Point-mass biomechanical model of the upper extremity during Lofstrand crutch-assisted gait

AbstractAmong the infinite number of possible movements that can be produced, humans are commonly assumed to choose those that optimize criteria such as minimizing movement time, subject to certain movement constraints like signal-dependent and constant motor noise. While so far these assumptions have only been evaluated for simplified point-mass or planar models, we address the question of whether they can predict reaching movements in a full skeletal model of the human upper extremity. We learn a control policy using a motor babbling approach as implemented in reinforcement learning, using aimed movements of the tip of the right index finger towards randomly placed 3D targets of varying size. We use a state-of-the-art biomechanical model, which includes seven actuated degrees of freedom. To deal with the curse of dimensionality, we use a simplified second-order muscle model, acting at each degree of freedom instead of individual muscles. The results confirm that the assumptions of signal-dependent and constant motor noise, together with the objective of movement time minimization, are sufficient for a state-of-the-art skeletal model of the human upper extremity to reproduce complex phenomena of human movement, in particular Fitts’ Law and the $$\frac{2}{3}$$ 2 3 Power Law. This result supports the notion that control of the complex human biomechanical system can plausibly be determined by a set of simple assumptions and can easily be learned.

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Combining Values

Guides Newsletter ◽

10.1001/amaguidesnewsletters.2002.marapr01 ◽

2002 ◽

Vol 7 (2) ◽

pp. 1-4, 12 ◽

Cited By ~ 1

Author(s):

Christopher R. Brigham

Keyword(s):

Lower Extremity ◽

Upper Extremity ◽

Evaluation Method ◽

Proximal Phalanx ◽

Common Error ◽

The Third ◽

Whole Person ◽

Impairment Ratings ◽

Upper Extremity Impairment ◽

The Individual

Abstract To account for the effects of multiple impairments, evaluating physicians must provide a summary value that combines multiple impairments so the whole person impairment is equal to or less than the sum of all the individual impairment values. A common error is to add values that should be combined and typically results in an inflated rating. The Combined Values Chart in the AMA Guides to the Evaluation of Permanent Impairment, Fifth Edition, includes instructions that guide physicians about combining impairment ratings. For example, impairment values within a region generally are combined and converted to a whole person permanent impairment before combination with the results from other regions (exceptions include certain impairments of the spine and extremities). When they combine three or more values, physicians should select and combine the two lowest values; this value is combined with the third value to yield the total value. Upper extremity impairment ratings are combined based on the principle that a second and each succeeding impairment applies not to the whole unit (eg, whole finger) but only to the part that remains (eg, proximal phalanx). Physicians who combine lower extremity impairments usually use only one evaluation method, but, if more than one method is used, the physician should use the Combined Values Chart.

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Impairment Tutorial: Functionally Limiting Upper Extremity Pain: Controversies in Impairment Rating

Guides Newsletter ◽

10.1001/amaguidesnewsletters.2003.sepoct02 ◽

2003 ◽

Vol 8 (5) ◽

pp. 4-12

Author(s):

Lorne Direnfeld ◽

James Talmage ◽

Christopher Brigham

Keyword(s):

Upper Extremity ◽

Radicular Pain ◽

Illness Behavior ◽

Orthopedic Surgeon ◽

First Case ◽

Clinical Presentations ◽

Whole Person ◽

Physical Examinations ◽

Upper Extremity Impairment ◽

The Individual

Abstract This article was prompted by the submission of two challenging cases that exemplify the decision processes involved in using the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides). In both cases, the physical examinations were normal with no evidence of illness behavior, but, based on their histories and clinical presentations, the patients reported credible symptoms attributable to specific significant injuries. The dilemma for evaluators was whether to adhere to the AMA Guides, as written, or to attempt to rate impairment in these rare cases. In the first case, the evaluating neurologist used alternative approaches to define impairment based on the presence of thoracic outlet syndrome and upper extremity pain, as if there were a nerve injury. An orthopedic surgeon who evaluated the case did not base impairment on pain and used the upper extremity chapters in the AMA Guides. The impairment ratings determined using either the nervous system or upper extremity chapters of the AMA Guides resulted in almost the same rating (9% vs 8% upper extremity impairment), and either value converted to 5% whole person permanent impairment. In the second case, the neurologist evaluated the individual for neuropathic pain (9% WPI), and the orthopedic surgeon rated the patient as Diagnosis-related estimates Cervical Category II for nonverifiable radicular pain (5% to 8% WPI).

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Spinal Impairment Evaluation: Fifth Edition Changes

Guides Newsletter ◽

10.1001/amaguidesnewsletters.2001.janfeb01 ◽

2001 ◽

Vol 6 (1) ◽

pp. 1-3

Author(s):

Robert H. Haralson

Keyword(s):

Spinal Cord ◽

Lower Extremity ◽

Range Of Motion ◽

Upper Extremity ◽

Spinal Cord Injuries ◽

Clinical Findings ◽

Fourth Edition ◽

Treatment Results ◽

Standard Terminology ◽

Made In

Abstract The AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), Fifth Edition, was published in November 2000 and contains major changes from its predecessor. In the Fourth Edition, all musculoskeletal evaluation and rating was described in a single chapter. In the Fifth Edition, this information has been divided into three separate chapters: Upper Extremity (13), Lower Extremity (14), and Spine (15). This article discusses changes in the spine chapter. The Models for rating spinal impairment now are called Methods. The AMA Guides, Fifth Edition, has reverted to standard terminology for spinal regions in the Diagnosis-related estimates (DRE) Method, and both it and the Range of Motion (ROM) Method now reference cervical, thoracic, and lumbar. Also, the language requiring the use of the DRE, rather than the ROM Method has been strengthened. The biggest change in the DRE Method is that evaluation should include the treatment results. Unfortunately, the Fourth Edition's philosophy regarding when and how to rate impairment using the DRE Model led to a number of problems, including the same rating of all patients with radiculopathy despite some true differences in outcomes. The term differentiator was abandoned and replaced with clinical findings. Significant changes were made in evaluation of patients with spinal cord injuries, and evaluators should become familiar with these and other changes in the Fifth Edition.

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