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Biomedical subjects

P Messmer

Publications and source records attributed to P Messmer.

At least 19 recordsLinked to original sources

A less invasive anterior intrapelvic approach for the treatment of acetabular fractures and pelvic ring injuries.

BACKGROUND: The ilioinguinal approach by Letournel has fundamentally contributed to the successful treatment of acetabular fractures. Since most of the present complications arise from soft tissue structures in the inguinal part, it would be desirable to avoid the surgical dissection of this region. We have therefore developed a less invasive anterior intrapelvic approach consisting of a suprapubic access combined with the lateral window of the ilioinguinal approach. METHODS: Between January 2000 and October 2002, 14 patients with acetabular fractures and 6 patients with pelvic ring injuries were consecutively operated using our technique. The patients were prospectively followed up clinically and by standard X-rays for 1 year. RESULTS: In 19 patients the technique was successful and only one patient was converted to an ilioinguinal approach due to difficulties in reducing the fracture. Our access allowed good visibility but reduction manoeuvres were sometimes difficult and the development of a new reduction forceps became necessary. Anatomical and satisfactory reduction was achieved in 13 acetabular fractures and 4 pelvic ring injuries. One cutaneous femoris neurapraxy and one superficial infection occurred related to the approach and both resolved with conservative treatment. Clinical outcome at one year was good to excellent in 17 patients (modified Merle d'Aubigné/Postel score). In 3 patients the result was fair to poor for reasons unrelated to the approach. CONCLUSIONS: Our approach permits visualisation of the entire anterior column and pelvic ring without the necessity to dissect the inguinal neurovascular structures. Our preliminary results demonstrate that safe reduction and stable fixation of selected acetabular- and pelvic ring fractures are possible.

Acetabulum↗

[Interdisciplinary emergency room management of trauma patients from the standpoint of coworkers].

INTRODUCTION: The purpose of this study was to examine whether staff questionnaire evaluation is useful for quality control in the emergency room (ER) setting. METHODS: Consecutive anonymous questionnaires (Likert scale 1-5) were filled out by the involved medical staff in all ER trauma cases in a university hospital from July 2002 to December 2003 (analysis of variance, P<0.05). RESULTS: In 171 ER cases, 844 staff members responded. Main criticisms concerned time management or satisfaction with personal ER training (Likert <4). Consultants rated the quality of their training significantly higher than younger doctors, two thirds of consultants vs one third of residents having passed an Advanced Trauma and Life Support course (P<0.001). Depending on responders' professional specialties and whether the situation concerned multiple trauma (Injury Severity Score >15), a significant systematic difference resulted. CONCLUSION: Our standardized staff questionnaire evaluation was revealed to be a discriminative instrument for quality management of trauma cases in the ER. To confirm these findings, correlation with clinical outcome data and further validation of the method are needed.

Attitude of Health Personnel↗

Multiple-trauma management: standardized evaluation of the subjective experience of involved team members.

BACKGROUND AND OBJECTIVE: Staff attitude plays a pivotal role in quality management. The objective of the present study was to further define how interdisciplinary emergency hospital staff experience their daily work and the extent to which the professional speciality and training of an individual influences his/her assessment of multiple-trauma team performance. METHODS: The clinical staff involved in multiple-trauma emergency management of a university hospital was asked to answer a confidential questionnaire. Factorial analysis was used to identify 8 major dimensions from a total of 53 items. RESULTS: The questionnaire was returned by 128 team members. All professional groups were most dissatisfied with the dimensions 'education and training', 'work sequence between specialities' and 'communication between specialities'. Assessment of the quality of in-hospital emergency-trauma management differed significantly between professional specialities (ANOVA, F=5.2; P=0.028); surgeons gave the highest ratings for all but one dimension. Having taken an Advanced Trauma Life Support (ATLS) course influenced significantly the total rating of multiple-trauma treatments of anaesthetists and surgeons (F=5.5; P=0.024). CONCLUSIONS: The perceptions of interdisciplinary trauma team members without the completion of an ATLS training course were that they did not communicate enough with each other and that there were differences between their expectations and reality. The differences and the communication deficits were overcome in team members who had passed an ATLS course.

Anesthesia↗

Synchrotron diffraction study of deformation mechanisms in mineralized tendon.

The high stiffness and toughness of biomineralized tissues are related to the material deformation mechanisms at different levels of organization, from trabeculae and osteons at the micrometer level to the mineralized collagen fibrils at the nanometer length scale. Quantitatively little is known about the sub-micrometer deformation mechanisms under applied load. Using a parallel-fibred mineralized tissue from the turkey leg tendon as a model for the mineralized collagen fibrils, we used in situ tensile testing with synchrotron x-ray diffraction to measure the average fibril deformation with applied external strain. Diffraction peak splitting occurred at large strains, implying an inhomogeneous elongation of collagen fibrils. Scanning electron microscopy measurements lead us to conclude that the inhomogeneous mineralization in mineralized tendon is at the origin of the high fracture strain.

Animals↗

Computer aided designed neo-clavicle out of osteotomized free fibula: case report.

Total clavicle reconstruction is a challenging task. We performed a reconstruction of the ventral shoulder girdle by calculating a 3D DICOM representation of the left clavicle to create a right neo-clavicle. Two cuts in correct position and angle leads to a natural 3D shape of the new clavicle. The data were used with a thermo-jet procedure to form model slices of thermoplastic wax. Subsequently, the double titanium osteotomy template with correct cut-angulation was constructed. A 40-year old patient presented with symptoms of progressive pain and instability in the shoulder girdle resulting from complete right clavicle resection due to desmoid tumour 23 years earlier. During the operative procedure, dissection, guided double osteotomy, microvascular anastomoses and acromioclavicular-sternoclavicular fixation were performed. The computer-assisted planning resulted in the exact calculation of the two osteotomy cuts, hence, the 3D appearance of the neo-clavicle. Two years postoperatively, patient showed slightly improved elevation and complete recovery from pain. Our operative procedure demonstrates that the computer-assisted planning with construction of a wax model and an osteotomy template is a useful approach to plan the two precise cuts leading to a predictable shape of the clavicle.

Adult↗

Effect of cortical thickness and cancellous bone density on the holding strength of internal fixator screws.

Internal fixators are a new class of implants designed to preserve the periosteal blood supply of the bone. In contrast to conventional plate fixation in which the screws have spherical heads and are loaded mainly by axial pullout forces, screws in internal fixators are "locked" within the plate and therefore subjected to axial as well as bending loads. In this study the ultimate loads of screws of a commercially available internal fixator system were tested in a pullout (n = 72) and cantilever bending mode (n = 72) in metaphyseal and diaphyseal regions of four pairs of human tibiae with different bone qualities. Cortical thickness and cancellous bone density were determined at the screw insertion sites. Stepwise multiple linear regression revealed that cortical thickness and cancellous density can explain 93% and 98% of the variance of the ultimate load of the screws in an axial pullout and cantilever bending mode. Screws in internal fixators are better suited to transmit shear forces and thereby make better use of the strength potential of bone than screws used in conventional plate fixation: this is especially advantageous when bone strength is reduced, e.g. due to osteoporosis.

Aged↗

Displaced anterior column acetabular fracture: closed reduction and percutaneous CT-navigated fixation.

The purpose of this study is to demonstrate the feasibility of computer-tomography-navigated closed reduction and percutaneous fixation (CRPF) in a patient with an externally rotated left acetabular fracture. After a follow-up of 18 months the patient was pain-free and had a normal range of motion in both hip joints. Radiologically, the fracture was fully consolidated, remodelled, and there were no signs of osteoarthritis. To our knowledge, CT-navigated CRPF of a rotated acetabular fracture has not been reported before. Further studies regarding the feasibility of the method are warranted.

Acetabulum↗

[Fluoroscopy based surgical navitation vs. mechanical guidance system for percutaneous interventions. A controlled prospective study exemplified by distal locking of intramedullary nails].

The aim of this study was to directly compare mechanically based targetting and surgical navigation when applied for percutaneous osteosynthesis. The distal locking procedure of intramedullary nails was used as the clinical model for a controlled prospective study. A total of 50 patients were included in two groups. In group 1, the distal locking was done with a mechanical aiming device while in group 2 this was done using a fluoroscopy based surgical navigation system. The target parameters were the precision attained, the necessary operation and fluoroscopy times as well as the number and severity of intra-operative problems. The drill-bit failed to pass through the interlocking hole in one patient with mechanical guidance and in two patients with surgical navigation. The average procedure time for distal locking with mechanical guidance was 6.9 minutes compared with 37.6 minutes with surgical navigation. An additional 44 minutes were required before skin incision and after skin closure as setup time for the navigation system. There was no significant difference in the fluoroscopy time or in the number of intra-operative technical problems. Surgical navigation increased the demand for resources but failed to improve the precision of distal locking compared with mechanical guidance. Further clinical studies are required to determine to what degree these results, using a special model, relate to other applications.

Aged↗

Targeted overexpression of vitamin D receptor in osteoblasts increases calcium concentration without affecting structural properties of bone mineral crystals.

Increased cross-sectional area and strength of long bones has been observed in transgenic mice with 2-fold (OSV9) and 3-fold (OSV3) elevation of osteoblast vitamin D receptor (VDR) levels. In the present study, mineralization density distributions, including typical calcium content (Ca(Peak)) and homogeneity of mineralization (Ca(Width)) of femoral bone and growth plate cartilage, were determined by quantitative backscattered electron imaging (qBEI). Fourier-transform infrared (FTIR) microspectroscopy was used to examine mineral content, collagen and crystal maturation, and scanning small angle X-ray scattering (scanning-SAXS) for studying mineral particle thickness and alignment. In addition, X-ray diffraction (XRD) of distal tibiae revealed mineral particle c-axis size. In trabecular bone, the increase in Ca(Peak) was significant for both OSV9 (+ 3.14%, P = 0.03) and OSV3 (+ 3.43%, P = 0.02) versus controls with 23.61 +/- 0.45 S.D. wt% Ca baseline values. In cortical bone, Ca(Peak) was enhanced for the OSV3 mice (+ 1.84%, P = 0.02) versus controls with 26.61 +/- 0.28 S.D. wt% Ca, and OSV9 having intermediate values. Additionally, there was significantly increased homogeneity of mineralization as denoted by a reduction of Ca(Width) (-8.4%, P = 0.01) in primary spongiosa. FTIR microspectroscopy, with the exception of an increased collagen maturity in OSV3 trabecular bone (+ 9.9%, P = 0.02), XRD, and scanning-SAXS indicated no alterations in the nanostructure of transgenic bone. These findings indicate that elevation of osteoblastic vitamin D response led to formation of normal bone with higher calcium content. These material properties, together with indications of decreased bone resorption in secondary spongiosa and increased cortical periosteal bone formation, appear to contribute to the improved mechanical properties of their long bones and suggest an important physiological role of the vitamin D-endocrine system in normal bone mineralization.

Animals↗

Adapting the fluoroscope to image-guided surgery.

Image-guided techniques have been well established in all surgical disciplines for years. To achieve an optimised work flow during image-guided surgery, the surgeon should be able to manipulate the visual feedback and therefore the imaging unit. C-arm fluoroscopy is the imaging modality routinely used for intraoperative imaging in orthopaedic surgery. The C-arm fluoroscope is positioned and handled by a radiographer on vocal commands, which means that the surgeon depends on external help to manipulate the visual feedback and the work flow is not optimised. The MEPUC interface adapts the C-arm fluoroscope to the needs of image-guided orthopaedic procedures. MEPUC is an acronym for Motorised Exact-Positioning Unit for C-arm. In the hardware component of the MEPUC a conventional C-arm fluoroscope is equipped with stepping motors. The software component allows the surgeon to control the motorised movements of the fluoroscope. The MEPUC interface enables the surgeon to position the C-arm fluoroscope independently in the operating room. Further advantages are achievable when the MEPUC interface is combined with surgical navigation, as this combination allows fully automatic reproduction of former projections. Clinical experience with the MEPUC interface suggests that the work flow for intraoperative imaging is improved and personal requirements reduced.

Fluoroscopy↗

[New stabilization techniques for fixation of proximal tibial fractures (LISS/LCP)].

In unstable proximal tibia fractures secondary dislocation due to insufficient buttressing is a well known complication leading to incongruency of the joint and axial deviation of the leg. Double plate osteosynthesis increases stability, however it is not very biological and may be accomplished by wound healing problems. New stabilization techniques such as LISS (Less Invasive Stabilization System) and LCP (Locked Compression Plate) provide angle stability and minimal invasiveness. Therefore stability of fixation is improved and wound-healing problems decrease. Today simple fractures are still fixed with conventional plates and screws, however more complex bicondylar fractures, particularly those with a metaphyseal comminution zone and/or severe soft tissue damage are fixed favorably by the new stabilization techniques.

Adult↗

[Unilateral apophyseal fracture of the superior anterior iliac crest--a case report].

While soccer playing a 19 year old man suffered from acute onset of severe pain in the anterior part of the iliac crest. A CT-scan confirmed the unilateral avulsion of the anterior superior iliac spine. Due to only minimal fragment dislocation and still open apophysis we decided to treat this injury conservatively with crutches and partial weight bearing. There were no complications and already three weeks after the accident the young man was nearly painfree. Avulsion of the anterior superior iliac spine most commonly occur in adolescents. The fracture is often missed and treated as muscle injury or hip pain and therefore received a symptomatical therapy. Later a typical hypertrophic callus formation confirms the avulsion fracture. The avulsion occurs by sudden pull of the sartorius muscle to the anterior superior iliac spine. The pull of the muscle dislocates the loose fragment caudally. In most of the cases a conservative treatment is successful.

Adult↗

[Endoscopically controlled stabilization of humerus shaft fractures. The endoscope as an aid in minimally invasive osteosynthesis].

This study describes the anatomical basis of direct visualization of the radial nerve and of fracture reduction in humeral shaft nailing and reports first clinical results. Fourteen cadavers were random selected and dissected in order to determine the exact course of the radial nerve in relationship to anatomical landmarks. In individuals with a total humeral length between 25-33 cm the radial nerve was found to cross the humeral shaft exactly in the middle of the long axis of the humeral shaft. The average distance from the lateral epicondyle to the point were the radial nerve penetrates the lateral intermuscular septum was 11.9 +/- 1.0 cm, the distance from the posterior tip of the acromion to the crossing of the nerve with the medial border of the humeral shaft was 12.9 +/- 1.5 cm. Using these landmarks in six clinical cases fracture reduction, visualization of the radial nerve and intramedullary nailing could be achieved with endoscopic control. There were no surgical complications such as secondary radial nerve palsy, hematomas or wound healing problems. With the use of the endoscope the number of secondary radial nerve palsies associated with intramedullary humeral shaft nailing might be reduced in the future.

Adult↗

Endoscopic-assisted, minimally invasive anterior pelvic ring stabilization: a new technique and case report.

This report describes the technique of endoscopic-assisted reduction and stabilization of the anterior pelvic ring with endoscopic visualization of all critical bone and soft tissue structures. Compared with the conventional ilioinguinal approach of Letournel, the endoscopic technique facilitates a reliable internal fixation of anterior pelvic ring fractures with minimal soft tissue trauma. Thus, the use of the endoscope enables us to apply the concept of minimal invasive plate osteosynthesis to the pelvis. We recommend the described technique for complex anterior pelvic ring fractures, in which the anterior stabilization has to be achieved with a plate from the symphyseal region to the iliac wing.

Adult↗

Volumetric model determination of the tibia based on 2D radiographs using a 2D/3D database.

We present a new concept with mathematical background for the construction of a three-dimensional (3D) volumetric model of the human tibia based on two conventional orthogonal two-dimensional (2D) radiographic images. This approach is supported by a computer database containing a collection of 80 2D/3D image data sets of individual cadaveric tibiae. For each of these tibiae, the database contains digitized 2D orthogonal radiographic images in both anterior and lateral views, and the corresponding 3D CT data obtained by computerized tomography. To obtain a 3D model of a tibia for a given patient, shape matching is performed. The computer finds the most similar tibia to the patient's tibia among the 2D radiographic images in the database by applying a matching process. To improve accuracy, a 2D image warping procedure can be applied on the slices of the selected bone prior to 3D reconstruction. The warping process is controlled by the contour data of the two orthogonal views. We found that the 3D model thus achieved was useful for virtual preoperative planning and for simulation of the internal fixation of long bones.

Cadaver↗

[Technology integration and process management. Concept and implementation of a new platform for simultaneous diagnosis and therapy of acutely ill and injured patients and for elective computer assisted surgery (CAS)].

Modern imaging and computer technology gain more and more importance in surgery. This is true for elective and emergency diagnosis and treatment. However integration of technology and optimization of process management is severely behind. A new diagnostic-therapeutic platform should balance this deficit. The platform is composed of a fully equipped operation room environment with integrated high end computer-tomography with navigation, a digital subtraction angiography and an OR- and imaging-table particularly developed for this set-up. The platform may be used for elective diagnosis, for diagnosis and therapy in polytraumatized patients in one and the same location (one stop shop) and for computer assisted surgery (CAS). Bringing the technology to the patient and not the patient to the technology can save time consuming and potentially dangerous transports and expensive personnel can be reduced. Navigation-technology and high quality intra-operative imaging expand the spectrum of minimally invasive surgery.

Diagnostic Imaging↗

[Computer-assisted surgery: developments and prospects in 2001. Results of a workshop at Schloss Reisenburg, 23-24 November 2000].

The progress in computer assisted surgery (CAS) is influenced by new technologies in imaging as well as by the input of the users. At present, CAS procedures are established in dorsal spine instrumentation, prosthetics and long bone surgery. Present status and future of CAS was a topic of an expert meeting at the Reisensburg castle. Imaging will speed up in the future using multi-detector techniques. C-arm navigation will gain more information using the 3D technology intraoperatively. CT based navigation procedures are standard in spine and will be established in pelvic surgery. CAS in robotics at the moment means the use of robot-assistance. A new concept is the modality-based navigated surgery, which can be used at various skeletal locations. Visualization of patient data will improve using 3D semi-transparencies with real time update. In the future it will be mandatory to find algorithms to fuse the different possibilities and techniques. A new concept of surgical training is necessary to teach CAS procedures. Therefore discussion must go on to improve these systems.

Arthroplasty, Replacement, Knee↗

[Radiation exposure of the patient by intraoperative imaging of intramedullary osteosyntheses].

MATERIAL AND METHOD: 39 patients with pertrochanteric femur fracture (n = 32) or lower leg fracture (n = 7) were treated with closed intramedullary nailing. The related radiation exposure of the patients was calculated. RESULTS: Osteosynthesis of pertrochanteric fractures took less fluoroscopic time than osteosynthesis of lower leg fractures. The effective dose was 14 mSv for nailing osteosynthesis of proximal pertrochanteric fractures and less than 0.1 mSv for osteosynthesis of distal lower leg fractures. CONCLUSION: Radiation exposure of the patient due to intraoperative fluoroscopic imaging during osteosynthesis can be estimated based on the data given above. Intraoperative observations imply, consequent application of radiation protection by the orthopaedic surgeons may reduce intraoperative radiation exposure even more.

Female↗