What Can We Learn From Imaging About Rotator Cuff Tears?
Authors: Jin-Young Park
References: Presented at ICSES 2010
Pathology of the rotator cuff influences both the tendon and corresponding muscle. In case of full-thickness tear can result in retraction of the muscle belly and its tendon. And this phenomenon can lead to change in the pennation angle between the muscle fiber and the subsequent development of fatty infiltration. Goutallier et al. defined the severity of fatty infiltration using CT scan for the rotator cuff muscle (Surgery of the Shoulder 1990). Fuchs et al. reported good interoberver reliability for the grading fatty infiltration according for the MRI (JSES, 1999). In the pathogenesis of fatty infiltration change of the pennation angle of the infraspinatus after tendinous retraction is a key event (Gerber, JSES 2009). For the atrophy of the supraspinastus tangent sign and scapular ratio is useful (Zanetti, Invest Radiol, 1998).
US is useful for the detection of the rotator cuff tear although sensitivity & specificity is little bit lower in US. MRI following routing shoulder US was requested in 5.2% of the full thickness rotator tears (Rutten, Eur Radiol 2010). The diagnosis of small partial-thickness tear is restricted because of difficulties in the differentiation among fiber tearing, tendinosis, synovitic change and superficial fraying at tendon margin (Waldt, Eur Radiol, 2007). US being a dynamic study and better tolerated by the patients, can be used as the first-line investigation for the detection of full-thickness RCT and and follow-up of repair (international Sh J, Naqvi, 2010; Clin Orthop, Park, 2010). US can depict fatty infiltration and atrophy of the rotator cuff as reliably as MRI (Khoury, Am J Roentgenol, 2008; Strobel, Radiology, 2005).
For the clinical relevance of the fatty infiltration, the progression of fatty infiltration is faster in rotator cuff tears that a traumatic and involve more than one tendon with moderate (Stage 2) fatty infiltration appearing at an average of 3 years after onset of symptoms (Melis, JSES, 2010). And larger tears result in more rapid onset of fatty infiltration and to more severe degree (Bernageau, Sauramps Medical, 1993; Melis, JSES, 2010).
Practically, Even though all rotator cuff tears are not necessarily treated surgically, asymptomatic tears are usually small, becoming symptomatic as their size increases. Rotator cuff repair should be performed before the appearance of fatty infiltration (Stage II) and atrophy (positive tangent sign) and as soon as possible in older patients when the tear involves multiple tendons.