Subacromial Impingement Syndrome

Shoulder pain is one of the more common conditions that physiotherapists treat in an orthopaedic setting, with many of these patients describing impingement like symptoms. Subacromial impingement syndrome (SAIS) is defined as mechanical compression of structures in the subacromial space with movements above shoulder height. Neer originally proposed the idea of impingement syndrome and attributed its development to an unfortunate acromial shape: the infamous hooked acromion.

We now know that SAIS has a multitude of potential causes that include local factors (acromial shape and/or rotator cuff weakness) as well as regional factors (scapula dyskinesis, regional hypomobility and/or multidirectional instability). To the benefit of the clinician SAIS has been categorized into Primary SAIS and Secondary SAIS; where primary refers to glenohumeral impingement secondary to a “Mechanical block” and secondary refers to impingement occurring due to “Instability” as a result of excessive mobility or a loss of motor control.

Typically, SAIS is diagnosed based on a history, with patients describing pain with overhead movements, shoulder stiffness and pain at night.

As with most conditions, clinical tests simply serve to confirm the diagnosis based on the history.

For many years, the Neers and Hawkins-Kennedy tests were considered the best tests for SAIS. Both tests demonstrate good sensitivity, suggesting that a negative test helps rule out a subacromial impingement syndrome(1). Unfortunately, a positive Neers or Hawkins-Kennedy test in isolation does little to improve our confidence in a diagnosis of SAIS. In recent years, clinical tests for SAIS have been clustered to improve their diagnostic accuracy. Park et al.(2) retrospectively looked at patients presenting for surgery and compared their outcomes with presurgical screening test. He used the painful arc, infraspinatus muscle strength test and Hawkins-Kennedy tests to identify SAIS. If two of the three screening tests for SAIS were positive, this was associated with impingement findings upon surgical visualization.

Park et al also found that by replacing the Hawkins-Kennedy test with the drop arm test, the three tests became diagnostic for a full thickness tear of the rotator cuff. Michener et al (3) performed a similar study prospectively and found that a cluster of five tests was beneficial in diagnosing shoulder impingement syndrome. He included the Hawkins-Kennedy sign, painful arc and resisted external rotation tests as cited by Park et al. He also included the empty can test and Neer’s sign for impingement, with three or more tests improving the likelihood of subacromial impingement syndrome. With patients presenting with secondary impingement, the above noted tests may be positive but there will be other findings such as glenuhumeral ligament laxity or an altered scapulohumeral rhythm observed with movements.

Once a diagnosis of SAIS has been established, here is the great news: our multimodal physiotherapy treatment has equal outcomes to cortisone injection and subacromial decompression in two recently published papers. Rhon et al (4) compared the efficacy of cortisone injections to physical therapy for SAIS. 104 patients were randomized to either receive cortisone injection or physical therapy. The physical therapy treatment consisted of cervicothoracic and shoulder girdle manual therapy and exercise as determined by the treating physiotherapist based on each patient’s impairment findings. Both groups demonstrated a 50% improvement in functional outcomes at a one year follow-up. Although there were no differences in outcomes between the two groups at any point during the trial, those receiving physical therapy had fewer future visits to physicians and fewer repeat cortisone injections. No significant adverse effects were seen in either group, although a previous study with SAIS patients did identify a risk of progression of rotator cuff tears from partial thickness to full thickness in patients receiving cortisone injection (5). In a recent systematic review of the literature (6), four studies compared conservative management with surgical intervention for SAIS.

None of the studies reviewed were of strong methodological quality but they all identified no advantage of surgical intervention over conservative management, with surgery carrying significant potential risk for the patient. It is noteworthy that one trial compared supervised exercise with surgical subacromial decompression for SAIS and found no differences in outcomes between the two treatments (7). Recent research has demonstrated a clear advantage of combining exercise with manual therapy over exercise alone for the treatment of SAIS (8); it would be interesting to see a trial comparing combined manual therapy and exercise with surgical intervention for SAIS.

Based on the research, physiotherapy should be an obvious first line intervention for SAIS.


AUTHOR

REFERENCES

1. Hegedus, Eric J., et al. "Which physical examination tests provide clinicians with the most value when examining the shoulder? Update of a systematic review with meta-analysis of individual tests." British journal of sports medicine (2012): bjsports-2012.

2. Park, Hyung Bin, et al. "Diagnostic accuracy of clinical tests for the different degrees of subacromial impingement syndrome." The Journal of Bone & Joint Surgery 87.7 (2005): 1446-1455.

3. Michener, Lori A., et al. "Reliability and diagnostic accuracy of 5 physical examination tests and combination of tests for subacromial impingement." Archives of physical medicine and rehabilitation 90.11 (2009): 1898-1903.

4. Rhon, Daniel I., Robert B. Boyles, and Joshua A. Cleland. "One-Year Outcome of Subacromial Corticosteroid Injection Compared With Manual Physical Therapy for the Management of the Unilateral Shoulder Impingement Syndrome: A Pragmatic Randomized Trial." Annals of internal medicine 161.3 (2014): 161-169.

5. Ramírez, Julio, et al. "Incidence of full-thickness rotator cuff tear after subacromial corticosteroid injection: A 12-week prospective study." Modern Rheumatology 0 (2013): 1-4.

6. Dorrestijn, Oscar, et al. "Conservative or surgical treatment for subacromial impingement syndrome? A systematic review." Journal of Shoulder and Elbow Surgery 18.4 (2009): 652-660.

7. Brox, Jens Ivar, et al. "Arthroscopic surgery versus supervised exercises in patients with rotator cuff disease (stage II impingement syndrome): a prospective, randomized, controlled study in 125 patients with a 212-year follow-up." Journal of shoulder and elbow surgery 8.2 (1999): 102-111.

8. Bang, Michael D., and Gail D. Deyle. "Comparison of supervised exercise with and without manual physical therapy for patients with shoulder impingement syndrome." Journal of Orthopaedic & Sports Physical Therapy 30.3 (2000): 126-137.