Hazards of internal fixation in the treatment of slipped capital femoral epiphysis. We reviewed the records of 202 patients (308 hips) in whom a slipped capital femoral epiphysis had been fixed with pins or screws. A serious complication that was directly related to the use of internal fixation developed in eighty hips (26 per cent). The rate of complications in the 202 patients was 40 per cent. In thirty-six (18 per cent) of the 202 patients, an additional procedure was done to correct a pin-related complication. Forty-one hip joints had been penetrated by a pin. Other complications included avascular necrosis (fourteen hips), chondrolysis (nine), fracture (one), infection (one), further slippage (one), sciatic-nerve injury (one), and breakage of a screw (eight). Ways of decreasing the incidence of complications of fixation were explored. 