total hip arthroplasty; acetabular reconstruction; bone defect; trabecular metal; augment
The management of severe acetabular bone defects in hip revision surgery is challenging. The goals of revision surgery include to correct the cranial migration of the hip center of rotation (COR) restoring the biomechanics of the hip with an effective function of the abductors , and to preserve the acetabular bone stock.
The use of trabecular metal (TM) cups has widely increased during the past decade 2., 3., 4. and 5.. TM is a biomaterial made out of tantalum characterized by high 3D porosity (70–80%), high friction and low modulus of elasticity. It provides primary stability at the time of the procedure, and allows a deep bony in-growth leading to a secondary biologic fixation 6. and 7.. Because the type of bone defect is variable, the TM augments have been also introduced for the management of severe bone defects in the acetabular reconstruction. Indeed, the variability of augments in terms of size and shape allows to perform a customized reconstruction maximizing the contact with the host bone restoring the hip COR.
Given its biomechanical properties and biocompatibility, the association of TM cups and augments could represent an effective management of bone defects in acetabular reconstructions. Although some authors investigated the use of TM cups and augments in this setting 3., 8., 9., 10., 11., 12., 13., 14., 15., 16. and 17., they performed studies including patients with different types of bone defects, ranging from Paprosky grade IIA to grade IIIB with pelvic discontinuity, who underwent revision surgery using TM acetabular cups with or without TM augments. Therefore, data arising from these studies refer to non-homogenous populations managed with different surgical techniques. To our knowledge, only two previous studies assessed a small case series including patients affected by Paprosky type IIIA defect managed with the association of TM acetabular components and augments 10. and 11.. In our opinion, further evidence is required to confirm the effectiveness of TM-coated cup and augment association in Paprosky type III defects.
The aim of this retrospective case series was to assess the clinical and radiographic outcomes of TM augments associated with cementless TM acetabular components for the management of Paprosky type IIIA and IIIB defects without pelvic discontinuity. The null hypothesis was that the acetabular reconstruction with TM-coated cups and augments provides a statistically significant improvement of range of motions (ROMs) of the hip and Harris Hip Score (HHS) values, and reduction of limb-length discrepancy (LLD) and cranial migration of the hip COR.