Causes

Many factors may impede bone healing causing delayed union or non-union. They are conveniently discussed in terms of the injury, the bone, management of the injury and the patient, although in any one case, all may contribute.

The injury:

• interposition of tissue between the bone fragments - periosteum, muscle or cartilage
• expulsion of the bone fragment at the scene of the injury producing an excessive gap
• severe comminution or displacement producing instability
• intact fellow bone preventing realignment and bony apposition - e.g. an intact fibula with fractured tibia
• soft tissue contracture producing a deforming forces - e.g. ankle equinus causing angulation of a mid-tibial fracture

The bone:

• poor quality - e.g. a pathological fracture
• poor local circulation e.g. fractured neck of femur
• infection

Management of the fracture:

• excessive traction - pulling the fragments too far apart
• poor fixation - poorly applied or incorrect technique
• excessive splintage - bone becomes osteoporotic, muscles atrophied, and joints stiff

The patient:

• poorly motivated - doesn't want to mobilise
• poorly nourished
• poor general health