Poster 385: Discrepancies Exist Between Intraoperative and Magnetic Resonance Imaging Assessments of Partial Pectoralis Major Tears

OBJECTIVES: Existing literature regarding pectoralis major tear location demonstrating tendinous insertion on the humerus tears has not been substantially updated in 20 years or is based on small sample sizes. While intraoperative confirmation of tear characteristics ultimately guide surgical decision making, a preoperative MRI is almost universally obtained, warranting assessment of the utility of MRI to accurately characterize pectoralis major tears. The purpose of this study was to evaluate the location of pectoralis major tears as well as determine the degree of agreement between MRI and intraoperative assessments. We hypothesized a large proportion of myotendinous junction tears and that intraoperative and MRI assessments would be in agreement. METHODS: An observational study of consecutive patients undergoing pectoralis major repair at a single multicenter institution between 2007 and 2021 was conducted. Patient demographics as well as MRI and intraoperative assessments of tear location, extent of tear (whether complete or partial), and muscle head involvement were collected from the medical record (MR). Descriptive statistics pertaining to location of tear (muscle belly, myotendinous junction, insertion on humerus) as well as agreement between MRI and intraoperative assessments were tabulated and reported as percentages. RESULTS: A total of 73 (72 male, 1 female) individuals with pectoralis major tears undergoing operative repair were included for analysis. The mean age was 35.0 ± 10.7 years and mean BMI of 29.0 ± 4.8 kg/m(2). Of the 73 tears, 44 (60.3%) were complete, sternal/ sternocostal head tears, 12 (16.4%) were partial, sternal/ sternocostal head tears, 11 (15.1%) were complete, sternocostal and clavicular tears, and 6 (8.2%) were partial, sternocostal and clavicular tears. Complete tears at the sternal/ sternocostal head had a 90.9% agreement on extent of tear and 93.2% on muscle head involvement between MRI and intraoperative assessments. Complete tears at the sternocostal and clavicular heads had a 90.9% agreement on extent of tear and 63.6% on muscle head involvement. Partial tears at the sternal/ sternocostal head had a 50% agreement on extent of tear and 83.3% on muscle head involvement. Partial tears at the sternocostal and clavicular heads had a 33.3% agreement on extent of tear and 50% on muscle head involvement. Overall, we found 79.5% agreement on tear location, 79.5% agreement on whether the tear was complete or partial, and 83.6% agreement on muscle head involvement between MRI and intraoperative assessments. Regarding tear location, 52.1% of the study population had tears at the myotendinous junction, 45.2% at the tendinous insertion on the humerus, and 2.7% within the muscle belly, as determined intraoperatively. CONCLUSIONS: The majority of pectoralis major tears occurred at the myotendinous junction, as confirmed intraoperatively. Given that tear patterns correlate with mechanisms of injury and that studies published at least 20 years ago report a vast majority of tears at the tendinous insertion on the humerus, our findings may reflect changes in population-wide physical activities. Specifically, the increasing popularity of activities that add strain to the pectoralis major muscle may contribute to the increasing rate of MTJ tears. Additionally, preoperative analysis with MRI agreed with intraoperative findings in approximately 80% of cases. However, agreement between MRI and intraoperative assessments was substantially higher for complete tears than partial tears, which aligns with existing literature. We report that a large proportion of pectoralis major tears occur at the myotendinous junction and support the use of MRI in preoperative planning for complete pectoralis major tears.