Fatty Infiltration and Rotator Cuff Atrophy

Abstract

Moderate to severe fatty infiltration and rotator cuff atrophy are commonly associated with poor clinical outcomes and failed rotator cuff repair. Numerous animal and human studies have attempted to elucidate the etiology of fatty infiltration and rotator cuff atrophy. Mechanical detachment of the tendon in rotator cuff tears is primarily responsible. Suprascapular nerve injury may also play a role. CT, MRI, and ultrasonography are used to evaluate severity. The Goutallier staging system is most commonly used to evaluate fatty infiltration, and rotator cuff atrophy is measured using multiple techniques. The presence and severity of fatty infiltration have been associated with increasing age, tear size, degree of tendon retraction, number of tendons involved (ie, massive tears), suprascapular neuropathy, and traumatic tears. Fatty infiltration is irreversible and progressive if left untreated. Slight reversal of muscle atrophy has been noted after repair in some studies. Novel therapies are currently being evaluated that may eventually allow clinicians to alter the natural history and improve patient outcomes.

Assessments of Fatty Infiltration and Muscle Atrophy From a Single Magnetic Resonance Image Slice Are Not Predictive of 3-Dimensional Measurements

“…Fatty infiltration has been shown to be distributed non- uniformly throughout the muscle belly, 8,29 challenging the rationale of using a single image to evaluate fatty infiltration. 14 Jo and Shin 30 showed that new baseline images are needed following surgical repair because surgery moves the muscle and changes its appearance in the MR image. Additionally, the large image slices (e.g.…”

“…Nevertheless, these assessment techniques are applied to identify surgical candidates. 5,7,11,14 Single-image assessments may mislead clinicians because they do not account for variation in three-dimensional muscle morphology. Both atrophy and fatty infiltration occur with aging but are separate processes 6 and the results of increased muscle atrophy without marked increases in fatty infiltration volume following a RCT support that report.…”

“…13 However, these clinical methods consider only a single image slice to view the rotator cuff muscle bellies, selected for consistency of anatomical landmarks. One image cannot fully capture morphological changes in other areas of the muscle, 14 but little work has focused on the acquisition of three-dimensional measurements of muscle morphology to evaluate whether a single image is indicative of three-dimensional muscle information. Further, the Goutallier score does not have high reliability, 15–18 suggesting that more objective methods should be used.…”

Eccentric training as a new approach for rotator cuff tendinopathy: Review and perspectives

“…Fatty infiltration and tear can be better analyzed in magnetic resonance imaging. The presence and severity of fatty infiltration have been associated with increasing age, tear size, degree of tendon retraction, number of tendons involved and traumatic tears [86] .…”

Advancements in Imaging Technology: Do They (or Will They) Equate to Advancements in Our Knowledge of Recovery in Whiplash?

“…The injured rotator cuff muscles (supraspinatus and infraspinatus in particular) show abnormal fibrosis, fatty infiltration, and changes in fat deposits on CT, MRI, and ultrasound. 66,77 These changes can be significant and may influence the outcome of the repair process. 47 While it is not known how the specific changes occur at the cellular level, in humans the SC or skeletal muscle progenitors are higher in number in partialthickness rotator cuff tears compared to noninjured and full-thickness tears.…”