Tetracycline labeling as a measure of humeral head viability after 3- or 4-part proximal humerus fracture

Hypothesis: Specifically located humeral head biopsies from three-part proximal humerus fractures taken at the time of hemiarthroplasty will show greater tetracycline labeling under fluorescent microscopy than those biopsies taken from four-part fractures. Additionally, biopsies from younger patients would show greater fluorescence than older patients. Material and methods: Nineteen consecutive adult patients (range 43-83 years) underwent hemiarthroplasty as definitive treatment for 20 displaced three- and four-part proximal humerus fractures after having received 500mg of tetracycline hydrochloride orally every six hours for the immediate five preoperative days. Humeral head biopsies were taken from four pre-determined locations intraoperatively. The biopsies were prepared and analyzed with fluorescent microscopy. Results: All specimens in each biopsy location demonstrated fluorescence. There was no difference between the mean rank gray values for the four biopsy locations (p = 0.78 with the Friedman test). There was no difference between the mean rank gray values for the four biopsy locations when analyzed according to three-part vs four-part fracture (p > 0.05 with the Mann-Whitney test). There was an inverse relationship between age and fluorescence for the anterosuperior biopsy location (p = 0.033 with Spearman correlation). Discussion: Vascular supply is preserved in displaced three- and four-part proximal humerus fractures. With intact vascularity to the humeral head, head-preserving techniques utilizing stable, site-specific fixation and minimal dissection should be considered in the treatment of displaced three- and four-part proximal humerus fractures. Conclusion: Vascular supply is preserved in displaced three- and four-part proximal humerus fractures, especially in younger patients in the anterosuperior aspect of the humeral head. Level of evidence: Basic Science Study.