Biphasic calcium phosphate (BCP) with a characteristic needle-shaped submicron surface topography (MagnetOs) has attracted much attention due to its unique bone-forming ability which is essential for repairing critical-size bone defects such as those found in the posterolateral spine. Previous in vitro and ex-vivo data performed by van Dijk LA and Yuan H demonstrated that these specific surface characteristics drive a favorable response from the innate immune system. This study aimed to evaluate and compare the in vivo performance of three commercially-available synthetic bone grafts, (1) i-FACTOR Putty®, (2) OssDsign® Catalyst Putty and (3) FIBERGRAFT® BG Matrix, with that of a novel synthetic bone graft in a clinically-relevant instrumented sheep posterolateral lumbar spine fusion (PLF) model. The novel synthetic bone graft comprised of BCP granules with a needle-shaped submicron surface topography (MagnetOs) embedded in a highly porous and fibrillar collagen matrix (MagnetOs Flex Matrix). Four synthetic bone grafts were implanted as standalone in an instrumented sheep PLF model for 12 weeks (n=3 bilateral levels per group; levels L2/3 & L4/5), after which spinal fusion was determined by manual palpation, radiograph and µCT imaging (based on the Lenke scale), range-of-motion mechanical testing, and histological and histomorphological evaluation. Radiographic fusion assessment determined bilateral robust bone bridging (Lenke scale A) in 3/3 levels for MagnetOs Flex Matrix compared to 1/3 for all other groups. For µCT, bilateral fusion (Lenke scale A) was found in 2/3 levels for MagnetOs Flex Matrix, compared to 0/3 for i-FACTOR Putty®, 1/3 for OssDsign® Catalyst Putty and 0/3 for FIBERGRAFT® BG Matrix. Fusion assessment for MagnetOs Flex Matrix was further substantiated by histology which revealed significant graft resorption complemented by abundant bone tissue and continuous bony bridging between vertebral transverse processes resulting in bilateral spinal fusion in 3/3 implants. These results show that MagnetOs Flex Matrix achieved better fusion rates compared to three commercially-available synthetic bone grafts when used as a standalone in a clinically-relevant instrumented sheep PLF model.
Recent clinical data suggest improvement in the fixation of tibia trays for total knee arthroplasty when the trays are additive manufactured with highly porous bone ingrowth structures. Currently, press-fit TKA is less common than press-fit THA. This is partly because the loads on the relatively flat, porous, bony apposition area of a tibial tray are more demanding than those same porous materials surrounding a hip stem. Even the most advanced additive manufactured (AM) highly porous structures have bone ingrowth limitations clinically as aseptic loosening still remains more common in press-fit TKA vs. THA implants. Osseointegration and antibacterial properties have been shown In this At 4 weeks, a 42% increase in average pull-out shear strength between nanotube treated specimens and non-nanotube treated specimens was shown. A 21% increase in average pull-out shear strength between nanotube treated specimens and hydroxyapatite-coated specimens was shown. At 12 weeks, all specimens had statistically similar pull-out values. Bone labels demonstrated new bone formation into the porous domains on the materials as early as 2 weeks. A separate These
The prevention of surgical-site infection (SSI) is of great importance. Airborne particulate correlates with microbial load and SSI. There are many potential sources of airborne particulates in theatre and from an experimental point of view impossible to control. We evaluated the effectiveness of a novel air decontamination-recirculation system (ADRS) in reducing airborne particles in a laboratory environment and controlled the introduction of particulate using diathermy. Airborne particles were measured with and without activation of the ADRS in PC2 laboratory to provide a baseline. Particles were generated in a controlled manner utilising electrocautery ablation of porcine skin tissue. Ablation was performed at 50W power (Cut) for 60 seconds at a constant rate with and without the ADRS operating in the PC2 laboratory. Particles were measured continuously in 30s intervals at two sites 0.5m and 3m from the site of diathermy. Adequate time was allowed for return to baseline between each repetition. Each experiment was repeated 10 times.Aim
Methods
Calcium sulfate and phosphate have a long clinical history of use as bone-void fillers (BVF) with established biocompatibility and resorption profiles. It has been widely reported that the addition of ‘impurity’ elements such as Silicon, Strontium and Zinc to calcium phosphate is advantageous, resulting in an improved bone healing response. This study examined the in vivo response of two formulations of calcium sulfate, as 3mm diameter hemispherical beads, in critical sized defects created in cancellous bone of distal femur and proximal tibia (10mm diameter × 13mm depth) in adult sheep; beads prepared from recrystallised pharmaceutical grade calcium sulfate (RPCS, Stimulan, Biocomposites Ltd, UK) and a lower purity medical grade material containing 1% strontium (SrCS). The animals were sacrificed at 3, 6 and 12 weeks post implantation and the surgical sites analysed using microCT and decalcified histology.Background
Methods
Cementless devices can be designed with varying surface treatments with the hope of achieving osseointegration. The surface finish dictates the interaction, adhesion and growth of bone therefore it is an important parameter that be measured and compared. The surface topography of a material can be viewed both microscopically and macroscopically. Surface microtopography focuses on the peaks and valleys where deviations in the characteristics of the size and spacing of these features determine the variability between surface topography. The most common parameter used worldwide to describe surface roughness is the arithmetic average height (Ra). The definition of Ra is the absolute deviation of the surface irregularities from a mean line across the sampling length given by the equation shown in figure 1. Many techniques can be used to relate to surface characteristics of materials, with the common two options revolving around contact and non-contact methods. These techniques are expensive and are limited in detecting the interaction of implantable devices at a macroscopic level. This study sought to develop a method to determine the surface roughness and characterise implants based on cross sectional images and scanning electron microscopy. The profile of 6 trunnions from a total hip replacement was obtained in x and y coordinates along a set length using a profilometer. A custom program to calculate the Ra of the material was created using a mathematical program (MATLAB). Each material profile was inputted into a mathematical program to provide the surface roughness of the material. The surface parameters were initially obtained from a surface analyser to determine the accuracy of the program.Introduction
Method
Biological fixation of arthroplasty devices through osseointegration via ingrowth or ongrowth can be achieved with a numerous surface treatments and technologies. Surface roughness and topography have evolved to include sintered bead, calcium phosphate coatings and more recently additive manufacturing techniques. Regardless of the technique employed, the clinical goal has always been directed at improving osseointegration and achieve rapid, stable and long-term implant fixation without compromising the mechanical properties of the device. Pre-clinical models provide insight into the in-vivo efficacy. The in vivo results of a wide range of technologies over the past 20 years have been examined by our laboratory using an adult ovine cortical and cancellous implantation model. This paper will present a twenty year experience of pre-clinical evaluation of bone ingrowth and ongrowth surfaces used for arthroplasty device fixation. The endpoints as well as understanding of the dynamic nature of the bone-implant interface continues to evolve as advanced manufacturing moves forward and the demands on the interface due to patient and surgeon expectations increase.
Modern hip replacements all have encapsulated the design concept of proximal modularity. The factors contributing to the increased wear and corrosion at the taper junction are trunnion geometry, surface characteristics, head size, impaction forces, and material coupling. This study maps the inferior and superior region of the trunnion and bore to provide a visual identification of the corrosion severity. The corrosion/wear generated inferiorly and superiorly at the bore and trunnion will be quantified to understand how corrosion is affected by mechanical stresses in relation to anatomical orientation. Three neck tapers generated from bar stock containing a threaded trunnion Ti-6Al-4V and 3× 32mm femoral heads (Co-Cr-Mo) with a +4 offset manufactured by Signature Orthopaedics were used within this study. Rectangular Rozzette strain gauges (Tokyo Sokki Kenkyujo Co., Ltd.) were adhered onto the inferior and superior sections of the neck section. The tapers were fatigued in accordance to ISO 7206 at 5Hz for 5 million cycles at 37 degrees Celsius in phosphate buffered saline. The tapers were sectioned from the center of the femoral head to split both trunnion and bore into superior and inferior components. SEM imaging of all surface areas for each component, per taper (4) was done under ×100 magnification. The images were used to quantify the corrosion present across the surface area using a MATLAB based program called Histomorph. To obtain a visual observation of the variation of corrosion across the bore and trunnion the proximal, medial, and distal regions were mapped together for both the superior and inferior sections.Introduction
Methodology
The possibility of corrosion at the taper junction of hip replacements was initially identified as a concern of generating adverse reactions in the late 1980s. Common clinical findings of failure are pain, clicking, swelling, fluid collections, soft tissue masses, and gluteal muscle necrosis identified intra operatively. The joint replacement surgery was performed utilizing a posterior approach to the hip joint. The data from all surgical, clinical and radiological examinations was prospectively collected and stored in a database. Patients were separated into two groups based on bearing material, where group 1 had a CoC bearing and ABG modular stem whilst group 2 had a MoM bearing and SROM stem, with each group having 13 cases. Pre-operative revision surgery and post-operative blood serum metal ion levels we collected. Cup inclination and anteversion was measured using the Ein-Bild-Roentgen-Analyse (EBRA) software. A range of 2–5 tissue sections was examined per case. 2 independent observers that were blinded to the clinical patient findings scored all cases. The tissue grading for the H&E tissue sections were graded based on the presence of fibrin exudates, necrosis, inflammatory cells, metallic deposits, and corrosion products. The corrosion products were identified into 3 groups based on visible observation and graded based on abundance. A scanning electron microscope (SEM) Hitachi S3400 was used to allow for topographic and compositional surface imaging. Unstained tissue sections were used for imaging and elemental analysis. X-Ray diffraction was the analytical technique used for the taper debris that provided identification on the atomic and molecular structure of a crystal.Introduction
Methodology
Bone marrow stimulation has been a successful treatment option in cartilage repair and microfracture was the procedure of choice since the late 1980s. Despite its success in young and active patients, microfracture has inherent shortcomings such as shallow channels, wall compression, and non-standardized depth and diameter. This in vitro study assessed bone marrow access comparing microfracture, 1 and 2mm K-Wires, 1mm drill, and a recently introduced standardized subchondral bone needling procedure (Nanofracture) that creates 9mm deep and 1mm wide channels. An adult ovine model was used to assess access to bone the marrow spaces as well as effects on bone following microfracture, nanofracture, K-wire, and drilling following ethical clearance. All bone marrow stimulation techniques were conducted on a full thickness articular cartilage defect on the medial femoral condyles by the same surgeon. The same groups were repeated in vitro in 4 paired ovine distal femurs. MicroCT (Inveon Scanner, Siemens, Germany) was performed using 3D reconstruction and 25 micron slice analysis (MIMICS, Materialise, Belgium).Introduction
Methods
A thorough understanding of wear patterns and failure mechanisms of TKA components in the context of pre-revision knee kinematics is advantageous for component designers, manufacturers and surgeons alike. Traditional gait analysis provides an experimental technique to determine in vivo kinematics but is often limited by its cumbersome nature, infrastructure intensiveness and time. The recent introduction of the KneeKG (Emovi Inc, Canada) as a stand-alone knee motion tracking system which uses infrared technology provides a great opportunity to quickly, easily and routinely monitor patients at the clinical level, especially those being revised for component failure. This pilot study was conducted to examine pre-revision knee kinematics and subsequent wear patterns and failure mechanisms observed on the UHMWPE inserts upon retrieval in a cohort of TKA revision patients. We hypothesize that motion patterns can provide surgeons a unique insight into the status of the UHMWPE insert and implant longevity. Patients requiring revision due to failure of the UHMWPE insert were recruited in this study after institutional ethical approval and written informed consent of the patients was obtained. Motion of the affected knee was quantified using a stand-alone infrared tracking system (KneeKG, Emovi Inc, Canada) whilst the patient was walking on a treadmill. All analyses were conducted within our institutional Physiotherapy Department. The KneeKG system is composed of passive motion sensors fixed on a validated knee harness, an infrared motion capture system (Polaris Spectra, Northern Digital Inc, USA) and a computer equipped with the Knee3D software suite (Emovi). Following application of the KneeKG trackers a calibration procedure was performed to identify joint centres and define a coordinate system on each body segment. After a treadmill habituation period of between 6 and 10 min, a trial was then conducted at the patient's comfortable treadmill gait speed over 45 sec. Averaged clinical rotations and translations of the tibia as a function of gait cycle were output by the system, and a report highlighting and detailing biomechanical deficiencies as compared to a database of normal controls automatically generated. Following the scheduled revision surgery the retrieved components were formalin-fixed and brought to our laboratory for a routine retrieval workup. All revisions were performed by a single surgeon. Components were analysed using optical and scanning electron microscopy techniques for regions of polishing, burnishing, pitting, delamination, deformation, scratching and embedded debris. Wear maps and scores were generated and correlated with pre-revision kinematics for each patient.Introduction
Methods
Biological fixation through bone ingrowth and ongrowth to implants can be achieved with a variety of surface treatments and technologies. This study evaluated the effect of two different three dimensional surface coatings for CoCr where porosity was controlled through the use of different geometry of CoCr beads in the sintering process. Test specimens in Group A were coated with conventional spherical porous-bead technology. The porous coating technology used on Group B was a variation of the conventional porous-bead technology. Instead of spherical beads, cobalt-chromium particles in irregular shapes were sieved for a particular size range, and were sintered onto the specimen substrate using similar process as Group A. The geometry and the size variation of the particles resulted in a unique 3D porous structure with widely interconnected pores. Three implants were placed bicortically in the tibia. Two implants were placed in the cancellous bone of the medial distal femur and proximal tibia bilaterally with 4 implantation conditions (2 mm gap, 1 mm gap line-to-line, and press fit). Animals were euthanized at 4 or 12 weeks for standard mechanical, histological and histomorphometric endpoints.Introduction
Methods
Timing for the application and use of fentanyl patches for pre-emptive analgesia and sedation is crucial to obtain good clinical outcomes. Placement and timing is important to maximise clinical effect and apparent levels of analgesia. The use of sheep as preclinical models for the investigation of orthopaedic conditions is gaining momentum, the control of their pain is a significant ethical issue. The daily need for injecting non-steroidal anti-inflammatory drugs (NSAIDs) and/or the shorter acting opioids increases the demand for handling post-operatively which can increase animal distress and risk of human injury. NSAIDs can have a negative effect on bone healing, complicating results. Opioid analgesics have no impact on bone healing. Fentanyl patches have become another option for use in pain management. Pre-emptive analgesia helps reduce the demand on post-operative analgesic use. Fentanyl has the added benefit of producing mild sedation. This study evaluated the pharmacokinetics of fentanyl patches in sheep in an effort to maximise pre and post-surgical analgesia.Summary
Introduction
Supercritical fluid (SCF) sterilization produces clean and osteoconductive allograft bone capable of healing a critical-sised bony defect. SCF treated graft induces an increased anabolic response and decreased catabolic reponse compared to gamma irradiated graft. Clinically, allogeneic bone graft is used extensively because it avoids the donor site morbidity associated with autograft. However, there are concerns over the optimal sterilization method to eliminate immunological risks whilst maintaining the biological efficacy of the graft. This study compared the effect of Supercritical fluid (SCF) sterilization and gamma irradiation on the osteoconductivity of allograft bone in a bilateral critical-sised defect rabbit model.Summary Statement
Introduction
An autologous thrombin activated 3-fold PRP, mixed with a biphasic calcium phosphate at a 1mL:1cc ratio, is beneficial for early bone healing in older age sheep. The management of bone defects continues to present challenges. Upon activation, platelets secrete an array of growth factors that contribute to bone regeneration. Therefore, combining platelet rich plasma (PRP) with bone graft substitutes has the potential to reduce or replace the reliance on autograft. The simple, autologous nature of PRP has encouraged its use. However, this enthusiasm has failed to consistently translate to clinical expediency. Lack of standardisation and improper use may contribute to the conflicting outcomes reported within both pre-clinical and clinical investigations. This study investigates the potential of PRP for bone augmentation in an older age sheep model. Specifically, PRP dose is controlled to provide clearer indications for its clinical use.Summary Statement
Introduction
Demineralised bone matrix augmented tendon-bone fixations in the animal model show less scar tissue and an enthesis morphology closer to the physiologic one which may lead to a more resistant repair construct. Rotator cuff repair is one of the most common operative procedures in the shoulder. Yet despite its prevalence recurrent tear rates of up to 94% have been reported in the literature. High failure rates have been associated with tendon detachment from bone at the tendon – bone interface. Exogenous agents as biological strategies to augment tendon – bone healing in the shoulder represent a new area of focus to improve patient outcomes. Demineralised bone matrix (DBM) contains matrix bound proteins, exposed through acid demineralization step of DBM manufacture, and has long been recognised for its osteoinductive and osteoconductive properties. We hypothesised that DBM administered to the bone bed prior to the reattachment of the tendon, will upregulate healing and result in enhanced tissue morphology that more closely resembles that of a normal enthesis. An established ovine transosseous equivalent rotator cuff model was used.Summary Statement
Introduction
In order to emulate normal knee kinematics more closely and thereby potentially improve wear characteristics and implant longevity the Medial Pivot type knee replacement geometry was designed. In the current study the clinical and radiographic results of 50 consecutive knee replacements using a Medial Pivot type knee replacement are reported; results are compared to the Australian Orthopaedic Associations National Joint Replacement Registry. The patients' data were crossed checked against the registry to see if they had been revised elsewhere. After a mean follow-up of 9.96 years results show that the Medial Pivot Knee replacement provides good pain relief and functional improvement according to KSS and Womac scores and on subjective patient questionnaires. There was one minor revision; insertion of a patella button at 6.64 years FU. There were no major revisions; all implants appeared to be well fixed on standard radiographic examination. While the revision rate for the Medial Pivot knee according to the Australia Joint Registry results is higher compared to all other types of knee replacements in the registry, and to what is reported in the literature on the medial pivot knee, it is not in the current series. Revision rate was similar to what is reported on in the literature, but after a longer follow-up period. However, long term follow-up is required to draw definitive conclusions on the longevity of this type of implant.
Mechanical stabilization following periprosthetic fractures is challenging. A variety of cable and crimping devices with different design configurations are available for clinical use. This study evaluated the mechanical performance of 5 different cable systems in vitro. The effect of crimping device position on the static failure properties were examined using a idealized testing set up. Five cable systems were used in this study; Accord (Smith & Nephew), Cable Ready (Zimmer), Dall-Miles (Stryker), Osteo Clage (Acumed) and Control Cable (DePuy). Cables were looped over two 25 mm steel rods. Cable tension was applied to the maximum amount using the manufactures instrumentation. Devices were crimped by orthopaedic surgeon according to instructions. Crimping device/sleeve was secured in two different positions; 1. Long axis in-line with the load; 2. Long axis perpendicular to the load (Fig 1). Four constructs were tested for each cable system at each position. All constructs were tested following equilibration in phosphate buffered saline at 37 degrees Celsius using a servohydraulic testing machine (MTS 858 Bionix Testing Machine, MTS Systems) at a displacement rate of 10 mm per minute until failure. The failure load, stiffness and failure model (cable failure or slippage) was determined for all samples. Data was analysed using a two way analysis of variance (ANOVA) followed by a Games Howell post hoc test. One sample of each cable – crimping construct was embedded in PMMA and sectioned to examine the crimping mechanism.Introduction
Materials and Methods
The use of polymethyl methacrylate based cement for the fixation of joint replacements although commonly applied, is still limited by interfacial weakness. This study aims to document the effects of a variety of surface treatments on implant/cement bonding and link them to their surface properties. Thirty seven femoral implant analogues of Ti6Al4V rods were given one of six different surface treatments: traditional grit blasting, wet and dry Vaquasheening, acid etching in concentrated sulphuric and hydrochloric acid, anodisation at 150V, and a combination of acid etching and anodisation, before being embedded into a commercially available poly(methyl methacrylate) bone cement. The interfacial strength, energy and stiffness were measured through pushout testing. Surface analysis included examination with scanning electron microscopy, wettability tests and roughness analysis. Results were analysed with a one-way ANOVA with post hoc tests. Overall, the coarse blasted surface created the strongest interface, followed by both etched then anodised, acid etched only, wet Vaquasheened, anodised only and finally dry vaquasheened. While anodised samples showed a weaker bond than etched samples, the combination of etching and anodisation was not different to etching alone. In addition, six different types of interface failure modes were observed, and theories as to explain their mechanism, using experimental evidence were outlined. Coarse blasted surfaces showed the strongest bonding, while other surface modifications may encourage tissue ingrowth and other biological responses, these surface treatments do not strengthen bonding for cemented fixation.
Loading of the implant/cement bond during polymerization is possible when a joint is put through passive range of motion shortly after implantation. This may adversely affect the integrity of the cement – implant interface. The aim of this study was to evaluate the effect of implant motion during cement polymerization on the mechanical properties of the cement – implant interface. Simulated titanium tibial trays (15 mm dial tray, 15 mm keel) were used in this study and implanted in cellular rigid polyurethane foam (12.5 pcf) (Sawbones Vashon, WA, USA). Surface roughness (Ra) of implants was verified as 3.60μm with a 2μm tip at 0.5 mm/s over a length of 1.6 mm (SurfAnalyzer, MAHR Federal Inc., Providence, RI, USA). Palacos cement (Heraeus Medical, Wehrheim, Germany) was mixed for 2 minutes followed by implantation and one of 3 motion regimes at two time points. Six groups were tested. Motion was applied at three minutes for three groups. This motion was 1)axial micromotion for 20 cycles at 100 microns and 0.5 Hz, 2)rotational of 20 cycles at +/− 1.5 degrees and 0.5 Hz, or 3)both motions sumultaneously. An additional three groups were tested at 6 minutes under the same conditions. Motion was applied using calibrated mechanical testing equipment (MTS systems, Eden Prarie, MN, USA). Implants were tested in tension to failure at 0.5 mm/min, 24 hrs after implantation. The peak load, stiffness and energy were determined for each sample. Data was analysed using an Analysis of Variance and a Games Howell post hoc tests where appropriate.Introduction
Methods
Appropriate, well characterized animal models remain essential for preclinical research. This study investigated a relevant animal model for cancellous bone defect healing. Three different defect diameters of fixed depth were compared in both skeletally immature and mature sheep. This ovine model allows for the placement of four confined cancellous defects per animal. Defects were surgically created and placed in the cancellous bone of the medial distal femoral and proximal tibial epiphyses (See Figure 1). All defects were 25 mm deep, with defect diameters of 8, 11, and 14 mm selected for comparison. Defects sites were flushed with saline to remove any residual bone particulate. The skeletally immature and mature animals corresponded to 18 month old and 5 year old sheep respectively. Animals were euthanized at 4 weeks post-operatively to assess early healing. Harvested sites were graded radiographically. The percentage of new bone volume within the total defect volume (BV/TV) was quantified through histomorphometry and μ-CT bone morphometry. Separate regions of interest were constructed within the defect to assess differences in BV/TV between periosteal and deep bone healing. Defect sites were PMMA embedded, sectioned, and stained with basic fuschin and methylene blue for histological evaluation.INTRODUCTION
METHODS
Surgical drill-bits are used in a raft of procedures, from trauma, joint reconstruction to Arthroplasty. Drilling of bone is associated with the conversion of mechanical work energy into shear failure of bone and heat generation, causing a transient rise in temperature of hard and soft tissues. Thermal insults above 47°C sustained for one minute or more may cause osteonecrosis, reduced osteogenic potential, compromise fixation and influence tolerances with cutting blocks. Drill design parameters and operational variables have marked effects on cutting performance and heat generation during drilling. Dulling and wear of the cutting surfaces sustained through repeated usage can significantly reduce drill bit performance. Deterioration of cutting performance substantially increases the axial thrust force required to propel the cutting face through bone, compromising surgeon control during drilling and increasing the likelihood of uncontrolled plunging, cortical breakthrough and improper placement of holes as well as other jigs. The drilling accuracy and skiving of 2.8 mm 3-fluted SurgiBit (Orthopedic Innovation (OI), Sydney, Australia) (Figure 1) was compared with a standard 2-fluted drill (Synthes) at 15, 30 and 45 degrees using a 4th generation Sawbone as well as bovine cortical bone. A surgical handpiece was mounted in a servo-hydraulic testing machine and the motion of the drill-bit confined to 2 degrees of freedom. The lateral force and skiving distance was measured (n=6 per drill per angle per testing medium). A new drill was used for each test. Wear performance over multiple drilling episodes (1, 10 and 100) was performed in bovine cortical bone. The surface characteristics of the cutting faces of the drills were assessed optically at 10x magnification and at higher magnifications (50, 100 and 500x) using an environmental electron microscope.Introduction
Methods
Implant contamination prior to cement application has the potential to affect the cement-implant bond. the consequences of implant contamination were investigated Fifty Titanium alloy (Ti-6Al-4V) dowels were prepared with two surface finishes comparable to existing stems. The roughness (Ra and Rq) of the dowel surface was measured before and after the pushout test. Four contaminants (Phosphate Buffered Saline (PBS), ovine marrow, ovine blood, olive oil) were prepared and heated to 37°C. Each contaminant was smeared on the dowel surface completely and uniformly approximately 4 minutes prior to implantation. Samples were separated into ten groups (n=5 per group) based on surface roughness and contaminant. Titanium alloy dowels was placed in the center of Polyvinyl chloride (PVC) tubes with bone cement, and equilibrated at 37°C in PBS for 7 days prior to mechanical testing. The push out test was performed at 1 mm per minute. The dowel surface and cement mantel were analyzed using a Scanning Electron Microscopy (SEM) to determine the distribution and composition of any debris and contaminates on the surface.Introduction
Methods
Cementless prosthesis is one of the major bone-implant interface fixation methods in total joint replacement. Grit blasted surface, hydroxyapatite coated surface and plasma sprayed metallic porous coating have been popularly used. The latter has demonstrated higher bone implant mechanical stability in previous laboratory study in early and middle stages. However, question remains what the mechanism is to make it performing better and how to improve them further. This study is designed to examine the mode of failure in bone-implant interface in a sheep model. Plasma sprayed porous coated (TiPL); hydroxyapatite (HA) coated and and grit blasted (TiGB) titanium implants were examined in the study. Each type has 36 specimens. Implants were inserted into cortical bones in a press-fit fashion in a total of 22 sheep bilateral hind limbs. Specimens were retrieved at 4 weeks and 12 weeks. Push- out testing was performed to just reach ultimate failure. Failed bone-implant interface were investigated by histology and BSEM. The percentage of failure at bone-coating interface, bone itself fracture, coating itself failure, and coating-substrate dissociation were measured by BSEM.Aim
Method
This study was performed to compare the mechanism of bone-implant integration and mechanical stability among three popularly used cementless implant surfaces. Plasma sprayed porous surface (TiPL), grit-blasted rough surface (TiGB), and hydroxyapatite coated implant surface (HA) were tested in a sheep model at 4 and 12 weeks. The integration patterns were investigated using histology, histomorphometry, and mechanical strength by push-out test. All three groups demonstrated early bone ongrowth on their surfaces, with much of the ongrowth resembling contact osteogenesis. TiPL group showed bone anchorage into porous coating with new bone ingrowth into the pores. HA group revealed small cracks at its coating at 12 weeks time point. Plasma sprayed porous surface also demonstrated its superior mechanical stability maybe reinforced by its bone anchorage, whearas, HA surface exhibited higher osteoconductivity with highest ongrowth rate.
Post-arthroscopic glenohumeral chondrolysis (PAGCL) is a rare, but significant, complication of arthroscopic shoulder surgery that may lead to arthroplasty. Exact causal factors and pathways associated with the development of PAGCL are unknown however a number of patient factors and surgical factors have been implicated. Suture is one of these potential causal factors and currently little is known about the body's immune response to commonly used orthopaedic sutures. The aim of this project is to examine the biological response to 3 commonly used orthopaedic sutures (Ethibond, Fibrewire, and Orthocord) in a murine airpouch model. It was hypothesised that different sutures would elicit a different histological response and that suture wear-debris would induce an increased inflammatory reaction compared to intact suture. Total of 50 male Wister rats (12 weeks old) were used in this study. 5 rats were used per time point per group. Rat air-pouch was created according to a protocol previously described by Sedgewick et al. (1983). Once the pouch was established, on day 6, an incision was made and one of the test materials (intact Ethibond, intact Orthocord, intact Fibrewire, Fibrewire wear-debris) administered. Following wound closure, 5 ml of sterile PBS was injected to suspend the implanted materials. Negative control animals were injected with PBS alone. Rats were sacrificed at 1 and 4 weeks following surgery. The entire pouch was harvested and processed for H&E histology. The images of histological stained sections were digitally photographed and evaluated for presence of synovium and inflammatory reaction. Foreign body giant cells were quantified by two independent, blinded observers.Introduction
Methods
Initial stability of the tibial component influences the success of uncemented total knee arthroplasty. In uncemented components, osseointegration provides long-term fixation which is particularly important for the tibial component. Osseointegration is facilitated by minimising bone-implant interface micromotion to within acceptable limits. To investigate initial stability, this study compares the micromotion and initial seating of two uncemented hydroxyapatite-coated tibial components, the Genesis II and Profix. This is the first stability comparison of two hydroxyapatite-coated tibial components. Six components of each type were implanted into synthetic tibias by a single orthopaedic surgeon. Good coverage was achieved. No screws or articular inserts were used. Initial seating was measured using ImageJ software at five areas on each tibia. Tibias were transected and their proximal section implanted into a molten alloy parallel to horizontal. Dynamic mechanical testing was performed using a hydraulic 858-Bionix machine. Prostheses underwent unilateral axial point-loading of 700N cyclically applied four times. The load was applied to three locations approximating femoral loading points. The loading cycle was repeated six times at each point, allowing micromotion to be recorded at three contralateral locations. Micromotion was measured by optical lasers. After dynamic testing, two tibial components of each type were removed with claw pliers while measuring the force required on the 858-Bionix machine. Implant under-surfaces were photographed for wear.Introduction
Methods
Gamma Irradiation is often considered the gold standard for sterilizing bone allograft. However, a dose dependant decrease in the static mechanical properties of gamma irradiated bone has been well established. Supercritical Fluid Sterilization (SCF) using carbon dioxide represents a potential alternate method to sterilize allografts. This study aimed to evaluate the effect of SCF on the static and dynamic (fatigue) properties of cortical bone in 3-point bending. Eighty paired 18-month old rabbit humeri were randomized to 4 treatments: Gamma Irradiation at 10 kGy or 25 kGy, SCF Control and SCF with Peracetic Acid (Introduction
Methods
The reduction of intraoperative blood loss during total knee arthroplasty (TKA) and total hip arthroplasty (THA) and even organ resection is an important factor for surgeons as well as the patient. In order to cauterize blood vessels to stop bleeding diathermy is commonly used and involves the use of high frequency and induces localized tissue damage and burning. Saline-coupled bipolar sealing RFE technology however has been shown to reduce tissue carbonization, however the dosage effects of RFE are not well known for both bone and soft tissue. This study examined sealing progression of blood vessels using a range of energy levels of saline-coupled bipolar RFE on bone and various soft tissues in a non-survival animal study. Following institutional ethical approval, three mature sheep were used to examine the cancellous bone of the femoral trochlear groove and soft tissue (liver, kidney, lung, pancreas and mesentry peritoneum) subjected to the following treatment regime varying by watts and time: (1) untreated control, (2) 50 W for 1 sec, 2 sec, 3 sec and 5 sec, (3) 140 W for 1 sec, 2 sec, 3 sec and 5 sec and (4) 170 W for 1 sec, 2 sec, 3 sec and 5 sec. The Aquamantys™ System Generator and hand piece (Salient Surgical Technologies, Inc, Portsmouth, NH) coupled to a saline (0.9% NaCl) drip was used to apply RFE to the various tissues. Two clinical diathermy settings were used as controls. Tissues were immediately harvested, fixed in 10% buffered formalin and prepared for routine paraffin histology. Stained sections were evaluated in a blinded fashion for the acute in vivo response.Introduction
Materials and Methods
Edge loading commonly occurs in all bearings in hip arthroplasty. Edge loading wear can occur in these bearings when the biomechanical loading axis reaches the edge and the femoral head loads the edge of the cup producing wear damage on both the head and cup edge. When the biomechanical loading axis passes through the polished articulating surface of the acetabular component and does not reach the edge, the center of the head and the center of the cup are concentric. The resulting wear known as concentric wear is low in metal-on-metal (MOM) bearings, and is negligible in ceramic-on-ceramic (COC) bearings. Edge loading is well defined in COC hip bearings. However, edge loading is difficult to identify in MOM bearings, since the metal bearing surfaces do not show wear patterns macroscopically. The aims of this study are to compare edge loading wear rates in COC and MOM bearings, and to relate edge loading to clinical complications. Twenty-nine failed large diameter metal-on-metal hip bearings (17 total hips, 12 resurfacings) were compared to 54 failed alumina-on-alumina bearings collected from 1998 to 2011. Most COC bearings were revised for aseptic loosening or periprosthetic bone fracture, while most MOM bearings were revised for pain, soft tissue reactions or impingement. The median time to revision was 3.2 years for the metal hip bearings and 3.5 years for alumina hip bearings. The surface topography of the femoral heads was measured using a RedLux AHP (Artificial Hip Profiler, RedLux Ltd, Southampton, UK).Introduction
Materials and Methods
In patients with conventional metal-on-Polyethylene (MoP) hip replacements, osteolysis can occur in response to wear debris. During revision hip surgery, surgeons usually remove the source of osteolysis (polyethylene) but cannot always remove all of the inflammatory granulomatous tissues in the joint. We used a human/rat xenograft model to evaluate the effects of polyethylene granuloma tissues on bone healing. Human osteoarthritic and periprosthetic tissues collected during primary and revision hip arthroplasty surgeries were transplanted into the distal femora of athymic (nude) rats. The tissues were assessed before and after implantation and the bone response to the tissues was evaluated after 1 week and 3 weeks using micro-computed tomography, histology, and immunohistochemistry. After 3 weeks, the majority (70%) of defects filled with osteoarthritic tissues healed, while only 21% of defects with polyethylene granuloma tissues healed. Polyethylene granuloma tissues in trabecular bone defects inhibited bone healing. Surgeons should remove polyethylene granuloma tissues during revision surgery when possible, since these tissues may slow bone healing around a newly implanted prosthesis. This model provides a method for delivering clinically relevant sized particles into an
The need for regeneration and repair of bone presents itself in a variety of clinical situations. The current gold standard of treatment is autograft harvested from the iliac crest or local bone. Inherent disadvantages associated with the use of autogenous bone include limited supply, increased operating time and donor site morbidity. This study utilized a challenging model of posterolateral fusion to evaluate the in vivo response of an engineered collagen carrier combined with nano-structured hydroxyapatite (NanOss Bioactive 3D, Pioneer Surgical) compared to a collagen porous beta-tricalcium phosphate bone void filler (Vitoss BA, Orthovita). A single level posterolateral fusion was performed in 72 adult rabbits at 6, 12 and 26 weeks (8 per group per time point). Group 1: nanOss Bioactive 3D + bone marrow aspirate (BMA) + autograft, Group 2: Vitoss BA + BMA and Group 3: Autograft + BMA were compared were compared using radiographic (X-ray and Micro-computed tomography (μCT), biomechanics (manual palpation and tensile testing at 12 and 26 weeks) and histology.Introduction
Materials and Methods
The marriage of rapid prototyping technologies with Arthroplasty has resulted in the fabrication and use of cutting jigs and guides which are tailored to a patients' individual anatomy. These disposable cutting blocks are designed based on input parameters obtained from pre-operative CT and MRI scans and manufactured using 3-D printers. Indirect benefits include a reduction in inventory and a decrease in the burden for central sterilising units. This approach is advantageous for the surgeon in the attainment of ideal mechanical alignment, which is known to be associated with an improved clinical outcome and implant longevity. This study evaluated the postoperative alignment parameters from a single surgeon series of patients following TKA with the Signature (Biomet) system. The postoperative alignment of a single surgeon series of 60 consecutive patients receiving a Vanguard cruciate retaining TKR (Biomet) using the Signature patient-specific surgical positioning guides was performed. Postoperative CT and preoperative templating MRI scans were imported into Mimics 14.0 (Materialise, Belgium) where specific bony landmarks were identified in both data sets. A subset of these points was used to transform the MRI data into the CT coordinate frame to enable the computation of femoral mechanical alignment in the absence of a full-length lower limb CT scan. CT and transformed MRI landmarks were then imported into ProEngineer (PTC, MA) where angular measurements were made by projecting axes onto anotomical planes. Flexion, rotation, valgus/varus of the femoral component and posterior slope, rotation and valgus/varus of the tibial component were computed. Femoral rotation was referenced to the trans-epicondylar axis as opposed to Whiteside's line. Overall limb alignment was determined based on individual component position.Introduction
Methods and Materials
The purpose of this study was to understand the effects of terminal sterilisation and residual calcium on human demineralised bone matrix (DBM) in ectopic bone formation in nude rat. The intramuscular implantation of human DBM prepared by the Queensland Bone Bank (QBB) from four donors into eight male athymic rats was used to assess osteoinductivity. The DBM contained different levels of residual calcium and treated with or without gamma-irradiation at 11kGy. At 6 weeks post-implantation, calcium deposition was assessed by manual palpitation and radiological imaging. Tissue morphology and cellular interactions was analysed using various histological staining methods whilst protein expression of anabolic and catabolic biomarkers were examined through immunohistochemistry. All results were then analysed in qualitative, semi-quantitative and quantitative manners and tested for statistical significance. Bone formation was observed in all specimens at the gross level. This was confirmed by histology which revealed bony capsules surrounded by soft tissue in the muscle pockets and differences in tissue components. On a cellular level, variations in osteoclast expression were found between the two groups as well as amongst individual donors through statistical analysis which resulted in an imbalance of the expression of anabolic and catabolic markers. Furthermore, a positive relationship between residual calcium and new bone formation in gamma irradiated DBM samples was found. To date, no studies have compared the effect of calcium in gamma irradiated DBM. Our results suggest that gamma irradiation even at low doses and residual calcium may affect new bone formation. Taken together, this study stresses the importance of selecting ideal conditions for graft processing and the need to identify an optimal level of irradiation and remaining calcium levels that confers a balance between osteoinductivity and sterility.
Edge loading commonly occurs in all bearings in hip arthroplasty. The aim of this study compares metal bearings with edge loading to alumina bearings with edge loading and to metal bearings without edge loading. Seventeen failed large diameter metal-on-metal hip bearings (8 total hips, 9 resurfacings) were compared to 55 failed alumina-on-alumina bearings collected from 1998 to 2010. The surface topography of the femoral heads was measured using a chromatically encoded confocal measurement machine (Artificial Hip Profiler, RedLux Ltd.). The median time to revision for the metal hip bearings and the alumina hip bearings was 2.7 years. Forty-six out of 55 (84%) alumina bearings and 9 out 17 (53%) metal bearings had edge loading wear (p<0.01). The average volumetric wear rate for metal femoral heads was 7.87 mm3/yr (median 0.25 mm3/yr) and for alumina heads was 0.78 mm3/yr (median 0.18 mm3/yr) (p=0.02). The average volumetric wear rate for metal heads with edge loading was 16.51 mm3/yr (median 1.77 mm3/yr) and for metal heads without edge loading was 0.19 mm3/yr (median 0 mm3/yr) (p=0.1). There was a significant difference in gender, with a higher ratio of females in the alumina group than the metal group (p=0.02). Large diameter metal femoral heads with edge loading have a higher wear rate than smaller alumina heads with edge loading. Metal-on-metal bearings have low wear when edge loading does not occur.
Shape memory staples have several uses in both hand and foot and ankle surgery. There is relatively little data available regarding the biomechanical properties of staples, in terms of both the compression achieved and potential decay of mechanical advantage with time. An understanding of these properties is therefore important for the surgeon. Two blocks of synthetic polyurethane mimicking properties of cancellous bone were fixed in jigs to both the actuator and 6 degree-of-freedom load cell of an MTS servohydraulic testing machine. With the displacement between the blocks held constant the peak value and subsequent decay in compressive force applied by both the smooth and barbed version of the nitinol OSStaple (Biomedical Enterprises), Easyclip (LMT), Herbert Bone Screws (Martin) and the Headless Compression Screw (Synthes) was measured. Nitinol staples were energised once only. A second experiment was conducted to assess the effects of repeated energisation on these parameters. The Easyclip staples achieved a mean peak force of 5.2N, whilst the smooth and barbed OSStaples achieved values of 9.3N and 5.7N, respectively. The Herbert screws achieved a mean peak force of 9N and the headless compression screws 23.9N. The mean peak force achieved with 2 Easyclip staples in parallel was 8.1N. Following the application of a single energisation the OSStaples exhibited a significant reduction in compressive load, losing up to approximately 70% of the peak value attained. The repeated energisation of these nitinol staples produced progressive increases in both peak and trough loads, the positive effects exhibited a plateau with time. Performance of both OSStaples was comparable to the Herbert screw with regard to reduction load applied across a simulated fracture plane. The maximum load applied by the OSStaples diminished with time. Staples provide fixation without violating the fracture plane which has the potential to offer some benefits from a healing perspective.
To set up an osteosarcoma mouse model with spontaneous lung metastasis and to identify a marker of osteosarcoma metastasis and to inhibit the marker against the invasive ability of an osteosarcoma cell line. A human osteosarcoma orthotopic mouse model was set up by injecting 143B human osteosarcoma cells into mouse tibia. Type I insulin-like growth factor receptor (IGF-1R) and its downstream signalling factors were measured in samples from the primary tumor and the lung secondaries by immunohistochemistry. Human Alu mRNA expression was tested using in situ hybridization assay. A Matrigel assay was used to assess cell invasion ability under the interference of a MEK/ERK pathway specific inhibitor, U0126. All fifteen mice showed tumour mass at the left tibia and lung metastasis. Human Alu expression in the primary and secondary tumours confirmed human origin of the tumour cells. Total IGF-1R, MEK, Akt, p38 and phosphorylated MEK (p-MEK), but not p-Akt and p-p38, were positive in both local tumours and lung secondaries. Leiomyosarcoma controls expressed p-Akt and p-MEK, but not p-p38. The 143B cells treated with U0126 had significantly lower in vitro invasion ability compared with controls. The IGF-1R-MEK signalling pathway, particularly Ras/Raf/MEK/ERK, may play an important role in osteosarcoma lung metastasis, and the targeting MEK/ERK by its specific inhibitor may have a potential use in the effective treatment of osteosarcoma.
Animal studies examining tendon-bone healing have demonstrated that the overall structure, composition, and organization of direct type entheses are not regenerated following repair. We examined the effect of Low-Intensity Pulsed Ultrasound (LIPUS) on tendon-bone healing. LIPUS may accelerate and augment the tendon-bone healing process through alteration of critical molecular expressions. Eight skeletally mature wethers, randomly allocated to either control group (n=4) or LIPUS group (n=4), underwent rotator cuff surgery following injury to the infraspinatus tendon. All animals were sacrificed 28 days post surgery to allow examination of early effects of LIPUS. Humeral head – infraspinatus tendon constructs were harvested and processed for histology and immunohistochemical staining for BMP2, Smad4, VEGF and RUNX2. All the growth factors were semiquantitative evaluated. T-tests were used to examine differences which were considered significant at p < 0.05. Levene's Test (p < 0.05) was used to confirm variance homogeneity of the populations. The surgery and LIPUS treatment were well tolerated by all animals. Placement of LIPUS sensor did not unsettle the animals. Histologic appearance at the tendon-bone interface in LIPUS treated group demonstrated general improvement in appearance compared to controls. Generally a thicker region of newly formed woven bone, morphologically resembling trabecular bone, was noted at the tendon-bone interface in the LIPUS-treated group compared to the controls. Structurally, treatment group also showed evidence of a mature interface between tendon and bone as indicated by alignment of collagen fibres as visualized under polarized light. Immunohistochemistry revealed an increase in the protein expression patterns of VEGF (p = 0.038), RUNX2 (p = 0.02) and Smad4 (p = 0.05) in the treatment group. There was no statistical difference found in the expression patterns of BMP2. VEGF was positively stained within osteoblasts in newly formed bone, endothelial cells and some fibroblasts at the interface and focally within fibroblasts around the newly formed vessels. Expression patterns of RUNX2 were similar to that of BMP-2; the staining was noted in active fibroblasts found at the interface as well as in osteoblast-like cells and osteoprogenitor cells. Immunostaining of Smad4 was present in all cell types at the healing interface. The results of this study indicate that LIPUS may aid in tendon to bone healing process in patients who have undergone rotator cuff repair. This treatment may also be beneficial following other types of reconstructive surgeries involving the tendon-bone interface.
Treatment of large segmental defects in the extremities is challenging. A segmental tibial defect model in a large animal can provide a basis through which in vivo testing of materials and techniques for use in non-unions and severe trauma cases can be examined. This study reports such a model. Six aged ewes (> 5 years) were used following ethical approval. A 5cm piece of the mid diaphysis of the left tibia was removed including its associated periosteum. The tibia was stabilized with an 8mm stainless steel cross locked intramedullary nail and all tissues closed in their respective layers. Animals were euthanised at 12 weeks following surgery and evaluated using radiographic, micro-computed tomography (CT), soft tissue and hard tissue histology techniques. Three weeks post operatively one of the intramedullary nails failed through the first of the distal two cross locking screw holes, the sheep was euthanised and the tibia was harvested. Early signs of callus formation were evident at the osteotomy edges originating from the periosteal surface; the defect space was bridged by fibrous scar tissue. The remaining 5 sheep were taken out to the 12 week time point then all relevant tissues were harvested. Gross dissection revealed a lack of bony union in the defect site and no evidence of infection. X-rays and CT showed a lack of hard tissue callus bridging in the defect region at 12 weeks. Histological sections of the bridging tissues revealed, callus originating from both the periosteal and endosteal surfaces, with fibrous tissue completing the bridging in all instances. One case had cartilaginous tissue developing; however this was incomplete at 12 weeks. As none of the 12 week time point sheep achieved clinical union; this model may be effective as a basis for the investigation of healing adjuncts to be used in non-union cases, where severe traumatic injury has lead to significant bone loss such as blast injuries or following large tumour removal.
Two types of ceramic materials currently used in total hip replacements are third generation hot isostatic pressed (HIPed) alumina ceramic (commercially known as BIOLOX®forte, CeramTec) and an alumina matrix composite material consisting of 75% alumina, 24% zirconia, and 1% mixed oxides (BIOLOX®delta, CeramTec). The aim of this study is to compare BIOLOX delta femoral heads to BIOLOX forte femoral heads revised within 2 years in vivo. Ceramic bearings revised at one center from 1998 to 2010 were collected (61 bearings). BIOLOX delta heads (n=11) revised between 1–33 months were compared to BIOLOX forte femoral heads with less than 24 months in vivo (n=20). The surface topography of the femoral heads was measured using a chromatically encoded confocal measurement machine (Artificial Hip Profiler, RedLux Ltd.). The median time to revision for BIOLOX delta femoral heads was 12 months, compared to 13 months for BIOLOX forte femoral heads. Sixteen out of 20 BIOLOX forte femoral heads and 6 out of 11 BIOLOX delta femoral heads had edge loading wear. The average volumetric wear rate for BIOLOX forte was 0.96 mm3/yr (median 0.13 mm3/yr), and 0.06 mm3/yr (median 0.01 mm3/yr) for BIOLOX delta (p=0.03). There was no significant difference (p>0.05) in age, gender, time to revision or femoral head diameter between the two groups. Early results suggest less volumetric wear with BIOLOX delta femoral heads in comparison to BIOLOX forte femoral heads.
In order to prepare hamstring autograft, suture fixation to the tendon is required to secure and handle the tendon during harvest and preparation. We use a simple, grasping suture which doesn't require suture of the tendon, thus saving time and avoiding violation of the graft itself. We present this technique, with results of mechanical testing compared to a standard whip suture, traditionally used to handle hamstring autograft. Twelve uniform ovine flexor tendons were prepared. A number two braided polyester suture was used in all cases. Six tendons were prepared with a standard, non-locking whip-suture, maintaining uniformity of suture bite and working length between samples. Six tendons were prepared with the utility suture, also taking care to maintain uniformity. The suture was applied by tying the thread around the tendon with a single-throw granny knot then symmetrically wrapping the suture ends from proximal to distal and securing with another single throw, allowing compression of the tendon with longitudinal tension on the suture. All the samples were tested to failure in uniaxial tension in a materials testing machine. Peak load values and load/displacement curves were acquired and results analysed with a two-sample T-test assuming significance at P<0.05.Introduction
Methods and materials
Fibrocartilaginous entheses are formed through endochondral ossification and characterized by four zones morphologically separated into tendon, uncalcified fibrocartilage, calcified fibrocartilage and bone [1]. These zones are not successfully regenerated following surgical repair. Demineralized Bone (DBM) presented at the tendon bone interface may improve healing between tendon and bone. Fifty six female nude rats were randomly allocated into either a control reconstruction or treatment group (DBM at the tendon-bone healing site). A modified rodent model of anterior cruciate ligament reconstruction was adopted [2]. Animals were sacrificed at 2, 4 and 6 weeks following surgery. Four rats per group were prepared for histology at each time point while eight rats were culled for biomechanical testing at 4 and 6 week time points. ANOVA and post hoc tests were used to examine differences which were considered significant at p < 0.05. The surgical procedure was well tolerated. Macroscopic dissection did not reveal any infection and all joint surfaces appeared normal. An intra-articular graft between the femur and tibia was present in all specimens. Mechanical differences were noted between groups. Peak loads were significantly higher in treatment group at 4 and 6 weeks (6.0 ± 3.6N and 9.1 ± 2.6 N, respectively) compared to controls (2.9 ± 1.9 N and 5.8 ± 2.7 N). No statistical differences were found in graft stiffness between the groups at 4 or 6 week time points. Histology showed an initial influx of inflammatory cells coupled with formation of a loose disorganized fibrovascular interface layer between tendon and bone in both groups. By the 6 weeks the interface layer in the DBM group fused into the newly formed bone to create a continuum between the tendon and bone, in an interdigitated fashion, containing Sharpy's like fibres. In the control group the continuum was less apparent with evidence of large areas of discontinuity between the two zones. A thicker region of newly formed woven bone with increased osteoblast activity along the bone tunnel was evident in the DBM group. DBM has the potential to increase the quality of repair following surgical procedures involving reattachment of tendon to bone.
The role of porosity in the longevity of polymethylmethacrylate (PMMA) bone cement mantles remains unclear, although porosity reduction is probably desirable. It is not known whether pore patterns, pore distribution or pore morphology contribute to failure, since it is difficult to assess these features with traditional techniques. We used a novel microtomographic technique to quantitatively and qualitatively assess porosity in PMMA cements of differing viscosities to establish whether pore distribution can be effectively assessed and to document any differences in porosity (in both quantity, distribution and morphology). Each cement was also examined with and without the addition of vacuum, since this is thought to reduce porosity. Four PMMA bone cements of different viscosities (three of the same brand and the fourth chosen due to its popularity) were prepared and moulded according to established protocols (ASTM F451-99a), with and without the addition of vacuum. 25 samples per group (200 total) were prepared and densities for each sample calculated using Archimedes' principle. Four samples per group (total 32) were randomly selected for further analysis. These samples underwent micro-computer tomography (micro-CT) at a magnification of 20× and slice thickness of 13.67μm and reconstructed images were analysed with in-house developed software to measure pore size and volume. Results were analysed and compared with the two-sample T-test assuming significance at P<0.05. Qualitative assessment of pore character and distribution was made using three dimensional (3D) reconstruction.Introduction
Methods and materials
The diagnosis and treatment of disorders of the long head of the biceps tendon remains controversial. There is uncertainty as to the role of the long head of biceps and it can be difficult to determine whether the patient's pathology is coming from the biceps or other adjacent structures. In addition, the appropriate type of treatment remains controversial. We retrospectively reviewed the files of the senior author's experience in over 4000 arthroscopic shoulder procedures. We examined cases involving isolated biceps pathology, excluding those patients with rotator cuff tears and labral pathology, involving 92 biceps tenotomies and 103 biceps tenodeses. Our analysis supports the benefit of clinical examination over all types of radiological investigations. The benefits and technique of biceps tenodesis is described including surgical technique. Irritation by PLA interference screw is examined. A paradigm is put forward to help in diagnosis and management of these lesions. Long head of biceps pathology is a significant cause of shoulder pain in association with other shoulder problems and in isolation. Biceps tenodesis and tenotomy is an efficacious way of dealing with this pathology.
Thermal damage to bone related to the exothermic polymerisation of bone cement (PMMA) remains a concern. A series of studies were conducted to examine PMMA bone interface during cemented arthroplasty. In vitro and in vivo temperature distributions were performed in the laboratory and human and animal surgery. In vivo (10 patients) measurements of cement temperature during cementing of BHR femoral prosthesis using thermocouples. Intra-operative measurement of cement temperature in BHR in the presence of femoral head cysts was examined in patients. The BHR femoral heads were sectioned to assess cement mantle as well as position of thermocouples. An additional study was performed in sheep with PMMA implanted into cancellous defects. Thermocouples were used to monitor temperature in the cement as well as adjacent bone. Histology and CT was used to assess any thermal damage. The exothermic reaction of PMMA during polymerization does indeed result in an increase in temperature at the interface with bone. The in vivo study recorded a maximum temperature of 49.12C for approximately three minutes in the cancellous bone underneath the BHR prosthesis. This exposure is probably not sufficient to cause significant injury to the femoral head. The maximum temperature of the cement on the surface of the bone was 54.12C, whereas the maximum recorded in the cement in the mixing bowl was 110.2C. In the presence of artificial cysts within the bone, however, temperatures generated within the larger cysts, and even at the bone-cement interface of these cysts, reached levels greater than those previously shown to be harmful to bone. This occurred in one case even in the 1 cc cyst. Routine histology revealed a fibrous layer at the cement bone interface in the sheep study. Fluorescent microscopy demonstrated bone label uptake adjacent to the defect site. Histology did not reveal thermal necrosis in the defects in terms of bony necrosis. CT data was used to measure the amount of PMMA placed into each defect. This analysis revealed a range of volumes that did not seem to influence the histology. The heat of cement polymerisation in resurfacing as performed in our study is not sufficient to cause necrosis. This may reflect the ability of the body to rapidly conduct heat away by acting as a heat sink. The temperature-conducting properties of the metal prosthesis are also likely to be important.
Posterolateral spinal fusion using autograft in adult rabbits has been reported by many groups using the Boden model. Age in general has an adverse effect on skeletal healing; although, its role in posterolateral fusion is not well understood. This study examined the influence of animal age on spinal fusion using a standard model and experimental endpoints. We hypothesised that fusion quality and quantity would be less with increasing age. A single level posterolateral fusion between the fifth and sixth lumbar segments were performed in six-month and two-year-old New Zealand white rabbits (n=6 per group) using morcelized iliac crest autograft. All animals were sacrificed at 12 weeks following surgery. Posteroanterior Faxitron radiographs and CT scans were taken and DICOM data was analysed (MIMICS Version 12, Materialise, Belgium). Axial, sagittal, coronal and three-dimensional models were created to visualise the fusion masses. Bone mineral density (BMD) of the fusion mass was measured using a Lunar DPXL Dexa machine. An MTS Bionix testing machine was then used to assess peak load and stiffness. Sagittal and coronal plane histology was evaluated in a blinded fashion using H&E, Tetrachrome and Pentachrome stains. Assessment included overall bony response on and between the transverse processes. Radiographs and CT confirmed a more robust healing response in younger animals. Radiographic union rates decreased from 83% to 50% in the aged animals. A neo- cortex surrounding the fusion mass was observed in the younger group but absent in the aged animals. Fusion mass BMD and that of the vertebral body was decreased in the older animals (P<0.05). Tensile mechanical data revealed a 30% reduction in peak load (P=0.024) and 34% reduction in stiffness (P=0.073) in the two-year-old animals compared with the six-month-old animals. Histological evaluation demonstrated a reduction in overall biological activity in the two-year-old animals. This reduction in activity was observed in the more challenging intertransverse space as well as adjacent to the transverse processes and vertebral bodies at the decortication sites. Numerous sites of new bone formation was present in the middle of the fusion mass in the six-month-old animals while the bone graft in the two-year- old animals were less viable. Skeletal healing is complex and mediated by both local and systemic factors. This study demonstrated that ageing leads to an impaired and delayed skeletal repair. Where autograft is utilised, diminished graft osteoinductivity and reduced levels of growth factors and nutritional supply in the surrounding milieu explains our observations. The aged rabbit posterolateral spinal fusion model has not been previously described but would be a useful to evaluate new treatment modalities in a more challenging host environment.
Cortical bone is a complex composite material composed of an inorganic mineral phase and organic matrix of type I collagen and various non-collagenous proteins. The hierarchical organisation of bone results in a transversely isotropic material with the mechanical properties in the long-axis (z) being superior to the radial and circumferential axes which are equivalent. This directional dependence of bone has been well reported, whilst the mechanisms/anisotropy are more difficult to study. This study examined the anistropic nature of cortical bone and the influence of different sterilisation procedures. Ninety cortical bone cubes were prepared using established techniques (Walsh and Guzelsu) and randomly allocated to three treatments; control, 15 KGy, Super Critical Fluid (SCF) (n=30 per group). The ultrasonic moduli was examined using longitudinal sound waves at 5 MHz using a pulse receive technique. Unconfined compression was performed non-destructively in longitudinal (z), circumferential (ï±) and radial orientations (r). Samples were tested to failure in the z axis. A two-way analysis of variance (treatment and time) followed by a Games Howell post hoc test and covariate analysis was performed using SPSS for Windows. Data from this study revealed some interesting and intriguing results with respect to the effects of gamma irradiation and dense gas technology on the properties of cortical bone and load transmission. A statistical decrease in the compressive stiffness and strength was noted with 15 KGy of whilst SCF treatment did not alter the properties in the r or ï orientations. Similar results were found with respect to the ultrasonic moduli (data not shown). The pilot data confirmed the adverse effects of bone in compression following gamma irradiation as we found in our recently presented ORS work. However, the study in compression demonstrated that the directional dependence that makes cortical bone a transversely isotropic material is removed following gamma irradiation with SCF did not appear to have this effect. The effects of gamma irradiation on the mechanical performance of allografts in the long bone axis may play a role in their in vivo performance. The removal of the anisotropy following gamma irradiation provides insight into the relationship(s) between the mineral and organic constituents, which requires further study.
The aim of this study was to compare the outcome of cemented TKR using either oxidized zirconium (oxinium) or cobalt chrome (CoCr) femoral components in patients undergoing simultaneous bilateral TKR. Patients involved in the study received one of each prosthesis, thereby acting as their own control. The hypothesis was that there would be no difference in the clinical and radiographic outcome between the two prosthetic materials. Forty consecutive patients who were undergoing bilateral Genesis ll TKR consented to participate in the study. Patients were assessed preoperatively, at five days, six weeks and one, two and five years, postoperatively. The outcome measures included the KOOS, Knee Society Score, BOA Patient Satisfaction Scale, and radiographs at six weeks and one, two and five years. In two patients polyethlylene exchange was performed at 56 months from surgery during patellofemoral resurfacing. The four retrieved polyethylene liners were studied for wear with the aid of a stereo zoom microscope and an environmental scanning electron microscope (ESEM). Both the patients and the all examiners were blinded as to the prosthesis type throughout the study. Forty patients (80 knees) were included in the study. At five years, three patients were deceased and two had developed senile dementia. No patients were lost to follow up. At five years from surgery the CoCr knee was preferred by 41% of patients compared to 13% who preferred the Oxinium knee (p=0.009). There was no significant difference in range of motion between the two prosthesis at five days, six weeks or one, two and five years. There were also no significant differences between the two prostheses in any of the other variables assessed. The four retrieved polyethylene inserts showed similar patterns of wear in terms of both wear types and patterns under examination with both the stereo zoom and scanning electron microscope with no clear differences between CoCr and Oxinium bearing against the polyethlylene. There was no difference in the grade or incidence of radiographic lucencies between the two prosthesis at five years. At five years after surgery the only significant difference between the Genesis II Oxinium prosthesis and the CoCr prosthesis was a subjective preference for the CoCr prosthesis by a higher proportion of patients. There were no unexpected complications associated with the use the Oxinium femoral implants. In the four retrieved polyethylene liners, no significant differences were identified between the two prosthesis materials in terms of detectable wear type and patterns. Continued follow up of this cohort is planned to establish whether Oxinium femoral implants have an improved survivorship compared to CoCr femoral component in total knee replacement to warrant the additional cost.
‘High flexion’ polyethylene tibial tray inserts are available from total knee replacement (TKR) manufacturers. There is currently no published data available that examines how much extra knee flexion these new implants give or if there are any wear consequences for the change in design. The high flexion inserts are narrower posteriorly than standard inserts and have chamfers anteriorly and on the post in cruciate sacrificing designs. This prospective randomised controlled trial of 100 patients undergoing posterior stabilised TKR compared knee flexion, measured intra-operatively by a computer navigation system, of the standard and high flexion trial inserts in the same knee. Patients were then randomised to receive either a standard or ‘high flexion’ definitive component and the stability assessed. The post-operative knee flexion of all patients was measured at six months. High flexion inserts did not give significantly more knee flexion than standard inserts either per-operatively at the trial insert stage, or at six months post-op and resulted in marginally more anterior draw. The average per-operative difference in flexion between standard and high flex inserts measured in the same knee was 3.2° (range -4-18°) The average knee flexion at 6 months post op was 106° for both groups. The average change in knee flexion comparing pre and post op was 2.3° for the high flex group and 0.6° for the standard insert group. Laboratory Tek scan contact pressure analysis at the surface of the standard and high flexion designs was not significantly different, but the thinner polyethylene of the high flexion design raises questions about wear characteristics. High flexion polyethylene inserts are probably not justified in terms of improved knee flexion, but may be a useful option in certain technical circumstances during TKR such as patella baja or if the patella impinges on the post in deep flexion.
We present a biomechanical cadaveric study investigating the effect of type II Superior Labrum Anterior Posterior (SLAP) lesions on the load-deformation properties of the Long Head of Biceps (LHB) and labral complex. We also report our assessment of whether repair of the type II SLAP lesion restored normal biomechanical properties to the superior labral complex. Using a servo-controlled hydraulic material testing system (Bionix MTS 858, Minneapolis, MA), we compared the load-deformation properties of the LHB tendon with: the LHB anchor intact; a type II SLAP lesion present; following repair with two different suture techniques (mattress versus ‘over-the-top’ sutures). Seven fresh-frozen, cadaveric, human scapulae were tested. We found that the introduction of a type II SLAP lesion significantly increased the toe region of the load deformation curve compared to the labral complex with an intact LHB anchor. The repair techniques restored the stiffness of the intact LHB but failed to reproduce the normal load versus displacement profile of the labral complex with an intact LHB anchor. Of the two suture techniques, the mattress suture best restored the normal biomechanics of the labral complex. We conclude that a type II SLAP lesion significantly alters the biomechanical properties of the LHB tendon. Repair of the SLAP lesion only partially restores the biomechanical properties. We hypothesise that repairs of type II SLAP lesions may fail at loads as low as 150N, hence the LHB should be protected following surgery.
The histology results implied a potential acceleration in the early stage of fracture healing in the high dose (75 μg) MB group. However progression to union following this initial early phase acceleration was delayed as callus volume increased rather than union according to micro CT and histological data.
