Proposal for the classification of peri-implant femoral fractures: Retrospective cohort study.

Background Peri-implant fractures occur in association with an implant used to treat a previous injury and that is still attached to the bone. Peri-implant fractures are considered to be relatively "new" fractures and they lack any classification system that is accepted in practice. Generally, the fracture classification systems currently used in our clinical practice were not developed or validated using rigorous scientific evaluation methods. Aim To provide data for a proposed classification of peri-implant femoral fractures. Methods This is an international and multicentre study (12 centres) based on a cohort of consecutive peri-implant fractures with the criterion being: a fracture in any segment of the femur in association with previously-used osteosynthesis material, whether a nail, plate or screws. A proposed system for the classification was tested, based on a topographical classification using alphanumeric coding, following a similar nomenclature to that explained in the "Vancouver-Classification-for-Total-Hip-Arthroplasty-Periprosthetic-Fractures", and classified according to whether the implant is a nail, a screw or a plate, and the location of the fracture in relation to the original implant and the affected femoral segment. The study coordinator performed the first classification exercise, which was discussed subsequently for the study coordinator group to reach a consensus. A descriptive analysis of the fractures was produced. The proportion of peri-implant femoral fractures was estimated, and 95% confidence interval (95%CI) was calculated. Results Between January 2013 and December 2016, data on a total of 143 peri-implant femoral fractures were collected. Only 5 (3.5%) fractures had to be discussed to reach a consensus. The most common peri-implant femoral fractures were located at the diaphyseal segment (#32) and associated with nails or plates: 51%, 73/143, 95%CI:43-59%; at the proximal segment (#31): 39%, 56/143, 95%CI:32-47%; and at the distal femoral segment (#33): 10%, 14/143, 95%CI:6-16%. The highest proportion of peri-implant femoral fractures corresponded to #31-AN (trochanteric and neck area) and #32-CNP (diaphysis fractures distant from the implant, often distal and spiral). Conclusion The proposed classification for peri-implant femoral fractures appears to be useful and easy to accomplish. Future studies will be necessary to validate it and demonstrate the effectiveness of its application in clinical practice.