Eighteen studies with 674 patients were included in the review. Follow-up data were available for 564 (83.7%).
Three studies scored 6 for methodological quality, six scored 5 and nine scored 4.
Fracture displacement and complications.
Displaced intracapsular hip fractures were more common than undisplaced fractures (79.9% versus 25.6%). Overall, the incidence of nonunion was 8.9% and avascular necrosis 23%. The incidences of nonunion and avascular necrosis were both higher in displaced than undisplaced fractures: 6% versus 0.9% for nonunion (P=0.02) and 22.5% versus 5.9% for avascular necrosis (P<0.001).
Method of reduction and complications.
The incidence of nonunion was significantly higher in fractures that underwent open compared with closed reduction (11.2% versus 4.7%, P=0.04; RR 0.42, 95% CI: 0.19, 0.93).
The incidence of avascular necrosis was significantly higher in fractures that underwent closed reduction than open reduction (28% versus 10.1%, P=0.0005; RR 2.8, 1.45, 5.29). No significant difference between open and closed reduction was observed following the exclusion of a study with a high rate of avascular necrosis.
Timing of reduction and complications.
No significant differences between early and late fracture reduction were found in the incidence of nonunion (11.8% versus 5%, P=0.18; RR 2.36, 95% CI: 0.7, 7.79) and the incidence of avascular necrosis (13.6% versus 15%, P=0.82; RR 0.91, 95% CI: 0.42, 1.95).