Fracture of femoral neck in modular total hip arthroplasty: a systematic review of the literature

Background: Modular femoral stems have the advantage of anatomic hip reconstruction by restoring the femoral offset thus minimising the bearing surface wear, implant loosening and dislocation. Aim: This study aims to investigate the existing literature on modular neck fractures, to identify predisposing factors and guide the decision-making process in the management of these difficult cases. Methods: A systematic literature review was conducted until July 2022. PRISMA guidelines were followed, eligibility criteria were set, and methodology assessment of included studies was conducted based on MINORS criteria, size and primary outcome. Data were extracted and analysed thoroughly. Results: 5657 studies were initially screened; the full texts of 124 records were assessed and finally, 32 reports were included. There were 7 clinical studies and 25 case reports. A total of 4825 patients (5204 hips) with a mean age 62.38 years and a mean BMI 29.06 kg/m(2) were analysed in the 7 clinical studies. The reported overall weighted revision rate was 0.86%, while the weighted mean modular neck fracture rate was 0.26%. The usual history was sudden experience of hip pain and instability. The average time interval to neck fracture was 4.57 (range 3-4.7) years and a long modular neck was identified in 91.17% of them. Data from case reports showed a mean age and average BMI of 55.85 and 31.63 kg/m(2). 82.35% of the patients were male. Necks were fractured after an average time interval of 64.5 +/- 8.8 months. Conclusions: The incidence of modular neck fracture is significant. The profile of a male, obese patient with a long modular neck increased risk of neck fracture. Microstructural investigation of the retrieved implants demonstrated a higher incidence of fracture line in the base of the neck junction and at its anterolateral distal part. Surgeons should be aware of this complication while using or revising such protheses.