Outline. Coracoacromial Arch. Gross Anatomy. MR Anatomy. MR Anatomy. Kamath Coracoacromial Arch. Ravi S. Kamath, MD, PhD

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1 Kamath Coracoacromial Arch 6/17/2011 Outline Definitions Anatomy & variants Coracoacromial Arch Common pathology Trauma Rotator cuff Impingement Acromion variants Surgery Ravi S. Kamath, MD, PhD Division of Musculoskeletal Imaging & Intervention Department of Radiology Massachusetts General Hospital Uncommon pathology Coracoacromial Arch Gross Anatomy Smooth, inferiorly concave undersurface of the anterior acromion, coracoacromial ligament, and coracoid Forms the ceiling of the glenohumeral joint along which rotator cuff tendons gglide duringg movement MR Anatomy MR Anatomy Key components: Acromion Acromioclavicular joint Coracoacromial ligament Coracoid Subacromial-subdeltoid bursa 1

2 Kamath Coracoacromial Arch 6/17/ M with impingement Anatomic Variant Variant Normal 28M with recent trauma Coracoid Fx with Ligament Injury 28M with recent trauma Coracoacromial Ligament Tear 2

3 Kamath Coracoacromial Arch 6/17/ F with recent trauma CC Lig Tear, CA Lig Sprain 35M with distal clavicle resection Chronic CC Lig Tear, CA Lig Missing Subacromial-Subdeltoid Bursa 60F with pain, weakness Passage of cuff tendons and proximal humerus under arch is facilitated by the subacromialsubdeltoid bursa Gliding articulation lubricated by bursal and synovial fluid 3

4 Supraspinatus Tear + Bursitis 55F with rheumatoid arthritis Inflammatory Bursitis Scapulohumeral Articulation Scapulohumeral articulation can be thought of as two concentric hemispheres which together enhance shoulder stability and increase surface area for load transfer Defects in coracoacromial arch result in superior instability Rotator Cuff Rotator Cuff The supraspinatus tendon is subject to compressive loading between the humeral head and coracoacromial arch, and it provides passive resistance against superior displacement of the humeral head 4

5 Kamath Coracoacromial Arch 6/17/ M with chronic shoulder pain FT Supra Tear, CA Lig Degenerated Impingement Interval Subacromial Impingement Space between the coracoacromial arch and superior humeral head is called the impingement interval Clinical diagnosis: Anterior or lateral pain during ABER Normally narrow, more so on abduction anything that p this space p can cause impingement p g further compresses Imaging findings: AC joint j i t DJD CA ligament thickening Subacromial spur Acromial shape Subacromial-subdeltoid bursitis Impingement interval Subacromial Impingement 52M with worsening pain, wkness 5

6 Subacromial Impingement 55F with pain, decreased ROM Subacromial Impingement 55F with pain on abduction Subdeltoid Lipoma Subdeltoid Lipoma Subdeltoid lipomas can cause impingement-type symptoms due to pressure from strong tension of middle deltoid when arm is abducted, pancaking the lipoma and pushing it into the subacromial space with the bursa 6

7 60M with prior acromioplasty Absent CA Lig, Focal Bursitis Acromial Shape Biglani et al. classified the acromion into three types: Type 1: Flat, 12% Type 2: Curved, 56% Type 3: Hooked, 29% Curved (type II) and hooked (type III) acromion shapes have been associated with higher rates of bursal-surface cuff tears 58% of people have the same type of acromion on both sides Acromial Shape Type III Acromion + FT Supra Tear A fourth type (upward curved, 3%) has also been described Type 1 Type 2 Type 3 Type 4 7

8 Acromial Shape Acromial Shape More recent studies suggest that type II & III acromia are acquired rather than developmental and are caused by traction spurs of the coracoacromial ligament Spurs are thought to result from increasing dependency on the coracoacromial arch for superior stability with cuff degeneration Association has also been noted between the lateral acromial angle and rotator cuff pathology Downward sloping acromia and subacromial spurs decrease the size of the acromial interval and impinge of the rotator cuff tendons Os Acromiale Presence of an os acromiale (unfused acromial apophysis) has also been associated with rotator cuff impingement (~2x RR) Os Acromiale 1-3 acromial ossification centers appear by age and fuse by 25; failure of fusion at any synchondrosis results in an os acromiale (seen in 2.7%) >85% 7 types of os acromiale: Os acromiale Acromioclavicular joint Os Acromiale Os Acromiale With deltoid contraction, downward pull on unstable os acromiale narrows the subacromial space Osteophytes at synchondrosis can also cause impingement 8

9 Subcoracoid Impingement Subcoracoid Impingement Impingement of subscapularis tendon in the acromiohumeral interval Clinical diagnosis: Pain during flexion, adduction, int rotation Roller-wringer effect: on internal rotation, coracoid indents bursal fibers of cranial subscapularis tendon while stretching, which leads to undersurface tear Imaging findings: Coracohumeral distance < 6 mm Subscapularis tendon tear Subcoracoid bursitis Cortical irreg of lesser tuberosity Abnormalities of biceps tendon 65F with chronic shoulder pain 44M with chronic shoulder pain Subcoracoid Impingement Other Pathology Anything that can affect other osseous structures can also affect those of the coracoacromial arch tumor, infection, inflammation, metabolic disease Although these are less common causes of pain in this region, they should be considered in patients with an appropriate clinical history 9

10 20M with pain after weightlifting Distal Clavicular Osteolysis 23M with pain after weightlifting Stress Fracture 50M after AC injection in office AC Septic Arthritis 10

11 55F with asymmetric AC pain Tumoral Pseudogout 40F with pain, no recalled trauma Same patient, 2 months later Breast Cancer Metastasis 24F with history of osteosarcoma 11

12 Osteosarcoma Metastasis 12

Rotator cuff tears Acute or chronic? Mary Obele ANZSOM September 2012 Acknowledgement: ACC

Rotator cuff tears Acute or chronic? Mary Obele ANZSOM September 2012 Acknowledgement: ACC Anatomy Epidemiology Asymptomatic rotator cuff tears: prevalence is 35% (5) 15% full thickness and 20% partial