The Shape of the endosteal canal of the humerus. It is not a cylinder and definitely it is not straight. Implications for total elbow and shoulder replacement

The humeral canal proximally is not straight while all shoulder stems are straight. Aggressive reaming during total shoulder replacement for a "good fit" of the implant in the canal will lead to asymmetric removal of the endosteal bone and thinning which can result in loss of cortical thickness are certain areas and eventually at areas susceptible to fracture.

Supracondylar region of distal humerus. From oval the humeral canal changes to triangular. See previous post for clinical implications of distal humeral anatomy.