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At least 235 records · Page 13Linked to original sources
PubMed1993

[The signification of total elbow replacement in the treatment of rheumatoid arthritis].

The purpose of this paper is to emphasis the signification of total elbow replacement in the treatment of rheumatoid arthritis. Total elbow replacement were performed in twenty elbows in fourteen patients who had rheumatoid arthritis from 1982 to 1990. The follow-up period ranged from 2 to 9 years. Pain relief was complete in twelve patients. Preoperation flexion averaged 119 degrees, increasing to 127 degrees. Preoperation extension averaged -34 degrees, increasing to -24 degrees postoperation. There were no infection and fracture postoperatively. Radiolucent lines were seen in four humeral components, in one ulnar component. Proximal subsidence of the humeral component were found in two elbows. Posterior dislocation occurred in three elbows. In two cases, reduction was successful by three weeks immobilization in a plaster cast with the elbow in the flexion position. Transient ulnar nerve palsy was evident in two elbows. Revision surgeries were performed in two cases, which occurred dislocation and progressive subsidence. Multiple replacements of major joints were performed in ten patients. Two joints were replaced in two patients, three joints were replaced in six patients, four joints were replaced in two patients. Four total elbow replacements were performed accompanied with other joints replacement in the same anesthesia. We recommended two joint replacements in the same anesthesia in patient with good general condition. All patients had functional improvements after total elbow replacement, especially reaching of the arm. Four patients improved the walking by being able to use stich after total elbow replacement.

Activities of Daily Living↗
PubMed1998

The column procedure: a limited lateral approach for extrinsic contracture of the elbow.

Thirty-eight elbows (thirty-seven patients) with an extrinsic contracture were treated operatively with a limited lateral approach to the anterior and posterior aspects of the capsule. Because the procedure elevates muscles from the anterior and posterior aspects of the lateral supracondylar osseous ridge, we called it the column procedure. The mean preoperative arc of flexion was 49 degrees (from 52 to 101 degrees). At a mean of forty-three months (range, twenty-four to seventy-four months) postoperatively, the mean arc of flexion was 94 degrees (from 27 to 121 degrees). The mean total gain in the arc of flexion-extension was 45 degrees; thirty-four elbows (89 percent) had an improved range of motion at the latest follow-up examination. Overall, thirty-one elbows (82 percent) had a satisfactory result. Greater improvement was obtained in elbows that had had severe stiffness (a total arc of 31 to 60 degrees) or very severe stiffness (a total arc of 30 degrees or less) or that had had a combined flexion and extension contracture. A complication occurred in four elbows (11 percent). A hematoma developed in two elbows and impaired the final outcome in one of them. Two elbows had transient ulnar paresthesia, which resolved spontaneously. The arc of flexion obtained at the time of the operation was lost in ten elbows (26 percent) after an initial period of improvement; at the latest follow-up evaluation, four of these elbows had a mean decrease in the arc of flexion of 24 degrees compared with preoperatively. The column procedure is associated with a low rate of complications and is safe and effective for the treatment of a limitation in flexion or extension resulting from an extrinsic contracture of the elbow.

Adolescent↗
PubMedDate not supplied

Semiconstrained total elbow arthroplasty.

Diminution of elbow function may be both embarrassing and severely disabling, especially in patients with multiple arthritic joints. Over the past century, multiple techniques of soft tissue reconstruction of the elbow have been advocated. In general, they do not compare well with total elbow arthroplasty. Arthrolysis has often resulted in little improvement of elbow motion and interposition arthroplasty to instability. Synovectomy may however offer satisfactory relief of disability for the rheumatoid elbow provided that initially there is little evidence of joint destruction. The major problem with rigidly linked total elbow arthroplasty has been a high incidence of prosthetic loosening. Biomechanical analysis has shown that high moments tend to disrupt the osseousmethacrylate junction in the humoral medulary canal. Development of a semi-constrained total elbow prosthesis transfers the developed stress to the collateral soft tissues and reduces prosthetic loosening to approximately 3 per cent. This is about one-tenth of the incidence of loosening of the hinge type arthroplasty. This reduction in prosthetic loosening has been coupled with excellent gains in flexion and estension. However, improvement in forearm rotation has not been predictable, especially in elbows exhibiting preoperative fusion or fibrous ankylosis. Though the semi-counstrained total elbow has only been generally available for 3 years, a review of these results justifies its continued use for elbow reconstruction.

Arthritis, Rheumatoid↗
PubMed1999

Osseous manifestations of 'handball goalie's elbow'.

The radiographic manifestations of musculoskeletal stress at the elbow associated with European team handball are reported in 46 amateur handball players with 74 elbows injured by blocking shots. All the 92 elbows were evaluated by clinical and radiological examinations using the 18 asymptotic elbows as a control. Lateral and anterioposterior radiographs were obtained of both elbows in addition to stress radiographs with manual valgus force. The mean age of the athletes was 23.0 (range 16-44) years. The players had an athletic experience of 11.6 years (range 3.5-34). Their elbow pain had at inclusion lasted for 43 +/- 42) (range 2-252) months. Their symptoms were located in all four parts of the elbow and in different combinations: anterior (6), posterior (23), medial (38), lateral (17), and in the whole elbow (3). No major bony lesions were found. Minor abnormalities were observed (21%), including loose bodies (7), traction spur formation (1), and minor arthritic changes (7) in addition to medial instability (12). Manual instability stress test was not useful and should be performed with a stress device. 'Handball goalie's elbow' does not lead to major osseous manifestations.

Adolescent↗
PubMed2006

Impact of sedation method on the diagnosis of hip and elbow dysplasia in Swedish dogs.

Our objective was to investigate the effect of sedation method on the screening result for hip and elbow dysplasia. The study was based on a questionnaire survey of routines for hip and elbow screening at Swedish veterinary clinics and results of hip and elbow status, for eight breeds (Bernese Mountain Dog, Boxer, German Shepherd Dog, Golden Retriever, Labrador Retriever, Newfoundland, Rottweiler, and Saint Bernard) recorded by the Swedish Kennel Club. In total 5877 and 5406 dogs examined for hip and elbow dysplasia, respectively, from January 2002 through March 2003 were included. We used logistic regression to examine whether the type of chemical restraint used for sedation affected the screening result for hip and elbow dysplasia. In addition to sedation method, the effects of veterinary clinic, sex, breed, and age at screening were studied. The type of chemical restraint used for sedation affected the screening result for hip but not for elbow dysplasia. Acepromazine gave less than half the odds of hip dysplasia compared with medetomidine and butorphanol (the most common method), medetomidine alone or xylazine. Females had about 25% higher odds for developing hip dysplasia whereas males had almost 40% higher odds for developing elbow dysplasia. Saint Bernard, Newfoundland and German Shepherd Dog had the highest odds of developing hip dysplasia, whereas Rottweiler and Labrador Retriever had the lowest odds. Boxer had the lowest risk for elbow dysplasia, followed by Labrador Retriever. Saint Bernard and Rottweiler had the highest odds of elbow dysplasia. Increasing age increased the odds of both hip and elbow dysplasia, by about 2.5% per month. Following the results in this study, recording of the type of chemical restraint used for sedation during hip screening has now become mandatory in Sweden. This makes it possible to account for the effect of sedation method in a model for prediction of breeding values for hip dysplasia.

Acepromazine↗
PubMed1991

Activity of wrist muscles elicited during imposed or voluntary movements about the elbow joint.

To examine the coordination of muscles during multijoint movement, we compared the response of wrist muscles to perturbations about the elbow joint with their activation during a volitional elbow movement. The purpose was to test the following two predictions: (a) Responses can occur in muscles not stretched by the perturbation, as has been reported for other multijoint systems; and (b) the motor pattern in response to a perturbation mimics an opposing volitional motor pattern across the two joints. We recorded the electromyographic (EMG) activity of elbow and wrist muscles as well as the flexion/extension motions at the elbow and wrist joints during individual trials that either involved a response to a torque perturbation that extended the elbow or required volitional elbow flexion. The results of this study confirmed that responses were elicited in the nonstretched wrist muscles when the elbow joint was perturbed. The same motor sequence of elbow and wrist flexors was present for both the volitional and perturbation task (with the forearm supinated), regardless of whether the wrist joint was immobilized or freely moving. The findings suggest that the nervous system relies on the purposeful coupling of elbow and wrist flexors to counter the inertial effects during the unrestricted voluntary movement, even though the coupling does not appear to be purposeful during the perturbation or with the wrist immobilized. The coupling of elbow and wrist flexors, however, was not rigidly fixed, as evidenced by muscle onsets that adapted over repeated perturbation trials and a reversal of the wrist muscle activated (wrist extensor) when the forearm was pronated. Hence, the coupling of muscle activities can be modified quantitatively when not beneficial and can be altered qualitatively with different initial configurations of the arm.

Journal Article↗
PubMed2006

Expression of Dlx5 and Dlx6 during specification of the elbow joint.

The onset of elbow joint formation in the developing limb is characterized morphologically by the conversion of differentiated chondrocytes at the site of incipient joint formation into the densely packed flattened cells of the joint interzone. However, experimental studies have indicated that the elbow joint is specified well before joint interzone formation by a distinctive population of precursor cells located at the site in the developing limb bud at which the elbow joint will subsequently form. Here we show that during specification of the elbow joint in the chick limb bud, the homeodomain transcription factors Dlx5 and Dlx6 are highly expressed by a discrete group of cells that encompass the prospective elbow joint. The Dlx5- and Dlx6-expressing cells at the prospective elbow joint are located where the differentiating humerus branches into the radius and ulna. Thus, Dlx5 and Dlx6 are the earliest molecular markers of the presumptive elbow joint yet described. The onset of Dlx5 expression in the region of the presumptive elbow joint is shortly followed by the initiation of expression amongst the Dlx5-expressing cells of Gdf5, which encodes a secreted signaling molecule that is involved in regulating the onset of joint formation. These results suggest that Dlx genes may be involved in specification of the elbow joint and/or in providing positional information that specifies the site at which the elbow joint will form.

Animals↗
PubMed1996

Relationship between physical signs of elbow dysplasia and radiographic score in growing Rottweilers.

OBJECTIVE: To examine the relationship between physical signs of elbow dysplasia and radiographic appearance of the elbow joints in growing dogs. DESIGN: Prospective study. ANIMALS: 55 Rottweiler pups. PROCEDURE: Owners of clinically normal Rottweiler pups were contacted through breed clubs in 3 Australian states and asked to participate in the study. All those offering to participate were included. PROCEDURE: The first physical examination was performed when pups were 3 months old and included a lameness evaluation and palpation of the elbow joints. Physical examinations were repeated when pups were 5, 6, 9, and 12 months old. Radiographs of the elbows were obtained at 6 and 12 months. Relationships among lameness, decreased range of movement, signs of pain, and radiographic data related to elbow dysplasia were examined. RESULTS: Elbow dysplasia caused clinical lameness in only 3 dogs but 57% of dogs developed radiographic signs of elbow dysplasia by 12 months of age. A grade-2 radiographic score at 12 months of age was significantly associated with clinical elbow dysplasia. CLINICAL IMPLICATIONS: Elbow dysplasia has a prevalence of > 50% in certain breed populations. This study supports radiographic screening at 12 months of age, accompanied by physical examination to detect clinical elbow dysplasia.

Age Factors↗
PubMed2004

[Total elbow joint allograft for long term posttraumatic osteoarticular loss. Follow-up results at twelve years].

PURPOSE OF THE STUDY: Elbow joint allograft (EJA) involving the entire joint (distal humerus, proximal radius and ulna, capsuloligament structures) is a salvage technique proposed in massive bone loss, particularly in young subjects where total elbow prosthesis is contraindicated. We report our experience with seven patients, analyzing the long-term clinical and radiological outcome. MATERIAL AND METHODS: This retrospective study included seven patients, mean age 42 years (21-70). All had experienced severe elbow trauma. Two patients had associated neuromuscular or vascular lesions. All patients underwent at least one surgical procedure on the affected elbow. The preoperative status of the skin cover was crucial. Both longitudinal and circumferential retraction were observed. We used preoperative skin expansion in one patient and a pediculated musculocutaneous latissimus dorsi flap in one other. A posterior and median approach was used conserving tricipital continuity. The ulnar nerve was transposed anteriorly. The allograft was prepared, carefully preserving the capsule and ligaments. Adaptation required cutting the extremities of the humerus and radius and total resection of the radial head except in one patient. Stable plate fixation was completed by an iliac cancellous graft screwed to the humerus and the ulna. The Morrey score was used to assess clinical outcome. The Larsen and Allieu classifications were used to assess radiological outcome. RESULTS: There was one early failure requiring revision for arthrodesis. Assessment of long-term outcome concerned six patients. Mean follow-up was 12 years (7-15 years). The Morrey score improved in six patients and five of them were satisfied. None of the patients complained of invalidating pain and elbow motion was not functional in only one (- 30 degrees - 100 degrees ). For all patients except one, instability was proportional to the duration of the graft and worsened with time. For five out of six patients, significant radiological degradation of the elbow joint was associated with bone lysis which increased with time. DISCUSSION: The allograft acts like a spacer and does not transmit pain impulses. The absence of the pain signal leads to overuse of the grafted joint and osteoarticular destruction. Despite radiological degradation, this procedure provides satisfactory and painless elbow function in most patients. The clinical and radiological features do not follow the same pattern. But we did not have any cases of disassembly or nonunion. Preoperative planning and plastic surgery have enabled us to control the cutaneous portal. We did not have any postoperative infections. Joint allograft is a salvage solution for major osteoarticular loss in young patients desiring conserved joint function and for whom a total elbow prosthesis is contraindicated. It restores bone stock, enables mid-term potential for joint function, and does not compromise surgical revision. CONCLUSION: It remains an exceptional indication which is technically difficult. Resorption of the allograft is constant at long term. Clinically, instability worsen functional outcome. The future for this technique depends on progress in immunology and cryobiology. At the present time, composite total elbow prostheses with an allograft combine the advantages of restored bone stock and arthroplasty.

Adult↗
PubMed1996

Range of motion and complications after postburn heterotopic bone excision about the elbow.

OBJECTIVE: To review the results of surgical management of heterotopic ossification about the elbow in burned patients. DESIGN: Retrospective analysis with long-term patient follow-up. MATERIALS AND METHODS: Eleven patients with 16 elbows requiring surgery were admitted between January 1, 1982 and December 31, 1993. A posterior approach to the elbow with release of the encased ulnar nerve +/- anterior transposition and transolecranon osteotomy to access extensive bone formation in the olecranon fossa was employed. Eight patients (11 elbows) were available for long-term follow-up conducted at mean 50 +/- 13 months after surgery. Long-term follow-up consisted of measurement of range of elbow motion, as well as clinical assessment of ulnar nerve function. MAIN RESULTS: For the 11 elbows examined postoperatively, the mean range of motion preoperatively in flexion-extension was 11 degrees +/- 5 degrees compared to 89 degrees +/- 12 degrees postoperatively (p < 0.001). Three patients with poor long-term results had ankylosis of the joint preoperatively. Of four patients with ulnar nerve paresis preoperatively, none had ulnar nerve dysfunction at follow-up. Of 16 elbows operated on, four (25%) had postoperative complications. Two suffered soft-tissue breakdown with hardware exposure requiring abdominal flap closure, one early failure of olecranon fixation, and one late infected hardware. CONCLUSIONS: Surgery for both limited range of motion as well as ulnar nerve compression is effective in cases of heterotopic ossification about the elbows of burned patients. Early operative intervention is indicated in progressive disease, particularly ulnar nerve palsy, if soft-tissue quality is adequate. Complications with 25% of elbows suggest that use of olecranon osteotomy for joint access may warrant review.

Adult↗
PubMed2005

Complex pediatric elbow injury: an uncommon case.

BACKGROUND: There is paucity of literature describing complex elbow trauma in the pediatric population. We described a case of an uncommon pediatric elbow injury comprised of lateral condyle fracture associated with posterolateral dislocation of elbow. CASE PRESENTATION: A 12-year-old boy sustained a direct elbow trauma and presented with Milch type II lateral condyle fracture associated with posterolateral dislocation of elbow. Elbow dislocation was managed by closed reduction. The elbow stability was assessed under general anaesthesia, followed by open K-wiring for the lateral condylar fracture fixation. The patient had an uneventful recovery with an excellent outcome at 39 months follow-up. CONCLUSION: Complex pediatric elbow injuries are quite unusual to encounter, the management of such fractures can be technically demanding. Concomitant elbow dislocation should be managed by closed reduction followed by open reduction and internal fixation (K-wires or cannulated screws) of the lateral condyle fracture.

Bone Wires↗
PubMed1997

Total elbow arthroplasty as primary treatment for distal humeral fractures in elderly patients.

We retrospectively reviewed the results of primary total elbow arthroplasty for the treatment of an acute fracture of the distal aspect of the humerus in twenty consecutive patients (twenty-one elbows) who had a mean age of seventy-two years (range, forty-eight to ninety-two years) at the time of the injury. The patients were managed between November 1982 and October 1992. The presence of rheumatoid arthritis in nine patients (ten elbows) influenced the choice of treatment. The mean interval between the injury and the total elbow arthroplasty was seven days (range, one to twenty-five days). The mean duration of postoperative hospitalization was seven days (range, four to thirteen days). The mean duration of follow-up was 3.3 years (range, three months to 10.5 years). All patients were followed for a minimum of two years or until the time of death; the duration of follow-up was less than two years for three patients who died. None of the patients were lost to follow-up. Twenty implants were intact at the latest follow-up examination. One patient had a revision total elbow arthroplasty twenty months after the index procedure because of a fracture of the ulnar component sustained in a fall on the outstretched arm. On the basis of the Mayo elbow performance score, fifteen elbows had an excellent result and five had a good result; there were inadequate data for one elbow. There were no fair or poor results. The mean arc of flexion was 25 to 130 degrees. There was no evidence of loosening on the radiographs. Postoperative complications included fracture of the ulnar component in one patient, ulnar neurapraxia in three, and reflex sympathetic dystrophy in one. The results suggest that total elbow arthroplasty can be an alternative form of treatment of a severely comminuted fracture of the distal aspect of the humerus in older patients even in the presence of rheumatoid arthritis. This procedure is not an alternative to osteosynthesis in younger patients.

Accidental Falls↗
PubMed2004

Standard surgical protocol to treat elbow dislocations with radial head and coronoid fractures.

BACKGROUND: The results of elbow dislocations with associated radial head and coronoid fractures are often poor because of recurrent instability and stiffness from prolonged immobilization. We managed these injuries with a standard surgical protocol, postulating that early intervention, stable fixation, and repair would provide sufficient stability to allow motion at seven to ten days postoperatively and enhance functional outcome. METHODS: We retrospectively reviewed the results of this treatment performed, at two university-affiliated teaching hospitals, in thirty-six consecutive patients (thirty-six elbows) with an elbow dislocation and an associated fracture of both the radial head and the coronoid process. Our surgical protocol included fixation or replacement of the radial head, fixation of the coronoid fracture if possible, repair of associated capsular and lateral ligamentous injuries, and in selected cases repair of the medial collateral ligament and/or adjuvant hinged external fixation. Patients were evaluated both radiographically and with a clinical examination at the time of the latest follow-up. RESULTS: At a mean of thirty-four months postoperatively, the flexion-extension arc of the elbow averaged 112 degrees +/- 11 degrees and forearm rotation averaged 136 degrees +/- 16 degrees. The mean Mayo Elbow Performance Score was 88 points (range, 45 to 100 points), which corresponded to fifteen excellent results, thirteen good results, seven fair results, and one poor result. Concentric stability was restored to thirty-four elbows. Eight patients had complications requiring a reoperation: two had a synostosis; one, recurrent instability; four, hardware removal and elbow release; and one, a wound infection. CONCLUSIONS: Use of our surgical protocol for elbow dislocations with associated radial head and coronoid fractures restored sufficient elbow stability to allow early motion postoperatively, enhancing the functional outcome. We recommend early operative repair with a standard protocol for these injuries.

Adult↗
PubMed2005

Standard surgical protocol to treat elbow dislocations with radial head and coronoid fractures. Surgical technique.

BACKGROUND: The results of elbow dislocations with associated radial head and coronoid fractures are often poor because of recurrent instability and stiffness from prolonged immobilization. We managed these injuries with a standard surgical protocol, postulating that early intervention, stable fixation, and repair would provide sufficient stability to allow motion at seven to ten days postoperatively and enhance functional outcome. METHODS: We retrospectively reviewed the results of this treatment performed, at two university-affiliated teaching hospitals, in thirty-six consecutive patients (thirty-six elbows) with an elbow dislocation and an associated fracture of both the radial head and the coronoid process. Our surgical protocol included fixation or replacement of the radial head, fixation of the coronoid fracture if possible, repair of associated capsular and lateral ligamentous injuries, and in selected cases repair of the medial collateral ligament and/or adjuvant-hinged external fixation. Patients were evaluated both radiographically and with a clinical examination at the time of the latest follow-up. RESULTS: At a mean of thirty-four months postoperatively, the flexion-extension arc of the elbow averaged 112 degrees +/- 11 degrees and forearm rotation averaged 136 degrees +/- 16 degrees . The mean Mayo Elbow Performance Score was 88 points (range, 45 to 100 points), which corresponded to fifteen excellent results, thirteen good results, seven fair results, and one poor result. Concentric stability was restored to thirty-four elbows. Eight patients had complications requiring a reoperation: two had a synostosis; one, recurrent instability; four, hardware removal and elbow release; and one, a wound infection. CONCLUSIONS: Use of our surgical protocol for elbow dislocations with associated radial head and coronoid fractures restored sufficient elbow stability to allow early motion postoperatively, enhancing the functional outcome. We recommend early operative repair with a standard protocol for these injuries.

Collateral Ligaments↗
PubMed2003

The objective diagnosis of early tennis elbow by magnetic resonance imaging.

OBJECTIVE: To identify the salient magnetic resonance imaging (MRI) features of tennis elbow. An objective diagnosis is important when managing work-related incapacity due to ill-defined lateral arm pain. METHOD: Twenty-three symptomatic and 17 asymptomatic elbows in 20 patients with tennis elbow, no evidence of other pathology and no previous treatment were imaged using established MRI sequences. RESULTS: In the symptomatic elbows, the common extensor origin (CEO) showed signs of oedema in 23, thickening in 19, peri-tendon oedema in 3 and tears in 13 cases. More extensive abnormalities were demonstrated in only two elbows. Six out of 17 asymptomatic elbows also showed oedema in the CEO. CONCLUSIONS: The CEO is confirmed as the primary site of MRI changes in tennis elbow. Oedema was commonly found in asymptomatic elbows, necessitating the presence of thickening or tears in the CEO tendon to objectively diagnose tennis elbow on MRI.

Adult↗
PubMed1993

Elbow joint disorders in relation to vibration exposure and age in stone quarry workers.

Elbow joint disorders were studied in relation to vibration exposure and age in 74 male stone quarry workers who operated mainly chipping hammers and sometimes rock drills. They were examined for range of active motion in elbow extension and flexion, and by means of radiographs of the elbow joint. Effects of age and vibratory tool operation on the elbow joint were statistically estimated using multiple regression analysis. In the analysis of all subjects, including those aged over 60 years, age was significantly related to the range of motion in extension and to radiographic changes in both elbows, and the duration of vibratory tool operation was associated with the range of right elbow flexion. Among subjects under the age of 60 years, duration of vibratory tool operation showed a significant dose-effect relationship to the range of flexion and radiographic changes in the right elbow, but there was no significant relationship with age. The present results suggest that the operation of chipping hammers and rock drills contributes to elbow joint disorders or osteoarthrosis, even when the effect of age is taken into account. Besides vibration exposure, it may be necessary to consider various loads on the elbow joint such as firmly grasping and pressing the tool against stones with the arm bent at about 90 degrees, and carrying stones.

Adult↗
PubMed1999

Finger opening in an overarm throw is not triggered by proprioceptive feedback from elbow extension or wrist flexion.

Accuracy in an overarm throw requires great precision in the timing of finger opening. We tested the hypothesis that finger opening in an overarm throw is triggered by proprioceptive feedback from elbow extension or wrist flexion. The hypothesis was tested in two ways: first, by unexpectedly perturbing elbow extension or slowing wrist flexion and determining whether changes occurred in finger opening, and second, by measuring the latency from the start of these joint rotations to the start of finger opening. Subjects threw balls fast and accurately from a sitting or standing position while joint rotations were recorded with the search-coil technique. Elbow extension was unexpectedly blocked near the start of forward motion of the hand by a rope attached to the wrist that passed through a catch mechanism located behind the subject. In spite of a slowing or complete block of elbow extension, and in some cases a replacement of elbow extension by elbow flexion, finger opening always occurred and at the same latency as for normal throws. Wrist flexion was slowed in seven of eight subjects when subjects changed from throwing with a light ball (14 g, 70 mm diam.) to a heavy ball (210 g, 65 mm diam.). For the first throw with the heavy ball, this slowing was neither fully anticipated by the subject nor compensated for by the changed proprioceptive feedback associated with the slowing. Consequently, the timing of finger opening was unchanged and (to the surprise of the thrower) the ball went high. Furthermore, in unperturbed throws with tennis balls, the latency from onset of wrist flexion or elbow extension to onset of finger opening was too short for either to have triggered finger opening (across subjects means were 4 ms for wrist flexion and 21 ms for elbow extension). In additional analysis, no relation was found between the time of onset of earlier occurring rotations at the shoulder and the time of onset of finger opening. We concluded that, although a role for all proprioceptive feedback in triggering finger opening cannot be disproved by these experiments, it can be ruled out for feedback arising from elbow extension and wrist flexion, and it seems unlikely for feedback arising from events occurring very early in the throw. The more likely possibility is that finger opening in an overarm throw is triggered by a central command based on an internal model of hand trajectory.

Biomechanical Phenomena↗
PubMed2001

General coordination of shoulder, elbow and wrist dynamics during multijoint arm movements.

Studies of multijoint arm movements have demonstrated that the nervous system anticipates and plans for the mechanical effects that arise from motion of the linked limb segments. The general rules by which the nervous system selects appropriate muscle activities and torques to best deal with these intersegmental effects are largely unknown. In order to reveal possible rules, this study examined the relationship of muscle and interaction torques to joint acceleration at the shoulder, elbow and wrist during point-to-point arm movements to a range of targets in the horizontal plane. Results showed that, in general, dynamics differed between the joints. For most movements, shoulder muscle torque primarily determined net torque and joint acceleration, while interaction torque was minimal. In contrast, elbow and wrist net torque were determined by a combination of muscle and interaction torque that varied systematically with target direction and joint excursion. This "shoulder-centered pattern" occurred whether subjects reached targets using straight or curved finger paths. The prevalence of a shoulder-centered pattern extends findings from a range of arm movement studies including movement of healthy adults, neurological patients, and simulations with altered interaction effects. The shoulder-centered pattern occurred for most but not all movements. The majority of the remaining movements displayed an "elbow-centered pattern," in which muscle torque determined initial acceleration at the elbow and not at the shoulder. This occurred for movements when shoulder excursion was <50% of elbow excursion. Thus, both shoulder- and elbow-centered movements displayed a difference between joints but with reversed dynamics. Overall, these findings suggest that a difference in dynamics between joints is a general feature of horizontal plane arm movements, and this difference is most commonly reflected in a shoulder-centered pattern. This feature fits well with other general shoulder-elbow differences suggested in the literature on arm movements, namely that: (a) agonist muscle activity appears more closely related to certain joint kinematics at the shoulder than at the elbow, (b) adults with neurological damage display less disruption of shoulder motion than elbow motion, and (c) infants display adult-like motion first in the shoulder and last at the wrist.

Adult↗