The hand of the musician: the kinematics of the bidigital finger system with anatomical restrictions.

Tendons of the fingers are frequently interconnected by anatomic structures that limit the displacements of these tendons relative to each other. In this paper a bidigital finger system in which such interconnections between tendons are present is kinematically modelled. Using this model, an exhaustive description of the effects on finger movement of connections between the different tendons of the fingers is given. The study provides a context for the interpretation of typical difficulties of finger coordination in musicians, especially in pianists and string players.

Biomechanics of the finger with anatomical restrictions--the significance for the exercising hand of the musician.

Exercise and teaching of musicians presupposes in the individual the constitutive ability to freely execute the finger movements required in the playing of the instrument. However, in the hand anatomical restrictions may exist that limit the mobility of the fingers and, thereby, the possibility to determine their movements voluntarily. In this article we investigate the kinematics of a monodigital system in which restrictions are present.

Radioscapholunate ligament: a gross anatomic and histologic study of fetal and adult wrists.

The radioscapholunate ligament was studied using fifty-four dissected adult cadaver wrists. Four of these wrists had arterial perfusions with colored latex and serial sections were made of twenty-one wrists from fetuses ranging in size from 23 to 230 millimeters crown-rump length. The radioscapholunate ligament was consistently identified between the long and short radiolunate ligaments, emerging through the palmar capsule of the radiocarpal joint. It was found to be a neurovascular structure surrounded by synovial tissue with vascular origins from the anterior interosseous and radial arteries and a neural origin from the anterior interosseous nerve. On entering the radiocarpal joint it attaches proximally to the interfacet prominence on the articular surface of the radius and distally to form the proximal membrane of the scapholunate interosseous ligament system. We found no anatomic evidence that this structure should be considered a ligament in a traditional mechanical sense. However, this structure may be clinically important as the vascular supply of the scapholunate interosseous ligament, as well as a sensory pathway from the scapholunate articulation.

The palmar radiocarpal ligaments: a study of adult and fetal human wrist joints.

The palmar radiocarpal ligaments were studied with use of fifty-four dissected adult cadaver wrists and serial sections on twenty-three wrists from fetuses ranging in size from 23 to 230 millimeters crown-rump length. Three palmar radiocarpal ligaments were clearly identified: the radioscaphocapitate, long radiolunate, and short radiolunate ligaments. The radioscaphocapitate ligament originates from the radial styloid process and inserts into the radial aspect of the waist of the scaphoid, hemicircumferentially around the distal pole of the scaphoid and interdigitates with fibers from the palmar aspect of the triangular fibrocartilage complex just palmar to the head of the capitate, with only a minor insertion distally into the body of the capitate. The long radiolunate ligament originates just ulnar to the radioscaphocapitate ligament, being separated from it throughout its course by the interligamentous sulcus. The long radiolunate supports, but is separate from, the palmar aspect of the scapholunate interosseous ligament, and inserts into the radial half of the palmar surface of the lunate. The short radiolunate ligament, previously not described, originates just palmar to the lunate facet of the distal radius articular surface and inserts as a flat sheet of fibers into the proximal margin of the palmar surface of the lunate. Each ligament is intracapsular, enveloped within a continuous superficial fibrous stratum and deep synovial stratum.

Functional morphology of the hindlimb in some lacertilia.

Based on a global exploration of the hindlimb in some lacertilian species, an equally global functional approach has been undertaken, which led to the concept of the crural mechanism, an integral mechanism comprising the knee joint and the joints between respectively tibia and fibula on the one hand and the astragalocalcaneum on the other. Simple models explain the position of muscles and ligaments in relation to the homonymous rotation of tibia and fibula as well as the relative anterior displacement of fibula in front of the tibia. The linkage of knee and ankle joints appears to be based on those morphological features in both proximal and distal joints, that preclude pure axial rotations of tibia and fibula without deviation of these bones, again in both knee and ankle. The final result appears to be an integral mechanism endowed with one degree of freedom. An attempt has been made to identify the significance of the crural mechanism for function of the hindlimb in sprawling gait.

The hand and hominisation.

Morphological features of the hands of Varanus, Iguana, opossum and primates were disclosed by dissection and an attempt was made to a functional assessment of the findings. A simple functional morphological pattern seems to prevail in the reptiles studied. A specialised function of claw retraction could explain the complex digital morphology in opossum. Already in opossum functions cannot be defined sharply. Functional domains and functional options within these domains become the prevailing picture in primates. Hand morphology of the great apes and man warrants to distinguish one functional domain. In man a full-fledged thumb dominates the hand morphology next to other features, which could be functionally interpreted as a unique setting for perception of form. This could have been a primary drive in cerebral development and hominisation.

A comparison of fingers and hand in varanus, opossum and primates.

A comparative analysis of hands constitutes the basis of an assessment of hand function in an evolutionary context. Terms as functional domain and functional options are instrumental to define the functional expansion, which can be seen when comparing reptiles, opossum and primates. In man the structural arrangement can be interpreted in functional terms only by terms as functional continuum or universe and by performance control. In the great apes knuckle walking and brachiation seems to interfere with a full-fledged pollical-digital interplay, the latter function being considered to constitute the structural base of optimalization collecting afferent information, requiring brain development, which opens up categories as abstraction, design and freedom.

The human hand in phylogenetic perspective.

Comparative studies contribute substantially to our understanding of the function and structure of the hand. Introduction of the term "working space" proved to be useful for the development of a phylogenetic concept of hand function. It seems likely that there is a functional continuum within the working space of the human hand. Functional options are basically not limited, but have to be designed, learned, and developed. Performance control becomes a major issue.

Internal stabilization in the thumb.

An analysis of the thumb as an articular chain, with the biarticular tendon displacement used as a model, is presented. Comparison of the extensor pollicis longus/flexor pollicis longus (EPL/FPL) tendon displacement ratios at the three joints, as determined from cadaver studies, shows that the thumb will be unstable, with a persistent tendency to extend at the carpometacarpal (CMC) joint and flex at the interphalangeal (IP) joint when it is under the exclusive control of the EPL and FPL muscles. In addition, according to the model, with stabilization of the CMC joint, the MCP joint will tend to extend and the IP joint will flex. Clinical data from thumbs of leprosy patients with thenar paralyses largely confirm these predictions and the validity of this approach in studying the functional behavior of the thumb.

The extensor assembly in two species of opossum, Philander opossum and Didelphis marsupialis.

In considering primate and hominoid phylogeny, the fundamental position assigned to opossums is explained partially by the characteristic morphology of their hands and feet. One of the main functional features of the human hand is the ability to make a stabilized arch of the finger. Because the extensor assembly plays a key role in establishing an arched finger, the extensor systems of the digits of both the hands and feet were studied in two species of opossum, Philander opossum and Didelphis marsupialis. In the foot, two extensor tendons join in each toe to form one tendinous plate, which inserts onto the base of the second phalanx. Lumbricals join this plate along the tibial side, and interosseus insertions are found, although a true interosseus wing is lacking. At the proximal interphalangeal level, a terminal tendon takes its origin from this tendinous plate. This terminal tendon is oval in cross-section and contains elastic structures. Oblique bands arise from this terminal tendon and run proximally along the proximal interphalangeal joint inserting onto the base of the first phalanx. There are elastic structures in the flexor tendon on the dorsal side near its site of insertion. In the hand, the main extensor tendons are arranged differently and the interossei contribute substantially to the extensor assembly. Otherwise, the extensor assembly of the hands and feet are quite similar. The function of the so-called paratendinous intravaginal flexors is discussed as are evolutionary aspects of the extensor assembly.

[Proximal interphalangeal articulation in man]. / Quelques observations sur l'articulation interphalangienne proximale chez l'homme

A report is presented on microdissections of the proximal interphalangeal joint, in particular the proximal attachments of volar plate and tendon sheath. The proximal anchorage of the joint capsule is assured by three components, occurring bilaterally. A. Laterobasal and retrochlear fibres. B. An internal cord which inserts along the inner side of the line of attachment of the osteofibrous sheath of phalanx I; C. The cruciform ligament of the sheath which is inserted at the outer side of the osteofibrous sheath of phalanx I.