[Femoral neck fractures in adults: joint sparing operations. II. The significance of surgical timing and implant for development of aseptic femur head necrosis].

Statistical analysis of the results of the AO multi-center study (Part I) shows significant advantages of early (within 24 h) operative stabilization of the medial neck fracture (P < 0.05) and of use of the dynamic hip screw (DHS) as implant (P < 0.01). Secondary surgery necessitated by implant complications led to higher rates of aseptic femoral head necrosis (FHN) and non-unions (NU) (P < 0.05). According to the so-called logistic regression, the rate of NU is influenced most by the number of implant complications and the choice of implant, the rate of FHN by the interval time-lapse between fracture and follow up, the implant selected (the best being the DHS), primary dislocation (poorest results obtained in Garden types III and IV) and the time-lapse between fracture and operative stabilization. This puts the assumed paramount importance of dislocation in perspective and calls in question the dogma that a dislocated intracapsular neck fracture will necessarily be followed by FHN.