Fatty infiltration of the supraspinatus: a reliability study.
BACKGROUND
The Goutallier classification of rotator cuff fatty infiltration is an accepted standard, yet no recommendations exist for which computed tomography plane is best to identify fatty infiltration of the supraspinatus. Our purpose was to determine the most reliable plane to evaluate supraspinatus fatty infiltration, assess reliability of the tangent sign, and to correlate fatty infiltration and muscle atrophy.


METHODS
Fatty infiltration in 87 computed tomography scans was reviewed by 3 shoulder surgeons using the 5-tiered Goutallier classification and a separate 3-grade scale. The supraspinatus muscle was evaluated in the axial, coronal, and sagittal plane. The tangent sign was used to assess muscle atrophy.


RESULTS
The axial plane produced the highest agreement for both the 5-tiered and 3-tiered systems. An objective radiographic marker was described to reliably determine grade 3 fatty infiltration. The tangent sign produced excellent agreement for the presence of muscle atrophy. A significant relationship between the tangent sign and fatty infiltration was discovered (P < .0001); grades 3 and 4 fatty infiltration correlated statistically with supraspinatus atrophy.


CONCLUSIONS
The tangent sign is acceptable for determining the presence of muscle atrophy and clinical decision making. A positive tangent sign is an indicator of advanced fatty infiltration. The axial computed tomography plane should be used when evaluating fatty infiltration.


METHODS
Level 3; Diagnostic study.
Williams
Matthew D
MD
Acadiana Orthopaedic Group, Lafayette, LA, USA.
Lädermann
Alexandre
A
Melis
Barbara
B
Barthelemy
Renaud
R
Walch
Gilles
G
D000273:Adipose Tissue / Q000503:physiopathology; D050154:Adiposity; D000328:Adult; D015331:Cohort Studies; D016001:Confidence Intervals; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009133:Muscular Atrophy / Q000000981:diagnostic imaging / Q000209:etiology / Q000473:pathology*; D015588:Observer Variation; D019637:Orthopedic Procedures / Q000009:adverse effects* / Q000379:methods; D011183:Postoperative Complications / Q000473:pathology*; D011336:Probability; D015203:Reproducibility of Results; D017006:Rotator Cuff / Q000601:surgery*; D000070636:Rotator Cuff Injuries; D012421:Rupture / Q000601:surgery; D012720:Severity of Illness Index; D012785:Shoulder Joint / Q000503:physiopathology / Q000601:surgery; D018709:Statistics, Nonparametric; D014057:Tomography, X-Ray Computed