Early versus delayed weight bearing after internal fixation for femoral neck fracture in younger adults: A multicenter retrospective study

Introduction: Femoral neck fracture (FNF) is among the most common and devastating injuries that orthopedic surgeons encounter. However, the incidence of FNF is lower in younger adults than in elderly individuals. In elderly FNF patients, early weight bearing (EWB) is preferred to prevent loss of function and decreased activity. In younger adults, some surgeons decide on delayed-weight bearing (DWB) after surgery because EWB may cause femoral neck shortening. We aimed to compare the postoperative results (clinical outcome, radiological evaluation, and complications) of EWB and DWB after FNF surgery in younger adults. Methods: The study included 151 younger adults (age: <= 65 years at injury; nondisplaced, n = 100; displaced, n = 51) who underwent internal fixation at 11 university-affiliated hospitals in 2016-2020, and who were followed for >= 1 year. Patients were divided into the EWB (EWB in early postoperative period) and DWB (beginning weight bearing at 4 weeks after surgery) groups. The two groups were matched for age, and nondisplaced (EWB and DWB, both n = 24) and displaced (EWB and DWB, both n = 11) FNF were analyzed. The study items were age, sex, body mass index (BMI), Charlson Comorbidity Index (CCI), presence of diabetes, days waiting for surgery, fracture type, Parker mobility score (PMS) at last follow-up examination, pain (Numerical Rating Scale: NRS), radiological evaluation (femoral neck shortening, Canulated Cancellous screws (CCS) backout, and complications (nonunion, femoral head osteonecrosis). Results: The patient backgrounds of the nondisplaced and displaced types did not differ. The PMS was significantly higher in the DWB group at the last follow-up examination (nondisplaced: 8.00 +/- 2.20 vs. 6.67 +/- 2.22, p = 0.005, displaced: 8.67 +/- 0.89 vs. 6.91 +/- 2.77, p<0.001). NRS and the amount of femoral neck shortening were significantly lower in the DWB group (nondisplaced: 1.65 +/- 0.70 mm vs. 3.94 +/- 3.03 mm, p<0.001, displaced: 4.26 +/- 2.64 mm vs. 8.91 +/- 5.69 mm, p<0.001). CCS backout did not differ between the groups. One case of each of nonunion and femoral head osteonecrosis were observed in the displaced EWB and DWB groups; these differences were not significant. Conclusions: DWB after internal fixation for FNF in younger adults was associated with better outcomes than EWB.