KINEMATICS IN OCCUPATIONAL THERAPY 1

Kinematics is the geometry, pattern, or form of motion with respect to time. Kinematics, which describes the appearance of motion, is distinguished from kinetics, the forces associated with motion. Linear kinematics involves the shape, form, pattern, and sequencing of linear movement through time, without particular reference to the forces that cause or result from the motion. Careful kinematic analyses of performance are invaluable for occupational therapy practice. When people learn a new motor skill, a progressive modification of movement kinematics reflects the learning process. This is particularly true for young children, whose movement kinematics changes with the normal changes in anthropometry and neuromuscular coordination that accompany growth. Likewise, when a patient rehabilitates an injured joint, the occupational therapist or clinician looks for the gradual return of normal joint kinematics. Understanding movement is crucial to effectively helping individuals with movement difficulties. If we do not understand some of the characteristics of movement, it is hard to explore the problems that movement difficulties create. When an occupational therapist works with an individual who has difficulty with movements, the therapist needs to understand the characteristics of the movements and how these actions impact occupations. (Sandi J. Spaulding 2005)

One specific performance areas in occupation that I chose for basic activities of daily living are functional mobility. Functional mobility is a movement from one position or place to another (during performance of everyday activities), such as in-bed mobility, wheelchair mobility, and transfers. For example wheelchair, bed, car, tub, toilet, tub/shower, chair, floor ). It also includes functional ambulation and transporting objects. (Susan J. Hall 2012) Kinematic models of the human body are those that represent its mobility and neglect all other aspects (for example is the mass distribution). The models are classified as anthropomorphic, also called skeletal, or functional. Skeletal models visually resemble the construction of the human body; the body segments are (typically) modelled as solid links and the human joints as the joints of the model. In functional models, the body segments are modelled as nodes of a graph (of a tree) and the joints as arcs connecting the nodes. The model represented in figure below consists maximally of 18 rigid segments and 17 joints and possesses 41 Degree of Freedom.

Kinematic model of human body. Filled circles designate the joints that are usually included in the model. Open circles are for the joints that are included only in some models.

To estimate the total mobility of the body all joints and body segments must be considered. According to estimations, there are 148 movable bones and 147 joints in the human body.  The total mobility can be estimated using a slightly modified Gruebler's formula, in which classes of joints instead of the number of DOF are used:

Where F is the mobility of the body (the total number of DOF), N is the number of movable bones, i is the class of the joint (based on the number of imposed constraints, i = 6 - f, where f is the number of DOF), and j, is the number of joints of the class i. It has been estimated that the human body has 148 movable bones connected by the joints, 29 joints of the 3rd class (with three DOF), 33 joints of the 4th class (with two DOF), and 85 joints of the 5th class (with one DOF). The total mobility of the human body is

F = (6.148) - (4.33) - (5.85) = 888 - 87 - 132 - 425 = 244

Thus the human skeletal system is highly redundant. It has 244 DOF and its manoeuvrability is 238. To position an end effector in space, the brain must specify not 6 but 244 variables, of which 238 are redundant and may be used to perform the motor task in an optimal way.  (Zaciorskij Vladimir M 1998) Knowledge of kinematics is important in Occupational Therapy practice. The therapist will able to improve their practice techniques when working with the patient. This is because the therapist will more readily see movement substitution (an awkward movement that occurs sometimes because the needed muscle force is absent). Besides that, the therapist will be able to document movement speed changes and other aspects of movement so they can better observe and document changes as treatment progresses. Furthermore, one can understand the implications of adapting and accommodating movements more efficiently. (Sandi J. Spaulding 2005) Understanding the kinematics of human movement is of both a basic and an applied value in medicine and biology. Motion measurement can be used to evaluate functional performance of limbs under normal and abnormal conditions. Kinematic knowledge is also essential for proper diagnosis and surgical treatment of joint disease and the design of prosthetic devices to restore function.

One clinical case study that can be use is patient with Osteoarthritis namely as Sandy, female, 62 years old. She has good health state, suffered with osteoarthritis for 3 years, this accompanied by varicose vein and thrombosis. She does not taking any medication. In past was taking anti-inflammatory. Previously, she complains pain in the left knee affecting walking ability preventing to go up or down stairs. She has difficulty in walking down stairs. Alteration of joint movement in a hand, the normal transmission of force requires that the joint axis stays in its relationship to both bones at the joint and the joint glides in a normal pattern. In case of Sandy, there is an alteration of pattern of movement around an axis. The axis may change considerably when the joint no longer glides or when the joint subluxates or collapses.  In severe derangement of the joint surface as in intra-articular fracture or in dislocated or collapsed joint, the axis of the joint surface is lost altogether. An example is excisional arthroplasty where the joint no longer moves about the axes of rotation. The type and the range of motion are entirely different from those of a normal joint. This pattern of motion is a poor compensation and is only useful in limited situations where the adjacent joints can compensate. An example is the excisional arthroplasty for osteoarthritis (OA) of the base of thumb, where the aim of surgery is to relieve pain and retains stability at the basal joint, motion being provided by the distal MCP joint and IP joints. However, introducing a fibrous joint on a basal finger or a thumb joint, one changes the way the joint moves, the joint mechanics and the moment arm of all the muscles at that joint. This invariably leads to an imbalance in the distal joints as seen with thumb MCP joint hyperextension with silastic or excisional arthroplasty of the CMC joint. There is nothing wrong with the MCP joint itself, but the altered mechanics of the basal joints leads to a change in forces of the muscles on the distal joints, deformity, pain and eventually OA (Brand). (Santosh Rath 2011)

Robert J. Beichner on 1996 explained the impact of video motion analysis on kinematics graph interpretation skills. Video motion analysis software was used by introductory physics students in a variety of instructional settings. 368 high school and college students took part in a study where the effect of graduated variations in the use of a video analysis tool was examined. Post‐instruction assessment of student ability to interpret kinematics graphs indicates that groups using the tool generally performed better than students taught via traditional instruction. The data further establishes that the greater the integration of video analysis into the kinematics curriculum, the larger the educational impact. An additional comparison showed that graph interpretation skills were significantly better when a few traditional labs were simply replaced with video analysis experiments. Hands‐on involvement appeared to play a critical role. Limiting student experience with the video analysis technique to a single teacher‐led demonstration resulted in no improvement in performance relative to traditional instruction. Offering more extensive demonstrations and carrying them out over an extended period of time proved somewhat effective. The greatest impact came from a combination of demonstrations with hands‐on labs. (Robert J. Beichner 1996)

In a nut shell, the therapist will able to improve their practice techniques when working with the patient. A progressive modification of movement kinematics reflects the learning process. The therapist will be able to document movement speed changes and other aspects of movement so they can better observe and document changes as treatment progresses. It is basically apply to prevent injury and improve rehabilitation in terms of technique analysis and exercise given to the client.

 

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