Orthopaedics and Trauma

Background: A gamma irradiation dose of 15 kGy 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 15 kGy 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 15 kGy or 60 kGy. 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 60 kGy group compared to the 15 kGy 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 15 kGy does not affect initial femoral stem stability following femoral impaction bone grafting.

This study investigates receptor activator NF-kappaB (RANK), RANK ligand (RANKL) and tumour necrosis factor (TNFalpha), key factors regulating bone turnover, present in the tissues near peri-prosthetic osteolysis. Tissue was obtained from zones of peri-prosthetic osteolysis from 11 patients undergoing revision of total hip prostheses, analysed preoperatively by high-resolution spiral multislice CT using a metal artefact suppression protocol. Synovial tissue from 10 patients with osteoarthritis undergoing primary hip replacement was used as control tissue. Immunohistochemical analysis of formalin fixed tissue sections demonstrated that RANK, RANKL and TNFalpha were strongly expressed by large multinucleated cells containing polyethylene wear debris in revision tissues. Control tissue stained weakly for RANK, RANKL and TNFalpha. A strong statistical correlation (p<0.02) was found between the five parameters, volume of bone loss, polyethylene wear debris, RANK, RANKL and TNFalpha ex...