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BOOK
EXCERPT CHAPTER
FOUR The transition from reflexive grasp patterns to purposeful grasp is an automatic, yet complicated process. It is difficult to determine when reflex activity no longer impacts grasp; there is not a clearly defined age or manner in which one can identify if reflexive behavior has been completely integrated. Pehoski (1992, p.1) states that the ability to use the hand “has a long developmental course,” with the hands at birth being “crude instruments.” Motor control of the upper extremity is based on the principle of proximal and distal development. Kuypers states that “two distinct motor systems control the upper limbs; one proximal, is responsible for the control of large movements of arm and hand, the other distal, controls the subtle coordinations of hand movements” (Corbetta & Mounoud, 1990, p.191). It is thought that the proximal motor systems originate in brainstem structures, while the distal motor systems originate from cortical structures (Pehoski, 1992). Initially, a child’s brainstem provides the proximal control of the upper limb to direct grasp. But as the child develops, control moves from the more basic centers of the brainstem to higher brain structures located in the cortex. The increasing role of the cortical structures provides the individualized finger control needed for precision grasping. This development progression of precise hand movements provides the neurological basis for the mass to specific pattern of development. The mass to specific pattern “indicates that less differentiated movement patterns precede discrete, highly specialized skills” (Exner, 2001, p.293). For example, the infant initially uses the whole hand (or palmar grasp) to pick up a block, which indicates that the infant has not gained the precise motor control necessary to use specialized hand skills, such as in a neat pincer grasp.
In addition to the neurological maturation that occurs as hand skills develop, many other factors must work together for optimal hand function. For example, postural control, motor planning, eye-hand coordination, tactile and proprioceptive input, and somatosensory processing also play a role in the development of a mature grasp. The maturation of grasp also depends on the underlying structures of the hand, such as the musculature, muscle tone, stability of the arches, and separation of the two sides of the hand. Therefore, when using this guide, one should be aware of the numerous factors that contribute to the developmental process.
The following chapter presents the typical developmental sequence of purposeful grasp (Table 4-1). The maturation of grasp should be considered a progression with overlapping sequences (Conner, Williamson, & Siepp, 1978). In other words, children do not typically master a new type of grasp and use it exclusively; experimentation and practice are common. Additionally, the ages presented here are approximate. Therefore, this progression should be used as a general guideline, taking into consideration the individuality of each child (Table 4-2).
REFLEX SQUEEZE GRASPAlternative Grasp Name
DescriptionFollowing the emergence of the grasp reflex, the infant begins to extend an arm toward a desired object but does not yet have the ability to purposefully grasp it in the hand. The infant’s hand extends beyond the desired object (Halverson, 1931) and upon contact pulls the object back toward the body (Gilfoyle et al., 1990). The object is actually held between the hand and the body; this is not considered a true grasp as the hand is not actually grasping the object, but rather it is trapping it (Halverson, 1931). There is no thumb involvement with this grasp (Erhardt, 1994). Grasp at this age continues to be reflexive, and would be initiated by touching or moving an object through the hand (Case-Smith, 1995).
AgeThis grasp is typically seen around 20 weeks or the 4th month of age. Developmental AdvancementThis pattern of corralling the object is adapted from swiping. Swiping, which represents a pattern of early reaching, can be seen between 2 and 2.5 months of age (Ammon & Etzel, 1977), when an infant will glance from object to hand and attempt to contact the object with a full arm movement and closed fist (Gilfoyle et al., 1990). This closed fist is a result of the traction response, which is elicited during the extension of the arm during reach. As the child develops, the hand will be increasingly open during reach (Ammon & Etzel, 1977), helping to enable a true grasp. However, at this developmental stage a coordinated grasp has not developed. CRUDE PALMER GRASP(Gilfoyle et al., 1990)Alternative Grasp Name
DescriptionThe crude palmar grasp typically follows the reflex squeeze grasp. The infant reaches out with a pronated forearm where, upon contact, simultaneous flexion of the fingers press the object firmly against the heel of the hand. The thumb is extended (Halverson, 1931) and does not play a role in pressing the object into the palm (Case-Smith, 1995). The infant’s forearm is resting on a supported surface while actually grasping the object, but once the object is grasped the infant is able to pick up the object and bring it to midline for exploration. The infant is unable to open the hand in relation to the size or shape of the object as the fingers can only partially extend during the reaching pattern. As a result, the hand is placed crudely on the object (Gilfoyle et al., 1990). Finger differentiation is not present. Due to immature motor control and proprioceptive systems, the object is held tightly, which does not allow the object to move within the hand. This grasp is clumsy and is often unsuccessful (Case-Smith & Bigsby, 2000).
AgeThis grasp is typically seen between 20 and 24 weeks or the 4th and 5th months of age. Developmental AdvancementReflexive patterns are becoming integrated and conscious grasp is beginning to take place (Ayres, 1954). The hand has developed the ability to grasp an object, although crudely. To facilitate the development of this grasp, an infant has built on the reflex squeeze grasp and scratching. Scratching is the alternating flexion and extension pattern of the fingers when in contact with various surfaces. Typically developed by 4 months, scratching helps an infant develop full range of reciprocal and combined finger flexion and extension, and provides tactile input to the fingers and palms of the hands (Gilfoyle et al., 1990). This tactile input and reciprocal movement patterns help promote greater awareness of the hand and contribute to the emergence of purposeful grasp. PALMER GRASP(Ammon & Etzel, 1977; Parks, 1988; Erhardt, 1994; Case-Smith, 1995; Duff, 1995; Provence, Erikson, Vater, & Palmeri, 1995; Bruni, 1998; Case-Smith & Bigsby, 2000; Exner, 2001)Alternative Grasp Name
DescriptionThis grasp is characterized by the child putting the pronated hand down on the object, where the fingers flex simultaneously around the object to secure it in the midsection of the palm. The thumb is adducted and not assisting with the grasp (Erhardt, 1994; Case-Smith, 1995; Case-Smith & Bigsby, 2000). As the grasp matures, the object will move from the ulnar side of the hand toward the thenar eminence, and finally to the lower part of the thumb (Illingworth, 1963). In the early stages of this grasp, the forearm is in a pronated position (Case-Smith, 1995), which makes it difficult for the child to visualize the object so the child must rely on tactile cues for feedback about its position within the hand. “Grasp remains palmar regardless of size of object, so that even small objects are taken between fingers and palm and sometimes lost in the palm” (Gilfoyle et al., 1990, p. 163).
AgeThis grasp is typically seen between 20 and 28 weeks or the 5th and 6th months of age. Developmental AdvancementThe forearm continues to be pronated impeding visual guidance. The forearm is positioned in pronation during the child’s first reaching pattern, but by the 6th month, supination of the forearm increases, allowing the child to visualize the grasped object (Case-Smith, 1995). While using the palmar grasp, the infant grasps an object in the midsection of the palm. As maturation and greater motor control are gained, the radial side of the hand becomes more dominant, improving the success of the grasp. The shift to the radial side of the hand “foretells thumb opposition” (Gesell & Amatruda, 1974, p. 60). RADIAL PALMER GRASP(Gesell & Amatruda, 1974; Parks, 1988; Gilfoyle et al., 1990; Erhardt, 1994; Case-Smith, 1995; Duff, 1995; Provence et al., 1995; Case-Smith & Bigsby, 2000)Alternative Grasp Name
DescriptionIn this grasp, the object is secured in the radial side of the palm. The index and middle fingers flex around the object, as the thumb begins to oppose the fingers to press the object into the radial palm. As the grasp matures, the thumb becomes more active (Case-Smith, 1995). The two ulnar digits flex into the palm as they begin to act as a stabilizer for the now more dominant radial side. With the ulnar digits flexed into the palm to provide stability to the radial side of the hand, this grasp represents the earliest example of coupling (which is the differentiation in the function of the two sides of the hand). The object continues to be pressed into the palm, restricting the manipulative movements of higher-level grasps.
AgeThis grasp is typically seen between 24 and 32 weeks or the 6th and 7th months of age. Developmental AdvancementThis grasp marks a significant change in the activity of the hand. The emergence of the instinctive grasp response allows the hand to adjust to the object being grasped. Therefore, objects are grasped in the radial side of the hand (Ammon & Etzel, 1977). This is also the beginning of thumb opposition, which is highly significant for the infant, as opposition is necessary for the continued development of the mature grasp and will be used throughout adulthood. Opposition, along with the prominence of the index finger, is largely responsible for the higher level grasps (Halverson, 1931). Another significant advancement is that the hand now has two definite sides, one that manipulates or grasps and one that stabilizes the movement. This grasp signifies the initial development of the radial side of the hand as the skill side of the hand (Case-Smith, 1995). This differentiation will eventually allow an infant to pick up and grasp two small objects simultaneously (Conner et al., 1978). RAKING GRASP(Parks, 1988)Alternative Grasp Name
DescriptionThe grasp is characterized by the child reaching for and grasping a small object using a raking motion (Erhardt, 1994). The hand is positioned in a rake-like manner with all of the fingers flexed at the IP joints. The fingers, hand, and arm move as one unit to “rake” the small object into the palm (Bruni, 1998). The hand may need support from a solid surface to be successful. This grasp is not always successful, and if it is, manipulation does not occur.
AgeThis grasp is typically seen between 28 and 36 weeks or the 7th and 8th months of age. Developmental AdvancementThis raking motion provides important tactile contact with objects that helps stimulate sensory development, which is needed for the development of grasp. RADIAL DIGITAL GRASP(Gesell & Amatruda, 1974; Parks, 1988; Erhardt, 1994; Case-Smith, 1995; Duff, 1995; Provence et al., 1995; Bruni, 1998; Case-Smith & Bigsby, 2000; Exner, 2001).Alternative Grasp Name
DescriptionThis grasp is characterized by thumb opposition to the radial fingers. The object is held proximal to the pads of the fingers with space visible between the object and the palm. The ring and little finger are flexed. The forearm is in a neutral position when reaching, which provides greater visual direction for grasping. This grasp is similar to the radial palmar grasp, but now the object is held away from the palm, giving the child greater manipulative control. Yet, this grasp is not a fingertip grasp, because the object is held proximal to the pads of the fingers (Halverson, 1931). “[T]he infant can adjust the object within the hand and as a result can use the object for various purposes while holding it” (Case-Smith, 1995, p.117).
AgeThis grasp is typically seen between 32 and 40 weeks or the 8th and 9th months of age. Developmental AdvancementThe fingers are beginning to gain the motor control and proprioceptive feedback needed to begin digital grasping. Sensory feedback is providing the hand with more discrete information, offering the hand increased control and precision. The fingers now have the ability to “maintain the delicately balanced pressure of the digits” (Halverson, 1931, p.218) necessary to secure an object. The developing motor control and proprioceptive systems provide a balance that gives the radial side of the hand the ability to begin to act independently of the palm and the ulnar fingers, giving the child the ability to grasp two objects in one hand (Case-Smith, 1995). DEVELOPMENTAL SCISSORS GRASPAlternative Grasp Name
DescriptionThis grasp is characterized by the object being secured between the adducted thumb and radial side of the flexed index finger. The thumb is not opposed, but slides over in a pattern of adduction to trap an object against the side of the index finger. “The thumb envelops rather than manipulates” (Ayres, 1954, p. 97). The ulnar digits are loosely flexed and do not flex or extend with the radial digits (Gesell & Amatruda, 1974); in the flexed position the ulnar digits provide stability for the radial side of the hand. The hand requires stabilization from a solid surface for successful grasping of the object. Castner (1932) named this grasp the scissors closure due to the similar action of the thumb being drawn to the index finger, mimicking the action of operating a pair of scissors.
AgeThis grasp is typically seen between 32 and 40 weeks or the 8th and 9th months of age. Developmental AdvancementThe thumb is taking on a more independent role in the grasping process, as observed in the separate actions of the thumb and radial fingers. This independent action is necessary for more mature grasps. However, the thumb lacks the ability to oppose the digits, which is necessary for many precision grasps. INFERIOR PINCER GRASP(Conner et al., 1978; Gilfoyle et al., 1990; Johnson-Martin, Jens, Attermeier, & Hacker, 1991; Erhardt, 1994; Duff, 1995; Bruni, 1998; Case-Smith & Bigsby, 2000)DescriptionThis grasp is characterized by thumb adduction and emerging opposition to secure the object against the extended index finger. The object is held proximal to the pad of the finger (Case-Smith, 1995). The extension of the index finger IP joints supports prehension, but not manipulation of the object (Gilfoyle et al., 1990). Depending on the degree of thumb opposition, MCP and IP flexion of the joint of the thumb will vary. The ulnar three digits are flexed toward the palm providing stability. The hand and arm continue to require support from the table to accomplish a successful grasp. At this age, the precision needed for a fingertip grasp has not been developed.
AgeThis grasp is typically seen between 32 and 40 weeks or the 8th and 9th months of age. Developmental AdvancementThe grasp is usually adapted from index finger probing (Case-Smith, 1995), a nonprehensile movement pattern that isolates extension of the index finger with the ulnar digits flexed for stability (Gilfoyle et al., 1990). This beginning of index finger isolation, together with a thumb to finger pattern of movement, is fundamental to more mature patterns of prehension (Gilfoyle et al., 1990). This grasp should not be underestimated in terms of its significance to the development of prehension because the inferior pincer grasp represents the beginning stage of opposition. The continued development of opposition helps enable the child to prehend small objects with increasingly greater precision and control. THREE JAW CHUCK(Duff, 1995; Exner, 2001)Alternative Grasp Name
DescriptionThis grasp is characterized by thumb opposition to the index and middle fingers. The object is held at the pads of the index and middle fingers, as well as the pad of the thumb. The IP joints of the index and middle fingers range from extended to slightly flexed, with flexion of the MCP joints. To oppose the digits, the thumb rotates and flexes toward the fingertips. The ulnar two digits do not participate in grasping the cube, but provide support to the radial side of the hand. A solid surface serves as a “leverage point for lifting the hand after it grasps the cube” (Halverson, 1931, p. 219).
AgeThis grasp is typically seen between 44 and 52 weeks or the 10th and 12th months of age. Developmental AdvancementThis grasp marks the beginning of the tripod posture, which is used for writing and many other tasks. The radial digits no longer flex around the object (Halverson, 1931); instead the pads of the fingers and thumb secure the object. Proprioceptive feedback from these digits enables the fingers and thumb to provide the appropriate pressure needed to secure the object. PINCER GRASP(Duff, 1995; Exner, 2001)Alternative Grasp Name
DescriptionThis grasp is characterized by the object being held between the opposed thumb and pad of the index or middle finger. The MCP and IP joints of the thumb are extended. The index finger is flexed at the MCP, slightly flexed at the PIP and extended at the DIP. The finger and thumb usually come together in the vertical plane (Castner, 1932) with the forearm in the midposition, offering the child increased visual regard. When grasping the object, the child rests only the fingertips on the tabletop for support.
AgeThis grasp is typically seen between 44 and 52 weeks or the 10th and 12th months of age. Developmental AdvancementMinimal external support is needed with the grasp. Hirschel, Pehoski, and Coryell (1990) state that with increased age children develop internal stability, which enables them to grasp with progressively less external support. The developmental progression of forearm position allows the child greater visual regard of the object, which assists in precision grasping. NEAT PINCER GRASP(Gesell & Amatruda, 1974; Ammon & Etzel, 1977; Newborg, Stock, Wnek, Guidubaldi, & Suinicki, 1984; Parks, 1988; Johnson-Martin et al., 1991; Provence et al., 1995)Alternative Grasp Name
DescriptionThis grasp is characterized by the object being held between the opposed thumb and the fingertip of the index or middle finger. All joints of the index or middle fingers are flexed. The longitudinal arch is aligning the phalanges and the MCP joint, which supports this position. The child no longer requires support from a solid surface. The forearm is in the midposition, enabling the child to visually guide the hand toward the object.
AgeThis grasp is typically seen between 44 and 52 weeks or the 10th and 12th months of age. Developmental AdvancementThe child no longer needs external support to successfully grasp an object, indicating continued development of internal stability. Greater control of finger flexion and extension also allows the child to bring the fingertip to the thumb for precision grasping. This ability to fractionate the flexion and extension of the IP joints of the fingers is essential for manipulation.
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