Narrowing of the Coracohumeral Interval
- Subcoracoid impingement is ANTERIOR shoulder pain arising from narrowing of the CORACOHUMERAL INTERVAL - the space between the tip of the coracoid process and the lesser tuberosity of the humerus - in which the SUBSCAPULARIS tendon is compressed (and abraded) between the coracoid and the humeral head, often described as a 'roller-wringer' effect on the tendon.
- The interval is quantified by the CORACOHUMERAL DISTANCE (CHD) on axial (and sagittal-oblique) MRI; a narrowed CHD and increased coracoid overlap define a tight subcoracoid space, and arthroscopic decompression (coracoplasty) increases the CHD and reduces coracoid overlap.
- Causes of a tight interval include a coracoid that is congenitally/developmentally too LONG or too LATERALLY placed, and IATROGENIC/post-surgical change - particularly after coracoid-transfer stabilisation (Latarjet/Bristow) or glenoid osteotomy that brings the coracoid closer to the humerus - as well as dynamic narrowing in provocative positions.
- The provocative position reproduces pain when the shoulder is brought into FORWARD FLEXION, ADDUCTION and INTERNAL ROTATION (the coracoid impingement test), which drives the lesser tuberosity towards the coracoid; pain is anterior, over the coracoid, and may be associated with subscapularis signs (a positive belly-press or lift-off if the tendon is involved).
- There is a genuine CONTROVERSY about causation: subcoracoid impingement is classically implicated in upper-border SUBSCAPULARIS tears, but comparative MRI studies have found NO significant difference in coracohumeral distance or coracoid overlap between shoulders with isolated subscapularis tears and the opposite healthy shoulders, with coracoacromial-ligament degeneration (a subacromial process) present in most - so a narrowed interval is not proven to cause the tear, and subscapularis pathology should not be attributed to it uncritically.
- MANAGEMENT is CONSERVATIVE first - activity/biomechanical modification, physiotherapy and corticosteroid injection - reserving ARTHROSCOPIC SUBCORACOID DECOMPRESSION (CORACOPLASTY, resecting the posterolateral coracoid to widen the interval) for recalcitrant, genuinely subcoracoid pain, often combined with addressing any subscapularis tear; coracoplasty reliably increases the CHD and improves pain and subscapularis strength in selected patients.
- “Subcoracoid impingement = anterior shoulder pain from a narrowed COROCOHUMERAL interval; subscapularis pinched between coracoid tip and lesser tuberosity ('roller-wringer').
- “Quantify with coracohumeral distance (CHD) on MRI; provocative position = forward flexion + adduction + internal rotation; causes incl. long/lateral coracoid and post-Latarjet.
- “Controversial as a cause of subscapularis tears (CHD often similar to healthy side). Conservative first; arthroscopic coracoplasty for recalcitrant cases.
Anterior shoulder pain reproduced by forward flexion + adduction + internal rotation; a narrowed coracohumeral distance on MRI; possible subscapularis signs.
It is implicated in subscapularis tears but not proven to cause them - don't attribute subscapularis pathology to a tight interval uncritically.
Anatomy, Mechanism & Diagnosis
Subcoracoid impingement is anterior shoulder pain from narrowing of the coracohumeral interval - the space between the coracoid tip and the lesser tuberosity - so the subscapularis tendon is compressed between the coracoid and the humeral head (the 'roller-wringer' effect). The interval is measured as the coracohumeral distance (CHD) on axial/sagittal MRI; a narrow CHD with increased coracoid overlap defines a tight space. A tight interval may be congenital/developmental (a long or laterally placed coracoid), iatrogenic (after coracoid-transfer stabilisation such as Latarjet/Bristow, or glenoid osteotomy), or dynamic. The provocative position is forward flexion, adduction and internal rotation, which drives the lesser tuberosity towards the coracoid and reproduces anterior pain, sometimes with subscapularis signs (belly-press/lift-off).
The Causation Controversy & Management
- Be critical about causation. Subcoracoid impingement is classically implicated in upper-border subscapularis tears, but comparative MRI studies have found no significant difference in CHD or coracoid overlap between shoulders with isolated subscapularis tears and the contralateral healthy shoulder, with coracoacromial-ligament degeneration (a subacromial process) present in most - so a tight interval is not proven to cause the tear.
- Conservative management first: activity/biomechanical modification, physiotherapy, and a corticosteroid injection into the subcoracoid space (also diagnostic).
- Arthroscopic subcoracoid decompression (coracoplasty) - resecting the posterolateral coracoid to widen the interval - is reserved for recalcitrant, genuinely subcoracoid pain, often combined with repair of any subscapularis tear.
- Outcome: coracoplasty reliably increases the CHD, reduces coracoid overlap, and improves anterior pain and subscapularis strength in selected patients.
The key judgement in subcoracoid impingement is to take the diagnosis seriously as a cause of genuine anterior shoulder pain while remaining critical about its role in subscapularis tears: because comparative imaging shows that the coracohumeral distance is often no different from the healthy side and that coracoacromial (subacromial) degeneration is common, attributing a subscapularis tear solely to a 'tight' subcoracoid interval can lead to an unnecessary or insufficient operation. Confirm that pain is truly subcoracoid (anterior, provocative position, relieved by a subcoracoid injection) before offering coracoplasty, treat conservatively first, and address the subscapularis on its own merits.
Evidence & Key Studies
Effect of arthroscopic coracoplasty on subscapularis strength in subcoracoid impingement
- Subcoracoid impingement causes anterior shoulder pain; arthroscopic subcoracoid decompression (coracoplasty) is the preferred treatment in recalcitrant cases.
- Coracoplasty increased the coracohumeral distance and reduced coracoid overlap, with improvement in anterior pain, internal rotation, ASES score and subscapularis strength.
- The improvement in subscapularis strength was inversely related to the postoperative coracohumeral distance, indicating a mechanical effect of the coracoid on the subscapularis.
Is it subcoracoid or subacromial impingement that tears the subscapularis? An MRI comparison
- In patients with isolated subscapularis tears, coracohumeral distance and coracoid overlap did not differ significantly between the operated and the contralateral healthy shoulder.
- Coracoacromial-ligament degeneration (a subacromial process) was present in 75% of patients.
- These findings question whether subcoracoid narrowing is the true cause of isolated subscapularis tears, implicating subacromial factors instead.
According to PubMed, the description of subcoracoid impingement as a cause of anterior shoulder pain, the use of the coracohumeral distance and coracoid overlap, and the effect of coracoplasty (widening the interval and improving subscapularis strength) come from the cited Acan study; the finding that CHD/coracoid overlap do not differ from the healthy side in isolated subscapularis tears, and the high rate of coracoacromial-ligament degeneration that questions a subcoracoid cause, from the cited Cetinkaya study. The coracohumeral-interval anatomy, the 'roller-wringer' mechanism, the provocative position and the conservative-then-coracoplasty pathway are standard, well-established teaching. (See also our Subscapularis Tears and Subacromial Impingement topics.)
Clinical Decision Scenarios
Practise clinical reasoning and management decisions out loud
“What is subcoracoid impingement, and how would you assess a patient you suspect has it?”
“How would you manage subcoracoid impingement, and what does the evidence say about coracoplasty?”
Mnemonics & Memory Aids
CORACOID
Hook:CORACOID: narrowed interval + Overlap, Roller-wringer on subscap, Anterior pain, measure CHD, On provocative position, Iatrogenic/long coracoid, Decompress if needed.
Definition & mechanism
- Anterior shoulder pain from a narrowed coracohumeral interval (coracoid tip to lesser tuberosity)
- Subscapularis compressed between coracoid and humeral head ('roller-wringer')
- Quantified by coracohumeral distance (CHD) on MRI
Causes
- Long or laterally placed coracoid (congenital/developmental)
- Iatrogenic/post-surgical (coracoid transfer - Latarjet/Bristow; glenoid osteotomy)
- Dynamic narrowing in provocative positions
Assessment
- Provocative position: forward flexion + adduction + internal rotation
- Coracoid tenderness; subscapularis tests (belly-press, lift-off)
- MRI CHD/coracoid overlap; diagnostic subcoracoid injection
Controversy & management
- Implicated in subscapularis tears but CHD often same as healthy side - not proven causal
- Conservative first (modification, physio, injection)
- Arthroscopic coracoplasty for recalcitrant cases (+/- subscapularis repair)