[The carpus in the conflict between stability and mobility]. / Der Carpus im Konflikt zwischen Stabilität und Mobilität.

The stability of the carpus is determined by a precise interaction of the osseous and ligamentous elements. The main load of the carpus responsible for the adaptation of concerned tissues is a longitudinal compression caused by the force of the muscles of the forearm with their insertions to the metacarpus and fingers. As a consequence, the proximal row is distracted due to the wedge-shaped form of the hamatum together with the capitatum. It is the function of the mainly oblique orientated ligaments to take these transverse tensional forces, supported by the circular arrangement of the retinacula. Here, the ligaments are described in respect of their precise course into three groups. The distribution of material which is needed for bearing the enormous static and dynamic forces is minimised by the integration in a system of oblique fibre bundles which guaranties that all elements, osseous as well as ligamentous, are involved in the force distribution. This is the prerequisition for the minimalisation of osseous material. On the other hand, damage of only one element can cause severe consequences to the stability of the whole system.

[Evolution of the hand]. / Evolution der Hand.

The skeleton of the human hand has its evolutionary origin in the anterior fin of primitive fishes following a reduction process. Starting with 20 to 30 elements, the number of bones reduces to eight. This does not follow a continuous pattern but is influenced by environmental factors. This becomes particularly evident when considering the development of the opposition of the thumb. The muscles of the hand evolve from dorsal and palmar compact plates which are divided into two layers. The differentiation process follows the development of the fingers. The development of the individual hand is controlled by a group of homeobox genes. Comparable genes are found in many different species. The more recent evolution of the hand can be understood as the expression of the development of the brain. Therefore, the hand is a direct tool of our consciousness. It is a main source of differentiated tactile sensations as well as a precise working organ. Gestures, finally, are direct expressions of our personality.

The carpus in the conflict between stability and mobility.

The stability of the carpus is determined by a precise interaction of the osseous and ligamentous elements. The main load of the carpus responsible for the adaptation of concerned tissues is a longitudinal compression caused by the force of the muscles of the forearm with their insertions to the metacarpus and fingers. As a consequence, the proximal row is distracted due to the wedge-shaped form of the hamatum together with the capitatum. It is the function of the mainly oblique orientated ligaments to take these transverse tensional forces, supported by the circular arrangement of the retinacula. Here, the ligaments are described in respect of their precise course into three groups. The distribution of material which is needed for bearing the enormous static and dynamic forces is minimised by the integration in a system of oblique fibre bundles which guaranties that all elements, osseous as well as ligamentous, are involved in the force distribution. This is the prerequisition for the minimalisation of osseous material. On the other hand, damage of only one element can cause severe consequences to the stability of the whole system.

[Menisci and synovial folds of the metacarpophalangeal joint of the thumb]. / Menisci und Synovialfalten des Daumengrundgelenkes.

The inner surface of 25 thumb metacarpophalangeal joints were investigated and the arrangement and structure of different folds protruding into the joint cavity at the level of the joint cleft studied. At the ulnar and radial sides, compact wedgeshaped folds are found consisting of collagenous fibres, which connect with the fibrous layer of the joint capsule. The circularly arranged fibrous tissue is covered by a thin layer of cartilaginous cells. From a structural and functional point of view they are comparable to the menisci of the knee joint. In contrast, a different kind of tissue is found at the palmar and dorsal circumference of the joint cleft: typical synovial folds, consisting of loose connective tissue and small fat lobules. These are suggested not to fulfill a particular mechanical function but to act as a malleable spacer which is able to conform to the requirements of joint mobility.

Periarticular fiber system of the shoulder joint.

The structure and attachment of the glenoid labrum were examined from the functional point of view in 42 shoulder-joint cavities using a combination of macroscopic and microscopic techniques. The labrum continues the long tendon of the biceps as far as the ventral glenoid notch and is supplemented by a connecting band between the superior and inferior glenohumeral ligaments. In the upper quadrants, the periarticular fibers are broadly attached to the neck of the scapula and separated by a gap from the articular cartilage. In the lower quadrants, they are attached to both the neck of the scapula and the joint surface. The periarticular structures consist of bundles of parallel collagen fibers that run round the entire circumference of the cavity. The labrum, glenohumeral ligaments, and inserting tendons form a basket of fibers around the neck of the scapula, which constitutes a functional unit: the periarticular fiber system (PAFS). This acts as a tension-brace for the joint cavity and takes part in the local transmission of pressure through the cavity. Detachment of the labrum, or the labral-biceps anchor, should only be diagnosed when it can be shown that the tissue between the PAFS and the upper part of the neck of the scapula has been torn, and that the extent of the gap formation reaches laterally and caudally beyond the peripheral edge of the cartilage.