The purpose of this study was to evaluate the effect of fibular fractures in the healing of tibial shaft fractures treated with an interlocking nail and to determine whether the fibular fracture had a relation with other prognostic factors.

From Mar. 1992 to Feb. 1995. the authors performed interlocking nailing for displaced fractures of the tibial shaft in 111 patients. We reviewed 98 patients with a minimal ten month follow up period.

We divided the fractures into three groups; the intact fibula group which consisted of 15 patients had tibial shaft fractures with intact fibula, the same level fracture group had tibiofibular fractures at the same level in 56 patients and the different level fracture group had tibiofibular at different level in 27 patients. The results were as follows:

1. Clinically excellent and good results, according to Klemm and Horner criteria. were in 15 patients(100%) of the intact fibula group,49 patients(87.4%) in the same level fracture group and 21 patients(92.5%) in the different leyel fracture group.

2. Radiologically bone healing was obtained in 15 patients(100%) with a mean union time of 13.3 weeks in the intact fibula group, 42 patients(75.O%) with a mean union time of 17.9 weekf in the same level fracture goup and 2,1 patients(85.2%) with a mean union time of 15.3 weeks in the different level fracture group.

3. The same level fracture group had a tendency to cause a bending force while the different level fracture group tended to treat a torsional force. We found that the bending fractures had the worst prognosis.

These results suggest that the treatment of tibial shaft fractures with an intact fibula by using an interlocking nail prevents significant complications and allows early weight bearing, thus permiiting early mobilization of the traumatized patient. The level of the fibular fracture associated with the tibial fracture may be a useful prognostic factors in the healing of tibial shaft fractures.