Man-Machine Interfaces in Computer Assisted Surgery

The clinical potential of computer assisted surgery (W) has been more and more widely acknowledged since CAS systems have been introduced into the operating room (OR) theater.

Especially the improvements in safety and accuracy are remarkable and strengthen the ties between surgeons and engineers. Tumor stereotaxis was introduced to neurological surgery in the early 1980s, and currently systems with and without robotic navigation are in use for specific medical indications. Recently, solutions for computer assisted orthopedic surgery were developed and applied to various anatomical regions. However, with the establishment of CAS in vivo, a new complex of problems, which was not present in the laboratory setup, was introduced: the man-machine interface.

Currently, the complexity of available CAS systems requires the presence of at least one system engineer (often called the “operator”) in the OR. As a consequence, there is no possibility for direct communication between the surgeon and the machine or software.

Most of the program steps involved in CAS and choices to be made intraoperatively have to be transferred to the software by means of communication of the surgeon with the operator. Particularly, the establishment of a relation between the virtual object (i.e., a medical image) and the surgical object (i.e., the patient), often denoted as “matching” or “skeletal registration” requires intensive interaction of the surgeon with the computer. A literature survey revealed that no CAS system in clinical use exists without a system engineer or a comparable person, and our clinical experience indicated that the matching process is a weak point in most systems. Because it appears to be contradictory to cost-reduction efforts in health care to have a highly paid specialist in the OR, this research evaluates strategies to facilitate the man-machine interface with the final goal of establishing a direct control of the system by the surgeon or the medical personnel traditionally present at surgery. Options to be investigated include 1) a CAS control panel (virtual keyboard) as an integrated component of the existing navigation system and 2) introduction of a commercial voice-recognition system. The implementation of these strategies into the existing CAS setup at the Department of Orthopaedic Surgery at the Inselspital (University of Bern) and clinical experience gained are reported     

CARD15 in inflammatory bowel disease and Crohn''s disease phenotypes: An association study and pooled analysis

BACKGROUND: Three major polymorphisms of the Caspase-Activation Recruitment Domain containing protein 15 gene have been described to be associated with Crohn's disease. Genotype-phenotype studies reported in literature provide conflicting data on disease localisation and behaviour. We investigated the relation of Caspase-Activation Recruitment Domain containing protein 15 with inflammatory bowel disease and Crohn's disease phenotypic characteristics in a large Dutch cohort and performed a pooled analysis on inflammatory bowel disease patients and Crohn's disease phenotypic characteristics reported in association studies. METHODS: We genotyped 781 cases and 315 controls for the R702W, G908R and 1007fsinsC variants and for six microsatellite markers in and close to Caspase-Activation Recruitment Domain containing protein 15. In the pooled analysis data of 7201 inflammatory bowel disease patients and 3720 controls from 20 studies were included. RESULTS: Association was found for Crohn's disease with R702W and 1007fsinsC, including several disease characteristics, and not for ulcerative colitis. In the pooled analysis all three common Caspase-Activation Recruitment Domain containing protein 15 variants showed strong association with Crohn's disease (p<0.00001; odds ratio varying from 3.0 for single heterozygotes to 14.7 for compound heterozygotes) and not with ulcerative colitis. Phenotype analysis showed association with small bowel involvement, stricturing and penetrating disease. CONCLUSION: Caspase-Activation Recruitment Domain containing protein 15 is associated with Crohn's disease and not with ulcerative colitis. All three common Crohn's disease-associated variants are associated with small bowel involvement, the G908R and 1007fsinsC alleles also being associated with a complicated disease course.     

Degradable injectable bone cement in maxillofacial surgery: indications and clinical experience in 27 patients.

BACKGROUND: A carbonated apatite cement (NORIAN SRS) was used as a bone mineral substitute for the calvaria or viscerocranium in 27 patients. It has the consistency of a paste and hardens at physiologic pH and body temperature due to dahllite crystallization, which has the stoichiometric formula Ca(8.8)(HPO(4))(0.7)(PO(4))(4.5)(CO(3))(0.7)(OH)(1.3). MATERIAL AND METHODS: The cement was used for posttraumatic bone defects in the orbital, periorbital or malar regions (nine patients), posttraumatic deformities of the frontal bone (six patients), tumour-dependent bony defects of the calvaria (two patients) and posttraumatic or cystic defects of the mandible (five patients). In another five patients, the material was used to augment the atrophic anterior mandible in combination with the insertion of dental implants. Follow-up varied between 6 and 40 months (mean: 29 months). RESULTS: There was no inflammatory reaction surrounding the implanted material. There was no sign of infection in any of the patients and only one case of partial wound dehiscence with superficially exposed material. The defect fillings and augmentations were successful in all patients. None of the 19 dental implants which were inserted in combination with the material showed any sign of infection or loosening. Also, there was no loosening of the implants after loading (mean follow-up: 15 months). From the check-up radiographs, the material could be seen as a dense, radio-opaque structure. There were no material fractures or dislocations. Radiologically, the material seemed to be completely replaced by bony tissue after 30 months. CONCLUSION: Our 5-year clinical experience suggests that the material is a suitable bone mineral substitute for cranio-maxillofacial surgery especially for moderate-sized defects of the calvaria and forehead bone. It has advantages over preformed, solid bone substitute materials, and, due to its initial plasticity and eventual great compressive strength, it can also stabilize dental endosseous implants in the atrophic mandible.     

Computer-assisted LISS plate osteosynthesis of proximal tibia fractures: feasibility study and first clinical results.

Fluoroscopy is the most common tool for the intraoperative control of long-bone fracture reduction. Limitations of this technology include high radiation exposure for the patient and the surgical team, limited visual field, distorted images, and cumbersome verification of image updating. Fluoroscopy-based navigation systems partially address these limitations by allowing fluoroscopic images to be used for real-time surgical localization and instrument tracking. Existing fluoroscopy-based navigation systems are still limited as far as the virtual representation of true surgical reality is concerned. This article, for the first time, presents a reality-enhanced virtual fluoroscopy with radiation-free updates of in situ surgical fluoroscopic images to control metaphyseal fracture reduction. A virtual fluoroscopy is created using the projection properties of the fluoroscope; it allows the display of detailed three-dimensional (3D) geometric models of surgical tools and implants superimposed on the X-ray images. Starting from multiple registered fluoroscopy images, a virtual 3D cylinder model for each principal bone fragment is constructed. This spatial cylinder model not only supplies a 3D image of the fracture, but also allows effective fragment projection recovery from the fluoroscopic images and enables radiation-free updates of in situ surgical fluoroscopic images by non-linear interpolation and warping algorithms. Initial clinical experience was gained during four tibia fracture fixations that were treated by LISS (Less Invasive Stabilization System) osteosynthesis. In the cases operated on, after primary image acquisition, the image intensifier was replaced by the virtual reality system. In all cases, the procedure including fracture reduction and LISS osteosynthesis was performed entirely in virtual reality. A significant disadvantage was the unfamiliar operation of this prototype software and the need for an additional operator for the navigation system.     

Superficial femoral artery recanalization with self-expanding nitinol stents: long-term follow-up results.

PURPOSE: Since long-term patency and device integrity of nitinol stents in SFA lesions are not well studied, we examined clinical outcome, patency and device integrity after stenting long lesions using a standardized implantation technique. METHODS: Between 2001 and 2006, 59 patients (74 lesions) were treated with the same nitinol self-expandable stent (Zilver, Cook, USA) and technique for SFA recanalization. Clinical charts and imaging were retrospectively reviewed for patency (primary and assisted-primary), and device integrity. RESULTS: Patients were 74.5 (10.9) years old (range 49 to 93), 64% male, 42% diabetic, 62% hypertensive and 67% current or former smokers. Lesions were 23% TASC B, 16% TASC C, or 61% TASC D. Mean recanalization length was 19 cm (range 3 to 53). Mean number of stents per patient was 2.8 (total 210). Mean follow-up time was 2.4 years (range 3 days to 4.8 years). Kaplan-Meier estimates for primary patency rates were 90%, 78%, 74%, 69%, and 69% at 1, 2, 3, 4 and 4.8 years, respectively. Ten restenoses at a mean of 500 (388) days (1-1251 days) were successfully recanalized. The assisted primary patency rates were 96%, 90%, 90%, 90% and 90% at 1, 2, 3, 4 and 5 years, respectively. Six complete occlusions could not be reverted by a second recanalization procedure, and were treated by surgical bypass (1 case), amputation (3 cases), or medical management (2 cases). One (1.04%) Class II stent fracture was noted. CONCLUSIONS: SFA recanalization with a standardized implantation technique and nitinol stents provides good long-term primary and assisted-primary patency.     

Criteria for evaluating the clinical and practical utility of models used by nurses

Arguably, nursing, like all health care disciplines, is an applied science. Essentially, this refers to the application of theory in order to understand and respond to the health problems of clients. These theories may be drawn (borrowed) from any applied science, or generated inductively from clinical nursing practice. Alternatively, nurses may attempt to apply deductive theory (global theoretical frameworks) known as nursing models. In this paper, all theoretical approaches, irrespective of origin, are referred to as models used by nurses. Thirteen criteria by which clinicians, and others, can evaluate the clinical and practical utility of models used by nurses which are expressed in the form of questions are identified and discussed. The criteria are an extension, both in detail and in number, of those developed by Reynolds and Cormack and subsequently applied by those writers to the Johnson Behavioural System Model of Nursing. The value, or otherwise, of individual models, or of models in general, will not be discussed in this paper. However, the authors propose that if the evaluation criteria described here are applied to existing models, serious deficits will be identified in relation to their clinical and practical utility.     

Quadriceps tendon and patellar ligament: Cryosectional anatomy and structural properties in young adults

Structural tensile properties analyses of 10-mm-wide central sections of quadriceps tendon-bone (QT-B) and bone-patellar ligament (B-PL) complexes from young male donors (mean age 24.9 years, range 19–32 years) were complemented by a cryosectional analysis: each QT-B complex was composed of the segment of the quadriceps tendon with the proximal half of the patella attached, each B-PL complex was composed of the distal half of the patella with the patellar ligament attached. A servohydraulic materials testing machine was used to assess ultimate failure load of 16 unconditioned and 16 preconditioned QT-B and B-PL complexes at an extension rate of 1 mm/s. Ligaments/tendons were preconditioned during 200 cycles from 50 to 800 N at 0.5 Hz. On cryosections the quadriceps tendons were significantly longer and thicker and exhibited a significantly larger bony attachment area than the patellar ligaments. Cross-sectional areas of 10-mm-wide, full-thickness, central parts of unconditioned quadriceps tendons were significantly greater and measured 64.6±8.4 mm² with respect to the cross-sectional area of patellar ligament, measuring 36.8±5.7 mm² (P<0.0025). Ultimate failure loads for unconditioned complexes resulted at 2173±618 N for QT-B complexes and at 1953±325 N for B-PL complexes (P=0.43). Ultimate failure load values measured 2353±495 N for preconditioned QT-B complexes and 2376±152 N for preconditioned B-PL complexes, respectively (P=0.77). Despite the fact that initial testing length, area of unconditioned QT-B and B-PL complexes were significantly different, displacement at ultimate load, energy to failure and total energy were not. In terms of ultimate tensile strength, the 10-mm-wide central part of the QT-B complex compared favourably to the tensile properties of the human femur-anterior cruciate ligament-tibia complex from a comparable young age group. The evidence from anatomic, cryosectional and structural properties analyses suggests that the QT-B complex may be a valuable and versatile adjunct to the surgeon's armamentarium in reconstructive cruciate ligament surgery.     

Localization of SNARE proteins and secretory organelle proteins in astrocytes in vitro and in situ

Astrocytes are capable of regulated release of messenger molecules. Astrocytes cultured from new born rodent brain express a variety of classical presynaptic proteins. We investigated the question whether the capability to express synaptic proteins in culture was a feature only of immature astrocytes, and whether these proteins were also expressed by astrocytes in situ. Experiments were performed with transgenic mice expressing the enhanced green fluorescent protein under the control of the human glial fibrillary acidic protein promoter. Using double fluorescence and astrocytes cultured from 1 to 16 day-old animals we show that the astrocytic expression of synaptic proteins in culture is invariant of the age of donor animals. Culturing can induce the astrocytic expression of specific synaptic proteins such as SV2, synaptophysin and SNAP-25. Astrocytes in brain sections of 1-16 day-old animals revealed a punctuate immunofluorescence for secretory carrier membrane protein (SCAMP), SNAP-23, synaptobrevin II, and cellubrevin, to a minor extent for SNAP-25 and synaptophysin, and none for SV2. Our results demonstrate that cultured astrocytes express synaptic proteins not present in situ. Nevertheless, astrocytic organelles in situ are equipped with molecules that could be involved in regulated exocytosis of messenger substances.     

Vancomycin-resistant Aureobacterium species cellulitis and bacteremia in a patient with acute myelogenous leukemia.

A 39-year-old male with acute myelogenous leukemia and concomitant porphyria cutanea tarda was admitted to the hospital for consolidation chemotherapy of his leukemia. During his hospitalization, he developed cellulitis of the left hand and persistent bacteremia with a yellow-pigmented, nonfermenting coryneform bacterium that was identified as Aureobacterium sp. The portal of entry for the Aureobacterium infection was probably through the skin lesions due to porphyria cutanea tarda. The infection developed while the patient was receiving vancomycin prophylaxis, and the vancomycin MIC for the isolate was 32 micrograms/ml.