Prehension pattern in upper extremity.pptx

Prehension pattern in upper extremity

1. PREHENSION

2. Prehension activities of the hand involve the grasping or taking hold of an object between any two surfaces in the hand; the thumb participates in most but not all prehension tasks. There are numerous ways that objects of varying sizes and shapes may be grasped, with strategies also varying among individuals . Prehension can be categorized as either power grip ( full hand prehension) power grip, in which the object makes full contact with the palm and is moved through space. precision handling (finger-thumb prehension ) precision handling, in which the thumb and fingers dynamically manipulate the object.

3. Holding object Sequence of ( 1) opening the hand, ( 2) positioning the fingers, ( 3) bringing the fingers to the object, and ( 4) maintaining a static phase that actually constitutes the grip.

4. POWER GRIP The fingers in power grip usually function in concert to clamp on and hold an object into the palm. The fingers assume a position of sustained flexion that varies in degree with the size, shape, and weight of the object. The palm is likely to contour to the object as the palmar arches form around it. The thumb may serve as an additional surface to the finger-palm vise by adducting against the object. 4 types Cylindrical grip Spherical grip Hook grip L ateral prehension

5. The three varieties of precision handling that exemplify this mode of prehension are pad-to-pad prehension , tip-to-tip prehension , pad-to-side prehension .

6. Cylindrical grip Cylindrical grip almost exclusively involves use of the flexors to carry the fingers around and maintain grasp on an object. The function in the fingers is performed largely by the FDP muscle, especially in the dynamic closing action of the fingers. In the static phase , the FDS muscle assists when the intensity of the grip requires greater force. Cylindrical grip is typically performed with the wrist in neutral flexion/extension and slight ulnar deviation . Ulnar deviation also puts the thumb in line with the long axis of the forearm .

7. Spherical grip Spherical grip is similar in most respects to cylindrical grip. The extrinsic finger and thumb flexors and the thenar muscles follow similar patterns of activity and variability. The main distinction can be made by the greater spread of the fingers to encompass the object . This evokes more interosseous activity than is seen in other forms of power grip. The MP joints do not deviate in the same direction (e.g., ulnarly ) but tend to abduct.

8. Hook grip Hook grip is actually a specialized form of prehension. It is included in power grip because it has more characteristics of power grip than of precision handling . It is a function primarily of the fingers. It may include the palm but never includes the thumb. It can be sustained for prolonged periods of time, as anyone who has carried a briefcase or books at his side or hung onto a commuter strap on a bus or train can attest. The major muscular activity is provided by the FDP and FDS muscles .

9. Lateral prehension Lateral prehension is a rather unique form of grasp. Contact occurs between two adjacent fingers. The MP and IP joints are usually maintained in extension as the contiguous MP joints simultaneously abduct and adduct. This is the only form of prehension in which the extensor musculature predominate in the maintenance of the posture; the EDC and the lumbrical muscles are active to extend the MP and IP joints, and MP joint abduction and adduction are performed by the interossei muscles.

10. Precision Handling The positions and muscular requirements of precision handling are somewhat more variable than those of power grip, require much finer motor control, and are more dependent on intact sensation. The thumb serves as one “jaw” of what has been termed a “two-jaw chuck ”; the thumb is generally abducted and rotated from the palm . The second and opposing “jaw” is formed by the distal tip, the pad, or the side of a finger. When two fingers oppose the thumb, it is called a three-jaw chuck.

11. Pad-to-pad prehension Pad-to-pad prehension involves opposition of the pad, or pulp, of the thumb to the pad, or pulp, of the finger. The pad of the distal phalanx of each digit has the greatest concentration of tactile precision, 80 % are considered to fall into the category of pad-to pad. The MP and PIP joints of the fingers are partially flexed, with the degree of flexion being dependent on the size of the object being held. The DIP joint may be fully extended or in slight flexion.

12. Tip-to-Tip prehension Although the muscular activity found in tip-to-tip prehension is nearly identical to that of pad-to-pad prehension , there are some key differences. In tip-to-tip prehension , the IP joints of the finger and thumb must have the range and available muscle force to create nearly full joint flexion. The MP joint of the opposing finger must also be ulnarly deviated (with fingertip pointed radially) to present the tip of the finger to the thumb.

13. Pad-to-side prehension Pad-to-side prehension is also known as key grip (or lateral pinch ) because a key is held between the pad of the thumb and side of the index finger. Pad-to-side prehension differs from the other forms of precision handling only in that the thumb is more adducted and less rotated.

14. Functional Position of The Wrist And Hand The functional position is Wrist complex in slight extension (20) and slight ulnar deviation (10) Fingers moderately flexed at the MP joints (45) PIP joints (30) and slightly flexed at the DIP joints The wrist position optimizes the power of the finger flexors so that hand closure can be accomplished with the least possible effort. It is also the position in which all wrist muscles are under equal tension.