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
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
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
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 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
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 biological properties of morselised bone allograft treated with either a supercritical fluid process or low-dose (15 kGy) gamma irradiation were compared using radiological, histological and immunohistological techniques. The aims were to investigate any differences in the biological properties of supercritical fluid treated allograft and low-dose gamma irradiated allograft in-vivo. Rabbit allograft were cleaned of all soft tissue, cartilage and processed into ‘corticancellous crunch’ using a Noviomagus Bone Mill. Pooled samples were either gamma irradiated (15 kGy) or treated by NovaSterilis using super critical carbon dioxide. A well-reported tibial defect model in ten rabbits was used to examine the in vivo response of the different treatments at two and four weeks following surgery (n=5 per time point). Radiographic (x-ray, CT and micro CT), histology and immunohistochemistry was used to assess the in vivo response. Radiographic results revealed an initial response to the gamma-irradiated samples compared to SCF. Histology confirmed this reaction to be inflammatory in nature at two weeks that continued at four weeks for the gamma irradiated samples. In contrast, the SCF treated sample demonstrated new bone formation while the inflammatory reaction was muted compared to the gamma irradiated samples. Four week x-rays and histology confirmed new bone formation in both groups while the lack of significant inflammatory response in the SCF group was noted. Allograft sterilisation techniques do not result in the same initial response when evaluated in vivo. Removal of lipids and cellular debris following SCF treatment may influence the in vivo response. While both techniques can provide a sterile product, the in vivo response requires further investigation.
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.
Single level posterolateral spinal fusion in rabbits is the accepted preclinical model for evaluating bone graft substitutes or treatments to enhance/augment healing. This study aimed to improve preclinical testing by developing a multi-level unilateral fusion model that could be used as a screening tool prior to larger scale preclinical experiments. A four level unilateral posterolateral fusion was performed in nine animals. The materials were randomly allocated and placed between the decorticated surfaces of the transverse processes and vertebral bodies. Animals were euthanised at three, six and 12 weeks. The materials were (1) 25 kGy y-irradiated rabbit allograft chips (RAC), (2) SCF RAC, (3) 60% tri-calcium phosphate, 40% hydroxyapatite formagraft (BiOstetic) (4) Autograft (1.5 cc morsellised to 1-2.5 mm granules). The autograft was harvested from the iliac crest using the L5-L6 incision. Endpoints included x-ray, CT, micro CT and histology. The animals tolerated the surgery well. Radiographic data provided a useful method to differentiate between groups. Micro CT however was extremely valuable demonstrating new bone formation as early as three weeks across the groups. Gamma irradiated samples demonstrated an initial inflammatory reaction while the autograft, SCF allograft and synthetic TCP did not show this response. As expected, time was an important factor demonstrating the maturity in the fusions. These materials responded in a similar fashion in this model as observed in a single level fusion. A unilateral multi-level fusion can be performed in rabbits to provide a useful screening for different materials. Gamma irradiated allograft has an initial inflammatory reaction that may be related to the presence of residual cellular material whereas SCF and synthetic materials do not.
