Ortsständige Rekonstruktionstechniken und Palliativoperationen bei großen Rupturen und sogenannten Massenrupturen der Rotatorenmanschette

Ohne Zusammenfassung      

Betrachtungen zur notwendigen Stabilität und zur Biomechanik der Frakturheilung bei Fixateur-externe-Osteosynthesen

In recent years, many investigators have concerned themselves with improving the construction of the external fixateur in order to achieve even greater stability. Clinical observations demonstrate a moderate callus formation and an often considerably delayed fracture healing resulting from such an extreme rigid mounting of the external fixateur. This report presents viomechanical considerations which indicate that extreme rigidity in the external fixateur is not only unnecessary, b ut may even interfere with fracture healing and the formation of functionally stable bone.     

Biomechanik von Knorpel-Tissue-Engineering-Konstrukten

Specific biomechanical properties represent important quality markers of cartilage tissue engineering (TE) constructs. The aim of the study was to identify a sensitive biomechanical test to assess mechanical properties of cartilage TE constructs. Biomechanical testing of in vitro cultivated constructs following the very low rubber hardness (VLRH) principle illustrated significant differences between constructs cultured under chondrogenic conditions over various periods of time. An increase in proteoglycan and collagen type II deposition corresponded to increasing VLRH hardness values. Although a decrease in proteoglycan was detected after ectopic implantation of constructs into SCID mice, no reduction in biomechanical hardness values was observed. A functional estimation of TE constructs requires determination of biomechanical and biochemical parameters as quality features.     

Biomechanik der Schulter

The shoulder joint takes a special position among all the other joints of the human body because of its special requirements of stability and mobility. Knowledge of the biomechanics of the shoulder joint forms the basis for the development of modern concepts of reconstructive surgery and arthroplasty. Most of the biomechanical findings are the result of research performed on cadaver shoulders using increasingly sophisticated methods of measurement. These studies elucidate the interaction of the static and dynamic factors which contribute to the delicate balance of the glenohumeral joint. Recently performed research is increasingly being focussed on more detailed analyses of muscle forces and stress distribution in the subchondral bone and periarticular soft tissues. The efficiency of the computer systems now available has enabled the development of complex, virtual shoulder models and three-dimensional finite element analyses. In the future a pure mechanical understanding has to be modified to extend to a concept which includes more data obtained from living subjects, especially with regard to muscle activity under varying loads and neuromuscular feedback systems which currently are difficult to assess.     

Biomechanik der Kyphose

Kyphosis is a dorsally convex curvature of the spine in the sagittal plane. A pathological kyphosis of the thoracic spine has a Cobb angle greater than 50 degrees. It occurs when the anterior and/or posterior load-transferring elements of the spine are overloaded or damaged. Wedge-shaped vertebral bodies may be found at one or several levels. A wedge-shaped vertebral body increases the curvature of the spine and moves the centre of gravity of the body parts above of the corresponding vertebral body in a ventral direction. This increases the flexion-bending moment acting on the spine. In the case of a wedge-shaped deformation of a vertebral body, the relative increase of the flexion moment is a function of the wedge angle and of the original position of the centre of gravity of the upper body.     

Biomechanik distaler Radiusfrakturen

Fractures of the distal radius are most commonly caused by hyperextension injuries of the wrist. Tensile forces and force vectors, strength of impact, bone strength and soft tissue tension create individually different fracture patterns. Metaphyseal comminution, loss of cortical support, ligament avulsion and shear fragments are defining parameters for fracture instability. The dislocation of the articular fragment follows the force vectors of the extrinsic forearm muscles bridging the joint. The goal-plan-standardized (GPS) treatment strategy has proven to be helpful in choosing the ideal individual treatment. It is based on individual patient demands on wrist function and an analysis of fracture instability in computed tomography (CT) scans. The “goal” is a realistic expectation assessed by patient and surgeon. The “plan” includes a benefit-risk analysis and selection of an appropriate treatment modality. The “standardized treatment” of surgical and follow-up treatment is based on biomechanical knowledge. Locking plate osteosynthesis aims to neutralize dislocating force vectors and to allow early active mobility. Unidirectional instability can be indirectly neutralized by palmar locking plate systems. A multidirectional instability can be addressed by multiple plating following the column theory. Distal shear and avulsion fractures may require a fragment-specific osteosynthesis approach.     

Biomechanik der Frakturbehandlung

Background

The local mechanical environment is one of the key elements for the successful healing of bone fractures.

Biomechanics of osteosynthesis

The choice and implementation of the fracture fixation technique (e.g., the type and performance of the osteosynthesis) determine this mechanical environment. It can be characterized by the stiffness and strength of the bone–implant construct. Bone–implant stiffness primarily determines the temporal course of the healing process by providing the mechanical window for bone formation and bone remodeling. Bone–implant strength on the other hand determines the load-bearing capacity and also influences the failure characteristics of the specific fracture healing construct.

Requirements for osteosynthesis/development of optimized implants

The requirements for successful fracture treatment depend on the anatomy and physiological loading situation of the individual bone. Thus, different requirements have to be respected for treatment of diaphyseal compared to epi-/metaphyseal fractures. Diaphyseal fractures require a certain amount of dynamic interfragmentary movement in order to stimulate secondary healing by periosteal callus formation. Fractures around a joint on the other hand rely on accurate restoration of joint congruity and its retention. Based on these different requirements, osteosynthesis implants can be optimized according to their mechanical performance and safe application for patient treatment.     

Unfallanalyse und Biomechanik

The number of claims linked to whiplash injuries is steadily increasing in most European countries. After minor accidents the question often arises as to whether the occupant could really have been injured. The technical expert may calculate the biomechanical stress imposed on the occupants by the impact from the evidence gathered after the accident. Based on this data the medical expert is able to judge whether this stress was sufficient to produce the injury claimed. The threshold of biomechanical loading necessary for spinal injuries will be deduced from a technical perspective. With the help of examples, the steps required to preserve evidence will be explained.     

Zur Biomechanik der Schenkelhalsnagelung

Zusammenfassung Unter Berücksichtigung der eigenartigen anatomischen Verhältnisse der Schenkelhalsgegend im Senium wurden die biologischen und mechanischen Voraussetzungen der Immobilisierung der Schenkelhalsfraktur revidiert. Eine Verbesserung der Heilergebnisse wird von einer verbesserten Immobilisierung der Fragmente erhofft. Es wird ein neukonstruierter Nagel beschrieben, wobei seine die biologischen und mechanischen Eigenarten des senilen Schenkelhalses berücksichtigenden Charakteristika — wodurch eine bessere Immobilisierung erzielt wird — hervorgehoben wurden. Über die endgültigen Ergebnisse wird erst später berichtet. Eine vorläufige Mitteilung schien aber mit Rücksicht auf die komplikationsfreie Anwendung des Nagels bei 30 unselektierten nacheinander die Klinik eingelieferten einschlägigen Patienten statthaft, unter denen kein Herausgleiten des Nagels, keine Redislokation und keine Pseudarthrose vorgekommen ist.

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Summary The author analyses the mechanical and biological conditions of a better fixation of the fracture of the femoral neck, taking into consideration the specific relations of old-age femoral neck. He is of the opinion that the poor results obtained hitherto in healing femoral neck fractures could be improved by means of better fracture fixation. He describes the advantages of the nail he constructed, having taken into account the biological and mechanical characteristics of old-age femoral neck. The evaluation of the results and the drawing of final conclusions can, of course, take place only later, but the fact, that in the first 30 unselected cases of operating with the described technique the early complications such as: nails slipping out, redislocation, and pseudarthrosis did not occur even once, justifies the author in issuing a preliminary report.

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Résumé L'auteur analyse les conditions méchaniques et biologiques de la meilleure fixibilité de la fracture du col du fémur prenant en considération les relations spécifiques du col du fémur sénile. Il lui semble que les résultats pitoyables de la médication de la fracture du col du fémur puissent etre curables par une meilleure fixation de rupture. Il fait connaitre son clou construit par la prise en considération les spécialités biologiques et méchaniques du col du fémur sénile et les avantage de celui-la. De l'évaluation des résultats et de tirer les dernieres conséquences ne peut etre en question que plus tard, mais a la communication préalable donne le droit ce fait que dans les premiers 30 cas — tout venant — soignes par la technique traitée ci-dessus les accidents précoces du clouage du col du fémur ne se sont pas présentés: glissement du clou, recislocation, pseudoarthrose.

     

Analyse der Biomechanik des Kiefergelenks

Modern technologies provide new methods for an accurate recording and biomechanical quantitative analysis of the masticatory system in motion and especially the temporomandibular joint (TMJ). In particular, the combination of anatomical and kinematic data of asymptomatic subjects and patients suffering from TMJ disorders yields new and more precise information. The techniques used not only provide images and videos for didactic purposes but also allow researchers to make inferences on joint loading and the possible mechanical origin of degenerative joint disease. Furthermore, monitoring of masticatory muscle activity in the natural environment provides data on masticatory muscle behavior. Thus, not only snapshots or short laboratory recordings of TMJ biomechanics can be taken but it can also be assessed whether a prolonged loading of masticatory structures can be detrimental. It is also worth mentioning that with digital technology and virtual reality it is possible to create true virtual articulators that no longer approximate mandibular motions but exactly replicate patient-specific movement patterns. The biomechanical information can also be replicated on live tissue and the biological response to typical TMJ loading patterns in the time dimension can also be retrospectively analyzed.     

Biomechanik und Biochemie der Gelenkfrakturen

Ohne ZusammenfassungMit 6 Abbildungen     

Differenzialindikationen aktueller Endoprothesensysteme der Schulter

Modern shoulder prostheses adapt to the size, inclination, posterior offset and retrotorsion of the shoulder anatomy. Typical implants are cup prostheses for surface replacement, stemless prostheses that anchor in metaphyseal bone, anatomical prostheses using stems of different lengths, and last but not least reverse prostheses. The main reasons for implantation of shoulder prostheses are primary osteoarthritis, posttraumatic and rheumatoid arthritis, avascular necrosis, arthritis of instability and cuff defect arthropathy. Anatomical hemiprostheses should be used only if the glenoid is intact as total prostheses are functionally better as soon as the arthritis involves the glenoid. Conventional stems are cemented most of the time and cemented glenoids that are convex on the back are standard. Stemless prostheses were developed for posttraumatic indications and can often replace stemmed designs if the bone quality is good. Reverse prostheses were developed for the treatment of cuff tear arthropathies but if used as a revision implant complication rates rise and survival time is shorter.     

Design und Biomechanik inverser Schulterprothesen

Reverse shoulder arthroplasty has developed from a salvage procedure for a small group of selected patients with pseudoparalysis to a standard procedure for a variety of shoulder diseases associated with rotator cuff insufficiency. By inversing the joint surfaces the humeral head can be stabilized on the glenoid despite an insufficient rotator cuff. A normal shoulder function, however, cannot be expected after such a procedure. Reverse prostheses medialize the centre of rotation and distalize the humerus. This has an influence on the range of motion, the lever arms, the forces and the stability of the reconstructed joints. The currently used prosthesis models differ in many parameters. The following article describes the most important features and biomechanics of reverse prostheses.     

Anatomie und Biomechanik des Kahnbeins

The scaphoid is biomechanically and clinically of great importance for function of the wrist. In the literature, its anatomy and biomechanics are clearly underrepresented as well as underestimated. In the following review the scaphoid will be presented in more detail, according to recent information and findings. Not only will the origin of the name and the history of previous names, such as cotyloid or navicular, be introduced, but also for the first time in medical literature the significant phylogeny and ontogeny of the scaphoid will be shown. Moreover, the clinically very important blood supply, the ligaments of the scaphoid and relevant biomechanical details will be described.     

215. Biomechanik der Zuggurtung

Zusammenfassung Empfehlungen, Zuggurtungsdrähte durch Weichteile zu legen, sind unsinnig, well ohne direkten Knochenkontakt Bruchflächen durch Draht nicht komprimiert werden können. Patella- und Olecranonfrakturen und -pseudarthrosen heilen durch laterale Zuggurtung stufenlos knöchern aus, well sie dauerhafte, hohe interfragmentäre Kompression gewährleistet.Starrer Cerclagedraht ist für Zuggurtungen allerdings ungeeignet, well sich die Knickbildungen und Schlaufen unter Beübung strecken und die Verzwirbelung rückdrehen kann, so daß die primär erreichte Stabilität durch Abfall der Drahtspannung verloren geht. Deshalb wird anstelle starren Drahtes ein komplettes Set für Zuggurtungen mit normiertenDrahtseden, mechanischen Klemmvorrichtungen und neu konzipiertem Drahtspanner vorgestellt, das die Anlegung einer Zuggurtung technisch vereinfacht und permanente Kompression garantiert.     

Stabilitätsuntersuchung aktueller Gipsersatzstoffe

In connection with company independent test series the clinically required usefulness of four different modern plaster substitutes were examined. A comparison of breakage resistance, deformation and relation of price versus stability of plaster bandages were considered. The advantage of using these materials, especially in case of prolonged cast immobilization, is-despite of higher financial costs-more appropriate because of lower weight, increased durability and hygienical comfort for the patients.     

Anatomie und Biomechanik des Patellofemoralgelenks

The patellofemoral joint constitutes a complex anatomical and functional entity. The tensile force of the quadriceps femoris muscle is transmitted through the patella and patellar ligament onto the tibial tuberosity. This particular three-dimensional arrangement increases the torsional moment acting on the knee joint. Dynamic alignment of the patella is determined by trochlear geometry and is supported by active muscular and passive connective tissue stabilizers. In addition to the retinaculum of the patella, the medial patellofemoral ligament is attracting increasing clinical attention. Multidirectional motion of the patella is closely connected to retropatellar pressure distribution which can be modulated by moving the patellar ligament insertion. Implantation of a knee endoprosthesis changes the joint surface geometry and consequently patella kinematics and retropatellar pressure distribution. Finite element analysis provides the possibility to assess retropatellar pressure distribution before and after implantation of prostheses.