The supraspinatous has five layers, but mainly functions as two layers: joint surface fibres and bursal surface fibres
Overuse or misuse of any tendon leads to accelerated apoptosis and to what has been called 'degeneration'.
Changes within the tendon which do not lead to symptoms may be referred to as tendinosis. When symptoms develop, the term tendinopathy is used.
Impingement plus weakness suspicious for tear
Leading edge:younger and more often symptomatic. Midsubstance: older may be asymptomatic
Partial tears affect one fibre group, joint or bursa, or can occur as an interstitial defect between them (CID lesion)
Tears can be linear, L or U shaped
MRI is less reliable in the diagnosis of tendinopathy. The signs described include signal alteration with loss of the normal low signal on T1 weighted images, diffuse increase signal on T2 weighted images and alterations in tendon dimension. A wide inter and intra observer variation has been described with all of these. This is particularly the case with signal alterations on T1 weighted images. Similar alteration can be seen with variation in muscle tendon interdigitation and signal changes induced by the magic angle phenomenon. The latter are particularly problematic on short TE images
Abnormal only in late stages
Look for acromiohumeral impaction
and secondary cuff arthropathy
Normal acromiohumeral distance approximately 1 cm but depends on radiographic projection
Also look for calcification and x-ray as symptoms can mimic rotator cuff tear
In your MRI report describe:
Tear location
Tear shape (as best you can)
Tear size (medial lateral measurement and ant-post (larger lesions will extend into infraspinatus)
State of remaining tendon and muscle. Grade 0 is normal, some fatty streaks grade 1. Grade 2 = Muscle > Fat, grade 3 = Muscle = Fat, grade 4 > Fat > Muscle.
A full thickness tear is diagnosed when high signal is seen to completely traverse the tendon on T2 weighted or fat saturated images.
Look carefully at the leading edge right up to the biceps tendon
Leading edge tears are easy to miss
Using a cross reference facility on a workstation, can help with diagnosis of smal tears
Joint surface partial tears (JSPT) often begin at the medial point of the tendon attachment (footprint) and undercut in a linear fashion. This type is called a 'Rim-Rent' tear or PASTA lesion
Reverse rim rent lesions are the same but involve the bursal surface
Use both axial and coronal images for diagnosis
US gives excellent visualisation of internal tendon structure
Look for loss of normal architecture and decide if it involves one or both surfaces
Dynamic assessment with movement can be helpful as tendons move dofferently to tear debris
Bone irregularity at the footprint is a good clue as often indicates an abnormal tendon
