Partial-thickness rotator cuff tears are rotator cuff tears that lack full transmural extension from the articular to the bursal surfaces.
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Epidemiology
Partial-thickness rotator cuff tears are common and occur more often with increasing age, prevalence ranges from 4% in patients under the age of 40 years and increases up to 25% in patients over the age of 60 1.
Risk factors include overhead activity and throwing sports and they are also associated with subacromial impingement.
Diagnosis
The diagnosis can be established with characteristic imaging features on ultrasound, MRI, or CT/MR arthrography and verified arthroscopically.
Pathology
Etiology
Extrinsic factors
- internal impingement
- subacromial impingement
- glenohumeral instability
- trauma
- repetitive overload
Intrinsic factors
- hypovascularity of the distal parts of tendon and the footprint
- age-related hypocellularity and/or fascicular thinning etc.
Classification
They can be classified as follows 1-3:
- articular-sided tears: arise from the undersurface part of the tendon and communicate with the glenohumeral joint space
- bursal-sided tears: arise from the bursal surface and communicate with the subacromial-subdeltoid bursa
- intrasubstance tears: confined to the tendon they also known as concealed interstitial delamination (CID)
Cadaveric studies suggest that most partial-thickness tears are intratendinous followed by articular-sided and bursal-sided tears 4.
They can be graded based on their depth 1,2 to the rotator cuff tendon thickness:
- grade 1: <3 mm or <25%
- grade 2: 3-6 mm or 25-50%
- grade 3 : >6 mm or >50%
Radiographic features
Ultrasound
Focal hypoechoic or anechoic defect in the area of the partially torn tendon, either on the bursal or articular side with intact residual fibers 5-8.
Sensitivity and specificity is 66% and 93% when conducted by a skilled examiner 8.
MRI
Focal non-transmural defect of fluid signal intensity of the rotator cuff on fat-saturated PD or T2 weighted images, again with intact residual fibers 6-8.
Sensitivity and specificity is 64% and 92%.
CT/MR arthrography
MR arthrography is preferred over CT arthrography since it is also able to depict bursal-sided or intrasubstance tears. Sensitivity and specificity is 86% and 96%.
Intraarticular contrast will extend into the tear, particularly in the case of an articular-sided tear. The ABER (abduction external rotation) position is useful to demonstrate intratendinous extensions due to the lax tendon fibers and the contrast filling into the delaminated space 7.
Treatment and prognosis
Partial-thickness tears can be initially treated conservatively for 2-3 months. Surgery is indicated for patients, who failed conservative treatment and younger patients with a single acute injury and include debridement and repair the latter, particularly in larger tears, where more than 75% of the tendon diameter is affected 1. Subacromial decompression might be an option if there are extrinsic risk factors for subacromial impingement 1. Partial-thickness tears with intratendinous extension might need more extensive debridement or more dedicated repair.
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