Natural history of infraspinatus fatty infiltration in rotator cuff tears

Background/hypothesis Muscular fatty infiltration (FI) represents an important prognostic factor in rotator cuff repair. The goal of this study was to analyze the natural history of infraspinatus FI in rotator cuff tears to determine the timing of the appearance and the speed of progression of this phenomenon. Method The preoperative MRI or CT-arthrograms of 1688 patients operated for rotator cuff tears were reviewed. The degree of infraspinatus FI was correlated with the type of tendon tear, patient sex, dominant hand, presence of traumatic injury, delay between the onset of symptoms and imaging studies, and age of the patients at imaging. Infraspinatus FI was graded on axial images according to Goutallier classification and described as minimal (stage 0 or 1), medium (stage 2), and severe (stages 3 and 4). Statistical regression was used to determine the most significant factors. Results Infraspinatus FI increased significantly in presence of an infraspinatus tendon tear and when multiple tendons were torn ( P < .0005), with increasing delay between the onset of symptoms and imaging studies ( P < .0005) and increasing patient age ( P < .0005). Medium FI appeared on average 2 and a half years after the onset of symptoms, and severe FI appeared at an average of 4 years after symptom onset. Conclusion Larger tendon tears, longer delays after tendon rupture and older patient age are associated with more severe and frequent FI. Stage 2 FI appears at an average of 2 and a half years after the onset of symptoms, and surgical repair should be done within this time frame if possible.