Biomechanical analysis of column fixation and acute total hip arthroplasty with an anti-protrusion cage in a typical geriatric acetabular fracture.

Abstract

Acute total hip arthroplasty (THA) plays an increasing role in the management of acetabular fractures in elderly patients. However, there is no consensus on the need for column fixation during primary THA, especially for the anterior column. This study aimed to assess the biomechanical impact of column stabilization during acute THA using a Burch-Schneider anti-protrusion cage (BSC) for a typical geriatric acetabular fracture. A finite element model of a hemipelvis with an anterior column posterior hemi-transverse fracture was developed to compare four treatment strategies during acute THA with BSC: anterior and posterior column plating (CAP), posterior column plating (CnP), anterior column plating (CAn), and BSC alone (Cnn). During peak load walking, we analyzed the pelvis displacement, fracture relative motion, bone strain around screws, and metal stress. Pelvis displacement was lowest for CAP and highest for Cnn, while CnP and CAn showed intermediate values slightly higher than CAP. Fracture relative motion, bone strain, and metal stress followed similar patterns. Fracture relative displacement was around 1 mm on average, and below 5 mm, except for Cnn, where it exceeded this value on 22 % of the fracture surface. Peak strain far exceeded 1 % for Cnn, predominantly concentrated at screw tips and screw-plate junctions, as did peak metal stress. This biomechanical analysis indicates that CnP alone provides mechanical stability comparable to isolated or additional anterior column plating. These findings support the single posterior approach concept for acute THA in the management of acetabular fractures in elderly patients.