Chapter 2. Prehension

Chapter 2 - Prehension 29
test object’ (Skerik et al, 1971, p. 102). Unique to their taxonomy is
the argument that the lateral pinch (see Figure 2.1) is a link grip or a
bridge between power grips and precision handling since ‘it possesses
some of the characteristics of both precision and nonmanipulative
grasps but cannot be considered a pure form of either’ (Skerik et al,
1971, p. 101). Occurring between the thumb and radial side of an-
other finger, the lateral pinch is similar to a power grasp in that it is an
isometric muscular contraction. At the same time, manipulation can
occur using movements of the thumb and/or finger, using the thumb
pad in particular to provide sensory information about the object’s
state. Lacking is both the strength of the power grasp and the manipu-
lative range of precision handling. It is interesting to note that whereas
most other researchers put the lateral pinch as a precision operation,
Cutkosky and Howe placed it on the power grasp side.
2.2.5 The adduction grasp
An interesting feature of the human hand is that there are a multi-
tude of surfaces, oriented in different ways. Objects, such as
cigarettes, can even be held between the fingers. In a formal classifi-
cation study performed by Kamakura et al. (1980), seven subjects
were photographed holding 98 different objects and a hierarchical
classification was developed. Fourteen postures were observed within
four major types: power, precision, intermediate, and adduction.
Postures were classified into types based on finger and/or palm in-
volvement and amount of contact area on the hand. Of note here, a
posture called the adduction -grip (see Figure 2.4a) was used for hold-
ing a small, light object such as a cigarette between the index and
middle fingers. Other uses of this posture are seen when small objects
need to be removed from tight places, such as grasping coins from
pockets. Napier (1980) calls this the scissor grip. In contrast,
Kapandji (1982) describes this grip anatomically as the interdigital lat-
ero-lateral ET~D.
2.2.6 Gravity dependent grasps
According to Napier (1956), the hook nriD (illustrated in Figure
2.1) doesn’t involve the thumb and is used when precision require-
ments are minimal and power needs to be exerted for long periods, as
in carrying a suitcase. In the 1970’s, the French hand surgeon
Kapandji developed an extensive taxonomy in an attempt to identify
hand functionality for reconstructive surgery (Kapandji, 1982). He