Introduction. Femoral neck impingement occurs clinically in total hip replacements (THR) when the acetabular liner articulates against the neck of a femoral stem prosthesis. This may occur in vivo due to factors such as prostheses design, patient anatomical variation, and/or surgical malpositioning, and may be linked to joint instability, unexplained pain, and dislocation. The Standard Test Method for Impingement of Acetabular Prostheses, ASTM F2582 −14, may be used to evaluate acetabular component fatigue and deformation under repeated impingement conditions. It is worth noting that while femoral neck impingement is a clinical observation, relative motions and loading conditions used in ASTM F2582-14 do not replicate in vivo mechanisms. As written, ASTM F2582-14 covers failure mechanism assessment for acetabular liners of multiple designs, materials, and sizes. This study investigates differences observed in the implied and executed kinematics described in ASTM F2582-14 using a Prosim electromechanical hip simulator (Simulation Solutions, Stockport, Greater Manchester) and an AMTI hydraulic 12-station hip simulator (AMTI, Watertown, MA). Method. Neck impingement testing per ASTM F2582-14 was carried out on four groups of artificially aged acetabular liners (per ASTM F2003-15) made from GUR 1020 UHMWPE which was re-melted and cross-linked at 7.5 Mrad. Group A (n=3) and B (n=3) consisted of 28mm diameter femoral heads articulating on 28mm ID × 44mm OD acetabular liners. Group C (n=3) and D (n=3) consisted of 40mm diameter femoral heads articulating on lipped 40mm ID × 56mm OD 10° face changing acetabular liners. All acetabular liners were tested in production equivalent shell-fixtures mounted at 0° initial inclination angle. Femoral stems were potted in resin to fit respective simulator test fixtures. Testing was conducted in bovine serum diluted to 18mg/mL protein content supplemented with sodium azide and EDTA. Groups A and C were tested on a Prosim; Groups B and D were tested on an AMTI. Physical examination and coordination measurement machine (CMM) analyses were conducted on all liners pre-test and at 0.2 million cycle intervals to monitor possible failure mechanisms. Testing was conducted for 1.0 million cycles or until failure. An Abaqus/Explicit model was created to investigate relative motions and contact areas resulting from initial impingement kinematics for each test group. Results. Effects of kinematic differences in the execution of ASTM F2582-14 were observed in the four groups based on simulator type (Figure 1) and liner design. The Abaqus/Explicit FEA model revealed notable differences in relative motions and contact points (Figure 2) between specimen components i.e. acetabular liner, femoral head, and femoral stem throughout range of motion. Acetabular liner angular change within shell-fixtures, rim deformation, crack propagation, and metal-on-metal contact between acetabular shell-fixtures and femoral stems were observed as potential failure mechanisms (Figure 3) throughout testing. These mechanisms varied in severity by group due to differing contact stresses and simulator constraints. Significance. Investigating failure mechanisms caused by altered kinematics of in-vitro neck impingement testing, due to influences of simulator type and acetabular liner design, may aid understanding of failure mechanisms involved when assessing complaints/retrievals and influence future prosthetic designs. For any figures or tables, please contact the authors directly

1. Currently available total replacement hip and knee prostheses were tested in a machine enabling flexion-extension movements to be applied whilst the prostheses were surrounded with Ringer's solution or other liquid and loaded within the physiological range. 2. Prostheses of which both components were made in cobalt-chromium-molybdenum alloy produced visible quantities of alloy particles, whose sizes ranged down to about 0·1 microns, and cobalt and molybdenum ions in solution. 3. No metallic or plastic particles were detected during tests on a hip prosthesis made of stainless steel and high density polyethylene. 4. The frictional moments in cobalt-chromium-molybdenum hip prostheses were higher than in stainless steel-polyethylene hip prostheses, by a factor of at least 2 to 1. 5. It is accepted that the conditions of these tests were probably more severe than in life, but the difference is held to be one of degree and not one of kind. 6. The particulate alloy debris, when injected in massive doses into the muscles of rats, gave an incidence of malignant tumours which was comparable to that already established for pure cobalt powder, whereas particles of several other metals, tested in the same way, gave no tumours. 7. It is argued that the particles which are known to be produced in at least some patients using cobalt-chromium-molybdenum total replacement joint prostheses constitute a risk of tumour formation which is certainly small, possibly negligible, but not accurately calculable at present. 8. The results of these tests, particularly the differences in frictional moment and in the production of particulate debris, suggest a preference for high density polyethylene as one component of a total joint replacement prosthesis

Summary. Osseointegrated Amputation Prostheses can be functionalised by both biological augmentation and structural augmentation. These augmentation techniques may aid the formation of a stable skin-implant interface. Introduction. Current clinical options are limited in restoring function to amputees, and are associated with contact dermatitis and infection at the stump-socket interface. Osseointegrated Amputation Prosthesis attempts to solve issues at the stump-socket interface by directly transferring axial load to the prosthesis, via a skin-penetrating abutment. However, development is needed to achieve a seal at the skin-implant interface to limit infection. Fibronectin, an Extracellular Matrix protein, binds to integrins during wound healing, with the RGD tripeptide being part of the recognition sequence for its integrin binding domain. In vitro work has found silanization of RGD to polished titanium discs up regulates fibroblast attachment compared to polished control. Electron Beam Melting can produce porous titanium alloy implants, which may encourage tissue attachment. This study aims to test whether a combination of biological RGD coatings and porous metal manufacturing techniques can encourage the formation of a seal at the skin-implant interface. Materials and Methods. We developed four different augmented transcutaneous devices: Porous, Porous RGD coated, drilled and drilled RGD coated. These were implanted in tibial transcutaneous ovine model, n=6, for a period of 6 months. Following explantation we performed hard grade resin histology to assess soft tissue attachment at the transcutaneous interface. Results. Histological analysis revealed no statistical difference in epithelial downgrowth and epidermal attachment values between the four augmented devices. There were significant increases (p<0.05) in the number of blood vessels and the number of cells in the Porous RGD devices compared with both drilled implant devices. Both Porous and Porous RGD implant groups observed significant increase (p<0.05) in soft tissue infiltration compared with both Drilled implant devices. Discussion. The use of porous structures and RGD coatings increases tissue ingrowth and revascularisation in ITAP devices despite having no effect on epithelial downgrowth and epidermal attachment in a long-term ovine model. There were no detrimental effects in the transcutaneous interface formation observed. These augmentation techniques may prove beneficial in preclinical and clinical developments of transcutaneous osseointegrated devices

Purpose of the study: Revision total knee arthroplasty with major destruction of bone and ligament tissue raises the problem of choosing between a complex reconstruction with a semi-constrained prosthesis or a much more simple procedure using a hinged prosthesis which transmits all of the stress to the bone anchors. The choice is basically one of longevity of the bony fixation of these constrained prostheses (and the deterioration of the articulated pieces). The present work reports the long-term outcome observed with constrained hinged prosthesis with a cemented press-fit stem implanted for bone tumors where the stress is even greater than for revisions. Material and methods: The series included 32 prostheses implanted in young active subjects (mean age 33 years). A hinged, non-rotating Guepar II revision prosthesis was implanted. The part of the implant corresponding to the reconstruction after tumor resection was custom-made but the part implanted in «healthy» bone (for example the tibial piece in a patient with a femoral tumor) was the same as used for revisions prostheses inserted after loosening. On the healthy side, press-fit quadrangular stems were used, generally adapted to the endosteum by reaming. The prosthesis was fixed by simple mechanical adjustment before cementing, using the French paradox system (JBJS 2003). Before 1993, a metal-polyethylene bearing was used and after 1993 a metal-on-metal bearing without inserts. Results: Among the 32 patients with a malignant tumor, 19 survived, seven with 2–10 years follow-up and 12 with 10–21 years follow-up. For the overall series, there was only one case of osteolysis on a tibial tumor which was revised at 12 years. There was one infection (hematogeneous) at 21 years (antibiotic cement). Prostheses with polyethylene inserts produced laxities or synovitis with 50% requiring synovectomy and insert replacement. There were no cases of synovitis for the metal-on-metal bearings. Two stems (inserted in adolescents) were too thin and had to be changed because of fracture without loosening. Discussion: Prosthesis survival was 88% at ten years (1 osteolysis, 2 fractures on tumor), even for the constrained prostheses, even for young and active subjects. Conclusion: The very good longevity of cemented pressfit stems (and the absence of synovitis and osteolysis with metal-on-metal bearings, and the low rate of infection) should be kept in mind as a possible alternative to very complex and possibly less predictable procedures in the presence of certain very severe loosenings with bone and ligament destruction

To try and aid the formation of a soft tissue seal to promote dermal and epidermal attachment to Intraosseous Transcutaneous Amputation Prostheses we compared the effect of titanium surfaces functionalised with fibronectin (fn) or YRGD peptide sequences on human dermal cell (HDF) attachment. We hypothesise that YRGD and fn coatings will significantly increase HDF attachment to titanium alloy substrates. Titanium alloy 10mm discs were polished and acted as control substrates, functionalised surfaces had YRGD or fn adsorbed or silanised onto the polished surface. HDFs were seeded at 10,000/disc and cultured for 1, 4, 24 and 96 hours, fixed and fluorescent immnolocalisation for vinculin was performed. Individual vinculin markers were counted and density calculated as a measure of cell attachment. All assays were performed in triplicate and data were analysed in SPSS 19.0 and results were considered significant at the 0.05 level. Results showed an up-regulation of Focal adhesion density (FA) against controls at all time-points (excluding ad-fn at 4 hours, p=0.057), p values < 0.05, the use of functionalised titanium surfaces may lead to long-term clinical success of ITAP. We have shown a significant positive effect on cell attachment when a synthetic peptide sequence is used. Using synthetic peptide sequence may also be more beneficial from a regulatory stand-point compared with using isolated proteins

Infection in orthopedics is a challenge, since it has high incidence (rates can be up to 15-20%, also depending on the surgical procedure and on comorbidities), interferes with osseointegration and brings severe complications to the patients and high societal burden. In particular, infection rates are high in oncologic surgery, when biomedical devices are used to fill bone gaps created to remove tumors. To increase osseointegration, calcium phosphates coatings are used. To prevent infection, metal- and mainly silver-based coatings are the most diffused option. However, traditional techniques present some drawbacks, including scarce adhesion to the substrate, detachments, and/or poor control over metal ions release, all leading to cytotoxicity and/or interfering with osteointegration. Since important cross-relations exist among infection, osseointegration and tumors, solutions capable of addressing all would be a breakthrough innovation in the field and could improve clinical practice.

Here, for the first time, we propose the use antimicrobial silver-based nanostructured thin films to simultaneously discourage infection and bone metastases. Coatings are obtained by Ionized Jet Deposition, a plasma-assisted technique that permits to manufacture films of submicrometric thickness having a nanostructured surface texture. These characteristics, in turn, allow tuning silver release and avoid delamination, thus preventing toxicity. In addition, to mitigate interference with osseointegration, here silver composites with bone apatite are explored. Indeed, capability of bone apatite coatings to promote osseointegration had been previously demonstrated in vitro and in vivo. Here, antibacterial efficacy and biocompatibility of silver-based films are tested in vitro and in vivo. Finally, for the first time, a proof-of-concept of antitumor efficacy of the silver-based films is shown in vitro.

Coatings are obtained by silver and silver-bone apatite composite targets. Both standard and custom-made (porous) vertebral titanium alloy prostheses are used as substrates.

Films composition and morphology depending on the deposition parameters are investigated and optimized. Antibacterial efficacy of silver films is tested in vitro against gram+ and gram- species (E. coli, P. aeruginosa, S. aureus, E. faecalis), to determine the optimal coatings characteristics, by assessing reduction of bacterial viability, adhesion to substrate and biofilm formation. Biocompatibility is tested in vitro on fibroblasts and MSCs and, in vivo on rat models. Efficacy is also tested in an in vivo rabbit model, using a multidrug resistant strain of S. aureus (MRSA, S. aureus USA 300). Absence of nanotoxicity is assessed in vivo by measuring possible presence of Ag in the blood or in target organs (ICP-MS). Then, possible antitumor effect of the films is preliminary assessed in vitro using MDA-MB-231 cells, live/dead assay and scanning electron microscopy (FEG-SEM). Statistical analysis is performed and data are reported as Mean ± standard Deviation at a significance level of p <0.05. Silver and silver-bone apatite films show high efficacy in vitro against all the tested strains (complete inhibition of planktonic growth, reduction of biofilm formation > 50%), without causing cytotoxicity. Biocompatibility is also confirmed in vivo.

In vivo, Ag and Ag-bone apatite films can inhibit the MRSA strain (>99% and >86% reduction against ctr, respectively). Residual antibacterial activity is retained after explant (at 1 month). These studies indicate that IJD films are highly tunable and can be a promising route to overcome the main challenges in orthopedic prostheses.

Background/Aims. The development of extendable prostheses has permitted limb salvage surgery in paediatric patients with bone tumours in proximity to the physis. Prostheses are extended to offset limb length discrepancy as the child grows. Aseptic loosening (AL) is a recognised complication. The implant stem must fit the narrow paediatric medullary canal and remain fixed while withstanding growth and increasing physical demands. Novel designs incorporate a hydroxyapatite (HA) coated collar that manufacturers claim improves bony ongrowth and stability, providing even stress distribution in stem and shoulder regions and providing a bone-implant seal, resulting in decreased AL and prolonged survival. This study aims to assess whether there is a relationship between bony ongrowth onto a HA collar and AL. Hypothesis: Bone ongrowth onto the HA collar of extendable prostheses is associated with more stable fixation and less AL despite patient growth. Methods. Retrospective review of 51 primary partial femoral extendable prostheses implanted over 12 years from 1994–2006 (followed up to death at a mean of 2.5±2.2 years or last clinical encounter at a mean of 8.6 years) and 24 subsequent revisions, to ascertain failure rate and mode, together with a cohort study reviewing bony ongrowth onto the HA coated collar in 10 loose and 13 well fixed partial femoral, humeral and tibial implants. Patient growth was measured as a change in bone:implant-width ratio. Results. 21 (41.2%) primary femoral implants failed at a mean 42.8 months, 5 through AL. 1 secondary implant was revised for AL. 2 implants displayed evidence of progressive AL but had not failed at last follow-up. 5 of 11 tibial component revisions in distal femoral replacement were due to AL. 1 major complication occurred after revision surgery for AL in a primary implant: deep infection requiring 2 stage revision. Bony collar ongrowth was significantly higher in all 4 quadrants (anterior, posterior, medial and lateral) in the well-fixed as opposed to loose group, demonstrating a strong negative relationship in each quadrant between bony ongrowth and AL (p0.001) in the presence of patient growth as shown by increased bone:implant width ratio. In both groups, collar ongrowth was greatest in the posterior quadrant. Summary and Conclusions: AL has been confirmed as a common cause of failure in massive extendable endoprostheses. Revision surgery is difficult and may cause serious complications. For the first time, a significant relationship between a well fixed implant stem and bony ongrowth onto a HA coated collar in the context of massive implants used in tumour surgery has been demonstrated. This newly-proven relationship may result in longer-term implant survival and thus a reduced need for revision surgery. It is hoped that this study will provide the basis for further study of this relationship

Purpose of the study: Generally, hip prosthesis implantation for congenital hip dysplasia is a routine procedure. Material and methods: We compared preliminary results between two surgical techniques. On one hand, hip prostheses were implanted via trochanterotomy with femoral shortening osteotomy for cemented insertion and trochanteroplasty. On the other, access was achieved via a triple infratrochanteric osteotomy for shortening, correction of valgum and derotation followed by implantation of a press-fit prosthesis without osteosynthesis. Results:. Between 1993 and 2001, 61 patients underwent surgery for Crowe III or Eftekhar grade C hips (n=45) and Crowe IV or Eftekhar grade D hips (n=16). Mean patient age was 42 years. Prostheses inserted via the trans-trochanteric approach with femoral shortening osteotomy and cementing developed complications related to the trochanteroplasty: nonunion of the greater trochanter (n=6), functional impairment (n=2), infection after bursitis on suture and secondary necrosis (n=1). Because of these complications we adopted the triple femoral osteotomy technique for shortening, derotation and press-fit femoral implants. Between 2001 and 2005, eight Eftekhar D hips were treated with this technique. Locked non-cemented femoral prostheses were inserted. Pre- and postoperative clinical assessment was based on the Postel-Merle-d’Aubigné score. For the cup, the technique remained unchanged, with cemented implants. The lengthening obtaine varied from 3.5 to 5.5 cm with no cases of sciatic palsy. There has been no case of prosthesis dislocation. Conclusion: These preliminary results concern non-cemented femoral prosthesis with insufficient follow-up. We nevertheless have found this an attractive technique free of femoral complications

The anatomy of the femur shows a high inter-patient variability, making it challenging to design standard prosthetic devices that perfectly adapt to the geometry of each individual. Over the past decade, Statistical Shape Models (SSMs) have been largely used as a tool to represent an average shape of many three-dimensional objects, as well as their variation in shape. However, no studies of the morphology of the residual femoral canal in patients who have undergone an amputation have been performed. The aim of this study was therefore to evaluate the main modes of variation in the shape of the canal, therefore simulating and analysing different levels of osteotomy.

To assess the variability of the femoral canal, 72 CT-scans of the lower limb were selected. A segmentation was performed to isolate the region of interest (ROI), ranging from the lesser tip of the trochanter to the 75% of the length of the femur. The canals were then sized to scale, aligned, and 16 osteotomy levels were simulated, starting from a section corresponding to 25% of the ROI and up to the distal section. For each level, the main modes of variations of the femoral canal were identified through Principal Component Analysis (PCA), thus generating the mean geometry and the extreme shapes (±2 stdev) of the principal modes of variation.

The shape of the canals obtained from these geometries was reconstructed every 10 mm, best- fitted with an ellipse and the following parameters were evaluated: i) ellipticity, by looking at the difference between axismax and axismin; ii) curvature of the canal, calculating the arc of circumference passing through the shapes’ centroids; iii) conicity, by looking at the maximum/minimum diameter; iv) mean diameter. To understand the association between the main modes and the shape variance, these parameters were compared, for each level of osteotomy, between the two extreme geometries of the main modes of variation.

Results from PCA pointed out that the first three PCs explained more than the 87% of the total variance, for each level of simulated osteotomy. By analysing the extreme geometries for a distal osteotomy (e.g. 80% of the length of the canal), the first PC was associated to a combination of ROC (var%=41%), conicity (var%=28%) and ellipticity (var%=7%). PC2 was still associated with the ROC (var%=16%), while PC3 turned out to be associated with the diameter (var%=38%).

Through the SSM presented in this study, a quantitatively evaluation of the deformation of the intramedullary canal has been made possible. By analysing the extreme geometries obtained from the first three modes of variance, it is clear that the first three PCs accounted for the variations in terms of curvature, conicity, ellipticity and diameter of the femoral canal with a different weight, depending on the level of osteotomy. Through this work, it was also possible to parametrize these variations according to the level of excision. The results given for the segment corresponding to the 80% of the length of the canal showed that, at that specified level, the ROC, conicity and ellipticity were the anatomical parameters with the highest range of variability, followed by the variation in terms of diameter. Therefore, the analysis carried out can provide information about the relevance of these parameters depending on the level of osteotomy suffered by the amputee. In this way, optimal strategies for the design and/or customization of osteo-integrated stems can be offered depending on the patient's residual limb.

Aims

Arthroplasty surgery of the knee and hip is performed in two to three million patients annually. Periprosthetic joint infections occur in 4% of these patients. Debridement, antibiotics, and implant retention (DAIR) surgery aimed at cleaning the infected prosthesis often fails, subsequently requiring invasive revision of the complete prosthetic reconstruction. Infection-specific imaging may help to guide DAIR. In this study, we evaluated a bacteria-specific hybrid tracer (^99mTc-UBI_29-41-Cy5) and its ability to visualize the bacterial load on femoral implants using clinical-grade image guidance methods.

Purpose: The three dimensional position of the tuberosity and the tension of the rotator cuff influence the structural changes of the rotator cuff and their influence on clinical results of reversed trauma prostheses. We propose this technique with it of a biological support, the fractured humeral head, adequately modeled, in order to give again the just tension to the cuff. Method: from February 2007 and February 2009 we treated 29 patients with a reversed trauma prostehes, in 7 cases we have practiced the bony necktie, for giving a support to the correct reconstruction of the tuberosity. The patients have an average of 71,5 years and was evaluated with Constant score and radiographic study with mean follow-up of 18,6 months. Results: Improvement of postoperative Constant score and radiographic good results were correlated with satisfactory subjective results. However, these results will have to be confirmed with more cases and later revision. Conclusion: Tuberosity position and healing is critical for clinical and radiographic outcome in shoulder arthroplasty in trauma. In particular the rate resorption of the tuberosity in Reverse Trauma Prostheses still is elevated. we propose a new surgical technical in order to give again the just position to the tuberosity fractured and therefore to give tension to the rotator cuff

Summary. The required torque leading to an abrasion of the passive layer in the stem-head interface positively correlates to the assembly force. In order to limit the risk of fretting and corrosion a strong hammer blow seems to be necessary. Introduction. Modular hip prostheses are commonly used in orthopaedic surgery and offer a taper connection between stem and ball head. Taper connections are exposed to high bending loads and bear the risk of fretting and corrosion, as observed in clinical applications. This is particularly a problem for large diameter metal bearings as the negative effects may be enhanced due to the higher moments within the taper connection. Currently, it is not known how much torque is required to initiate a removal of the passive layer, which might lead to corrosion over a longer period and limits the lifetime of prostheses. Therefore, the purpose of this study was to identify the amount of torque required to start an abrasion of the passive layer within the interface dependent on the assembly force and the axial load. Materials and Methods. Titanium hip stems (Furlong H-AC, JRI, UK) and cobalt-chromium heads (⊘ 28mm, size L, JRI, UK) were assembled using a drop rig with peak forces of 4.5 kN (F. P,1. , n = 4) or 6.0 kN (F. P,2. , n = 4). The prostheses were inverted and then mounted with the head rigidly fixed to the base of a materials testing machine using a non-conducting (nylon) jig while submerged in Ringer's solution. The stems were attached to the machine actuator via non-conductive plates. An axial load (F. A,1. = 1 kN, F. A,2. = 3 kN, n = 4 each) was applied to the stems along the taper axis. After a period of equilibration a torque, increasing from 0 up to 15Nm, was manually applied. The galvanic potential at the taper interface was continuously recorded using a titanium electrode. The torque required to cause a drop in the potential of 5% was identified. For statistical analyses non-parametric tests were performed (α = 0.05). Results. Four different phases of the potential could be clearly differentiated during testing: equilibrium, removal of the passive layer leading to a drop of the potential, repassivation and then a second equilibrium. Prostheses assembled with a force of 6 kN required a significantly higher torque to start a removal of the passive layer compared to those with 4.5 kN (7.2 ± 0.5 Nm vs. 3.9 ± 1.0 Nm for F. A,1. , p = 0.029). In contrast, no influence of the axial load on the fretting behaviour of the prostheses could be found (8.0 ± 1.6 Nm for F. P,2. , p = 0.486). Discussion. Changes in the galvanic potential were observed at low torque levels for a small head diameter. With increasing head diameter the tangential force leading to a removal of the passive layer in the stem-head interface decrease resulting in a higher risk for corrosion. Component assembly with a high force reduces the risk of fretting and corrosion in the taper interface; however, it is feasible that the determined torque levels can still be reached, particularly in situations of large weight and high activity of the patient or malpositioning of the prosthesis in the body

Introduction

“Bioexpandable” prostheses after resection of malignant bone tumors in children to lengthen the bone using the method of callus distraction may offer new perspectives and better long-term results.

Modular dual mobility (DM) articulations are increasingly utilized during total hip arthroplasty (THA). However, concerns remain regarding the metal liner modularity. This study aims to correlate metal artifact reduction sequence (MARS) magnetic resonance imaging (MRI) abnormalities with serum metal ion levels in patients with DM articulations.

All patients with an asymptomatic, primary THA and DM articulation with >2-year follow-up underwent MARS-MRI of the operative hip. Each patient had serum cobalt, chromium, and titanium levels drawn. Patient satisfaction, Oxford Hip Score, and Forgotten Joint Score-12 (FJS-12) were collected. Each MARS-MRI was independently reviewed by fellowship-trained musculoskeletal radiologists blinded to serum ion levels.

Forty-five patients (50 hips) with a modular DM articulation were included with average follow-up of 3.7±1.2 years. Two patients (4.4%) had abnormal periprosthetic fluid collections on MARS-MRI with cobalt levels >3.0 μg/L. Four patients (8.9%) had MARS-MRI findings consistent with greater trochanteric bursitis, all with cobalt levels < 1.0 μg/L. A seventh patient had a periprosthetic fluid collection with normal ion levels. Of the 38 patients without MARS-MRI abnormalities, 37 (97.4%) had cobalt levels <1.0 μg/L, while one (2.6%) had a cobalt level of 1.4 μg/L. One patient (2.2%) had a chromium level >3.0 μg/L and a periprosthetic fluid collection. Of the 41 patients with titanium levels, five (12.2%) had titanium levels >5.0 μg/L without associated MARS-MRI abnormalities.

Periprosthetic fluid collections associated with elevated serum cobalt levels in patients with asymptomatic dual mobility articulations occur infrequently (4.4%), but further assessment of these patients is necessary.

Level of Evidence: Level IV

We aimed to obtain anthropometric data on Korean knees and to compare these with data on commonly available total knee arthroplasties (TKAs). The dimensions of the femora and tibiae of 1168 knees were measured intra-operatively. The femoral components were found to show a tendency toward mediolateral (ML) under-coverage in small femurs and ML overhang in the large femurs. The ML under-coverage was most prominent for the small prostheses. The ML/anteroposterior (ML/AP) ratio of Korean tibiae was greater than that of tibial components.

This study shows that, for different reasons, current TKAs do not provide a reasonable fit for small or large Korean knees, and that the ‘gender-specific’ and ‘stature-specific’ components help for large Korean femurs but offer less satisfactory fits for small femurs. Specific modifications of prostheses are needed for Asian knees.

Abstract

Dual mobility hip arthroplasty utilizes a freely rotating polyethylene liner to protect against dislocation. As liner motion has not been confirmed in vivo, we investigated the liner kinematics in vivo using dynamic radiostereometry.

16 patients with Anatomical Dual Mobility acetabular components were included. Markers were implanted in the liners using a drill guide. Static RSA recordings and patient reported outcome measures were obtained at post-op and 1-year follow-up. Dynamic RSA recordings were obtained at 1-year follow-up during a passive hip movement: abduction/external rotation, adduction/internal rotation (modified FABER-FADIR), to end-range and at 45° hip flexion. Liner- and neck movements were described as anteversion, inclination and rotation.

Liner movement during modified FABER-FADIR was detected in 12 of 16 patients. Median (range) absolute liner movements were: anteversion 10° (5–20), inclination 6° (2–12), and rotation 11° (5–48) relative to the cup. Median absolute changes in the resulting liner/neck angle (small articulation) was 28° (12–46) and liner/cup angle (larger articulation) was 6° (4–21). Static RSA showed changes in median (range) liner anteversion from 7° (-12–23) postoperatively to 10° (-3–16) at 1-year follow-up and inclination from 42 (35–66) postoperatively to 59 (46–80) at 1-year follow-up. Liner/neck contact was associated with high initial liner anteversion (p=0.01).

The polyethylene liner moves over time. One year after surgery the liner can move with or without liner/neck contact. The majority of movement is in the smaller articulation between head and liner.

The objective of this study was to evaluate the short term clinical and radiological results of a new short stem hip implant. In 29 consecutive patients suffering from osteoarthritis with 33 affected hip joints, the clinical and radiological results of 33 cementless hip arthroplasties using a cementless implanted short stem prosthesis type Aida and a cementless cup type Ecofit were evaluated prospectively between October 2009 and June 2015 in two hospitals. The median age of patients at time of surgery was 55 years (range, 30–71 years), 23 male and 10 female patients were included in the study. The median clinical follow up was 24 months (range, 1.5–51 months), and the median radiological follow up was 12 months (range, 1–51 months). Two patients were lost to follow up and two patients had only one immediate postoperative x- ray. The Harris Hip Score improved from a median preoperative value of 53 to a median postoperative value of 93 at follow up. Radiological analysis showed that 19 stems (58%) showed stable bony ingrowth, five cases (15%) showed stable fibrous ingrowth. Four cases need further follow up for proper evaluation of stem fixation. The short term survival of this new short stem is very promising, and achieving the goals of standard hip arthroplasty.

Objective

We explanted NeuFlex metacarpophalangeal (MP) joint prostheses to identify common features, such as position of fracture, and thus better understand the reasons for implant failure.

Joint replacement is a life-enhancing, cost-effective surgical intervention widely used to treat disabling joint pain mainly caused by osteoarthritis. Hip and knee joint replacements are common, highly successful operations bringing many patients relief from pain, and improve mobility.

Prosthetic joint infections (PJI) are often difficult to diagnose; diagnosis often relying on a combination of clinical findings, microbiological data and histological evaluation of periprosthetic tissue. The majority of recent studies demonstrate a higher sensitivity for the culture of sonication fluid (62–94%) than periprosthetic tissue (55–88%).

The Royal Devon & Exeter NHS Foundation Trust provided a specialist multidisciplinary team. We evaluated the use of sonication for identifying pathogens during revision hip and knee replacement in our unit with the intention of applying for further grants to study this technology in more detail; it was a diagnostic feasibility study. The target recruitment was 50 patients; 25 consecutive patients undergoing revision hip arthroplasty for any reason, and 25 undergoing revision knee arthroplasty for any reason. The majority of patients were identified in outpatient clinics.

Our results show that tissue culture remains more sensitive than sonication. The sensitivity for direct sonication was 75% compared with 80% for tissue culture; sensitivity of enriched sonication was 80 %, compared to the unit results for tissue culture of 83%. The combined sensitivity of tissue culture was better as a higher number of tissue specimens were obtained.

The different methodology might explain reported differences between this and other studies; however, our study does not support the use of sonication as the only tool in the diagnosis of PJI.

Aim

Diagnosing a prosthetic joint infection (PJI) can be difficult. Several imaging modalities are available, but the choice which technique to use is often based on local expertise, availability and costs. Some centers prefer to use 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) as first imaging modality of choice, but due to a lack of accurate interpretation criteria, FDG-PET is currently not routinely applied for diagnosing PJI. With FDG-PET it is difficult to differentiate between FDG uptake due to reactive inflammation and uptake due to an infection. Since the physiological uptake pattern around a joint prosthesis is not fully elucidated, the aim of this study was to determine: i) the FDG uptake pattern in non-infected total hip prostheses and, ii) to evaluate whether there is a difference in uptake between cemented and non-cemented prostheses.

Introduction

Increasingly young and active patients are concerned about revision arthroplasty forcing the manufacturers to think about revision prostheses that fit to this population while meeting the indications and fitting with bone losses and ligament deficiencies. One of those industrials claims that its system allows the surgeon to rise the constraint from a posterior stabilized (PS) prostheses to a semi-constraint total stabilized (TS) prostheses without modifying the gait pattern thanks to a similar single radius design. The aim of the study was to compare gait parameters in patients receiving either PS or TS knee prostheses.

Abstract

Aims

To evaluate the place of the massive prostheses in the most complex periprosthetic infections cases (PJis).

The ODEP (Orthopaedic Data Evaluation Panel) rating system should offer a surgeon and patient extra information when making a choice on which implant to use. However, in the current economic environment, ratings may also influence implant choice by contracting bodies. Our aim was to determine the performance of commonly used Acetabular and femoral components in our unit and compare these to their published ODEP ratings (or absence of rating).

We analysed all of the following primary THR components (12,792) for revision for any reason, using same date ranges as ODEP where more than 100 implantations had occurred. Hip components: Trinity (3A in 2013), Trilogy (10A* in 2016), Atlas (10A in 2013), Trilogy TMT (10A 2010) Durom (not rated), BHR (10A, 2010), ACCIS (not rated); Femoral components: Taperfit (10A in 2013), Taperloc (10A* in 2016), Metafix (3A in 2013), CPT (10A in 2012), Ecofit (not Rated), ESOP (not rated), Minihip (3A 2013), Durom (not rated), BHR (10A 2010), ACCIS (not rated).

Analysis of Kaplan Meier survival curves was undertaken for all components. The rated components and non-rated components were compared using HR and logrank tests for all time groups when ratings were introduced. No statistical difference was observed in any group except for the Trinity cup which had a 98.2% (1344 cups) survival at 6 years.

Component survival in our unit was better than ODEP suggested failure for A category of not more than 1% per year, for all components.

Whilst we applaud the intention to improve data available for prostheses, the present ODEP system does not distinguish between performances of different implants in our unit. We therefore recommend care when relying upon ODEP ratings to make clinical or contracting decisions.

Prosthetic joint infections (PJI) caused by Streptococcus species are relatively common.

The aim of our study was to assess outcome after treatment for early and late PJI with Streptococcus species after a follow-up of two years.

For this study we retrospectively included all patients with primary or revision total knee arthroplasty (TKA) or total hip (THA) arthroplasty, a minimum of two periprosthetic tissue cultures positive for Streptococcus species and a minimum follow-up of one year. According to international guidelines patients were classified as having early or late PJI. All patients with an early PJI were treated according to a standard treatment protocol, i.e. debridement and retention of the prosthesis, followed by adequate antibiotic therapy. Patients with late PJI underwent a debridement followed by adequate antibiotic therapy or joint revision. Patients’ hospital records were reviewed and we evaluated the status of the original prosthesis after an infection.

Forty cases were included; 24 early and 16 late PJI. For early PJI, open debridement was performed in all patients, after a mean of 19 (range: 9 – 80) days. At final follow-up 21 prostheses (88%) were still in situ and without clinical signs of infection. Eight cases (41%) of late PJI were successfully treated with debridement and retention. Nine patients (59%) underwent a one- or two-stage revision. At final follow-up 16 patients (100%) with late PJI had a prosthesis in situ. Streptococcus dysgalactiae species accounted for more than 50% of the early infections, followed by Streptococcus agalactiae with 30%.

In case of PJI with Streptococcus species open debridement and retention of the prosthesis should be performed followed by adequate and long-term antibiotic treatment. As expected, the retention rate for early PJI is much higher than that for late PJI.

Introduction: Reasons why patients refuse wearing their upper limb prostheses deserve to be studied.

Method: Amputees were recruited from the clinics as well as from health- and accident insurances and Veterans’ Service Offices. Questions covered the patients’ medical history of amputation, their prosthetic supply and their present living conditions. 454 participants returned the anonymous questionnaire and could be entered into the study.

Amputation was caused by war (287), civil trauma or illness (123) and congenital (44). Age ranged from 3 – 96 years, with mean of 67.8. Distribution regarding sex and side was 411m/43 f and and 211 right/223 left. 20 had bilateral amputation. In 216 patients the dominant side was affected. Level of amputation was: wrist 36, BE 164, elbow 9, AE 201, shoulder 23, forequarter 3, unknown 18.

Prosthetic devices were classified as passive (i.e. cosmetic and passive work prostheses) or active, i.e. electrically- or body-powered prostheses as well as the combination of the two.

In the statistical analysis null hypothesis was that no factor influences the acceptance rate. Significant differences are accepted when p< 0.05.

Results: Electrically-powered prostheses were accepted best. Cosmetic prostheses were accepted well when stigmatization in the context of ethnic origin or religious affiliation may be important.

Acceptance rate was influenced by: Country of origin, religious affiliation, sex, learned occupation, therapist involved in training, return to work, incapacity for work, job held after amputation, own initiative in initiating prosthetic care, loss of friends or partners, level of amputation and the combined parameters AE-amputation and non-dominant side.

No influence was found for education, age at amputation, marital status, side of amputation, recommendation of prosthesis, time until first prosthetic fitting, phantom pain and phantom feeling, return to sports or hobbies, consumption of tobacco, alcohol or sedatives.

Discussion: Looking at all patients, the rates of acceptance of the various prosthetic types equals those found in the relevant literature. However, this study is much more detailed, looking at many different parameters and their combinations and can therefore provide some guidance to the successful prescription of upper limb prostheses. Nowadays electrically-powered prostheses are generally better accepted than all other types and should therefore be provided more often.

Summary

The posterolateral overhang of the femoral component was measured using 3-D templating software. Rounded and reduced shape of the posterolateral corner in the femoral component would be beneficial.

Introduction

Dual modular hip prostheses were introduced to optimize the individual and intra-surgical adaptation of the implant design to the native anatomics und biomechanics of the hip. The downside of a modular implant design with an additional modular interface is the potential susceptibility to fretting, crevice corrosion and wear [1–2]. The purpose of this study was to characterize the metal ion release of a modular hip implant system with different modular junctions and material combinations in consideration of the corrosive physiological environment.

Background

Aseptic loosening of prostheses is the most common cause for failure in total joint arthroplasty. Particulate wear debris induces a non-stop inflammatory-like response resulting in the formation of a layer of fibrous periprosthetic tissue at the bone/implant interface. The current treatment is an invasive revision joint replacement surgery. However, this procedure has a high morbidity rate, therefore, a less invasive alternative is necessary. One approach could be to re-establish osseointegration of the joint prosthesis by inducing osteoblast differentiation in the periprosthetic tissue. Therefore, the aim of this study was to investigate the capacity of periprosthetic tissue cells to differentiate into the osteoblast lineage.

A longitudinal study was done assessing the latest radiographs available in a series of collarless Corail uncemented stems which have reported survival rates of 95% at 20 years. Parameters scored included the degree of “Ghosting” or delamination, the Gruen, the stem fit in the femoral canal and the degree of calcar resorption. Patient and implant demographics were noted.

At 3 years the loosening rate was 23% reaching 64% at 6 years after the index procedure. It was present in all age groups, with a peak in the 24 to 49 year age group. Males and females had the same occurrence. When it was present this was always in zone 1. It was present in 6% of patients in zone 7, but then always associated with zone 1 changes. High and standard off-set stems had the same loosening rates. The looser fit of the stem the higher the incidence of loosening. There was no correlation to the type of bearing surface or the degree of calcar resorption. Those patients with a BMI of 25 – 35 had lower loosening rates compared to those with higher or lower BMI's.

We postulate that cancellous bone on-growth onto the hydroxyapatite coating associated with loading flexural micro-motion leads to hydroxyapatite being pulled off the smooth stem substrate in zone 1. Progressive delamination of the hydroxyapatite then occurs. The triple-tapered design though imparts continued stability.

We report high loosening rates in the Corail stem and suggest a mechanism for its development.

In cases of tumours, severe bone loss, etc., special pros-theses are sometimes required. It is also important to have a prosthesis that permits a switch from a primary knee system to a revision knee to a hinged knee.

This paper discusses and demonstrates some locally-manufactured prostheses.

Total hip joint replacement (THJR) for high riding congenital hip dislocation (CDH) is often performed in young patients, and presents unique problems with acetabular cup placement and leg length inequality.

A database and the NZ Joint Registry were used to identify 76 hips in 57 patients with a diagnosis of CDH who underwent THJR in the Wellington region between 1994 and 2015. Records and radiographs of 46 hips in 36 patients classified pre-operatively as Crowe II, III or IV were reviewed. Surgical technique used a direct lateral approach, the uncemented acetabular component was located in the anatomic hip center and a primary femoral stem was used in all but one hip. Whether a step-cut sub-trochanteric femoral osteotomy was performed depended on degree of correction, tension on the sciatic nerve, and restoration of leg length.

For the 36 patients classified as Crowe II or higher, the average age at operation was 44 years (26 – 66), female:male ratio was 4.5:1 and follow-up averaged 10 years (2 – 22.3). Of the 15 hips classified as Crowe IV, 10 required a step-cut sub-trochanteric femoral osteotomy to shorten the femur, but 5 were lengthened without undo tension on the sciatic nerve. Nine Crowe IV hips received a conventional proximally coated tapered primary femoral component. Oxford hip scores for 76% of patients was excellent (> 41/48), and 24% had good scores (34 – 41). All femoral osteotomies healed. Five hips have been revised, one at 2 years for femoral loosening, one at 5 years for dislocation, two at 12 years for liner exchanges, and one at 21 years for femoral loosening.

THJR using primary prostheses for CDH can provide durable long-term results.

Background

Hemiarthroplasty of the hip involves the replacement of the femoral side of the joint with a metal prosthesis, resulting in metal-on-cartilage articulation. The two most common types of hemiarthroplasty used are the Austin Moore and the Thomson, both of which are available in either Titanium (Ti) or cobalt chromium (CoCr). Hemiarthroplasty may be more cost effective in elderly patients who have lower life expectancy and are less active.

1. Fourteen patients whose Kienböck's disease was treated by prosthetic replacement, and who have had an acrylic lunate prosthesis in place for periods of eight to twenty years, have been reviewed.

2. In most patients pain, weakness and limitation of movement are less than they were before operation. Four wrists are completely painless and the other ten have only occasional slight pain. The average range of antero-posterior movement is 100 degrees.

3. Radiological signs of osteoarthritis are either absent or slight in ten wrists: this is considered to be due to the success of the prosthesis in maintaining the carpal architecture, even after prolonged heavy use.

Introduction

Clinical symptoms arising from corrosion within taper junctions of modular total hip prostheses are of increasing concern [1]. In particular, bi-modular implant designs showed increased failure rates due to wear originating from the neck-stem junction [2]. In-vivo corrosion-related failure is less frequently observed for head-stem junctions [3]. It is hypothesized that fretting and crevice corrosion are associated with micromotions between the mating surfaces of a taper junction [4]. The aim of this study was to measure micromotion occurring within a head-stem junction of a conventional prosthesis and clarify by how much it is exceeded in a neck-stem junction of a bi-modular prosthesis that exhibited severe corrosion and early implant failure.

Aim

A number of orthopaedic strategies have been described for limb salvage following periprosethic joint infection (PJI). However, this is often only possible with concomitant soft tissue reconstruction in the form of flap coverage. The purpose of this study was to determine the long-term clinical outcome of patients who underwent pedicled gastrocnemius flap coverage as part of their treatment for knee PJI.

Replacing a fused or ankylosed hip with a prosthesis has several advantages. It reduces the pain in the lumbar-sacral spine and the ipsilateral knee. It gives a better range of movement and leg length is restored.

In this study we present our experience of 50 cases of total hip arthroplasty in fused or ankylosed hips. Aetio-pathogenesis was rhizomelic spondylitis in 35 cases, sequelae of cox it is in 2, posttraumatic in 4, Ankylosis in 6, and fusion in 3. For clinical assessment we used the Merle D’Aubignè score, and for radiographic evaluation we used the Gruen method of area subdivision

Of the 50 prosthesis implanted, 3 were removed due to aseptic loosening. The other were the radiographically stable after an average follow-up of 12 years. Preoperative clinical scores were: pain (2.9), range of motion (2.5), and walking (2.1). At the latest exam the scores were: pain (5.5), motion (4.6), walking (4.5). Preoperative leg shortening was 3.5 cm, whereas at the latest exam it was 0.9 cm. Lumbalgia decreased notably in 62%.

Total hip arthroplasty may have advantages over fusion on one hand, but on the other it is technically more difficult and gives results that are inferior to common indications. It is therefore important to assess patients (time of fusion, age of patient, residual muscular function) preoperatively to obtain good results.

Buechel and Pappas invented a modified version of LCS RP system (Co-Cr) with light material (Titanium), axial rotation limiting bar and improved conformity. The purpose of this prospective randomized study was to compare the minimum 3-year clinical outcomes including lightness, preference, and instability between the Co-Cr implant system and the Titanium implant system in bilateral total knee arthroplasty.

We prospectively enrolled 108 patients and 20 patients were lost to follow-up. Therefore, 88 patients (176 knees; mean age, 69.9±6.0years) were included in the study. The range of motion and clinical scores such as Knee Society score (KSS), Hospital for Special Surgery score (HSS) and Western Ontario and McMaster University (WOMAC) scores were measured preoperatively and postoperatively. At each follow-up, patients also complete a Likert scale questionnaire regarding subjective pain, lightness, left-right side preference (naturalness and satisfaction) and subjective instability.

There were no significant differences in all preoperative variables between two groups (p>.05). Mean follow-up period was 46.3±8.8 (36 to 72) months. The mean weight of Titanium implants was three times lighter than that of Co-Cr implants (133.9g versus 390.1g, p<.01). At the minimum of 3-year follow-up, there were no significant differences in pain, range of motion (ROM), clinical scores including KSS, HSS, and WOMAC between both groups. Also, the study showed no significant differences with subjective pain, lightness, preference (convenience, naturalness, and satisfaction), and subjective instability between the Co-Cr protheses and the Titanium protheses (p>.05).

No differences in clinical outcomes as well as subjective side-to-side differences between the Co-Cr prostheses and the Titanium prostheses were observed in the minimum 3-year follow-up. This implies that patients do not feel differently with two different weighted implants in mid-term follow-up.

Introduction

There is much current debate concerning wear and corrosion at the taper junctions of large head total hip replacements, particularly metal-on-metal hips. Is such damage a modern concern or has it always occurred in total hip replacement but not previously noted. To investigate this five explanted V40 Exeter femoral stems (Stryker Howmedica) were obtained following revision surgery at a single centre. In all cases, the 24–26 mm femoral heads were still attached.

Despite the generally inferior clinical performance of acetabular prostheses as compared to the femoral implants, the causes of acetabular component loosening and the extent to which mechanical factors play a role in the failure mechanism are not clearly understood yet. The study was aimed at investigating the load transfer and bone remodelling around the uncemented acetabular prosthesis.

The 3-D FE model of a natural right hemi-pelvis was developed using CT-scan data. The same bone was implanted with two uncemented hemispherical acetabular components, one metallic (CoCrMo alloy) and the other ceramic (Biolox delta), with 54 mm outer diameter and 48 mm bearing diameter. The FE models of the implanted pelvis (containing ∼116000 quadratic tetrahedrals) were generated using a submodelling approach, which were based on an overall full model of implanted pelvis (containing ∼217600 quadratic tetrahedrals) acted upon by hip joint force and twenty one muscle forces. The apparent density (ρ in g cm⁻³) of each cancellous bone element was calculated using linear calibration of CT numbers of bone, from which the Young's modulus (E in MPa) was determined using the relationship, E = 2017.3 ρ^2.46 [1]. Implant-bone interface conditions, fully bonded and debonded with friction coefficient μ = 0.5, were simulated using contact elements. Applied loading conditions consist of two load cases during a gait cycle, corresponding to 13% and 52% of the walking cycle. Fixed constraints were prescribed at the pubis and at the sacroiliac joint. The bone remodelling algorithm was based on strain energy based site-specific formulation [2]. The FE analysis, in combination with the bone remodelling simulation, was performed using ANSYS FE software.

The predicted changes in peri-prosthetic bone density were similar for the metallic and the ceramic implant. For debonded implant-bone interface, stress shielding led to ∼20% reductions in bone density at supero-anterior, infero-anterior and posterior part of the acetabulum (Fig. 1). However, bone apposition was observed at the supero-posterior part of the acetabulum, where implantation led to ∼60% increase in bone density (Fig. 1). The effect of bone resorption was higher for the fully bonded implant-bone interface, wherein bone density reductions of 20–50% were observed in the cancellous bone underlying the implant (Fig. 1), which is indicative of implant loosening over time. However, implantation led to an increase in bone density around the acetabular rim for both the interface conditions (Fig. 1). These results are well corroborated by the earlier studies [3, 4]. Implantation with a ceramic component resulted in 2–7% increase in bone density at supero-posterior part of the acetabulum as compared to the metallic component, for the debonded interface condition. Considering better wear resistant properties and absence of metal ion release, results of this study suggest that the ceramic component might be a viable alternative to the metallic prosthesis.

Purpose

The success rate of surgical debridement and prostheses retention for acute periprosthetic joint infection (PJI) is controversial. This study aims to report our experience in managing acute PJI following total knee arthroplasty (TKA) with surgical debridement and prostheses retention, and to identify the prognostic factors that may influence the surgical outcomes.

Alumina and zirconia are known for their general chemical inertness and hardness. These properties are exploited for implant purposes, where they are used as an articulating surface in hip and knee joints. Their ability to be polished to a high surface finish make them an ideal candidate for such wear applications, where they compete against materials such as ultra-high-molecular-weight polyethylene.

Alumina is a highly inert material and resistant to most corrosive environments. The term high alumina ceramics refersr to materials that have a minimal content of 97% of alumina. If there is a 99% minimal percentage of alumina it is called high purity alumina ceramics. In its _ phase (more famous than corundum), characterised by its particular structure and stability, high purity alumina has been being used in orthopaedics since 1970, in the articulations of the hip prostheses.

BIOLOX^®forte (commercially available since 1994) is high purity alumina (ca 99.7 %) with a small percentage of magnesium oxide (MgO). Approximately 50 years ago, MgO was introduced during the sintering phase of alumina because it was discovered that a small amount of this additive prevented the increase in grains of alumina during the sintering process. It was therefore possible to have a more homogenous and dense microstructure; both characteristics directly correlated with the mechanical resistance. The suffix forte derives from the increased mechanical characteristic and continuous optimisation of the fabrication technology.

One of the main factors involved in wear reduction is the characteristic molecular structure of alumina. Its superficial layer is composed of oxygen atoms that create a residual electric power which interacts with polarized molecules of the lubricant, tying it to the surface by strong Van der Waals ties. Therefore the presence of a fluid film that reduces the coefficient of clutch between the two surfaces involved during the articulation is guaranteed.

The colour of alumina components varies. Originally it is ivory, but it can easily become brown after sterilization with gamma beams that interact with the free valences introduced by the MgO. This change in colour does not change the mechanical characteristics. Currently the systems are completely modular and allow a wide choice of couplings. In 1984 and subsequently in 1995, the introduction of ISO norms for the production of ceramics ball-heads and inserts and the concept of conical fixation has provided higher reliability.

Today, the alumina BIOLOX^®forte components are prepared in clean-rooms, sintered with high quality control processes, laser marked and accurately inspected and tested. The tolerances between ceramics (ball-heads and inserts) and metallic parts (taper and metal shell) are fundamental for increasing implant reliability. It is important to control and validate the stems and cups which the ceramic parts are applied on. Correct assembly and the respect of the compatibilities between parts (angle, material, producer) guarantee the longevity of the implants.

Actually, in the orthopaedic field, alumina is mainly used in standard applications of hip prostheses. Ball-heads of 22 mm in diameter, lengths of neck type XL, and the knee prostheses are not possible because the mechanical characteristics of alumina do not allow for the elevated stress values requested for these special applications.

Between 1975 and 1977, it was discovered that the strength and toughness of alumina could endure a remarkable increment by developing composites with oxide of zirconium (zirconia). In zirconia, during the phase of cooling from temperatures over 1170°C, the grains go through a change of phase (from tetragonal to monoclica), with an increase of 3% of volume. At ambient temperatures the monoclica phase is stable. This transformation is martensitic, with energy absorption, and involves a heat-proof change of the symmetry of the structure. In the case of dispersed grains of zirconia in the alumina matrix, the transformation absorbs the energy of the crack and the strength of the ceramics increases. With the use of yttria (Y₂O₃) to stabilise the zirconia the problem of the structure defects can be resolved.

A percentage of zirconia stabilized with yttria (Y-TZP) was introduced in the alumina matrix and other mixed oxides to counterbalance the reduction of the hardness caused by particles of zirconia and to create lengthened particles during the sintering.

All these studies have been used to create the new ceramic BIOLOX^®delta. Tests of biocompatibility in agreement with norms EN 30993 have been carried out, so that implants can be made of these new composite ceramics.

Since 1970, more than 3,500,000 ball-heads and 350,000 inserts of alumina BIOLOX^® have been implanted. Owing to the grain size, currently reduced to values under 2 μm, the value of the mechanical resistance has been raised to about 580 MPa. The increase in the mechanical characteristics, the new shapes and the conical fixation have reduced the risk of fracture of the BIOLOX^®forte ball-heads and inserts to around 0.01% (Ø28 mm), maintaining the excellent tribology and wear characteristics. Many laboratory tests and clinical cases have shown that the wear rate of the alumina-alumina bearing complex is extremely low (0.001 mm/year). If compared with metal-polyethylene (0.2 mm/year) it shows a drastic reduction of particles of debris and therefore of the osteolysis problem

BIOLOX^®delta has a bending strength of around 1000 MPa, which is more than double that of the alumina ISO (400 MPa). In the minimum fracture load test, ball-heads of 28 mm Ø millimeter (neck L) have achieved values of around 100 KN, well beyond the 46 KN requested by the FDA. Multiple cycles of sterilisation in autoclaves have demonstrated that the the mechanical and tribological characteristics of BIOLOX^®delta are not altered.

On the basis of these results, BIOLOX^®forte can be considered a reliable alternative to other materials in standard applications and the new alumina composite BIOLOX^®delta will allow the realization of medical ceramics devices, already in the study phase, such as knee prosthesis, 22-mm ball-heads and thinner wall-thickness of inserts, which could not be developed up to now with the available ceramic materials.

Friction was studied in 67 retrieved cemented cups with 32 mm internal diameter. Friction was measured under 1.0 KN of static load. High molecular hyaluronic acid was adapted as a lubricant. Thirty cups were combined with alumina heads and 37 were combined with metal heads. The years cups were in situ was 7.5 (3.2–13.2) for alumina-polyethylene implants and 8.9 (1.5–15.7) for metal-polyethylene implants (p> 0.05).

The revision rate at 15 years follow-up was higher in metal-polyethylene (PE) implants (57%) than that of alumina-PE implants (40%) (p< 0.05). The prevalence of cup loosening was less in alumina-PE implants (12/30) than in metal-PE implants (29/37) (p< 0.01). Less wear was observed in alumina-PE implants (1.15+−0,80mm) than in metal-PE implants (1.62+−0.61mm) (p< 0.01). Less wear was observed in cups without loosening (alumina-PE implants: 1.84+−0.57mm, metal-PE implants: 1.75+−0.51mm) than in those with loosening (alumina-PE implants: 0.69+−0.56mm, metal-PE implants: 1.31+−0.73mm) in both types (alumina-PE implants: p< 0.01, metal-PE implants: p< 0.05). Less wear rate was observed in cups without loosening (alumina-PE implants: 0.11+−0.05 mm/year, metal-PE implants: 0.14+−0.05mm/year) than in those with loosening (alumina-PE implants: 0.17+−0.03 mm/year, metal-PE implants: 0.22+−0.09mm/year) in both types (alumina-PE implants: p< 0.01, metal-PE implants: p< 0.05). The coefficient of friction increased in proportion to the progress of cup wear in both types (alumina-PE implants: r2 =0.217, p< 0.01, metal-PE implants: r2 =0.183, p< 0.01). Relation between the coefficient of friction and stability of implants was not detected in both types, while alumina-PE implants had lower coefficient of friction (0.137+-0.056) than metal-PE implants (0.209+−0.098) (p< 0.01). The torque of metal-PE implants without stem loosening (0.137+−0.053) was larger than that of alumina-PE implants with stem loosening (0.274+−0.088) (p< 0.01).

The results suggest that wear has greater influence on stability of implants than the friction, whereas coefficient of friction increases in worn implants.

Introduction: Modern navigation technology appears to be acquiring an established place in the fields of total knee arthroplasty. This technology helps the surgeon to apply his manual skills with greater precision and thus more effectively, and its positive impact on the quality of surgical treatment has already been demonstrated. The Surgetics navigation system described in this paper shows that the Technology can be adapted to the requirements of daily surgical practice, without compromising its utility to the surgeon.

The Surgetics navigation system: The Surgetics navigation system represents a multifunctional tool, that can be used in a lot of fields in orthopedic surgery. For every special use as prosthesis, osteotomies ore ACL-replacement, the hard- and software is adapted thus not any compromise should be accepted for the surgical procedure. In total knee prostheses navigation no ct- scan is needed preoperatively, the patented bone morphing procedure is entering all the anatomic datas to the computer for an absolutely correct positioning of the implant. Consequently the pre- and intraoperative inputs are reduced to a minimum.

Material: To evaluate the advantage of the Surgetics navigation system in total knee prosthesis, the technical datas of a non constrained knee prostheses with rotational platform (ESKA) had been entered in the system. The patient datas, concerning size of the knee joint, leg axes, center of rotation of the hip joint and ligament balance are transmitted by rigid bodies and a pointer with 6 reflecting markers each and a stereo infrared camera. The rigid bodies are fixed by two thin Steinmann-nails each in the tibial and femoral bone. On a monitor each step of the bone morphing and the surgical procedure is shown. Thus the bonecutting guides are placed in an absolutely correct position. The extension – and the flexion gap is presented as well for a precise ligament balancing. The additional time for using this system is not extending 15 minutes.

Methods: 50 ESKA total knee prosthesis with rotational platform have been implanted with standard instrumentation and another 50 with the use of the Surgetics navigation system. In both groups the reason fore surgery has been nearly identic. In 92% the patients suffered from arthritis. More varus than valgus deformities have been seen. The range of deformity went up to 25 degrees.In 8% posttraumatic deformities with consecutive arthritis leaded to surgery. Preoperative X rays of the whole leg in a standing position have been taken, the shifting of the bearing axes in comparison to the center of the knee joint has been determined. The maximum of this shifting was 6.3 cm. The HSS score has been used to describe the clinical findings pre- and postoperativly. In 38 cases of the S- group and in 39 of the N- group the joint was inserted cementless. 2 in the s-group and 1 in the n-group in a hybrid technic, the rest cemented.

Results: The follow up time in both groups ranged from 6 month to one year.Because it has not been the purpose of this paper to report on long time clinical results or survivership, this short follow up time seems to be acceptable for the evidence upon the value of a navigation system.The postoperative x- rays showed a correction of the bearing axes of the leg in relation to the center of the knee joint in a 4 degree corridor in 94,6% for the N – group and in 69,9% in the S- group. Two failures in the N-group came from a change of position of the rigid bodies during surgery due to pushing them by lack of caution.

Conclusion: The surgetics navigation system is a technical help for the orthopedic surgeon, improving the radiological and clinical results in knee arthroplasty. The correction of the bearing axes in the 4 degree corridor is significantly higher in the N-group then in S-group. This has as well an important influence on the clinical outcome. The HSS score by first impression differs by 6 points. The use of the system is economically reasonable,because preoperative ct- scan is not needed and the time of surgery is not extended more than 15 minutes.The Surgetics navigation system with its sophisticated software is leading the surgeon visually through the bone morphing procedure, the bone cutting process and the ligament balancing step by step.

Introduction

Total hip prostheses which use a ceramic head within a metal liner are a relatively recent introduction. As such, survivorship rates from independent centres alongside explant analysis are rare. The early experience with this novel ceramic-on-metal (CoM) bearing couple is reported.