Biomechanical comparison of the role of inlay graft in proximal humerus fracture fixed with conventional plate and locking plate

With a varus deformity, repairs of proximal humeral fractures frequently fail after screws pull out due to lack of medial support. Indirect intramedullary grafts have been used to prevent such complications. A biomechanical study was performed to investigate the role of an intramedullary bone peg (strut) in fractures fixed with conventional and locking plates. Twenty artificial proximal humerus specimens were divided into four groups. Group 1 specimens were fixed with convention plates and group 2 specimens were fixed with the addition of a bone peg. Groups 3 and 4 specimens were fixed using locking plate and additional bone peg, respectively. All specimens were tested with a static loading test, and the axial stiffness and maximal load were recorded. Locking plates with inlay graft were the most rigid of the four groups. When an intramedullary graft was introduced, the maximal load increased by more than 200%, whether conventional or locking plates were used. The maximal load of a conventional plate with inlay graft was more than twice of that of the locking plate only. Indirect medial support acts as an anti-bending device, reducing the tension on the plate. It also decreases varus deformity and loosening of screws. Locking plate stabilize the plate-bone interface. Locking plate with indirect medial support is thus recommended for patients withsevere osteoporotic or medial comminuted proximal humeral fractures.