Parallel and non-parallel cannulated screw fixation complications in femoral neck fractures: A systematic review and meta-analysis

Background: Since its introduction in the early 1960s, the multiple cannulated screw fixation method has been developed for use in femoral neck fractures (FNFs); however, the parallelism of screws remains controversial. Materials and methods: MEDLINE, Embase, and the Cochrane Library were systematically searched for studies published before June 2, 2020, that compared the use of parallel and non-parallel screw fixation for the treatment of FNF. The pooled analysis was designed to identify differences between the two groups and focused on postoperative complications, including fracture nonunion and osteonecrosis of the femoral head (ONFH). Results: Over four studies, we enrolled 445 patients, including 195 patients with fixed FNF with parallel trajectory screws and 250 patients with fixed FNF with non-parallel screws. The pooled analysis showed no difference in the nonunion rates (odds ratio (OR) = 0.91; 95% confidence interval (CI), 0.24-3.44; p = 0.89) and no significant difference in the incidence of ONFH between parallel and non-parallel screw fixation (OR = 0.74; 95% CI: 0.21-2.63; p = 0.64). Conclusions: The results of this meta-analysis reveal that screw parallelism in multiple cannulated screw fixation of FNF has no relationship with either the fracture nonunion rate or the incidence of postoperative ONFH. Level of evidence: III; meta-analysis. (c) 2021 Elsevier Masson SAS. All rights reserved.