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желчного пузыря, как фактора дестабилизации коллоидного состояния желчи.
K.J. van Zwieten a, P. Helder b, P.L. Lippens a, K.P. Schmidta,
I.A. Zoubovac, O.E. Piskun c, S.A. Varzin c, A. V. Zinkovsky c
INTEROSSEOUS MEMBRANE (IOM) EXTREME TAUTNESS IN FOREARM NEUTRAL POSITION, EVIDENT FROM IN VITRO ANATOMICAL OBSERVATIONS, STRONGLY SUGGESTS UNWISHED EFFECTS ON FINGERS AND THUMB LONG MUSCLES, DURING REPETITIVE TASKS IN VIVO
aFunctional Morphology, Anatomy, Universiteit Hasselt, BioMed, Diepenbeek, Belgium; bHandShoe Mouse, Hippus NV, Rotterdam, The Netherlands; cDepartment of Health Sciences and Biomechanics, St. Petersburg State Polytechnic University,
IMOP, St. Petersburg, Russia
Introduction, identifying the problem Shifting the conventional, horizontal computer mouse over e.g. a mouse-mat includes crossed positions of the radius over the ulna in the forearm, which is also known as pronation. In modern man using the PC-mouse, prolonged pronation easily leads to undue tension in muscles and joints (1), thus eliciting certain forms of the much-dreaded repetitive strain injuries (RSI) (2). Traditional mice force the base of the palm to be horizontal to the work surface, which increases wrist and forearm pronation and elevates intracarpal tunnel pressure and the risk for injury (3).
With regard to the design of PC-mouse positions, various adjustments have been proposed to prevent injuries by using vertical or joystick-mice (4). Thanks to the necessary “handshake” or neutral position of the forearm, vertical mice in particular are assumed to leave thumb and fingers relatively free (5, 6) so as to prevent strain in forearm muscles and joints. Such solutions seem the more beneficial since they are considered as a possibility to use more frequently the long muscles of fingers (especially index) and thumb, whose origins are all situated in the forearm, thus preventing unwished overuse-effects of the smaller muscular units, that are well-documented (7, 8). Anatomical in vitro studies however suggest negative effects of “neutral” forearm positions (9, 10).
The convincing anatomical observations used to support this hypothesis are shortly repeated below.
Full supination of the forearm Forearm interosseous membrane, bridging the distances between the interosseous borders of ulna and radius, is undulated and rather lax. Most thumb and fingers long muscles originate here (Fig. 1)
Forearm transverse 0: diagrams of the interosseous membrane (IOM) (after Csillag 1999, adapted)
Neutral position of the forearm The ulna remaining unchanged in the frontal plane, the radius now lies in a sagittal plane, i.e. orthogonally perpendicular to the frontal plane. The radius’ interosseous border forms a convex arch with respect to the ulna’s interosseous border that still lies in frontal plane. As a consequence of the increased distances between them, the interosseous membrane appears to be taut (Figure 2).
ulna
Deep
finger <3 flexors
Deep
extensors
IOM
radius
Figures 1a and 1b
Anterior view of a left forearm anatomical wet specimen in neutral position in vitro. Elbow and wrist joints were preserved, as well as lower half of the bony humerus (right). With respect to the ulna (top), the radius (bottom) shows curvature of its bony interosseous border to be arched, causing the strong interosseous membrane (IOM) to be extremely taut in this forearm position here.
Pronation of the forearm Anatomical evidence shows forearm interosseous membrane to become lax and undulated again, as the radius’ and ulna’s interosseous borders have re-approached each other, in this position (9, 10).
In pronation in vivo, the tilt of a lightly slanted PC mouse positions the wrist and the forearm at a natural angle causing minimal forearm muscular activities needed to handle such types of mice (12)
Discussion In view of the molecular properties of skeletal muscle tissue, we like to stress the importance of the data presented above, based upon the observed maximal IOM tautness. As a skeletal muscle derives most of its force from bone periosteum, as well as from fascial sheaths and collagen membranes, forearm interosseous membrane and periosteum will be heavily relied upon by fingers and thumb deep long muscles arising here (13), in long and repetitive contractions at forearm neutral positions.
Proprioception- and pain-registering organs located here too (13) may then lead to pain complaints.
A taut non-compliant interosseous membrane will require more of the elasticity of a normal muscle cell, causing subtle unwished molecular changes to occur during muscular contractions (14, 15, 16)
Further, whereas a lax interosseous membrane will offer compliance in supination and pronation, regarding pumping up effects by contracting muscles within their compartments, a taut interosseous membrane at forearm neutral position might on the contrary evoke “compartment syndromes” (17).
As was demonstrated, intramuscular biochemistry too is disturbed by compartment syndromes (18).
Figure 2
Conclusions 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 (19, 20).
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 (12)
Figures 3 a and 3b
Lightly slanted mice like the ones shown here require less muscular activity (Chen & Leung 2007)
Acknowledgments The authors wish to thank Prof. Dr. S. Hendrix MD (Chair),
Prof. Dr. M. Vandersteen MD, Prof. Dr. L. Vanormelingen MD, Dr. K. Palmers MD, Mr. D. Mathijsen MSc and Mr. D. Janssen BSc of the Department of Anatomy, University of Hasselt, for their interest, and for their kind cooperation.
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1 2 12 F. H. M. Narain , K. J. van Zwieten , K. S. Lamur , P. L. Lippens ,
K. P. Schmidt2, O. E. Piskun 3, S. A. Varzin 3, I. A. Zoubova3,
A. V. Zinkovsky 3
EVERSION OF THE FOOT AT TOUCHDOWN
1 Department of Anatomy, Anton de Kom University of Suriname, Paramaribo,
2
Suriname; Department of Anatomy, BioMed, University of Hasselt, transnational University Limburg, Diepenbeek, Belgium; Department of Biomechanics and Valeology, Saint-Petersburg State Polytechnic University, Saint-Petersburg
Normal bipedal human walking over a flat surface, divided in a stance phase and a swing phase for each leg, is characterized by (among others) heel strike at the beginning of stance (1). To prepare for each following heel contact, the foot is extended at the ankle joint, at the end of the swing phase. The strong ankle extensor muscle m. tibialis anterior however, responsible for this movement, simultaneously causes foot inversion too (2). Foot inversion is defined as turning the sole of the foot inward, while eversion is turning the sole of the foot outward. Normally, heel contact is immediately followed by an eversion of the foot, to prevent a walking person so to say to land on the lateral side of his foot which easily leads to a so-called “inversion traumatism” (3)
Because inversion traumatisms constitute e.g. the most frequent sport traumatisms (3), while at the same time foot eversion is considered as being typical for human plantigrade walking (4), it may be interesting to analyse walking strategies in non-cursorial mammals, such as primates and predecessors like the marsupial opossum (Didelphis) whose terrestrial locomotion is plantigrade-quadrupedal (5). Various higher primates lack initial heel contact in stance (б), as do lower primates and opossum (2). Regarding extinct marsupials moreover, it is clear that “Thylacynidae (had) feet small with spreading toes” and “In gait, the Santa Cruz thylacynes were probably plantigrade” (7). Thylacine footage reveals spreading of toes indeed, during its swing phase (S). This had been observed already, it was explicitly described in Didelphis (9, 10). Here abduction and extension of toes does include foot eversion. The latter is the more relevant, in view of the extreme inversion of the opossum foot at end-stance (11, 12). In general, mm. fibulares are held responsible for repositioning the foot from inversion to eversion. M. fibularis tertius, acting simultaneously with toe extensor muscles, deserves particular attention, especially in man (13). In the swing phase m. fibularis tertius “levels the foot and helps the toes to clear the ground” (4).
As a practical application of some of the above observations and analyses we cite a recent report concerning strength-training, applied to mm. fibulares in particular, in youthful gymnasts (14).
This training, performed as a warming-up, produced longer periods of continuous
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