The strengths of healing long-bone fractures treated in two different
mechanical environments were compared using a rabbit experimental model.
Constant compression was applied to one healing tibial fracture, while the
other was subjected to cyclic compression. At six weeks of healing, the
group of tibial fractures treated with cyclic loading exhibited
significantly higher torque and energy absorption to failure and lower
stiffness than their pair-mates treated with constant compression. No
statistically significant differences were detected at four or eight weeks
of healing, although there was a suggestion that compression-treated bones
may be stronger in the earlier phases of healing. Clinical Relevance: This
experiment suggests that the requirements for rapid fracture-healing may
vary with the stage of healing; that is, rigid immobilization applied
during the initial stages of healing followed by intermittent compression
during later stages.