山田 光子

Background: Treatment of proximal humeral fractures is very challenging in elderly patients with osteoporosis. To get the good stability at the fracture site we need to know the suitable region to insert screws. We examined cadavers' proximal humeral heads to know the difference of bone mineral density (BMD) and pull out strengths of screws at each region.<BR>Methods: 16 cadavers' humeri (mean age 85 years old) were used. In the humeral head we decided region 1; 30 degrees above the medial surgical neck, 2;60 degree above the medial surgical neck, 3; GT, 4: the medial surgical neck, 5: the lateral surgical neck, 6; 1 cm medial side from 4, 7; 1cm medial side from 5. BMD on each region was measured by DEXA. We inserted 2 screws; one was inserted into region 1, the other was inserted into region 7. The pull out strength of screws was measured using the universal material examination machine.<BR>Results: The mean BMD(g/cm²) at each region was 1; 0,268, 2; 0,184, 3; 0,119, 4; 0,102, 5; 0,037, 6; 0,122, 7; 0,059. The mean maximum pull out strength(N) at each region was 1; 296, 6, 7; 92,6. Concerning the pull out strength of screws region 1 was significantly higher than 7(p < 0.001).<BR>Conclusion: Our result shows that BMD and pull out strength of screws are different in the proximal humeral head. During operation we should consider the above result and insert screws into the subchondral bone 30 degrees up from the surgical neck to get good stability at the fracture site.

Treatment of proximal humeral fractures is very challenging in elderly patients with osteoporosis. To get the good stability at the fracture site we need to know the suitable region to insert screws. We examined cadavers` proximal humeral heads to know the difference of bone mineral density (BMD) and bone strength in this study.<BR>(Method) 6 cadavers humerus (mean age 84,1) were used. BMD was measured by DEXA. On the coronal plane the osteotomy was performed on the middle of the humeral head and sliced 1 cm thickness. Then we made two lines. One was the humeral shaft line which passed the greater tuberosity(GT), the other was the surgical neck line. We decided region A; medial surgical neck, B; 30&deg; above A , C; 60&deg;above A, D; GT, E: lateral surgical neck, F; 1 cm medial side from B, G; 1cm medial side from C. The maximum load value was measured at the each region of each segment by the universal material examination machine ( Instron 5882 ). Mean BMD at each region were A; 0.12, B; 0.24, C; 0.14, D; 0.12, E; 0.7, F; 0.15, G; 0.1. Mean maximum load value at each region were A; 140N, B; 348N, C; 253N, D; 147N, E; 99N, F; 161N, G; 45N. Concerning BMD value B was significantly higher than all regions except C. And C was significantly higher than ADEG. Concerning the mean maximum load value B was significantly higher than A,C,D,E,F and G( p < 0.05 ). C was significantly higher than A,D,E,F and G( p < 0.05 ). D, D and F were significantly higher than G( p < 0.05 ). Our result shows that BMD and the bone strength is different in the proximal humeral head. During the operation we should consider the above result and insert screws 30 degree upward from the surgical neck to the subchondral bone near the top of the proximal humeral head to get good stability at the fracture site.

In the operation of the proximal humeral fractures in elderly patients, there are some problems due to osteoporosis. Previously we reported the correlation between BMD and the stability of screw fixation about the proximal humeral fracture model. Also we reported regional difference in BMD within the proximal humeral head in cadavers. In this paper we analyzed BMD in the proximal humeral heads of living bodies to confirm regional differences of BMD within the proximal humeral head. BMD of 10 cases, 20 proximal humeral heads (mean age 67.7 yrs.old ) was analyzed by Discovery A ( Discovery A, Hologic Co.). BMD was measured at 4 regions of interest (ROI) ; top of the humeral head(A), the middle of the humeral head(B), surgical neck(C) and the greater tuberosity(D). We analyzed the BMD value at each ROI and compared the dominant side with non-dominant side. Mean BMD ( g/cm² )A was 0.48, B 0.35, C 0.29 and D 0.39. There was significant difference between A vs. B, A vs. C, A vs. D and C vs. D (p < 0.05). However there was not a significant difference between the dominant side and the non-dominant side. Our results show that there is a significant difference of BMD is in the proximal humeral head. To get good stability of the screws fixation, the edge of the screw must be inserted just beneath the top of the proximal humeral head.

Bone structure and bone strength of the proximal humeral head affect the stability of the internal fixation material at the fracture operation. We evaluated the relationship between the trabecular structure and the bone strength in the proximal humeral head using cadaver humerus. 7 cadavers humerus ( mean age 79.6 ) was analyzed by micro CT. Bone volume/ tissue volume, trabecular number, trabecular thickness, trabecular separation, number of node and length of node strut were measured as trabecular parameters at 3 regions of interest ( region A : top of humeral head, B : middle of humeral head and C : neck ). On the coronal plane the osteotomy was performed on the middle of humeral head and sliced 1 cm thickness. The maximum load value was measured by the compression test using a universal material examination machine ( Instron 4505 )at region A and B. There were significant difference between region A and C, B and C concerning Bone volume/ tissue volume, trabecular number, trabecular separation node number, number of node and length of node strut ( p < 0.05 ). There were significant difference between region A and B( p < 0.05 ) concerning bonestrength. There were positive correlation between bone volume/ tissue volume and bone strength, trabecular number and bone strength, trabecular thickness and bone strength, node number and bone strength and node length and bone strength( p < 0.01). Our result shows the trabecular structure and bone strength at the superior region in the proximal humeral head had better than other regions. There were positive correlation between trabecular parameters and bone strength. Above results indicate that better stabilization is achieved by inserting the screw tip on the superior proximal humeral head at the fracture operation.