PROXIMAL HUMERUS FRACTURE: A BIOMECHANICAL STUDY COMPARING FIXATION WITH POLARUS AND EUROPEAN HUMERAL NAIL VS PHILOS VS CONVENTIONAL PLATES

Abstract

Aim: To compare of strength of constructs using the newer and part specific nail systems: Polarus and European Humeral Nail with that using PHILOS and Conventional plate systems in a simulated 2-part fracture of proximal humerus, in an osteoporotic bone model.

Materials and Methods: A Biomechanical laboratory study was undertaken. Third generation composite Humerus model was used, with short e-glass epoxy fibres forming cortex and polyurethane cancellous core. Low-density polyurethane core (1.2gm/cc) was used to simulate an osteoporotic model. Osteotomy at surgical neck of humerus was carried out to create 2-part fracture of proximal humerus. Samples were fixed using one of the implants- the Polarus nail, the European Humeral Nail, PHILOS Plate, Clover Leaf Plate or T-Plate. Following fixation samples were placed in a custom made jig to fix proximal and distal ends without interfering with implants and osteotomy site. All samples were subjected to cyclical torque, torque to failure, cyclical compression and Compression loading to failure.

Results: The two Nail systems that are specifically designed for fixation of proximal humerus fracture provided significantly better fixation in all the test modalities. PHILOS construct shows less plastic deformation in cyclical torque and cyclical compression when compared to the other plates but the 2 nail systems were far superior. Locking screws did not ‘back off’ in any of the experiments involving the Polarus, European Humeral Nail and PHILOS construct, however ordinary screws used with the conventional plates did back off both in ‘torque and compression’ testing.

Conclusions: Polarus and European Humeral Nail constructs provide better stability in torque and compression as compared to PHILOS, which in turn is a more stable construct in comparison to conventional plating devices.