Stress shielding in periprosthetic bone following a total knee replacement: Effects of implant material, design and alignment.

Periprosthetic bone strain distributions in some of the typical cases of total knee replacement (TKR) were studied with regard to the selection of material, design and the alignments of tibial components to examine which conditions are more forgiving than the others to stress shielding post a TKR. Four tibial components with two implant designs (cruciate sacrificing and cruciate retaining) and material properties (metal-backed (MB) and all-polyethylene (AP)) were considered in a specimen-specific finite element tibia bone model loaded in a neutral position. The influence of tibial material and design on the periprosthetic bone strain response was investigated under the peak loads of walking and stair descending/ascending.

Stress shielding in bone of a bone-cement interface.

Cementation is one of the main fixation methods used in joint replacement surgeries such as Total Knee Replacement (TKR). This work was prompted by a recent retrieval study, which shows losses up to 75% of the bone stock at the bone-cement interface ten years post TKR. It aims to examine the effects of cementation on the stress shielding of the interfacing bone, when the influence of an implant is removed.

Computation of full-field displacements in a scaffold implant using digital volume correlation and finite element analysis.

Measurements of three-dimensional displacements in a scaffold implant under uniaxial compression have been obtained by two digital volume correlation (DVC) methods, and compared with those obtained from micro-finite element models. The DVC methods were based on two approaches, a local approach which registers independent small volumes and yields discontinuous displacement fields; and a global approach where the registration is performed on the whole volume of interest, leading to continuous displacement fields. A customised mini-compression device was used to perform in situ step-wise compression of the scaffold within a micro-computed tomography (μCT) chamber, and the data were collected at steps of interest.

Techniques for cartilage repair in chondral and osteochondral defects of the knee.

Many techniques are currently used in an attempt to regenerate cartilage surfaces in the presence of a chondral or osteochondral defect. Clinical results have been mixed and no single treatment has emerged as being superior. This article reviews the techniques previously and currently being used and evidence to support their use.

TruFit CB bone plug: chondral repair, scaffold design, surgical technique and early experiences.

The TruFit CB osteochondral scaffold plug is a commercially available and licensed scaffold implant for the treatment of chondral and osteochondral defects of the knee. A number of surgical techniques have been described that are designed to achieve neocartilaginous tissue cover of a chondral defect, but many result in fibrocartilage tissue, not type II collagen hyaline cartilage. This fibrocartilage layer can fail with high shear forces in the knee joint, and lead to ongoing articular surface irregularity and subsequent secondary arthritic change.