We reviewed the radiological and clinical long-term results after the nailing in situ of slipped upper femoral epiphysis in 59 hips in 43 patients. The displacement of the epiphysis had been measured as the ‘slipping angle’ before operation and related to the results at follow-up at a mean of 30.9 years (27 to 34). The mean age at follow-up was 44.2 years (39 to 50).

Radiographic re-examination of 41 hips with slipping angles of ≤30° at the time of operation showed that eight (20%) had developed mild osteoarthritis and one had severe changes. For 18 hips with slipping angles ranging from 31 to 50° at surgery six (33%) had mild osteoarthritis and three had severe changes. The differences did not quite achieve statistical significance (p = 0.09).

Clinical re-examination of the 41 hips with slipping angles of ≤30° showed fair or poor results (Harris hip score < 90) in three (7%). In the 18 hips with slipping of 31 to 50°, four had fair or poor results (22%) (p= 0.13).

We conclude that nailing in situ for slipping of ≤30°, using one thin nail, can give excellent long-term results. At present we recommend that hips with slips ranging from 31 to 50° should also be nailed in situ, but further long-term studies are required, especially on the choice between nailing in situ and corrective osteotomy for slips in excess of 50°.