In a prospective study, since March 1989, 55 tibial shaft fractures have been treated with a new, unreamed solid tibial nail (UTN). This nail was initially designed as a temporary implant. The first 33 cases with second or third degree soft tissue damage were reviewed 6 months or more after the operation. Fractures were classified according to Müller: 6 type A (18.2%), 15 type B (45.5%), and 12 type C (36.7%). In 9 cases (27.3%), there was GII (n = 4) or GIII (n = 5) closed soft tissue damage according to Tscherne's classification. The 24 open fractures (72.7%) comprised 11 OII, 3 OIIIA and 10 OIIIB fractures (Gustilo classification). 24 patients (72.7%) were polytraumatized, the mean PTS (Hannover Polytrauma Score) was 18 points (range: 8-65 points). All fractures were stabilized without reaming. The implant diameter was 8mm (n = 14) or 9 mm (n = 19). Static locking was performed in 31 cases. Dermatofasciotomy was necessary because of compartment syndrome in 14 cases. In 1 grade IIIB open fracture soft tissue coverage was performed with a latissimus dorsi myocutaneous free flap 4 days after nailing. In 32 of the 33 cases the use of an additional cast or brace was not necessary during the follow-up treatment; 1 patient had a cast for 8 weeks for the treatment of accompanying injuries. Full weight-bearing was achieved in 5 cases within 3 weeks, in 16 cases within 12 weeks, and in 30 cases within 26 weeks. In 16 cases (48.5%) the interlocking screws were removed after 5-26 weeks (mean: 10 weeks).(ABSTRACT TRUNCATED AT 250 WORDS)