Timing of internal fixation of femoral neck fractures. A systematic review and meta-analysis of the final outcome.

The aim of the present study was to evaluate the effect of timing of internal fixation of intracapsular fractures of the neck of femur on the development of late complications, particularly osteonecrosis of femoral head (ONFH) and non-union. We undertook a systematic review of the literature adhering to the PRISMA guidelines. There were 7 eligible reports for the final analysis. The methodological quality of component studies was assessed with the Coleman Methodology Score (CMS). Each included study was assigned a score independently by the two reviewers. The final score of each individual study constituted the average value of the scores given by the two reviewers. The agreement between the two assessors was tested with intraclass correlation coefficient (ICC). The CMS ranged from 37 to 64 within component studies (mean: 46.5, SD: 10.8, median: 41). The ICC was 0.94 (95% CI: 0.69-0.99), implying a nearly perfect agreement between the two assessors. Based on the available data regarding the timing of operative fixation of the femoral neck fractures, 4 discreet pairs of comparison groups could be created: (1) fractures fixed within 6h from injury versus fractures fixed after 6h from injury; (2) fractures fixed within 12h versus after 12h; (3) fractures fixed within 24h versus after 24h; and (4) fractures fixed within 6h versus after 24h. Outcome measures were analyzed within each one of the above pairs of treatment groups. The following subgroups analyses were a priori decided: (1) initial fracture displacement (displaced vs. undisplaced fractures); (2) fixation method (cannulated screws vs. sliding hip screw); (3) quality of reduction (anatomic vs non-anatomic reduction). This study failed to prove any essential association between timing of NOF fracture internal fixation and incidence of AVN. With respect to non-union though, it indicated that delay of internal fixation of more than 24h could increase substantially the odds of non-union.