BackgroundThe extent of fatty infiltration and rotator cuff (RC) atrophy is crucial for the clinical results after rotator cuff repair (RCR). The purpose of this study was to evaluate changes in fatty infiltration and RC atrophy after revision RCR and to correlate them with functional outcome parameters.MethodsPatients who underwent arthroscopic revision RCR for symptomatic recurrent full-thickness tear of the supraspinatus tendon between 2008 and 2014 and were retrospectively reviewed with a minimum follow up of 2 years. Magnetic resonance imaging (MRI) was performed pre- and postoperatively to assess 1) tendon integrity after revision RCR according to Sugaya classification, (2) RC atrophy according to Thomazeau classification, and (3) fatty infiltration according to Fuchs MRI classification. Constant score (CS) and the American Shoulder and Elbow Surgeon (ASES) score were used to correlate functional outcome, tendon integrity, and muscle degeneration.Results19 patients (17 males and 2 females) with a mean age of 57.5 years (range, 34 to 72) were included into the study at a mean follow-up of 50.3 months (range, 24 – 101). At final evaluation, 9 patients (47%) presented with intact RCR and 10 patients (53%) suffered a re-tear after revision repair. No progress of fatty infiltration was observed postoperatively in the group with intact RC, atrophy progressed in only 1 out of 9 patient (11%). Fatty infiltration progressed in 5/10 patients (50%) and RC atrophy increased in 2/10 patients (20%) within the re-tear group. CS (42.7 ± 17.7 preop, 65.2 ± 20.1 postop) and ASES (47.7 ± 17.2 preop, 75.4 ± 23.7 postop) improved significantly from pre- to postoperatively (p< 0.001). A positive correlation between fatty infiltration and RC integrity was detected (r = 0.77,p< 0.01). No correlation between clinical outcome and tendon integrity or RC atrophy was observed.ConclusionArthroscopic revision RCR leads to reliable functional outcomes even in case of a recurrent RC retear. An intact RCR maintains the preoperative state of fatty infiltration and muscle atrophy but does not lead to muscle regeneration.Level of evidenceLevel IV; Therapeutic study.