Unreamed intramedullary tibial nailing--fatigue of locking bolts.

Between January 1990 and October 1993 we investigated 72 consecutive patients who had an unreamed tibial nail inserted for fractures of the tibial shaft; 75 per cent (N = 54) were closed fractures and 25 per cent (N = 18) were open fractures. The mean follow up was 15.2 months. Of the patients 91.7 per cent (N = 66) were interlocked, 58 per cent (N = 38) statically and 42 per cent (N = 28) dynamically. Union rate was 98.6 per cent, time to union was 18.5 weeks, 17.3 weeks for closed fractures, 22 weeks for open fractures. Shortening greater than 1 cm occurred in 1.4 per cent (N = 1), varus and valgus deformity in 4.1 per cent each (N = 3). There was no rotational deformity. Of the locking bolts 30 per cent broke 8-10 weeks after partial weight bearing was allowed. Electron microscopy investigations showed that failure of the bolts was due to fatigue. It was not associated with any clinical problems with regard to union times or incidence of malunion. Bolt failure is however a problem if you try to remove the nail.