Introduction. Geometric variations of the hip joint can give rise to abnormal joint loading causing increased stress on the articular cartilage, which may ultimately lead to degenerative joint disease. In-vitro simulations of total hip replacements (THRs) have been widely reported in the literature, however, investigations exploring the tribology of two contacting cartilage surfaces, and cartilage against metal surfaces using complete hip joint models are less well reported. The aim of this study was to develop an in-vitro simulation system for investigating and comparing the tribology of complete natural hip joints and hemiarthroplasties with THR tribology. The simulation system was used to assess natural porcine hip joints and porcine hemiarthroplasty hip joints. Mean friction factor was used as the primary outcome measure to make between-group comparisons, and comparisons with previously published tribological studies. Method. In-vitro simulations were conducted on harvested porcine tissue. A method was developed enabling natural acetabula to be orientated with varying angles of version and inclination, and natural femoral heads to be potted centrally with different orientations in all three planes. Acetabula were potted with 45° of inclination and in the complete joint studies, natural femoral heads were anatomically matched and aligned (n=5). Hemiarthroplasty studies (n=5) were conducted using cobalt chrome (CoCr) heads mounted on a spigot (Figure 1), size-matched to the natural head. Natural tissue was fixed using PMMA (polymethyl methacrylate) bone cement. A pendulum friction simulator (Simulator Solutions, UK), with a dynamic loading regime of 25–800N, ± 15° flexion-extension (FE) at 1 Hertz was used. The lubricant was a 25% (v/v) bovine serum. Axial loading and motion was applied through the femoral head and frictional torque was measured using a piezoelectric transducer, from which the friction factor was calculated. Results. The correct anatomical orientation and positioning was achieved enabling in-vitro simulation testing to be conducted on hemiarthroplasty and complete hip joint samples for two-hours. Mean friction increased rapidly followed by a continued gradual increase to ≈0.03 ± 0.00 in the complete joints, with the hemiarthroplasty group plateauing at ≈0.05 ± 0.01 (Figure 2). Mean friction factor was significantly lower (t-test; p < 0.05) in the complete natural joint group. Discussion. An in-vitro simulation system for the natural hip joint with controlled orientation of the femur and acetabulum was successfully developed and used to measure friction in complete porcine hip joints and porcine hip hemiarthroplasties. A non-linear increase in friction indicative of biphasic lubrication was observed in both groups with slower exudation of fluid from the complete joints compared to the hemiarthroplasties, inferring a quicker move towards solid-phase lubrication. Higher friction in the hemiarthroplasties, which was similar to that measured in-vitro in metal-on-polyethylene THRs, was most likely due to variable clearances between the non-conforming spherical metal head and aspherical acetabulum, causing poorer congruity and distribution of the load. This could in time lead to abrasive wear and cartilage degradation. This methodology could have an important role when investigating associations between hip geometric variations, interventions for hip disease/pathology, and risk factors for cartilage degeneration

Total ankle replacement (TAR) is the main surgical option in case of severe joint osteoarthritis. The high failure rate of current TAR is often associated to inappropriate prosthetic articulating surfaces designed according to old biomechanical concepts such the fixed axis of rotation, thus resulting in non-physiological joint motion. A recent image-based 3D morphological study of the normal ankle (Siegler et al. 2014) has demonstrated that the ankle joint surfaces can be approximated by a saddle-shaped cone with its apex located laterally (SSCL). We aimed at comparing the kinematic effects of this original solution both with the intact joint and with the traditional prosthetic articulating surfaces via in-silico models and in-vitro measurements. Native 3D morphology of ten normal cadaver ankle specimens was reconstructed via MRI and CT images. Three custom-fit ankle joint models were then developed, according to the most common TAR designs: cylindrical, symmetrically-truncated medial apex cone (as in Inman's pioneering measures), and the novel lateral apex cone, i.e. SSCL. Bone-to-bone motion, surface-to-surface distance maps, and ligament forces and deformations were evaluated via computer simulation. Prototypes of corresponding prosthesis components were designed and manufactured via 3D-printing, both in polymer-like-carbon and in cobalt-chromium-molybdenum powders, for in-vitro tests on the cadaver specimens. A custom testing rig was used for application of external moments to the ankle joint in the three anatomical planes; a motion tracking system with trackers pinned into the bone was used to measure tibial, talar and calcaneal motion (Franci et al. 2009), represented then as tibiotalar, subtalar and ankle complex 3D joint rotations. Each ankle specimen was tested in the intact joint configuration and after replacement of the articulating surfaces according with the three joint models: cylindrical, medial apex cone and SSCL. Results. Small intra-specimen data variability in cycle-to-cycle joint kinematics was found in all cadaver ankles, the maximum standard deviation of all rotation patterns being smaller than 2.0 deg. In-silico ligament strain/stress analysis and in-vitro joint kinematic and load transfer measurements revealed that the novel SSCL surfaces reproduce more natural joint patterns than those with the most common surfaces used in current TAR. TAR based on a saddle-shaped skewed truncated cone with lateral apex is expected to restore more normal joint function. Additional tests are undergoing for further biomechanical validation. The present study has also demonstrated the feasibility and the quality of the full process of custom TAR design and production for any specific subject. This implies a thorough procedure, from medical imaging to the production of artificial surfaces via 3D printing, which is allowing for personalised implants to become the future standard in total joint replacement

Introduction: Squeaking after total hip replacement has been reported in up to 10% of patients. Some authors proposed that sound emissions from squeaking hips result from resonance of one or other or both of the metal parts and not the bearing surfaces. There is no reported in vitro study about the squeaking frequencies under lubricated regime. The goal of the study was to reproduce the squeaking in vitro under lubricated conditions, and to compare the in vitro frequencies to in vivo frequencies determined in a group of squeaking patients. The frequencies may help determining the responsible part of the noise. Methods: Four patients, who underwent THR with a Ceramic-on-Ceramic THR (Trident. ®. , Stryker. ®. ) presented a squeaking noise. The noise was recorded and analysed with acoustic software (FMaster. ®. ). In-vitro 3 alumina ceramic (Biolox Forte Ceramtec. ®. ) 32 mm diameter (Ceramconcept. ®. ) components were tested using a PROSIM. ®. hip friction simulator. The cup was positioned with a 75° abduction angle in order to achieve edge loading conditions. The backing and the cup liner were cut with a diamond saw, in order to avoid neck-head impingement and dislocation in case of high cup abduction angles. The head was articulated ± 10° at 1 Hz with a load of 2.5kN for a duration of 300 cycles. The motion was along the edge. Tests were conducted under lubricated conditions with 25% bovine serum without and with the addition of a 3rd body alumina ceramic particle (200 μm thickness and 2 mm length). Results: Edge loading was obtained incompletely. In-vitro, no squeaking occurred under edge loading conditions. However, with the addition of an alumina ceramic 3rd body particle in the contact region, squeaking was obtained at the beginning of the tests and stopped after ~20 seconds (dominant frequency 2.6 kHz). In-vivo, recordings had a dominant frequency ranging between 2.2 and 2.4 kHz. Discussion: For the first time, squeaking was reproduced in vitro under lubricated conditions. In-vitro noises followed edge loading and 3rd body particles and despite, the severe conditions, squeaking was intermittent and difficult to reproduce. However, squeaking is probably more difficult to reproduce because the cup was cut and the head was fixed in the simulator, preventing vibration to occur. Squeaking noises of a similar frequency were recorded in-vitro and in-vivo. The lower frequency of squeaking recorded in-vivo, demonstrates a potential damping effect of the soft tissues. Therefore, the squeaking in the patients was probably related to the bearing surfaces and modified lubrication conditions that may be due to edge loading. The determined values of frequencies may help to analyze the squeaking patients in order to determine the mechanism generating the sound

Introduction: Degenerative disc desease is one of the most frequently encountered spinal disorders. The intervertebral disc is a complex anatomic and functional structure, which makes the development of an efficient artificial disc a challenge [. 1. ]. Based on the complexity of the anatomical structures and the nearly unknown loading conditions at the moment only contradictory knowledge exists about the kinematics after TDA and in particular the location of the center of rotation in the human lumbar spine [. 2. ]. The objective of our study was to evaluate the kinematics of the human lumbar spine and the ability of TDA to restore the native conditions in regard to range of motion (ROM), neutral zone (NZ) and center of rotation (COR). Material and Methods: In-vitro flexibility testing on functional spinal units (FSU) out of 12 fresh frozen lumbar spines has been performed. The FSU (L2/L3 and L4/L5) were tested first in the native condition, followed by nucleotomy and partial annulus resection and also after TDA with activ L (lumbar artificial disc, Aesculap Germany). Therefore a spinal simulator has been customized, applying pure moments for flexion/extension, lateral bending and axial rotation (+/−7.5Nm) and axial preload (FP=400N) with a defined velocity (1°/s). The instantaneous COR has been calculated based on the velocity pole method using a 3D ultrasonic motion analysis system, measuring the twelve components of motion. Results: The TDA with activ L leads to a good restoration of ROM and NZ in all loading directions under in-vitro flexibility testing. The instantaneous COR is exemplary described for the native condition under flexion/ extension in the sagittal plane. For the native condition the COR is located in the center of the inferior vertebral endplate. After nucleotomy the COR shifts dorsally into the region of the spinal cord and a significant grade of instability has been measured. After insertion of the lumbar artificial disc the instability can be reduced to the native grade of motion and the COR is located again in the main axis of the spinal column in the upper third of the inferior vertebra. Conclusion: The instantaneous COR has been estimated in-vitro for the different loading situations in the human lumbar spine before and after TDA. Based on the newly introduced method further optimizations of TDA devices can be undergone in regard to the particular aspect of physiological kinematics

Introduction: Current total disc prostheses are 2- or 3-pieces devices, including 1 or 2 bearing surfaces, and providing 3 or 5 degrees of freedom but with no, or very little, resistance. The ESP. ®. is a one-piece deformable implant made of silicon and polycarbonate polyurethane elastomer securely fixed to titanium endplates. It allows limited rotation and translation with elastic return. This cushion without fixed rotation center achieves 6 degrees of freedom including shock absorption. An earlier attempt to use elastomers (Acroflex. ®. ) failed clinically due to the polymer. This highlights the need for accurate in-vitro fatigue testing and clinical evaluations. Methods: In-vitro fatigue testing with more than 40 millions cycles were performed on different samples for compression, flexion-extension bending, lateral bending, torsion and shear. A prospective trial was initiated in 2004 for L3L4, L4L5 and L5S1 levels. Total disc replacements have been performed in 153 lumbar levels through extra-peritoneal mini-invasive anterior approach. Results: After in-vitro testing, microscopic examination showed that the polymer core remained unchanged without evidence of cracking or other degradation. Gravimetric analysis revealed insignificant changes in weight. The geometrical characteristics and the cohesion of the implants remained stable. After 3 years clinical experience, there was no device related complication, except one early revision for a post-traumatic implant migration. VAS and ODI scores improvements were equivalent to other published series. Discussion and Conclusion: In-vitro fatigue testing and short term results of the innovative ESP. ®. prosthesis demonstrate the reliability of the concept. The results are equivalent to other series with conventional implants

Methotrexate and Cox-2 inhibitors are thought to interfere with bone healing. There have been controversial results published in the literature. The effect of newer antirheumatoids (Leflunomide, Etanercept, Infliximab) has not been studied. The aim of this study was to find the in-vitro effect of methotrexate, newer anti-rheumatoids, steroids and cox-2 inhibitors on Osteoblasts. Osteoblasts were cultured from femoral heads obtained from young otherwise healthy patients undergoing total hip replacement. The cells were cultured using techniques that have been previously described. A computer aided design of experiment was used as a model for setting up the experiment on samples obtained from five patients. Normal therapeutic concentration of the various antirheumatoids was added alone and in combination to the media. The cell growth was estimated after two weeks using spectrophotometric technique using Roche Cell proliferation Kit. Multiple regression analysis was done to estimate the best predictor of the final result. Patient was found to be the most significant factor (p< 0.001) in predicting the ultimate response. Cox-2 inhibitor (Etoricoxib) was found to be the next best predictor (p=0.043). Etoricoxib in fact had a stimulatory effect (R=0.219) on the osteoblast growth, which was accentuated in the presence of other agents that varied amongst different patients. Different patients respond differently to the drugs. None of the antirheumatoids inhibit osteoblast proliferation and differentiation in-vitro. If osteoblastic activity is considered to be the primary factor responsible for bone healing, then an inhibition should not result in patients who are on these drugs

Sufficient primary stability of the acetabular cup is essential for stable osseous integration of the implant after total hip arthroplasty. By means of under-reaming the cavities press-fit cups gain their primary stability in the acetabular bone stock. These metal-backed cups are inserted intra-operatively using an impact hammer. The aim of this experimental study was to obtain the forces exerted by the hammer both in-vivo and in-vitro as well as to determine the resulting primary stability of the cups in-vitro. Two different artificial bone models were applied to simulate osteoporotic and sclerotic bone. Polymeth-acrylamid (PMI, ROHACELL 110 IG, Gaugler & Lutz, Germany) was used as an osteoporotic bone substitute, whereas a composite model made of a PMI-Block and a 4 mm thick (cortical) Polyvinyl chloride (PVC) layer (AIREX C70.200, Gaugler & Lutz, Germany) was deployed to simulate sclerotic bone. In all artificial bone blocks cavities were reamed for a press-fit cup (Trident PSL, Size 56mm, Stryker, USA) using the original surgical instrument. The impactor of the cup was equipped with a piezoelectric ring sensor (PCB Piezotronics, Germany). Using the standard surgical hammer (1.2kg) the acetabular cups were implanted into the bone substitute material by a male (95kg) and a female (75kg) surgeon. Subsequently, primary stability of the implant (n=5) was determined in a pull-out test setup using a universal testing machine (Z050, Ziwck/Roell, Germany). For validation the impaction forces were recorded intra-operatively using the identical press-fit cup design. An average impaction force of 4.5±0.6kN and 6.3±0.4kN using the PMI and the composite bone models respectively were achieved by the female surgeon in vitro. 7.4±1.5kN and 7.7±0.8kN respectively were obtained by the male surgeon who reached an average in-vivo impaction force of 7.5±1.6kN. Using the PMI-model a pull-out force of 298±72N and 201±112N were determined for the female and male surgeons respectively. However, using the composite bone model approximately half the pull-out force was measured for the female surgeon (402±39N) compared to the male surgeon (869±208N). Our results show that impact forces measured in-vitro correspond to the data recorded in-vivo. Using the osteoporotic bone model the pull-out test revealed that too high impaction forces affect the pull-out force negatively and hence the primary implant stability is reduced, whereas higher impact forces improve primary stability considerably in the sclerotic bone model. In conclusion, the amount of impaction force contributes to the quality of the obtained primary cup stability substantially and should be adjusted intra-operatively according to the bone quality of each individual patient

Purpose. The management of moderate to large engaging Hill-Sachs lesions is controversial and surgical options include remplissage, allograft reconstruction, and partial resurfacing arthroplasty. Few in-vitro studies have quantified their biomechanical characteristics and none have made direct comparisons. The purpose of this study was to compare joint stability and range of motion (ROM) among these procedures using an in-vitro shoulder simulator. It was hypothesized that all procedures would prevent defect engagement, but allograft and partial resurfacing would most accurately restore intact biomechanics; while remplissage would provide the greatest stabilization, possibly at the expense of motion. Method. Eight cadaveric shoulders were tested on an active in-vitro shoulder simulator. Each specimen underwent testing in 11 conditions: intact, Bankart lesion, Bankart repair, and two unrepaired Hill-Sachs lesions (30% & 45%) which were then treated with each of the three techniques. Anterior joint stability, ROM in extension and internal-external rotation, and glenohumeral engagement were assessed. Stability was quantified as resistance, in N/mm, to an anteriorly applied load of 70N. Results. Remplissage significantly increased joint stiffness compared to both defects (6.43.8 N/mm, p=0.01) and the allograft and partial resurfacing (p <= 0.04). No technique significantly surpassed the stability of the intact state (p>0.05). In adduction, the remplissage significantly reduced internal-external rotation compared to both defects (p <= 0.01), but only the 30% repair caused a significant change compared to the intact state (14.511.3 N/mm, p=0.05). In abduction, all repairs reduced rotation ROM compared to the Hill-Sachs defect (>= 8.24o, p <= 0.04), but none with respect to the intact condition (p >= 0.05). Remplissage had significantly less extension than either resurfacing procedure (>= 15.4o, p <= 0.02) and resulted in a greater reduction in extension ROM for 45% defects compared to 30% defects (11.918.91, p=0.06). All unrepaired lesions engaged during extension. None of the remplissage or allograft reconstructions engaged, however, 75% of partial resurfacing arthroplasties partially engaged. Conclusion. This study is the first biomechanical evaluation to directly compare three surgical procedures for engaging Hill-Sachs lesions. Each procedure enhanced stability; however, the enhancement provided by the resurfacing repairs more closely resembled the intact state. Remplissage of the 30% and the 45% defects improved stability and eliminated glenohumeral engagement but caused significant and progressive reductions in ROM. In comparison, both the allograft and partial resurfacing procedures re-established ranges of motion approaching those of the intact joint; however, the partial resurfacing could not fully prevent engagement. These findings indicate that the effects of each technique are not equivalent and further clinical and biomechanical studies are required

This in-vitro study was conducted to determine the effect of rotator cuff tears on joint kinematics. A shoulder simulator produced unconstrained active abduction of the humerus. Three sequential 1cm lesions were created, the first two in the supraspinatus tendon and the third in the subscapularis tendon. The plane of abduction moved posteriorly and became more abnormal throughout abduction as the size of the tear increased. It is concluded that in order to generate the same motions achieved by the intact joint other muscle groups must be employed, inevitably resulting in altered joint loading. This in-vitro study was conducted to determine the effect of simulated progressive tears of the rotator cuff on active glenohumeral joint kinematics. Five cadaveric shoulders were tested using a shoulder simulator designed to produce unconstrained active motion of the humerus. Forces were applied to simulate loading of the supraspinatus, subscapularis, infraspinatus/teres minor, anterior, middle, and posterior deltoid muscles based upon variable ratios of electromyographic data and average physiological cross-sectional area of the muscles. Three sequential 1cm lesions were created, the first two in the supraspinatus tendon and the third in the subscapularis tendon. Simulated active glenohumeral abduction was performed following the creation of each lesion. Five successive tests were performed to quantify repeatability. The plane of abduction moved posteriorly and became more abnormal throughout abduction as the size of the lesion increased (p=0.01) (Figure 1). In order to generate the same motions achieved with an intact rotator cuff other muscle groups must be employed, inevitably resulting in altered joint loading. A better understanding of the effects that rotator cuff tears have on the kinematics of the glenohumeral joint may result in the development of innovative rehabilitation strategies to compensate for this change in muscle balance and improve the clinical outcomes. Please contact author for diagram and/or graph

Quantitative measurements of load transfer through the distal radioulnar joint (DRUJ) are limited. An instrumented ulnar head prosthesis was developed to measure bending and torsion moments about the three anatomic axes of the ulna. This device has shown repeatable loading data following insertion in a cadaveric specimen during active forearm rotation trials conducted in an in-vitro upper extremity joint simulator. The data acquired from this device will have important implications for upper extremity modeling, implant fixation and design, and optimizing surgical procedures related to DRUJ arthroplasty. To develop a system to quantify in-vitro load transfer through the distal radioulnar joint (DRUJ) following ulnar head arthroplasty during simulated active forearm rotation. Also, the effect of an eccentric ulnar head implant design was investigated. A load-measuring system was developed that was easily surgically inserted, and produced repeatable loading data. The instrumented implant developed in this study will contribute to the optimization of surgical procedures and implant design parameters related to distal ulnar arthroplasty. Four pairs of strain gauges were applied to the stem of an ulnar head prosthesis to measure bending and torsion moments about the three anatomic axes of the ulna. Three ulnar heads were machined with varying eccentricities (axisymmetric, 1.5 mm offset and 3.0 mm offset). The implant was inserted in one unpreserved cadaveric upper extremity and active forearm rotation induced using a computer controlled joint simulator. Repeatability (assessed using the maximum standard deviation over 5 trials of pronation and supination) was less than 9% of the output range for all loads. Bending and torsion moments between −0.4 and 0.5 Nm, correlating to joint loads between 0 and 50 N, were measured. The measured loads followed a consistent pattern with forearm position. Higher loads were noted for the eccentric implant heads compared to the axisymmetric head, especially at the extreme ranges of rotation. Clinical interpretation of these findings is difficult since the optimal loading scenario for distal ulnar implant longevity remains unknown. Please contact author for diagrams and graphs

According to the Canadian Joint Replacement Registry, in 2010–2011 there were 17,303 hip replacements performed in Canada of which 10% were revisions. More than 73% of these revisions were for aseptic loosening, wear, and instability which suggests that hip biomechanics may be anomalous. The hip joint is often described as a ball-and-socket joint, which implies congruent interacting bony joint surfaces and purely rotational relative motion. This study challenges the accepted kinematic description by analysing detailed motion of the hip joint using surgical navigation technology. An in-vitro study was conducted using twelve fresh frozen cadaveric human hemi-pelvises in three soft-tissue states. Three dimensional digital models of each specimen were generated from segmentation of computed tomography images. Local coordinate reference devices, mounted on the proximal femur and anterior-superior iliac spine, were registered and tracked with an active optical localisation system. Positions and orientations were imported to custom virtual surgery software. The study used soft-tissue states as one variable and twelve combinations of flexion/extension, abduction/adduction and internal/external rotation as the other variable. The entire series of motions were repeated for (I) soft tissues intact, (II) capsule intact and (III) completely disarticulated joint. Translation of the femoral head with respect to the acetabular cup at each frame was extracted from the recorded data. An Analysis of Variance (ANOVA) was used to determine whether the means of translations in each dissection states were significantly different. Translatory motion was observed in all specimens. Significant differences were found between magnitudes of translation in distinct soft tissue states (p<0.001). Investigation of sudden changes in translational tracks of each femoral head, plotted as 2-D wave forms, showed that there were no correlations between contact zones and excursions. Interestingly, three specific maneuvers were found to be more likely to cause maximal translations: ankle on knee (where the femur is flexed and externally rotated while being abducted), ankles crossed (where the femur is flexed and externally rotated while being adducted) and the pivot (where the femur is extended and externally rotated while the pelvis is abducted). The highly accurate surgical navigation system detected subtle translatory behaviour in hip motion. The data provided evidence that the femoral head translates with respect to the acetabular cup with or without any contact between the two bones; such impingements were previously thought to be the main reason for femoral excursion. The statistical significance found between translations exhibited at different soft tissue states indirectly supports an aspherical model of the adult hip, with kinematics driven by both soft tissue and the anatomy. This work towards an improved biomechanical model of the hip could help guide both surgical intervention and implant design, leading to improved outcomes for the hundreds of thousands of hip surgeries performed globally each year

Bone is the preferred site of metastases in women with breast cancer, which can cause skeletal-related events (SRE¡¦s) such as pathologic fractures. Bisphosphonates are the current standard of care for treatment of meta-static bone disease by preventing further bone destruction. Photodynamic therapy (PDT) has been applied successfully as a non-radiative treatment for malignancies. In PDT, light is delivered to a tumour after the administration of a photosensitiser. Earlier pre-clinical studies in a metastatic rat model have shown that PDT reduced the tumour burden in the vertebrae. The goal of this investigation was to study the effect of PDT on bisphosphonate pre-treated cancer in-vitro. Human breast cancer cells, MT-1, were cultured until confluent. The following groups were formed: no treatment; incubation with zoledronic acid (24h; 10 ƒÝmol) only; PDT treatment only and incubation with zoledronic acid and PDT treatment. Prior to light application 1 microg/ml of the photosensitiser BPD-MA was added. PDT was performed with a light dose of 1J and 10 J. The cells were stained with a live/dead stain and analyzed by fluorescence microscope and flowcytometry. Incubation of the MT-1 carcinoma cells with bisphosphonate zoledronic acid resulted in a significantly higher number of dying cells following PDT treatment when compared cells that were not treated by zoledronic acid (p< 0.05). When comparing cell groups that did not undergo PDT treatment the incubation with zoledronic acid alone did not have a statistically significant effect on cell survival twenty-four hours following zoledronic acid administration. In-vitro, breast cancer cells appear more susceptible to PDT after they have been incubated with the zoledronic acid. Zoledronic acid, a potent bisphosphonate, inhibits farsenylpyrophosphate (FPP) which is involved in farsenylation of cell membrane proteins. The inhibition of FPP may cause a reduced effect of PDT on cell rescue. The treatment with bisphosphonates seems to have a synergistic effect with PDT treatment. As such, light dosimetry in PDT treatment may need to take into account potential therapeutic interactions between PDT and current medical therapies in the treatment of skeletal metastatic burden

To evaluate the mechanism by which orthopedic implant wear particles induce apoptosis in immature osteoblasts in an in-vitro setting. Stromal cells from femurs of thirty day-old Swiss Webster Mice were isolated, cultured in-vitro, and incubated with orthopedic wear particles in the micrometer size range. After incubation with wear-particles, the cells were assessed for Caspase three expression and activity in the presence or absence of specific inhibitor(s) in order to delineate potential mechanism for cellular changes previously reported. Here we report the induction of caspase three protein expression and activity with incubation of stromal cells with titanium wear particles. Caspase three activity however was not demonstrated to be up regulated in a time dependent manner or at lower concentration of particles (2 x 107 particles/ml). However, there was a significant (P< 0.05) increase in caspase three activity with titanium particle at higher concentration (4 x 107 particles/ml) that was not reversible when the extrinsic arm of the apoptotic pathway was blocked with anti-TNFƒa antibodies. Our previous studies have suggested that aseptic loosening of orthopedic implants may be independent of inflammatory processes, and may be associated with induction of programmed cell death. Our current results would strengthen this idea by demonstrating induction of expression and activity of caspase three involved in apoptosis in cells incubated with wear particles. In addition, titanium wear particles may induce apoptosis through direct cellular effects rather than through the extrinsic TNFƒa pathway. Delineating the mechanism by which wear particles induce apoptosis in immature osteoblasts will allow for the selection and/or development of inhibitors to the process of asceptic loosening by targeting a specific pathway

Introduction. The frequency of revision hip arthroplasty is increasing with the increasing life expectancy and number of individuals treated with joint replacement. Newer porous implants have been introduced which may provide better treatment options for revision arthroplasty. These may require cementation to other prosthesis components and occasionally to bone, however, there is currently no information on how these porous implants interface with cement. Materials and Methods. Cylindrical bone (control group) and porous metal probes with a diameter and height of 10mm were created and subsequently cemented in a standardized setting. These were placed under tensile and torsional loading scenarios. In this experimental study, 10 human femoral heads were used to create 20 cylindrical probes with a diameter and height of 10mm. One side was tapered to 6mm for cementation and interface evaluation. A further set of 20 probes of a porous metal implant (Trabecular Metal®) was created with the same geometry. After the probes were created and lavaged, they were cemented at the tapered surface using a medium viscosity cement at a constant cementation pressure (1.2N/mm2). The setup allowed for comparison of the porous metal/cement interface (group A) with the well-studied control group interface bone/cement (group B). The maximal interface stability of groups A and B were evaluated under tensile and rotational loading scenarios and the cement penetration was measured. Results. Group A showed a significantly decreased cement penetration under the same cementation pressure than group B, yet the interface showed a significantly more stable interface in the measured tests: larger maximum tensile force (effect size 2.7), superior maximum tensile strength (effect size 2.6), greater maximum torsional force (effect size 2.2), and higher rotational stiffness (effect size 1.5). Discussion and Conclusion. The porous metal/cement interface displays substantially more stability than does the bone/cement interface. Although these tests evaluate initial stability in an in-vitro setting, they appear promising with regard to their cemented stability. As a result, a multicomponent porous metal construct with cement interdigitation should not compromise the overall implant primary stability

Purpose. The coronoid process is an integral component for elbow stability. In the setting of a comminuted coronoid fracture, where repair is not possible, a prosthetic device may be beneficial in restoring elbow stability. The hypothesis of this in-vitro biomechanical study was that an anatomic coronoid prosthesis would restore stability to the coronoid deficient elbow. Method. A metal coronoid prosthesis was designed and developed based on CT-derived images adjusted for cartilage thickness. The kinematics and stability of eight fresh-frozen male cadaveric arms (mean age 77.4 years, range 69–92 years) were quantified in the intact state; after collateral ligament sectioning and repair (control state); after a simulated 40% transverse coronoid fracture; and after implantation of a coronoid prosthesis. Elbow flexion was simulated passively with the arm oriented in the varus position and the forearm in pronation. Varus-valgus angulation (VV) and internal-external rotation (IE) of the ulna relative to the humerus were quantified with an electromagnetic tracking system (Flock of Birds, Ascension Technologies, Burlington, VT, static accuracy: 1.8mm position, 0.5 orientation). Results. No significant difference was found between the intact elbow and the native coronoid control state with collateral ligament repair (mean standard deviation) (VV=0.13.1, p=0.9; IE=0.82.59, p=0.4). A significant decrease in stability was observed following the 40% coronoid fracture (VV=5.73.4, p<0.01; IE=10.93.35, p<0.001). Following coronoid hemi-arthroplasty, no significant difference in stability was found between the coronoid prosthesis and the control state (VV=0.22.7, p=1.0; IE=1.33.0, p=0.8). Conclusion. An anatomic coronoid prosthesis restores the stability of the coronoid deficient elbow similar to the intact state. Further studies are needed to determine the optimum fixation method of this device and to determine the range of sizes which would be required for the successful commercialization of this device for patient use. Clinical trials will be required to confirm the favourable findings of this in-vitro investigation

Mesenchymal stem cells (MSCs) are exciting candidates for cellular repopulation and repair in intervertebral disc degeneration (IDD). Our purpose is to investigate the interaction between MSCs and nucleus polposus cells (NPCs) and to determine viability of MSC in the intervertebral disc (IVD). Human NPCs and hMSCs were co-cultured in pellet system at different ratios. Proteoglycans were measured and normalized with DNA content. Histological analysis were also performed. Rabbit MSCs from bone marrow were trasduced with LacZ reporter gene and were injected into a rabbit IVD. Rabbits were sacrificed postoperatively at 3, 6, 12 and 24 weeks. Histological analysis was performed. Co-culturing of hNPCs with hMSCs resulted in increases proteoglycans as compared with hNPCs alone. Histological examination of the injected IVDs revealed presence of MSCs without apparent decrease in numbers or diminishment of protein production at 3, 6, 12 and 24 weeks. The data from this study show that there is a synergistic effect between MSCs and NPCs resulting in upregulated proteoglycan synthesis in-vitro. MSC remain viable and continue to express an ex-vivo transduced protein for up to 24 weeks. These results suggest that MSCs can survive in the harsh environment of the IVD and may favourably modify ECM production

Rotator cuff tears are a common cause of shoulder pain and dysfunction. Therefore, the purpose of this in-vitro biomechanical study was conducted to determine the effects of simulated tears and subsequent repairs of the rotator cuff tendons on joint kinematics. Eight paired fresh-frozen cadaveric shoulder specimens (mean age: 66.0 ± 8.7 years) were tested using a custom loading apparatus designed to simulate unconstrained motion of the humerus. Cables were sutured to the rotator cuff tendons and the deltoid. Loads were applied to the cables based on variable ratios of electromyographic (EMG) data and average physiological cross-sectional area (pCSA) of the muscles. An electromagnetic tracking device (Flock of Birds, Ascension Technologies, VT) was used to provide real-time feedback of abduction angle, to which the loading ratio was varied correspondingly. 2 and 4cm tears were made starting at the rotator cuff interval and extending posteriorly. Specimens were randomised to receive either single or double suture anchor repair. In order to quantify repeatability, five successive tests on each of the intact, torn, and repaired cases were performed. Statistical significance was established using One- and Two-way Repeated Measured ANOVAs (p< 0.05). Rotator cuff tears caused alteration in glenohumeral kinematics. A 2cm tear caused the humerus to consistently move posterior through the arc of abduction; however, as the tear increased to 4cm the humerus moved anteriorly, returning towards the intact state. Double row suture anchor repairs more accurately reproduced the kinematics of the intact specimen compared to single row suture anchor repair. The initial posterior displacement in the plane of elevation with the sectioning of the supraspinatus is related to the diminished anterior moment on the glenohumeral joint. As the tear proceeds into the infraspinatus, the anterior and posterior forces become more balanced and a return to near normal intact kinematics was observed. This study demonstrates that double row suture anchor repair more accurately reproduces active shoulder kinematics of the intact shoulder specimens

Introduction: In hereditary multiple exostosis (HME) the synthesis of the polysaccharide heparan sulphate (HS) is disrupted. HS-proteoglycans are low affinity receptors involved in fibroblast growth factor signaling. Activation of FGF receptor 3 (FGFr3) on mature chondrocytes leads to growth attenuation rather than stimulation. We tested the hypothesis that in HME chondrocytes with absent or reduced HS-PG synthesis there is impaired response to the FGFr3 ligand and loss of control of chondrocyte proliferation. Materials and methods: Chondrocytes were harvested from normal growth plate (epiphyseodesis) or HME osteochondroma cartilage cap obtained as surgical discard and cultured to 70% confluence in growth media. Cells were re-plated for experimentation. Growth curves were obtained for cells over a period of 5 days. In addition proliferative responses of healthy and HME chondrocytes were determined after low serum synchronization followed by challenge with FGF 9 (10 and 100ng/ml) and incorporation of BrdU for 2hours every two hours over a twenty eight hour period. Using these techniques it is possible to describe in detail the time dependent entry of cells into S-phase of the cell cycle and compare cell lines and treatment. Results: Significant differences were observed in the growth characteristics over a five-day period (p< 0.05). Under baseline growing conditions the chondrocytes derived from osteochondroma had a more rapid doubling time when compared with the normal growth plate chondrocyte (2.6+/− 0.6 vs 4.9+/−1.0, p< 0.05). In response to incubation with FGF-9 cells from normal growth plate have a lower peak proportion of cells entering the s-phase than with media alone (7% vs 25%). This inhibition is not observed in chondrocytes from osteochondroma. Conclusions: It would appear that osteochondroma chondrocytes are resistant to the normal regulatory effect of FGF-9 on cell proliferation. The differential response to FGF may be responsible for the growth differences observed both in-vitro and in-vivo

A load cell, capable of measuring medial and lateral loads independently, was used to evaluate current methods of ligamentous balancing in total knee arthroplasty. Ten cadaveric knees were randomized with the surgeons blinded or unblinded to the load cell’s output. Before ligament resection, there were differences between medial and lateral forces (p< 0.05). Balance improved in both groups following ligamentous releases. There was a trend for superior balance (medial-lateral compressive force) with load cell feedback provided: 30°(11.1 vs. 44.4N), 60°(7.1 vs. 36.9N), and 90°(3.0 vs. 8.7N). Further in-vivo studies with this device may improve load transfer and the longevity of TKA. The purpose of this study was to employ a tibial load cell to assess current methods of ligamentous balance during total knee arthroplasty, and to determine whether the load cell can improve load distribution between the medial and lateral compartments. Current methods achieve imperfect load balance, however this may be improved with the assistance of an intra-operative load cell. Intra-operative assessment and quantification of load balance with a load cell may improve the longevity of TKA. TKA was performed on five pairs of cadaveric knees which were randomly assigned into one of two groups based upon whether the surgeons were blinded or unblinded to the load cell’s output. A validated tibial load cell, capable of measuring medial and lateral loads independently, was inserted. Compartment forces were recorded at discrete flexion angles prior to ligamentous balancing and again after soft tissue balancing with final components cemented into position. Initially, there were significant differences between the loads in the medial and lateral compartments (p< 0.05). With soft tissue release, there was improved balance. There was a trend for superior balance (medial minus lateral compressive force) in the unblinded group at 30°: 11.1N unblinded vs. 44.4N blinded, 60°: 7.1 vs. 36.9N, and 90°: 3.0 vs. 8.7N. Failure to achieve ligamentous balance results in instability and unequal load distribution. Current balancing techniques are not perfect, but appear to be improved with the use of the load cell. Further in-vitro and in-vivo studies are needed to improve the load distribution following TKA

Purpose: The purpose of this study was to determine the effect of serial olecranon resections on elbow stability. Method: Eight fresh, previously frozen cadaveric arms underwent CT scanning. The specimens were mounted in an in-vitro motion simulator, and kinematic data was obtained using an electromagnetic tracking system. Simulated active and passive flexion was produced with servo-motors and pneumatic pistons attached to specific muscles. Flexion was studied in the dependent, horizontal, varus, and valgus positions. Custom computer navigation software was utilized to guide serial resection of the olecranon in 12.5% increments. A triceps advancement repair was performed following each resection. Results: Serial olecranon resections resulted in a significant increase in valgus-varus (V-V) laxity for both passive (p< 0.001) and active (p=0.04) flexion. For passive motion this increase reached statistical significance following the 12.5% resection. This corresponded to an increase in V-V laxity of 1.4 ± 0.1o and a total laxity of 7.5 ± 1.0o. For active flexion this increase reached significance following the 62.5% resection. This corresponded to an increase in V-V laxity of 5.6 ± 1.1o and a total laxity of 11.2 ± 1.5. There was no significant effect of sequential olecranon excision on elbow kinematics or stability with the elbow in the vertical or horizontal positions. The elbows became grossly unstable after resection of greater than 75% of the olecranon. Conclusion: A progressive increase in the varus-valgus laxity of the elbow was seen with sequential excision of the olecranon. Laxity of the elbow was increased with excision of 75% of the olecranon, likely due to the loss of the bony congruity and attachment site of the posterior band of the medial collateral ligament. Gross instability resulted when 87.5% or greater was removed, likely due to damage to the anterior band of the medial collateral ligament as it inserts on the sublime tubercle of the ulna. Rehabilitation of the elbow with the arm in the dependant position should be considered following excision of the olecranon; varus and valgus orientations should be avoided. The contribution of the olecranon to elbow stability may be even more important in patients with associated ligament injuries or fractures of the elbow