Measurement Of Anatomic Parameters Of Proximal Humerus And Design Of Structural Artificial Bone For Proximal Humeral Fractures

Objective: In recent years,with the development of city construction and transportation as well as increase of the aging populations,the incidence of proximal humeral fractures shows an increasing trend.However,the treatment of these fractures effectively is a tough work to orthopaedic surgeons.Although locking plate is adopted widely to fix the proximal humeral fractures,complications related to fracture reduction and healing are not uncommon.The reason of these complications is bone defect of humeral head which is resulted by fracture compression,especially when the quality of bone is poor.To reduce the incidence of these complications,augmenter fixation is suggested.The objective of this study is to investigate the detail relevant parameters of proximal humerus,and to design an anatomic structural implant,which will assist fracture reduction and improve the stability of fixation.Methods: CT image data of shoulder of healthy adults were collected.Three-dimension proximal humerus was reconstructed by the Mimics software.After identification of the plane of anatomical and surgical neck,the central axis of the humeral head,the axis of the humeral shaft,the projection line of the central axis of the humeral head in the plane of surgical neck and the medial margin of the crest of greater tuberosity,parameters associated with the implant model were measured: angle between anatomical neck and surgical neck,distance between the highest point at anatomical neck plane and surgical neck,distance between the highest point at anatomical neck plane and the axis of the humeral shaft,the diameter of anatomical neck,the diameter of medullary cavity at surgical neck plane,the angle between the line(from the medial margin of the crest of greater tuberosity to the axis of the humeral shaft)and the projection line of the humeral head central axis.After statistical analysis,different size implant model was designed.Results: The mean angle between anatomical neck and surgical neck was 45.1°±4.0°.The mean distance between the highest point at anatomical neck plane and the plane of surgical neck was 32.2mm±3.0mm.The mean distance between the highest point at anatomical neck plane and the axis of the humeral shaft was 9.6mm±2.3mm.The mean diameter of the anatomical neck plane was 39.8mm±2.8mm.The mean diameter of the medullary cavity at surgical plane was 19.7mm±2.4mm.The mean angle between the line(from the medial margin of the crest of greater tuberosity to the axis of humeral shaft)and the projection line of humeral head central axis was 26.6°±8.0°.There was no statistical difference between left and right group.There were no differences in parameters,which related with the neck-shaft angle and the retroversion of humeral head,between male and female.However,significant differences were found in the parameters,which related with the size of proximal humerus,between male and female.Therefore,artificial bone model was divided into two kinds of size.The height of outer edge was 34 mm and the diameter of the anatomical neck plane was 41 mm for male.The height of outer edge was 31 mm and the diameter of the anatomical neck plane was 38 mm for female.Other parameters were the same,which included the angle between two planes was 45°,the angle assisting in retroversion angle reduction was 27°,the distance between the highest point of outer edge and intra medullary axis was 10 mm,the diameter of the medullary cavity was 15 mm.Conclusions: The data from this study is useful for the design of anatomic structural implant.This proximal humeral implant will help fracture anatomic reduction,facilitate fracture fixation,and simplify surgical operation.