抄録
Since bone mineral density ( BMD ) and bone strength of the proximal humeral head affect the stability of the internal fixation material at the operation, we evaluated the relationship between BMD and bone strength in the proximal humeral head using cadaver humerus. The BMD of 10 cadavers humerus (mean age 79.2 ) was analyzed by XP26 ( Norland Co. ). BMD was measured at 4 regions of interest ( top is top of the humeral head, medial is the area of subchondral bone at the glenoid side, middle is the middle of the humeral head and GT is the greater tuberosity ). On the coronal plane the osteotomy was performed on the middle of the humeral head and sliced 1 cm thickness to compare the anterior slice with the posterior slice at the same region. The maximum load value was measured by the compression test using a universal material examination machine ( Instron 4505 ). Mean BMD ( g/cm2 )the top was 0.50, the medial 0.64, the middle 0.44 and the GT 0.51. The medial region was significant difference from the middle ( p < 0.05 ) . The mean maximum load value ( N ) was 347 at the top, 437 at the medial 136 at the middle and 209 at the GT. The medial was significant difference from the top and the middle ( p < 0.05 ). By comparison between the anterior slice and the posterior slice at the same region, there was significant difference at the top, the medial, the middle and GT ( p < 0.01 ). There was positive correlation between BMD and the bone strength at each region ( p < 0.05 ). Our result shows that the BMD indicates the bone strength in the proximal humeral head. To get more stability of the screws, the edge of screw must be inserted into the top or medial region at the posterior side.
