Myotendinous junction tears of the pectoralis major are occurring more frequently and discrepancies exist between intraoperative and radiographic assessments.

Background: Pectoralis major (PM) tears have been shown to occur most frequently at the tendinous humeral insertion. However, no substantial updates on tear location have been published in 20 years or are based on relatively small sample sizes. The primary purpose of this study was to evaluate PM tear location based on magnetic resonance imaging (MRI). A secondary purpose was to evaluate agreement between MRI and intraoperative assessments of tear characteristics. We hypothesized that PM tears at the myotendinous junction (MTJ) occur at a higher rate than previously reported and that intraoperative and MRI assessments would demonstrate agreement in at least 80% of cases. Materials and methods: An observational study of consecutive patients evaluated for a PM tear at a single institution between 2010 and 2022 was conducted. Patient demographics as well as MRI and intraoperative assessments of tear location, extent of tear, and muscle head involvement were collected from the electronic medical record. Agreement was calculated by comparing radiographic and intraoperative assessments per variable and reported as percentages. Data and statistical analysis were performed with SPSS software with a significance level set to P < .05. Results: A total of 102 patients were included for analysis. Mean age was 35.8 ± 10.5 years and mean body mass index was 29.4 ± 4.8 kg/m2. 60.4% of the study population had tears of the MTJ, 34.9% of the tendinous humeral insertion, and 4.7% within the muscle belly, as determined intraoperatively. Complete tears had significantly higher agreement between MRI and intraoperative assessments relative to partial tears (83.9% and 62.5%, respectively; P ≤ .01). Discussion: The majority of PM tears occurred at the MTJ. Preoperative MRI and intraoperative assessments agreed in 80% of cases, a value that was significantly higher for complete over partial tears. These findings demonstrate that tears of the MTJ are increasingly more common and support the use of MRI in preoperative planning for complete PM tears.