Effect of calcium triphosphate cement on proximal humeral fracture osteosynthesis: a cadaveric biomechanical study

Purpose. To evaluate the effect of filling a central humeral bone void with calcium triphosphate cement on the strength and stability of an osteosynthesis in elderly cadavers. Methods. 14 fresh cadaveric shoulder specimens obtained from 11 donors (mean age, 91.5 years; mean body weight, 61 kg) were divided into 2 age-and sex-matched groups. A standardised 3-part proximal humeral fracture with a central bone void was created in each specimen. Each specimen was reduced and fixed with a locking plate. In half the specimens the central bone void was packed with calcium triphosphate cement. The intra-fragmentary motion and the load and mode of failure were recorded. Results. Respectively in the test group and controls, the intra-fragmentary motion was 1.0 and 6.4 mm, and the peak displacement at the 500 N load was 1.8 and 9.1 mm. The Cohen's d was 1.6 to 2.7 for all load steps, indicating a large effect of the calcium triphosphate cement on strength and stability. The mean difference in the failure load was 300 N (p<0.05). Conclusion. Construct stability and failure load improved significantly when the central humeral bone void was filled with calcium triphosphate cement.