Effect of Early Axial Dynamization on Tibial Bone Healing : A Study in Dogs

Although it has been well established that fracture healing is influenced by the mechanical environment, the optimal parameters have not yet been established. In two groups of sheep an experimental tibial diaphysial fracture was created, and stabilised using external skeletal fixation. In one group rigid fixation was maintained throughout fracture healing; in the other group controlled axial micromovement, with a loading regime known to be osteogenic in intact bones, was applied for a short period daily. A significant improvement in healing was associated with the application of controlled micromovement. Data from these experiments provide the basis for improving the conditions for fracture healing and may assist in the prevention of delayed union.

For many fractures of the femoral shaft, closed intramedullary nailing will not control rotation or telescoping of the fragments. Locked intramedullary nailing combines closed nailing with the percutaneous insertion of screws that interlock the bone and nail. This method permits static locking that controls rotation and telescoping and subsequently conversion to dynamic locking when weight-bearing is started after approximately twelve weeks. By providing greater stability, this method extends the indications for intramedullary nailing to severely comminuted, oblique, and spiral fractures as well as to fractures complicated by loss of bone and fractures in the proximal and distal ends of the femoral shaft. Of fifty-two patients with forty-nine severely comminuted fractures of the femoral shaft and three fractures that were complicated by loss of bone, forty-seven patients had uneventful consolidation of the fracture, with a mean time of 4.5 months for the severely comminuted fractures and seven months for the fractures that had a loss of bone. At follow-up, all forty-seven patients had normal motion of the hip, and forty-five had normal motion of the knee. Of the remaining five patients, four had a non-union that eventually healed (three after a second locked nailing and one after a third) and one had a septic non-union that eventually healed after removal of the nail and screws, débridement, and immobilization with an external fixator. Based on this experience, we concluded that this form of treatment has many advantages. The risk of infection and non-union is low, the incidence and severity of malunion are reduced, the hospital stay is short, and early mobilization of the patient is possible.

The results obtained with a lightweight dynamic axial fixator in the treatment of fractures are reported. The apparatus comprises a single bar with articulating ends which clamp self-tapping screws and can be locked at an angle appropriate for axial alignment. A telescopic facility allows ready conversion from rigid to dynamic fixation once periosteal callus formation has commenced. Reduction and controlled distraction or compression are achieved by means of a detachable compressor unit. We treated 288 patients with fresh fractures and 50 with ununited fractures. The success rate for fresh fractures was 94%, with average healing times ranging from 3.4 to 6.5 months. In ununited fractures also, the success rate was 94% with average healing times ranging from 4.7 to 6.5 months. Complications were minimal. The device is versatile and can be applied in an average of 15 minutes. It permits ambulatory fracture care without sacrificing a sound anatomical result.