irregularly shaped meningiomas had an increase of 1.98 (95% CI: 1.38–2.59, p < 0.001) in the MIB-1 index. Irregular MSWM shape is independently associated with an increased risk of postoperative cranial nerve deficits and a shortened time to tumor progression. Irregular MSWM shapes might be caused by highly proliferative tumors.