A preclinical study of stem subsidence and graft incorporation after femoral impaction grafting using porous hydroxyapatite as a bone graft extender

Early acetabular cartilage wear following hemiarthroplasty: An ovine model

Objectives: Hemiarthroplasty induces degenerative changes in the hip joint, which are difficult to evaluate in vivo. Radiostereometric analysis (RSA) is a radiographic measurement technique that has recently been used to measure acetabular cartilage wear in vivo. The aim of the study was to measure acetabular cartilage wear, using this technique, in an ovine model during the first 14 weeks post-implantation.

Methods: Measurements of three-dimensional femoral head migration, combined with visual assessments at necropsy and safranin O staining for cartilage integrity, were undertaken.

Results: Mean femoral head migration during the first six weeks was 0.525 mm in the medial, 0.144 mm in the cranial, and 0.517 mm in the dorsal direction. The majority of this migration was confirmed to be cartilage wear in the medial and dorsal aspects of the acetabulum at necropsy and with subsequent histological evaluation depicting significant cartilage degeneration.

Clinical significance: Radiostereometric analysis is the current gold standard technique for in vivo assessment of implant migration following total hip replacement. This study has utilized RSA to quantify the amount of early cartilage wear in vivo, which was supported by ex vivo evaluations. Accurately measuring the amount of cartilage wear will allow future studies to compare component material and design characteristics prior to clinical use.

Staged total hip arthroplasty in a patient with hip dysplasia and a large pertrochanteric bone cyst

Hip arthroplasty in young patients requires thoughtful preoperative planning. Patients with proximal femoral bone loss complicate this planning and may require a staged procedure to optimize implant insertion. We report on a case of a 26-year-old woman with secondary hip arthritis from developmental dysplasia of the hip and a large pertrochanteric bone cyst that was treated with staged total hip arthroplasty. The cyst was decompressed and filled with an osteoconductive and osteoinductive bone graft substitute called EquivaBone. One year later, the patient underwent a successful primary total hip arthroplasty. Fifteen-month follow-up after her hip replacement revealed resolution of postoperative pain and significant functional improvement.

Management of periprosthetic femoral fractures following total hip arthroplasty: a review

PURPOSE

As the number of total hip arthroplasties (THAs) is increasing, the expected number of periprosthetic femur fractures is also expected to increase. As such, a thorough grasp of the evaluation and management of patients with periprosthetic femur fractures is imperative, and discussed in this review.

METHODS

This review discusses the epidemiology, classification, and management of periprosthetic femur fractures in an evidence-based fashion.

RESULTS

Periprosthetic fracture management starts with assessing stem stability and bone quality. Well-fixed stems require fracture fixation without stem revision, while loose stems require revision THA.

CONCLUSIONS

Periprosthetic femoral fractures after primary total hip arthroplasty are a complex and clinically challenging issue. The treatment must be based on the fracture, the prosthesis, and the patient (Table 1). The Vancouver classification is not only helpful in classifying the fractures, but also in guiding the treatment. In general, well-fixed stems require open reduction and internal fixation, whereas loose stems require revision arthroplasty.

Preclinical trial of a novel surface architecture for improved primary fixation of cementless orthopaedic implants

BACKGROUND

A new surface architecture for cementless orthopaedic implants (OsteoAnchor), which incorporates a multitude of tiny anchor features for enhancing primary fixation, was tested in an ovine hemi-arthroplasty pilot study.

METHODS

Test animals were implanted with a hip stem component incorporating the OsteoAnchor surface architecture produced using additive layer manufacturing and control animals were implanted with stems containing a standard plasma sprayed titanium coating.

FINDINGS

Intra-operative surgeon feedback indicated that superior primary fixation was achieved for the OsteoAnchor stems and rapid return to normal gait and load bearing was observed post-operation. Following a 16-week recovery time, histological evaluation of the excised femurs revealed in-growth of healthy bone into the porous structure of the OsteoAnchor stems. Bone in-growth was not achieved for the plasma sprayed stems.

INTERPRETATION

These results indicate the potential for the OsteoAnchor surface architecture to enhance both the initial stability and long term lifetime of cementless orthopaedic implants.

Stem micromotion after femoral impaction grafting using irradiated allograft bone: a time zero in vitro study

BACKGROUND

A gamma irradiation dose of 15kGy has been shown to adequately sterilise allograft bone, commonly used in femoral impaction bone grafting to treat bone loss at revision hip replacement, without significantly affecting its mechanical properties. The objective of this study was to evaluate whether use of 15kGy irradiated bone affects the initial mechanical stability of the femoral stem prosthesis, as determined by micromotion in a comprehensive testing apparatus, in a clinically relevant time zero in vitro model of revision hip replacement.

METHODS

Morselised ovine bone was nonirradiated (control), or irradiated at 15kGy or 60kGy. For each dose, six ovine femurs were implanted with a cemented polished taper stem following femoral impaction bone grafting. Using testing apparatus that reproduces stem loading, stems were cyclically loaded and triaxial micromotion of the stem relative to the bone was measured at the proximal and distal stem regions using non-contact laser transducers and linear variable differential transformers.

FINDINGS

There were no significant differences in proximal or distal stem micromotion between groups for all directions (p≤0.80), apart for significantly greater distal stem medial-lateral micromotion in the 60kGy group compared to the 15kGy group (P=0.03), and near-significance in the anterior-posterior direction (P=0.08, power=0.85).

INTERPRETATION

Using a clinically relevant model and loading apparatus, irradiation of bone at 15kGy does not affect initial femoral stem stability following femoral impaction bone grafting.