Frank W. Jobe

Dynamic electromyographic analysis of the throwing shoulder with glenohumeral instability

Fifteen male athletes who were skilled in throwing and who had chronic anterior instability of the shoulder (Group 1) were evaluated by dynamic intramuscular electromyography while pitching a baseball. Indwelling wire electrodes recorded the levels of activity in the biceps, middle deltoid, supraspinatus, infraspinatus, pectoralis major, subscapularis, latissimus dorsi, and serratus anterior throughout the entire pitching sequence. These signals were synchronized electronically with records of the pitch that were made using high-speed photography. The pitch was divided into five phases: wind-up, early cocking, late cocking, acceleration, and follow-through. The results were compared with previous identical studies of twelve healthy, uninjured male athletes who were skilled in throwing (Group 2). Activity increased mildly in the biceps and supraspinatus in Group 1 as compared with Group 2. Similar patterns of activity were demonstrated in the deltoid. In Group 1 the infraspinatus had increased activity during early cocking and follow-through but had decreased activity during late cocking. The pectoralis major, subscapularis, latissimus dorsi, and serratus anterior in Group 1 all were shown to have markedly decreased activity. The study revealed a difference between Groups 1 and 2 in all of the muscles of the shoulder that were tested with the exception of the deltoid. The mildly increased activity levels of the biceps and supraspinatus that were found in Group 1 may compensate for anterior laxity. The marked reduction in activity in the pectoralis major, subscapularis, and latissimus dorsi added to the anterior instability by decreasing the normal internal-rotation force that is needed during the phases of late cocking and acceleration.(ABSTRACT TRUNCATED AT 250 WORDS)

Medial instability of the elbow in throwing athletes. Treatment by repair or reconstruction of the ulnar collateral ligament.

From September 1974 to December 1987, seventy-one patients were operated on for valgus instability of the elbow. The average length of follow-up of sixty-eight patients (seventy operations) was 6.3 years (range, two to fifteen years). At the operation, a torn or incompetent ulnar collateral ligament was found. Fourteen patients had a direct repair of the ligament, and fifty-six had a reconstruction of the ligament using a free tendon graft. The result was excellent or good in ten patients in the repair group and in forty-five (80 per cent) in the reconstruction group. Seven of the fourteen patients who had a direct repair returned to the previous level of participation in their sport. Of the fifty-six who had a reconstruction, thirty-eight (68 per cent) returned to the previous level of participation. Twelve of the sixteen major-league baseball players who had a reconstruction as the primary operation (no previous operation on the elbow) were able to return to playing major-league baseball, and two of the seven major-league players who had a direct repair returned to playing major-league baseball. Previous operations on the elbow decreased the chance of returning to the previous level of sports participation (p = 0.04). Fifteen patients had postoperative ulnar neuropathy. This was transient in six patients, only one of whom was unable to return to the previous level of sport. The other nine patients had an additional operation for the neuropathy; four were able to return to the previous level of sport.

Anterior capsulolabral reconstruction of the shoulder in athletes in overhand sports

From April 1, 1985, through June 30, 1987, 25 skilled athletes with shoulder pain secondary to anterior gle nohumeral instability that had failed to improve with conservative therapy had an anterior capsulolabral re construction. All but one athlete completed a formal rehabilitation program with an average followup of 39 months. The results at followup were rated excellent in 68%, good in 24%, fair in 4%, and poor in 4%. Seven teen patients returned to their prior competitive level for at least 1 year. This operation and rehabilitation program may allow many athletes who participate in overhand activities or throwing sports to return to their prior level of competition.

An EMG analysis of the shoulder in pitching A second report

This is the second report in a series of projects dealing with electromyographic (EMG) analysis of the upper extremity during throwing. Better understanding of the muscle activation patterns could lead to more effective preseason conditioning regimens and rehabilitation pro grams. Indwelling wire electrodes recorded the output from the biceps, long and lateral heads of the triceps, pectoralis major, latissimus dorsi, serratus anterior, and brachialis for four professional baseball pitchers. These signals were synchronized electronically with high speed film records of a fast ball. The EMG signals were converted from analog to digital records. Results showed that wind-up and early cocking phases showed minimal activity in all muscles, and such firing which occurred was of low intensity. Late cocking, which occurred after the front foot was firmly planted, showed moderate activity in the biceps. Cocking was termi nated by the pectoralis major and latissimus dorsi. At this point, the trunk began to rotate forward, while the arm remained elevated and the elbow flexed. Also, the shoulder was moving to maximum external rotation. During the acceleration phase, the biceps was notably quiescent, while the pectoralis major, latissimus dorsi, triceps, and serratus anterior were all active. Muscle action at this time terminated external rotation and elbow flexion; i.e., the muscles fired as decelerators and also initiated the opposite actions for ball acceler ation, internal rotation and elbow extension. Follow- through was not only a time of eccentric contraction with muscle activity decelerating the upper extremity complex, it was also an active event with the shoulder moving across the body and the elbow into extension with forearm pronation.

Delineation of diagnostic criteria and a rehabilitation program for rotator cuff injuries

In the examination and rehabilitation of patients with shoulder injuries it is necessary to isolate the individ ual rotator cuff muscles as much as possible. We subscribe to the belief that, independent of the deltoid, the rotator cuff muscles can become fatigued, injured, or atrophied individually. Accordingly, we feel that these muscles must be considered separately during examination and rehabilitation. This paper describes methods and positions to iso late the cuff and, thus, enable the examiner to be more precise in diagnosis and treatment. In addition, individual exercises for each component are de scribed.

An electromyographic analysis of the upper extremity in pitching

The upper extremity is vulnerable to injury during the baseball pitch because of the repetitious nature of the action, the extremes in range of motion, and the high angular velocities and torques generated at the shoulder and elbow. Hence this study was designed to describe the muscle-firing patterns through fine-wire electromyography in 29 muscle bellies in the upper extremities of skilled pitchers during the fastball pitch. The results demonstrated that the muscles functioned with precise timing for joint stabilization to prevent injury, joint activation to transfer forces to the ball, and joint deceleration to dissipate forces after ball release. The synchrony of reciprocal and sequential muscle contraction necessary to accomplish these functions was clearly evident. This study provides a better understanding of the coordinated sequence of muscle activity during the throwing motion; this understanding is crucial to the development of exercise protocols and surgical procedures used for treatment and prevention of shoulder and elbow injuries in the throwing athlete.

A comparative electromyographic analysis of the shoulder during pitching: Professional versus amateur pitchers

Dynamic, fine-wire, intramuscular electromyography (EMG) was performed on 12 different shoulder muscles in 13 normal male subjects as they pitched a baseball. Seven were major league baseball pitchers and six were amateur pitchers. The act of pitching a fast ball was filmed at 450 frames per second with the EMG signals recorded synchronously. The subscapularis, su praspinatus, and infraspinatus muscles were tested in 13 subjects, the biceps brachii muscle was tested in 12, and other shoulder muscles were tested variously among the subjects. Two groups of muscles were identified. Group I mus cles, the supraspinatus, infraspinatus, teres minor, del toid, trapezius, and biceps brachii, served primarily to position the shoulder and elbow for the delivery of the pitch. These muscles were found to have greater activ ity during the early and late cocking stages, with less activity during acceleration. Group II muscles acceler ated the arm and baseball forward in space. These muscles, the pectoralis major, serratus anterior, sub scapularis, and latissimus dorsi, had stronger activity during the propulsive phase of the pitch. The professional pitchers were able to use the mus cles about the shoulder in an efficient manner to achieve greater pitching velocities. The subscapularis and latis simus dorsi muscles of Group II had stronger activity among the professionals, whereas the supraspinatus, teres minor, and biceps brachii muscles of Group I had only minimal activity. The amateurs, on the other hand, continued to use all of the rotator cuff muscles and the biceps brachii muscle of Group I through the accelera tion stage of the pitch. These data may provide a basis for understanding improved performance and an ad junct for sport-specific rehabilitation programs.

The normal shoulder during freestyle swimming : an electromyographic and cinematographic analysis of twelve muscles

The purpose of this paper is to describe the patterns of activity of 12 shoulder muscles in painful shoulders, and compare those patterns of activity with normal shoulders. The results show significant differences in 7 of the 12 muscles. Those muscles included the anterior deltoid, middle deltoid, infraspinatus, subscapularis, up per trapezius, rhomboids, and the serratus anterior. There were no significant differences between muscle activity patterns of normal versus painful shoulders in the latissimus dorsi, pectoralis major, teres minor, su praspinatus, or the posterior deltoid. This information will contribute to the development of muscle condition ing programs to optimize performance and prevent injury, as well as develop programs for scientific reha bilitation strengthening.

Painful athletic injuries of the shoulder.

Pain in the athletes shoulder is likely to have a mechanical origin, because the athlete performs repetitive high-stress activity. Proper treatment is based on understanding the biomechanics and physiology of the tissues, as well as the demands of the patients specific athletic activity. Correct rehabilitation is the key to successful conservative and surgical management. A return to previous activity depends on restoring the normal biomechanics, either through conservative management or surgery. Some of these problems are unsolved and remain fruitful areas for future research.

Arthroscopic Findings in the Overhand Throwing Athlete: Evidence for Posterior Internal Impingement of the Rotator Cuff

SUMMARY The purpose of this article is to describe the outcome of an arthroscopic examination and the pathology in symptomatic shoulders of 41 professional overhand throwing athletes. With the arm in the position of the relocation test, 100% of the subjects had either contact between the rotator cuff undersurface and the posterosuperior glenoid rim or osteochondral lesions. Other key findings included undersurface cuff fraying in 93%, posterosuperior labral fraying in 88%, and anterior labral fraying in 36% of the subjects. This study supports the concept of impingement of the posterior cuff undersurface with the posterosuperior glenoid rim in the overhand throwing athlete with shoulder pain.