Fifteen patients were managed between November 1983 and February 1991 for an isolated suprascapular neuropathy. The average age of the thirteen male and two female patients at the time of the diagnosis was thirty-five years (range, fifteen to fifty-four years). The left shoulder was involved in seven patients and the right shoulder, in eight patients; the dominant extremity was involved in ten patients. The average duration of the symptoms before the diagnosis was eleven months (range, six to sixteen months). The average duration of follow-up was three years and eleven months (range, one year to eight years and ten months). The one-year clinical data on the patient (Case 12, a drug abuser) who was lost to follow-up after one year were included in the study because neuropathy is a fairly uncommon condition.
All of the patients had pain in the posterolateral aspect of the shoulder at rest. The pain, which was exacerbated by activity, was described as a dull ache with an occasional sensation of burning and frequent radiation into the ipsilateral extremity and side of the neck. The patients also reported a feeling of weakness in the affected shoulder, especially when performing overhead activities.
Six of the fifteen patients reported a specific traumatic event before the onset of symptoms: five fell, and one sustained a blunt injury to the shoulder. Six other patients, who participated in sports at a competitive level, reported pain and a feeling of weakness when participating in athletic activities that involved repetitive overhead movements. Two of these six patients were weight lifters, two were tennis players, one was a swimmer, and one was a baseball player. Two other patients were unable to identify a precipitating event or activity. The neuropathy in the remaining patient (Case 12) possibly developed as a result of traction or compression after the patient had lain comatose for several hours (Table I).
Clinical Examination
Muscle strength was graded with the system of the British Medical Research Council on a scale of 0 to 5, with 0 indicating no muscle activity; 1, visible muscle contraction; 2, muscle contraction with the effect of gravity eliminated; 3, muscle contraction against gravity; 4, muscle contraction against manual resistance; and 5, normal muscle power36. Muscle strength on abduction was grade 4 for nine patients and grade 5 for six. Muscle strength on external rotation was grade 3 for nine patients and grade 4 for six.
Atrophy of the muscles of the rotator cuff was graded, on the basis of visual examination, as mild (barely discernible), moderate (easily discernible), or severe (obvious flattening of the muscle mass in the supraspinatus or infraspinatus fossa). Ten patients had moderate atrophy, and five had mild atrophy (Table I).
Ten patients had a decreased range of motion of the ipsilateral shoulder. Forward elevation averaged 160 degrees (range, 140 to 170 degrees); abduction, 150 degrees (range, 140 to 170 degrees); and external rotation at 0 degrees of abduction, 40 degrees (range, 20 to 55 degrees). Three patients had a symmetrical range of motion of the shoulders. For two patients, only the difference in the range of motion between the two shoulders was recorded; one patient had 15 degrees less external rotation at 0 degrees of abduction and 10 degrees less abduction and forward elevation compared with the contralateral side, and the other had 10 degrees less external rotation at 0 degrees of abduction.
Radiographic Evaluation
Anteroposterior, scapular Y, axillary, and Stryker notch radiographs of the shoulder were made for all patients. None of the radiographs revealed abnormal findings. Radiographs of the cervical spine made for five patients who had neck pain also showed normal findings. Seven patients had arthrography of the shoulder and three others had magnetic resonance imaging to rule out a tear of the rotator cuff. Computerized tomography scans were made for two patients to rule out a tumor.
Electrodiagnostic Evaluation
Electromyographic and nerve-conduction studies showed abnormalities in the supraspinatus and infraspinatus muscles consisting of sharp positive waves, activity at the site of insertion, fibrillations, decreased recruitment, and spontaneous activity at rest in all fifteen patients. Four patients had abnormal results of the nerve-conduction study: in three the motor latency to both the supraspinatus and the infraspinatus muscle was prolonged and the amplitude was reduced, and in one only the distal motor latency of the infraspinatus was prolonged and the amplitude was reduced. The diagnosis of suprascapular neuropathy was made on the basis of the clinical signs and symptoms and the abnormal electrodiagnostic findings after the exclusion of other causes of pain in the shoulder.
Non-Operative Treatment
The program of physical therapy, which was continued for a minimum of six months, focused on increasing the strength of the muscles of the rotator cuff, the deltoid muscle, and the periscapular muscles. During the period of rehabilitation, the patient was asked to avoid lifting heavy objects or performing activities that exacerbated the symptoms. Initially, the weight of the upper extremity was used to provide resistance; gradually, elastic tubing and weights were added to the program to provide increased resistance. Emphasis was placed on increasing the strength of the scapular stabilizing muscles, in particular the trapezius, rhomboids, levator scapulae, and serratus anterior, since weakness of these muscles leads to instability of the scapula. The instability, in turn, alters the length-tension relationship of the rotator cuff, decreases glenohumeral congruency, and places additional stresses on the static and dynamic restraints of the glenohumeral joint. Exercises to strengthen scapular protraction, retraction, elevation, and depression were also included. Resistance and proprioceptive neuromuscular facilitation exercises that incorporate more movements that are closer to normal function were used. To facilitate overhead activities, the strengthening exercises included movements to improve the performance of the muscles involved in deceleration or slowing of the extremity during the follow-through phase of these activities. During this phase, the posterior muscles of the shoulder must act eccentrically, producing tension as the muscles contract with associated lengthening of the muscle, to control and decelerate the limb from the high velocities achieved during overhead activities3,7,16,33. Therefore, the eccentric component of these exercises was stressed.
The supraspinatus muscle was strengthened with the patient prone and the extremity abducted 100 degrees and externally rotated 90 degrees6,31,35. The extremity was then raised vertically with the elbow in extension. A second exercise was performed with the patient standing and the extremity in 30 degrees of forward elevation and 90 degrees of internal rotation. The extremity was elevated in the plane of the scapula with the elbow in extension.
The infraspinatus and teres minor muscles were strengthened by external rotation of the shoulder with the extremity held in 15 to 20 degrees of humeral abduction and 30 degrees of forward elevation. The patient was instructed to complete three sets of ten repetitions for each of the exercises. The resistance applied through the use of elastic bands, dumbbells, and isotonic and isokinetic machines was set so that the target muscle groups became fatigued by the end of the third set of repetitions. The resistance was increased when the patient was able to complete three sets of each exercise without fatigue. The same exercises were also performed with the extremity abducted 90 degrees.
The deltoid was strengthened by abduction of the shoulder with the elbow in extension; the exercises to strengthen the anterior aspect of the deltoid were performed with the shoulder in forward elevation, and those for the posterior aspect were performed with the shoulder in extension in the sagittal plane, with use of a rowing-type motion. The exercises for the middle fibers of the deltoid were performed with abduction of the shoulder in the coronal plane and the shoulder in neutral rotation.
Operative Treatment
Three patients (Cases 13, 14, and 15) had operative treatment at six, seven, and fourteen months after the diagnosis, respectively, because of continuing symptoms and persistent abnormalities on the electrodiagnostic studies (Table I). One patient (Case 13), for whom the diagnosis had been made eight months after a blunt injury to the scapula in a sailing accident, continued to have pain over the posterolateral aspect of the shoulder as well as weakness when performing overhead activities despite six months of physical therapy. A computerized tomography scan with three-dimensional reconstruction revealed stenosis of the suprascapular notch and a calcified suprascapular ligament. These were treated with release of the suprascapular ligament and widening of the suprascapular notch.
The second patient (Case 14), a baseball pitcher, had pain in the posterolateral aspect of the shoulder with weakness of external rotation and a decrease in the velocity and accuracy of his pitches. The pain continued despite seven months of physical therapy, and a release of the suprascapular ligament was performed. No abnormalities were noted intraoperatively.
The third patient (Case 15), a tennis player, had pain with abduction and external rotation during backhand swings with adduction of the ipsilateral shoulder as well as a feeling of weakness when serving. The symptoms persisted despite fourteen months of physical therapy, and a release of the suprascapular ligament was performed.
The operations were performed with the patient under general anesthesia in the beach-chair position. The skin incision was made parallel and approximately one centimeter superior to the spine of the scapula. The trapezius was sharply elevated off the scapular spine and retracted superiorly, and the supraspinatus was retracted inferiorly to expose the transverse suprascapular ligament and the suprascapular nerve. The transverse ligament was resected while the underlying nerve was protected. The suprascapular nerve was then explored along its course, from the suprascapular notch to the spinoglenoid notch, to detect any abnormalities or evidence of compression. Non-absorbable sutures were used to reattach the trapezius to the scapula.
The patient began performing pendulum exercises on the day of the operation. For the first three weeks postoperatively, the physical therapy consisted of active-assisted and active range-of-motion exercises. The patient then followed the same protocol as that used after the non-operative treatment. Supervised physical therapy was continued for at least three months, depending on the presence of pain and strength deficits.
Follow-up Evaluation
Twelve of the fifteen patients were evaluated by one of us (S. D. M.) at the latest follow-up examination. The range of motion of the shoulder; the presence of tenderness, asymmetry, or muscle atrophy; muscle strength; and stability were documented. A neurological examination, which included manual muscle-testing, was performed by a neurologist. Two patients were evaluated with a telephone interview; one of them (Case 10) had had a detailed clinical evaluation at five years, and the other (Case 11), at two years and seven months. Another patient (Case 12) was lost to follow-up after one year, but the clinical findings at the last examination are included for completeness.
A result was considered excellent when the patient had returned to the former level of unrestricted activity without pain or objective weakness; good when there was persistent pain, objective signs of muscle weakness, or some decreased function of the shoulder; fair when two of the conditions just mentioned applied; and poor when all three of the conditions applied.
Thirteen patients had a second electromyographic and nerve-conduction study and dynamic isokinetic testing of both upper extremities. Concentric contraction of the deltoid and supraspinatus muscles (external rotators and abductors) was evaluated at 60 and 120 degrees per second, and eccentric contraction was evaluated at 60 degrees per second. The average peak torque and average work were recorded after a set of five repetitions. External rotation was tested, through an arc of motion of 50 degrees, with the patient supine and the shoulder in the modified neutral plane of the scapula (25 degrees of abduction and 35 degrees of forward elevation). Abduction was tested, with the patient seated and the extremity in internal rotation to isolate the supraspinatus, through an arc of motion of 20 to 75 degrees to prevent accessory movements of the trunk.
The result was excellent for six patients, good for eight, and poor for one. Of the twelve patients who were managed non-operatively, five had an excellent result and seven had a good result. Of the three patients who were managed operatively, one had an excellent result, one had a good result, and one had a poor result (Table I).
Ten of the thirteen patients who returned for a clinical evaluation, which included an electromyographic and nerve-conduction study, had been managed non-operatively. Four of the ten had an excellent result, and six had a good result. Four of the six patients who had a good result had atrophy of the supraspinatus and infraspinatus muscles; it was moderate in two and mild in two. Of these four patients, three (two who had moderate atrophy and one who had mild atrophy) had grade-4 muscle strength on abduction and external rotation and one (who had mild atrophy) had grade-4 muscle strength on external rotation. All four had unrestricted function of the shoulder, abnormal electromyographic findings, and normal findings on the nerve-conduction study (Table I).
The three remaining patients who returned for a clinical evaluation had been managed operatively after the initial period of non-operative management, as mentioned previously. One patient (Case 13) had an excellent result after widening of the stenotic notch and release of the calcified suprascapular ligament. The second patient (Case 14), who was a baseball pitcher, had a good result and returned to pitching. He did not have pain but did have persistent mild atrophy of the muscles and grade-4 motor strength on external rotation. The electromyographic study showed persistent neuropathy. The third patient (Case 15), who had a poor result, had moderate pain, atrophy, weakness, and decreased function. The patient reported an insidious return of the pain and weakness in the shoulder during the year before the examination. He continued to play tennis despite moderate pain with abduction, external rotation, and adduction of the shoulder. He also had cervical pain with radiation to the affected shoulder on axial loading of the head and flexion of the neck toward the ipsilateral shoulder. The patient refused evaluation to exclude cervical radiculopathy. He had not had cervical symptoms at the time of the initial evaluation, and cervical radiographs had not been made. The nerve-conduction study at the latest follow-up examination revealed abnormal findings.
The questionnaire used to evaluate two patients by telephone elicited information on strength, range of motion, pain, function, and over-all satisfaction with the outcome. One patient (Case 11) was extremely satisfied with the outcome, had no pain, had excellent strength, and had returned to his previous level of function at three years and six months. The clinical evaluation at two years and seven months had revealed excellent function of the shoulder without pain, weakness, or evidence of atrophy. He refused additional electrodiagnostic studies. The second patient (Case 10) had normal electrodiagnostic findings, had returned to his previous level of function, and had normal strength with no sign of atrophy when he was evaluated clinically by one of us (R. F. W.) five years postoperatively. When he was contacted by telephone at eight years and ten months, the result was still excellent, and he continued to be an avid weight lifter.
The electromyographic findings were abnormal for six of the thirteen patients who had a second study. The studies were characterized by sharp positive waves, activity at the site of insertion, fibrillations, and spontaneous activity at rest. One patient (Case 15) had an abnormal latency to the supraspinatus of 7.2 milliseconds (normal, 2.7 ± 0.7 milliseconds). Two of the six patients had had operative treatment. All six patients had muscle atrophy, which was moderate in three and mild in three (Table I). The more severe the atrophy, the greater the number of sharp positive waves, activity at the site of insertion, fibrillations, and decreased recruitment.
Isokinetic Testing
Twelve of the thirteen patients who returned for follow-up had dynamic isokinetic testing of the involved and contralateral extremities. The patient who had a poor result (Case 15) refused to be tested. Five patients (one who had been managed operatively and four who had been managed non-operatively) had weakness on manual muscle-testing that was also identified with dynamic isokinetic testing. All five patients had abnormal electromyographic findings and obvious muscle atrophy, which was moderate in two and mild in three. Two patients had grade-4 muscle weakness on external rotation only, and the remaining three patients had grade-4 weakness on abduction and external rotation (Table I).
Isokinetic testing of abduction in the seven patients who had a good result revealed an average deficit of 20 per cent in peak torque and an average deficit of 29 per cent in work compared with the values for the contralateral side. The five patients who had an excellent result had an average deficit of 1 per cent in peak torque and performed an average of 7 per cent more work compared with the values for the contralateral side. Isokinetic testing of external rotation revealed an average deficit of 24 per cent in peak torque and 25 per cent in work for the patients who had a good result and 7 per cent more peak torque and 3 per cent less work for the patients who had an excellent result. Strength deficits of less than 20 per cent on dynamic isokinetic testing were not detectable on manual muscle-testing.
Pain
All of the patients had had pain in the posterolateral aspect of the shoulder at rest before treatment. Three patients (Cases 4, 5, and 15) had moderate atrophy after treatment (Table I). Two (Cases 4 and 5) of these three patients, who had a good result with non-operative management, had occasional mild pain during maximum abduction of the shoulder. One (Case 5) of the two patients, who traveled frequently, had pain when carrying luggage with the strap over the affected shoulder. The third patient (Case 15), who had been managed operatively, had a poor result and moderate pain on external rotation, abduction, and adduction of the ipsilateral shoulder.
Motion
In twelve patients, forward elevation averaged 170 degrees (range, 165 to 175 degrees); abduction, 170 degrees (range, 165 to 175 degrees); and external rotation at 0 degrees of abduction, 60 degrees (range, 30 to 85 degrees). Eleven of the twelve patients had no restriction of motion compared with that on the contralateral side. The patient who had a poor result (Case 15) had 20 degrees less external rotation of the affected shoulder compared with that on the contralateral side. The two patients (Cases 10 and 11) who were interviewed by telephone thought that the range of motion of the affected shoulder was the same as that of the contralateral shoulder. The range of motion of the affected shoulder of the patient who was followed for only one year (Case 12) was equal to that of the contralateral shoulder at the last evaluation; however, the actual ranges were not documented.
Suprascapular neuropathy produces pain in the posterolateral aspect of the shoulder that may radiate into the ipsilateral extremity, shoulder, or side of the neck, with weakness on abduction and external rotation of the shoulder. The pain frequently is described as a deep burning or aching and can often be elicited by palpation over the region of the suprascapular notch. The location of the pain and other symptoms can mimic those of more common entities, such as impingement, rotator-cuff disease, cervical disc disease, brachial neuropathy, tendinitis of the biceps, adhesive capsulitis, glenohumeral degenerative joint disease, acromioclavicular joint disease, instability of the shoulder, thoracic outlet syndrome, and Pancoast tumor32.
The suprascapular nerve is a mixed sensorimotor nerve formed by the fifth and sixth cervical nerves with branches occasionally from the fourth. There are no sensory cutaneous branches; however, there are articular sensory branches to the capsule and ligaments of the glenohumeral and acromioclavicular joints. The nerve courses beneath the transverse suprascapular ligament in the suprascapular notch to enter the supraspinous fossa1,23,28. Ganglions or other space-occupying lesions can produce focal compression of the nerve along its course2,10,13,14,18,19,24,31. Suprascapular neuropathy can develop secondary to traction on the nerve from repetitive microtrauma, after a single traumatic event that causes swelling and subsequent irritation of the nerve, or in association with a lesion of the brachial plexus.
Mechanical stretching has been shown to produce non-linear stress-strain changes in peripheral nerves21. The nerve has a low modulus of stress that increases with increased stress. Beel et al.5 noted that chronically injured nerves have altered biomechanical properties, such as increased stiffness, which lead to increased stress. Stretching of these nerves leads to further damage. In addition, sustained stretching of the nerve leads to physiological changes. Kwan et al.21 noted marked alterations of conduction in the nerve with a sustained stretch of 6 per cent beyond its in situ length. A slightly increased stress of 15 per cent of the ultimate length of the nerve can cause irreversible damage20,21. In the studies by Kwan et al.20,21, the perineurium ruptured, leaving the epineurium intact. Therefore, gross inspection of the nerve would not reveal any of the underlying pathological changes. Lunborg and Rydevik22 as well as Trumble et al.34 showed that increased elongation of the nerve decreased the blood flow, leading to ischemia with resultant injury to the nerve. We agree with the theory that entrapment of the nerve can make it susceptible to a traction-type injury secondary to dynamic repetitive forces generated by normal muscle function and can lead to neurapraxia or even axonotmesis6,11,20-22,30,34.
Most authors have agreed that electromyographic studies are essential to confirm the diagnosis of suprascapular neuropathy. Initially, all fifteen patients in the present study had abnormal findings on the electromyogram. After treatment, six patients (four who had been successfully managed non-operatively and two for whom non-operative management had failed) of the thirteen who had a second electromyogram had abnormal findings. Nerve-conduction studies may show an increased latency but are not essential for the diagnosis. Isokinetic testing was sensitive and demonstrated deficits of less than 20 per cent, which were not detectable clinically. Magnetic resonance images of the shoulder should be made to diagnose any discrete anatomical lesion that should be treated13,24.
The best method to prevent permanent muscle atrophy is early diagnosis and treatment. The pathological changes noted in the nerves suggest that it is reasonable to try an initial period of non-operative treatment of six weeks to one year before operative intervention is considered4,6,11,17; however, there has been a lack of data about the effectiveness of such treatment6,9,11,12,17. Non-operative treatment of isolated suprascapular neuropathy is recommended only in the absence of a discrete anatomical lesion. Drez11 suggested that suprascapular neuropathy was secondary to a traction injury rather than to a focal compressive neuropathy and that it should respond to non-operative treatment; however, residual atrophy may persist regardless of the type of treatment. He reported on four patients who had complete relief of pain and normal function of the shoulder after a home program of shoulder exercises and electrical stimulation of the muscles of the rotator cuff. Black and Lombardo6 noted that four patients had a successful outcome after non-operative treatment of a suprascapular neuropathy involving primarily the infraspinatus muscle. Zoltan37 reported complete resolution of symptoms after non-operative treatment of a suprascapular neuropathy that had developed after a dislocation of the shoulder. Ferretti et al.12 evaluated ninety-six top-level volleyball players from the 1985 European Championships and found that twelve had an isolated suprascapular neuropathy with atrophy of the infraspinatus of the dominant shoulder. However, all of the players were unaware of any impairment and played without limitations.
Some authors have recommended immediate operative treatment once the diagnosis of suprascapular neuropathy has been confirmed2,9,15,17,25,26,28-30. Post and Grinblat25 reported on twenty-six of twenty-eight patients who had been managed operatively after an average duration of symptoms of twenty-seven months (range, seven months to nine years and three months). They noted an excellent result for fifteen patients, a good result for ten, and a fair result for one. Callahan et al.8 reported that twenty-one of twenty-three patients who had had operative management were pain-free immediately after the operation; however, pain recurred in four patients two months to four years after the operation, and three of the four had a second operation. A review of several reports6,9,15,17,25-30 showed that, despite operative treatment, fourteen of twenty-three patients continued to have residual atrophy and mild weakness. These studies did not demonstrate a difference in the outcome with regard to atrophy or strength deficits between operative and non-operative treatment. Hadley et al.17 reported on seven patients, one of whom had been managed non-operatively and six of whom had been managed operatively. They recommended non-operative management for patients who had less severe involvement of the shoulder, and they reported that the patient who had been managed non-operatively had relief of symptoms and return of muscle bulk. Two of the six patients who had had an operation continued to have weakness and persistent atrophy, and four had increased bulk and strength of the muscle. Post and Mayer26 reported good and excellent results after release of the suprascapular ligament in eight of nine patients who had entrapment of the suprascapular nerve. The average duration of symptoms was thirty-eight months (range, nine to sixty months). The remaining patient was managed non-operatively, but the treatment was not described.
Unrestricted function of the shoulder and relief of pain may be obtained by maximizing the function of the rotator cuff and periscapular muscles, and although residual atrophy and weakness may persist they do not preclude normal shoulder function. The residual weakness may be clinically relevant in a highly trained athlete in whom even a 25 per cent deficit on isokinetic testing can substantially affect over-all performance.
The favorable results noted with non-operative treatment of suprascapular neuropathy suggest that such an approach is warranted if a space-occupying lesion is not the cause of the condition. If the condition does not improve, then an operation should be performed for relief of the pain.