Biomedical subjects

N Wuelker

Publications and source records attributed to N Wuelker.

11 recordsLinked to original sources

PubMed1996

[A dynamic shoulder model for biomechanical measurements of shoulder specimen].

The article discusses a dynamic shoulder model capable of simulating the forces generated by the rotator cuff and the deltoid muscle, and elevation movements of the glenohumeral joint using, a computer-aided servohydraulic unit. In 10 cadaver shoulder specimen, the effects of the loss of function of the supraspinatus muscle on maximum elevation was determined with an ultrasound system. Changes in the so-called impingement pressure below the coracoacromial arch were determined with the aid of capacitive pressure sensors. With the supraspinatus muscle inactive/ absent, the maximum elevation of the humerus showed a decrease of 6% (p < 0.05), which, however, was overcome by an increase in deltoid power of only one-third of the supraspinatus muscle power loss. For a simulated isolated supraspinatus defect, the subacromial pressure below the coracoacromial arch decreased by 8% (p > 0.05). These results confirm clinical investigations showing that isolated lesions affecting the supraspinatus tendon often fail to produce symptoms and thus require no surgical reconstruction.

Adult↗

PubMed1995

A dynamic shoulder model: reliability testing and muscle force study.

This study introduces a dynamic shoulder model, where forces were applied to individual muscles in ten cadaveric specimens. The model provided reproducible glenohumeral joint motion and thereby allowed the investigation of active, glenohumeral joint mechanics. Forces were created by servo-actuated hydrodynamic cylinders and applied to the deltoid muscle and to the rotator cuff through wire cables. Computerized regulation initiated precise, time controlled cycles of glenohumeral joint motion. The position of the glenohumeral joint in all spatial orientations was measured and recorded using an ultrasonic sensor device. Reproducibility of glenohumeral joint motion was demonstrated on the basis of five cycles of glenohumeral joint elevation. Repeatability variance of position measurements for five cycles of elevation averaged 0.80 degrees for abduction, 0.75 degrees for anteflexion and 1.36 degrees for internal rotation. Arm weight and force distribution at the shoulder musculature were estimated according to the literature. In comparison to estimated physiologic conditions, a one third increase of arm weight led to a significant (p < 0.05) decrease of elevation of 20%, a one third decrease of arm weight to an average increase of elevation of 18% (p < 0.05). Exclusion of the supraspinatus muscle caused a significant (p < 0.05) 6% decrease of elevation of the glenohumeral joint. Without force applied to the subscapularis and infraspinatus/teres minor muscles, elevation decreased 16% (p < 0.05). A decrease of glenohumeral joint elevation of 25% resulted when force was applied to the deltoid muscle alone (p < 0.05).

Adult↗

PubMed1994

Function of the supraspinatus muscle. Abduction of the humerus studied in cadavers.

We evaluated the function of the supraspinatus tendon with a dynamic shoulder model. Active glenohumeral joint motion was simulated in 10 cadaveric shoulder specimens with hydrodynamic cylinder forces at the deltoid muscle and at the rotator cuff. Computerized regulation initiated standardized cycles of glenohumeral joint motion, where the isolated effect of the supraspinatus muscle could be studied. The efficacy of the supraspinatus muscle on elevation of the glenohumeral joint was measured with an ultrasonic sensor system. Pressures underneath the coracoacromial vault were recorded with capacitive sensors, as an indicator of the impingement at the shoulder. Elimination of force of the supraspinatus muscle led to a 6 percent decrease in elevation of the glenohumeral joint. The deltoid muscle was able to reverse this loss of elevation by a force increase of one third of the lost supraspinatus force. If no force was applied to the supraspinatus muscle, average pressures underneath the coracoacromial vault decreased 8 percent. It was concluded that the supraspinatus produces less torque and more glenohumeral joint compression than the deltoid. However, the supraspinatus has no effect on depression of the humeral head during elevation. The clinical consequence of our observations is that operative closure of supraspinatus tendon defects is not mandatory.

Adult↗

PubMed1994

Translation of the glenohumeral joint with simulated active elevation.

Translation of the glenohumeral joint was measured with a dynamic shoulder model during elevation of the arm in 8 cadaveric specimens. Controlled hydrodynamic actuator forces were applied to the deltoid muscle and the rotator cuff through wire cables. Using a constant force ratio, the glenohumeral joint was elevated to 90 degrees. The position of the arm in all spatial orientations was measured with an ultrasonic device. Reproducibility of glenohumeral joint motion was demonstrated on the basis of 5 cycles of glenohumeral joint elevation. The rotational center of the humeral head was used as the reference point for translation. Translation during elevation of the glenohumeral joint between 20 degrees and 90 degrees averaged 9.0 mm +/- 5.2 mm superiorly and 4.4 mm +/- 1.3 mm anteriorly. Physiologic variation of muscle activity, which is not yet fully understood, was not included in the model. In vivo, translation may be diminished by coordinated activity of the rotator cuff. The presence of significant glenohumeral joint translation underlines the importance of active, muscular guidance at the shoulder. Physiologic translation must be considered in the design of total shoulder arthroplasty, in shoulder instability, and in the impingement syndrome.

Adult↗

PubMed1994

[Function of the supraspinatus muscle in a dynamic shoulder model].

Active glenohumeral joint motion was simulated in ten cadaveric shoulder specimens with hydrodynamic cylinder forces at the deltoid muscle and at the rotator cuff. Computerized regulation initiated standardized cycles of glenohumeral joint motion in which the isolated effect of the supraspinatus muscle could be studied. The effect of the supraspinatus muscle on the elevation of the glenohumeral joint was measured with an ultrasonic sensor system. Pressures underneath the coracoacromial arch as an indicator of the 'impingement' at the shoulder were recorded with capacitive sensors. Elimination of force of the supraspinatus muscle led to a significant 6% decrease in elevation (p < 0.05). The deltoid muscle was able to reverse this loss of elevation by an increase in force equal to only one third the force lost at the supraspinatus muscle. When no force was applied to the supraspinatus muscle average pressures under the coracoacromial vault decreased by 8% (p > 0.05). In conclusion, the supraspinatus muscle produces less torque and more glenohumeral joint compression than the deltoid muscle. However, the supraspinatus muscle has no significant effect on the centering of the humeral head on the glenoid during elevation.

Acromioclavicular Joint↗

PubMed1994

Biomechanical data concerning the shoulder impingement syndrome.

This study evaluates forces underneath the coracoacromial vault during elevation of the arm, using a dynamic shoulder model. Muscle forces at the glenohumeral joint were simulated with hydrodynamic cylinders and applied to the deltoid muscle and to the rotator cuff through wire cables in ten anatomic specimens. Computerized regulation initiated precise, time-controlled cycles of glenohumeral joint motion. The position of the arm in all spatial orientations was measured with an ultrasonic device. Forces underneath the coracoacromial vault were recorded with capacitive sensors. The mean force during one cycle of elevation averaged 13.9 N +/- 12.5 N underneath the acromion, 0.43 N +/- 0.51 N underneath the coracoacromial ligament, and 3.44 N +/- 4.37 N underneath the coracoid process. The peak force averaged 37.8 N +/- 33.2 N underneath the acromion, 3.03 N +/- 2.62 N underneath the coracoacromial ligament, and 6.93 N +/- 7.38 N underneath the coracoid process. Forces under the coracoid process exceeded forces under the acromion in some specimens. A marked increase in forces was observed at the final stage of arm elevation and during early reverse-elevation in most specimens. The authors believe that these force values represent the pathomechanics of the shoulder impingement syndrome.

Acromioclavicular Joint↗

PubMed1993

A case of stenosing peroneal tendovaginitis.

At the foot and ankle, stenosing peroneal tendovaginitis has only rarely been described in literature. The superior and inferior peroneal retinacula, however, may cause symptoms of stenosis similar to other tendons in the foot and the hand. A case of a forty-three year-old woman is presented, where posttraumatic stenosing peroneal tendovaginitis caused sudden pain on supination of the foot. Nodular tendon swelling was present on a preoperative CT-scan. The condition was treated successfully by transsection of the peroneal retinacula.

Adult↗

PubMed1992

Biterminal tenotomy for the treatment of congenital muscular torticollis. Long-term results.

Fifty-five patients who, in a twenty-eight-year period, had been managed with a biterminal open release because of congenital muscular torticollis, were re-examined at an average of fifteen years and a minimum of five years after the operation. Forty-eight patients reported no functional or cosmetic impairment. Palpable soft-tissue strands remained in twenty-nine patients, but bending toward the untreated side was limited more than 10 degrees in only one patient. The rate of recurrence was 2 per cent. Facial asymmetry improved or resolved in more than one-half of the patients. We recommend that biterminal release be performed at the age of three to five years in all patients who do not respond to non-operative treatment.

Adolescent↗

PubMedDate not supplied

Coracoacromial pressure recordings in a cadaveric model.

A dynamic shoulder model was used to determine the pressure distribution under the acromion, the coracoacromial ligament, and the coracoid process with simulated active glenohumeral joint motion in cadaveric specimens. Computerized regulation of servo-actuator forces initiated controlled cycles of glenohumeral joint motion. Pressures were recorded by using capacitive sensors. Peak pressures averaged 56.6 N/cm2 and were located at the anterolateral border of the acromion in most specimens. Marked pressures were present under the coracoid process. Lack of force of the supraspinatus muscle resulted in an 8% decrease of mean coracoacromial pressures, lack of force on the subscapularis and infraspinatus/teres minor muscles in a significant 61% increase, and lack of force on all rotator cuff muscles in a significant 35% increase. After anterior acromioplasty was performed, mean coracoacromial pressures decreased 5%.

Acromion↗

PubMedDate not supplied

Dynamic glenohumeral joint stability.

Stability of the glenohumeral joint with an anterior, posterior, and inferior displacement force of 50 N was measured in a dynamic shoulder model. Controlled hydrodynamic actuator forces were applied to the deltoid muscle and to the rotator cuff in seven anatomic specimens. During elevation of the arm the position of the humerus was measured with a six-degree-of-freedom ultrasonic sensor device. The rotational center of the humeral head was used as a reference point for translation. A displacement force of 50 N led to significant humeral head displacement anteriorly and posteriorly but not inferiorly. A 50% reduction of rotator cuff forces increased anterior displacement by 46% and posterior displacement by 31%. Venting of the glenohumeral joint space and of the subacromial bursa resulted in a 50% increase of anterior displacement, a 19% increase of posterior displacement, and significant inferior displacement. This study demonstrates that in addition to passive stabilizers and negative intraarticular pressure, rotator cuff force significantly contributes to stabilization of the glenohumeral joint during arm motion. Muscle strength and coordination should gain more emphasis in the diagnosis and treatment of shoulder instability.

Adult↗

PubMedDate not supplied

[Biomechanic results in impingement syndrome of the shoulder].

Forces underneath the coraco-acromial vault during elevation of the arm were evaluated with a dynamic shoulder model. The deltoid muscle and the rotator cuff muscles were simulated with a hydrodynamic device, in ten autopsy specimens. Controlled cycles of glenohumeral joint motion were initiated with computerised regulation. An ultrasonic device measured the position of the arm in all spatial orientations. Capacitive sensors recorded forces underneath the coraco-acromial vault. The mean force during one cycle of elevation averaged 13.9 Newton +/- 12.5 Newton underneath the coraco-acromial ligament and 3.44 Newton +/- 4.37 Newton underneath the coracoid process. The peak force averaged 37.8 Newton +/- 33.2 Newton underneath the acromion, 3.03 Newton +/- 2.62 Newton underneath the coraco-acromial ligament and 6.93 Newton +/- 7.38 Newton underneath the coracoid process. The force markedly increased at the final stage of arm elevation and during early reverse-elevation in most specimens, corresponding to the painful arc sign. In some specimens, the force under the coracoid process exceeded the force under the acromion. Osteophytes protruding into the subacromial space may lead to a concentration of force and to high regional pressures.

Adult↗