Shoulder impingement syndrome (subacromial pain syndrome)

  • Impingement syndrome (also referred to as subacromial impingement and subacromial pain syndrome) is marked by shoulder pain that occurs on top of the shoulder joint beneath the acromion. The pain typically occurs when the arm is raised above shoulder level. See illustration of subacromial space.
  • Impingement syndrome accounts for up to 70% of all shoulder pain syndromes and is a leading indication for shoulder surgery
  • The proposed mechanism for impingement syndrome is mechanical contact between the supraspinatus tendon and the acromion that occurs when the acromion forms bone spurs and other arthritic changes
  • Patients with impingement syndrome and shoulder pain often have MRIs done. The MRI may show degenerative changes, partial thickness rotator cuff tears, and/or abnormalities in the subacromonial bursa. These findings are also common in patients without shoulder pain.
  • The condition is often treated with physical therapy and/or steroid injections. If these modalities fail, arthroscopic subacromial decompression surgery where bone spurs and involved soft tissue are surgically removed may be performed. [2]

Surgery vs Sham Surgery vs No Treatment for Shoulder Impingement Syndrome, Lancet (2017) [PubMed abstract]
  • A study published in the Lancet enrolled 313 patients with impingement syndrome
  • Main inclusion criteria: Subacromial pain of at least 3 months’ duration with intact rotator cuff tendons | Completion of a non-operative management program that included both exercise therapy and at least one steroid injection
  • Main exclusion criteria: Full-thickness torn rotator cuff (partial-thickness tear was allowed)
  • Baseline characteristics: Average age 53 years | Average number of shoulder injections received - 2 | Average Oxford Shoulder Score - 26
Patients were randomized to one of three groups:
  • Group 1 (106 patients): Arthroscopic subacromial decompression surgery
  • Group 2 (103 patients): Sham surgery
  • Group 3 (104 patients): No treatment
  • The sham surgery group had arthroscopy performed but no removal of bone or soft tissue was performed
  • Study was performed at 32 hospital sites with 51 participating surgeons
  • Patients in the Groups 1 and 2 received postoperative physical therapy but Group 3 did not
PRIMARY OUTCOME: Oxford Shoulder Score (0 [worst] to 48 [best]) at 6 months, analysed by intention to treat
During follow-up, the following was seen:
  • Primary outcome (6 months): Group 1 - 32.7, Group 2 - 34.2, Group 3 - 29.4 (1 vs 2 p=0.31 | 1 vs 3 p=0.019 | 2 vs 3 p=0.0014)
  • Primary outcome (12 months): Group 1 - 38.2, Group 2 - 38.4, Group 3 - 34.3 (1 vs 2 p=0.85 | 1 vs 3 p=0.020 | 2 vs 3 p=0.019)
  • In Group 1, 21% of patients had not received surgery at 6 months. At 12 months, 16% had not received surgery.
  • In Group 2, 11% of patients had received some type of shoulder surgery (non-sham) and 31% had not received any surgery (sham or real) at 6 months. At 12 months, 11% of patients had received some type of shoulder surgery (non-sham) and 22% had not received any surgery (sham or real).
  • In Group 3, 11% of patients had received some type of shoulder surgery at 6 months. At 12 months, 24% of patients had received some type of shoulder surgery.
  • In a per-protocol analysis, there was no significant difference between Group 1 and Group 2 at 6 months (p=0.69) and 12 months (p=0.35)
Findings: Surgical groups had better outcomes for shoulder pain and function compared with no treatment but this difference was not clinically important. Additionally, surgical decompression appeared to offer no extra benefit over arthroscopy only. The difference between the surgical groups and no treatment might be the result of, for instance, a placebo effect or postoperative physiotherapy. The findings question the value of this operation for these indications, and this should be communicated to patients during the shared treatment decision-making process.

Professional guidelines
  • In 2019, the British Medical Journal made a strong recommendation against surgery for impingement syndrome
  • The recommendation said nonoperative management including physical therapy, NSAIDs, exercise, and steroid injections should be used instead - BMJ recommendation

StraightHealthcare analysis:
  • This study showed that subacromial decompression surgery was no better than sham surgery for impingement syndrome. Both surgery groups were better than no treatment, but this is likely due to the placebo effect of surgery and/or the extra physical therapy that the surgical groups received.
  • Over the course of the study, a significant number of patients did not receive their assigned treatment, but this was mostly due to subjects not having surgery which indicates that pain and function improved without intervention in a number of people. Only 11% of subjects in Group 2 were true crossovers (received non-sham surgery) at 6 and 12 months. A per-protocol analysis also found no significant effect of surgery.