Introduction

Traditionally correction of idiopathic paediatric scoliosis is done by hybrid fixation. This involves a judicious combination of mono-axial and poly-axial screw constructs. This has inherent perceived advantages with better deformity correction and maintaining alignment without loss of correction over time.

Introduction: The aim of this paper is to biomechanically evaluate its stabilisation properties of a new retrograde device used in the þxation of proximal humeral fractures and to assess the effect of Bone Mineral Density (BMD) on its intramedullary þxation. The device incorporates a trio wire at the proximal end instead of a conventional proximal locking screw relying on it for proximal humeral segment stability. Methods: Eight fresh frozen human humeri were harvested from post mortem specimens and evaluated for Bone Mineral Density (BMD). The long axis of the nail and the rotational axis of the humerus were perfectly aligned. A 2-mm perpendicular osteotomy (fracture), 3cm distal to the distal margin of the medial joint surface represented the most rotationally unstable proximal humeral fracture. The proximal end was loaded for torque at a rate of 10û/sec. All testing was halted at failure (10% drop in recorded load). Results: The mean torque hold at failure was 1.51 ± 0.56, median 1.4 Nm-1. The mean rotation observed at failure was 32.2û ± 21.43û, median 34.3û. No signiþcant relationship was identiþed between proximal humeral bone mineral density and Failure of torque hold with the use of this particular device. Conclusions: Biomechanical data from previous similar studies are based on highly variable testing conþgurations. True comparisons are difþcult to obtain. This study shows that the trio wires deform with minimal torque. The Nail is weak in torsional control when compared to other implants available for the treatment of proximal humeral fractures.