Development of small diameter intramedullary nails made from ISO 5832-9 stainless steel.

Background: In order to improve strength in small diameter intramedullary nails, a system was designed in which the implants were manufactured from 30% coldworked ISO 5832-9 stainless steel.

Methods: Nail diameters were 9 and 10 mm for the femur, and 8 and 9 mm for the tibia. The nails were solid rods and the screws were partially threaded. Pre-clinical bending yield tests established that the 8-, 9- and 10-mm diameter rods had strengths comparable, respectively, with 10-, 12- and 14-mm diameter Grosse-Kempf nails. Forty-eight femoral and 98 tibial shaft acute fractures were treated with this system. Postoperatively, patients were allowed to gently bear weight as tolerated.

Results: There was one broken nail, occurring 10 months after femoral nailing. There were six broken screws, occurring between 3 and 6 months postoperatively in two patients and after more than 6 months in four patients. The broken screws had no adverse clinical effect. Five patients required late bone grafting or exchange nailing, and 15 patients required dynamization.

Conclusion: This design of small diameter locked intramedullary nails was strong enough to allow early weightbearing.