Impingement

DefinitionLateral Acromial Spur

 

Painful impingement of rotator cuff

- on anterior 1/3 of Acromion, CA ligament & ACJ

- causes tendinosis of the RC

 

Anatomy Subacromial Space

 

1.  Roof / CA Arch

- acromion

- CA ligament

- coracoid process

- ACJ is superior & posterior to CA ligament

 

2.  Floor 

- GT & superior aspect head

- rotator cuff

 

Aetiology

 

Controversial

- extrinsic and intrinsic theories

 

1.  Extrinsic / Extra-tendinous / Bursal sided tears

 

CA arch impinges on RC

- true impingement syndrome

- causes tendinosis of the cuff

 

Factors

 

A.  Subtle GH Instability

- relationship poorly understood

- respond poorly to acromioplasty

- alteration in dynamics of shoulder

 

B.  Internal Impingement Posterior / Superior Glenoid

 

Described by Davidson 1997

- throwing athletes

- impinge in abduction & ER

- SS impinges on posterosuperior rim of glenoid 

- normally humeral head translates posterior in glenoid 

- this may be lost with instability or laxity of throwing athlete

- alternatively may be caused by posterior capsular tightness

 

See Miscellaneous/Throwing Athlete

 

C. Degeneration ACJ

 

OA Spurs

 

D.  Acromion Morphology

 

Neer = impingement on anteroinferior acromion 

 

E.  Os Acromiale

- mesoacromion most common

- hypermobile unfused epiphysis

- tilts anteriorly

- 1-15% normal population

- increased incidence with impingement

 

F.  CA Ligament Spurs 

 

Develop calcium in tendon

 

G.  CA Ligament Impingement

- common

- "Snapping shoulder"

- in flexion & IR

- SS & Biceps impinge on it

- Neer recommends division

 

H.  Coracoid Impingement

- less common

- subscapularis impingement between coracoid and LT

- may be exacerbated by anterior instability

- more medial pain with arm flexed, adducted and IR

- find SSC partial tears on arthroscopy

 

Coracoid Impingement Lateral Coracoid

 

2.  Intrinsic / Intra-tendinous / Articular sided tears

 

2° to bursal thickening or intrinsic problem in cuff

- ? Now thought to be most common

 

Factors

 

1. Muscle Fatigue

- overloaded weak muscles

- eccentric tension load

- associated with proximal humeral migration

 

2. Shoulder Overuse

- soft tissue inflammation

- repetitive microtrauma

- athletes / manual labourers

 

3. Degenerative Tendinopathy

- 1° intrinsic degeneration of RC

- ? hypovascularity

- increasing incidence with age

 

Pathology

 

Impingement Zone 

- centered on supraspinatus tendon insertion

- Codman's "Critical Zone" 1cm from insertion

- zone of hypoperfusion

 

Neer's Pathological Classification

 

Stage I

- reversible

- oedema & haemorrhage

- < 25 years

 

Stage II

- irreversible change

- fibrosis & tendinitis

- 25-40 years

 

Subdivided by Gartsman

- Stage IIA = No tear

- Stage IIB = Partial thickness tears

 

Stage III

- > 40 years

- chronic

- partial & full thickness tears

 

Acromial Morphology

 

Bigliani / Assess on Supraspinatous Outlet View / Scapula Lateral

 

Type I:  Flat

- 20% of normal population

 

Type 1 AcromionType 1 Acromion

 

Type II:  Curved

- 40% of normal population

 

Type 2 Acromion

 

Type III:  Hooked

- 40% of normal population

- 80% of RC tears

 

Type 3 AcromionAcromion Type 3Acromial Spur Type 3

 

Cadaver study

- 30% of all cadavers had a full thickness cuff tear

- 75% type III & 25% type II & 3% type I

 

Morphology does change with age

- Spur more common > 50 years

- ? 2° event to cuff process

- most hooks appear to be acquired & lie in CA ligament 

 

Symptoms

 

Painful arc

 

Weakness overhead

 

If < 40 years look for instability

 

Examination

 

Painful Arc

- 70-120°

- > 120° - ACJ OA / terminal phase pain

 

IR

- limitation of IR may suggest posterior capsular tightness

 

Neer Impingement Sign

- stabilize scapula from behind patient

- passively elevate arm in scapula plane

- pain between 70-120°

 

Hawkins Modification

- IR humerus at 90° flex

 

Neer Impingement Test 

- LA in SAD

- abolish pain & test for cuff tear / weakness

 

Always

- anterior apprehension / Jobes relocation (young patient)

- ACJ assessment

- biceps assessment

- NVI

- C spine

 

X-ray

 

AP view (True AP)

- acromio-humeral interval:  Normal 1-1.5 cm, < 0.7cm abnormal

- sclerosis greater tuberosity / acromion

- lateral Acromion spur

- OA ACJ

 

Acromial Spur AP

 

Axillary Lateral

- os acromion

- bone scan to exclude symptomatic hypermobility

 

Os Acomionale Axillary Lateral Xray

 

Supraspinatus Outlet View

- Acromion morphology / calcification Coraco-Acromial Ligament

- scapula lateral variant

- plate on affected shoulder, other turned out of way 

- 10° caudal

 

Scapular Lateral for Acromial Morphology

 

Zanca view

- ACJ

- half voltage / centred on ACJ / 10o cephalad

 

US

 

Diagnose

- dynamic impingement

- bursitis

 

Shoulder Ultrasound Bursitis

 

MRI

 

Sensitive

- assess acromial morphology

- look for tendinosis / tears

 

MRI Type 3 Acromion

 

Management

 

Non Operative

 

HCLA injection 

 

Goals

- decreases pain & inflammation

- diagnostic

 

Alvarez et al Am J Sports Med 2005

- RCT HCLA v LA in RC tendonosis

- no clinical difference between the two groups

 

Cuff Rehabilitation

 

Rockwood 3 Stages of Physio

 

1. Decrease Inflammation / Increase ROM

- rest

- gentle ROM 

- posterior capsular stretches

- scapula & trunk stabilisers

- modify activities

- NSAIDS

 

2. Cuff Stabilisation and Balancing

- strengthen humeral depressors

- work on SSC and IS

- takes load off SS

- theraband / IR / ER exercises

- avoid abduction drills

 

3. Deltoid strengthening

- task specific exercises

 

Operative Management

 

Acromioplasty

 

Theory

 

Believe primary problem is extrinsic impingement

- abnormal acromial morphology on outlet view

- spurs in CA ligament

 

Results

 

Ketola et al JBJS Br 2009

- RCT of patients with impingement

- treated with exercise program or acromioplasty + exercise program

- no difference between the two groups

 

Henkus et al JBJS Br 2009

- RCT of bursectomy alone v bursectomy + acromioplasty

- no difference between the two groups

 

Open v Arthroscopic Acromioplasty

 

Results

 

Sachhs JBJS 1997

- open v arthroscopic

- open longer return to work & in hospital stay

- results similar

 

Davis et al Am J Sports Med 2010

- meta-analysis of open v arthroscopic acromioplasty

- no significant difference in outcome

- longer return to work and inpatient stays