Dynamic Compression Plating with Strategic Screw Fixation in Diaphyseal Transverse Fractures of the Radius: the Biomechanical Effect of Numbers of Screws

摘要

Introduction.Diaphyseal fracture of radius could compromise function unless adequately treated. Open reduction and internal fixation with six cortices of screw fixation on either side of the fracture is generally accepted as the best method of treatment. Unfortunately, a very high rate of refracture after plate removal has been observed for as high as up to 22%. Although a number of factors are thought to be the cause of such a high rate, such as the type of plate used, time from plating to plate removal, quality of reduction and compression achieved, type and duration of immobilization after plate removal, nevertheless, the stress riser from the screw holes is also considered as one of the important factor. In accordance with the stress riser from screw holes, number of screws introduced into bone played a very important role. The objective of this study is to biomechanically compare the load to failure between constructs for the treatment of diaphyseal transverse fractures of the radius in skeletally mature bone. Materials and methods. Sixteen skeletally mature human radii were retrieved, devoid of soft tissue including periosteum. Transverse osteotomy was done in each radius in its midpoint. In the control group, the radius was fixed with 6-holes 6-screws construct. In the test group, the radius was fixed with 6-holes 4-screws construct. All radii were fixed with 3.5mm mini Dynamic Compression Plates. They were then randomly divided into two groups, with each group consisted of four controls and four test specimens. Group I was tested in three-point bending force and group II was tested in axial compression force.Results.In the three-point bending test, the controls showed slightly higher load to failure but this value was not significant (p = 0.57). Meanwhile in the axial compression test, the test group showed higher load to failure with a p-value of 0.05 which was marginally significant.Conclusions.The 6-holes 6-screws construct showed higher load to failure when compared to the 6-holes 4-screws construct in terms of 3-point bending force although the value was not significant. In contrast, the 6-holes 4-screws construct showed a higher load to failure in terms of axial compression force and the value was deemed marginally significant. Furthermore, failure starting point in this experimental study was observed in the screw holes.