https://doi.org/10.1177/1120700020971726 HIP International 2020, Vol. 30(2S) 77–85 © The Author(s) 2020 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/1120700020971726 journals.sagepub.com/home/hpi HIP HIP International Introduction Periprosthetic fracture is one of the worst complications of total hip arthroplasty (THA) with high rates of unfavoura- ble prognosis and mortality. 1,2 The cumulative risk of post- operative periprosthetic femoral fractures (PFF) is 3.5% at 20 years. 2 Poor bone quality, decreased bone stock and osteolysis are considered major risk factors for PFF. 2–6 Antiresorptive drugs (ADs) such as bisphosphonates (BPs) and denosumab, are able to reduce, or even to revert, periprosthetic bone loss by inhibiting bone resorption. 7,8 In this way ADs, whose efficacy in preventing osteoporotic fractures had been clearly demonstrated, 9–11 might also prevent PFF. However, it has been assumed that prolonged AD use may play a role in the occurrence of stress fracture on the tensile side of the femoral shaft known as atypical femoral fractures (AFF). 12,13 These fractures are character- ised by a high incidence of delayed union, non-union and implant failure; 14–16 therefore, since their first description Atypical periprosthetic femoral fractures of the hip: characterisation of three cases Giuseppe Toro 1,2 , Ciro Di Fino 1 , Annalisa De Cicco 1 , Gabriella Toro 3 , Marco Paoletta 1 , Antonio Toro 4 , Umberto Tarantino 2 , Giovanni Iolascon 1 and Alfredo Schiavone Panni 1 Abstract Introduction: Long-term use of bisphosphonates (BPs) has been associated with a specific type of tensile side femoral stress fracture known as Atypical Femoral Fracture (AFF). Theoretically periprosthetic femoral fractures (PFF) should be excluded from the diagnosis of AFF. However, emerging evidence correlates prolonged BPs use with the occurrence of a type of PFF with an atypical pattern (atypical PFF, APFF). The aim of the present study is to report 3 cases of APFF treated at a single centre. Methods: Clinical and radiographic records of PFF that occurred between January 2016 and August 2018 were retrospectively reviewed. All patients meeting the American Society for Bone and Mineral Research (ASBMR) criteria for definition of PFF were included. Management strategies for APFF and patient outcomes, including fracture healing and hip function (assessed by the Oxford Hip Score [OHS]) were collected. Results: 3 patients in the study period were identified as APFF (1 incomplete, 2 complete). All patients were females with a mean age of 83.3 years. All patients were treated with lateral plating. The application of a contralateral strut allograft resulted in fracture healing in cases of complete fractures. Mean OHS at final follow-up was 34.3. Conclusions: Despite occurring around a hip stem like PFF, APFF had peculiar clinical and radiographic features, making them more similar to AFF. Therefore, the orthopaedic surgeon should also consider the natural history and healing problems associated with AFF prior in order to choose the most appropriate management for APFF. Keywords Atypical femoral fracture, bisphosphonates bone graft, periprosthetic fracture, strut graft Date received: 23 May 2020; accepted: 28 August 2020 1 Department of Medical and Surgical Specialties and Dentistry, University of Campania “Luigi Vanvitelli”, Naples, Italy 2 Department of Clinical Sciences and Translational Medicine, University of Rome Tor Vergata, Rome, Italy 3 Unit of Radiology, Ospedale del Mare, Naples, Italy 4 Unit of Orthopaedics and Traumatology, “Martiri del Villa Malta” Hospital, Sarno, Italy Corresponding author: Giuseppe Toro, Department of Medical and Surgical Specialties and Dentistry, University of Campania “Luigi Vanvitelli”, Via L. de Crecchio 4, Naples, 80138, Italy. Email: giusep.toro@gmail.com 971726HPI 0 0 10.1177/1120700020971726HIP InternationalToro et al. research-article 2020 Original Research Article