Until such time as we are able to reliably encourage the humeral condyles to fuse together it seems that the only practical management of IOHC is the placement of a stabilising screw. In that the incidence of fatigue failure of IOHC screws is high it seems reasonable to use the strongest screw available. We have manufactured a small range of 4.5 shaft screws from 32mm to 40mm specifically for this procedure.
Andy Moores advises me that the 4.5 shaft screw has an AMI (bending resistance) 5 times greater than a 4.5 cortical screw. Placement of the screw is, however, a challenge in that the gliding hole has to penetrate the far condyle.