Biofeedback Training of the
External Rotators to Centralize the Humeral Head in Patients with Anterior
Shoulder Instability and/or Pain.
Linda Saboe, B.P.T., M.C.P.A.
Judy Chepeha, Bsc.P.T., M.C.P.A.
David Reid, M.D., M.Ch.H., F.R.C.S.
Gary Okamura, M.D.
Michael Grace, Ph.D, P. Eng
The Glen Sather Sports Medicine Clinic, and the Division of Orthopaedics.
The University of Alberta
Anterior shoulder instability and impingement
are common athletic complaints associated with overuse, joint laxity,
post-traumatic dislocation and muscle imbalance. While traditionally treated
as clinically discrete entities, it is now accepted that considerable
overlap exists between functional instability and anterior impingement(1-3).
Until recently, rehabilitation programs have
emphasized subscapularis strengthening on the assumption that this muscle
provided an anterior buttress, preventing anterior humeral head subluxation(4-6).
Turkel (1981) has demonstrated inability of the subscapularis to cover
the anterior humeral head in abduction and external rotation(7) and Garth
reports that internal rotation forces actually contribute to anterior
displacement(2). These findings provide an explanation for high failure
rates of traditional rehabilitation programs(8-11).
Jobe and Perry's electromyograhic work identifies
the external rotators, and in particular, the infraspinatus, to be the
primary dynamic anterior shoulder stabilizers in abduction and overhead
motions(12-14). This dynamic stability is provided by preventing forward
motion of the humeral head in the glenoid fossa.
In 1988, a treatment protocol utilizing single
channel electromyographic biofeedback was developed; it has been continuously
tested and enhanced through controlled clinical trials at the University
of Alberta. This program utilizes targeted muscle feedback to perfect
motor skills. By electronically monitoring and amplifying activity of
the external rotators during an apprehensive motion with immediate visual
and auditory feedback to the subject, the performance is changed or shaped.
This program, which emphasizes muscle control rather than strength, requires
motivation, training, and lifelong routines to maintain the established
engram and control shoulder stability.
USING A SINGLE
CHANNEL EMG BIOFEEDBACK SYSTEM
The MyoTrac single channel EMG biofeedback
unit, from Thought Technology, is valuable in the reinforcement of appropriate
external rotator activity. Patients are provided with visual and auditory
feedback of appropriate muscle activity. The unique MyoScan sensor amplifies
the muscle signals at the pickup site, thereby providing excellent sensitivity
with no electrical interference (see figures 1 and 2)
BIOFEEDBACK TREATMENT PROGRAM
- Electrode placement is critical.
Using the disposable triode electrodes, attach the sensor below the
scapular spine with the 2 active electrodes parallel to the orientation
of the muscle fibers. Do not place it over the posterior deltoid
as increased activity in this muscle would drive the humeral head anteriorly.
The patient remains connected to the biofeedback unit during training
and must practice at home, both with and without the unit. For home
practice, the therapist might wish to place an indelible mark on the
skin for electrode placement.
Figure 1. Inside Pannel settings
Figure 2. Threshold and Gain settings
- To determine threshold and gain settings,
have the patient flex the shoulder forward to 70 degrees with the gain
switch at X1, and turn the threshold control until the yellow LED illuminates.
If the activity is greater than 10uV at 70 degrees, set the gain settings
to X10. Again, have the patient flex the shoulder forward to 70 degrees
while turning the threshold control until the yellow LED illuminates.
- Ensure the shoulder is in a pain-free
neutral position, the threshold switch is set to 'CONT', the volume
is set at a pleasant level (with or without the earphones) and the threshold
control and gain reading switch remain in the positions set previously
in step 2. Instruct the patient to use the visual and audio feedback
to increase EMG activity well above the yellow LED. This is done by
tightening the rotator cuff muscles in the neutral position
in order to glide and hold the humeral head posteriorly (figure 3).
This is a key component and must be successfully performed 100 times
(ten sets of 10) prior to progressing to active movement. The use of
many repetitions builds endurance. This procedure is quite fatiguing;
it may require several sessions before the patient can progress to step
Figure 3. Teach contraction in neutral position
- With the theshold set at twice the value
achieved in Step 2, place the patient's elbow in flexion (figure 4).
Instruct to forward flex the adducted and neutral rotated shoulder to
90-100 degrees. As the shoulder is flexed between 70 and 90 degrees,
have the patient tighten the rotator cuff and achieve the threshold
setting, trying to light-up the lights to the right of the first yellow
one. If pain or a sense of subluxation is experienced, stop, rest and
start again through a smaller arc of movement and/or with reduced threshold
settings. When the patient can successfully perform 100 consecutive
repetitions, progress by increasing the threshold and/or movement as
shown in figure 5.
Figure 4. Forward flex to 90-100 degrees
As the patient masters each level, progress
through the following exercises:
a) Forward flexion with a straight elbow.
b) Forward flexion with increasing external
c) Abduction with flexion progressing to
d) Abduction with elbow extension with increasing
e) Abduction from flexion.
f) Abduction from flexion with increasing
g) Reach for objects behind back or overhead.
When the above progression of increasingly
difficult tasks has been completed, progress to the activities specific
to the sport or work task that caused the difficulty. Break the movement
down into component parts and introduce catching or throwing activities
in preparation for a gradual return to normal activity (figures 6, 7).
If general weakness exists, instruct the
patient in appropriate progressive resistance exercises. Include pushups
for serratus anterior (with the arms abducted) and external rotation exercises
resisted using surgical tubing. Avoid resisted exercises which
load in an impingement position (figure 5). All pain free activities
are allowed and encouraged. The patient will require two to three weeks
of supervised physiotherapy, but must do a life-long home program to maintain
the engram. It might be desirable for patients to return for occasional
brief refresher courses.
Figure 8. Instability and impingement are related
This program emphasizes muscle control. Strength
acquisition is important, but secondary. Electrode placement is critical.
The biofeedback program is physically and mentally demanding, therefore,
appropriate rest periods and encouragement must be provided. Slow and
careful progression is usually necessary. Commitment by the therapist
and client are required for the program's success.
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1997 The Biofeedback Federation of Europe