Extraction of canine gait characteristics using a mobile gait analysis system based on inertial measurement units.

This study aims to investigate two simple algorithms for extracting gait features from an inertial measurement unit (IMU) based canine gait analysis system. The first algorithm was developed to determine the hip/shoulder extension/flexion range of motion. The second algorithm automatically determines the stance and swing phase per leg. To investigate the accuracy of the algorithms, two dogs were walked on a treadmill and measured simultaneously with an IMU system, an optical tracking system and two cameras. The range of motion estimation was compared to the optical tracking systems, with a total of 280 steps recorded. To test the stance and swing phase detection, a total of 63 steps were manually annotated in the video recordings and compared with the output of the algorithm. The IMU's-based estimation of the range of motion showed an average deviation of 1.4° to 5.6° from the optical reference, while the average deviation in the detection of the beginning and end of the stance and swing phases ranged from -0.01 to 0.09 s. This study shows that even simple algorithms can extract relevant information from inertial measurements that are comparable to results from more complex approaches. However, additional studies including a wider subject pool need to be conducted to investigate the significance of the presented findings.

Missing facial parts computed by a morphable model and transferred directly to a polyamide laser-sintered prosthesis: an innovation study.

Mirroring of missing facial parts and rapid prototyping of templates have become widely used in the manufacture of prostheses. However, mirroring is not applicable for central facial defects, and the manufacture of a template still requires labour-intensive transformation into the final facial prosthesis. We have explored innovative techniques to meet these remaining challenges. We used a morphable model of a face for the reconstruction of missing facial parts that did not have mirror images, and skin-coloured polyamide laser sintering for direct manufacture of the prosthesis. From the knowledge gleaned from a data set of 200 coloured, three-dimensional scans, we generated a missing nose that was statistically compatible with the remaining parts of the patient's face. The planned prosthesis was manufactured directly from biocompatible skin-coloured polyamide powder by selective laser sintering, and the prosthesis planning system produced a normal-looking reconstruction. The polyamide will need adjustable colouring, and we must be able to combine it with a self-curing resin to fulfil the requirements of realistic permanent use.

Facial acquisition by dynamic optical tracked laser imaging: a new approach.

Three-dimensional capture of the surface of soft tissue is a desirable support for documentation and therapy planning in plastic and reconstructive surgery concerning the complex anatomy of the face, particularly cleft lip and palate (CLP). Different scanning systems are used for capturing facial surfaces. These systems are mostly based on a static linear measuring arrangement. Established systems work on the basis of coded white light or linear laser triangulation and digital stereophotogrammetric approaches. Shadowing effects occur with these devices. These effects may be avoided by a radical new approach first used in automotive industries that employs a mobile, flexible handheld laser scanner with simultaneous registration by optical tracking. The aim of this study was to assess the suitability of this scanner for surgical procedures on the human face in operating theatre. Five babies aged about 3 months with cleft deformities (one CLP, one bilateral CLP, three isolated cleft lips) were captured directly: twice preoperatively, twice postoperatively and twice after 7 days. An industrial standard specimen and two plaster cast masks of CLP babies were taken and subsequently measured to assess reliability and validity of the device. Masks were measured to reflect the complex surface of the cleft deformity. Data evaluation was done with respect to completeness of the data sets, as well as reliability and validity of the system. Missing data caused by shadowing could be avoided in all images. Even complex areas with undercuts could be reproduced completely and precisely with an accuracy in the sub-millimetre range.

Computer-assisted single- or double-cut oblique osteotomies for the correction of lower limb deformities.

Corrective osteotomy interventions on lower extremities are widely accepted procedures for restoring axial alignment of lower limbs. However, some studies reveal failure rates of up to 70 per cent in a 10 year time frame, which indicates that the success of corrective osteotomies depends on multiple factors. Based on a comprehensive review of error sources among conventional correction osteotomy interventions, a novel approach was developed in order to reduce these error sources among all clinical working steps (deformity determination, planning, and intra-operative realization). The article describes the implemented methodology for realizing optimal correction osteotomies based on a six-dimensional or 12-dimensional optimization module for single- and double-cut oblique osteotomies. The results show that the realized planning and navigation concept enables reduction in the error sources among the clinical working steps of correction osteotomy interventions.

[Minimally-invasive computer-assisted fluoroscopic navigation for kyphoplasty]. / Minimal-invasive Computer-assistierte fluoroskopische Navigation der Kyphoplastie.

AIM: The transpedicular placement of a hollow needle into vertebral bodies for kyphoplasty requires utmost accuracy and thereby permanent multiplanar X-ray control. Facing the increasing number of vertebral compression fractures, the aim of this work was the implementation of computer-assistance to optimise the issue. Prior to clinical implementation, experimental trials were undertaken to analyse the quality-improving options of the technique. METHOD: The virtual image of the planning and the puncture were correlated with the postoperative X-ray image of the needle. The real canal in the bone was then correlated with the preoperative planning in a CT-based 3D model and differences were calculated. As a measure of accuracy the deviation of the needle from the ideal intruding vector and the distance between its top and the centre of a predefined target were scrutinised and related to the indications of the navigation system. Operating time, radiation exposure and general applicability were additionally assessed. All data were compared with those of a conventional control group. RESULTS: Planning and navigation could be executed with high accuracy. With an exactly transpedicular approach, neural structures were safely circumnavigated without once missing the target. In the control group the distance fault was up to 9 mm. The navigated drilling differed from the ideal trajectory by 1 degrees to max. 4 degrees. Conventional C-arm control led to a divergence of 4 degrees to 8 degrees . Radiation exposure could be reduced through computer assistance by 76 % to a fourth of the conventionally resulting amount and the pure operating time thereby decreased by 40 %. The inconvenient course of repeated positioning of the C-arm was overcome. CONCLUSION: In challenging cases of deteriorated anatomy and difficult radiomorphologic orientation, especially of the lower thoracic spine, the CAOS-procedure succeeds in finding the optimal pedicular approach to the vertebral body, helps to avoid collateral damage and minimises the overall risk of the procedure. High accuracy and reduced radiation exposure justify the clinical use of fluoroscopic navigation for transpedicular instrumentation.

[Accuracy of fluoroscopically navigated drilling procedures at the hip]. / Präzisionsanalyse fluoroskopisch navigierter Zielbohrungen am Hüftkopf.

AIM: Many orthopaedic procedures require an accurate drilling in bone. The outcome is frequently dependent on the geometric accuracy of this surgical step. The precision of such a procedure can be improved with the help of fluoroscopic navigation. Reliability, accuracy and benefit of this new method for the patient, as well as for the surgical staff, need to be analysed. METHOD: In a standardised in vitro trial, the drilling of a 5 mm spherical lesion implanted in an artificial femoral head was performed using a navigated drill-guide and a navigated drill. In groups A and B, the distance of the tip of the drill to the center of the lesion was analysed in a 3D CT-generated model and in macroscopic cross section. Additionally, in group B the actual direction of the drill canal was measured. RESULTS: The mean distance in group A was measured to be 1 mm, with all results ranging between 0 and 2.5 mm. In group B the planned direction of the canal was reproduced with a deviation of 0 degrees to 7 degrees, the target only being missed by a mean distance of 2.5 mm and a maximum of 3.5 mm. Compared to the macroscopic and 3D-CT findings, the correlation of the data calculated by the navigation system was accurate up to a difference of 4 degrees or 2 mm. CONCLUSION: The fluoroscopically assisted freehand navigation used during the drilling of bone led to a high accuracy of three-dimensional tip placement while reducing radiation exposure to a minimum. It represents a promising and efficient application for a variety of procedures in orthopaedic surgery.

Computer-assisted orthopedic surgery with individual templates and comparison to conventional operation method.

STUDY DESIGN: Comparison was made of the accuracy of a pedicle bore performed by conventional technique and by using an individual template in the lumbar spine of cadavers. OBJECTIVES: The fixation of pedicle screws necessitates a high amount of surgical skill and experience to avoid lesions of nerves and vessels. By using individual templates in a cadaver study the goal was to prove the accuracy and efficiency of this less-invasive image-guided surgery in comparison with the conventional technique by fluoroscopy and computed tomographic (CT) scan. SUMMARY OF BACKGROUND DATA: Based on three-dimensional models generated from CT scans of the lumbar spine, precise preoperative planning of the position and trajectory of pedicle screws is possible. In comparison with other means of computer-assisted spine surgery with navigation systems, in which a time-consuming intraoperative matching of the bone surface structure is necessary, the use of individual templates enables the surgeon to reduce the operation time considerably. METHODS: Individual templates are customized on the basis of three-dimensional reconstructions of the bone structures extracted from CT image data and depending on the individual preoperative surgical planning, which uses the desktop image processing system for orthopedic surgery (DISOS). A desktop-computer-controlled milling device is used as a three-dimensional printer to automatically mold the shape of small reference areas of the bone surface into the body of the template. Postoperative CT scans were obtained and the accuracy of the pedicle bore rated by two independent observers. RESULTS: The preparation time with the individual template lasted slightly longer than with the conventional operation technique (555 seconds and 482 seconds, respectively). Fluoroscopic study took a mean time of 31.5 seconds, with the conventional operation technique and 5.5 seconds with the individual template. The assessment of the postoperative CT scans demonstrated a higher accuracy of the pedicle bore with the individual template. CONCLUSIONS: This cadaveric study has shown that overall operation time including the fluoroscopy time can be shortened by using the individual template for the pedicle bore. The individual template is an alternative to the computer-assisted navigation systems with a good cost-performance ratio without excessive technical workload on the physicians or the surgical personnel. Further investigations must be conducted to validate the clinical applicability of this system.

[Planning and performance of orthopedic surgery with the help of individual templates]. / Planung und Ausführung von orthopädischen Operationen mit Hilfe von Individualschablonen.

Operational interventions can be planned and simulated accurately with the help of a three-dimensional reconstruction of the anatomical bone structures, created from the tomographic data of a patient. Computer-assisted navigation systems or robotic systems can assist the intraoperative realization of the planned intervention and may support the spatial orientation within the operational field. As an inexpensive alternative without the high excessive technical workload on the physicians or the surgical personnel, individual templates were developed in the Helmholtz Institute Aachen. In this approach the negative three-dimensional bone surface, known exactly from the 3D-reconstruction of the patient's bone by the planning system DISOS, is milled into a small cubic block of polycarbonate. During the intervention, the template serves as a reference for the spatial orientation and as a tool-guide for cutting or milling of the bone according to the previous planning. Clinical and experimental studies have shown that operation times as well as intraoperative X-ray times can be shortened by the use of individual templates, while preserving the task sequence of the conventional operation procedures.