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Although femoral neck fractures (FNFs) are common injuries, optimal treatment methods have not yet been established. FNFs disproportionately affect the ageing population and are associated with high disability and mortality. Since Garden’s classification was introduced in 1961, hip arthroplasty has emerged as the preferred method for treating displaced FNFs in older patients. However, for undisplaced or minimally displaced FNFs, internal fixation has been the prevailing treatment option, regardless of biological age and activity. Reoperation rates after internal fixation have been reported, ranging from 8% to 19%. Reducing treatment failures and subsequent re-operations is of clinical significance to improve care for this vulnerable patient population. Several treatment options, such as internal fixation and arthroplasty, have been proposed to manage basicervical FNFs. However, the number of available reports on clinical outcomes is limited.

Paper 1 is a register-based observational cohort study of the panorama of FNFs in Sweden based on data from the Swedish Fracture Register (SFR), allowing us to include a large number of FNFs for analysis. Data on age, sex, seasonal variation, trauma mechanism and location, fracture type, treatment and mortality are presented.

Paper 2 is an observational cohort study based on data from the SFR. All basicervical FNFs between 2011 and 2020 and entered into SFR at the participating sites (Sunderbyn, Umeå, Östersund, Karlstad, Uppsala and Göteborg) were screened. A review of radiographs and medical records was performed. We found basicervical FNFs to be difficult to classify accurately. Furthermore, undisplaced basicervical FNFs have a low re-operation rate when treated with internal fixation compared to displaced basicervical FNFs.

Paper 3 is an observational cohort study based on data from three centres (Umeå, Skellefteå and Danderyd) with a consecutive series of undisplaced FNFs treated with internal fixation. This study investigated the association between dorsal and anterior tilt on the lateral radiograph and the outcome after internal fixation. We found that dorsal tilt >20° and anterior tilt >10° increased the risk of treatment failure.

Paper 4 is an observational cohort study based on data from the SFR. We identified a cohort of stress-induced FNFs and reviewed patient medical records to verify a correct diagnosis and identify treatment failures. The study sought to depict the panorama of stress-induced FNFs and document instances of treatment failures. We found low mortality rates, a biphasic age distribution and a large proportion of displaced FNFs.

Paper 5 is a case series of 93 occult FNFs treated with internal fixation. A consecutive series of occult FNFs from four centres were included (Umeå, Skellefteå, Danderyd, Malmö). The treatment failure rate after internal fixation was analysed, and it was shown that 6% led to treatment failure.