ISB recommendation on definitions of joint coordinate systems of various joints for the reporting of human joint motion-Part II: shoulder, elbow, wrist and hand

Muscle fatigue is an exercise-induced reduction in maximal voluntary muscle force. It may arise not only because of peripheral changes at the level of the muscle, but also because the central nervous system fails to drive the motoneurons adequately. Evidence for “central” fatigue and the neural mechanisms underlying it are reviewed, together with its terminology and the methods used to reveal it. Much data suggest that voluntary activation of human motoneurons and muscle fibers is suboptimal and thus maximal voluntary force is commonly less than true maximal force. Hence, maximal voluntary strength can often be below true maximal muscle force. The technique of twitch interpolation has helped to reveal the changes in drive to motoneurons during fatigue. Voluntary activation usually diminishes during maximal voluntary isometric tasks, that is central fatigue develops, and motor unit firing rates decline. Transcranial magnetic stimulation over the motor cortex during fatiguing exercise has revealed focal cha...

Spinal and Supraspinal Factors in Human Muscle Fatigue

People with diabetes are more likely to be hospitalized and to have longer durations of hospital stay than those without diabetes. A recent survey estimated that 22% of all hospital inpatient days were incurred by people with diabetes and that hospital inpatient care accounted for half of the 174 billion USD total U.S. medical expenditures for this disease (1). These findings are due, in part, to the continued expansion of the worldwide epidemic of type 2 diabetes. In the U.S. alone, there are ∼1.6 million new cases of diabetes each year, with an over all prevalence of 23.6 million people (7.8% of the population, with one-fourth of the cases remaining undiagnosed). An additional 57 million American adults are at high risk for type 2 diabetes (2). Although the costs of illness-related stress hyperglycemia are not known, they are likely to be considerable in light of the poor prognosis of such patients (3–6).

There is substantial observational evidence linking hyperglycemia in hospitalized patients (with or without diabetes) to poor outcomes. Cohort studies as well as a few early randomized controlled trials (RCTs) have suggested that intensive treatment of hyperglycemia improved hospital outcomes (5–8). In 2004, this evidence led the American College of Endocrinology (ACE) and the American Association of Clinical Endocrinologists (AACE), in collaboration with the American Diabetes Association (ADA) and other medical organizations, to develop recommendations for treatment of inpatient hyperglycemia (9). In 2005, the ADA added recommendations for treatment of hyperglycemia in the hospitalto itsannual Standards of Medical Care (10). Recommendations from the ACE and the ADA generally endorsed tight glycemic control in critical care units. For patients in general medical and surgical units, where RCT evidence regarding treatment targets was lacking, glycemic goals similar to those advised for outpatients were advocated (9, …

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American Association of Clinical Endocrinologists and American Diabetes Association Consensus Statement on Inpatient Glycemic Control

Intra-articular fractures of the distal part of the radius in young adults comprise a distinct subgroup of fractures that are difficult to manage and are associated with a high frequency of post-traumatic arthritis. The effect of residual radiocarpal incongruity after this fracture has not been investigated previously. A retrospective study of forty-three fractures in forty young adults (mean age, 27.6 years) was done to determine the components that are critical to the outcome. Treatment included application of a cast alone in twenty-one fractures, insertion of pins and application of a plaster cast in seventeen, external fixation in two fractures, and open reduction and internal fixation in three fractures. At a mean follow-up of 6.7 years, 26 per cent were rated as excellent; 35 per cent, as good; 33 per cent, as fair; and 6 per cent, as poor. There was radiographic evidence of post-traumatic arthritis in twenty-eight (65 per cent) of the fractures. Accurate articular restoration was the most critical factor in achieving a successful result. Of the twenty-four fractures that healed with residual incongruity of the radiocarpal joint, arthritis was noted in 91 per cent, whereas of the nineteen fractures that healed with a congruous joint, arthritis developed in only 11 per cent. A depressed articular surface (a so-called die-punch fragment) was reduced anatomically by closed means in only 49 per cent and was responsible for residual incongruity in 75 per cent of the incongruous joints at late follow-up. Non-union of the ulnar styloid process adversely affected the results. Restoration and maintenance (extra-articular reduction) of the dorsal tilt and radial length did not prove critical except when severe radial shortening occurred.

Intra-articular fractures of the distal end of the radius in young adults.

Biomechanical models of the musculoskeletal system are frequently used to study neuromuscular control and simulate surgical procedures. To be broadly applicable, a model must be accessible to users, provide accurate representations of muscles and joints, and capture important interactions between joints. We have developed a model of the upper extremity that includes 15 degrees of freedom representing the shoulder, elbow, forearm, wrist, thumb, and index finger, and 50 muscle compartments crossing these joints. The kinematics of each joint and the force-generating parameters for each muscle were derived from experimental data. The model estimates the muscle-tendon lengths and moment arms for each of the muscles over a wide range of postures. Given a pattern of muscle activations, the model also estimates muscle forces and joint moments. The moment arms and maximum moment-generating capacity of each muscle group (e.g., elbow flexors) were compared to experimental data to assess the accuracy of the model. These comparisons showed that moment arms and joint moments estimated using the model captured important features of upper extremity geometry and mechanics. The model also revealed coupling between joints, such as increased passive finger flexion moment with wrist extension. The computer model is available to researchers at http://nmbl.stanford.edu.

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A model of the upper extremity for simulating musculoskeletal surgery and analyzing neuromuscular control

Patients with Colles' fractures have serious complications more frequently than is generally appreciated. A study of 565 fractures revealed 177 (31 per cent) with such complications as persistent neuropathies of the median, ulnar, or radial nerves (forty-five cases), radiocarpal or radio-ulnar arthrosis (thirty-seven cases), and malposition-malunion (thirty cases). Other complications included tendon ruptures (seven), unrecognized associated injuries (twelve), Volkmann's ischemia (four cases), finger stiffness (nine cases), and shoulder-hand syndrome (twenty cases). In many patients, incomplete restoration of radial length or secondary loss of the reduction position caused the complications.

Complications of Colles' fractures.

S-shaped force transducers were developed for measurement of the forces along intact tendons. After calibration, the transducers were applied to the flexor pollicis longus and flexor digitorum superficialis and profundus tendons of the index finger in five patients operated on for treatment of carpal tunnel syndrome. The tendon forces generated during passive and active motion of the wrist and fingers were recorded. For pinch function, the amount of the applied load was measured with a special pinch meter. Tendon forces in the range of 0.1 to 0.6 kgf were measured during passive mobilization of the wrist. Tendon forces up to 0.9 kgf were present during passive mobilization of the fingers. Tendon forces up to 3.5 kgf were present during active unresisted finger motion. Tendon forces up to 12.0 kgf were recorded during tip pinch, with a mean applied pinch force of 3.5 kgf. These results have potential application in determining the amount of force that a tendon repair would have to resist during passive as well as active postsurgical mobilizations.

Flexor tendon forces: In vivo measurements

The results in sixteen patients who had a displaced, comminuted intra-articular fracture of the distal end of the radius and who were treated by open reduction and internal fixation were retrospectively reviewed. At a mean follow-up of 4.8 years, 81 per cent of the patients had a rating of good or excellent by the scoring system of Gartland and Werley, but only 56 per cent had such a rating when the modified scoring system of Green and O'Brien was used. All of the fractures healed at an average of nine weeks. A step-off of two millimeters or more in the distal radial articular surface at the time of healing was important, because the four patients in whom the fracture healed with this amount of incongruity all had post-traumatic arthritis at follow-up, compared with only three of twelve in whom the incongruity was less than two millimeters.

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Open reduction and internal fixation of displaced, comminuted intra-articular fractures of the distal end of the radius.

We have examined 40 normal subjects (20 men and 20 women) to determine the ideal range of motion required to perform activities of daily living. The amount of wrist flexion and extension, as well as radial and ulnar deviation, was measured simultaneously by means of a biaxial wrist electrogoniometer. The entire battery of evaluated tasks could be achieved with 60 degrees of extension, 54 degrees of flexion, 40 degrees of ulnar deviation, and 17 degrees of radial deviation, which reflects the maximum wrist motion required for daily activities. The majority of the hand placement and range of motion tasks that were studied in this project could be accomplished with 70 percent of the maximal range of wrist motion. This converts to 40 degrees each of wrist flexion and extension, and 40 degrees of combined radial-ulnar deviation. This study provides normal standards for the functional range of motion of the wrist.

Functional ranges of motion of the wrist joint

A series of 166 perilunate dislocations and fracture-dislocations from 7 centers was retrospectively studied. The diagnosis was missed initially in 41 cases (25%). A classification system was presented. The perilunate fracture-dislocations were more frequent than the perilunate dislocations at a ratio of two to one. The displacement was dorsal in 161 cases (97%) and palmar in only 5 (3%). The dorsal transscaphoid perilunate fracture-dislocations represented 96% of the dorsal perilunate fracture-dislocations and 61% of the whole series. The clinical and radiologic outcome of 115 perilunate dislocations and fracture-dislocations with at least 1 year and an average of 6 years 3 months of follow-up was studied. Open injury and delay of treatment had an adverse effect on clinical results, whereas anatomical type had less influence. In cases treated early, the clinical results were satisfactory but the incidence of post-traumatic arthritis was high (56%). In the dorsal perilunate dislocation group of pure ligamentous injuries and in the dorsal transscaphoid group, the best radiologic results were observed after open reduction and internal fixation. In the latter group, the fixation of the scaphoid alone was not always sufficient and left occasionally scapholunate dissociation, lunotriquetral dissociation, ulnar translation of the carpus, or other carpal collapse patterns. The initial appraisal of both the osseous and ligamentous pathology was very important.

William P. Cooney

Papers

Complications of Colles' fractures.

Flexor tendon forces: In vivo measurements

Open reduction and internal fixation of displaced, comminuted intra-articular fractures of the distal end of the radius.

Functional ranges of motion of the wrist joint

Perilunate dislocations and fracture-dislocations: A multicenter study