Bilateral FNF is rare, and it is necessary to look for an associated condition that predisposes to this injury. As described in the 1960s, seizures can be a risk factor for bilateral FNF. This is due to the muscular tensions received by the proximal segment of the femur, secondary to these crises (10). Kimura et al. also described a case of bilateral femoral fracture secondary to tonic-clonic seizures, which was resolved with a bilateral hip arthroplasty using an anterior approach (3). Diaz Dilernia et al. described a case of bilateral femoral neck injury in a patient with a history of seizures and chronic use of corticosteroids as part of a brain tumor treatment. Both fractures were resolved with a one-staged total hip arthroplasty (11). In our case, similar to the findings reported by these authors, we can infer that the “shakings” reported by the nursing staff corresponded to a seizure episode, predisposing to bilateral hip injury. Continuing with neurological disorders, bilateral FNF was also documented in a patient with cerebral palsy mimicking abdominal pain that was resolved with a bilateral uncemented total hip arthroplasty due to his young age (4). In our case, unipolar uncemented hemiarthroplasties were chosen due to the low functional demand, the short life expectancy and the possibility of BCIS in this group of patients (9).
Eating disorders are another predisposing factor for bilateral FNF. There are reports that associate anorexia nerviosa with stress fractures. This pathology can decrease bone density through two mechanisms: alteration in body composition and hormonal changes. This combination, added to an intensification of sports activity, can predispose an occult bilateral femoral neck fracture (12). Endocrinological disorders and more precisely, alterations in phospho-calcium metabolism, can lead to a bilateral hip fracture. This injury can occur in patients with renal osteodystrophy, osteomalacia, and primary hyperparathyroidism (13). Reports of cases have also been described in young patients with osteoporosis and Vitamin D deficiency (2/14). Elderly patients with severe osteoporosis may also suffer a bilateral hip fracture secondary to low-energy trauma. A lesion of these characteristics has double morbidity and mortality compared to patients with a unilateral fracture, since bedtime can be prolonged with the subsequent complications that this entails (urinary infection, pneumonia and deep vein thrombosis) (15). In the last two years, our patient suffered low-energy fractures in two different bones (pelvis and proximal humerus) being able to infer that the mineral density of the patient's bone was suboptimal.
Additionally, Csotye et al. reported a case of bilateral femoral neck fracture during pregnancy. This was secondary to transient osteoporosis in the third trimester of pregnancy. This suggests that in the face of bilateral hip pain in a pregnant patient, protecting the weight load can prevent catastrophic consequences in a transitory disease (16).
Finally, as is known, bilateral hip arthroplasty is used around the world with excellent results (17), and it is a safe option in appropriately selected patients (18). To guarantee the successfulness of the bilateral hip surgery, it is mandatory to perform an expeditious surgery, to have a strict and well-controlled prophylaxis for thromboembolic diseases, and have an aggressive postoperative rehabilitation(19). Communication and co-working with anesthesiologists and physical therapist´s team is a key part of the success of bilateral hip surgery.
We presented a patient with severe osteopenia, who suffered a suspected seizure episode and this led her to present a bilateral FNF. Due to the general condition and low functional demand, a bilateral one-stage uncemented hemiarthroplasty was indicated. Despite being a rare injury, bilateral femoral neck fracture may occur in elderly patients, especially in those with severe osteoporosis who have low-energy trauma. Early diagnosis and surgical intervention are extremely important, allowing early recovery and mobilization.