Introduction: Implant fixation assessment following Vancouver B1 periprosthetic hip fracture is a major decision factor for internal fixation and/or implant revision. The main aim of the present study was to assess the correlation between radiographic Remaining Attachment Index (RAI) and risk of implant loosening at last follow-up following internal fixation of Vancouver B1 periprosthetic hip fracture. Material and method: A multicentre retrospective study included 50 patients with Vancouver B1 periprosthetic hip fracture with uncemented femoral stem between 2013 and 2019. Preoperative radiographs were analysed independently by 2 senior orthopedic surgeons, distinguishing 2 groups: RAI > 2/3 versus < 2/3. Postoperative and last follow-up radiographs were then screened for signs of complete femoral component loosening. Results: Median age was 89 years (range: 36-99 years). Two RAI > 2/3 patients showed implant loosening (8%) versus 9 RAI < 2/3 patients (36%), disclosing a significant correlation between early loosening and RAI < 2/3 (p = 0.005). Interobserver agreement for both radiographic RAI and radiographic loosening assessment at last follow-up was 98% with kappa correlation coefficient 0.96 [range: 0.88-1]. Conclusion: Remaining Attachment Index < 2/3 in Vancouver B1 periprosthetic hip fracture was a risk factor for early implant loosening after isolated internal fixation. In these often frail elderly patients, first-line implant exchange is to be considered in the light of the risk/benefit ratio. The present results confirm the need for rigorous preoperative radiographic work-up of the remaining attachment area in Vancouver B1 fracture. Level of evidence: IV.