Biomechanics Of Rotator Cuff Tears Flashcards
What is the term used to describe when two or more muscles acting in different directions influence the rotation of a joint in a specific region?
Force coupling
What two planes does force coupling occur in?
Coronal and transverse planes
Describe the mechanism of the coronal force couple?
The coronal force couple occur from contraction of the deltoid and supraspinatus muscles . This compresses the humerus into the glenoid Fossa during abduction
Describe the mechanism of force coupling in the travers plane?
The Subscapularis and infraspinatus muscles play a synergistic role in concavity compression.
What muscles of the rotator cuff play the largest role in force coupling?
Subscapularis and infeaspinatus play the largest role
What percentage of rotator cuff strength comes from the Subscapularis?
53%
What percentage of rotator cuff strength comes from the Infraspinatus?
22%
What percentage of rotator cuff strength comes from the supraspinatus?
14%
What percentage of rotator cuff strength comes from the Teres minor?
10%
What rotator cuff muscles is responsible for the most strength and stability of the rotator cuff?
Subscapularis at 53%
While all the other 3 which are responsible for 47%
What does passive range of motion mean?
Passive range of motion can be defined as what is achieved when an outside force, such as a therapist, causes movement of a joint.
What does active range of motion mean?
Active range of motion is what can be achieved when opposing muscles contract and relax, resulting in joint movement.
What are the results from a massive tear of a posterior superior rotator cuff tear?
Results in super physiological passive internal rotation.
What are the results from a massive tear of a anterior superior rotator cuff tear?
Decrease passive external rotation and increased movement in passive internal rotation
Loss of integrity of the anterior superior rotator cuff lead to weakness in _____________?
Active internal rotation and increased movement in active external rotation
What is tear propogation
The spreading of a tear as a result from imbalanced force coupling .
What is pseudoparalysis?
Inability to perform more that 90deg of active forward elevation with fully intact passive range of motion in the absence of neurological impairment
Patients are at a higher risk of pseudoparalysis if which structures are completely disrupted?
The subscapularis or all three posterior superior muscles
What nerve is impinged when you have a large posterior superior tear?
Suprascapular nerve , which leads to degeneration supraspinatus and Infraspinatus
What are extrinsic factors that cause rotator cuff tear?
Impingement and demographic
What are intrinsic factors that cause rotator cuff tear?
Age related degeneration, hypovascualrity, inflammation and oxidative stress
What is the majority cause of rotator cuff tears? Gradual onset or acute injury?
Gradual onset
Is surgical intervention typically required for partial or incomplete tears?
No
What are the characteristics of a rotator cuff tear?
Size, depth, retraction,acromiohumeral interval, goutallier classification and contaminant pathology
What is the goutallier classification ?
See photo
Tears generally affecting less that <50% typically treated with good results of
Debriefing without/with acromioplasty
When tear depth is great than >50%
Surgical intervention focusing on repair is successful
