Shoulder Impingement

Shoulder Impingement

Today we will be looking at the diagnosis of impingement.  Remember most shoulder impairments lie on a continuum of care, that is the shoulder pathology starts small with muscle imbalances, progresses secondary to biomechanical deficits, and eventually results in some type of structural damage.  

 

Subacromial impingement begins as a result of of poor biomechanics or secondary to decrease subacromial space.  Therefore, in the continuum of care it is a product of repetitive stress to the underlying tissue of the acromion process.   The official definition of the subacromial impingement is the compression from the coraco-acromial arch and the humerous.

Let’s review the most commonly injured soft tissue. 

-Supraspinatus muscle
-Long head of the bicep
-Infraspinatus
-Teres minor
-Subscapularis
-Subacromial bursa

With that being said there are two types of impingements:  Structural and functional. 

Structural impingement-A reduction in the subacomial spaces secondary to boney growth, instability, calcification, boney structure etc.

The shape of the acromion process can play a large role in structural impingement.  The acromion comes in 3 shapes or types:


Type I, flat
Type II, Curved
Type III, Hooked and most likely causing repetitive compression and irritation of the sub acromial structures

Functional Impingement: is caused by improper mechanic’s secondary to muscle imbalances, or GH instability

Functional impingement occurs because of bad mechanics, instability and poor posture that cause a decrease in space at a lower degree of shoulder movement.
Common causes include:

 

Posture
 -Forward head
 -IR humeral head
 -Protracted scap

Muscle Imbalances
 -Tight UT, Levator scap, Pec minor
 -Weak Middle and lower trap


Instability
 -Anterior Instability allows anterior translation of humeral head
Scapula Dyskinesia
 -More in depth look at Scapula mechanics can be found on Scapulae dyskinesia page here.

 

Diagnostics

Cluster Findings for Impingement
3 or greater + tests indicate +subacromial Impingement with a + LR of 2.93
 -Hawkins-Kennedy
 -Neers
 -Painful arc
 -Empty Can
 -ER resistance
To RULE OUT  High Sensitivity
- A negative Hawkins Kennedy, Neer or horizontal adduction
Other differential diagnosis
 -Drop arm sign for infraspinatus
 -Lift of test for subscapularis


Stages of impingement
Stage I:
 Edema and hemorrhage- less 25 years old
Stage II:
 Fibrotic tendon changes- 25-40 year olds
Stage III:
 Involves tendon rupture from increasing fibrotic tissues- greater then 50 y/o

Treatment

Acute; rest, ice NSAIDS

Subacute chronic: Correct muscle imbalances, posture education