Modification of the Unified Classification System for periprosthetic femoral fractures after hip arthroplasty

The Unified Classification System (UCS) for Periprosthetic femoral fractures (PPFF) still has some limitations.

We retrieved 18 previous classifications for PPFF based on systematic review of the literature, and also retrospectively analyzed 402 cases with PPFF. 46 cases (11.4%) were identified as beyond the classification scope of the original UCS.

We modified the UCS as follows: (1) add two new B2 subtypes: B2PALT/B2PAGT (i.e., the pseudo ALT/AGT: Fracture in trochanter region including a segment of the proximal medial/lateral femoral cortex); (2) add a new FS category to encompass stem fracture alone or accompanied by PPFF, with FSO designating this fracture with stem fracture alone, FS1 designating this fracture with the proximal portion of the fractured femoral prosthesis being stable, FS2 designating this fracture with the proximal portion of the fractured femoral prosthesis being loose and the surrounding bone quality being good, and FS3 designating this fracture with the proximal portion of the fractured femoral prosthesis being loose and the bone bed being of poor quality; and (3) delete Type F which does not apply to the femur. Thus, using our modification of the UCS, among the 46 cases, we found thirty-five B2PALT, two B2PAGT, three FSO, one FS1, two FS2 and three SF3.

Compared to the original UCS, our modified version is more comprehensive. We believe it is useful to improve the judgment of the implant stability, and establish the therapeutic strategy for PPFF.