Bone ingrowth is desired with uncemented hip implants. Infection is clearly undesirable. We have worked on developing a nanofiber coating for implants that would enhance bone formation while inhibiting infection. Few studies have focused on developing an implant surface nanofiber (NF) coating to prevent infection and enhance osseointegration by local drug release. In this study, coaxial doxycycline (Doxy)-doped polycaprolactone/polyvinyl alcohol (PCL/PVA) Nanofibers were directly deposited on the titanium (Ti) implant surface during electrospinning.

The interaction of loaded Doxy with both PVA and PCL NFs was characterized by Raman spectroscopy. The bonding strength of Doxy-doped NF coating on Ti implants was confirmed by a stand single-pass scratch test. The improved implant osseointegration by PCL/PVA NF coatings in vivo was confirmed by scanning electron microscopy, histomorphometry and micro computed tomography at 2, 4 and 8 weeks after implantation. The bone contact surface (%) changes of NF coating group (80%) is significantly higher than that of no NF group (< 5%, p<0.05). Finally, we demonstrated that Doxy-doped NF coating effectively inhibited bacterial infection and enhanced osseointegration in an infected (Staphylococcus aureus) tibia implantation rat model. Doxy released from NF coating inhibited bacterial growth up to 8 weeks in vivo. The maximal push-in force of Doxy-NF coating (38 N) is much higher than that of NF coating group (6.5 N) 8 weeks after implantation (p<0.05), which was further confirmed by quantitative histological analysis and micro computed tomography.

These findings indicate that coaxial PCL/PVA NF coating doped with Doxy and/or other drugs have great potential in enhancing implant osseointegration and preventing infection.

The purpose of the study was to evaluate the outcome of curettage and grafting with calcium sulfate pellets for progressive retroacetabular osteolysis with retention of the acetabular component. Seven patients who underwent the procedure were evaluated clinically and radiographically at an average follow-up time of fifteen months. There was no progression of osteolysis following curettage and grafting with good to excellent osseo-integration. All patients had a good functional outcome with no pain during follow-up. Curettage and synthetic grafting of retroacetabular cysts with calcium sulfate pellets is a viable option in halting the progression of retroacetabular lysis and promoting osseous recovery. The purpose of this study was to evaluate outcome of curettage and grafting of progressive retroacetabular osteolysis with calcium sulfate pellets and retention of components. Restoration of retroacetabular bone stock by curettage and grafting with synthetics would obviate the need for autogenous bone graft and its associated risks. Retention of well-fixed acetabular components also aids in prevention of further bone loss associated with component extraction. We conducted a clinical and radiographic review of seven patients who presented to the senior author with radiographic findings of progressive retroacetabular osteolysis. All patients were treated with curettage and filling of the defects with calcium sulfate. Mean follow-up time is fifteen (five to twenty-seven) months. Polyethylene wear was noted in all cases. The size of the lesions ranged from 3.1 x 2.0 to 9.0 x 5.3 cm. On follow-up evaluation, there was no recurrence or progression of the lesions. Osseo-integration was excellent in four cases and good in three cases. All patients had returned to normal level of function with no pain. Patients with retroacetabular osteolysis are often asymptomatic until catastrophic failure occurs as a result of extensive bone loss. Treatment of retroacetabular osteolysis in the setting of well-fixed components is controversial. Retention of the components, curettage and synthetic grafting with calcium sulfate is a viable option to prevent progression of lysis and stimulate bone formation. Curettage and grafting of progressive retroacetabular osteolysis with calcium sulfate and retention of components results in good osseo-integration of the graft and halts the progression of lysis

This preliminary report demonstrates the effective use of Apapore in the management of benign cystic bone lesions. The use and development of bone graft substitutes over the past ten years has increased dramatically to improve their osseo-integration to a level similar to autografting techniques without the drawbacks of comorbidity from the graft site. Apapore is a synthetic bone graft substitute which consists of a scaffold of synthetic phase-pure hydroxy apatite with micro- and macroporosity and inter-connectivity to favour bone repair. Nineteen patients (12M:7F) with a mean age of 18.6years (8–33 years) having had procedures for the management of benign cystic lesions of bone with grafting using Apapore were followed up retrospectively for a mean period of 8 months (1–16months). In each case the diagnosis of a benign cystic lesion was made histologically prior to surgery. The subsequent definitive procedure was performed by a consultant on the Bone Tumour Unit at the Royal National Orthopaedic Hospital (Stanmore) in each case involving curettage and impaction of Apapore into the cavity in a standard fashion as a general anaesthetic procedure in the operating theatre. There have been no complications to date. All patients have made uneventful recoveries. Short-term radiological follow-up demonstrates excellent incorporation of the bone graft substitute and osseo-integration

We present a prospective study focused on radiographic long-term outcomes and bone remodeling at a mean of 17.0 years (range: 15 to 20) in 208 cementless fully HA-coated femoral stems (Corail®, DePuy, Johnson & Johnson). Total hip replacements in this study were performed by three members of the surgeon design team (Artro Group) in France between 1986 and 1991. Radiographic evaluation focused on periprosthetic osteolysis, bone remodeling, osseous integration, subsidence, metaphyseal or diaphyseal load transfer, and femoral stress shielding. The radiographs were digitized and examined with contrast enhancing software (DICOM Anonymizer 1.1.2) for analysis of the trabecular architecture. Radiographic signs of aseptic stem loosening were visible in two cases (1%). Three stems (1.4%) showed metaphyseal periprosthetic osteolysis in two of seven Gruen zones associated with eccentric polyethylene wear awaiting metaphyseal bone grafting and cup liner exchange. One stem (0.5%) was revised due to infection. No stem altered in varus or valgus alignment more than two degrees and mean subsidence was 0.1 mm (range: 0 to 2) after a mean of 17.0 years. Five stems (2.4%) required or are awaiting revision surgery. Trabecular orientation and micro-anatomy suggested proximal load-transfer patterns in all except three cases (98.6%). Combined metaphyseal and diaphyseal osseo-integration and bone remodeling were visible in one hundred stems (48%). Diaphyseal stress shielding and cortical thickening were observed in three stems (1.4%). Other radiographic features are discussed in depth. This long-term study of 208 fully HA-coated Corail stems showed highly satisfactory osseo-integration and fixation in 97.6% after a mean of 17.0 years follow-up

Decellularised extracellular matrix scaffolds show great promise for the regeneration of damaged musculoskeletal tissues (cartilage, ligament, meniscus), however, adequate fixation into the joint remains a challenge. Here, we assess the osseo-integration of decellularised porcine bone in a sheep model. This proof-of-concept study supports the overall objective to create composite decellularised tissue scaffolds with bony attachment sites to enable superior fixation and regeneration. Porcine trabecular bone plugs (6mm diameter, 10mm long) were decellularised using a novel bioprocess incorporating low-concentration sodium dodecyl sulphate with protease inhibitors. Decellularised bone scaffolds (n=6) and ovine allograft controls (n=6) were implanted into the condyle of skeletally mature sheep for 4 and 12 weeks. New bone growth was visualised by oxytetracycline fluorescence and standard resin semi-quantitative histopathology. Scaffolds were found to be fully decellularised and maintained the native microarchitecture. Following 4-week implantation in sheep, both scaffold and allograft appeared well integrated. The trabecular spaces of the scaffold were filled with a fibro-mesenchymal infiltrate, but some areas showed a marked focal lymphocytic response, associated with reduced bone deposition. A lesser lymphocytic response was observed in the allograft control. After 12-weeks the lymphocytic reaction was minimised in the scaffold and absent in allografts. The scaffold showed a higher density of new mineralized bone deposition compared to allograft. New marrow had formed in both the scaffold and allografts. Following the demonstration of osteointegration this bioprocess can now be transferred to develop decellularised composite musculoskeletal tissue scaffolds and decellularised bone scaffolds for clinical regeneration of musculoskeletal tissues

It is well documented that implant loosening rate in sickle cell disease patients is higher than that seen in patients with hip arthroplasty from other indications. The Hypoxic inducible factor(HIF) - is activated in the microcellular hypoxic environment and this through a cascade of other enzymatic reactions promotes the activity of other factors and further help enhance angiogenesis and osteogenesis. The aim of this study was to investigate and propose a potential model for investigating osseointegration in a hypoxic microcellular environment using osteoblasts(MG63). Human MG63 osteoblastic cells were cultured under normoxia and hypoxic conditions (20%; and 1% oxygen saturation) for 72 hours under two different condition- with and without cobalt chloride. The samples cultured under normoxic condtions without cobalt chloride acted as control. Using qualitative polymerase chain reaction-(qPCR) - HIF expression was assessed under the above conditions in relation to the control. The results showed there was significant expression of the HIF 1 alpha protein under hypoxic condition with cobalt chloride in comparison with the control samples- all at 72hours incubation. Mann-Whitney U test was used to deduce level of significance of fold change.(p=0.002; <0.05). This was deemed as being a significant difference in the level of expression of HIF compared to the control. The results show that the hypoxic inducible factor can be expressed using the above tested. experimental invitro-model with significant results which can be a foundation for further research into improving hip implant prosthesis design to help enhance osseo-integration in sickle cell disease patient with AVN

Bone healing especially in elderly patients is a complex process with limited therapeutic options. In recent years the use of BMP2 for fracture healing is investigated extensively. However, for many applications superficial amounts of BMP2 were required for efficacy due to the absence of sustained release carriers and severe side effects have reported thereby limiting the use of BMP2. Here we present an alternative method based on the use of a combination of low molecular weight compounds, testosterone and alendronate, with established safety profiles in men. Moreover, in contrast to BMP2 which activates both osteoblasts and osteoclasts, this combination of drugs enhances osteoblast activity but simultaneously inhibits osteoclast activity resulting in a net effect of bone growth. Human primary osteoblasts were obtained from bone of patients requiring knee prostheses and cultured in the presence of various concentrations testosterone with and without alendronate. Optimal concentrations were selected and used to stimulate 5×8 mm porcine bone biopsies for 4 weeks. Medium was exchanged regularly and ALP activity was determined. At endpoint biopsies were analyzed in a MicroCT (Bruker Skyscan 1076) to analyze bone volume (BV), trabecular thickness (Tb.Th) and tissue volume (TV). Bone strength was measured using Hounsfield (H10KT) test equipment. The data obtained showed a significant and dose dependent increase in ALP activity of primary osteoblasts (day 7–10) indicating robust activation of osteoblast activity. Optimal and synergistic ALP activation was observed when treating cells with 15–375 nM testosterone in combination with 2 μM alendronate. Significant inhibition (75%) of osteoclast activity was observed by alendronate (2–10 μM) which was further enhanced by high testosterone levels. This concept was further tested in bovine bone biopsies cultured for 4 weeks in the presence of 75 nM testosterone and 2 μM alendronate. MicroCT analysis of the biopsies revealed a ± 40% increase in both bone volume (trabecular and cortical bone) and bone strength. Moreover bone mineral density was increased by 20% indicating increased mineralization of bone tissue. Treatment of human primary osteoblasts or human or bovine bone explants with a combination of an androgen (testosterone) and a bisphosphonate (alendronate) significantly enhance bone growth and bone mineral density. Moreover, bone strength was increased indicating the formation of high quality bone tissue. These findings are the basis for the development of sustained release materials to be applied locally at the bone fracture site, which would allow for low amounts of the drugs and no systemic exposure. By encapsulating testosterone and alendronate in a biodegradable polymer coating, a sustained release up to 5 weeks can be achieved, and the loaded coating can be applied in combination with collagen membranes to improve bone healing or as a coating onto implants to improve osseo-integration

Cementless arthroplasty has progressed substantially in the recent decades from pressfit implantation to porous-coated and later HA-coated implant fixation as its ultimate current state-of-the-art incarnation. As a consequence ever younger and older patients have received the benefits of hip and other arthroplasty although attention to age-related factors is key to success. Key factors for success, from the implant perspective, are adequate primary stability of the device in the bone supported by design and surface structure variables that together with optimal implant biocompatibility result in durable osseo-integration of the device. The high activity levels of younger patients but similarly the generally inferior muscular condition of elderly patients require special attention for the stability of the hip joint with avoidance of impingement. Also bone quality may be a topic for consideration to avoid problems. Excellent survival rates past twenty years are documented in both literature and registries with quantitative studies confirming the excellent implant stability and bone quality. With an optimal consideration for patient related factors as well as anatomic reconstruction of the arthroplasty, modern cementless arthroplasty provides every patient an outlook on both excellent long term functionality and survival

Objectives. Osteoporosis and osteomalacia lead to increased fracture risk. Previous studies documented dysregulated osteoblast and osteoclast activity, leading to a high-turnover phenotype, reduced bone mass and low bone mineral content. Osteocytes, the most abundant bone cell type, are involved in bone metabolism by enabling cell to cell interaction. Osteocytes presence and viability are crucial for bone tissue homeostasis and mechanical integrity. Osseo-integration and implant degradation are the main problems in developing biomaterials for systemically diseased bone. This study examines osteocyte localisation, morphology and on the implant surface and at the implant bone interface. Furthermore, the study investigates ECM proteins regulation correlated to osteocytes and mechanical competence in an ovariectomised rat model with a critical size metaphyseal defect. Methodology. After induction of osteoporosis, 60 female Sprague-Dawley rats were randomised into five groups: SrCPC (n=15), CPC (n=15), ScB30 (n=15), ScB30Sr20 (n=15) and empty defect (n=15). The left femur of all animals underwent a 4mm wedge-shaped metaphyseal osteotomy that was internally fixed with a T-shaped plate. The defect was then either filled with the above mentioned implants or left empty. After six weeks, histomorphometric analysis showed a statistically significant increase in bone formation at the tissue-implant interface in the SrCPC group compared to the other groups (p<0.01). Osteocyte morphology and networks were detected using silver and staining. ECM proteins were investigated through immunohistochemistry. Cellular populations were tested using enzyme histochemistry. Mineralisation was assessed using time of flight secondary ion mass spectrometry (TOF-SIMS). Statistical analysis was performed using Mann Whitney U test with Bonferroni correction. Results. In the SrCPC and compared to other test groups, osteocytes presence and morphology was enhanced. An increased osteocytic activity was also seen in ScB30Sr20 when compared to SCB30 alone. Local osteomalatic lesions characterised by the presence of excessive unmineralised osteoid as revealed by the VKVG staining in the intact bone was also seen. A regular pattern of osteocytes distribution reflecting a better bone maturation was also seen in case of the Sr substituted cements. Whereas in case of the ScB30 degenerated osteocytes with a comparatively irregular arrangement were seen. Nonetheless, ECM proteins indicating discrepant bone turnover (RANKL, OPG, BMP2, OCN; ASMA) were noticed to increase within these regions and were accompanied by the presence of apoptotic osteocytes. Interestingly, osteocytes were also localised near the blood vessels within the newly formed woven bone. On the other hand, osteocytes allocation at implant bone interface and on the implant surface were qualitatively better in the Sr substituted groups when compared to the other test groups. Furthermore, this correlates with healing enhancement and implant retention results obtained from the histomorphometry (BV/TV and Osteoclasts count). The first qualitative results of the sclerostin visualisation showed a lower expression in the Sr supplemented biomaterials compared to the Sr free ones. Conclusion. Osteoblasts, osteoclast and osteocytes are the key players to bone metabolism through production and mineralisation of ECM or resorption. The current study indicates the importance in therapeutically targeting osteocytes to regulate bone metabolism in osteoporotic/osteomalatic bone. Sr inhibits osteoclast activity which is important for implant degradation. However, in osteoporotic bone osteoclasts inhibition is crucial to enhance the healing. Our data suggest that osteocytes allocation at the bone implant interface and on the implant surface is aiding in implant degradation through osteocytes dependent resorption. Currently, discrepancies in mechanosensitivity, proliferation and fibrotic tissue formation are being investigated together with several anchorage proteins to quench further effects of osteocyte presence at the implant bone interface

Modern modular revision stems employ tapered conical (TCR) distal stems designed for immediate axial and rotational stability with subsequent osseo-integration of the stem. Modular proximal segments allow the surgeon to achieve bone contact proximally with eventual ingrowth that protects the modular junction. The independent sizing of the proximal body and distal stem allows for each portion to obtain intimate bony contact and gives the surgeon the ability precisely control the femoral head center of rotation, offset, version, leg length, and overall stability. The most important advantage of modular revision stems is versatility - the ability to manage ALL levels of femoral bone loss (present before revision or created during revision). Used routinely, this allows the surgeon to quickly gain familiarity with the techniques and instruments for preparation and implantation and subsequently master the use for all variety of situations. This also allows the operating room staff to become comfortable with the instrumentation and components. Additionally, the ability to use the stem in all bone loss situations eliminates intra-operative shuffle (changes in the surgical plan resulting in more instruments being opened), as bone loss can be significantly under-estimated pre-operatively or may change intra-operatively. Furthermore, distal fixation can be obtained simply and reliably. Paprosky 1 femoral defects can be treated with a primary-type stem for the most part. All other femoral defects can be treated with a TCR stem. Fully porous coated stems also work for many revisions but why have two different revision stem choices available when the TCR stems work for ALL defects?. The most critical advantage is the ability to separate completely the critical task of fixation from other important tasks of restoring offset, leg length, and stability. Once fixation is secured, the surgeon can concentrate on hip stability and on optimization of hip mechanics (leg length and offset). The ability to do this allows the surgeon to maximise patient functionality post-operatively. Modular tapered stems have TWO specific advantages over monolithic stems in this important surgical task. The proximal body size and length can be adjusted AFTER stem insertion if the stem goes deeper than the trial. Further, proximal/distal bone size mismatch can be accommodated. The surgeon can control the diameter of the proximal body to ensure proper bony apposition independent of distal fitting needs. If the surgeon believes that proximal bone ingrowth is important to facilitate proximal bone remodeling, modular TCR stems can more easily accomplish this. The most under-appreciated advantage is the straightforward instrumentation system that makes the operation easier for the staff and the surgeon, while enhancing the operating room efficiency and reducing cost. Also, although the implant itself may result in more cost, most modular systems allow for a decrease in inventory requirements, which make up the cost differential. One theoretical disadvantage of modular revision stems is modular junction fracture, which can happen if the junction itself is not protected by bone. Ensuring proximal bone support can minimise this problem. Once porous ingrowth occurs proximally, the risk of junction fracture is eliminated. Even NON-modular stems fracture when proximal bone support is missing. Another theoretical issue is modular junction corrosion but this not a clinical one, since both components are titanium. One can also fail to connect properly the two parts during surgery

This was a retrospective study of all AML uncemented femoral prostheses and Duraloc cups in a consecutive series of patients treated between 1990 and 1995. Patients were evaluated clinically using the Merle Score. Radiological parameters included osseo-integration, subsidence and wear. Failure was defined as removal of implants or revision. The 8 to 10-year results show a 99% survival rate. One patient was revised for femoral stem loosening following trauma. One patient with rheumatoid disease required revision for acetabular cup loosening after a few days. We conclude that the results of the uncemented AML femoral stem and Duraloc cup are excellent in the South African population

Intramedullary nailing is acknowledged as a safe and effective mode of treatment for many tibial fractures. Implant removal is frequently indicated either as an elective procedure following union or because of problems such as infection or delayed fracture union. It is therefore essential that intramedullary rod removal should be reasonably straightforward and atraumatic. We describe three cases in which bony growth into the implant has made rod removal either difficult or impossible. We include photographs of two removed implants with clearly visible areas of osseo-integration with bony growth into the cannulation through the interlocking holes as well as radiographs demonstrating the same phenomenon. The average time between insertion and removal was 16 months. In all cases an end cap had been used such that insertion of the extraction device was straightforward but for two patients nail removal was extremely difficult due to bone ingrowth and in the third patient the nail had to be left in-situ. All three implants were made of titanium and the patients were all active young males. The authors have never encountered this problem with steel rods and speculate that the osteointegrative property of titanium is the major causative factor. We suggest that unremoved intramedullary rods represent a major risk in fracture management and that close monitoring of these implants should be undertaken

Introduction. Intimate bone-implant contact is a requirement for achieving stable component fixation and osseo-integration of porous-coated implants in TKA. However, consistently attaining a press-fit and a tight-fitting femoral component can be problematic when using conventional instrumentation. We present a new robotic cutting-guide system that permits intra-operative adjustment of the femoral resections such that a specified amount of press-fit can be consistently attained. System Description: A.R.T. (Apex Robotic Technology) employs a miniature bone-mounted robotic cutting-guide and flexible software that permits the surgeon to adjust the anterior and posterior femoral resections in increments of 0.25 mm per resection, allowing a maximum of 1.5mm of total added press in the AP dimension. Methods. The accuracy of guide-positioning and bone-cutting with A.R.T. was assessed in bench testing on synthetic bones (SAWBONES®) using an optical comparator. The individual guide locations for 16 femoral cut positioning sequences (80 guide positions in total) were measured. Femoral resections were performed with A.R.T. on eight sawbones (two per fit-adjustment setting) and the anterior-posterior dimensions of the final cut surfaces were also measured. Eight sawbones were prepared using conventional instrumentation (jigs) as controls: four with a 0 mm press-fit block and four with a +0.5 mm specially manufactured press-fit block. Results. The robotic guide-positioning error in the AP dimension was −0.04 ± 0.14mm (mean ± standard deviation, SD). The standard deviation in guide positioning for the distal, anterior chamfer and posterior chamfer resections was 0.03° and 0.17mm. The average error in the AP dimension between the targeted and measured cuts was −0.14±0.13mm with A.R.T. and 0.7±0.52mm with conventional blocks (p=0.021). Conclusions. A.R.T. guide positioning precision was found to be sub-degree and sub-millimetric, allowing for significantly more accurate and repeatable bone resections than conventional instrumentation

Removal of well-fixed cement at the time of revision THA for sepsis is time consuming and risks bone stock loss, femoral perforation or fracture. We report our experience of two-stage revision for infection in a series of cases in which we have retained well-fixed femoral cement. All patients underwent two-stage revision for infection. At the first stage the prostheses and acetabular cement were removed but when the femoral cement mantle demonstrated good osseo-integration it was left in-situ. Following Girdlestone excision arthroplasty (GEA), patients received local antibiotics delivered by cement spacers, as well as systemic antibiotics. At the second stage the existing cement mantle was reamed, washed and dried and then a femoral component was cemented into the old mantle. Sixteen patients (M:F 5:11) had at least three years follow-up (mean 80 months – range 43 to 91). One patient died of an unrelated cause at 53 months. Recurrence of infection was not suspected in this case. The mean time to first stage revision was 57 months (3 to 155). The mean time between first and second stages was nine months (1 to 35). Organisms were identified in 14 (87.5%) cases (5 Staphylococcus Aureas, 4 Group B Streptococcus, 2 Coagulase negative Staphylococcus, 2 Enterococcus Faecalis, 1 Escheria Coli). At second stage, five (31.2%) acetabulae were uncemented and 11 (68.8%) were cemented. There were two complications; one patient dislocated 41 days post-operatively and a second patient required an acetabular revision at 44 days for failure of fixation. No evidence of infection was found at re-revision. One patient (1/16, 7%) has been re-revised for recurrent infection. Currently no other patients are suspected of having a recurrence of infection (93%). Retention of a well-fixed femoral cement mantle during two-stage revision for infection and subsequent cement-in-cement reconstruction appears safe with a success rate of 93%. Advantages include a shorter operating time, reduced loss of bone stock, improved component fixation and a technically easier second stage procedure

Bone related adverse events including failure of implant osseo-integration, periprosthetic fracture, femoral neck narrowing, and unexplained pain occur more frequently following metal-on-metal hip resurfacing (MoMHR) versus total hip arthroplasty (THA). The exact mechanism for the adverse effects is still unclear and may be due to the direct effect on bone cells of metal ions released from the prostheses. The aim of the present study was to determine the effect of clinically relevant combinations of metal ions on osteoblast cell survival and function. To assess cell proliferation and alkaline phosphatase (ALP) activity of osteoblasts, human osteoblast cells (SaOS-2), were cultured in 96-well plates for 24-hours and then treated with metal ions. Cell proliferation was measured at day 3 and day 7 using MTS assay, whilst ALP activity was assessed at day 3 by measuring pNPP substrate hydrolysis by the cell lysate. Mineralisation ability of the cells was assessed in 24-well plates cultured until day 21 and staining the calcium deposits using Alizarin red. All cultures were treated with the IC50 concentration of Co(II) (135μM) and an equivalent Cr(III) concentration (1Co(II):1Cr(III)). After 3 days, Co(II) at an IC50 concentration decreased osteoblast proliferation as expected, but no further decrease in proliferation was observed with the 1Co(II):1Cr(III) combination treatment. However, after 7 days, a further significant decrease (P<0.05) in proliferation was observed with the combination treatment compared to Co(II) IC50. A similar significant decrease (P<0.01) was observed for ALP activity at day 3 with 1Co(II):1Cr(III) compared to Co(II) alone. For mineralization, a significant reduction (P<0.0001) was observed for Co(II) IC50 concentration, however no further reduction was seen with the 1Co(II):1Cr(III) combination treatment. The observed decrease in cell proliferation and ALP activity with combination treatments suggest an additive detrimental effect compared to single ions alone. The mineralisation ability did not show any additive effect due to cell toxicity of chronic exposure to IC50 concentrations calculated from 3 day proliferation cultures. The results suggest that presence of both cobalt and chromium ions in the periprosthetic environment have more severe detrimental effect on osteoblasts than single ions alone and extend our understanding of the periprosthetic bone health

Introduction: Tantalum Monoblock Acetabular cup was designed to reduce backside wear and stimulate osseo-integration of cup with bone. The cup has peripheral fit to improve the initial stability and further stability and longevity depends on the osseointegration of cup with acetabulum. The revision cup was intended to give added stability with screws in case of defective rim or large acetabulum. The aim of this study is to assess the radiological outcome following tantalum monoblock revision cup in total hip replacement. Methods: Between 1999 and 2000, 32 Tantalum mono-block revision acetabular cups was used in 31 patients. Standard hip radiographs were performed during post op, at three months, six months and then annually. X rays were assessed for loosening in De Lee and Charnley zones and for migration of cup. Results: At a minimum follow-up of 2 years (range 2 to 5 years), 31 hips in 30 patients were assessed. The average age of the patient was 62.4 years (39–78 years). Three Brookers type 1 and one type 2 heterotrophic ossification was seen. There was a gap of 2–5mm in Zone 1(6 patients), 1–5mm in Zone 2 (8 Patients) and 5mm in Zone 3 of one patient. At final follow up, all the gaps were filled, except for one, where 5mm gap was persistent. There was no migration of cup or problems with screws. All the patients were satisfied with the operation. Conclusion: Short term radiological result following uncemented revision tantalum monoblock acetabular cup in total hip replacement is highly encouraging. However, similar results from other centres and long term follow up studies are necessary to confirm the efficacy of the revision cups

Introduction: Trabecular Metal (Tantalum) has been successfully used in Neurosurgery for many years. Acetabular components have only been available in the UK since 2004. The metal’s properties of porosity and a high friction coefficient are attractive, particularly in complex primary and revision hip arthroplasty when surgical challenges include abnormal, deficient or limited bone. Methods: Two year results of 110 consecutive acetabular reconstructions are presented. The age range was between 27 and 95 years with a predominance of females. The indication in 75 primary hip replacements included, Destructive Osteoarthritis, Dysplasia, Rheumatoid Arthritis, Paget’s and AVN. 35 revisions were performed either two-component or single acetabular exchanges. Clinical results have been obtained using the Merle d’Aubigne score and bone deficiencies were classified according to the AAOS system. Results: There have been no failures and radiologically, serial X-rays demonstrate osseo-integration at an early stage. We have had no cases of deep infection but there have been 3 femoral peri-prosthetic fractures, (1 late) and 2 dislocations. All patients have been allowed early weight bearing and those patients with over 12 months follow up have an improved Merle d’Aubigne score. Discussion: The biomechanical properties of Trabecular metal and a modular design permit a press fit technique supplemented by dome screws combined with the possibility of using varying sizes of liner to minimise dislocation or to retain well fixed femoral stems in revision surgery. The ease of use of the implant has now led to us largely abandoning other reconstructive techniques such as impaction allo-grafting or cages in revision or complex primary hip surgery. We consider Trabecular metal to be a major advance in acetabular reconstruction on the basis of our initial experience

Purpose: Removal of all foreign material is the normal practice at the time of revision arthroplasty for sepsis. However, removal of well-fixed bone cement is time consuming, can result in significant bone stock loss and increases the risk of femoral shaft perforation or fracture. We have performed two-stage revision for infection in a series of cases in which we have left oseeointegrated femoral cement at the first stage and we present the results of this technique. Method: All patients underwent two-stage revision for infection. At the first stage the prostheses and acetabu-lar cement were removed but when the femoral cement mantle demonstrated good osseo-integration it was left in-situ. Following Girdlestone excision arthroplasty (GEA), patients received local antibiotics delivered by cement spacers, as well as systemic antibiotics. At the second stage the existing cement mantle was reamed, washed and dried and then a femoral component was cemented into the old mantle. Results: Sixteen patients (M:F 5:11) had at least three years follow up (mean 80 months, range 43 to 91). One patient died of an unrelated cause at 53 months. Recurrence of infection was not suspected in this case. The mean time to first stage revision was 57 months (3 to 155). The mean time between first and second stages was 9 months (1 to 35). Organisms were identified in 14 (87.5%) cases (5 Staphylococcus Aureas, 4 Group B Streptococcus, 2 Coagulase negative Staphylococcus, 2 Enterococcus Faecalis, 1 Escheria Coli). At second stage, five (31.2%) acetabuli were uncemented and 11 (68.8%) were cemented. There were two complications; one patient dislocated 41 days post-operatively and a second patient required an acetabular revision at 44 days for sudden loss of fixation. No evidence of infection was found at re-revision. One patient has been revised for recurrent infection. Currently no patients are suspected of having a recurrence of infection. Conclusion: Retention of a well-fixed femoral cement mantle during two-stage revision for infection and subsequent in-cement reconstruction is safe with a cure rate of 93%. Advantages include a shorter operating time, reduced loss of bone stock, improved component fixation and a technically easier second stage procedure

Aims: The holding power of new designed implants, need to be improved by osseointegration, in particular in osteoporotic bone. The osseo-integration depends on the interface mechanical conditions during fracture healing or fusion leading either to bony incorporation or to micro-movement and encapsulation. The aim of the current study was to evaluate the load sharing conditions after the fusion process between implant and bone with respect to the fusion status of the stabilized segment. Methods: The hollow cylinder based implant was used to stabilize a corpectomy of L4 in 17 sheep (9 osteoporotic and 8 control). After a survival time of 4 month the spine specimens were tested in a six-degree-of-freedom (6DOF) device in the three principal directions (flex/ex, lat. bending, torsion). Hysteresis curves were recorded before and after removal of the stabilizing longitudinal bar. The changes in ROM and stiffness in the different planes were compared statistically (α < 0.05). The results were validated histologically. Results: The increase in range of motion in all planes was significantly higher after implant removal in animals that were classified as non-fused spines (+35±15% in non-fused vs. +12±8% in fused spines). At the same time stiffness decreased significantly more (stiffness ex/flex −31±14% in non-fused vs −7±7% in fused spines) without differnces between normal and osteoporotic spines. Histology revealed 3 capsules in the fused spines. Conclusions: If fusion takes place in the presence of a relatively stiff implant the load flow through the implant is interrupted by connective tissue on one of the implant/bone interfaces. The changes in ROM and stiffness indicate the remaining contribution of the implant to the load sharing of the implant/ bone complex in case of non-fusion and are highly sensitive therefore to predict micromovement

Introduction: Removal of all foreign material is the normal practice at the time of revision arthroplasty for sepsis. However, removal of well fixed bone cement is time consuming, can result in significant bone stock loss and increases the risk of femoral shaft perforation or fracture. We report our results of 2 stage revision hip arthroplasty with retention of a well fixed femoral cement mantle. Methods: If the femoral cement mantle demonstrated good osseo-integration at first stage it was left in-situ. Following Girdlestone excision arthroplasty (GEA), patients received local and systemic antibiotics and underwent reconstruction at a second stage. At the second stage the femoral component was cemented into the old mantle. Results: 16 patients (M:F 5:11) had at least 3 years follow up (mean 80 months, range 43 to 91). 1 patient died of an unrelated cause at 53 months. Recurrence of infection was not suspected in this case. The mean time to first stage revision was 57 months (3 to 155). The mean time between first and second stages was 9 months (1 to 35). Organisms were identified in 14 (87.5%) cases (5 Staphylococcus Aureus, 4 Group-B Streptococcus, 2 Coagulase negative Staphylococcus, 2 Enterococcus Faecalis, 1 Escheria Coli). At second stage 5 (31.2%) acetabula were uncemented and 11 (68.8%) were cemented. There were 2 complications, 1 patient dislocated 41 days post-operatively and a second patient required an acetabular revision at 44 days for sudden loss of fixation. No evidence of infection was found at re-revision. Currently no patients are suspected of having a recurrence of infection. Discussion: In-cement revision of the femoral component following GEA for sepsis is not associated with a higher rate of recurrence of infection. Advantages include a shorter operating time, reduced loss of bone stock, improved component fixation and a technically easier second stage procedure