The efficacy of β-tricalcium phosphate (β-TCP) loaded with bone morphogenetic protein-2 (BMP-2)-gene-modified bone-marrow mesenchymal stem cells (BMSCs) was evaluated for the repair of experimentally-induced osteonecrosis of the femoral head in goats. Bilateral early-stage osteonecrosis was induced in adult goats three weeks after ligation of the lateral and medial circumflex arteries and delivery of liquid nitrogen into the femoral head. After core decompression, porous β-TCP loaded with BMP-2 gene- or β-galactosidase (gal)-gene-transduced BMSCs was implanted into the left and right femoral heads, respectively. At 16 weeks after implantation, there was collapse of the femoral head in the untreated group but not in the BMP-2 or β-gal groups. The femoral heads in the BMP-2 group had a normal density and surface, while those in the β-gal group presented with a low density and an irregular surface. Histologically, new bone and fibrous tissue were formed in the macropores of the β-TCP. Sixteen weeks after implantation, lamellar bone had formed in the BMP-2 group, but there were some empty cavities and residual fibrous tissue in the β-gal group. The new bone volume in the BMP-2 group was significantly higher than that in the β-gal group. The maximum compressive strength and Young’s modulus of the repaired tissue in the BMP-2 group were similar to those of normal bone and significantly higher than those in the β-gal group. Our findings indicate that porous β-TCP loaded with BMP-2-gene-transduced BMSCs are capable of repairing early-stage, experimentally-induced osteonecrosis of the femoral head and of restoring its mechanical function

In about 50% of cases, osteonecrosis of the femoral head is known to occupy more than one site. There is controversy as to whether a single focus may increase in size. We have reviewed 606 consecutive femoral heads which had been surgically removed for osteonecrosis. Extension of osteonecrosis was observed in only two (0.3%) and was confirmed histopathologically by the enlargement of the necrotic segment beyond the repair zone formed for the primary necrosis into the adjacent, previously uninvolved bone. In both cases, the necrotic regions were wedge-shaped and occupied over 80% of the femoral head. It appears that an increase in size is extremely rare and that osteonecrosis is due to a single event. Our findings may be of value in assessing the use of joint-salvage procedures for osteonecrosis of the femoral head

The use of a composite osteochondral device for simulating partial hemiarthroplasty was examined. The device was composed of a polyvinyl alcohol hydrogel and a titanium fibre mesh, acting as artificial cartilage and as porous artificial bone, respectively. The titanium fibre mesh was designed to act as an interface material, allowing firm attachment to both the polyvinyl alcohol gel (through injection moulding) and the femoral joint surface (through bony ingrowth). We implanted 22 of these devices into canine femoral heads. Histological findings from the acetabular cartilage and synovial membrane, as well as the attachment of the prosthesis to bone, were examined up until one year after operation. No marked pathological changes were found and firm attachment of the device to the underlying bone was confirmed. The main potential application for this device is for partial surface replacement of the femoral head after osteonecrosis. Other applications could include articular resurfacing and the replacement of intervertebral discs

Osteonecrosis of the femoral head usually affects young individuals and is responsible for up to 12% of total hip arthroplasties. The underlying pathophysiology of the death of the bone cells remains uncertain. We have investigated nitric oxide mediated apoptosis as a potential mechanism and found that steroid- and alcohol-induced osteonecrosis is accompanied by widespread apoptosis of osteoblasts and osteocytes. Certain drugs or their metabolites may have a direct cytotoxic effect on cancellous bone of the femoral head leading to apoptosis rather than purely necrosis.

The pathophysiological basis of alterations in trabecular bone of patients with osteonecrosis of the femoral head (ONFH) remains unclear. ONFH has classically been considered a vascular disease with secondary changes in the subchondral bone. However, there is increasing evidence suggesting that ONFH could be a bone disease, since alterations in the functionality of bone tissue distant from the necrotic lesion have been observed. We comparatively studied the transcriptomic profile of trabecular bone obtained from the intertrochanteric region of patients with ONFH without an obvious aetiological factor, and patients with osteoarthritis (OA) undergoing total hip replacement in our Institution. To explore the biological processes that could be affected by ONFH, we compared the transcriptomic profile of trabecular bone from the intertrochanteric region and the femoral head of patients affected by this condition. Differential gene expression was studied using an Affymetrix microarray platform. Transcriptome analysis showed a differential signature in trabecular bone from the intertrochanteric region between patients with ONFH and those with OA. The gene ontology analyses of the genes overexpressed in bone tissue of patients with ONFH revealed a range of enriched biological processes related to cell adhesion and migration and angiogenesis. In contrast, most downregulated transcripts were involved in cell division. Trabecular bone in the intertrochanteric region and in the femoral head also exhibited a differential expression profile. Among the genes differentially expressed, we highlighted those related with cytokine production and immune response. This study identified a set of differently expressed genes in trabecular bone of patients with idiopathic ONFH, which might underlie the pathophysiology of this condition. Acknowledgements: This work was supported by grants PI18/00643 and PI22/00939 from ISCIII-FEDER, Ministerio de Ciencia, Innovación y Universidades (MICINN)-AES

Introduction. The most frequent diagnosis in young adults undergoing total hip arthroplasty (THA) is osteonecrosis of the femoral head (ONFH), an evolving and disabling condition with an increasing prevalence worldwide. Treatment of ONFH remains a challenge mainly because of a lack of understanding of the disease's pathophysiological basis. This study investigated the biological processes that could be affected by ONFH by comparing the microstructure, histological characteristics and transcriptomic profile of trabecular bone from the femoral head (FH) and the intertrochanteric region (IT) of patients suffering from this condition. Method. A total of 18 patients with idiopathic ONFH undergoing THA in our institution were included. Trabecular bone explants were taken intraoperatively from the FH and the IT of patients. Bone microstructure was examined by micro-computed tomography (micro-CT). After bone sectioning, histological features were studied by hematoxylin and eosin staining. Differential gene expression was investigated using a microarray platform. Result. Micro-CT imaging showed higher trabecular separation and lower trabecular thickness and bone volume in trabecular bone from the FH than from the IT. Histological staining revealed that the number of osteoblasts on the bone surface and the percentage of empty lacunae were higher in trabecular bone from the FH. Transcriptome analysis identified a differential signature in trabecular bone from the FH compared to the IT. The gene ontology analyses of the genes overexpressed in trabecular bone from the FH revealed a range of enriched biological processes related to cell division and immune response. In contrast, most downregulated transcripts were involved in bone formation. Conclusion. This study identified changes in the microarchitecture, histological features and transcriptomic signature of trabecular bone from the FH of patients with idiopathic ONFH, which might underlie the pathophysiology of this condition. This work was supported by PI22/00939 grant from ISCIII-FEDER-MICINN-AES and Luis Alvarez grant from IdiPAZ

Mesenchymal stem cells (MSC) have potent immunomodulatory and regenerative effects via soluble factors. One approach to improve stem cell-based therapies is encapsulation of MSC in hydrogels based on natural proteins such as collagen and fibrin, which play critical roles in bone healing. In this work, we comparatively studied the influence of collagen and fibrin hydrogels of varying stiffness on the paracrine interactions established by MSC with macrophages and osteoblasts. Type I collagen and fibrin hydrogels in a similar stiffness range loaded with MSC from donants were prepared by modifying the protein concentration. Viability and morphology of MSC in hydrogels as well as cell migration rate from the matrices were determined. Paracrine actions of MSC in hydrogels were evaluated in co-cultures with human macrophages from healthy blood donors or with osteoblasts from bone explants of patients with osteonecrosis of the femoral head. Lower matrix stiffness resulted in higher MSC viability and migration. Cell migration rate from collagen hydrogels was higher than from fibrin matrices. The secretion of the immunomodulatory factors interleukin-6 (IL-6) and prostaglandin E. 2. (PGE. 2. ) by MSC in both collagen and fibrin hydrogels increased with increasing matrix stiffness. Tumor necrosis factor-α (TNF-α) secretion by macrophages cultured on collagen hydrogels was lower than on fibrin matrices. Interestingly, higher collagen matrix stiffness resulted in lower secreted TNF-α while the trend was opposite on fibrin hydrogels. In all cases, TNF-α levels were lower when macrophages were cultured on hydrogels containing MSC than on empty gels, an effect partially mediated by PGE. 2. Finally, mineralization capacity of osteoblasts co-cultured with MSC in hydrogels increased with increasing matrix stiffness, although this effect was more notably for collagen hydrogels. Paracrine interactions established by MSC in hydrogels with macrophages and osteoblasts are regulated by matrix composition and stiffness

Total hip arthroplasty (THA) outcome in patients with osteonecrosis of the femoral head ONFH) are excellent, however, there is controversy when compared with those in patients with osteoarthritis (OA). Reduced mineralization capacity of osteoblasts of the proximal femur in patients with ONFH could affect implant fixation. We asked if THA fixation in patients with ONFH is worse than in those with OA. We carried out a prospective comparative case (OA)-control (ONFH) study of patients undergoing THA at our hospital between 2017 and 2019. The minimum follow-up was 2 years. Inclusion criteria were patients with uncemented THA, younger than 70 years old, a Dorr femoral type C and idiopathic ONFH. We compared the clinical (Merlé D'Aubigné-Postel score) and radiological results related with implant positioning and fixation. Engh criteria and subsidence were assessed at the immediate postoperative, 12 weeks, 6 months, 12 months and yearly. Osteoblastic activity was determined by mineralization assay on primary cultures of osteoblasts isolated from trabecular bone samples collected from the intertrochanteric area obtained during surgery. Group 1 (ONFH) included 18 patients and group 2 (OA), 22. Average age was 55.9 years old in group 1 and 61.3 in group 2. (p=0.08). There were no differences related with sex, Dorr femoral type or femoral filling. The mean clinical outcome score was 17.1 in group 1 and 16.5 in group 2 (p=0.03). There were no cases of dislocation, infection, or revision surgery in this series. There were 5 cases (28%) of femoral stem subsidence greater than 3mm within 6 first months in group 1 and 1 case (4.5%) in group 2 (p=0.05). Although there were no significant differences related to clinical results, bone fixation was slower, and a greater subsidence was observed in patients with ONFH. Greater femoral stem subsidence was associated with a lower capacity for mineral nodule formation in cultured osteoblasts. The surgical technique could influence THA outcome in patients with reduced mineralization capacity of osteoblasts

Introduction. Although osteonecrosis of the femoral head has been observed in young adult patients with autoimmune diseases such as SLE and MCTD that are treated by corticosteroids, the pathogenesis of the osteonecrosis remains unclear. We established a rat model with osteonecrosis of the femoral head by injecting lipopolysaccharide (LPS) and corticosteroid, and assessed consequences of the histopathological alteration of the femoral head, the systemic immune response, and the lipid synthesis. Methods. Male Wistar rats were given 2 mg/kg LPS intravenously on days 0 and 1 and intramuscularly 20 mg/kg methylprednisolone on days 2, 3, and 4. The animals were sacrificed 1, 2, 3, or 4 weeks after the last injection of the methylprednisolone. Histopathological and biochemical analyses were performed every week. The bone samples were then processed for routine hematoxylin and eosin staining to assess the general architecture and injury of the tissue. The triglyceride and the total cholesterol concentrations in the PRP were measured. The levels of various cytokines (IL-1α, IL-1β, IL-2, IL-4, IL-6, IL-10, GM-CSF, IFN-γ, TNF-α) in blood samples were measured. Results. The body weight of the rats over time decreased for 2 weeks but had recovered by week 4. The plasma triglyceride concentrations had decreased significantly by weeks 2 and 3. The total plasma cholesterol concentrations had increased significantly by week 1 but then decreased significantly by week 4. The plasma concentrations of IL-1?α, IL-2, IL-4, IL-6, IL-10, GM-CSF, IFN-γ and TNF-α had increased significantly by week 1. These cytokines can all be induced by toll-like receptor 4 (TLR4) signaling. We defined osteonecrosis as the diffuse presence of empty lacunae or pyknotic nuclei of osteocytes in the bone trabeculae, accompanied by surrounding bone marrow cell necrosis. Osteonecrosis of the femoral head was observed only in the epiphysis of the femoral head in sacrificed specimen every week. Histological analysis revealed osteocytic death surrounded by necrotic bone marrow with or without repaired tissue. Conclusion. We established a new rat model of corticosteroid-induced femoral head osteonecrosis. The necrosis that is generated in this model is similar to that seen in patients treated with corticosteroid. In particular, the necrotic lesion was exclusively observed in the proximal epiphysis. LPS is known to activate the immune system via the TLR4 signaling pathway. It has been recognized that the unique immunogenic effects of LPS promote autoimmune disease . LPS and methylprednisolone induced osteonecrosis of the femoral head in rats and this was associated with a disruption of the innate immune system and lipid synthesis. These findings suggest that the TLR4 signaling pathway plays an important role in the pathogenesis for osteonecrosis of the femoral head

Introduction. The purpose of this study was to evaluate the functional and radiographical mid-term follow-up results of a second generation metal-on-metal cementless total hip arthroplasty for the treatment of osteonecrosis of the femoral head in patients younger than 50 years. Methods. Twenty eight patients (35 hips) who underwent total hip arthroplasty with second generation metal-on-metal bearings for osteonecrosis of the femoral head at a minimum 5-year follow-up were included in this study. There were 5 women (6 hips) and 23 men (29 hips) who had a mean age of 40 years (range, 23 to 49 years) and a mean follow-up of 7 years. We used a Fitmore (Zimmer) cup and a 28mm Metasul femoral head in all cases. A CLS (Protek AG/Zimmer) femoral stem was used in 30 hips and a Cone prosthesis¯ (Protek AG) was used in 5 hips. Functional results were measured by Harris hip (HHS) and WOMAC scores. Radiographic evaluations were used to assess loosening and osteolysis according to Gruen and Delee and Charnley criteria. Results. The mean Harris hip score improved from 58 points (range, 35 to 67 points) pre-operatively to 92 points (range, 84 to 99 points) post-operatively, and the mean WOMAC score improved from 73 points (range, 63 to 89 points) to 30 points (range, 24 to 41 points). On radiological evaluation, all femoral and acetabular components were well-fixed without loosening or subsidence. Osteolysis was observed in 5 hips (14%) (acetabular osteolysis in 2 cases-Zone 2; 1, Zone 3; 1, femoral osteolysis in 3 cases- Zone 1; 2, Zone 7; 1). There were no complications including immediate post-operative deep infection, delayed infection, or recurrent dislocation. There was no case of revision for aseptic loosening. Conclusion. Second generation metal-on-metal cementless total hip arthroplasty for the treatment of osteonecrosis of the femoral head in patients younger than 50 years showed favorable functional and radiographic results

Introduction. The purpose of this study was to evaluate the functional and radiographical results in patients younger than 30 years who underwent cementless third generation ceramic-on-ceramic total hip arthroplasty for osteonecrosis of the femoral head. Methods. Forty one patients (55 hips) who underwent total hip arthroplasty with third generation ceramic-on-ceramic bearings for osteonecrosis of the femoral head with a minimum 4-year follow-up were included in this study. There were 26 men and 15 women who had a mean age of 26 years (range, 16 to 29 years). The average duration of follow-up was 6 years (range, 4 to 7 years). All surgeries were done by a single hip surgeon and third generation ceramic-on-ceramic articulations were used. Securefit (Stryker) acetabular components were used in 46 hips and Duraloc (Depuy) in 9 hips. Accolade (Stryker) femoral stems were used in 33 hips, cone prosthesis (Zimmer) in 18 hips and CLS (Zimmer) in 4 hips. Functional results were measured by Harris hip (HHS) and WOMAC scores. Radiographic evaluation was assessed for loosening and osteolysis according to Gruen and Delee and Charnley criteria. Results. The average HHS improved from 53 points (range, 24 to 59 points) pre-operatively to 95 points (range, 88 to 100 points) at last follow-up. WOMAC scores improved from 72 points (range, 50 to 98 points) to 25 points (range, 21 to 37 points). Thirty nine patients (51 hips) continued their normal occupation. There was no aseptic loosening, osteolysis, and no prosthesis had been revised. There was one patient who complained of continuous squeaking and two patients with Brooker grade I heterotopic ossification. There were no other major complications such as ceramic fracture. Conclusion. Total hip arthroplasty with third generation ceramic-on-ceramic bearings for osteonecrosis of the femoral head especially in active and young patients resulted in satisfactory clinical and radiological results at minimum 4 year follow-up. If long-term follow-up shows excellent results, then the age limit for total hip arthroplasty might be lowered

Introduction. The crescent sign is thought to be an early indicator of collapse in osteonecrosis of the femoral head. However, the formation mechanism of the crescent sign is still not quite clear. The purpose of this study was to utilize the two-dimensional finite element model analysis (FEA) technique to analyze mechanical function of different structures and intraosseous fluid in the femoral head under the stress of physiological loading. We wished to answer the following question: which structure or structures' failure are the main causes of collapse in osteonecrosis of the femoral head (ONFH)?. Methods. Based on two femoral head specimens obtained during THA (one with osteonecrosis of the femoral head with crescent sign formation and the other with most of the cancellous bone eroded by tumor cells without collapse), three groups of ten models were designed. Group A were standard femoral heads composed of subchondral plate, cancellous bone, intraosseous fluid, and cortical bone with 50 mm in diameter, Group B included ONFH, and Group C was based on a tumor-eroded femoral head. Previously reported mechanical property parameters were used in the FEA calculation. The strain and Von Mieses stress mechanics parameters of fifteen points (with the same coordinates) in the junction between subchondral plate and cancellous bone were harvested and compared. Results. In the model, Group B3 (around the fissure region), had strains 12 times and Von Mieses' stresses 4.5 times higher than the values in same region of Group A1. Strain and Von Mieses stresses were concentrated in the fissure region and in the junction of the subchondral plate and the cancellous bone of the necrotic region. Conclusion. All three; the subchondral plate, cancellous bone, and intraosseous fluid, together played an important role for the femoral head to bear physiological loads. It is the fissure in the subchondral plate caused by the resorption that; 1) provides a channel for the intraosseous fluid to outflow and makes the necrotic region in both the subchondral plate and the cancellous bone lose mechanical support from the intraosseous fluid, and 2) destroys the function of the subchondral plate as a thin shell structure, making the stress and strain concentrate in the junction of the subchondral plate and the cancellous bone of the necrotic region. Concentrated stress leads to fracture of the junction between the subchondral plate and the cancellous bone and the formation of a crescent sign

Introduction. The purpose of this study was to evaluate the functional and radiographical results in patients who underwent a modified minimally invasive two-incision total hip arthroplasty using large-diameter ceramic-on-ceramic articulations for osteonecrosis of the femoral head. Methods. One hundred and one patients (135 hips) who underwent unilateral minimally invasive two-incision total hip arthroplasties using large diameter ceramic-on-ceramic bearings for osteonecrosis of the femoral head with a minimum 12-months follow-up were included in this study. There were 22 women and 79 men who had a mean age of 46 years (range, 22 to 82 years). The mean follow-up was 25 months (range, 12 to 36 months). All surgeries were done by a single hip surgeon. The authors modified the original minimally invasive two-incision total hip arthroplasty technique and used large-diameter (32mm, 36mm) ceramic-on-ceramic articulations. In the lateral position, an anterolateral approach between the gluteus medius and tensor fascia lata muscles and a posterior approach between the piriformis and gluteus medius muscles was used. Functional results were measured by Harris hip (HHS) and WOMAC scores. Radiographic evaluation was assessed for positioning of the components and complications were assessed. Results. The mean Harris hip score improved from 43 points (range, 13 to 58 points) pre-operatively to 96 points (range, 73 to 100 points) post-operatively and the mean WOMAC score improved from 67 points (range, 50 to 98 points) to 28 points (range, 26 to 39 points). On radiological evaluation, the mean lateral opening angle of the acetabular component was 35.9 degrees (range, 27.1 degrees to 47.4 degrees) and the mean stem position was valgus 2.4 degrees (range, varus 2.7 degrees to valgus 5.3 degrees). One patient suffered an intra-operative femur fracture and another underwent revision surgery due to stem subsidence. There were no complications such as immediate post-operative deep infection, delayed infection, or recurrent dislocation. Conclusion. A modified minimally invasive two-incision total hip arthroplasty using large-diameter ceramic-on-ceramic articulation for osteonecrosis of the femoral head is safe and reproducible in terms of achieving proper implant positioning and early functional recovery. In particular, the complication rates encountered, especially dislocation, were low

Introduction. Since 2005, we have performed implantation of bone marrow-derived mononuclear cells for osteonecrosis of the femoral head in order to improve vascularization and bone repair. This study focused on early bone repair of osteonecrosis of the femoral head after transplantation of bone marrow-derived mononuclear cells (BMMNC). Patients and Methods. Twenty-two patients (30 joints) who had bilateral osteonecrosis followed for more than 2 years after BMMNC implantation were evaluated. Eight women and 14 men were included. Their mean age at surgery was 41 years (range, 18 to 64 years) and the mean follow-up period was 31 months. Pre-operative stage according to the ARCO classification was Stage 2 in 25 joints and Stage 3 in 5 joints. The mean volume ratio of osteonecrosis was 21%. For preparing BMMNC, about 700ml of bone marrow was aspirated from the ilium and centrifuged using a Spectra cell separator (Gambro). The BMMNC were seeded to interconnected porous calcium hydroxyapatite (IP-CHA) and implanted to the osteonecrotic lesion. As a control, cell-free IP-CHA was implanted for 8 patients (9 joints). A woman and 7 men were included. The mean age at surgery was 49 years (range, 28 to 73 years) and the mean follow-up period was 37 months. Preoperative stage was stage 2 in all patients. The mean volume ratio of osteonecrosis was 22%. At post-operative evaluations; progression of collapse, consolidation at reactive zone, post-operative course of volume rate of osteonecrosis, and bone absorption at osteonecrosis was assessed. Results. Shrinkage of osteonecrosis has been observed subsequent to bone consolidation at the transitional zone which progressed from 3 to 6 months post-operatively in the BMMNC-seeded group. Progression of collapse more than 2 mm was detected in 4 joints (13%), and hip arthroplasty was performed in 1 joint (3%). Consolidation at the reactive zone was detected in 28 joints (93%) and the volume rate of osteonecrosis significantly decreased by 12 months after surgery. Bone resorption at the osteonecrotic lesion was observed in 14 joints (47%). Meanwhile, subtle bone consolidation was detected after 12 months post-operatively in the control group. Progression of collapse was observed in 6 joints (67%) and further surgical treatments were needed in 3 joints (33%). Conclusion. This study found that BMMNC was beneficial to osteonecrosis of the femoral head from the viewpoint of prevention of collapse

Introduction and Objective. Mesenchymal stem cells (MSC) are attractive candidates for bone regeneration approaches. Benefits of MSC therapy are mainly attributed to paracrine effects via soluble factors, exerting both immunoregulatory and regenerative actions. Encapsulation of MSC in hydrogels prepared with extracellular matrix (ECM) proteins has been proposed as a strategy to enhance their survival and potentiate their function after implantation. Functional activity of MSC can be regulated by the physical and mechanical properties of their microenvironment. In this work, we investigated whether matrix stiffness can modulate the crosstalk between MSC encapsulated in collagen hydrogels with macrophages and osteoblasts. Materials and Method. Collagen hydrogels with a final collagen concentration of 1.5, 3 and 6 mg/mL loaded with human MSC were prepared. Viscoelastic properties of hydrogels were measured in a controlled stress rheometer. Cell distribution into the hydrogels was examined using confocal microscopy and the levels of the immunomodulatory factors interleukin-6 (IL-6) and prostaglandin E. 2. (PGE. 2. ) released by MSC were quantified by immunoassays. To determine the effect of matrix stiffness on the immunomodulatory potential of MSC, human macrophages obtained from healthy blood were cultured in media conditioned by MSC in hydrogels. The involvement of IL-6 and PGE. 2. in MSC-mediated immunomodulation was investigated employing neutralizing antibodies. Finally, the influence of soluble factors released by MSC in hydrogels on bone-forming cells was studied using osteoblasts obtained from trabecular bone explants from patients with osteonecrosis of the femoral head during total hip arthroplasty. Results. MSC loaded in hydrogels containing varying concentrations (1.5, 3 and 6 mg/mL) of collagen were viable. Rheology measurements determined that the hydrogel stiffness increased with increasing collagen concentration. Encapsulation of MSC into hydrogels barely affected their storage modulus values. MSC acquired a three-dimensional (3D) arrangement in all hydrogels and showed a more elongated shape in hydrogels with higher stiffness. The secretion of IL-6 and PGE. 2. by MSC in hydrogels increased with increasing matrix stiffness. Media conditioned by MSC encapsulated in stiffer hydrogels decreased TNF-α levels secreted by macrophages to a higher extent than media conditioned by MSC in softer hydrogels. This effect was partially mediated by PGE. 2. Finally, our preliminary results indicated that factors released by MSC in hydrogels regulated osteoblast-mediated mineralisation and this effect was dependent on hydrogel stiffness. Conclusions. Our data indicate that matrix stiffness of collagen hydrogels regulates the production of soluble factors by MSC and their paracrine actions on macrophages and osteoblasts

Introduction. Alumina ceramic-on-highly cross-linked polyethylene bearings (Al-on-X-linked PE) are attractive because of the potential for reduced wear, osteolysis and loosening of the component. The purpose of this study was to evaluate the clinical and radiographic outcomes of cementless total hip arthroplasties (THAs) using an Al-on-X-linked PE bearing and to determine the rates of osteolysis using radiographs and computer tomographic (CT) scans in young patients with osteonecrosis of femoral head. Methods. Consecutive primary cementless THAs using Al-on-X-linked PE bearing were performed in 71 patients (73 hips) who were younger than 50 years of age with osteonecrosis of the femoral head. There were 48 men (51 hips) and 23 women (23 hips). The average age at the time of the index arthroplasty was 46 years (range, 20 to 50 years). Osteolysis was evaluated using radiographs and CT scanning. The average follow-up was 11 years (range, 10 to 13 years). Results. The mean preoperative Harris hip score was 51 points (range, 27 to 55 points), which was improved to 96 points (range, 85 to 100 points) at the final follow-up. Preoperative functional activity was improved significantly (p=0.001) at the latest follow-up. All acetabular and femoral components were fixed by bone ingrown. The mean polyethylene linear penetration was 0.05 ?0.02 mm per year (range, 0.02 mm to 0.08 mm per year). Radiographic and CT scan evaluation demonstrated that no acetabular or femoral osteolysis was detected in any hip at the latest follow-up. Conclusion. The current generation of anatomic tapered cementless femoral component with Al-on-X-linked PE bearing is functioning well with no osteolysis at a 10-year minimum and average of 11-year follow-up in this series of young patients with osteonecrosis of the femoral head

Introduction. The purpose of this study was to evaluate the functional and radiographical results in patients who underwent a modified minimally invasive two-incision total hip arthroplasty using large-diameter metal-on-metal articulations for osteonecrosis of the femoral head. Methods. From December 2007 to July 2008, 45 hips (33 patients) underwent total hip arthroplasty for the treatment of osteonecrosis of the femoral head. There was 1 woman (2 hips) and 32 men (43 hips) who had a mean age of 39 years (range, 22 to 64 years). The minimum follow-up was 12 months (range, 12 to 19 months). The authors modified the original minimally invasive two-incision total hip arthroplasty technique and used large-diameter metal-on-metal articulations. In the lateral position, an anterolateral approach was used between the gluteus medius and tensor fascia lata muscles and for the posterior approach the muscle plane was between the piriformis and gluteus medius muscles. The acetabular components, Durom¯ (Zimmer) in 20 hips and Magnum¯ (Biomet) was used in 25 hips. M/L taper¯ (Zimmer) femoral stems were used in all cases. The size of the femoral heads were 38 mm (1 hip), 40 mm (3 hips), 42 mm (13 hips), 44 mm (18 hips), 46 mm (5 hips), 48 mm (4 hips) and 50 mm (1 hip). Postures such as excessive flexion or adduction which cause dislocation were not restricted, post-operatively. Functional results were measured by Harris hip scores (HHS), WOMAC scores, and range of motion. Radiographic evaluation was assessed for positions of components and post-operative complications were noted. Results. Mean operation time was 72 minutes (range, 54 to 94 minutes). The mean Harris hip score improved from 50 points (range, 38 to 73 points) pre-operatively to 96 points (range, 84 to 100 points) post-operatively, and the mean WOMAC score improved from 68 points (range, 50 to 93 points) to 28 points (range, 26 to 34 points). The mean flexion improved from 85° pre-operatively to 122° post-operatively. The mean internal rotation improved from 2.5° pre-operatively to 25.3° post-operatively. The mean external rotation improved from 31.8° pre-operatively to 60.1° post-operatively. The mean abduction improved from 24.0° pre-operatively to 41.6° post-operatively. The mean adduction improved from 19.4 ° pre-operatively to 26.6° post-operatively. All patients were able to sit cross legged and squat. On radiological evaluation, the mean lateral opening angle of the acetabular component was 39.4° (range, 32.2°-48.5°) and the mean stem position was valgus 0.3° (range, varus 2.8° to valgus 2.0°). At last follow-up, all femoral and acetabular components were well-fixed without loosening or subsidence. There were no complications such as dislocation, immediate post-operative deep infection or delayed infection. Conclusion. Modified minimally invasive two-incision total hip arthroplasty using large-diameter metal-on-metal articulations for osteonecrosis of the femoral head results in satisfactory early clinical and radiologic results

Osteonecrosis of the femoral head is a complex pathologic process with many aetiological factors. Factors most often mentioned in the literature are mechanical disruption (hip trauma or surgery), steroid use, smoking, haemoglobinopathies and hyperlipidaemia. 1. Our case depicts a rare association of crack cocaine related to osteonecrosis of the femoral head which has never been reported in the available literature. Case Report: A 32 year old man was referred to our Orthopaedic clinic with right hip pain. He had a 9 pack-year history of cigarette smoking and had also smoked crack cocaine between ages 20 to 28; shortly after this the hip pain started. He denied antecedent injury. He had undergone a steroid injection into his right ankle abroad for swelling one year before referral, which was after onset of hip pain. MRI of his hip previously performed abroad had been normal. The patient had an indoor job and was otherwise fit and well. On examination he had reduced of movement in his right hip with 5–10 degrees of fixed flexion deformity. Plain radiography demonstrated cyst formation and sclerosis of both femoral heads. Repeat MRI confirmed bilateral osteonecrosis, worse on the right with risk of head collapse. The patient underwent bilateral core decompressions. Subsequent follow-up demonstrated a mobile patient with no need for arthroplasty and he was discharged after two years. Osteonecrosis is caused by the coagulation of the intra-osseous microcirculation leading to thrombosis formation and eventual reduction in osseous blood supply. Steroid use is associated with increased risk of osteonecrosis to the femoral head, however in these cases the patients often undergo either direct local or systemic infiltration of steroid. In this case steroid was administered after symptoms began to a far distant site and therefore cannot be the cause. Cigarette smoking is also known to cause osteonecrosis. Our patient had smoked cigarettes for fourteen years without problems, and it was after he ceased to smoke crack cocaine that his symptoms began. Cocaine blocks voltage-gated sodium-channels causing vasospasm. It is known to cause nasal and facial bone osteonecrosis due to its common intranasal method of delivery. We postulate that in this case crack cocaine was a synergistic factor towards development of femoral head osteonecrosis

Introduction. The different types of treatment for osteonecrosis of the femoral head have not led to a consensus about which treatment is best for the different stages. Particularly in the later stages of osteonecrosis, the disease still progresses to destruction of the femoral dome. The purpose of our study was to check the outcome of bone impaction grafting used for the head-preserving treatment of severe femoral head osteonecrosis. In order to preserve the femoral head, the sphericity and mechanical properties of the femoral dome must be contained and further collapse prevented. Methods. In this prospective study, we included 28 hips in 27 patients who had severe complaints of pain due to an extensive osteonecrotic lesion. The mean age of the patients was 33 years with a mean follow up time of 42 months. Results. Eight patients (29%) underwent a conversion to a total hip arthroplasty. The pre-operative Harris hip score for all cases was 55 points and the post-operative score was 79 points. Fifty-four percent of all cases showed a radiological and sixty-four percent a clinical success. The clinical success rate of Stage 2 was 73%, of early Stage 3, 67%, and late Stage 3, 45%. Conclusion. In conclusion, we can state that the bone impaction grafting technique shows promising results and is an excellent addition for the treatment arsenal for osteonecrosis of the femoral head

Introduction. Osteonecrosis of the femoral head occurs in young patients. The preservation of the hip joint is vitally important, because hip arthroplasty does not guarantee satisfactory long-term results in young and active patients. Curved intertrochanteric varus osteotomy is one of several joint preserving procedures used for this disease. Methods. Between June 2004 and June 2007, 52 patients (55 hips) who had osteonecrosis of the femoral head were treated with curved intertrochanteric varus osteotomy. There were 29 men and 23 women who had a mean age at the time of osteotomy of 33 years (range, 18 to 52 years). The osteotomy was fixed with a 120 degree compression hip screw in the first 34 hips and with a 95 degree dynamic condylar screw in the remaining 21 hips. Clinical evaluation was performed using the scoring system of Merle d'Aubigne et al. Results. The mean duration of follow-up was 32 months (range, 24 to 60 months). Six patients (six hips) required a total hip arthroplasty, due to loss of fixation in two hips, shortening of the operated limb in two hips, and further collapse with persistent pain in two hips. In two patients (two hips), the plate fractured at 3 and 4 months after the operation, which was changed to a new plate. Thus, 49 of the 55 hips survived at a mean follow-up 32 months. In these hips, the mean Merle d'Aubigne hip score was 17.4 points at the latest evaluation. Conclusion. Curved intertrochanteric varus osteotomy is a satisfactory joint preserving method to treat osteonecrosis of the femoral head