Femoral neck fractures after internal fixation of trochanteric fractures with implants in situ in adults: A systematic review.

INTRODUCTION: Femoral neck fractures (FNF) after internal fixation of trochanteric fractures (AIFTF) with the implant in situ (WIIS) are uncommon. Publications of FNFAIFTFWIIS are rare. The purpose of this systematic review of the literature is to report on the frequency, risk factors, mechanisms, clinical presentation, diagnostic and therapeutic modalities, outcomes and the eventual prevention of this complication.

MATERIALS AND METHODS: A comprehensive review of the literature was undertaken using the PRISMA guidelines with no language restriction. Case reports of FNFAIFTFWIIS and series of trochanteric fractures (TF) with this complication in adults published between inception of journals to May 2018 were eligible for inclusion. Cases with fractures in pathological bone, undergoing treatment with hip replacement, or after partial or total implant removal were excluded. Relevant information was divided in two parts. Part I included the analysis of cases of FNFAIFTFWIIS, with the objective of establishing the eventual risk factors, mechanisms, diagnostic, treatment modalities, and outcomes. Part II analyzed series of TFs with implants in situ which included cases of FNFs for assessing the incidence of FNFs in this condition.

RESULTS: Overall 77 publications with 104 cases of FNFAIFTFWIIS met the inclusion criteria. The median incidence of this complication was 0,43%. The mean age was 80 years (range, 42-96).The prevalent factors for FNFAIFTFWIIS were osteoporosis, and the presence of the implant in the femoral neck and head. A short nail or screw with the tip far from the subchondral bone was of influence as a stress riser factor, but not prevalent because in two thirds of the cases the FNF occurred when the implant was introduced up to the subchondral bone. Other risk factors analysed included varus reduction or nonunion of the TF, and the breakage of the hip screw, which modify the forces exerted over the femoral neck, and may contribute to the FNF. The FNFs were spontaneous, i.e. not related to trauma or fall, in more than two thirds of the cases.

CONCLUSION: The etiology of FNFAIFTFWII should be considered multifactorial. The frequency seems low. Although a subchondral positioning of the hip screw might diminish the incidence of FNFS, a correct surgical technique does not preclude a FNFAIFTFWIIS, and in fact the incidence of this complication was higher in these correctly treated patients. FNFAIFTFWIIS is a fragility fracture and adequate management of systemic osteoporosis should be targeted as a main factor of prevention.