Malunion of a fracture

What it is

Malunion is a fracture that heals with a deformity, for example angulation or rotation. The bone is whole again, but in the wrong shape.

Causes and risk

It is more common in:

• Unstable patients at surgery
• Severely comminuted fractures
• Nonsurgical treatment, that is cast or splints
• Premature overloading of the limb, which gives a delayed onset

Two of those four are ours and not the fracture's: the choice of nonsurgical treatment, cast or splints, and premature overloading of the limb.

The types, and the rule for naming them

The types describe the position of the distal segment in relation to the proximal segment of bone. The deformity is named for the distal part, never the proximal one, and that is how the names are read:

• Angular: varus or valgus
• Rotational: internal or external malrotation
• Axial: shortening, since overlengthening is rare
• Translation, usually insignificant
• Combined or complex deformity

Read through the types with that rule in hand: angular is varus or valgus, rotational is internal or external malrotation, and cubitus varus holds both at once, internal rotation plus varus - and in every one of them it is the distal segment being described, never the proximal.

That is how the page names them: tibia external malrotation, femur external malrotation, and cubitus varus, given as internal rotation plus varus.