Abstract
Introduction
The standard treatment of proximal humerus fractures includes pre-contoured metal plates and up to nine cortical and trabecular screws. Frequent failures are reported, especially in case of poor bone quality. The scope of this study was to assess the strength of an innovative reconstruction technique (Cement-and-screws) based on a commercial plate, with a reduced number of screws compared to the standard, and with the injection of a beta-TCP additivated acrylic bone cement (Cal-Cemex, Tecres, Italy). The focus was on a four-fragment fracture of the proximal humerus, in combination with a bone defect. For comparison, also a standard technique, based on a commercial system of plate and screws was tested (Screws-only).
Materials and Methods
Six pairs of cadaveric humeri were obtained through an ethically-approved donation program. The humeri were osteotomized to simulate a reproducible four-fragment fracture with the aid of a dedicated jig. Preparation included the simulation of a bone defect in the humeral head. One humerus of each pair was randomly assigned to one of two reconstruction techniques: (i) cement-and-screws humeri were repaired with a commercial fixation plate, 2 cortical and 3 trabecular screws (Philos, DePuy Synthes), and with injection of an acrylic cement additivated with beta-TCP (Cal-Cemex, Tecres); (ii) for comparison, screws-only humeri were prepared with the same commercial plate, 2 cortical and 6 trabecular screws. The reconstructed humeri underwent a biomechanical test. An axial force was cyclically applied, where the load magnitude started at 140 N and increased by 1% at each cycle. Failure was defined as fragment motion exceeding 8 mm.
Results
As expected, the displacement increased monotonically as the amplitude of the load increased. Progressive failure was observed in all specimens, and initiated at a force significantly lower than the final peak. The proposed cement-and-screws reconstruction was over 5 times stronger than the traditional screws-only (paired t-test, p<0.005). For all of the pairs, the failure force of the cement-and-screws reconstruction was larger than for the contralateral screws-only reconstruction.
Conclusions
The innovative repair technique based on a lower number of screws and cement injection seems very promising in terms of biomechanical strength and is a potentially alternative for the treatment of comminuted fractures.
Acknowledgements
This study was funded by Tecres SpA, Italy
