Rationale: We present 2 cases of lateral incomplete impending fracture of the femoral neck without trauma in elderly patients taking long-term bisphosphonate (BP) treatment, and we defined it as atypical femoral neck fracture (AFNF). To the best of our knowledge, this is the first report on the follow-up results of AFNF.
Patient concerns: Patients in both cases had been taking BP drugs for a long time with osteoporosis. The duration of BP treatment was 6 years, and there was no history of repeated stresses.
Diagnoses: All fractures were linear at the lateral aspect of the mid portion of the femoral neck, and the BMD of the femoral neck was -0.9, and -1.8, respectively.
Interventions: Internal fixation was performed in both cases (73 years, 68 years) using cannulated screws.
Outcomes: In both patients who underwent screw fixation, the fracture line started to extend distally at 4 weeks and 2 weeks following surgery. In the 3-month follow-up image, the length of the fracture increased by 20.1 mm and 9.9 mm, respectively. There was a problem with active rehabilitation, and the possibility of revision was also found to be a burden in terms of mortality and cost in older patients.
Lessons: In the case of AFNF, guidelines for treatment should be set in consideration of the decreased bone healing, even when the fracture pattern is simple. Arthroplasty based on a wider indication may be worth considering.