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

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

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

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.

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

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

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.

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

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.

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.

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.

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.

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.

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.

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.

An inclusive classification system is required if valid comparisons are to be made between the various types of implants used for total elbow replacement (TER). The aim of the study was to consider the characteristics of the prostheses developed for TER in order to classify these into clearly defined categories.

A descriptive term such as ‘surface replacement’ is unhelpful as this would embrace every design.A classification based solely upon degree of resistance to movement –‘constraint’-is untenable. ‘Constrained’ or ‘fully constrained’ accurately describes a uni-axial hinge, but the term ‘semi-constrained’ defies description.

The terms ‘unconstrained’ or ‘non-constrained’ applied to a joint defy understanding. If articulating surfaces offer no resistance to movement as these terms imply, then there can be no contact between those articulating surfaces.

A definable, inclusive classification can be formulated by considering the mechanical characteristics of the articulating surfaces of each design.

Every design of TER can be classified into one of two broad groups, Linked or Unlinked. We define linked components as those offering resistance to distraction which includes snap-fit designs. Each of these two groups can then be sub-divided into ‘congruous’ or ‘non-congruous’ designs depending upon the shape of the articulating surfaces.

This classification can therefore be summarised as: Linked Congruous – original uni-axial hinge, snap fit designs; Linked Non-congruous – ‘sloppy hinge’; Unlinked Congruous – eg. Capitellocondylar,Souter/ Strathclyde,Roper-Tuke etc; and Unlinked Non-congruous – Kudo, iBP

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.

Background: In a previous randomized studiy using Röntgen Stereometric Analysis (RSA), we showed that oral bisphosphonates reduce the mean migration distance during the first 6 months. In a similar randomized study, bisphosphonates applied locally at the operation had a similar effect. These studies showed a 0.1 mm difference in mean value between groups. Does such a small difference matter? We addressed this question by use of frequency analysis.

Methods: The 2 previous studies were combined for analysis, and designated as bisphosphonate (n=44) or control treated (n=49). We analysed the migration vector (for the center of the rigid body) by use of a set of algoritms for frequency distribution analysis called Rmix. The migration vector lengths were assumed to be a compound of log-normal distributions. The frequency analysis determined if the observed frequency distributions were best described as a single, or a sum of 2 or more lognormally distributed subgroups.

Results: After 6 months, the control patients had formed 2 subgroups, one comprising 85% of the patients. The dichotomy was significant (p=0.016).

After 2 years, the dichotomy persisted (p=0.027). In the bisphosphonate-treated patients, no dichotomies could be found. The distribution of the migration vector length appeared similar to the larger and less migrating subgroup among the controls.

Discussion: The risk of aseptic loosening for cemented knees is extremely small. However, the migrating subgroup among our control patients may be at risk of loosening, and would have run a high risk if they were young and active. This subgroup did not appear with bisphosphonate treatment

Summary: In previous comparisons we found a slight decrease in mean value with bisphosphonates. The present analysis shows that this reflects the disappearance of a small subgroup with large migration.

The use of silicone inner sockets, with or without the incorporation of shuttle locks, has greatly improved the function of artificial limbs. They cushion and protect the stump and provide a means for prosthetic suspension, allowing more comfortable use, especially in patients with ischaemic stumps. They also allow greater movement at the proximal joint.

Patient function is poorly characterised following revision TKA. Modern semi-constrained implants are suggested to offer high levels of function, however, data is lacking to justify this claim.

52 consecutive aseptic revision TKA procedures performed at a single centre were prospectively evaluated; all were revision of a primary implant to a Triathlon total stabiliser prosthesis. Patients were assessed pre-operatively and at 6, 26, 52 and 104 weeks post-op. Outcome assessments were the Oxford Knee Score (OKS), range of motion, pain rating scale and timed functional assessment battery. Analysis was by repeated measures ANOVA with post-hoc Tukey HSD 95% simultaneous confidence intervals as pairwise comparison. Secondary analysis compared the results of this revision cohort to previously reported primary TKA data, performed by the same surgeons, with identical outcome assessments at equivalent time points.

Mean age was 73.23 (SD 10.41) years, 57% were male. Mean time since index surgery was 9.03 (SD 5.6) years. 3 patients were lost to follow-up. All outcome parameters improved significantly over time (p <0.001). Post-hoc analysis demonstrated that all outcomes changed between pre-op, 6 week and 26 weeks post-op assessments.

No difference was seen between primary and revision cohorts in OKS (p = 0.2) or pain scores (p=0.19). Range of motion and functional performance was different between groups over the 2 year period (p=0.03), however this was due to differing pre-operative scores, post-hoc analysis showed no difference between groups at any post-operative time point.

Patients undergoing aseptic revision TKA with semi-constrained implants made substantial improvements in OKS, pain scores, knee flexion, and timed functional performance, with the outcomes achieved comparable to those of primary TKA. High levels of function can be achieved following revision knee arthroplasty, which may be important considering the changing need for, and demographics of, revision surgery.

Introduction

Revision hip arthroplasty is a technically challenging operation as proximal bony deficits preclude the use of standard implants. Longer distally fixing stems are therefore required to achieve primary stability.

1. A prosthesis under myo-electric control is described.

2. An advanced technique of proportional control of such a prosthesis is outlined.

1. The working of an electrically powered prosthesis is described.

2. The advantages of this method are discussed.

1. The use of acrylic cement in bonding femoral head prostheses to bone is described.

2. No sign of deterioration of the bond between the cement and bone has been seen in histological preparations up to three and a quarter years after operation, and no harmful effects have been recognised, or suspected, in 455 patients in whom it has been used.

3. The technique is considered justifiable in elderly patients where the medullary canal is large and the cortex of the femur is thin and brittle.

Purpose of the study: Staphylococcus lugdunensis, described in Lyon in 1988 by Freney, appears to be a member of the cutaneous perineal flora. Since the first description, S. lugdunensis infections are regularly reported. The germ has been reported as the causal agent for endocarditis on valve prostheses with a very severe prognosis, requiring surgery in addition to medical management. We wanted to ascertain the prognosis of such infections on joint prostheses and to determine if it is different from that with other staphylococcal species.

Material and methods: Since 1991, seven S. lugdunensis infections on a joint prosthesis (three total hip prostheses and four total knee arthroplasties) were identified in our department. The Api Id 32 staph (BioMérieux SA) test battery was used for identification. All patients underwent surgical treatment and were given a prolonged antibiotic regimen. Simple joint cleaning was performed in three cases, one requiring a one-stage prosthesis replacement. There were four two-stage prosthesis replacements. The antibiotic regimen was always long (3–8 months) and was continued as a palliative treatment in two patients who underwent simple cleaning.

Results: One elderly woman with multiple co-morbid conditions died after prosthesis removal before the replacement procedure could be performed. There were no cases of recurrent infection at 16 months and 6 years for the four prosthesis replacements (one- and two-stage procedures). Arthroscopic cleaning without removal of the TKA was a failure in one patient who required prosthetic replacement later. Two simple cleanings in elderly patients were failures and required continuous palliative antibiotics.

Discussion: Staphylococcus lugdunensis is generally considered to be very susceptible to antibiotics in vitro. In our experience, search for minimum inhibitory concentrations and minimum bactericidal concentrations have shown cures with rapid shifts which must be taken into consideration when choosing an antibiotic. With surgical removal of the prosthesis and adapted antibiotics, the prognosis of these infections is not different from other staphylococcal infections of joint prostheses. We did however note two cases of secondary infections, probably related to hematogeneous spread, which developed from an unidentifiable point in time.

Conclusion: Staphylococcus lugdunensis is a coagulase-negative staphylococcus with poorly known virulence properties. In our very small series of joint prostheses infections, therapeutic failure occurred when the infected prosthesis was not removed.

Purpose of the study: Reversed prostheses provide improved active anterior elevation in shoulders free of cuff tears by lengthening the deltoid and increasing is lever arm. The purpose of this work was to search for a correlation between arm lengthening and postoperative active anterior elevation.

Material and methods: One hundred eighty-three reversed prostheses were reviewed with minimum one year follow-up for a complete clinical and radiographic work-up. Using a previously validated protocol, arm lengthening was assessed either in comparison with the contralateral side or with preoperative measurements. A statistical analysis was performed to search for a correlation between lengthening of the humerus and the arm with active anterior elevation.

Results: Considering the entire series, mean lengthening of the humerus was 0.2±1.4 cm (range −4.7 to +5.4). Postoperative active anterior elevation was 141±27 (range 30–180). There was no correlation between humerus lengthening or shortening and active anterior elevation (p=0.169). A shorter arm produced an active anterior elevation at 121 and 0 – 1 cm lengthening an active anterior elevation at 140; lengthening 1 – 2.5 cm gave active anterior elevation at 144 and beyond 2.5 cm 147. The difference in active anterior elevation was statistically significant (p< 0.001) between patients with a shortening and those with a lengthening.

Discussion: Arm lengthening corresponds to a lengthening of the humerus plus a lengthening of the infra-acromial space. We found a statistically negative correlation between arm shortening (and thus deltoid shortening) and active anterior elevation and a positive trend between lengthening and active anterior elevation. Our measurement did not take into account the increased lever arm of the deltoid and thus only partially expresses the improvement in deltoid function. Nevertheless, our study shows that objective evaluation of deltoid lengthening is possible pre- intra- and postoperatively and that this measurement can be correlated with postoperative functional outcome.

Introduction

Total hip replacement is one of the most successful orthopaedic surgeries, not least because of the introduction of modular systems giving surgeons the flexibility to intraoperatively adapt the geometry of the artificial joint to the patient's anatomy. However, taper junctions of modular implants are at risk of fretting-induced postoperative complications such as corrosion, which can lead to adverse tissue reactions. Interface micro-motions are suspected to be a causal factor for mechanical loading-induced corrosion, which can require implant revision.

The aim of this study was to determine the micro-motions at the stem-head taper interface during daily activities and the influence of specific material combinations.

Wear and wear debris induced osteolysis is recognised as a major cause of long term failure in hip prostheses. Historically ultra high molecular weight polyethylene acetabular cups produced micron and submicron wear particles which accumulated in peri prosthetic tissues, and stimulated macrophages to generate wear debris induced osteolysis. Acceleration of wear and osteolysis was caused in historical materials by oxidative degradation of the polyethylene following gamma irradiation in air, and by third body damage and scratching of metallic femoral heads. Current conventional ultra high molecular weight polyethylene cups are irradiated in an inert atmosphere to reduce oxidative degradation and are articulated against ceramic femoral heads to reduce third body wear. More recently modified highly cross linked polyethylene has been developed, and while these materials produce a four to five fold reduction in wear volume the wear particles have been found to be more reactive, resulting in only a two fold reduction in functional osteolytic potential. The question remains as to whether this performance is adequate for high demand patients, particularly if larger diameter femoral heads are to be used.

Recent interest in improved function, stability and reducing dislocations has generated interest in using larger diameter heads and hard on hard bearings.

Alumina ceramic on ceramic bearings have shown a one hundred fold decrease in wear compared to highly cross linked polyethylene materials, and cell culture studies have shown the wear particles to be more bio-compatible and less osteolytic potential.

Metal on metal bearings also produced very low wear rates compared to polyethylene. The wear particles are very small, 10 to 50 nanometers in size, some concern remains about the systematic release of metallic ions. These are lubrication sensitive bearings, and they unlike polyethylene wear decreases as the head size increases due to improved lubrication. Size 36 mm metal bearings are now commonplace for total joint replacements with even larger head sizes being used for surface replacement solutions.

The demand for increased function and improved stability is leading to increased use of hard on hard bearings with larger diameter heads.

Aim

A previous Dutch guideline for prophylaxis of hematogenous PJI (HPJI) caused defensive medicine and incorrect own guidelines. There was a need for a better national guideline, developed cooperatively by orthopedic surgeons and dentist.

Introduction: Discomfort and pain are common but unspecific symptoms in orthopaedic prosthetics. The majority of these symptoms are secondary to mechanical failure or loosening, while only a small proportion is related to infection. The differentiation between synovitis, loosening or infection is important for a correct therapeutical management, but it is often difficult using noninvasive techniques.

Positron emission tomography (PET) with 2-deoxy-2-[18F]fluoro-D-glucose (FDG) has evolved from a research imaging modality to a clinical practice for the assessment of malignancies. FDG, a nonspecific tracer of increased intracellular glucose metabolism, has been found to accumulate not only in malignant cells but also in infection and inflammation foci.

Aim of the study was to evaluate the usefulness of FDG PET scan in patients with joint replacement.

Materials and Methods: In this study we describe PET findings in 33 patients (age 42–88 yrs.) with hips (n. 16) and knees (n. 17) prostheses who had a complete operative and/or clinical follow-up; 42.5% had a pattern of mobilization. All patients underwent PET scan 60 minutes after i.v. injection of 185 MBq of 18F-FDG (transmission-emission, 3D acquisition). PET tomograms were evaluated by nuclear physicians without knowledge of the clinical diagnosis by visual interpretation, which was graded on a four-point scale according with common clinical classification (0 = normal pattern: not significant locoregional uptake; 1 = synovitis: synovial localized uptake; 2 = prosthesis loosening: synovial and soft tissues uptake; 3 = prosthesis infection: synovial, soft and bone tissues diffuse uptake).

Results: The results will be discussed in detail and correlated with clinical findings. The diagnostic value of PET, in terms of sensitivity, specificity and accuracy was compared with traditional radionuclear techniques (dynamic bone scan, 99mTc-labelled granulocytes).

Conclusion: We underline a good correlation between PET and clinical pattern (88% of cases). Particularly PET was able to correctly differentiate the prostheses loosening in the 100% of cases without infection and in the 77% of patients with infectious disease suggesting its usefulness in clinical practice also for detecting only inflammatory tissue such as synovitis. Moreover, the capability of PET to quantificate the inflammatory activity could be useful in the monitoring of the therapy. Further evaluation in a large group of patients is indicated.

Purpose: Among 115 cemented patellofemoral Bechtol-Blazina prostheses implanted between 1974 and 1991, we reviewed 59 knees in 41 women and nine men (nine bilateral implants). Material and methods: Mean patient age was 60 years and mean follow-up was ten years (6–16). The main indication was primary degenerative disease (82%) followed by chondrocalcinosis (6%), chondromalacia (7%) and secondary degeneration (5%). A previous procedure had been performed on 18 knees (14 patellofemoral and four femorotibial). Associated procedures were tubercle translocation (n=15), tibial osteotomy (n=2), and tension of the medial wing (n=1). The International Knee Society score was noted.

Results: According to the IKS, outcome was good or excellent in 91% of the knees and insufficient in 9% (knee score and function score). Mean ten-year survival determined with the actuarial method was 84.4%. It fell from 91.1% to 75.5% between the ninth and eleventh year due to femorotibial deterioration. There were no cases of phlebitis, infection or prosthetic loosening. Causes of failure were predominantly femorotibial (eight degradations) rather than femoropatellar (two snaps and three painful syndromes involving the lateral parapatellar area). Thirteen reoperations were necessary: tri-compartmental arthroplasty (n=8), modification of the trochlear orientation (n=1), release of the lateral patellar wing (n=3), demaquetisation (n=1). Total or nearly total pain relief was achieved for 80% of the knees. The mean flexion angle was 123° and stair climbing was considered normal in 91% of the patients. All knees were stable. Radiographically, there were six cases of polyethylene remodelling and one case of wear associated with major femorotibial deterioration. This absence of significant wear was, in our opinion, essentially due to the absence of a metal-backed patellar insert.

Discussion: The following indications can be retained on the basis of this series: the ideal indication is isolated patellofemoral osteoarthritis with dysplasia, relative indications are advanced-stage patellofemoral osteoarthritis with axial deviation having no clinical or radiographic (tangent view) impact. In this case, the patellofemoral implant allows postponing insertion of a tricompartmental prosthesis in middle-aged patients. Contraindications are patellar chondromalacia, chondrocalcinosis, low patella, and presence of associated femorotibial degradation.

Conclusion: The long-term clinical and radiographic results after patellofemoral arthroplasty make this procedure the treatment of choice for isolated and advanced-stage patellofemoral osteoarthritis on a normally axed limb when a conservative procedure cannot be performed or has failed. It provides effective pain relief and good knee stability. The operation is difficult and must use congruent implants to avoid the problem of prosthetic instability and patellar snaps.

Purpose: To assess the performance of a constrained liner in an unstable hip prosthesis.

Materials and methods: This is a retrospective study of 66 hip prostheses implanted in 66 patients by means of the same constrained cup (Lefevre, Lepine Group, France). The cup was implanted into 15 primary prostheses and 51 revision ones in order to treat recurrent dislocations (10 cases) or to prevent dislocations (56 cases with a deficit of the periarticular musculature or mental or neuromuscular disorders). The mean age was 76.7 years, 75.7% were female, 53% were operated in the right side and the mean follow up was 30.2 months.

Results: By the time the last review was made, four patients died for reasons not related to their hip surgery. One patient showed a dissociation between the femoral head and the stem at the level of the Morse taper; the head was trapped in the retentive liner and an open reduction was needed to replace the existing prosthetic head by a new one with a long neck. Another patient had a prosthetic infection that was treated by means of a two-stage replacement. Radiolucent lines were observed in de DeLee’s zone 1 in 1.5% of patients, in 3% the lines were in zone II and in 3% they were in zone. However, according to Hodgkinson’s radiographic criteria, no cups were loose.

Conclusions: Although retentive cups do address hip instability, the various cases of failure that have occurred, the appearance of radiolucencies and the concerns about their long-term fixation suggest that their use should be carefully weighted.

New generation alumina-on-alumina (A-A) prostheses have been introduced to try and overcome the problem of osteolysis often attributed to polyethylene wear particles liberated within conventional metal-on-ultra high molecular weight polyethylene (UHMWPE) joints. This study uses a hip simulator to compare the volumetric wear rates of five different radial clearances of A-A joints. Atomic force microscopy (AFM) provided topographic characterisation of the prosthesis surfaces throughout the wear test.

Materials and methods: The wear test was performed on the Durham hip joint wear simulator. The 28 mm diameter alumina ceramic couples investigated were manufactured by Morgan Matroc Ltd., in accordance with ISO 6474. Four radial clearances (33, 40, 48 and 74 μm) of A-A joints were tested to one million cycles with 25% new-born calf serum as the lubricant. Contact mode AFM (TopoMetrix Explorer SPM) was used to produce a topographical map of the poles of the four alumina heads every 0.1 million cycles. Every 0.2 million cycles the wear was assessed gravimetrically using a Mettler AE 200 balance (accurate to 0.1 mg).

Results and discussion: There was no measurable wear of either the heads or cups during this one million cycle wear period. Throughout the wear test the alumina equiaxed grain structure became apparent on the AFM images, the mean alumina grain size was 2 μm. The grain surfaces were below the mean femoral head surface height. Such topography was not observed on an as-received head. Some granular pull-out also took place. As the wear test proceeded, the average area surface roughness increased from 2.33 nm to 4.42 nm for the heads but stayed relatively constant for the cups (from 2.75 nm to 2.97 nm).

Conclusions: The very low wear produced by these A-A hip joints is very difficult to measure gravimetrically as it is close to the limits of resolution of the weighing equipment. The surface topography analysis, however, shows changes to the ceramic surfaces during the wear test and gives an indication of the wear processes and lubrication regimes acting within such joints. The authors wish to thank EPSRC for funding this research and Morgan Matroc Ltd. for supplying the joints.

Fluid film lubricating ability of a total hip prosthesis depends on the profile accuracies including surface-roughness or the sphericity of a head or a cup. Therefore, surface polishing is important. It was, however, difficult to polish the central portion of a cup or head using the conventional rotating machine. In the present study, we developed a polishing method combining a pendulum machine and a robotic arm. The effect of the accuracy improvement by this method was evaluated by the friction measurements on some test specimens.

Nine balls and a cup of Co-Cr-Mo alloy that were polished by a conventional process using a rotating machine were prepared for the prototype. The average diameter of the balls was 31.9648 mm with the sphericity of 0.0028 μm. The inside diameter of the cup was 31.9850 mm with the sphericity of 0.0044 μm. We combined a robotic arm and a pendulum apparatus to enable the further polishing. The ability of both automatic centering and change in the sliding direction was accomplished by this system. The sliding direction has been changed 180 times every ten degrees. The total distance of polishing was 120 m under vertical load of 100 N in a bath of saline solution containing abrasive grains of silicate of the diameter of 2μm. The surface roughness of the central portion of the cup, which is important area for the fluid film lubrication decreased from Ra 20.2 μm before the polishing to Ra 18.7 μm after the polishing.

A pendulum type friction tester was used for the assessment of the improvement of the lubricating ability by the polishing. The measurement was run over at 10 times under the conditions of the load of 600 N in a bath of saline solution. As the result, the frictional coefficients decreased from 0.1456–0.1720 before polishing to 0.1250–0.1300 after polishing. The polishing effect was, however, observed only at the specimens that radial clearances did not exceed the value of 50 μm.

The present results indicated that the surface polishing of the central portion of hip prostheses must improve the lubrication ability and the radial clearance before the finishing process should be chinked as possible.

Introduction

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

Introduction and Objectives: There is more experience with the use of cemented models of knee prosthesis. However, non-cemented models are proving to have equivalent survival. Our aim was to analyze our experience of long term survival of non-cemented total knee replacement prosthesis.

Materials and Methods: We included the patients operated in our unit between 1989 and 1996. In all cases the same implant was used (LCS Total Knee Replacement, Depuy, Warsaw, IN). We included a total of 129 knees (117 patients). The variables we studied were: Age, sex, follow-up time, KSS score, implant survival and reasons for revision.

Results: Follow-up was 14.5 years and mean age was 78.7 years. A total of 60 knees did not complete the study correctly. For the 69 knees that remained in the study, the results were: 11 TKR (16%) were reoperated: 2 due to dissociation-dislocation of the patellar component, 3 due to wear or rupture of the tibial polyethylene, 6 were revised due to aseptic loosening. There were no cases of infection. The mean KSS score was 90.29.

Discussion and Conclusions: In our experience, the use of non-cemented TKR prosthesis:

Provides an excellent clinical and functional result, assessed by KSS.

If we include all reoperations, survival free of reintervention was 84%.

Finger arthroplasty lacks the success seen with hip and knee joint replacements. The Van Straten Leuwen Poeschmann Metal (LPM) prosthesis was intended for the proximal interphalangeal (PIP) joints. However revision rates of 30% after 19 months were reported alongside massive osteolysis. Three failed LPM titanium niobium (TiNb) coated cobalt chrome (CoCr) components were obtained- two distal and one proximal.

All three components were analysed using an environmental scanning electron microscope (ESEM). This gave the chemical composition of the surface to determine if the TiNb surface coating was still intact. The distal components were analysed using a ZYGO non-contact profilometer (1nm resolution) with the proximal component unable to be analysed due to its shape. ZYGO analysis gave the roughness average (Ra) of the surface and determined the presence of scratches, pitting and other damage.

Images obtained from both the ZYGO and the ESEM indicated that the surfaces of all components were heavily worn. On the articulating surfaces of both distal components unidirectional scratching was dominant, while the non-articulating surface showed multidirectional scratching. The presence of unidirectional scratching suggested two-body wear, whilst the multidirectional scratching on the non-articulating surface of the distal component suggested that trapped debris may have caused three-body wear.

The ESEM chemical analysis showed that in some regions on the distal component the TiNb coating had been removed completely and in other areas it had been scratched or penetrated. On the proximal component the TiNb coating had been almost completely removed from the articulating surfaces and was only present in small amounts on the non-articulating surfaces. There was little evidence of bone attachment to the titanium coating which was intended to help provide fixation.

ESEM images showed the coating had been removed in some sections where there was minimal scratching, suggesting this scratching did not impact significantly in the coating removal. Therefore here the main cause of coating removal may have been corrosion, although scratching may have also have played a part.

The osteolysis reported clinically may have been linked to the wear debris from the failed coating.

In joint prostheses using ultra-high molecular weight polyethylene (UHMWPE) as bearing material, wear problems are not yet completely solved under severe conditions in various daily activities, although efficacious treatments such as crosslinking, addition of vitamin E and the grafting of phospholipid polymer improved the wear properties. In contrast, in healthy natural synovial joints possessing articular cartilage as biphasic bearing material lubricated with synovial fluid, minimal wear with extremely low friction has been maintained for a whole life. Therefore, the joint prosthesis with artificial hydrogel cartilage with similar properties to articular cartilage is expected to show superior tribological functions with very low friction and infinitesimal wear if the appropriate lubrication mechanism is actualized. In this study, the effectiveness of biphasic lubrication mechanism in hydrogel through significant load support by fluid phase is evaluated in finite element (FE) analysis for reciprocating motion.

As biocompatible artificial hydrogel cartilage materials, two kinds of poly (vinyl alcohol) (PVA) hydrogels were prepared by the repeated freezing-thawing method and the cast-drying method, which are physically crosslinked with hydrogen bonding but different in structure and mechanical properties. To evaluate these time dependent behaviors of load-support ratio of fluid/solid phases and friction, two-dimensional biphasic FE analysis for cylindrical PVA hydrogel cartilage as 1.5 mm thick soft layer and radius of 5 mm was conducted under continuous loading of 0.2 N/mm by impermeable rigid plate in reciprocating motion in Fig. 1. The sliding speed is 4 mm/s for stroke of 8 mm at period of 4 s. A commercial package ABAQUS (6.8–4), which was appropriately evaluated for the biphasic FE analyses, was used in this study. The biphasic tissue was modeled by CPE4RP (four-node bilinear displacement and pore pressure, reduced integration with hour glass control) elements. The mechanical properties such as permeability, Young's modulus and Poisson ratio were estimated by curve fitting to stress relaxation behaviors in compression test.

As indicated in Fig. 2, it is worth noting that the cast-drying PVA shows significant interstitial fluid pressurization compared with a repeated freezing-thawing PVA hydrogel at 292 s after start-up, where coefficient of friction for solid-to-solid was assumed as 0.2. Changes in friction for PVA hydrogels in reciprocating motion were estimated as shown in Fig. 3. In spite of high friction (0.2) for solid-to-solid, cast-drying PVA brought the gradual decreasing in friction, probably due to rising of load-support ratio by fluid phase from initial 74% to 80%.

In human body, lubricating constituents in synovial fluids such as hyaluronic acid, proteins, glycoproteins and phospholipids can reduce the coefficient of friction for solid-to-solid. As suggested for low coefficient of friction for solid-to-solid as 0.01 in Fig. 3, rubbing friction is expected to be reduced to significantly low level.

As described above, the effective biphasic lubrication can sustain low friction level and minimal wear in synergistic action with soft-elastohydrodynamic lubrication, hydration lubrication and boundary lubrication as a similar mechanism to natural cartilage in various daily activities. These results indicate the usefulness of artificial hydrogel cartilage for longer durability in joint prostheses for clinical application.

To evaluate the value of the use of massive prostheses in periprosthetic infections both in one stage and two stages procedures

Between 2008 and 2014, 236 revisions for PJI had been performed in our hospital by the same surgeon. For the most complex cases, we decided to introduce megaprostheses in our practice in 2011.

We report a prospective series of 33 infected patients treated between 2011 and the end of 2014, 14 male and 19 female with on average 67.9 years old (38–85) Infection involved TKA in 22 cases (17 TKA revisions, 4 primary TKA), THA in 9 cases (6 revisions, 3 primary THA), a femoral pseudo-arthrosis with posttraumatic gonarthrosis in one case and a septic humeral pseudoarthrosis in one case. We used a total femoral component for two patients: the first one for a hip PJI with extended diaphyseal bone loss and multiples sinus tracks, and the second one for a massive infected knee prosthesis used in a knee reconstruction for liposarcoma.

We used one stage procedures in 20 cases (8 hips, 12 knees, 1 shoulder) and two stages in 13 cases (12 knees and 1 hip). Additional technics included 3 massive extensor system allografts, two local flaps. Perioperative hyperbaric treatment was used for 2 patients.

The average follow up is 19.8 months (6–48 months). The most frequent complications were wound swelling and delayed healing in 8 cases;). In 3 cases of one stage surgery a complementary debridement was necessary in the three weeks after the surgery with always a good local and infectious evolution. VAC therapy was used in four cases with good results. We report one early postoperative dead.

In summary, the use of massive prostheses in PJI is a good option for complex cases. It can be a good alternative to knee arthrodesis. These components must be used preferentially for older patients, in cases of extreme bone loss or extensive osteomyelitis to secure the bone debridement and the quality of the reconstruction.

In our series, the one stage procedure is a validated option even by using complementary technics as bone allografts, extensor system allografts or flaps. We believe the two stages surgery is a secondary option, particularly when soft tissues status is compromised before or after the debridement, and mostly for the knees. The longevity of the implantation must be evaluate by a long term follow up.

Aims: The aim of this research activity is the synthesis and characterization of surface modified cobalt alloys, in order to obtain a biocompatible material presenting at the same time good wear performances, low metal ion release and low toxicity. It is of interest for hip and knee joints with metal-on-metal or metal-on-UHMWPE contacts. In the first case the main aim is to enhance the biocompatibily of the surface and to reduce the amount and the toxicity of the metal debris. In the second case the main aim is to reduce the amount of polymeric debris. The surface chemical composition of several implant cobalt alloys (as cast and forged alloys, low and high carbon alloys) was modified, producing relevant tantalum enrichment. Tantalum was chosen because of its low toxicity and high corrosion resistance. The employed process is of interest because it is low-cost and it does not involve the formation of a brittle ceramic coating.

Methods: The chemical composition and morphology (SEM-EDS), roughness (prophilometry), crystallographic structure (x-ray diffraction analysis) and wettability (contact angle) of the surface were characterized. The mechanical behavior of the modified materials was investigated by nanoindentations, scratch tests (Revetest), friction measurements and wear tests (pin-on-disc).

Results: A surface enrichment with tantalum was obtained through a thickness of several microns and the interface between the substrate and the modified layer is continuous and crack free. The maximum tantalum content on the surface is about 90 wt%. Scratch tests showed that the modified layer is well adherent to the substrate through a diffusion layer and its first detachment appeared at 55 N without any brittle or catastrophic event. The modified layer presented a higher wettability than the untreated one, with a contact angle of about 48° respect to 82°. The elastic modulus of the treated surface layer (nanoindentation tests) is 352 GPa, while it is 281 GPa in the untreated alloy and its hardness is 17 GPa while it is 8.6 GPa in the untreated one. The surface presents also a better wear resistance (0.7·10⁻⁶ respect to 5.7 10⁻⁶ mm³/ Nm) and lower friction coefficients (0.24 respect to 0.34) in the Me-on-Me contact, according to its higher hardness and wettability.

Conclusions: A surface with high tantalum content can be obtained by a low-cost process. It shows good mechanical properties (high elastic modulus, high hardness value, low friction coefficient, high wear resistance) and chemical properties (high wettability, good corrosion resistance). So it is of interest for joints presenting good biocompatibility and great longevity.

1. Experience with a refined type of implantable electrode for the myo-electric control of externally powered prostheses is reported.

2. The electrodes are externally energised by electromagnetic induction and therefore do not contain any battery cells. The myo-potentials are transmitted in frequency-modulated form and detected by a receiver placed on the skin. The implantable electrode, measuring 5x11x4 millimetres, is encapsulated in epoxy resin.

3. Six electrodes have been implanted in the forearms of two normal subjects and two below-elbow amputees. The time of implantation ranged from three to fifteen months. Macroscopically, a fibrous capsule developed around the electrodes. Histological examination showed a capsule of granulation tissue of varying thickness with slight inflammatory reaction and foreign-body giant cells.

4. In all cases except one the signals received have been of high quality as ascertained by conventional electromyography and frequency analysis. There has been no significant deterioration in signal quality during the follow-up periods.

5. The major source of failure was fatigue fracture of the gold wires making contact with the body tissues. In one case, however, the electrode was still functioning normally at the time of removal fifteen months after insertion.

6. The patients have not been inconvenienced either by the operative procedures or by the presence of the electrodes in the tissues.

Obviously these and other problems need much research, but the preliminary work already done is promising enough to indicate that a useful and dependable prosthesis could be developed to operate by the use of changes of muscle potential, and that such apparatus could be made light enough for practical use at the work-bench and in the home.

In addition to its orthopaedic interest, this case illustrates the special behaviour of fine particles of a synthetic material when implanted in the human body. These results may interest those engaged in the control of dusts in the plastics industry, for the inhalation of such dusts may well result in "implantation" of the material in the lung, with consequent histological changes.

Purpose of the study: Infection is the most severe orthopedic complication observed after conservative surgery. The purpose of this study was to ascertain the incidence and causes of such infection and analyze progress achieved over the last ten years.

Material and methods: From 1983 to 2004, surgical procedures were performed in more than 600 patients with bone sarcomas; 520 underwent reconstruction with a prosthesis and/or massive allow graft and were followed for at least six months. Age ranged from 4.5 to 82 years. Deep infections occurred in 47 patients requiring one or several revisions. Three other cases of infection, in patients initially given in other institutions, were included in the series. The study population thus included 50 deep infections after massive reconstruction. Forty-five of these patients had received chemotherapy and 20 radiotherapy. All patients were given adapted antibiotic therapy. Four patients required emergency amputation, and cleaning was attempted in 26. When the infection persisted, or when the infection became chronic, implanted material was removed systematically with insertion of an antibiotic-loaded spacer (gentamycin alon before 1990 then gentamycin+vancomycin). Reimplantation was attempted three to six weeks later when the laboratory results were satisfactory and the muscular and cutaneous situation was sufficient.

Results: Mean follow-up after infection was 8.5 years. At last follow-up, amputation had been necessary in 21 of the 50 patients. The limb was intact in the 29 others but the prosthesis could be reimplanted in only 27 after an average of 2.4 operations. The statistical analysis demonstrated that radiotherapy is a factor of poor prognosis (14 amputations in 20 radiotherapy patients versus 7 amputations in 30 patients without radiation) and that adjunction of vancomycin into the spacer cement has a beneficial effect (15 amputations in 23 patients without vancomycin versus 6 amputations in 27 patients with vancomycin.

Conclusion: Infection of a massive prosthesis is the most serious orthopedic complication because limb survival is compromised. Preventive treatment is crucial: radiotherapy should be avoided and duration of aplasia limited by the use of hematopoietic growth factors. Curative treatment can be achieved with early removal of implanted material, surgical cover with a muscle flap, and adjunction of vancomycin to the spacer cement. The role of prolonged systemic antibiotics remains controversial.

Introduction

Dislocation of an uncemented total hip replacement (THR) can cause damage to the femoral hear, when it passes through the rim of metal acetabular shell. This can lead to metal transfer on the surface of the head or chipping of bulk head material. Although dislocation is one of most common complications in total hip arthroplasty (THA), little is known if causes any further damage to the articulating surface of ceramic heads in long term observations.

Introduction: In an earlier publication we analysed short-term results of total hip arthroplasty (THA) with Ceramic-on-Ceramic (C-on-C) articulations, and we found that they did not perform better than the Charnley prosthesis with a metal-on-UHMWPE articulation.

Purpose: To examine mid-term results of THA with Con-C articulations, and to compare their results with the most commonly used cemented prosthesis in our register, the Charnley.

Materials and Methods: All THAs with C-on-C articulations were uncemented and they constituted 2506 THAs.

194 of the THAs had articulations with an Alumina liner and a femoral head made of a composite of Alumina and Zirconium oxide ceramic (Biolox delta). This group had a median follow-up of only 1.1 years, and the group was therefore not included in the survival analyses.

2312 of the THAs were uncemented prostheses with Alumina-on-Alumina articulations, with a follow-up of 0–11 years (median 4.3 years). For further analyses we included only patients under the age of 80 years (n = 2209).

We compared the two most common C-on-C cup/stem combinations: Igloo/Filler (n=1402) and Trilogy/SCP (n=363), and a group of others (n= 547). Further we compared the C-on-C prostheses with cemented Charnley prostheses in patients under the age of 80 years, operated during the same time-period. We also compared the C-on-C prostheses with Charnley prostheses in a group limited to patients under the age of 60 years. Prosthesis survival was estimated by Kaplan-Meier and Cox regression analyses adjusted for age and gender.

Results: In patients under the age of 80 years the Charnley prostheses had a statistically significant higher survival than the C-on-C prostheses at 7 years (97.1% and 95.7% respectively, p=0.04). In patients under 60 years of age these analyses gave similar results, although with no statistical significant difference between Charmley and the C-on-C prostheses (p=0.06). There was no statistically significant difference in revision risk among Igloo/Filler, Trilogy/SCP, and a group of all other combinations of cup/stem with a C-on-C articulation. The most common causes for revision of the C-on-C hips were dislocation (n=18) and deep infection (n=16). 3 were revised due to a broken liner and 4 due to a broken head. Of the 194 articulations with Alumina liner and Biolox delta head, one had been revised due to fractured head.

Conclusion: With a follow up of 0–11 years, we did not find superior results of the C-on-C prostheses compared to the Charnley prosthesis. Few revisions were clearly related to failure of the articulations.

The introduction of ceramics in total hip arthroplasty contributed significantly to the wear reduction of poly-ethylene and in consequence reduced osteolysis and loosening. This great benefit has been demonstrated in several clinical observations. In a recent study from Norway, the wear of a 28mm alumina and a CrCo ball head against Ultra High Molecular Weight Polyethylene (UHMWPE) after 10 years is compared using the RSA method of wear measurement.

It was concluded that the considerable reduced wear for ceramic ball heads in comparison to CrCo ball heads is a great advantage in hip arthroplasty.

A first prospective, randomized study with a 15 years follow up has been presented recently in the EFORT 2009. The comparison of wear of polyethylene between alumina and metal ball head shows a reduction of 44% penetration (linear wear) with the alumina-polyethylene bearing surface. In order to offer improved mechanical resistance and tribological qualities than alumina whilst maintaining structural stability, a new generation of alumina matrix composite (BIOLOX^®delta) has been used in orthopedics since 2001. The topic of this study is to demonstrate the excellent wear performance of the alumina ceramic composite against polyethylene, compared to alumina/PE in vivo.

Methods: The BIOLOX^®delta-PE bearing has been tested on a six station hip simulator (Endolob, Rosenheim) according to ISO/DIS 14242. The newborn calf serum was replaced every 0.5 million cycles and the test was stopped after 5 million cycles. Weight was measured using a high precision balance (Sartorius BP 211D)

Results and Discussion: After 5 million cycles, the insert surface appeared polished with fine scratching on the whole contact area. The wear rates calculated by linear interpolation were 13,52 mg per million cycles. (Standard deviation 0,60). The wear rate measured for BIOLOX^®delta against UHMWPE was 13,52 mg per million cycles.

In general, the wear rate can be regarded as small compared to other hip simulator tests using ceramic against polyethylene couplings. When comparing the results for BIOLOX^®forte on polyethylene with the same 28mm diameter and same testing parameter, we observed 26,57 +/− 3,55mg/million and 16,08+/−2,31 mg/million, respectively. The BIOLOX^®delta on UHMWPE bearing shows improved wear behavior with a much lower wear rate.

Conclusion: This study demonstrates the very low in vitro wear of the Alumina ceramic composite on UHMPE compared to ball heads made of pure alumina. Based on this results and the clinical performance of the alumina-UHMPE bearing from the literature, we can expect a further reduction of wear for the BIOLOX^®delta on UHMWPE in vivo that will increase the survival rate of the total hip arthroplasty.

Various treatments for ultra-high molecular polyethylene (UHMWPE) such as cross-linking, addition of vitamin E and the grafting of phospholipid polymer improved the wear properties. However, wear problems still occur in joint prostheses in mixed or boundary lubrication modes under severe conditions. As an alternate method, the joint prosthesis with artificial hydrogel cartilage with similar properties to articular cartilage is expected to show superior tribological functions with very low friction and low wear if the adaptive multimode lubrication mechanism is actualized. In this study, the effectiveness of hydrogel structure and adsorbed film formed on artificial cartilage surfaces is examined in reciprocating tests in related to biphasic, hydration and boundary lubrication modes.

The frictional behaviors of artificial cartilage materials against flat glass plate in the reciprocating test were observed. As upper specimens, poly(vinyl alcohol) (PVA) hydrogel ellipsoidal specimen as 2 mm soft layer were prepared. PVA hydrogel specimens were prepared by the repeated freezing-thawing method and the cast-drying method. The sliding speed and stroke length were 20 mm/s and 35 mm, respectively. Applied load was 2.94 N or 9.8 N. The lubricants are saline or saline solutions containing L-α-Dipalmitoyl phosphatidyl-choline (DPPC), serum protein and/or hyaluronate(HA).

As shown in Fig. 1, the repeated freezing-thawing PVA shows gradual increase in friction from initial medium value immediately after loading of 2.94 N to high level. For the same test condition, the articular cartilage exhibited similar time-dependent frictional behavior from initial lower friction to high level as estimated by biphasic lubrication theory. On the contrary, it is noticed that a low friction is maintained for cast-drying PVA hydrogel, particularly two-layer laminated PVA hydrogel until 140 m sliding. The improvement of frictional behaviors in cast-drying PVA hydrogel is considered to have been brought about by the improvement of water retention ability of the hydrogel with uniform microstructure controlled by hydrogen bond.

Next, the influence of lubricant constituents on tribological behaviors of freezing-thawing PVA hydrogel was examined in repeated reciprocating test including unloading-restarting process at each 36 m sliding at 9.8 N. The frictional behavior for the freezing-thawing PVA hydrogel could be improved with supplying appropriate lubricant constituents as shown in Fig. 2. In lubricated condition with HA solution containing 0.01 wt% DPPC, 1.4 wt% albumin and 0.7 wt% γ-globulin, low friction was maintained and very little visible wear was confirmed in micrograph. Adsorbed films appear to contribute to the effective synergistic lubrication even under high load of 9.8 N in reciprocating test.

As described above, the effectiveness of synergistic lubrication for PVA hydrogel specimens is shown for improvement of tribological behaviors of artificial cartilage as a superior mechanism to natural cartilage. These results indicate the possibility of artificial hydrogel cartilage for longer durability in joint prostheses for clinical application.

Introduction

Ten explanted pyrolytic carbon components of a number of finger prostheses were obtained at revision surgery for wear analysis. Implants were removed for either dislocation or failure of fixation. Hypothesis Failure of the components was due to wear from the articulating surfaces, as occurs in many hip and knee prostheses.

Introduction: One of the latest groups of replacement hip joints are known as hip resurfacings and they consist of a relatively large diameter femoral head articulating within a thin acetabular cup. Many of these devices show good short to medium term clinical results. However there are concerns over such implants including fracture of the femur and possible wear debris related reactions. Much valuable data can be learnt from explanted prostheses which have ‘failed’ and then been removed from patients. As hip resurfacing prostheses have only recently been introduced, there are relatively few such retrieval studies.

Methods and materials: Nineteen femoral and acetabular components from metal-on-metal hip resurfacing prostheses were obtained at revision operations. There were eight patients who had femoral fractures and the remainder experienced worsening groin pain and a characteristic sterile effusion. There were eleven head components and four pairs of matching heads and cups. Each of these was examined using a Zeiss TSK Rond-com60A roundness measuring machine and a Mitutoyo LEGEX co-ordinate measuring machine (CMM). Out of roundness measurements were taken on three planes for each acetabular and femoral component. The CMM was used to obtain 12 traces at 30° intervals for each acetabular and femoral component, allowing areas of localised wear to be identified and the maximum wear depth to be quantified.

Results: The maximum out of roundness values for the nineteen components ranged from 1.8 to 91.8 microns. A similar range of values was obtained from the CMM results. From the paired components, out of roundness was greater in the head than in the cup. All eight femoral heads which were retrieved after fracture of the femur showed out of roundness of less than 5 microns.

Discussion: Both out of roundness measurements and those from the CMM provided information about the wear of the implants. For a new component, a typical out of roundness value would be no greater than 5 microns. Therefore, from the out of roundness values it was seen that the eight ‘fracture’ components showed minimal distortion or wear after removal. In contrast the remaining components, which had a minimum out of roundness of 15 microns, showed much greater wear, thus suggesting that the groin pain was associated with relatively large volumes of wear debris. CMM scans helped to identify localised areas of wear and maximum wear depths. Values in the range of < 2 microns to 164 microns have been reported previously and show good agreement with the findings of this study. Retrieved components which had been implanted at high angles of inclination and anteversion tended to show the greatest wear, implying that correct positioning in vivo is crucial to the longevity of hip resurfacing prostheses.

Introduction and Aims: Aim of the study is to show whether the accuracy of alignment of a total knee pros-thesis is more dependent on the instrumentation or the skills of the surgeon.

Method: Forty patients that had total knee arthroplasties performed between September 1997 and September 1999 have been analysed. The results of prospective randomised trial using the LCS (Depuy) and IBII (Zimmer) prostheses have been analysed, as well as results using the Scorpio (Stryker) and Profix (Smith + Nephew) total knee replacement systems. Patients were evaluated according to a radiographic protocol, a modification of the Knee Society total knee arthroplasty x-ray evaluation and scoring system. All patients had long leg standing x-rays in full extension and neutral rotation. Lateral x-rays were taken in neutral rotation with a maximum of 10 degrees of flexion. The femoral varus/valgus alignment is recorded on the AP x-ray as the Alpha angle, and the tibial alignment as the Beta angle. On the lateral x-ray the Gamma angle records the femoral flexion and the Theta angle the tibial prosthesis alignment along the tibial shaft.

Results: The results were statistically analysed by the Department of Statistics at the University. Results were stratified according to both the instrumentation used and the surgeon. These showed that there was no statistical difference between the alignment of the different prostheses, irrespective of the surgeon performing the procedure.

Conclusion: From this study we concluded that no one set of instrumentation used while performing a total knee replacement was superior to another. As long the surgeon is familiar with the instrumentation the final alignment of the prosthesis will be satisfactory.

Introduction and purpose: Infections of total hip prostheses are one of the most serious complications that beset this procedure. Their incidence in the world literature is of 1%. However this figure rises to 16% in the case of implants secondary to fractures in patients with multiple pathologies. In this study we conduct a descriptive analysis of the qualitative variables after the implementation of an action protocol to address this complication.

Materials and methods: A consecutive series of 694 patients was studied (420 females, 60.52%, and 274 males, 39.48%). Out of these 233 cases were secondary to fractures ( 60 males and 173 females), which meant that treatment was administered as an emergency (in the first 48 hours), and 461 were primary (241 males and 247 females). The variables related to an infection risk were studied, a distinction being made between an acute and a chronic infection based on CCD criteria. In acute cases, surgical cleaning was performed; in subacute cases, a two-stage replacement was chosen and for chronic infections we performed a resection arthroplasty if the two-stage replacement failed.

Results: We performed a frequency and exponential chi square study which yielded 37 cases (5.33%) of implant infection (11 males, 26 females).The most frequently isolated germ was Staphilococus Aureus. 74% of cases treated with surgical cleaning after a diagnosis of acute infection are now infection-free after a two-year follow-up. 60% of subacute cases, where a two-stage replacement was performed, show a satisfactory result. As regards resection arthroplasty, the success of treatment was around 92%,with a p< 0.005 value.

Conclusions: Careful patient selection and early diagnosis are fundamental to obtain good results in the treatment of THP infections.

The common factor in all (mechanical) prosthetic failure mechanisms is the induction of osteolysis around the endoprosthesis with subsequent prosthetic migration and finally loosening of the prosthesis. Both initial prosthesis-bone fixation and long-term prosthesis survival depend on the quality of the peri-prosthetic bone mass. The effects of treatment of RA patients with prednison are inhibition of osteoblastic activity and inhibition of calcium resorption from the intestines. The bone mass loss during the first six months of prednison treatment is substantial and will seldom be regained. Bisphosphonates are known to decrease osteoclastic activity and may therefore stop osteolysis at the bone-prosthesis interface.

The aim of the study was to evaluate a possible association of bisphosphonates with reduced migration of total knee prostheses (Interax, Howmedica Osteonics, Rutherfort, USA) in a high-risk group. Roentgen Stereophotogrammetric Analysis (RSA-CMS, Medis, The Netherlands) was used to measure the micromotion.

Retrospectively a group of nine RA patients treated with prednison (non-bisphosphonates group) and a group of fourteen RA patients (bisphosphonates group) treated with prednison in combination with bisphosphonates (Etidronate) were included from a prospective randomized study of 82 patients (Nelissen et al., 1998).

At the two-year follow-up evaluation, functional scores and knee scores did not differ significantly among the two groups. At the two-year follow-up evaluation, the non-bisphosphonates group subsided −0.47 ± 0.8 mm, and the bisphosphonates components subsided 0.07 ± 2.9 mm. In the analysis of variance with repeated measurements, with correction for follow-up time, sedimentation rate, and prosthesis fixation type, the bisphosphonates group migrated 1.20 mm less in the total migration (95% c.i.: 1.07–1.30 mm) compared to the non-bisphosphonates group.

In this study, bisphosphonates medication in addition to corticosteroid medication was associated with reduced migration of knee prostheses compared to corticosteroid medication alone.

The stem of a femoral component can be helpful in assuring proper implant orientation. However, recent interest in short femoral components with which to better accommodate smaller incisions has resulted in technical challenges to proper implant positioning. In order to avoid component malposition and potential compromise of implant longevity, surgeons may rely upon intra-operative x-rays. However this has major drawbacks: radiation exposure of the OR staff; and accommodation of x-ray equipment without compromise of operating field sterility.

There has been created a simple, precise instrument which will ensure proper implant positioning in varus/valgus and flexion/extension planes without the need of intra-operative x-ray. Its reliability has been confirmed by both cadaveric and clinical studies. It has been demonstrated to be 100% accurate in providing proper short femoral component positioning.

Wear debris induced osteolysis is a recognized complication in conventional metal-on-polyethylene hip arthroplasty. One method of achieving wear reduction is through the use of metal-on-metal articulations. One of the latest manifestations of this biomaterial combination is in designs of hip resurfacing which are aimed at younger, more active patients. But, do these metal-on-metal hip resurfacings show low wear when implanted into patients?

Using a Mitutoyo Legex 322 co-ordinate measuring machine (scanning accuracy less than 1 micron) and a bespoke computer program, volumetric wear measurements for retrieved Articular Surface Replacements (ASR, DePuy) metal-on-metal hip resurfacings were undertaken. Measurements were validated against gravimetric calculations for volumetric wear using a sample femoral head that was artificially worn in vitro. At 5mm3, 10mm3, and 15mm3 of material removal, the method was shown to be accurate to within 0.5mm3.

Thirty-two femoral heads and twenty-two acetabular cups were measured. Acetabular cups exhibited mean volumetric wear of 29.00mm3 (range 1.35 - 109.72mm3) and a wear rate of 11.02mm3/year (range 0.30 - 63.59mm3/year). Femoral heads exhibited mean wear of 22.41mm3 (range 0.72 - 134.22mm3) and a wear rate of 8.72mm3/year (range 0.21 - 31.91mm3/year). In the 22 cases where both head and cup from the same prosthesis were available, mean total wear rates of 21.66mm3/year (range 0.51 - 95.50mm3/year) were observed.

Revision was necessitated by one of five effects; early femoral neck fracture (4 heads), avascular necrosis (AVN) (2 heads, 1 cup), infection (1 head, 1 cup), adverse reaction to metal debris (ARMD) (19 heads, 18 cups) or ARMD fracture (6 heads, 2 cups). Mean paired wear rates for the AVN and infection retrievals were 0.51mm3/year and 3.98mm3/year respectively. In vitro tests typically offer wear rates for metal-on-metal devices in the region of 2-4mm3.

Mean paired wear rates for ARMD and ARMD fracture were 17.64mm3/year and 68.5mm3/year respectively, significantly greater than those expected from in vitro tests. In the 4 cases of early fracture, only the heads were revised so a combined wear rate calculation was not possible. The heads exhibited mean wear rate of 8.26mm3/year. These high wear rates are of concern.

Purpose: The purpose of our work was to report causes and results of treatment of anterior shoulder instability after implantation of a shoulder prosthesis.

Material and methods: This retrospective multicentric study included 51 patients with prosthetic anterior instability: 42 patients after first-intention shoulder prosthesis and nine after prosthesis revision. There were 39 women (79%) and 12 men, mean age 67 years, who underwent total shoulder arthroplasty (n=29, 57%) or hemiarthro-plasty (n=22, 43%). Thirty-eight patients (75%) had prosthetic dislocation and 13 (25%) subluxation associated with pain an loss of anterior elevation. The initial prosthesis was implanted for degenerative disease (n=29), rheumatoid arthritis (n=7), or fracture (n=15). Anterior prosthetic instability occurred early in 23 shoulders (first six weeks) and lat in 28 shoulders (7 after trauma, 21 without trauma). Conservative treatment by reduction-immobilisation was performed in 16 cases and prosthetic revision in 35. The patients were reviewed radiographically at mean 41 months follow-up (range 24–62).

Results: Subscapular tear or incompetence was the main cause of prosthetic anterior instability, observed in 87% of the cases. Technical errors concerning the prosthesis were also observed: oversized head, malrotation of the prosthesis. Associated complications were frequent: glenoid loosening (24%), polyethylene dissociation from the metal glenoid implant (10%), infection (10%), humeral fracture (4%). The final Constant score was 54 points and 55% of the patients were disappointed or dissatisfied. None of the shoulders were stable after consevative treatment. The prosthetic revision provided disappointing results with 51% recurrent anterior instability.

Discussion: Anterior instability of shoulder prostheses is a serious complication which responds poorly to treatment. Loosening of the subscapular suture is the main cause.

Prosthetic radial head replacement is usually performed for trauma or post traumatic reconstruction. Therefore pain caused by a loose prosthesis might be incorrectly attributed to other causes. We lack reliable guidelines for diagnosing a loose radial head prosthesis that is symptomatic. Experience in Hip Arthroplasty has identified thigh pain as originating from the bone-prosthesis interface in the femoral canal, as opposed to the acetabulum or hip joint itself. The authors have recognized a similar phenomenon with radial head prostheses that has not yet been reported in the literature. Pain from a loose stem within the proximal radius may present as forearm pain.

The medical records and radiographs of 14 consecutive cases (13 patients) with proximal radial forearm pain associated with a loose radial head prosthesis were reviewed retrospectively. From August 1999 to December 2006, 9 consecutive patients (10 cases) required revision surgery for painful aseptic loosening of a primary metal prosthetic radial head implant. One of the 9 patients required re-revision with a longer stem. A further 4 patients with symptomatic aseptic loosening have not yet been revised. The indication for revision surgery was painful loosening of the prosthesis within the canal of the proximal radius in 7 patients (8 cases) and pain with no evidence of loosening in 2 patients (2 cases). Various prosthetic designs had been used in the primary operations.

In 12 of 14 cases the loosening was evident radiographically, but in 2 the only indication of a loose prosthesis (confirmed surgically) was proximal forearm pain. Revision or prosthetic removal eliminated the pain in 7 of 10 cases and decreased it in 1 Most of the patients who had relief of their forearm pain could tell in the first few days that the pain was gone following revision or removal of the loose radial head prosthetic component. One patient with moderate pain had an arthritic elbow and had no significant lasting relief from surgery. One patient was lost to follow-up. Follow-up averaged 27 months (range 1 to 66 months). Three of the 4 patients who had not yet undergone revision, were still awaiting revision and one did not want further surgery.

In conclusion, the presence of radial sided proximal forearm pain in a patient with a radial head prosthesis is a strong indicator of symptomatic aseptic loosening. If the prosthesis has a textured surface for bone ingrowth, and was inserted without cement, we now consider this symptom to be diagnostic even in the absence of radiographic signs of loosening.

Aim

To investigate the effectiveness of silver coated prostheses in preventing periprosthetic infection in a high-risk group.

The role of matrix metalloproteinases (MMPs) in the aseptic loosening of hip prostheses is well established. Gelatinase MMPs have been identified in the interface membranes and the pseudosynovial tissues in the hips. Little data are available on gelatinase MMPs and their major regulators, including specific tissue inhibitors of matrix metalloproteinases (TIMPs) in the loosening of shoulder prostheses. The objectives of this study were to determine whether A) gelatinase MMPs and their regulators (MMP14, TIMP-1,-2) are produced by periprosthetic tissues in cases of aseptic loosening of shoulder prostheses, and, B) to identify which cell types, in both interface and synovial tissues, localize the enzymes.

Interface tissues and synovial tissues were obtained during revision surgery for loose shoulder implants. In 9 patients (6-Total Shoulder Replacement, 3-Hemiarthro-plasty (Bipolar), 9 samples of interface tissues and 8 samples of synovial tissues were obtained. Of the interface tissues 2 were from the interface of the bipolar and the unresurfaced glenoid. Formalin-fixed paraffin embedded sections were stained using primary antibodies for MMP2 (Neomarkers), MMP9 (Oncogene Ltd), TIMP1, TIMP2 & MMP14 (Chemicon Ltd). Antigen retrieval required pressure cooker treatment for MMP2 and MMP9 and trypsin for TIMP1. Visualisation used a standard DAB chromagen technique (Envision, Dako Ltd.). Appropriate control sections ensured reproducibility of the staining. The antibodies selected bind to both active and inactive forms of the MMPs.

Both HDPE and metal debris were seen in both the synovial and interface tissues. Transformation of macrophages to giant cells was associated with PE debris, and was not observed with metal debris alone.

The presence of gelatinase MMPs in both interface and synovial tissues in aseptic loosening of shoulder prostheses was demonstrated. Differences between the MMP content of macrophages and giant cells between the tissues was detected, positivity was associated with the presence of metallic and/or HDPE debris. Activation of endothelial MMP2 by both MMP14 and low levels of TIMP2 would support the development of a vascular network.

Aim: To calculate the incidence and timing of metal failure in endoprostheses used for bone tumour reconstructions and to analyse the mode of failure.

Methods: A retrospective analysis was performed on 468 endoprostheses with an average follow-up of 50 months. The explanted prostheses were studied to determine the mode of failure and the design and material features that might have contributed to the failure.

Results: There were 18 mechanical failures of metal. A total of 19 cases were revised for loosening one of which was noted to have a metal fracture pending at the time of the revision. There were three cases of failure of the coupling between components of modular systems. All of the remaining cases (16) were in the lower limb and these failed by fracture of the metal. The fractures occurred at an average of 92 months. The majority of the fractures that were seen were simple fatigue fractures but in three cases other types of failure were also involved. There were no fatigue fractures in forged cobalt chrome components. Fatigue fracture of the cast cobalt chrome implants could always be attributed to a local stress riser or a local area of high stress due to features of the design. Fatigue fractures of titanium implants were often related to notching.

Discussion: The large skeletal defects left by resection of bone tumours can often be reconstructed with endo-prostheses. The mechanical demands on these implants are great resulting in a relatively high incidence of metal failure. Improvements in design and materials can minimise these failures.

Introduction

Total knee arthroplasty (TKA) prostheses are semi-constrained artificial joints. Femorotibial constraint is a key property of a TKA prosthesis and should be designed to match the device's intended function. Cruciate Retaining (CR) prostheses are usually used for patients with a functioning posterior cruciate ligament (PCL). For patients without a fully functioning PCL, CR-Constrained (CRC) prostheses may be used. A CRC tibial insert usually has a more conforming sagittal profile especially in the anterior aspect to provide increased constraint to prevent paradoxical femoral translation during knee flexion. A quantitative understanding of the constraint behavior of a prosthesis design is critical to ensure its functional outcome. Using a validated computer simulation, this study evaluated the anterior-posterior (AP) constraint of two types of tibial inserts (CR and CRC) from a same TKA product family.

Introduction

Fretting corrosion at the Head-Neck taper interface of Large Metal on Metal (MoM), Metal on Polymer (MoP) and Ceramic on Ceramic (CoC) total hip arthroplasty (THA) remains a clinical concern. Ceramic femoral heads have gained a lot of attention more recently as a possible way to mitigate/reduce the dissolution of Cobalt Chromium ions. The objective of this study is to assess the fretting corrosion currents emanating from four material combinations for which Ti6Al4V and Co28Cr6Mo are the neck components of Co28Cr6Mo and BIOLOX®delta femoral heads at three different cyclic loads.

We studied the detection of joint replacements at airport security checks in relation to their weight, using two types of detector arch. A single-source, unilateral detector showed different sensitivities for implants on different sides of a test subject.

All implants weighing more than 145 g were detected by one of the arches. The degree of detection was directly related to the logarithm of the weight of the prosthesis in patients, with a linear correlation (r² = 0.61). A bilateral arch detected all prostheses weighing over 195 g.

With their usual sensitivity settings many joint replacements were detectable; an identification pass containing the site and weight of such prostheses would help to avoid the need for body-search procedures.