Study on the two-dimension method measuring the humeral head retroversion angle with multi-slice spiral CT

Objective:To investigate the two-dimension method measuring the humeral head retroversion angle with multi-slice spiral CT and emphasize on discuss humeral head retroversion angle distal reference axis effect on measure value.Methods:51 dry humerus specimens were scanned with 16-slice spiral CT scanner.The humeral head retroversion angle was defined as the angle between the humeral head central axis and a line between the epicondyles or between the humeral head central axis and the tangent to the anterior surface of the distal humerus articulation with the forearm.The distal reference axis of the humeral head retroversion angle was defined by three different levels, the total six-group data on humeral head retroversion angle were analyzed by Statistics.Results:The humeral head retroversion angle ranged from 4° to 59.8°, the humeral head retroversion angle of six groups were(27.9±11.9)°,(29.2±11.2)°,(30.2±10.7)°,(27.3±10.3)°,(26.3±10.2)°,(25.8±10.4)° respectively.The Statistics showed that there was bigger the humeral head retroversion angle defined by the tangent to the anterior surface of the distal humerus articulation with the forearm, the more distal end of humerus;on the contrary, There was the smaller humeral head retroversion angle defined by a line between the epi-condyles, the more distal humerus.The humeral head retroversion angle defined by two reference axis of the distal humerus of inferior level had significant difference, there was not significant difference on the humeral head retroversion angle defined by the other two lev-els.Above them , the mean of the humeral head retroversion angle of superior level defined by the other two methods was near.The dif-ference value was 0.6°.Conclusions:The humeral head retroversion angle is markedly variable, the design of humeral head retroversion angle of shoulder prosthesis should be individual.The reference section of the distal humerus for two-dimension method measuring the humeral head retroversion angle with multi-slice spiral CT shows the deeper olecranoid fossa and distinct anterior surface of the distal humerus.