"Medial prehension", a new pen method - Mediaali-ote, uusi kynämetodi

Look at this video too : 

http://ethnosciences.blogspot.fi/2016/01/medial-prehension-to-hold-pen-or-pencil.html

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Antti Hernesniemi, Dr Med Sci 

"Medial prehension",  a new method  of holding a pen during writing and drawing (*)

Young pupils have, for innumerable generations, learned the conventional prehension of  holding a pen in writing and drawing. This grasp is referred to here as "radial prehension"  (R-prehension; presented as seen radially in a drawing, Fig. 1-1). In R-prehension, the writer/drawer holds the shaft of  the pen, supporting it on the area between the first and  second fingers  -  the first interosseus muscle area - and the head of the pen between the  palmar surfaces of the first finger (thumb), the second (index) finger and the radial side of  the third finger. In this article, a new method known as "medial prehension" (M-prehension)  is presented (seen radially in a drawing, Fig. 1-2, and seen anteriorly in a photo, Fig. 2).  The drawing (Fig. 1- 2) presents M-prehension in which the writer/drawer holds the shaft  of the pen between the proximal phalanges of the second (index) finger and third finger and  the head of the pen between the palmar surface of the first finger (thumb), the ulno-palmar side of the second (index) finger and the radial side of the third finger. 

What is necessary for a good pen prehension?

Kapandji (1970, 198 - 201) defines six kinds of hand prehension. Two of  these are important  in pen prehension: Prehension by "subterminal opposition" - as Kapandji calls it - of fingers,  and prehension between the two sides of fingers. The former is used in conventional radial prehension of a pen. The latter represents a medial prehension one of which the author  presents in this arcticle.

  Based on mechanical laws, a writer/drawer must hold a pen at at least two different points  along the pen shaft, or hold the shaft over a rather long portion of it, to be able to write or  draw with a steady grasp. In conventional R-prehension, the head of the pen is held between  the first finger (thumb), second (index) finger and third finger. The shaft of the pen is  supported against the dorso-radial second metacarpal area of the hand, the area of the first  dorsal interosseus muscle (see e.g. Moore 1992).

M-prehension method

In M-prehension method, the head of the pen or pencil, is held between the same fingers but  in a different way from the conventional R-prehension method,  and a long section of the  pencil shaft - several centimeters, depending on the size of the hand -  is held between the  opposite inner sides of the second and third fingers. If more convenient, in M-prehension the  pencil can also be held between the third and fourth fingers. In Figure 2, note the possibility  for a writer/drawer to have a steady grasp on the shaft of the pencil and the pronatio  positioning of the hand,  leaning with the area of the long flexors in the forearm and with both the thenar and hypothenar areas of the hand on the desk.

Author's experiment in using M-prehension

The author studied the work of Finnish folk therapists ("bonesetters") with their patients, recorded on a Super-8 narrow gauge film, with the help of an editor viewer (the approach is presented in the author's thesis; Hernesniemi 1999). The screen of the editor viewer, situated within the instrument,  is about 10 cm x 15 cm. Having made some preliminary sketches, the author noticed that he could not adequately draw sketches from the images visible on the screen with conventional R-prehension. He was unable to adjust the sharp, drawing end of the pencil precisely enough to draw all the necessary areas of the screen (an opaque paper had been placed over the screen). Therefore, he began to experiment with a new pencil prehension, M-prehension. After a short practice period, he could make sketches rather easily  and in a more precise way than earlier. Figure 3 (See Fig. G) presents a "bonesetter's" collaboration with her patient, a drawing made using M-prehension and  with the "positiographical cinemanalysis"- method developed by the author (Hernesniemi 1999).

Advantages of M-prehension in comparison with R-prehension

In R-prehension, the writer/drawer must use several hand muscles to hold the pen in a proper position. According to Kapandji (1970; 198 - 199), these muscles are the flexor digitorum sublimis muscle for the index finger, and the thenar muscles including the flexor pollicis brevis, first anterior interosseus, abductor pollicis brevis and adductor pollicis. Moreover, using R-prehension, the writer/drawer leans his/her wrist on the writing desk, usually having the ulnar side of his/her hypothenar against the desk. As a result of this, the position of the hand is not as stable as when using M-prehension. Using the latter,  one can support the area of the long flexors in the forearm and both thenar and hypothenar areas of the hand on the desk.

  In M-prehension, it is easy to hold the shaft of the pen steadily, which is accomplished using the second interossei muscles, both anterior and posterior (e.g. holding a cigarette, see Kapandji 1970; 200 - 201). It requires minimal energy because of the narrowness of the gap between the proximal phalanges of the second and third fingers, a gap which is well-suited to grasp a thin, long object.

  Further, while using M-prehension, one can control the position of the pen better than with R-prehension. The writer/drawer has a good control of the /drawing over long periods with a pencil using M-prehension is less energy-demanding than with R-prehension. The author has himself  noticed the ease, practicality and preciseness of M-prehension. M-prehension may also be used during various medical procedures where the operator works on the patient's deep tissues using a long instrument such as a sond.

Literature:

Hernesniemi, A (1999). Presentation of bonesetter-patient collaboration through positiographical cinemanalysis. Acta Universitatis Ouluensis. Series D. Medica 538. Oulu University Press. Oulu.

Kapandji, I J (1970): The Physiology of the Joints. Annotated diagrams of the mechanics of the human joints. Volume I. Upper Limb. Churchill Livingstone. Edinburgh London New York.

Moore K L (1992): Clinically Oriented Anatomy. Third Edition. Williams & Wilkins. Baltimore.

Fig. 1-1§

                                                                                           

                                                                                                                                                                  Fig. 1-2


Fig. 1-1.  Drawing presenting "radial prehension" (R-prehension) to hold a pen, as seen from the radial side of the right hand. The writer/drawer holds the shaft of the pen, supporting it on the area between the first and second fingers - the first interosseus muscle area - and holds the head of the pen between the palmar surfaces of the first finger (thumb), the second (index) finger and the radial side of the third finger.

Fig. 1-2. Drawing presenting "medial prehension" (M-prehension) to hold a pen, as seen from the radial side of the right hand. The writer/drawer holds the shaft of the pen between the proximal phalanges of the second (index) finger and third finger and the head of the pen between the palmar surface of the first finger (thumb), the ulno-palmar side the of the second (index) finger and the radial side of the third finger. 

 

Fig. 2. A photo presenting M-prehension during writing/drawing with a pencil. Note the possibility for a  writer/drawer to have a steady grasp on the shaft of the pencil and to hold the hand in a pronatio position, leaning with the area of long flexors in the forearm and with both the thenar and hypothenar areas of the hand on the desk (Photo: AH).

(*) Based on : Hernesniemi, A (2002).  "Medial prehension",  a new method  of holding a pen during writing and drawing. Abstrakti-kirja. Lääketiedetapahtuma 2002.  Helsinki, Finland 2002.   -  Contact :  Antti Hernesniemi,  Dr Med Sci,  MA :    antti.hernesniemi@sll.fimnet.fi