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Enkele minder bekende morfologische eigenschappen en detail-structuren van het Proximale Interphalangeale (PIP-) gewricht van de normale vinger worden besproken, die een rol zouden kunnen spelen bij de pathogenese van reumatoïde artritis. Naast het verloop van de capillairen in het gewrichtskapsel, en het gekruiste, laagsgewijze verloop van de vezelbundels in het proprius collateraal ligament (PCL) van het PIP-gewricht, spreken vooral de intra-articulaire plicae synoviales (synovial folds), en de in het PCL aanwezige gelamelleerde proprioceptieve lichaampjes tot de verbeelding. Ideeën worden geopperd omtrent mogelijke microtraumata van deze structuren. Recente literatuurgegevens suggereren namelijk het pathogenetisch belang van zulke microtraumata, die ook aanleiding kunnen zijn tot chronische gewrichtsontstekingen zoals reumatoïde artritis waarvan de (vroege) symptomen immers vaak de hand betreffen, met name de PIP-gewrichten.

This study offers data on finger joint morphology, revealed by micro-anatomical observations, histological screening, and various high resolution imaging techniques in in-vitro anatomical specimens of small finger joints. Such data may help to understand the use of finger joints while handling PC mice, especially flexing and extending the fingers in e.g. moving a PC mouse scrolling wheel during educational and professional activities. Possible solutions after long standing finger problems are proposed.

In conclusion, we state that curiosity-driven research after normal synovial folds within the PIP-joint of the finger confirms their actual location. Neurovascular bundles in the normal PIP-joint’s capsule, and neurons in lamellated corpuscles within the Proper Collateral Ligament, may shed new light on the pathogenesis of rheumatoid arthritis in human finger joints.

In human and non-human primates, at the level of the proximal interphalangeal joint of the finger, the arrangement of tendinous bands in the extensor assembly as well as the shape of the trochlea of the proximal phalanx determine the rate of release of the third phalanx as seen in e.g., ordinary opening and closing of the hand. In view of the importance of skilled forelimb movements and hand- and finger joint coordination, in prehensile kinematics of human and other primates, we therefore analyse the various morphological characteristics of these structures to some detail, viz. in human, non-human primates, and in a primate ‘predecessor’. Our data corroborate most of the previously published conclusions. In the extensor assembly of the finger, intercrossing of the various fanning-out tendon fibres appears to be a prerequisite par excellence for well-defined tendon-bundle formation (also known as “tendon fasciculation and individualization”). Initially, “in opossum, at the dawn of mammalian eruption, the hand emerged with a [less] complex structure of the extensor assembly”. On the other hand, a predominant parallelism of tendon fibres in the extensor assembly results in more homogeneity. Especially small-sized mammalian species, with short gestation periods, appear to display such homogeneities. The fanning out of tendon fibres in the extensor assembly increases as contrahentes digitorum muscles of the hand become more and more incorporated within the interosseus muscles. As hands of mammals with rather long gestation periods lack mm. contrahentes digitorum in particular, it is challenging to consider some relation between tendon fasciculation and individualization in the extensor assemblies, and ontogenetic processes, in human and other primates.

This short survey is concluded by stating that of all positions of the forearm, its so-called “neutral” position contains the greatest potential source of muscular and other damage during longstanding and repetitive movements of thumb and fingers. Most of this present conclusion is based on evident observations in preserved anatomical specimens of the forearm, supple enough to be compared to the situation in the living. Studies performed by means of modern imaging techniques moreover, applied to the forearms in otherwise normal subjects do clearly support these observations. To avoid the abovementioned effects, as a consequence of PC mice in “handshake” of “joystick” positions, we strongly recommend pronated positions of the forearm, explicitly the somewhat tilted variances e.g. in using lightly slanted computer mice, by proof requiring least muscle activities

Highly intense use of the finger, while handling the computer mouse, as in e-learning, may lead to hand- or finger complaints, e.g. in the elderly. To understand the finger positions concerned, we analysed some of its joints by functional anatomical research. A statically and dynamically stabilised finger arch is needed to prevent complaints. Endorsed by HandShoe Mouse, Hippus NV, Rotterdam, The Netherlands