Summary Statement. Femorotibial constraint is a key property of a total knee arthroplasty (TKA) prosthesis and should reflect the intended function of the device. With a validated simulation methodology, this study evaluated the constraint of two TKA prostheses designed for different intentions. Introduction. TKA prostheses are semi-constrained artificial joints. Femorotibial constraint level is a major property of a prosthesis and should be designed to match the device's intended function. Cruciate Retaining (CR) prostheses are usually indicated for patients with a functioning posterior cruciate ligament (PCL). For patients without a fully functioning PCL, CR-Constrained (CRC) prostheses with additional built-in constraint may be indicated. A CRC prosthesis usually consists of a CR femoral component and a tibial insert which has a more conforming sagittal profile to offer an increased femorotibial constraint. This study evaluated the anterior-posterior (AP) constraint behavior of two lines of prostheses (CR and CRC) from a same TKA product family. Using a validated computer simulation approach, multiple sizes of each product line were evaluated. Methods. Both the CR and CRC prostheses are from the same TKA product family (Optetrak Logic, Exactech, FL, USA) and share identical femoral components and tibial baseplates. The CRC tibial inserts have a more conforming sagittal profile than the CR tibial inserts, especially in the anterior aspect. Three sizes (sizes 1, 3, and 5) from each product line were included in this study. Computer simulations using finite element analysis (FEA) were performed to evaluate the femorotibial constraint of each prosthesis per ASTM F1223 standard [1]. The simulation has been validated by comparison with physical testing (more details submitted in a separate paper to CORS 2013). Briefly, FEA models were created using 10-node tetrahedral elements with all materials considered linear elastic. The tibial baseplate was distally fixed and a constant compressive force (710 N) was applied to the femoral component. Nonlinear Surface-Surface-Contact was established at the articulating surfaces, as well as between the tibial insert and the tibial baseplate. A coefficient of friction of 0.1 was assumed for all articulations [2]. The femoral component was driven under a displacement-controlled scheme to slide along AP direction on the tibial insert. Constraint force occurring at the articulation was derived from the reaction force at the distal fixation; thus, the force-displacement curve can be plotted to characterise the constraint behavior of the prosthesis. A nonlinear FEA solver (NX Nastran SOL601, Siemens, TX, USA) was used to solve the simulations. Results. The force-displacement curves predicted by the simulation exhibited the hysteresis loop appearance for both CR and CRC prostheses. The profile of the curves was generally consistent across different sizes for both product lines. The anterior constraint of the CRC prosthesis was significantly greater than the CR prosthesis. The posterior constraint of the CRC prosthesis was also slightly greater. Larger sizes exhibited reduced constraint compared to smaller sizes. Discussion/Conclusion. The increased constraint of the CRC prosthesis revealed in the study is consistent with the geometrical characteristics and the functional intent of the device. The CRC tibial insert is expected to provide significantly greater anterior constraint than the CR prosthesis to prevent paradoxical femoral translation when the patient's PCL is not fully functioning. The CRC tibial insert is also expected to provide slightly increased posterior constraint due to its elevated posterior lip. The observed hysteresis loop appearance is consistent with physical testing and the existence of friction. The reduced constraint on larger sizes is functionally desirable to offer proportional translation freedom. This study demonstrated the effectiveness of the simulation approach in quantifying the constraint behavior of different TKA prosthesis designs

The metal on metal implants was introduced without the proper stepwise introduction. The ASR resurfacing hip arthroplasty (RHA) withdrawn due to high clinical failure rates and the large diameter head THA (LDH-THA) are also widely abandoned. Early (2 year) radiostereometry studies does not support early instability as cause of failure but more likely metal wear products. A possible advantage may be maintenance of bone mineral density (BMD). We present 5 year prospective follow up from a randomized series, aiming to report changes from baseline and to investigate links between implant micromotion, Cr & Co ions and BMD. Patients eligible for an artificial hip were randomized to RHA, Biomet LDH-THA or standard Biometric THA. 19, 17 and 15 patients completed 5 year follow-up. All followed with BMD of the femur, acetabulum and for RHA the collum. RHA and THA with whole blood Co and Co. LDH-THA only at 5 year. RHA had marker based RSA of both components, cup only for LDH-THA. Translations were compiled to total translation (TT= √(x. 2. +y. 2. +z. 2. )). Data were collected at baseline, 8 weeks, 6 months, 1, 2 and 5 years. Statistical tests: ANCOVA for TT movement, Spearman's correlation for BMD, Cr, Co and BMI to TT at 5 years. RSA: The 5 year median (25%to75%) RHA cup translations were X=-0.00(−0.49 to 0.19) Y=0.15(−0.03 to 0.20), z=0.24(−0.42 to 0.37) and TT 0.58 (0.16 to 1.82) mm. For the LDH-THA X=−0.33(−0.90 to 0.20) Y=0.28(0.02 to 0.54), z=0.43(−1.12 to −0.19) and TT 1.06 (0.97 to 1.72) mm. The TT was statistically different (p<0.05) for the two cups. The RHA femoral component moved X=0.37(0.21 to 0.56) Y=0.02(−0.07 to 0.11), z=-0.01(−0.07 to 0.26) and TT 0.48 (0.29 to 0.60) mm at 5 years. There was no TT movement from year 2. The mean (SD) acetabular BMD was diminished to 93(90–97)% for RHA and 97(93–99.9)% for THA, but LDH-THA maintained 99(95–103)%. Overall femoral BMD was unchanged at 5 years for all interventions, but both stemmed implants lost 17% at the calcar. Median (25%to75%) whole-blood Cr peaked in the LDH-THA group with 1.7 (0.9 to 3.1) followed by RHA 1.2 (0.8 to 5.0) and THA with 0.5 (0.4 to 0.7)ppb. For Co the highest levels were found in RHA with 1.6(0.8 to 4.7) followed by LDH-THA 1.2 (0.7–1.7) and THA 0.2 (0.2 to 0.6) ppb. The only correlations above +/−0.3 for TT were the RHA femoral component with a correlation of 0.47 to BMI, 0.30 to Co and Cr. The ASR cup conversely had a negative correlation of −0.60 to BMI and again, the LDH-THA cup had a negative correlation of −0.37 to Cr. In contrast to registered revision rates, we found significantly larger movement for the Biomet cup than the ASR cup. The metal ion levels were similar. The LDH-THA cup maintained the acetabular BMD best at 5 years, but the difference was small, we are limited by small numbers and the correlations between TT and the covariates showed no clear pattern

Purpose. To compare postoperative clinical outcomes between posterior cruciate ligament (PCL) retaining and resecting total knee arthroplasty (TKA) using same cruciate-substituting (CS) inserts, and to elucidate the clinical relevance of the residual PCL in cruciate-retaining TKA, considering intraoperative influence factors, such as the posterior tibial slope, posterior condylar offset, joint gap, joint balance, and joint laxity. Methods. A total of 64 consecutive knees (44 patients) were enrolled in this study and divided into following two groups: 39 knees underwent PCL-retaining TKA group (CR group), and 25 underwent PCL-resecting TKA group (CS group). Preoperative patients’ demographic data and one-year postoperative clinical outcomes including range of motion, the Knee Injury and Osteoarthritis Outcome Score (KOOS), the Japanese Orthopaedic Association (JOA) score, and Forgotten Joint Score-12 (FJS-12) were compared between two groups. Results. Regarding range of motion, the average preoperative ROM was -14.3/120.0 degrees in the CR group and improved to -2.4/118.9 degrees postoperatively. In the CS group, the average preoperative ROM was -7.5/130 degrees and changed to -2.2/122.4 degrees postoperatively. There was no significant difference in the postoperative ROM between the groups (P=0.16). The KOOS (from 47.1 to 69.5 in CR group; from 41.1 to 70.8 in CS group) and JOA scores (from 59.2 to 76.9 in CR group; from 55.6 to 80.8 in CS group) were significantly improved postoperatively in both groups (P < 0.01). However, there was no significance in these postoperative scores between two groups (P = 0.09). There was also no significance in FJS-12 between two groups (70.3 in CR group and 66.9 in CS group; P=0.53). Conclusions. Residual PCL in TKA with a CS insert would not impact one-year postoperative clinical outcomes including KOOS, JOA, and FJS-12

The purpose of the study was to compare the mechanical properties, oxidation and wear resistance of a vitamin E blended and moderately crosslinked polyethylene for total knee arthroplasty (MXE) in comparison with clinically established polyethylene materials. The following polyethylene materials were tested: CPE (30 kGy e-beam sterilized), XLPE (75 kGy gamma crosslinked @ 100°C), ViXLPE (0.1 % vitamin E blended, 80 kGy e-beam crosslinked @ 100°C), and MXE (0.1 % vitamin E blended polyethylene, 30 kGy gamma sterilized). For the different tests, the polyethylene materials were either unaged or artificially aged for two or six weeks according to ASTM F2003-02. The oxidation index was measured based on ASTM F2102 at a 1 mm depth. Small punch testing was performed based on ASTM F2977. Mechanical properties were measured on unaged materials according to ASTM D638. Wear simulation was performed on a load controlled 3 + 1 station knee wear simulator (EndoLab GmbH, Thansau, Germany) capable of reproducing loads and movement of highly demanding activities (HDA) as well as ISO 14243-1 load profiles. The load profiles were applied for 5 million cycles (mc) or delamination of the polyethylene components. Medium size AS e.motion. ®. PS Pro (Aesculap AG, Tuttlingen, Germany) femoral and tibial components with a ZrN-multilayer surface, as well as Columbus. ®. CR cobalt-chrome alloy femoral and tibial components were tested. Particle analysis was performed on the serum samples of the ISO 14243-1 wear simulations based on ISO 17853:2011 and ASTM F1877. The analysis of the mechanical properties show that moderately crosslinked polyethylene (MXE) might be a superior material for total knee arthroplasty applications [Schwiesau et al. 2021]. The addition of vitamin E in a moderately crosslinked polyethylene prevented its oxidation, kept its mechanical characteristics, and maintained a low wear, even under a HDA knee wear simulation

Bi-cruciate stabilized (BCS) TKA is the prosthesis that aims to substitute bi-cruciate ligament with post-cam engagement. We estimated to describe the in vivo kinematics during deep knee bending in BCS and Cruciate retaining (CR) TKA with the same articular geometry. We analyzed 26 knees who agreed to the current investigation under institutional review board approval. 17 knees were implanted with BCS (Journey ∥BCS, Smith & Nephew. Memphis, US) and 9 knees with CR (Journey∥CR). Each patient was asked to perform deep knee bending under weight-bearing condition. To estimate the spatial position and orientation of the TKA, 2D/3D registration technique with single fluoroscopy was used. We evaluated anteroposterior (AP) translation of the nearest point from femoral component to tibial axial plane for medial and lateral sides, femoral external rotation relative to tibial component and post-cam engagement in BCS. Measurement results were analyzed using Wilcoxon test. Values of P<0.05 were considered statistically significant. Medial AP translation indicated 11.7±5.1% posterior movement in BCS and 4.0±6.6% anterior movement in CR from minimum flexion to 130°. Lateral AP translation indicated 28.9±11.4% posterior movement in BCS and 18.3±6.2% posterior movement in CR from minimum flexion to 130°. Femoral external rotation were observed in both group and the amount of rotation were 5.2°±4.5° in BCS and 8.2°±4.0° in CR. Anterior post-cam engagement was not observed in all cases (76.5%). But medial AP translation in BCS was anteriorly in shallow flexion angles compared to CR. It suggested that anterior post-cam engagement couldn't work in valid

Introduction

Intervertebral disc degeneration (IDD) is a progressive process affecting all disc tissues, namely the nucleus pulposus (NP), annulus fibrosus (AF), and cartilaginous endplates (CEPs). Several cell-based therapies have been proposed to replenish the disc cell population and promote tissue regeneration. However, cell-free therapeutics have been increasingly explored due to potentially higher advantages and cost-effectiveness compared to cell transplantation. Recently, extracellular vesicles (EVs) isolated from healthy Tie2⁺-NP cells (NPCs) have shown promising regenerative outcomes on degenerative NPCs (dNPCs). The aim of this study was to assess the effect of such EVs on all disc cell types, including AF cells (AFCs) and CEP cells (CEPCs), compared to EVs isolated from bone-marrow derived mesenchymal stromal cells (BM-MSCs).

Tenocytes from several mammal species have been shown to be prone to phenotypic drift at early sub-culture passages. In the present study we compared allogenic and xenogenic serum supplementation suitability as a supplement for the in vitro expansion of equine tenocytes (eTCs), in combination with the presence or absence of crowding conditions. eTCs were isolated from superficial digital flexor tendon and expanded in normal growth medium containing DMEM, 10% appropriate serum, 1% penicillin/streptomycin solution. Isolation was performed by migration method in growth medium containing the selected serum. Silver staining, densitometry, zymography, immunofluorescence, metabolic activity, proliferation, viability and morphology were performed after 3, 5 and 7 days in culture with a seeding density of 10,000 cells/cm2. Treatment conditions were equine serum (ES) or foetal bovine serum (FBS), with or without 75 μg/mL of crowding agent carrageenan (CR). Viability and metabolic activity of eTCs were affected by FBS. eTCs in ES reached higher cell density than in FBS in day 7, especially with CR. Morphology of eTCs was maintained under different sera. Silver staining on pepsin digested cell layers shows that collagen type I deposition rate is remarkably enhanced in the presence of CR in all conditions. Immunofluorescence showed increased expression for collagen I, III, V and VI in both sera in the presence of CR. Deposition of all collagen types but type VI was increased by ES supplementation. We conclude that ES in combination with CR can represent a reliable choice for the ex vivo expansion of eTCs

Introduction. Femoral periprosthetic fractures above TKA are commonly treated with retrograde intramedullary nailing (IMN). This study determined if TKA design and liner type affect the minimum knee flexion required for retrograde nailing through a TKA. Methods. Twelve cadaveric specimens were prepared for six single radius (SR) TKAs and six asymmetric medial pivot (MP) TKAs. Trials with 9mm polyethylene liners were tested with cruciate retaining (CR), cruciate substituting (CS) and posterior stabilizing (PS) types. The knee was extended to identify the minimum knee flexion required to allow safe passage of the opening reamer while maintaining an optimal fluoroscopic starting point for retrograde nailing. Furthermore, the angle of axis deviation between the reamer and the femoral shaft was calculated from fluoroscopic images. Results. In all specimens, the reamer entry point was posterior to Blumensaat's line. In the SR TKA, the average flexion required was 70, 71 and 82 degrees for CR, CS and PS respectively. The required flexion in PS was significantly greater than the other designs (p=0.03). In the MP TKA, the average flexion required was 74, 84 and 123 degrees for CR, CS and PS respectively. The required flexion was significantly greater in CS and PS designs (p<0.0001). Femoral component size did not affect the minimum flexion required. Furthermore, the entry reamer required 9.2 (SR) and 12.5 (MP) degrees of posterior axis deviation from the femur. Conclusions. Our study illustrates four novel factors to consider when performing retrograde nailing through TKA. First, significant knee flexion is required to obtain an ideal radiographic starting point when retaining the liner. Second, PS implants require more flexion with both TKA designs. Third, femoral component size does not affect the flexion required. Fourth, there is a consistent posterior axis deviation of the entry reamer from the femoral shaft, explaining the commonly created extension deformity

Background. Investigations into the response to implant debris tend to concentrate on how a population of cells proliferate in the presence of implant material, and how the regulation of cytokines change. For the problem of cobalt-chromium (CoCr) implants this has been done for osteoblasts and osteoclasts to understand how bone resorption, leading to aseptic loosening, is occurring. However, investigating the formation of the extracellular-matrix (ECM) may give a better indication of the mechanisms occurring. ECM is excreted from cells and is important for adhesion, structure, signaling and growth. Type I collagen is the most abundant protein in the ECM and is known to direct tissue development and is therefore a key part of understanding the mechanism behind aseptic loosening. Methods. 3T3-fibroblasts were seeded in Dulbecco's Modified Eagle Medium (DMEM) and supplemented with 100mM ascorbic acid. Every 48hours cells were fed with DMEM and doped with Co and Cr ions until fixation. Sirius Red dye was used to bind to the type I collagen, then removed using NaOH and analysed using UV absorption to show relative amounts of collagen. Type I collagen gel was formed in the presence of Co and Cr ions with and without DMEM and the fibers were imaged using AFM. Results and Conclusions. Studies show a decrease in the collagen output of 3T3-fibroblasts with increasing concentration of Co ions, and low concentrations of Cr ions. Precipitation was also seen for Cr ions in the presence of DMEM which may explain the reduced effect of higher concentration of Cr ions in comparison to Co ions. Co and Cr ions do influence the ECM which will affect the bone re-modelling process. Further work will be performed to link these results to mineralisation mechanisms to quantitatively determine the impact of metal ion debris on the ECM and collagen fiber formation

Summary. The effect of the geometry of the tibial polyethylene insert was investigated in vivo loaded conditions. Introduction. The decision to choose CR (cruciate retaining) insert or CS (condylar stabilised) insert during TKA remains a controversial issue. Triathlon CS type has a condylar stabilised insert with an increased anterior lip that can be used in cases where the PCL is sacrificed but a PS insert is not used. The difference of the knee kinematics between CR and CS insert remains unclear. This study measured knee kinematics of deep knee flexion under load in two insert designs using 2D/3D registration technique. Patients and Methods. We investigated the in vivo knee kinematics of 20 knees (18 patients) implanted with Triathlon CR components (Stryker Orthopedics, Mahwah, NJ), 10 knees in the CR insert with retaining PCL, and 10 knees in the CS insert with sacrificing PCL. All TKAs were judged clinically successful (Knee Society knee scores >90), with no ligamentous laxity or pain. Mean patient age at the time of operation was 72±12 years in CR and 69±9 years in CS. Mean period between operation and surveillance was 20±11 months in CR and 11±5 months in CS. Under fluoroscopic surveillance, each patient did a wight-bearing deep knee bending motion. Femorotibial motion including tibial polyethylene insert was analyzed using 2D/3D registration technique, which uses computer-assisted design (CAD) models to reproduce the spatial position of the femoral, tibial components from single-view fluoroscopic images. We evaluated the range of motion, femoral axial rotation, and antero-posterior (AP) translation of the nearest points. Results. The average range of motion between femoral component and tibial component was 113.3±22.3° in CR and 107.4±13.1° in CS. The amount of femoral axial rotation from 0° to 110° flexion was 8.6±2.9° in CR insert, and 7.6±2.6° in CS insert, respectively. No significant difference was observed in the amount of femoral external rotation (p=0.71). In CR insert, the medial contact point moved 4.0±2.9mm anteriorly from 0° to 100° flexion. The lateral contact point moved 2.0±1.1mm anteriorly from 60° to 90° flexion. In CS insert, the medial contact point moved 6.4±2.1mm anteriorly from 20° to 100° flexion. The lateral contact point moved 1.9±1.7mm anteriorly from 50° to 110° flexion. There was significant differences were observed in the amount of medial anterior translation between the two insert (medial; p=0.04, lateral; p=0.94). Discussion and Conclusion. Triathlon CR and CS insert had a similar kinematics pattern. However, there was significant differences were observed in the amount of medial anterior translation between the two insert. These results indicated that the increased anterior lip could not control medial anterior sliding. The posterior part of the two insert were almost same, so the kinematics are similar

Systemic metal ion monitoring (Co;Cr) has proven to be a useful screening tool for implant performance to detect failure at an early stage in metal-on-metal hip arthroplasty. Several clinical studies have reported elevated metal ion levels after total knee arthroplasty (TKA), with fairly high levels associated with rotating hinge knees (RHK) and megaprostheses. 1. In a knee simulator study, Kretzer. 2. , demonstrated volumetric wear and corrosion of metallic surfaces. However, prospective in vivo data are scarce, resulting in a lack of knowledge of how levels evolve over time. The goal of this study was to measure serum Co and Cr levels in several types TKA patients prospectively, evaluate the evolution in time and investigate whether elevated levels could be used as an indicator for implant failure. The study was conducted at Ghent University hospital. 130 patients undergoing knee arthroplasty were included in the study, 35 patients were lost due to logistic problems. 95 patients with 124 knee prostheses had received either a TKA (primary or revision) (69 in 55 patients), a unicompartimental knee arthroplasty (7 UKA), a RHK (revision −7 in 6 patients) or a megaprosthesis (malignant bone tumours − 28 in 27 patients). The TKA, UKA and RHK groups were followed prospectively, with serum Co and Cr ions measured preoperatively, at 3,6 and 12 months postoperatively. In patients with a megaprosthesis, metal ions were measured at follow-up (cross-sectional study design). In primary knees, we did not observe an increase in serum metal ion levels at 3, 6 or 12 months. Two patients with a hip arthroplasty had elevated preTKA Co and Cr levels. There was no difference between unilateral and bilateral knee prostheses. In the revision group, elevated pre-revision levels were found in 2 failures for implant loosening. In both cases, ion levels decreased postoperatively. In revisions with a standard TKA, there was no significant increase in metal ions compared to primary knee arthroplasty. RHK were associated with a significant increase in Co levels even at short-term (3–12 months). The megaprosthesis group had the highest metal ion levels and showed a significant increase in Co and Cr with time in patients followed prospectively. With the current data, we could not demonstrate a correlation between metal ion levels, size of the implant or length of time in situ. In primary knee arthroplasty with a standard TKA or UKA, metal ion levels were not elevated till one year postoperatively. This suggests a different mechanism of metal ion release in comparison to metal-on-metal hip arthroplasties. In two cases of revision for implant loosening, pre-revision levels were elevated, possibly associated with component wear, and decreased after revision. With RHK, slightly elevated ion levels were found prospectively. Megaprostheses had significantly elevated Co and Cr levels, due to corrosion of large metallic surfaces and/or wear of components which were not perfectly aligned during difficult reconstruction after tumour resection. Further research is needed to assess the clinical relevance of metal ion levels in knee arthroplasty

Background. Open reduction and internal fixation using plate osteosynthesis for midshaft clavicle fractures is often associated with hardware prominance. Although clinical studies have suggested a role for the use of thinner 2.7mm plates as a means of increasing cosmetic acceptability this still remains an area of controversy. We investigated the effect of plate size (2.7mm vs. 3.5mm), plate treatment (annealed vs. cold worked) and number of screws on the stiffness and yield point. Methods. Twenty-four synthetic clavicles were randomly divided into four treatment groups - Synthes (Synthes, Paoli, PA) 2.7mm cold-worked calcaneal reconstruction plate with six or eight bicortical screws; 3.5mm LCP reconstruction plate (RP) and 3.5mm LCP pre-contoured superior-anterior clavicle plate (PCSA). After measuring the baseline stiffness of the intact specimens, all clavicles were plated, a wedge-shaped inferior defect was created and testing performed using a cantilever-bending model. Statistical analysis was performed using one-way ANOVA with Tukey's multiple comparison test with significance set at a P value <0.05. Results. The 3.5mm RP construct was significantly stiffer than both of the 2.7mm CR constructs (P < 0.0001). The yield point for the 3.5mm PCSA construct was greater than the other three constructs (P < 0.0001), while the yield point for the 2.7mm CR plate with 6 screws and with 8 screws was higher than the 3.5mm RP construct (P = 0.0002 and P = 0.0023 respectively). The amount of displacement required to reach the yield point was highest for the 2.7mm CR plate with six screws and this was significantly higher than the values for the other three constructs. Conclusion. The 3.5mm plates demonstrated increased bending stiffness compared to the 2.7mm plates. Despite the lower resistance to bending forces, the cold worked 2.7mm plate exhibited a significantly higher yield point and required significantly more superior to inferior displacement to deform

We assessed carpal collapse by measuring the capitate-radius (CR) distance on standard plain radiographs. This new method required validation of diagnostic accuracy, so we compared it with the method of Nattrass et al. 1. known as revised carpal height (RCH). We studied wrist radiographs from 16 normal subjects and 11 patients with unilateral Kienböck’s disease. We found that there was a significant difference in the left/right CR index between the normal wrists and those with Kienböck’s disease (p < 0.001). The use of left/right RCH index showed no significant difference (p = 0.30). Diagnostic accuracy was shown to be higher for the CR index using ROC curves. We then assessed 40 normal wrists and found the mean CR index to be 0.999 ± 0.034, and suggest that values less than 0.92 are abnormal. The CR index can be used for diagnosis in unilateral carpal collapse, and for monitoring progress where the condition is bilateral

Whether it is best to retain the posterior cruciate ligament in the degenerated knee, i.e. using a cruciate-retaining (CR) total knee prosthesis (TKP), or to use a more constraint posterior-stabilized (PS) TKP is of debate. There are limited studies comparing the effect of both methods on implant fixation and clinical outcome, leaving it up to the surgeon to base this decision on anything but conclusive evidence. We assessed the effect of two different philosophies in knee arthroplasty on clinical outcome and tibial component migration measured with radiostereometric analysis (RSA), by directly comparing the CR and PS version of an otherwise similarly designed cemented TKP. Sixty patients were randomized and received a Triathlon TKP (Stryker, NJ, USA) of either CR (n=30) or PS (n=30) design. RSA measurements (primary outcome) and clinical scores including the Knee Society Score and Knee injury and Osteoarthritis Outcome Score were evaluated at baseline, at three months postoperatively and at one, two, five and seven years. A linear mixed-effects model was used to analyse the repeated measurements. Both groups showed a similar implant migration pattern, with a maximum total point motion at seven years follow-up of around 0.8 mm of migration (mean difference between groups 95% CI −0.11 to 0.15mm, p=0.842). Two components (one of each group) were considered to have an increased risk of aseptic loosening. Both groups improved equally after surgery on the KSS and KOOS scores and no differences were seen during the seven years of follow-up. No differences in implant migration nor clinical results were seen seven years after cruciate-retaining compared to posterior-stabilized total knee prostheses

Commonly used alterations of prosthetic surfaces include grit-blasting (GB), plasma-sprayed titanium (Ti) or hydroxyapatite (HA) coating. Systemic concentrations of cobalt (Co) and chromium (Cr) are elevated in patients with metal-on-metal hip replacement, but can occur for all modular hip replacements. Here, we use whole genome microarrays to assess differential gene expression in primary human osteoblasts grown in vitro and on these prosthesis surfaces following exposure to clinically relevant concentrations of Co and Cr. Mesenchymal cells obtained from bone-fragments of 3 patients undergoing joint replacement surgery were differentiated into osteoblasts. Subsequently, cells were cultured in vitro on tissue-culture plates (TCP), or on GB, Ti and HA surfaces (JRI Orthopaedics Ltd, Sheffield, UK). Following 24hr exposure to a combination of clinically equivalent concentrations of Co2+:Cr3+, RNA was extracted and hybridized to SurePrint-G3 Gene Expression Microarray. Probe signals were normalised using ‘Limma’ package on R-Bioconductor and differential gene expression assessed with empirical Bayes approach (Log2FC>1.00, P<0.001 for differentially expressed genes). For cells grown on TCP, 11 genes were upregulated with 500μg/L Co2+:Cr3+. Of these, 4 were associated to HIF-1 signalling based on KEGG pathway analysis (P=5.4e-5). Exposure to 1000μg/L Co2+:Cr3+ altered expression at 164 loci for HA surfaces, and a separate 50 loci for Ti surfaces compared to GB surfaces. Genes for osteoblast differentiation (BMP2 and RGS2) were downregulated on HA surfaces compared to GB, whilst genes for cell-adhesion (ESAM), vesicular trafficking (RAB37) and protection against oxidative damage (NRF2) were upregulated. Ti surfaces caused an upregulation in ERBB3 and CNTF, which are associated with inhibition of osteoblast differentiation and mineralisation, when compared to GB surfaces. This study confirms the role of HIF-1 signalling in response to prosthesis generated metal ions, and is the first to provide a comprehensive genome-wide insight into transcriptional response of osteoblasts at prosthesis surface to clinically equivalent metal exposure

Study Aim

Femoral components used in total knee arthroplasty (TKA) are primarily designed on the basis of kinematics and ease of fixation. This study considers the stress-strain environment in the distal femur due to different implant internal geometry variations (based on current industry standards) using finite element (FE) analyses. Both two and three dimensional models are considered for a range of physiological loading scenarios – from full extension to deep flexion. Issues associated with micro-motion at the bone-implant interface are also considered.

The establishment of a suitable animal model of repair of the rotator cuff is difficult since the presence of a true rotator cuff anatomically appears to be restricted almost exclusively to advanced primates. Our observational study describes the healing process after repair of the cuff in a primate model. Lesions were prepared and repaired in eight ‘middle-aged’ baboons. Two each were killed at four, eight, 12 and 15 weeks post-operatively. The bone-tendon repair zones were assessed macroscopically and histologically.

Healing of the baboon supraspinatus involved a sequence of stages resulting in the reestablishment of the bone-tendon junction. It was not uniform and occurred more rapidly at the sites of suture fixation than between them. Four weeks after repair the bone-tendon healing was immature. Whereas macroscopically the repair appeared to be healed at eight weeks, the Sharpey fibres holding the repair together did not appear in any considerable number before 12 weeks. By 15 weeks, the bone-tendon junction was almost, but not quite mature.

Our results support the use of a post-operative rehabilitation programme in man which protects the surgical repair for at least 12 to 15 weeks in order to allow maturation of tendon-to-bone healing.

We have previously observed an increase in total bone mineral density and reduced bone turnover (TRAP5b and osteocalcin) in patients with well-functioning metal-on-metal hip resurfacing (MOMHR). Here, we provide data to support the hypothesis that osteoclast differentiation and function is altered in this patient population, and that this effect is transferrable through their serum. Patients with well-functioning MOMHR (cases, n=18) at a median follow-up of 8 years were individually matched for gender, age and time-since-surgery to a low-exposure group consisting of patients with THA (controls, n=18). The monocyte fraction of patient peripheral blood was isolated and differentiated into osteoclasts on dentine wafers using RANKL and M-CSF supplemented media (osteoclastogenic media, OM). Cultures were monitored for the onset of resorption, at which point the cells were treated with OM, autologous serum or serum from matched MOMHR/THA donors, all supplemented with RANKL and M-CSF. At the end of the culture, cells were TRAP-stained and quantified using CellD Software Package, Olympus. When cells were differentiated in standard osteoclastogenic media, the resorbing ability of osteoclasts derived from MOMHR patients was reduced 22%(p<0.0079) compared to THA. The resorbing ability of osteoclasts generated from MOMHR patients and differentiated in autologous serum was reduced 33%(p<0.0001), whilst matched THA serum caused a smaller reduction of 14%(p<0.01). When cells derived from THA patients were differentiated in autologous serum, the resorbing ability of osteoclasts was similarly reduced by 35%(p<0.0001), whilst the matched MOMHR serum also caused a reduction of 21%(p<0.0001). This data suggests that prior exposure to higher circulating Co and Cr in patients with MOMHR reduces osteoclastogenesis, and that the detrimental effect on the functionality of mature osteoclasts is transferable through the serum. This has implications for systemic bone health of patients with MOMHR or modular taper junctions

The most common reasons for total joint arthroplasty (TJA) failure are aseptic loosening (AL) and prosthetic joint infection (PJI). There is a big clinical challenge to identify the patients with high risk of AL/PJI before the TJA surgery. Although there is evidence that genetic factors contribute to the individual susceptibility to AL/PJI, a predictive model for identification of patients with a high genetic risk of TJA failure has not been developed yet. We aimed to develop a risk evaluation tool utilising the AL/PJI-associated polymorphisms for identification of patients with high genetic risk of TJA failure based on inflammation-gene polymorphism panel. Based on allele and genotype frequencies of twenty-five single nucleotide polymorphisms (SNPs) in TNF, IL2, IL6, IL10, IL1b, IL-1Ra, MBL2, MMP1, FTO genes and those influencing the serum levels of biomarkers of TJA outcomes (IL6, CCL2/MCP-1, CRP, ESR) in peripheral blood obtained from patients with TJA (AL, n=110; PJI, n=93; no complications, n=123), we calculated a hazard ratio and a relative entropy of alleles and genotypes associated with AL and PJI and their combinations in patient subgroups. We conducted a risk evaluation tool based on the presence of risk alleles and genotypes in TNF (rs361525, rs1800629), DARC (rs12075), MBL2 (rs11003125) and FTO (rs9939609, rs9930506) genes associated with implant failure (AL/PJI). Of these, FTO gene variations (rs9939609, rs9930506) were associated mainly with PJI (P=0.001, OR=2.04, 95%CI=1.132–2.603; P=0.011, OR=1.72, 95%CI=1.338–3.096) and DARC (rs12075) with AL (P=0.005, OR=1.79, 95%CI=1.193–2.696). This tool calculates a hazard ratio of a combination of SNPs associated with AL and PJI for identification of patients with high and low risk of AL/PJI TJA failure. We proposed a risk evaluation tool for stratification of patients before the TJA surgery based on the genetic risk of AL/PJI development. The effect size for each genotype combination described in the study is small. Further multiparametric data analysis and studies on an extended patient cohort and other non-genetic and genetic parameters are ongoing. Grant support: AZV MZ CR VES16-131852A, VES15-27726A, IGA LF UP_2016_011

Wear particles produced by alumina ceramic-on-ceramic (CoC) bearings cause a minimal immunological response with low cytotoxicity and inflammatory potential. 1, 2. However, more comprehensive immunological studies are yet to be completed for the composite CoC (zirconia-toughened, platelet reinforced alumina) hip replacements due to difficulties in isolating the very low volume of clinically relevant wear debris generated by such materials in vitro. The aim of this study was to compare the cytotoxic effects of clinically relevant cobalt chromium (CoCr) nano-particles with commercial composite ceramic particles. Composite ceramic particles (commercial BIOLOX® delta powder) were obtained from CeramTec, Germany and clinically relevant CoCr wear particles were generated using a six station pin-on-plate wear simulator. L929 fibroblast cells were cultured with 50µm. 3. of CoCr wear debris or composite ceramic particles at low to high volumes ranging from 500µm. 3. –0.5µm. 3. per cell and the cyctotoxic effects of the particles were assessed over a period of 6 days using the ATP-Lite™ cell viability assay. The composite ceramic particles were bimodal in size (0.1–2µm & 30–100nm) and showed mild cytotoxic effects when compared with equivalent particle volumes (50µm. 3. ) of clinically relevant CoCr nano-particles (10–120nm). The CoCr nano-particles had significant cytotoxic effects from day 1, whereas the composite ceramic particles only showed cytotoxic effects at particle concentrations of 50 and 500µm. 3. after 6 days. The increased cytotoxicity of the clinically relevant CoCr nano-particles may have been attributed to the release of Co and Cr ions. This study demonstrated the potential cytotoxic effects of model ceramic particles at very high volume concentrations, but it is unlikely that such high particle volumes will be experienced routinely in vivo in such low wearing bearing materials. Future work will investigate the longer-term effects on genotoxicity and oxidative stress of low volumes of clinically-relevant generated BIOLOX® delta ceramic wear particles