Platelet-rich plasma (PRP) has been demonstrated to benefit a variety of disciplines. But there exists heterogeneity in results obtained due to lack of standardization of the preparation protocols employed in them. We aim to identify and standardize a preparation protocol for PRP with maximum recovery of platelets to obtain reproducible results across studies. Blood samples were collected from 20 healthy volunteers. The double spin protocol of PRP preparation was analyzed for variables such as centrifugal acceleration, time, and volume of blood processed and final product utilized. The final PRP prepared was investigated for platelet recovery, concentration, integrity, and viability. We noted maximum platelet recovery (86-99%) with a mean concentration factor of 6-times baseline, with double centrifugation protocol at 100xg and 1600xg for 20 minutes each. We also noted that 10 ml of blood in a 15 ml tube was the ideal volume of blood to be processed to maximize platelet recovery. We demonstrated that the lower 1/3rd is the ideal volume to be utilized for clinical application. We did not note a loss of integrity or viability of the platelets in the final product from the above-said protocol. Preparation of PRP by the double spin protocol of 10 ml of blood at 100xg and 1600xg for 20 minutes each in a 15ml tube and using the lower 1/3rd of the final product demonstrated consistent high platelet recovery (86-99%) and concentration (6x) without disturbing the platelet integrity or viability

Merriam Webster - ide•al adjective \ī-′dē(−ə)l, ′ī\: exactly right for a particular purpose, situation, or person. Dictionary.com. - 1: conceived as constituting a standard of perfection or excellence; 2: regarded as perfect of its kind; 3: existing only in the imagination; not real or actual. Concepts: Tissue Preserving - anterior and posterior capsule maintained: YES; No dislocation; Minimal leg manipulation; Rapid Rehabilitation: YES; Half the average LOS at NE Baptist; Safe: YES; Fewer complications than standard approach; Transferable and Reproducible ???; Limited adoption; Optimally executed with navigation; Leg length assessment less accessible; Neck cut measured from GT; “Funny looking” impactors/reamers - different “feel”. IDEAL: For some… but not for most

Introduction and Aims: C1 lateral mass screw fixation offers a powerful alternative biomechanical fixaion for upper cervical disorders. The anatomical constraints to this fixation have not been described yet and are essential to ensure avoidance of neurovascular damage. Method: Fifty patients (including five patients with rheumatoid arthritis) underwent upper cervical CT scans. Analysis of these CT scans involved use of calibrated scan measurements to identify the midpoint of the posterior lateral mass, the dimensions of the lateral mass, the direction of optimum screw passage, the position of the vertebral foramen at C1 and the ideal entry point for lateral mass screw fixation. Results: The average length of screw within the lateral mass was 20mm with 13.5mm of screw not in bone, behind the lateral mass, but necessary to allow rod placement posteriorly adjacent to other fixation points. The safest entry point was directly beneath the medial edge of the lamina origin. The ideal direction of screw angulation is parallel with the posterior arch, in the saggital plane. This entry point was on average 8.8mm from the vertebral artery foramen laterally and 5.8mm from the medial aspect of the lateral mass. Vertical space available for sublaminar screw placement was 3mm or less in 9% of lateral masses. Conclusion: C1 lateral mass screws are best placed beneath the lamina origin, parallel with the arch in the saggital plane using an entrypoint in line with the medial edge of the lamina origin. An entry point under the midpoint of the lamina origin, or passing through the lamina at its attachment to the lateral mass, is likely to damage the vertebral artery in a significant proportion of cases

Introduction: C1 lateral mass screw fixation offers a powerful alternative biomechanical fixation for upper cervical disorders. The anatomical constraints to this fixation have not been described yet and are essential to ensure avoidance of neurovascular damage. Methods: 50 patients (including 5 patients with rheumatoid arthritis) underwent upper cervical CT scans. Analysis of these CT scans involved use of calibrated scan measurements to identify the midpoint of the posterior lateral mass, the dimensions of the lateral mass, the direction of optimum screw passage, the position of the vertebral foramen at C1 and the ideal entry point for lateral mass screw fixation. Results: The average length of screw within the lateral mass was 20 mm with 13.5mm of screw not in bone, behind the lateral mass, but necessary to allow rod placement posteriorly adjacent to other fixation points. The safest entry point was directly beneath the medial edge of the lamina origin. The ideal direction of screw angulation is parallel with the posterior arch, in the saggital plane. This entrypoint was on average 8.8 mm from the vertebral artery foramen laterally and 5.8 mm from the medial aspect of the lateral mass. Vertical space available for sublaminar screw placement was 3mm or less in 9% of lateral masses. Discussion: C1 lateral mass screws are best placed beneath the lamina origin, parallel with the arch in the saggital plane using an entrypoint in line with the medial edge of the lamina origin. An entry point under the midpoint of the lamina origin, or passing through the lamina at its attachment to the lateral mass, is likely to damage the vertebral artery in a significant proportion of cases

Purpose: The purpose of this study was to examine how the “ideal” tibial nail insertion point varies with tibial rotation and to determine what radiographic landmarks can be used to identify the most suitable rotational view for insertion of a tibial intramedullary nail. Methods: Twelve cadaveric lower limb specimens with intact soft tissues around the knee and ankle joints were used. A 2.0mm Kirschner wire was placed in the center of the anatomic safe zone and centered on the tibial shaft. The leg was rotated and imaged using a fluoroscopic C-arm until the K-wire was positioned just medial to the lateral tibial spine (defined as the neutral anteroposterior radiograph). The leg was then fixed and radiographs were taken in 5 degree increments by rotating the fluoroscope internally and externally (in total, a 50 degree arc). Following this a second K-wire was placed in 5 mm increments both medially and laterally and the fluoroscope rotated until this second K-wire was positioned just medial to the lateral tibial spine. Radiographs were digitized for measurements. Results: Given the presence of a 30 degree rotational arc through which the radiograph appeared anteroposterior, it was possible to improperly translate the start point up to 15 mm. Relative external rotation of the image used for nail placement led to a medial insertion site when using the lateral tibial spine as the landmark. A line drawn at the lateral edge of the tibial plateau to bisect the fibula head correlated with an entry point that was central or up to 5 mm lateral to the ideal entry point. The use of a fibula head bisector line avoided a medial insertion point. Conclusions: Rotation of the tibia may result in up to 15 mm of translation of the start point that may be unrecognized. Relative external rotation of the film used for nail placement leads to medial insertion sites when using the lateral tibial spine as a landmark. The fibula head bisector line can be used to avoid choosing external rotation views and thus avoid medial insertion points

Introduction. Accurate alignment of components in total knee arthroplasty (TKA) is a known factor that contributes to improvement of post-operative kinematics and survivorship of the prosthetic joint. Recently, CAOS has been introduced into TKA in effort to reduce positioning variability that may deviate from the mechanical axis. However, literature suggests that clinical outcomes following TKA with CAOS may not present a significant improvement from traditional methods of implantation. This would infer that achieving correct alignment, alone, might be insufficient for ensuring an optimal reconstruction of the joint. Therefore, this study seeks to evaluate the importance of soft-tissue balancing, through the quantification of joint kinetics collected with intraoperative sensors, with or without the combined use of CAOS. Methods. Seven centers have contributed 215 patients who have undergone primary TKA with the use of intraoperative sensors. Of the 7 surgeons contributing patients to this study, 3 utilize CAOS; 4 utilize manual techniques. Along with standard demographic and surgical data being collected as per the multicenter study protocol, soft-tissue release techniques and medial-lateral intercompartmental loads—as indicated by the intraoperative sensors—were also captured pre- and post-release. “Optimal” balance was defined as a medial-lateral load difference of ≤ 15 lbs. A chi-squared analysis was performed to determine if the percentage of soft-tissue release was significantly different between the two groups: patients with CAOS, and patients without CAOS. Results. Of the 215 patients (35% with CAOS, 65% without CAOS) who have received TKA, using intraoperative sensors to assess mediolateral balance, 92.6% underwent soft-tissue release. Stratifying this data by surgical technique: 89% of the patients with CAOS, and 94% of patients without CAOS, were released. A chi-squared analysis—with 3 degrees of freedom; and 99% confidence—was executed to determine if the 5% difference between the two groups was significant. The analysis showed that there was no significant difference between the two groups, thus we can conclude that soft-tissue release is as equally necessary in the CAOS TKA group, as it is in the traditional TKA group. Discussion. It is widely accepted that correct alignment of TKA components contributes to improved kinematic function of the affected joint. Recently, technology has been developed to digitally guide surgeons through bony cuts, thereby decreasing the incidence of deviation from the mechanical axis. However, alignment may not be the foremost contributing factor in ensuring an optimal joint state. In this evaluation, 92.6% of the cohort required some degree of releasing of ligamentous structures surrounding the knee joint, regardless of intraoperative technique used. A chi-squared analysis of the data supports the claim that soft-tissue release is used in nearly all cases, irrespective of the use of CAOS (p < 0.001). This suggests that soft-tissue release is necessary in nearly all cases, even after appropriate alignment has been digitally verified. The data strongly supports the idea that obtaining an optimally functioning joint is multifactorial, and that alignment may play a more minor role in achieving ideal joint reconstruction than previously assumed, being superseded by the necessity to achieve soft-tissue balance

Economic data, clinical outcome studies, and anatomical studies continue to support the Superior Hip Approach as a preferred approach for improved safety, maximal tissue preservation, rapid recovery, and minimised cost.

Clinical studies show exceedingly low rates of all major complications including femur fracture, dislocation, and nerve injury.

Economic data from Q1 2013 to Q2 2016 demonstrate that CMS-insured patients treated by the Superior Hip Approach have the lowest cost of all patients treated in Massachusetts by an average of more than $7,000 over 90 days. The data show that the patients treated by the Superior Hip Approach have lower cost than any other surgical technique.

Matched-pair bioskills dissections demonstrate far better preservation of the hip joint capsule and short external rotators than the anterior approach.

Design principles include: Preservation of the abductors; Preservation of the posterior capsule and short external rotators; Preparation of the femur in situ prior to femoral neck osteotomy; Excision of the femoral head, thereby avoiding surgical dislocation of the hip; In-line access to the femoral shaft axis; Ability to perform a trial reduction; Independence from intra-operative imaging; Independence from a traction table; Applicable to at least 99% of THA procedures.

Cartilage is a realistic target for tissue engineering given the avascular nature and cellular composition of the tissue. Much of the work in this field has been largely empirical, indicating the need for alternative approaches to the design of cartilage formation protocols. Given the heterogeneity associated with human mesenchymal populations, continuous cell lines may offer an alternative to model and simplify cartilage generation protocols. We therefore exploited the potential of the murine chondrocytic ATDC5 cell line to, i) delineate the process of chondrocyte differentiation in monolayer culture and three-dimensional micromass pellet culture systems, and ii) model cartilage formation utilising appropriate scaffold and bioreactor (perfused and rotating) technologies. Monolayer cultures of ATDC5 cells over a 28-day period in presence of insulin demonstrated various stages of chondrocyte differentiation- proliferative, pre-hypertrophic, hypertrophic and finally, mineralisation of cartilaginous nodules. This was confirmed by gene and protein expression, by qPCR and Western blotting respectively, of chondrogenic differentiation markers- Sox-9, Bcl-2, Type II and X collagens. Pellet cultures of ATDC5 cells under chondrogenic conditions (10 ng/ml TGF-beta3, 1X ITS {insulin, transferrin, selenium}, 10 nanomolar dexamethasone, 100 micromolar ascorbate-2-phosphate) illustrated a gradual progression from an aggregation of cells at day 7, to initiation of matrix synthesis at day 14, followed by formation of well-defined cartilaginous structures at day 21. Chondrogenic differentiation at day 21 was evident by numerous proliferative/ pre-hypertrophic chondrocytes, staining for Sox-9, Aggrecan, Type II collagen and PCNA, lodged in distinct lacunae embedded in cartilaginous matrix of proteogly-cans and Type II collagen. Inclusion of TGF-beta3 in the chondrogenic medium during pellet culture beyond 21 days maintained the pre-hypertrophic phenotype, even at day 28. In contrast, removal of TGF-beta3, addition of 50 nanomolar thyroxine and reduction of dexa-methasone to 1 nanomolar in the chondrogenic medium stimulated hypertrophy at day 28, evident by down-regulation of Sox-9 expression. ATDC5 cells cultured on Polyglycolic acid fleece in the rotating bioreactor or encapsulated in chitosan /alginate and cultured in the perfused bioreactor for 21 days, formed cartilaginous explants reminiscent of hyaline cartilage. Thus, ATDC5 cells constitute an ideal cell line to elucidate the steps of chondrocyte differentiation and cartilage formation

Fractures of the hip are common, often occurring in frail elderly patients, but also in younger fit healthy patients following trauma. They have a significant associated mortality and major social and financial implications to patients and health care providers. Many guidelines are available for the management of these patients, mostly recommending early surgery for the best outcomes. As a result, healthcare authorities now put pressure on surgical teams to ‘fast track’ patients with a fracture of the hip, often misquoting the available literature, which in itself can be confusing and even conflicting.

This paper has been written following an extensive review of the available literature. An attempt is made to clarify what is meant by early surgery (expeditious versus emergency), and we conclude with a personal view for the practical management of these patients of variable age, fitness and type of surgery performed within services that are often under considerable pressure of finance and available operating theatres and qualified staff.

Cite this article: Bone Joint J 2016;98-B:1573–81.

We investigated the prognostic indicators for collagen-covered autologous chondrocyte implantation (ACI-C) performed for symptomatic osteochondral defects of the knee.

We analysed prospectively 199 patients for up to four years after surgery using the modified Cincinnati score. Arthroscopic assessment and biopsy of the neocartilage was also performed whenever possible. The favourable factors for ACI-C include younger patients with higher pre-operative modified Cincinnati scores, a less than two-year history of symptoms, a single defect, a defect on the trochlea or lateral femoral condyle and patients with fewer than two previous procedures on the index knee. Revision ACI-C in patients with previous ACI and mosaicplasties which had failed produced significantly inferior clinical results. Gender (p = 0.20) and the size of the defect (p = 0.97) did not significantly influence the outcome.

The Exeter Trauma Stem (ETS) is a monoblock unipolar prosthesis currently in use throughout various orthopaedic departments. It can be a useful procedure for specialty trainees in developing modern cementation techniques in hip arthroplasty. We propose that in order for this procedure to be a valid training tool that, as well as having a standardized surgical approach and operative technique, outcomes should be easily assessed and should be similar if performed by either a trainee or consultant.

All ETS procedures carried out at our institution from January 2009 until September 2011 were reviewed retrospectively. Patient demographics and operative details were recorded from patient notes. Radiographic evaluation involved the Barrack cementation grading system, Dorr's criteria, stem alignment and leg length measurement.

There was no significant difference in operative time between ETS performed by consultant or by specialty trainee. On postoperative x-ray, cement mantles were Barrack grade A or B in 55.6% (trainees) versus 61.9% (consultants). Stem alignment was neutral in 50% and varus in 50% of cases for trainees, versus 28.6% and 71.4% of cases for consultants. In total, 69.2 % of patients had lengthening of the operated limb with a mean increase of 10.4mm (2–25) for trainees and 9.3mm (2–18) for consultants.

Both trainees and consultants can attain a good cement mantle. However, from our results stem alignment is less accurate by trainees with half being placed in varus. Our results highlight the difficulty of obtaining correct leg length positioning with the ETS with trainees and consultants having similar discrepancies.

The ETS is a useful procedure for orthopaedic trainees to attain adequate skills in modern cementation techniques with similar post-operative radiographic outcomes to consultants. The tendency for trainees to be less accurate with stem positioning could be improved with supervision or careful pre-operative templating.

Several design principles were considered paramount when the surgical technique of performing total hip arthroplasty through an incision in the superior capsule without dislocation of the hip joint was developed. These design principles include: Preservation of the abductors; Preservation of the posterior capsule and short external rotators; Preparation of the femur in situ without dislocation of the hip; In-line access to the femoral shaft axis; Ability to perform a trial reduction; Independence from intraoperative imaging; Independence from a traction table; Applicable to at least 99% of THA procedures

Personal experience with more than 1950 THA using the superior capsulotomy technique over a 12-year period has demonstrated several observations: Dislocation rate of 0.15% (3 in 1950); Acute deep infection rate of 0% (0 in 1950); Universal applicability: used in 99.7% of primary THA; Lateral femoral cutaneous nerve palsy incidence: 0/1950; Femoral nerve palsy incidence: 0/1950; Transient peroneal palsy incidence: 2/1950; Length of stay (since 2010): 1.55 days; Discharge to home: 98%; 90-day cost (2/13 to 2/14) compared to other exposures in CMS patients in the same institution: $24,200 vs $30,100; Readmission costs (CMS 2/13 to 2/14) at 90 days: $0.

Conclusion: Performing total hip arthroplasty without dislocation and with preservation of the abductors, posterior capsule and short external rotations has proven to have a low dislocation rate, a low infection rate, and wide applicability. CMS 12-month expenditure data documenting ZERO dollars spent on readmission for any reason within 90 days of surgery demonstrates the potential for simultaneously improving incomes and reducing cost, with particular benefit within the CMS BPCI and private bundled payment programs.

The aim of our study was to assess the use of the Clavicular Hook Plate in treating acromio–clavicular joint dislocations and fractures of the distal clavicle. The prospective study was carried out at two hospitals- a teaching hospital and a district general hospital.

Between 2001 and 2004 a total of 37 patients with AC joint injuries and distal clavicle fractures were treated surgically with this device. Four of the patients had sustained a Neers Type 2 fracture of the distal clavicle, while 33 patients had acromio-clavicular joint dislocation (Rockwood Type 3 or higher). Mean age of the study group was 35.2 years. Post operatively, shoulder pendulum exercises were commenced on the second day and all patients discharged within 48 hours. During the first few weeks, we restricted shoulder abduction to 90 degrees. At the first postoperative follow up appointment at 2 weeks, average shoulder abduction was 30 degrees and forward elevation −40 degrees. This improved at 6 weeks to 85 degrees and 105 degrees respectively. The plates were removed at an average time interval of 11 weeks for the ACJ dislocations (range 8–12 weeks) and 15 weeks for the clavicle fractures (range 12–16 weeks). At three months after plate removal, we evaluated patients to measure the Visual Analogue Score(VAS) and Constant Score. The mean VAS was 1.4 (range 0–6) and the mean Constant score was 92 (range 72 to 98). Wound healing problems occurred in two patients, while two had a stress riser clavicle fracture. These had to be subsequently fixed with a Dynamic Compression Plate. One patient developed a superficial wound infection. Seven patients had problems due to impingement between the hook and the under surface of the acromion. A 45 year old female patient developed ACJ instability after plate removal. Radiographs revealed widening of the AC joint and some osteophyte formation. She went on to develop frozen shoulder which was treated with intensive physiotherapy.

The AO hook plate represents an improvement over previous implants in treating injuries around the AC Joint. However, the need for a second operation to remove the plate remains a significant problem. Complications resulting from impingement were common in our patients and represent a major drawback of this implant.

With Lord Darzi’s vision of the future of the NHS, it has become clear that quality of care will be the next focus and the hospitals providing acute orthopaedics and trauma services will have to deliver best and most efficient care for the patients being admitted with fractured neck of femur. This study is aimed at recognizing the changes and organization required at a district general hospital and their initial effect on the quality of services being provided locally.

Management of patient with hip fracture involves several specialties within the hospital as well as primary care setup. An audit of A& E waiting time showed significant variation in the delay before transferring the patients to the ward which was addressed by Fast-Track system. In the ward, preoperative assessment was standardized by agreement between orthopaedics and anaesthetics department. Three daytime lists were initiated specifically for hip fracture patients, resulting in increase in the number of patients going to theatre within 48 hours of admission, from 75% to 86%. A protocol was agreed between orthopaedic surgeons and rheumatologists for starting anti-resorptive therapy for these patients in order to decrease the chances of future fragility fractures. Impact of this measure will be assessed in due course. One senior middle grade surgeon was given the charge of managing NOF lists and to coordinate the medical management of these patients. Hospital has also started taking part in National Hip Fracture Database and a HCA has been assigned the duty of uploading the data to NHFD database. A acre pathway is being developed to streamline the whole peri-operative and after discharge management of these patients.

With just about a year left before the implementation of healthcare commissioning, it is vital that trusts start working on best and most efficient care for all patients. Hospital will have to publish their quality accounts from next year and their tariffs will be linked to patient reported outcome measures. This study highlights the main issues and the potentially vital role of orthopaedic specialists in developing the required services.

Introduction: We have previously described modification of Ti that renders the implant surface bactericidal and prevents bacterial colonization in vitro. This study evaluates the efficacy of the same surface in preventing periprosthetic infection in a small mammal model.

Methods: Control or VancTi rods were incubated with S. aureus (Ci=104CFU/mL) in TSB containing 0, 5×10-3, 4, or 100 μg/mL vancomycin at 37°C for 24h. Bacteria were detected by fluorescence (Live/Dead BacLight) and imaged by confocal microscopy. Resistance was tested by incubating control or VancTi rods with S. aureus for 0–8 weeks. Adherent bacteria were tested every 7 days on vancomycin screening agar (6μg/mL).

Results: Using a percutanous approach, the intercondylar region of the knee in rats were identified. The intrameduallry canal of the femur was retrograde reamed using an 18-gauge needle. Infection was induced by injection of 103 CFU S. aureus in 150uL of saline into the femoral canal followed by insertion of a 20 mm Ti implant. Animals were harvested at various time points. At harvest, animals were euthanized with CO2.. Detailed analysis including radiographic, micro-CT, histological, bacteriological, and clinical evaluation was performed.

Results: All animals showed signs of infection within the first few post-operative days with increased soft tissue swelling and limited mobility. At 1 week 75% of the animals showed radiographic signs of periprosthetic infection including periosteal reaction, abscess formation, widened canal, bone destruction, and formation of involucrum. PPI could be prevented in 92% of cases when modified Ti-Van was used. In one animal despite the use of antibiotic-tethered implant, PPI occurred partially due to the pin insertion penetrating the bone cortex.

Discussion: Biologically modified implants with bactericidal surface can have a promising role in management of periprosthetic infection. The modified implant described herein contains a nanoscale surface of covalently linked antibiotics that can potentially confer bactericidal properties throughout the life of the implant

Introduction and aim: Several authors have suggested that hyaline repair tissue following autologous – chondrocyte implantation (ACI) gives better clinical results than either mixed hyaline and fibrocartilage or fibrocartilage alone. This data is based on the use of periosteum as a covering membrane in these previous studies. We have for some years been using a porcine collagen type 1/III membrane (ACI-C) instead of periosteum and have now the opportunity to analyze the clinical results when compared with the histology of the repaired defect. We have also analysed the influence on the result of age and sex of the patient, the etiology of the lesion, the duration of the knee symptoms, number of previous knee procedures, the site and size of defect and the preoperative functional scores.

Method: Until 2004, 234 patients underwent autologous chondrocyte implantation at our centre. The patients were assessed clinically by their modified Cincinnati scores prospectively from 1 to 4 years from surgery. Also at arthroscopy (1 to 3 years following ACI-C) they underwent biopsy of the implant where possible and the neo-cartilage was graded as hyaline (H), mixed fibrohyaline (F.H), fibrocartilagenous (F.C) and fibrous (F).

Results: The clinical results showed that older patients had poorer results (p< 0.001) and a high preoperative modified Cincinnati score predicted a good result (p< 0.001). Concerning the cause of the defect, the percentage of patients with excellent and good results were significantly low among those with previously failed ACIs and mosaicplaties (12.5%) compared with those following trauma, osteochondritis dessicans and chondromalacia patellae (67% to 77%). At 4 year follow-up, 75% of patients with hyaline neo-cartilage had excellent and good modified Cincinnati scores whereas those with mixed fibro-hyaline and fibro-cartilage had fewer excellent and good results (44.4% and 54.5% respectively). The other parameters such as gender, the site of defect, duration of knee symptoms and the number of previous procedures and the size of the defect did not significantly influence the outcome. In conclusion, patients most likely to benefit from autologous chondrocyte implantation using a collagen membrane (ACI – C) are younger patients with higher preoperative functional scores and those who develop hyaline neo-cartilage.

Introduction The aim of this study was to assess the efficacy of current arthroscopic knotting techniques with commonly used suture materials.

Methods A Hounsfield tensiometer with a 1000N load cell, strain rate of 25 mm/min, bar separation of 7.5 mm was used under standard temperature and pressure. Suture materials were those in common use; 2 Ethibond, 1 PDS and 1 Panacryl. The knotting techniques compared were the Tennessee slider, Tautline hitch, Duncan Loop, SMC knot and the Surgeon’s knot. Two surgeons tied each knot 10 times using a suture passer and standardised knot technique. Each knot was tested to failure on 10 sequential experiments. Suture material strength was tested alone, tested to failure using the different knots and after suture immersion in normal saline. The ultimate strength of the suture material and of the various knotting techniques were assessed. The mode of failure, slip or suture material fractured was also investigated.

Results The 2 Ethibond had superior strength compared to 1 PDS or 1 Panacryl. The Tautline hitch and Surgeon’s knot had a significantly lower slip rate, with superior internal security than the other knotting techniques (p < 0.002). The Tennessee slider, Duncan Loop and SMC knots slipped in more than 50% of experiments. No difference was observed after soaking in normal saline. The number of additional half hitches required for maximum knot holding was consistently three, confirming previous findings.

Conclusions The Tautline hitch is recommended with its superior internal security, tying characteristics and overall knot strength. Whichever arthroscopic knot is selected, the addition of three alternating half hitches for consistent security and reliability is strongly supported.

Introduction: Conventional total hip replacement has a high rate of failure in young or high demand patients due to polyethylene wear, therefore, we perform a metal on metal hip resurfacing in these patients. Materials and Methods: The cup is all chrome cobalt alloy, with HA coating and the beads of the porous ingrowth surface are integrated with the substrate metal. The metal head is þxed with low viscosity cement, after careful precise preparation of femoral head.33 hybrid hip resurfacing in 29 patients. Average age was 42.8 years. Results: Harris Hip Score: 34.2 points average preoperatively and 97.1 points at the last examination. The average follow-up was 14.7 month. Discussion: The advantages: Minimal bone resection which makes for easier future revision, normal proximal femoral loading that hence avoidance of the stress shielding present in standard hip replacements, less risk of dislocation with greater range of motion, the physiological biomechanics of the joint is maintained, proprioception is maintained and we have noted that the postoperative recovery is extremely smooth and quick.

The disadvantages: Leg length and neck version cannot be altered. Hip resurfacing is, technically, a demanding procedure.

Contraindications: osteoporosis, varus neck.

Conclusions: Our early results are encouraging. We believe that metal on metal hybrid resurfacing is a legitimate alternative for active patients who require hip arthroplasty.

Soft tissue sarcomas (STS) have not demonstrated favourable clinical responses to emerging immunotherapies such as checkpoint inhibitors. Studies in carcinomas and melanoma have demonstrated that tumours lacking T-cell infiltrates are associated with poor responses to immunotherapies. It is postulated that STS lack tumour asscoiated lymphocytes which renders these tumours insensitive to checkpoint inhibitors. Our objective was to develop a novel syngeneic mouse model of STS and characterize the immune phenotype of these tumours. Additionally, we sought to evaluate the therapeutic responses of these sarcomas to checkpoint inhibitors and a Type I interferon agonist.

K-ras mutagenesis and p53 deletion was induced using a Lenti-Cre-recombinase injection into the hindlimb of 3 week old C57BL/6 mice. Tumours were harvested and characterized using standard histopathology techniques and whole trascriptome sequencing (RNAseq). Full body necrospy and histopathology was performed to identify metastases. Flow cytometry and immunohistochemistry was used to evaluate tumour immune phenotypes. Tumours were implanted into syngeneic C57BL/6 mice and the therapeutic responses to anti-CTLA4, anti-PD1 and DMXAA (Type I interferon agonist) were performed. Tumour responses were evaluated using bioluminescent imaging and caliper measurements.

Soft tissue sarcomas developed in mice within 2–3 months of Lenti-Cre injection with 90% penetrance. Histologic analyses of tumours was consistent with a high-grade myogenic sarcoma characterized by smooth muscle actin, Desmin and Myogenin D positive immunostaining. Using crossplatform normalization protocols, geneexpression signatures of the mouse tumours most closely correlated with human undifferentiated pleomorphic sarcoma (UPS). Collectively, gene expression signatures of this murine sarcoma correlated with all muscle-derived human sarcomas (ERMS, ARMS, Synovial sarcoma, UPS). No lung or other visceral metastases were observed in all mice who developed spontaneous tumours. Immune phenotyping demonstrated a paucity of tumour-infiltrating lymphocytes (TILs, (TAMs). 50% of identified TILs in these murine sarcomas expressed PD-1, yet tumours were not responsive to anti-PD1 therapy or anti-CTLA4 therapy. A single intra tumoural (i.t.) injection of the Type I interferon agonist, DMXAA resulted in 80–90% tumour necrosis 72 hrs post-injection, decreased tumour viability up to 2 weeks post-injection and a marked infiltration of CD8+ T-cells and anitgen presenting dendritic cells and macrophages. Additional longitudinal experiments demonstrate a sustained and progressive anti-tumour effect in 83% (5/6) mice up to 6weeks following a single i.t. injection of DMXAA. All control treated mice (6/6) reached humane endpoint within 14 days. At 3 months post-DMXAA treatment, 4/6 mice were free of disease. We re-injected UPS tumours into these mice and tumours did not grow, suggesting abscopal effects after DMXAA treatment of primary tumours.

We have characterized a new orthotopic and syngeneic mouse model of a myogenic soft tissue sarcoma. Like most human STS sub-types, these tumours have an immune inert tumour microenvironment and are not sensitive to checkpoint inhibitors. This model, syngeneic to C56BL/6 mice will enable future opportunities to investigate how various branches of the immune system can be targetted or manipulated to unearth new immunotherapeutic strategies for sarcoma. Using this model we have demonstrated that a single, intra-tumoural injection of a Type I interferon agonist can result in anti-tumour effects, recruit cytotoxic lymphocytes and antigen presenting cells with into the the tumour microenvironment. Abscopal tumour rejection after DMXAA treatement suggest adaptive T-cell responses against UPS are active in this model. Future work is needed to determine if upregulation of Type I inferferon pathways can be used as a therapeutic strategy for sarcoma or as a sensitization strategy for checkpoint inhibitors.