Accuracy of magnetic resonance imaging in predicting the intraoperative tear characteristics of pectoralis major ruptures.

Background: Magnetic resonance imaging (MRI) is the preferred study of choice for pectoralis major ruptures. Because this is a rare injury, no large case series have evaluated the efficacy of MRI for diagnosing and characterizing pectoralis major ruptures. We hypothesized that MRI would be accurate for diagnosis of the location and grade of pectoralis major tears.

Methods: The study included 36 operative cases of pectoralis major ruptures with detailed descriptions of tear location and grade and satisfactory preoperative MRIs. Two musculoskeletal fellowship-trained radiologists interpreted the MRIs, which were then compared with the operative findings for location: tendon-bone junction or myotendinous junction, and tear grade (G): G2 (incomplete high grade partial tear) or G3 (complete tear). The sensitivity, specificity, positive predictive value, and negative predictive value were calculated.

Results: The MRI sensitivity was 1.00 for diagnosing complete G3 tears at the sternal head and clavicular head in acute ruptures. The sensitivity of MRI for diagnosing tendon-bone tears at the sternal and clavicular heads was 0.93 and 0.90, respectively. The sensitivity of MRI in diagnosing myotendinous and G2 tears diminishes, but specificity and negative predictive value remain high for sternal and clavicular head ruptures.

Conclusions: Our data support the use of MRI in diagnosing the tear grade and location of pectoralis major tendon ruptures, particularly for acute, tendon-bone, and G3 tears. The diagnostic accuracy of MRI decreases when chronic tears are evaluated. MRI remains a useful adjunct in diagnosing and guiding treatment of pectoralis major ruptures.