J Manipulative Physiol Ther 2001 (Jul); 24 (6): 425–430 ~ FULL TEXT
Chad E. Moreau, DC, Susan R. Moreau, DC
Horrigan Sports Chiropractic Soft Tissue and Athletic Injuries,
2080 Century Park East, Ste 605,
Los Angeles, CA 90067
OBJECTIVE: To describe the clinical management of recurrent shoulder instability in a professional hockey player by using chiropractic management and rehabilitation exercises.
CLINICAL FEATURES: A 23-year-old professional hockey player with recurrent left shoulder pain and instability. He had two previous unsuccessful shoulder operations to correct the instability. He reported that the shoulder "slips out" in positions of abduction and external rotation or when the left arm is moved suddenly above shoulder height. The patient was still playing hockey professionally at the time of the initial visit and did not want to have to take time off for another surgery, so he chose to attempt a conservative approach.
INTERVENTION AND OUTCOME: The patient had undergone strength training for rehabilitation after each of the previous two shoulder operations and had very strong rotator cuff and scapular musculature. Proprioceptive testing revealed a poor response in the left shoulder compared with the right shoulder. Two subjective outcome measures were used to determine the effectiveness of the treatment protocol in reducing the symptoms of recurrent shoulder instability. Much of the treatment focused on proprioceptive training, soft tissue mobilization, and improving joint function.
CONCLUSION: This case demonstrates the potential benefit of chiropractic management and proprioceptive exercises to decrease the symptoms of recurrent shoulder instability.
From the Full-Text Article:
This case demonstrated the successful use of chiropractic procedures and proprioceptive exercise to decrease the symptoms of recurrent shoulder instability. Trauma to tissues that contain mechanoreceptors may result in partial deafferentation, which can lead to proprioceptive deficits.  The consequence of a deficit in proprioception could result in a delay in efferent protective muscle activity.  Normal mechanoreceptor function as modulator of protective muscle responses is vital to prevention of joint injury and to minimize further damage to already injured or destabilized joints.  This would suggest that the type of conservative approach used in this case for a patient with shoulder instability should be considered regardless of whether the patient is a surgical candidate.
The key strategy of this treatment approach was based on the role of proprioceptively mediated neuromuscular control after joint injury and its restoration through rehabilitation. Because several interventions were used simultaneously, it is impossible to determine which intervention had the greatest impact on decreasing the shoulder symptoms. The patient still described incidences of shoulder instability during the treatment period, but at a lesser rate than before treatment was initiated (Fig. 5, Fig. 8).
The patient demonstrated a 30-point increase on the WOSI scores from the initial visit to the final follow-up visit 5 ½ months later. Because the patient's perception of changes of health status was probably the most important indicator of the success of the treatment protocol, a 30-point increase on a 100 point scale for the WOSI was a significant improvement.  The patient symptom diary also demonstrated a significant decrease in episodes of disability during the hockey season after the start of treatment.
Ultimately, the treatment success could have been more objectively measured with a proprioceptive testing device. In this device, the subject's shoulder is positioned in 90 degrees of elbow flexion and shoulder abduction and the testing device is moved into external rotation. The time it takes the subject to sense the shoulder motion is the threshold to detection of motion, which is a measure of proprioceptive sensibility. In the studies that used the proprioceptive testing device, there were significant differences between subjects with stable versus unstable shoulders. [3, 11, 15, 19, 20] Unfortunately such a device is expensive and not practical in the office setting. In this case, although the patient demonstrated subjective improvement of shoulder symptoms, which allowed him to play the entire season, he is still contemplating a third surgery because of the perceived effects of the shoulder instability on his ability to adequately prepare and compete in his sport.
Of course this treatment protocol cannot be generalized to be deemed effective for all cases of shoulder instability. Each specific treatment protocol should be designed with the athlete's sporting demands in mind. In this case the athlete felt the most unstable with impulsive movements into flexion, external rotation, and abduction. Therefore the emphasis of the exercise program was to attempt to increase proprioceptively mediated neuromuscular control in these positions. Although the treatment intervention did not objectively demonstrate an increase in proprioceptively mediated neuromuscular control, it did demonstrate a subjective decrease in the athlete's symptoms of recurrent shoulder instability. In addition, although the contribution of the ligaments and muscles towards shoulder stability is essential and ongoing at any given time, the shoulder is not intended to sustain extreme loads applied with high accelerations. In fact, application of such high and fast loads as occur in sports trauma is the major cause of structural shoulder damage. These events are beyond the capabilities of any stabilizing influence. 
This case demonstrates how an athlete with recurrent shoulder instability had a successful outcome after receiving multimodal treatment of soft tissue mobilization, manipulation, proprioceptive training and taping, nutritional counseling, and conditioning exercises. It further demonstrates that achieving functional and sport-specific activities after musculoskeletal trauma can be enhanced significantly if proprioception is addressed in the treatment program. The decreased frequency of instability occurrences in this case combined with the perceived improvement on the shoulder instability index suggest a gradual stabilization of the proprioceptive function of the shoulder. This would suggest that rehabilitation exercises should focus on the importance of incorporating joint position sensibility and reflexive-type contractions into the therapy program. Future directions for proprioception research should consider the effects of upper extremity training on proprioception in both normal and unstable shoulders. Future studies should also examine the effectiveness of proprioceptive training in nonoperative treatment of shoulder instability. Further research to better understand and use chiropractic management strategies and interventions for athletes with shoulder instability appears warranted.