Background and Purpose. Treatment of patients with impingement symptoms commonly includes exercises intended to restore “normal” movement patterns. Evidence that indicates the existence of abnormal patterns in people with shoulder pain is limited. The purpose of this investigation was to analyze glenohumeral and scapulothoracic kinematics and associated scapulothoracic muscle activity in a group of subjects with symptoms of shoulder impingement relative to a group of subjects without symptoms of shoulder impingement matched for occupational exposure to overhead work. Subjects. Fifty-two subjects were recruited from a population of construction workers with routine exposure to overhead work. Methods. Surface electromyographic data were collected from the upper and lower parts of the trapezius muscle and from the serratus anterior muscle. Electromagnetic sensors simultaneously tracked 3-dimensional motion of the trunk, scapula, and humerus during humeral elevation in the scapular plane in 3 hand-held load conditions: (1) no load, (2) 2.3-kg load, and (3) 4.6-kg load. An analysis of variance model was used to test for group and load effects for 3 phases of motion (31°–60°, 61°–90°, and 91°–120°). Results. Relative to the group without impingement, the group with impingement showed decreased scapular upward rotation at the end of the first of the 3 phases of interest, increased anterior tipping at the end of the third phase of interest, and increased scapular medial rotation under the load conditions. At the same time, upper and lower trapezius muscle electromyographic activity increased in the group with impingement as compared with the group without impingement in the final 2 phases, although the upper trapezius muscle changes were apparent only during the 4.6-kg load condition. The serratus anterior muscle demonstrated decreased activity in the group with impingement across all loads and phases. Conclusion and Discussion. Scapular tipping (rotation about a medial to lateral axis) and serratus anterior muscle function are important to consider in the rehabilitation of patients with symptoms of shoulder impingement related to occupational exposure to overhead work.

https://ir.uiowa.edu/cgi/viewcontent.cgi?article=1000&context=oeh_pubs

Alterations in Shoulder Kinematics and Associated Muscle Activity in People With Symptoms of Shoulder Impingement

We have demonstrated that certain passive motions of the glenohumeral joint are reproducibly accompanied by translation of the head of the humerus on the glenoid. We investigated the relationship of these translations to the position of the glenohumeral joint and to applied torques and forces in seven isolated glenohumeral joints from fresh cadavera, using a six-degrees-of-freedom position sensor and a six-axis force and torque transducer. Reproducible and significant translation occurred in an anterior direction with glenohumeral flexion and in a posterior direction with extension. We also observed translation with cross-body movement. The translation occurring with flexion was obligate in that it could not be prevented by the application of an oppositely directed force of thirty to forty newtons. Operative tightening of the posterior portion of the capsule increased the anterior translation on flexion and cross-body movement and caused it to occur earlier in the arc of motion compared with the intact glenohumeral joint. Operative tightening of the posterior part of the capsule also resulted in significant superior translation with flexion of the glenohumeral joint.

Translation of the humeral head on the glenoid with passive glenohumeral motion

Background: While the anatomy of the medial part of the knee has been described qualitatively, quantitative descriptions of the attachment sites of the main medial knee structures have not been reported. The purpose of the present study was to verify the qualitative anatomy of medial knee structures and to perform a quantitative evaluation of their anatomic attachment sites as well as their relationships to pertinent osseous landmarks.

Methods: Dissections were performed and measurements were made for eight nonpaired fresh-frozen cadaveric knees with use of an electromagnetic three-dimensional tracking sensor system.

Results: In addition to the medial epicondyle and the adductor tubercle, a third osseous prominence, the gastrocnemius tubercle, which corresponded to the attachment site of the medial gastrocnemius tendon, was identified. The average length of the superficial medial (tibial) collateral ligament was 94.8 mm. The superficial medial collateral ligament femoral attachment was 3.2 mm proximal and 4.8 mm posterior to the medial epicondyle. The superficial medial collateral ligament had two separate attachments on the tibia. The distal attachment of the superficial medial collateral ligament on the tibia was 61.2 mm distal to the knee joint. The deep medial collateral ligament consisted of meniscofemoral and meniscotibial portions. The posterior oblique ligament femoral attachment was 7.7 mm distal and 6.4 mm posterior to the adductor tubercle and 1.4 mm distal and 2.9 mm anterior to the gastrocnemius tubercle. The medial patellofemoral ligament attachment on the femur was 1.9 mm anterior and 3.8 mm distal to the adductor tubercle.

Conclusions: The medial knee ligament structures have a consistent attachment pattern.

Clinical Relevance: Identification of the gastrocnemius tubercle and the quantitative relationships presented here will be useful in the study of anatomic repairs and reconstructions of complex ligamentous injuries that involve the medial knee structures.

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The anatomy of the medial part of the knee.

The purpose of this study was to characterize the role of the capsule in the interval between the supraspinatus and subscapularis tendons with respect to glenohumeral motion, translation, and stability. We used a six-degrees-of-freedom position-sensor and a six-degrees-of-freedom force and torque-transducer to determine the glenohumoral rotations and translations that resulted from applied loads in eight cadaver shoulders. The range of motion of each specimen was measured with the capsule in the rotator interval in a normal state, after the capsule had been sectioned, and after it had been imbricated. Operative alteration of this capsular interval was found to affect flexion, extension, external rotation, and adduction of the humerus with respect to the scapula. Modification of this portion of the capsule also affected obligate anterior translation of the humeral head on the glenoid during flexion. Limitation of motion and obligate translation were increased by operative imbrication and diminished by sectioning of the rotator interval capsule. Passive stability of the glenohumeral joint was evaluated with the use of anterior, posterior, and inferior stress tests. Instability and occasional frank dislocation of the glenohumeral joint occurred inferiorly and posteriorly after section of the rotator interval capsule. Imbrication of this part of the capsule increased the resistance to inferior and posterior translation.

The role of the rotator interval capsule in passive motion and stability of the shoulder.

A simple extension of a previously reported object recognition technique has been used to implement a six-degree-of-freedom position/orientation estimator for the measurement of knee replacement motion from two-dimensional (2-D) fluoroscopic images. Computer modeling studies and controlled mechanical tests were performed to assess the accuracy of the technique. The results indicate that knee rotations can be measured with an accuracy of approximately one degree and that sagittal plane translations can be measured with an accuracy of approximately 0.5 mm. The measurement technique is uniquely well suited for performing dynamic kinematic measurements on individuals with knee replacements, and for performing comparative studies among subjects with different designs of knee replacements.

Accurate measurement of three-dimensional knee replacement kinematics using single-plane fluoroscopy

Application of a magnetic tracking device to kinesiologic studies

Method for the measurement of friction between tendon and pulley

The gliding ability of the flexor digitorum profundus tendon and of the palmaris longus tendon through the A2 pulley was compared, in terms of gliding resistance, with use of a system that we developed. Fourteen digits and the ipsilateral palmaris longus tendons from fourteen cadavera were used. The average gliding resistance at the interface between the palmaris longus tendon and the A2 pulley was found to be greater than that between the flexor digitorum profundus tendon and the A2 pulley under similar loading conditions. We concluded that the gliding ability of the palmaris longus tendon was inferior to that of the flexor digitorum profundus tendon in vitro. CLINICAL RELEVANCE: The findings of the present study are consistent with those of in vivo experiments in which extrasynovial tendon grafts have been associated with substantial formation of adhesions. The adhesions may be explained by the poor gliding ability of the palmaris longus tendon. The palmaris longus tendon may have limitations, because of gliding resistance, when it is used as a graft to reconstruct flexor tendons in the digits.

Gliding resistance of extrasynovial and intrasynovial tendons through the A2 pulley.

Ten normal ring fingers from ten donors were used to determine the effect of flexor tendon repair on the gliding resistance between the tendon and the A2 pulley. Gliding resistance was measured for the intact FDP tendon and for the same tendon after it was cut transversely and repaired with a 4/0 Ticron core suture and a 6/0 running epitendinous nylon suture. After repair, the gliding pattern of the tendon through the A2 pulley changed significantly. The resistance and the friction coefficient were approximately doubled (P<0.005).

Flexor Tendon-Pulley Interaction afterTendon Repair A biomechanical study

When tendon excursion takes place through the pulley, friction and drag are encountered at the interface. Repetitive exposure to such friction and attrition of the tendon has been considered one of the important factors causing cumulative trauma and leading to disorders such as tendinitis and tenosynovitis. In this study, development of an experimental method to evaluate friction and drag between the pulley and tendon under different loading conditions and joint configurations is considered. Verification of the model under an ideal situation of sutures across a mechanical pulley was performed.

L. J. Berglund

Papers

Application of a magnetic tracking device to kinesiologic studies

Method for the measurement of friction between tendon and pulley

Gliding resistance of extrasynovial and intrasynovial tendons through the A2 pulley.

Flexor Tendon-Pulley Interaction afterTendon Repair A biomechanical study

Measurement of friction between pulley and flexor tendon.