Experimental investigations of the insertion and deformation behavior of press-fit and threaded acetabular cups for total hip replacement.

Background: The deformation behavior of threaded and press-fit acetabular cups in correlation with the applied torques and forces to insert the cups has not been widely investigated. The aim of this experimental study was to analyze the deformation behavior of threaded (BICON-PLUS) and press-fit (EP FIT PLUS and Metal shell) acetabular cup designs during insertion and extraction with regard to the possibility of cup failure.

Methods: The experiments were carried out using artificial bone and human acetabular bone.

[The influence of different surface treatments on the primary stability of cementless acetabular cups: an in vitro study].

Introduction: Long-term stability of cementless acetabular cups depends on osseointegration, which requires primary stability of the implant. The aim of this study was to determine the influence of different surface treatments on the primary stability of press-fit acetabular cups. Mechanical lever-out tests were performed to quantify the stability in vitro.

[Initial stability of press-fit acetabular cups--an in-vitro study].

Aim Of The Study: Mechanical lever-out tests were performed in vitro to investigate the initial stability of press fit acetabular cups.

Method: Five different uncemented, hemispherical press-fit cups were implanted in a standardized manner into Sawbones, Polyurethane foam blocks. Each cup was levered-out by using a 250 mm stainless steel rod, which was connected to the acetabular cup.

[Evaluation of the assembling and retention forces of constraint liners for total hip replacement].

Dislocation is a severe complication after total hip replacement which may cause revision surgery in some cases. The use of constraint inserts that are coupled to the femoral head by a snapping mechanism provides an opportunity for treatment of recurrent dislocations. This study was aimed to investigate the assembling and retention forces of a specific constraint liner.

[Experimental analysis of neutral, asymmetric and constraint liners for total hip replacement: investigation of range of motion and protection against joint instability].

Aim: Recurrent dislocation after total hip replacement is a severe complication, which requires specific treatment and implants. The purpose of the present study was to compare a constraint liner with an elevated rim and standard liner regarding their range of motion and dislocation stability.

Method: With a test device, range of motion until impingement (ROM (Imp)) and dislocation (ROM (Lux)) were experimentally analyzed using the above-mentioned insert types of a commercial total hip system.