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Background and purpose - Non-traumatic osteonecrosis is a progressive disease with multiple etiologies. It affects younger individuals more and more, often leading to total hip arthroplasty. We investigated whether there is a correlation between inducible nitric oxide synthase (iNOS) expression and osteocyte apoptosis in non-traumatic osteonecrosis. Patients and methods - We collected and studied 20 human idiopathic, non-traumatic osteonecrosis femoral heads. Subchondral bone samples in the non-sclerotic region (n = 30), collected from osteoarthritis patients, were used as controls. Spontaneously hypertensive rats were used as a model for osteonecrosis in the study. We used scanning electron microscopy, TUNEL assay, and immunohistochemical staining to study osteocyte changes and apoptosis. Results - The morphology of osteocytes in the areas close to the necrotic region changed and the number of apoptotic osteocytes increased in comparison with the same region in control groups. The expression of iNOS and cytochrome C in osteocytes increased while Bax expression was not detectable in osteonecrosis samples. Using spontaneously hypertensive rats, we found a positive correlation between iNOS expression and osteocyte apoptosis in the osteonecrotic region. iNOS inhibitor (aminoguanidine) added to the drinking water for 5 weeks reduced the production of iNOS and osteonecrosis compared to a control group without aminoguanidine. Interpretation - Our findings show that increased iNOS expression can lead to osteocyte apopotosis in idiopathic, non-traumatic osteonecrosis and that an iNOS inhibitor may prevent the progression of the disease. [ABSTRACT FROM AUTHOR]

Background and purpose Removal of distal cement at femoral implant revision is technically challenging and is associated with complications such as cortical perforations. A technique that can reduce the risks and operating time is to make a small cortical window in the distal femur for enhanced access. We wanted to determine whether the use of long, bridging, cemented femoral stems is necessary to reduce the risk of postoperative periprosthetic fractures after using an anterior cortical bone window. Methods 66 fresh pig femurs underwent mechanical testing. Steel rods were implanted at 3 locations: (1) at the distal window edge, (2) 15 mm proximally to the cortical window edge, and (3) 15 mm distally. 54 femurs were tested using a 3-point bending setup and 12 femurs were tested using a torsional load setup. Results Load to fracture ratio and bending stiffness ratio were similar in the 3 groups, for either the 3-point bending test or the torsional load test. Interpretation Our findings suggest that bypass of cortical windows with a revision femoral component may not reduce the risk of periprosthetic fracture. [ABSTRACT FROM AUTHOR]

Background and purpose The appropriate fixation method for hemiarthroplasty of the hip as it relates to implant survivorship and patient mortality is a matter of ongoing debate. We examined the influence of fixation method on revision rate and mortality. Methods We analyzed approximately 25,000 hemiarthroplasty cases from the AOA National Joint Replacement Registry. Deaths at 1 day, 1 week, 1 month, and 1 year were compared for all patients and among subgroups based on implant type. Results Patients treated with cemented monoblock hemiarthroplasty had a 1.7-times higher day-1 mortality compared to uncemented monoblock components (p < 0.001). This finding was reversed by 1 week, 1 month, and 1 year after surgery (p < 0.001). Modular hemiarthroplasties did not reveal a difference in mortality between fixation methods at any time point. Interpretation This study shows lower (or similar) overall mortality with cemented hemiarthroplasty of the hip. [ABSTRACT FROM AUTHOR]

Background and purpose Our aim was to assess in an animal model whether the use of HA paste at the cement-bone interface in the acetabulum improves fixation. We examined, in sheep, the effect of interposing a layer of hydroxyapatite cement around the periphery of a polyethylene socket prior to fixing it using polymethylmethacrylate (PMMA). Methods We performed a randomized study involving 22 sheep that had BoneSource hydroxyapatite material applied to the surface of the acetabulum before cementing a polyethylene cup at arthroplasty. We studied the gross radiographic appearance of the implant-bone interface and the histological appearance at the interface. Results There were more radiolucencies evident in the control group. Histologically, only sheep randomized into the BoneSource group exhibited a fully osseointegrated interface. Use of the hydroxyapatite material did not give any detrimental effects. In some cases, the material appeared to have been fully resorbed. When the material was evident in histological sections, it was incorporated into an osseointegrated interface. There was no giant cell reaction present. There was no evidence of migration of BoneSource to the articulation. Interpretation The application of HA material prior to cementation of a socket produced an improved interface. The technique may be useful in humans, to extend the longevity of the cemented implant by protecting the socket interface from the effect of hydrodynamic fluid flow and particulate debris. [ABSTRACT FROM AUTHOR]

Background Patella resurfacing in total knee arthroplasty is a contentious issue. The literature suggests that resurfacing of the patella is based on surgeon preference, and little is known about the role and timing of resurfacing and how this affects outcomes. Methods We analyzed 134,799 total knee arthroplasties using data from the Australian Orthopaedic Association National Joint Replacement Registry. Hazards ratios (HRs) were used to compare rates of early revision between patella resurfacing at the primary procedure (the resurfacing group, R) and primary arthroplasty without resurfacing (no-resurfacing group, NR). We also analyzed the outcomes of NR that were revised for isolated patella addition. Results At 5 years, the R group showed a lower revision rate than the NR group: cumulative per cent revision (CPR) 3.1% and 4.0%, respectively (HR = 0.75, p < 0.001). Revisions for patellofemoral pain were more common in the NR group (17%) than in the R group (1%), and “patella only” revisions were more common in the NR group (29%) than in the R group (6%). Non-resurfaced knees revised for isolated patella addition had a higher revision rate than patella resurfacing at the primary procedure, with a 4-year CPR of 15% and 2.8%, respectively (HR = 4.1, p < 0.001). Interpretation Rates of early revision of primary total knees were higher when the patella was not resurfaced, and suggest that surgeons may be inclined to resurface later if there is patellofemoral pain. However, 15% of non-resurfaced knees revised for patella addition are re-revised by 4 years. Our results suggest an early beneficial outcome for patella resurfacing at primary arthroplasty based on revision rates up to 5 years. [ABSTRACT FROM AUTHOR]

Background The identity of the vital active ingredient within synovial fluid (SF) - to which we owe the near frictionless performance of diarthrodial joints - has been the quest of researchers for many years. Initially, hyaluronic acid (HA) was thought to be the lubricant, but it has been shown not to possess the load-bearing ability required within the physiological joint. The glycoprotein fraction of synovial fluid (lubricin) has been shown to have the same lubricating ability as synovial fluid. All or part of this is thought to be due to the sur-face-active phospholipids (SAPLs) present in lubricin. We characterized the SAPLs adsorbed on the surface of retrieved prostheses which have been implicated as the boundary lubricant. Material and methods Rinsing fluids collected from the bearing surfaces of 40 prostheses removed from hip and knee revision operations were analyzed using highperformance liquid chromatography (HPLC). Results SAPLs were detected on all retrieved implants. During the study, 8 different species of phosphatidylcholines were identified. We also determined the relative concentration of each species, which suggested that the unsaturated SAPL species predominate. Interpretation It is of value to know the identity of the lubricating constituents of SF, not only for the future development of artificial joints, but also in developing cures for several disease processes in which lubrication plays a role. [ABSTRACT FROM AUTHOR]

Background Metal particles are generated during bone preparation in knee arthroplasty. These particles may produce third-body wear, or may have a role in osteolysis. Knowledge of their characteristics may help in the development of methods to reduce the amount of metal debris during bone cutting procedures. Material and methodsWe performed bony resection of the distal femur and proximal tibia on 15 pig knees, simulating a total knee arthroplasty (TKA). Metal debris was collected from the saw blades, cutting blocks and bone surfaces and cleaned for microanalysis. Results The average loss of metal from the saw blades was 1.13 mg. The average volume of a wear particle was 3.4 × 10 -16 m 3 . From this, it was estimated that approximately 500,000 particles are released from the saw blade alone. Material analysis of the particles indicated that the majority originated from the metallic cutting guides, suggesting that many millions of wear particles would be generated during the surgical procedure. Two particle shapes predominated: platelet shape and ploughed shape. Interpretation Wear particles are produced during resection for a TKA. These may enter the artificial articulation and cause accelerated wear and macrophage activation. Redesign of cutting blocks and saw blades may reduce the amount of debris produced during surgery. [ABSTRACT FROM AUTHOR]