Evaluation of sleeved implant fixation using a rat model.

Cementless hip implants have some osteolysis, stress shielding, and/or revision problems while the cemented ones have cement fracture problems. To overcome these problems, a new concept of implant fixation using a sleeve between the implant and the bone is proposed. This is a cementless fixation using a sleeve in place of the cement with a press-fit stem.

The effect of abductor muscle and anterior-posterior hip contact load simulation on the in-vitro primary stability of a cementless hip stem.

Background: In-vitro mechanical tests are commonly performed to assess pre-clinically the effect of implant design on the stability of hip endoprostheses. There is no standard protocol for these tests, and the forces applied vary between studies. This study examines the effect of the abductor force with and without application of the anterior-posterior hip contact force in the in-vitro assessment of cementless hip implant stability.

In vitro measurement of interface micromotion and crack in cemented total hip arthroplasty systems with different surface roughness.

Background: Cemented stems with various surface roughnesses are used in total hip arthroplasty. However, it is not clear how the surface roughness of the stem affects the longevity of the implant. In this study, we investigated the effect of the stem roughness on the micromotion at the bone-cement and cement-implant interface and investigated cracks in the cement layer through in vitro measurement.

Statistical analysis of interfacial gap in a cementless stem FE model.

In cementless total hip arthroplasty, a fair amount of interfacial gap exists between the femoral stem and the bone. However, the effect of these gaps on the mechanical stability of the stem is poorly understood. In this paper, a finite element model with various interfacial gap definitions is used to quantify the effect of interfacial gaps on the primary stability of a Versys Fiber Metal Taper stem under stair climbing loads.

Evaluation of the accuracy of three CT-free surgical navigation systems in total knee arthroplasty (TKA) using a coordinate measuring machine.

Previous studies have shown that the accuracy of computer-assisted surgery (CAS) via computed tomography (CT) free systems is useful when applied in the clinical realm. However, few studies have compared CAS systems to the current gold standard, manually applied measuring guides. Thirty total knee arthroplasties (TKA) were performed on artificial Sawbones knees using three different navigational systems.

Mechanical aspects of degree of cement bonding and implant wedge effect.

Background: The degree of bonding between the femoral stem and cement in total hip replacement remains controversial. Our objective was to determine the wedge effect by debonding and stem taper angle on the structural behavior of axisymmetric stem-cement-bone cylinder models.

Methods: Stainless steel tapered plugs with a rough (i.

Optimal orientation of implanted components in total hip arthroplasty with polyethylene on metal articulation.

Background: In many studies related to the total hip arthroplasty, it has been found that incorrect alignment of the total hip component is one of the major factors influencing mechanical failures. Although various recommendations for cup orientation have been presented, there were few studies that seek to determine a proper orientation of the implants based on the human motion data. The objective of this study is to determine an optimum orientation of the hip implant considering various daily activities.

Primary stability of cementless stem in THA improved with reduced interfacial gaps.

Large interfacial gaps between the stem and the bone in cementless total hip arthroplasty may prevent successful bone ingrowth at the sites, and can also be a passage for wear particles. Furthermore, interfacial gaps between the stem and the bone are believed to compromise the primary stability of the implant. Thus, a broaching method that serves to reduce gaps is expected to give clinically preferable results.

Resolving inconsistencies in defining the target orientation for the acetabular cup angles in total hip arthroplasty.

Background: Dislocation following total hip arthroplasty is a major complication and malorientation of the acetabular cup is one of the primary factors affecting dislocation. Different conventions used to describe the cup orientation produce significant variations in the recommendations for correct positioning, which in turn make it difficult for clinicians to properly interpret and apply previously reported studies.

Methods: We examined nine articles presenting recommendations for the range of target orientations of the acetabular cup to minimize the risk of dislocation (referred to as the 'safe zone').