JD Craik, R Malina, V Ramasamay & NJ Little

Subacromial Impingement & Rotator Cuff Tears

44% to 65% of all shoulder complaints

Two main theories:Mechanical (extrinsic) theoryDegenerative (intrinsic) theory

Anatomical Risk Factors

Type I

Type II

Type III

Bigliani Classification

Anatomical Risk Factors

AH

Coracoacromial Arch Height

Anatomical Risk Factors

AVP

Acromion Ventral Projection

Anatomical Risk Factors

AT

Acromion Tilt

Acromioglenoid Angle

AGA

Anatomical Risk Factors

CGACoracoglenoid Angle

Anatomical Risk Factors

ALP

Acromion Lateral Projection

Anatomical Risk Factors

CLP

Coracoid Lateral Projection

Anatomical Risk Factors

GV

Anatomical Risk Factors

Glenoid Version

GI

Glenoid Inclination

Anatomical Risk Factors

14 Mya

7 Mya

6 Mya

Anatomical risk factors unique or accentuated in human scapulae may play a more direct role in subacromial impingement and rotator cuff tear aetiology.

Hypothesis

Methods

Dry Bone Scapulae22 human17 gorilla

13 chimpanzee12 orangutan

Methods

Methods

Fiji Image J SoftwareMicrosoft Excel (Mac 2008)

Methods

VBL

Vertebral Border Length

Methods

Supraspinatus Area

Infraspinatus Area

Results Bigliani Classification

Type I

Type II

Type III

Bigliani Type I / II / III

0 / 8 / 4 1 / 11 / 1 4 / 13 / 0 3 / 17 / 2

Results Coracoacromial Arch Height

Increased Increased RiskRisk

mm

Results Acromion Ventral Projection

Increased Increased RiskRisk

mm

Results Acromion Tilt

Increased Increased RiskRisk

Degrees

Results Acromioglenoid Angle

Increased Increased RiskRisk

Degrees

Results Coracoglenoid Angle

Increased Increased RiskRisk

Degrees

Results Acromion Lateral Projection

Increased Increased RiskRisk

mm

Results Coracoid Lateral Projection

Increased Increased RiskRisk

mm

Results Glenoid Version

Increased Increased RiskRisk

Degrees

Results Glenoid Inclination

Increased Increased RiskRisk

Degrees

These anatomical risk factors are not unique to humans!

The extrinsic theory is not supported by these results as a primary aetiological factor

Therefore:

Results Fossa Ratio

??????

This study aimed to determine if any of the risk factors associated with impingement and rotator cuff tears are accentuated in humans

The extrinsic theory is not supported by these results as a primary aetiological factor

Reduction in Supraspinatus Fossa SizeMuscle / tendon insufficiency ?Force vector shift ?

Conclusions

Thank You