Is the pectoralis major tendon a reliable reference for restoration of humeral length with fracture hemiarthroplasty?

BACKGROUND: The primary objective was to calculate and to apply the numeric value of the distance from the pectoralis major tendon insertion to the superior aspect of the humeral head (PMTD) without any radiation exposure or equipment through basic data such as age, sex, height, and weight of Asian populations.

METHODS: We analyzed shoulder magnetic resonance images of 260 patients (107 men and 153 women; average age, 59.8 years). The superior border of the pectoralis major was identified on the transverse section and cross-referenced with the coronal section. Measurements were made inferiorly from the corresponding transverse section to the top of the humeral head superiorly in coronal view. Correlation analysis was performed between variables including the patient's age, sex, height, weight, and body mass index and the PMTD by multiple linear regression analysis.

RESULTS: The mean PMTD was 52 mm, with an average of 55 mm for men and 49 mm for women. Sex and height were significantly correlated with PMTD. The PMTD increased to a consistent level proportionally to height, and the difference in PMTD between men and women was 3.45 mm. An equation to estimate PMTD using these findings is as follows: PMTD (in mm) = 23 + (height [cm] × 0.17) + 3.45 (the last number is added for men). This equation had a prediction error of 0.3 mm.

CONCLUSION: Our study demonstrated that PMTD is a useful and reliable reference for optimal humeral height during hemiarthroplasty for proximal humerus fractures in Asian populations.