Bone Hardness of Different Anatomical Regions of Human Radius and its Impact on the Pullout Strength of Screws.

Wei Chen,Guo‐bin Liu,Zu‐sheng Hu,Yan‐bin Zhu,Ying‐ze Zhang,Bing Yin,Wei‐wei Wu,Jian‐zhao Wang,Sheng Li,Xiao‐juan Zhang

doi:10.1111/os.12436

Abstract

ObjectiveTo investigate the bone hardness of different anatomical regions of the human radius and its impact on the pullout strength of screws.MethodsFresh radius bones were obtained from three donated cadavers. They were divided into three parts: proximal metaphysis, shaft, and distal metaphysis. The proximal metaphysis contains the head, neck, and radial tuberosity. The distal metaphysis includes the palmaris radius and the styloid process. The shaft of the radius was divided into nine segments of equal length. The bone hardness of three radiuses, one from each cadaver, was measured by Vickers microindentation hardness tests, and the screw pullout strength was examined in the other three radiuses using a materials testing machine. The trend between radius hardness and pullout strength was analyzed by using an analysis of variance randomized block design. Pearson correlation analysis was performed to evaluate the linear correlation between the bone hardness and the pullout strength of the human radius.ResultsThe mean hardness ranged from 33.30 HV (the head) to 43.82 HV (the diaphysis). The hardest part of the radius was the shaft, with a value of 42.54 ± 5.59 HV. The proximal metaphysis had a hardness value of 34.15 ± 6.48 HV, and the distal metaphysis hardness value was 35.24 ± 5.17 HV. The shaft was 23.5% harder than the proximal metaphysis and 20% harder than the distal metaphysis. The microhardness test demonstrated that the bone hardness value of the diaphysis was significantly higher than those of both the proximal and distal metaphysis of the radius (both P < 0.05). The mean pullout strength values ranged from 552 N (the distal metaphysis) to 2296 N (the diaphysis). The greatest pullout strength of the radius was observed for the shaft, with a pullout strength of 1727.96 ± 111.44 N. The pullout strength of the proximal metaphysis was 726.33 ± 236.39 N, and the pullout strength of the distal metaphysis was 590.67 ± 36.30 N. The pullout strength of the shaft was 138% greater than that of the proximal metaphysis and 190% greater than that of the distal metaphysis. The pullout strength was also higher in the diaphysis than at both ends of the radius (both P < 0.05). A positive correlation was found between bone hardness and pullout strength (R = 0.927, P < 0.001).ConclusionsBone hardness and screw pullout strength are higher in the diaphysis of the radius than at either end. The pullout strength is positively related to bone hardness in the human radius.

Highlights

Radial and ulnar fractures account for 6.3% of fractures of the body[1]
The Distribution of Bone Hardness in the Human Radius The bone hardness distribution of the radius is shown in Table 1 and Fig. 3
The hardness was significantly enhanced in the diaphysis than the metaphysis in the radius (P < 0.001)

Summary

Introduction

Radial and ulnar fractures account for 6.3% of fractures of the body[1]. A study reported that in the United States, distal radial fractures accounted for more than 640 000 of cases during 2001 alone, representing one of the most common types of fractures[2]. BONE HARDNESS AND PULLOUT STRENGTH epidemiology of radial fractures can help them choose the most appropriate treatment options. The influence of environmental and lifestyle factors on the risk of radial fractures has recently been evaluated to further examine the reasons for the increasing rates and to reduce the dysfunction of radial fractures, which can usually be treated by internal fixation. Implant failure as a result of screw loosening is a serious complication after internal fixation of bone fractures[3]

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Conclusion