Classification and Reconstruction of Femoral Bone Defect in the Revision of Aseptic Loosening of Distal Femoral Endoprostheses: A 10-year Multicenter Retrospective Analysis

Abstract

Objective This study proposes a system for classifying the aseptic loosening of distal femoral prostheses and discusses reconstruction methods for revision surgery, based on different classification types. Methods We retrospectively analyzed the data of patients who received revision surgery for aseptic loosening in distal femoral tumor endoprosthesis from January 2008 to December 2018 at 3 bone tumor treatment centers in China. On the basis of the patient imaging data, we proposed a classification system for the aseptic loosening of distal femoral endoprostheses and discussed its revision surgery strategy for various bone defects. Results A total of 29 patients were included in this study, including 20 males and 9 females aged 15–64 y (average: 43.2 y). First-revision surgery was performed on 25 patients, whereas second-revision surgery was conducted on 4 patients. The 29 patients were classified into different types based on the degree of aseptic loosening: Type Ia, 5 patients (17.2%); Type Ib, 7 patients (24.1%); Type IIa, 9 patients (31.0%); Type IIb, 7 patients (24.1%); and Type IIIb, 1 patient (3.4%). Four Type Ia patients used the longer-stem rotating hinge prosthesis, and 1 Type Ia patient used the original prosthesis. Six Type Ib patients used a longer-stem rotating hinge, and 1 Type Ib patient used the original prosthesis plus bone grafting with an allograft bone plate for revision. Eight Type IIa patients underwent revision with a longer-stem rotating hinge prosthesis, and 1 Type IIa patient received revision surgery with the original prosthesis plus bone grafting with an allograft bone plate. Meanwhile, 5 Type IIb and 1 Type IIIb patients used a longer-stem rotating hinge prosthesis, and 2 Type IIb patients used the original prosthesis for revision. Conclusions Aseptic loosening of the distal femoral prosthesis can be divided into 4 types and 8 subtypes. Different types of bone defect can be repaired with the appropriate reconstruction.