Laminar flow theatres were first introduced in the United Kingdom in the 1960s and 1970s and have become standard in orthopaedic surgery involving implants. A study from 1982 showed a 50% reduction in infections with joint arthroplasties when compared to conventional theatres and laminar flow became standard in the following decades. Recent evidence including a meta-analysis from 2017 questions the effectiveness of these theatre systems. Most of the evidence for Laminar flow use is based on arthroplasty surgery. We aimed to determine the effect of using non-laminar flow theatres on our trauma patients. A total of 1809 patients who had trauma surgery were identified from 2019 to 2021. 917 patients were operated on in a laminar theatre and 892 in a non-laminar theatre across two operating sites. We identified the surgical site infections as reported through our surveillance program within the first 90 days of infection. Patient co-morbidities were noted through patient records and procedure length was also noted. Of the 1809 trauma patients identified between the years of 2019 and 2021, 917 patients had operations in a laminar flow theatre and 892 in a non-laminar theatre. Of the 892 operated in non-laminar flow theatres, 543 were operated in the University Hospital of Wales (UHW) and 349 at the University Hospital of Llandough (UHL). An analysis of soft tissue infections and hospital acquired infections post-operatively demonstrated 15/543 and 71/543 respectively for non-laminar UHW infections and 4/349 and 21/349 for non-laminar UHL infections. A look at laminar flow patients showed 25/917 with soft tissue infections and 86/917 hospital acquired infections. There was no difference between laminar and non-laminar flow theatre infection rates showing rates of 12.1% and 12.2% respectively. In our trauma patients we noticed no significant advantage of using laminar flow theatres when compared to non-laminar flow theatres. This is in keeping with some recently published literature. Laminar flow theatres have been shown to decrease airborne pathogen counts under controlled conditions, but we conclude in the day to day environment of trauma theatres these conditions are either not met or that the theoretical advantage of laminar flow does not translate to a direct advantage of reduction of infections which may be achieved by standard prophylactic antibiotics

This study addresses four questions:. Does laminar flow exist in our operating theatres?. Do perioperative warming blankets affect laminar flow?. Do perioperative warming blankets cause displacement of particles into a wound perioperatively?. Do conventional theatres have adequate airflow?. It has been widely recognised that laminar flow theatres decrease colony forming units in operating theatres and thus decrease the risk of infection in arthroplasty surgery. It is also accepted that perioperative warming blankets improve patient haemodynamic stability and may reduce the risk of wound infection. However, there has been great debate as to whether these perioperative warming blankets cause disruption of laminar flow and excess displacement of dust into a wound, and thus increase the risk of infection of total joint arthroplasty surgery. Using digital video imaging and airflow measurement techniques as used in formula 1 racing design, this independent study reveals that the Bair Hugger system has no effect on laminar flow or paticle displacement. It also shows that factors out of the surgeon’s control disrupt laminar flow and that general theatre design may be inherently flawed. This would seriously affect the risk of infection

Abstract. Aim. To identify the difference in infection rates in ankle fracture surgery in Laminar and Non Laminar flow theatres. Background. The infection rates in ankle fracture surgery range between 1–8%. The risk factors include diabetes, alcoholism, smoking, open fractures, osteoporotic fractures in the elderly, and high BMI. Laminar flow has been shown to reduce infections in Arthroplasty surgeries. Therefore, it has become mandatory to use in those procedures. However, it's not the same with ankle fracture surgery. Materials and Methods. It was a retrospective study. The data was collected over a 5 year period between 2015 and 2020. It was collected from Blue spier, Panda, and theatre register. There were 536 cases in each group i.e. Laminar flow (LF) and Non-Laminar flow (NLF). The variables looked at were: 1. Superficial and deep infection rates in LF and NLF theatres, 2. The number of open fractures, 3. Type of ankle fractures (Bimalleolar, Trimalleolar), 4. The number of infected cases who had external fixation prior to ORIF, 5. The number of cases that had Plastics reconstructive procedures, and 6. The grade of the operating surgeon. Conclusions. Superficial infection rate between NLF and LF was not significantly different 11.5% vs 10.3%. The deep infection rate was statistically significant against NLF theatres at 6.34% vs 4.29%. The open fracture was a major contributing factor for deep SSI (14.7% vs 26%). The application of an external fixator in LF and NLF theatres did not alter the infection. rates. Bimalleolar fractures were associated with a higher infection rate

The purpose of this study was to determine whether a laminar flow operating system reduces deep infection rates in Total Hip Arthroplasty (THA) and Total Knee Arthroplasty (TKA) and to examine the costs involved in implementing laminar flow technology. A retrospective analysis of deep infection rates in 759 patients who underwent THA and TKA was performed in one hospital prior to and after the introduction of a vertical laminar flow operating system together with the use of isolation body exhaust suits. A cost analysis was also performed on the cost of implementing laminar flow technology and the average inpatient hospital cost of managing a deep infection. A control group consisted of 387 THA and TKA performed in 2 years in a conventional operating theatre and follow up carried out to a mean of 29 months. There were 12 recorded deep infections, 3.1%. Case group consisted of 372 THA and TKA performed in 2 years after the introduction of a vertical laminar flow operating theatre together with the use of isolation body exhaust suits, with a mean follow up to 22 months. There were 4 recorded deep infections, 1.1%. A comparison of deep infection rates yielded p value 0.06. There was a strong trend toward a reduction in deep infection rate in THA and TKA performed in the laminar flow theatre with the use of isolation body exhaust suits. The economic impact of deep infection in THA and TKA is vast and the cost of implementing laminar flow technology must be weighed against the deep infection rate as well as the number of operations performed at an institution

i. Purpose To determine whether operating in ultra-clean vertical laminar flow and personal isolation “space suits” reduces deep infection rates in total knee replacement compared to a conventional theatre and modern disposal gowns. ii. Method An analysis of deep infection rates in 373 patients who underwent total knee arthroplasty performed in one operating theatre prior to and after a theatre and clothing upgrade. Results The infection rate before the introduction of ultraclean air and space suits was 6/166 (3.6%). Afterwards the rate was 1/207 (0.5%). This shows a significant reduction (p< 0.05). iii. Conclusion Compared to conventional theatres and clothing the use of ultraclean vertical laminar flow and spacesuits significantly reduces the risk of infection in total knee arthroplasty

Aim: To determine the effects of the different types of headgear on bacterial shedding in laminar flow theatres. Material and Methods: Sham experiments were carried out using standard theatre clothing, sterile gowns and face masks with visors. Three experimental groups were utilised; no headgear (control), surgeons hoods or fabric balaclavas (known colloquially as “chicken hats”). The sham experiments consisted of two surgeons, scrubbed and gowned, both wearing the same headgear, talking and moving hands for 30 minutes over a sterile mock operating field. 5 bacterial plates were placed on the sterile sheets to capture shed bacteria. An additional 5 plates were placed above head height in the laminar flow enclosure. An air sampler was positioned within the laminar flow and set off for the middle 5 mins of the experiment. Plates were then incubated for 48hrs at 37oC and the number of colony forming units at head and waist height as well as in the air sampler were counted. Each experiment was repeated 5 times. Results: The bacterial shedding rate at waist height was 0.2 CFUs/plate (314 CFUs/m2/hr) for the control experiment, 0 CFUs/plate (0 CFUs/m2/hr) for the surgeons hoods and 0.08 CFUs/plate (126 CFUs/m2/hr) for the fabric balaclavas. Conclusion: These experiments show very low bacterial shedding rates with standard clothing and headgear in laminar flow theatres. Although these results demonstrate worse bacterial shedding with fabric balaclavas (which contradicts conventional thinking), the low rate of shedding rates means the results are not statistically significant. It therefore raises the question as to whether we should be using the more expensive fabric balaclavas without proven benefit, and the possibility of increased bacterial shedding

Introduction. Reducing infection in total joint replacement by using ultra clean air and protective enclosed suits (space suits) has become the standard in many operating theatres without good supporting evidence. This study examined the impact of laminar flow and space suits on the rate of revision for early infection following total hip (THR) and knee (TKR) replacement. Method. We used the 10-year results of the New Zealand Joint Registry to compare the rates of revision for early infection between laminar flow and conventional theatres both with and without the use of space suits. We separated hospitals and surgeons who had worked with and without space suits in both environments to exclude other confounding variables. Results. There were 51,485 THR and 36,826 TKR registered with laminar flow theatres used for 50% of the procedures and space suits used in 44% of cases. In THR there was a significant increase in revision for early infection in those procedures performed with the use of a space suit (p< 0.0001), for those performed in a laminar flow theatre (p< 0.003) and those procedures performed in a laminar flow theatre with a space suit (p< 0.001). The results were similar in TKR with the use of a space suit (p< 0.001), in laminar flow theatres (p< 0.019) and when laminar flow and space suits were used (p< 0.001). The results were unchanged when the surgeons and hospitals were analysed individually. Conclusion. The rate of revision for early infection has not been reduced by using laminar flow and space suits. The results of this study question the rationale for the increasing use and cost to the health system of these modalities in routine joint replacement

Aim. Whether laminar airflow (LAF) in the operating room (OR) is effective for decreasing periprosthetic joint infection (PJI) following total joint arthroplasty (TJA) remains a clinically significant yet controversial issue. This study investigated the association between operating room ventilation systems and the risk of PJI in TJA patients. Method. We performed a retrospective observational study on consecutive patients undergoing primary total knee arthroplasty (TKA) and total hip arthroplasty (THA) from January 2013-September 2017 in two surgical facilities within a single institution, with a minimum 1-year follow-up. All procedures were performed by five board-certified arthroplasty surgeons. The operating rooms at the facilities were equipped with LAF and turbulent ventilation systems, respectively. Patient characteristics were extracted from clinical records. PJI was defined according to Musculoskeletal Infection Society criteria within 1-year of the index arthroplasty. A multivariate logistic regression model was performed to explore the association between LAF and risk of 1-year PJI, and then a sensitivity analysis using propensity score matching (PSM) was performed to further validate the findings. Results. A total of 6,972 patients (2,797 TKA, 4,175 THA) were included. The incidence of PJI within 1 year for patients from the facility without laminar flow was similar at 0·4% to that of patients from the facility with laminar flow at 0·5%. In the multivariate logistic regression analysis, after all confounding factors were taken into account, the use of LAF was not significantly associated with reduction of the risk of PJI. After propensity score matching, there was no significant difference in the incidence of PJI within 1 year for patients between the two sites. Conclusions. The use of LAF in the operating room was not associated with a reduced incidence of PJI following primary TJA. With an appropriate perioperative protocol for infection prevention, LAF does not seem to play a protective role in PJI prevention

Purpose: Infection after TJA is a rare but devastating complication. Horizontal laminar airflow has been advocated to reduce infection rate. Methods: 896 consecutive primary and revision total joint arthroplasties of the hip and knee were retrospectively reviewed. The first 751 were performed before February 2004 in a horizontal laminar air flow room; the final 146 were performed without laminar flow from February 2004 through May 2005. All patients received the same perioperative antibiotics, wound management, and rehabilitation program. Body exhaust systems were worn in all cases. Results: There were a total of 10 infections (1.1%) requiring surgical treatment, including 6 deep knee infections (0.67%), and four (0.45%) wounds (3 knees and 1 hip) with delayed healing or superficial infections. 9 of the infections occurred in the laminar flow group (1.2%), including all 6 deep knee infections (6/456=1.3%), 2 knee and 1 hip wound infection. Only 1 infection (0.68%), in a knee wound, occurred in the non-laminar flow group. There were no deep hip infections. Statistically, more knees became infected than hips overall (9/550=1.64% vs 1/346=0.29%)(p< 0.01) and more knees developed deep infection with laminar flow than without (6/456=1.2% vs 0/94=0.00%)(p< 0.1). Conclusions: Laminar air flow did not alter the infection rate in THA, but may have increased infection rate in TKA. Infection is multifactorial, and longer follow up of the non-laminar flow group may reduce the differences seen. Nevertheless, this data agrees with other published data and is of significant concern for the TKA surgeon and patient alike

Aims. Body exhaust suits or surgical helmet systems (colloquially, ‘space suits’) are frequently used in many forms of arthroplasty, with the aim of providing personal protection to surgeons and, perhaps, reducing periprosthetic joint infections, although this has not consistently been borne out in systematic reviews and registry studies. To date, no large-scale study has investigated whether this is applicable to shoulder arthroplasty. We used the New Zealand Joint Registry to assess whether the use of surgical helmet systems was associated with lower all-cause revision or revision for deep infection in primary shoulder arthroplasties. Methods. We analyzed 16,000 shoulder arthroplasties (hemiarthroplasties, anatomical, and reverse geometry prostheses) recorded on the New Zealand Joint Registry from its inception in 2000 to the present day. We assessed patient factors including age, BMI, sex, and American Society of Anesthesiologists (ASA) grade, as well as whether or not the operation took place in a laminar flow operating theatre. Results. A total of 2,728 operations (17%) took place using surgical helmet systems. Patient cohorts were broadly similar in terms of indication for surgery (osteoarthritis, rheumatoid arthritis, fractures) and medical comorbidities (age and sex). There were 842 revisions (5% of cases) with just 98 for deep infection (0.6% of all cases or 11.6% of the revisions). There were no differences in all-cause revisions or revision for deep infection between the surgical helmet systems and conventional gowns (p = 0.893 and p = 0.911, respectively). Conclusion. We found no evidence that wearing a surgical helmet system reduces the incidence of periprosthetic joint infection in any kind of primary shoulder arthroplasty. We acknowledge the limitations of this registry study and accept that there may be other benefits in terms of personal protection, comfort, or visibility. However, given their financial and ecological footprint, they should be used judiciously in shoulder surgery. Cite this article: Bone Jt Open 2024;5(10):894–897

Aim: To determine the cost of medical treatment of infection following total joint replacement (TJR) of the hip or knee. With this information, and obtaining the current costs of antibiotics, antibiotic loaded cement and laminar flow theatres, we aimed to calculate the relative cost- benefit of these prophylactic strategies to prevent infection. Method: Fifty two patients who were admitted to The Canberra Hospital (TCH) for treatment of infection at following total joint arthroplasty between January 1996 and January 2001. A detailed cost analysis of treatment costs following infection was performed. All ward, theatre, prosthesis, investigation, pharmaceutical, allied health and medical costs were collated to produce a total cost of treatment. Current costs of prophylactic antibiotics, antibiotic cement and laminar flow theatres were obtained from suppliers. Costs were calculated for different combinations of prophylactic measures using the rates of deep periprosthetic infection reported through the Swedish Arthroplasty Registry. Results: There were 41 deep infections and 13 superficial. The average cost for the 54 patients for the in hospital treatment of infection was $41,215. The cost of treating a superficial infection with antibiotics alone averaged $17,663. The average cost of a two stage revision procedure for deep periprosthetic infection was $79,623. Assuming a hospital volume of 150 cases per year, the use of prophylactic intravenous antibiotics, the use of laminar flow and the combined use of antibiotics and laminar flow were significantly cost effective. The addition of antibiotic loaded cement was marginally cost ineffective in combination with either or both of intravenous antibiotics or laminar flow. Conclusion: The in hospital costs for the treatment of infection after TJR in the Australian setting have been addressed for the first time. Past studies have underestimated the cost of treatment. With this information, we have shown that the combinations of laminar flow and intravenous antibiotic for prophylaxis against infection in TJR are justified on a purely financial cost benefit basis

Laminar airflow systems are universal in current orthopaedic operating theatres and are assumed to be associated with a lower risk of contamination of the surgical wound and subsequent early infection. Evidence to support their use is limited and sometimes conflicting. We investigated whether there were any differences in infection rates (deep and superficial) between knee and hip arthroplasty cases performed in non-laminar and laminar flow theatres at 10 year follow-up. Between 2002 and 2006, 318 patients underwent knee and hip arthroplasty in a non-laminar flow theatre. Prospectively collected local arthroplasty audit data was collected including superficial and deep infection, revision for infection and functional outcomes. A cohort of patients from the same time period, who underwent knee and hip arthroplasty in a laminar flow theatre, were matched for age, sex, body mass index (BMI), operative approach, implant and experience of surgeon. Superficial infection rates were lower overall in the non-laminar flow theatre (2.2percnt; versus 4.7percnt;), with a significantly lower superficial infection rate for knee arthroplasty performed in the non-laminar flow theatre (2percnt; versus 6.9percnt;). The deep infection rates were similar (1.3percnt; vs 1.9percnt;) for both laminar and non-laminar flow theatre respectively. Revision rates for infection were similar between both groups (0.9percnt; in non-laminar flow theatre vs 0.3percnt; in laminar flow). Whilst the causes of post-operative surgical site infection are multifactorial, our results demonstrate that at long –term follow-up, there was no increased risk of infection without laminar flow use in our theatre

Deep infection occurs in 2–4% of lower limb arthroplasty resulting in increasing cost, co-morbidity and challenging revision arthroplasty surgery. Identifying the potential sources of infection helps reduce infection rates. The aim of our study is to identify the impact and potential for contamination of our hands and gowns whilst scrubbing using SSHS. A colony-forming unit (CFU) is a pathogenic particle of 0.5 micrometers to 5 micrometers. Concurrent particle counts and blood agar exposure settle plates for 3 subjects and 1 alcohol cleaned mannequin; testing a standard arthroplasty hood, a SSHS with and without the fan on for a 2 minute exposure to represent scrubbing time. Microbiological plates were incubated using a standard protocol by our local microbiology department. All SSHS were positive for gram-positive cocci with a mean colony count of 410cfu/m. 2. Comparing background counts for laminar flow (mean 0.7 particle/m. 3. ; 95% CI 0–1.4) versus scrub areas (mean 131.5 particle/m3; 95% CI 123.5–137.9; p=0.0003), however neither grew any CFU's with a 2-minute exposure. For the mannequin, the only significant result was with the fan on with a 1.5× increase in the particle count (p=0.042) and a correlating positive organism (13CFU/m. 2. ). With human subjects, however, the particle count increased by 3.75× the background count with the fan on (total p=0.004, CFU p=0.047) and all had positive cultures, mean 36 CFU/m. 2. There were no positive cultures with the standard arthroplasty hood or the SSHS with no fan on. If repeated in laminar flow, there was only a statistically significant increase with the fan on (p=0.049), but with negative cultures following a 2-minute exposure. Sterile gloves and gowns can be contaminated when scrubbing with the SSHS fan on. We recommend having the fan switched off when scrubbing until the hood and gown is in place, ideally in a laminar flow environment

The light handle can be a major source of contamination in operation theatres where surgeries are prolonged and light handles need to be manipulated multiple times. The light handle by sheer size can obstruct laminar flow and cause eddy currents and can cause bacterial deposition on light handle which in turn can contaminate light handles. A study of light handle contamination was done from November 2010 to December 2010 at Blackpool Victoria hospital from swabs taken from light handles during preoperative, intra operative and post operative period from a single laminar flow operating theatre. A total of 40 cases were selected for study. Most of our cases were primary hip and knee replacement. The swabs were cultured into blood agar /mcconkey medium and incubated for 48 hours at 37 degree Celsius. None of the swabs showed any bacterial contamination which shows light handle is not a source of intraoperative contamination. Our trial gives a point estimate of 0% contamination rate, upper limit of the 95% confidence interval of the probability of contamination as 7.5%. we conclude that light handle is not a source of contamination in operation theatres and hence no need to change gloves every time we manipulate light handle

Introduction: Surgical Site Infection (SSI) in spinal surgery at the James Cook University Hospital was investigated and compared with the published rates of 1–12%. Variables of instrumentation, laminar air flow, duration of operation, and blood units transfused in the first 48 hours were examined. Methods: 556 spinal operations were carried out in 2005–6. 147 of these involved the use of instrumentation. Infections were defined as positive wound or blood cultures. The duration of surgery, presence of laminar air flow and units of blood transfused were recorded. Statistical analysis was performed using the Fisher’s Exact Test. Results: Nine cases of SSI were identified in the 147 instrumented spinal operations in comparison to Zero in the 409 non-instrumented patients (p < 0.0001). The mean duration of instrumented surgery was 4 hours 19mins. The infection rates for operation duration < 5 h versus operation duration > 5 h (3/96 Vs 6/51) were not statistically significant (p = 0.065). Of the 147 instrumented spinal operations, 8 of 117 operations performed in a laminar air flow system and 1 of 30 performed without laminar air flow were infected (p = 0.69). Infection rates for those patients transfused < 2 units (4/85) were not significantly different to those in patients transfused > 2 units (5/62), p = 0.49. Conclusion: The rate of SSI at the James Cook University Hospital in instrumented spinal surgery was 6%. SSI in spinal surgery was heavily influenced by instrumentation, but was not reduced by laminar airflow. Duration of operation and number of units of blood transfused were not significant factors

Patient warming systems are used routinely to prevent hypothermia under anaesthetic, the benefits of which have been clearly shown in the anaesthetic literature. We were concerned that since these systems take ‘dirty’ air from floor level and distribute it over the patient, bacterial counts could be increased. Also, airflow under the blanket itself could disturb the patients’ own skin cells and thereby influence bacterial counts. With slit air sampling we analysed air quality at the simulated operative site by passing a known volume of air over an agar plate (tryptone glucose yeast). Using probability curves we were able to calculate the volume of air required to detect 1 colony forming unit (CFU) per m³ with 97% confidence. All tests were performed in an ultra clean air laminar flow theatre. We assessed the effect of varying degrees of skin shedding under the warming blanket using volunteer patients with Psoriasis. We also simulated activity outside the lamina flow to determine whether counts on the table were influenced. No colonies were grown in any of the study groups. Plates exposed outside the laminar flow area at floor level showed a relatively high level of contamination. We therefore conclude that the WarmTouch warming system does not influence bacterial counts at the operative site in ultraclean air ventilated theatres

Aim: To evaluate the short to medium term outcome of the Souter-Strathclyde prosthesis when used as a primary elbow arthroplasty in rheumatoid arthritis. Introduction: The Souter-Strathclyde prosthesis has been evaluated in several studies. In our hospital the operation is carried out using the same strict precautions as for lower limb arthroplasty. At the onset of surgery the ulnar nerve is handled minimally. This study looked at infection and complication rates, and also at outcome. Methods: The operations were carried out in laminar flow theatres with exhaust suits. At the start of the procedure the ulnar nerve was decompressed, but not mobilised from its bed, and held loosely with tape while being kept moist. Cases were identified from theatre and implant records. 61 implants in 53 patients were identified. Complication and revision rates were established from case sheets. Of this group 19 patients had died leaving 40 implants in 34 patients suitable for review. Case notes were analysed. Patients were contacted by post and were asked to fill out a DASH form. 30 patients (34 implants) responded. 26 patients (30 implants) attended a review clinic. Results: From the 61 implants there were 4 complications (one ulnar nerve dysthesia – transient, one dislocated prosthesis – open reduction, two wound infections) within the first year. Overall, 4 implants from 62 required revision, a rate of 6.5% (range 11–92 months, mean 37 months). Reasons – One loose, two periprosthetic fractures and one infection. Mean follow up was 74 months (range 36–120). Mean DASH score at follow up was 48.7 (range 4.5–81.8). Conclusion: The low incidence of ulnar nerve palsy, compared to published studies, may be attributable to the surgical technique. The use of laminar flow theatres and exhaust suits may account for the low infection rate. The complication rate and revision rate is comparable to previous published studies

Aims: To evaluate the short to medium term outcome of the Souter-Strathclyde prosthesis when used as a primary elbow arthroplasty in rheumatoid arthritis. Introduction: The Souter-Strathclyde prosthesis has been evaluated in several studies. In our hospital the operation is carried out using the same strict precautions as for lower limb arthroplasty. At the onset of surgery the ulnar nerve is handled minimally. This study looked at infection and complication rates, and also at outcome. Methods: The operations were carried out in laminar flow theatres and scrubbed staff wore exhaust suits. At the start of the procedure the ulnar nerve was decompressed, but not mobilised from its bed, and held loosely with tape while being kept moist. Cases were identified from theatre and implant records. 61 implants in 53 patients were identified. Complication and revision rates were established from case sheets. Of this group 19 patients had died, leaving 40 implants in 34 patients suitable for review. Case notes were analysed. Patients were contacted by post and were requested to fill out a DASH form. 30 patients (34 implants) responded; 2 declined to be involved leaving 31 implants in 28 patients to analyse, 78% of those available. Results: From the 61 implants there were 4 complications within the first year; one ulnar nerve palsy – transient, one dislocated prosthesis – open reduction, two wound infections. The infection rate is thus 3.3%. Overall to date 4 implants from 61 required revision, a rate of 6.6% (range 13–92 months, mean 37 months). Reasons – one loose, two periprosthetic fractures and one infection. Mean follow up at clinic was 74 months (range 36–120). Mean DASH score at follow up was 48.7 (range 4.5–81.8). Conclusion: The lower incidence of ulnar nerve palsy, compared to published studies, may be attributable to the surgical technique. The use of laminar flow theatres and exhaust suits may account for the lower infection rates. The complication rate and revision rate is favourable compared to previous studies

Adherent cells are known to respond to physical characteristics of their surrounding microenvironment, adapting their cytoskeleton and initiating signaling cascades specific to the type of cue encountered. Scaffolds mimicking native biophysical cues have proven to differentiate stem cells towards tissue-specific lineages and to maintain the phenotype of somatic cells for longer periods of culture time. Although the characteristic anisotropy of tendon tissue is commonly replicated in scaffolds, relevant physical cues such as tendon rigidity or mechanical loading are often neglected. The objective of this study is to use tendons' main extracellular matrix component, collagen type I, to create scaffolds with an anisotropic surface topography and controlled rigidity, in an effort to engineer functional tendon tissue equivalents, with native organization and strength. Porcine collagen type I in solution was treated with one of the following cross-linkers: glutaraldehyde, genipin or 4-arm polyethylene glycol (4SP). The resulting mixture was poured on micro-grooved (2×2×2 μm) or planar polydimethylsiloxane (PDMS) molds and dried in a laminar flow hood to obtain 5 mg/ml collagen films. Surface topography and elastic modulus of the final scaffolds were analyzed using SEM/AFM and rheometry, respectively. Human tendon cells were isolated from adult tendon tissue and cultured on micro-grooved/planar scaffolds for 4, 7 and 10 days. Cell morphology, collagen III and tenascin C expression were analyzed by immunocytochemistry. Among the different cross-linkers used, only the treatment with 4SP resulted in scaffolds with a recognizable micro-grooved surface topography. Precise control over the micro-grooved topography and the rigidity of the scaffolds was achieved by cross-linking the collagen with varying concentrations of 4SP at low pH and temperature. The elastic modulus of the scaffolds cross-linked with the highest concentration of 4SP matched the physiological values reported in developing tendons (∼15 kPa). Around eighty percent of the human tendon cells cultured on the cross-linked collagen films aligned in the direction of the anisotropy for 10 days in culture. At 4 days, tenoyctes cultured on micro-grooved substrates presented a significant higher nuclei aspect ratio than tenocytes cultured on planar substrates for all the 4SP concentrations. Synthesis, deposition and alignment of collagen III and tenascin C, two important tenogenic markers, were up regulated selectively in the rigid micro-grooved scaffolds after 7 days in culture. These results highlight the synergistic effect of matrix rigidity and cell alignment on tenogenic cell lineage commitment. Collectively, this study provides new insights into how collagen can be modulated to create scaffolds with precise imprinted topographies and controlled rigidities. Gene expression analysis and a replicate study with hBMSCs will be carried out to support the first results and to further identify the optimal biophysical conditions for tenogenic cell lineage commitment. This potentially leads to the design of smart implants that not only restore immediate tendon functionality but also provide microscopic cues that drive cellular synthesis of organized tissue-specific matrix

Introduction: Surgical Site Infection (SSI) in spinal surgery at the James Cook University Hospital was investigated and compared with the published rates of 1 – 12%. Variables of instrumentation, laminar air flow, duration of operation, and blood units transfused in the first 48 hours were examined. Methods: 556 spinal operations were carried out in 2005–6. 147 of these involved the use of instrumentation. Infections were defined as positive wound or blood cultures. The duration of surgery, presence of laminar air flow and units of blood transfused were recorded. Statistical analysis was performed using Fishers exact test. Results: 9 cases of SSI were identified in the 147 instrumented spinal operations in comparison to zero in the 409 non-instrumented patients (p < 0.0001). The mean duration of surgery was 4 hours 19mins. The results for operation duration < 5hours vs. operation duration > 5hours (3/96 vs 6/51) were not statistically significant. (p=0.065). Of the 147 instrumented spinal operations, 8 of the infected were performed in a laminar air flow system and 1 without (not statistically significant, p=0.69). The results for blood transfusion < 2units vs. blood transfusion ≥2 units (4/85 vs 5/62) were not significant (P=0.49). Conclusion: The rate of SSI at the James Cook University Hospital in instrumented spinal surgery was 6%. SSI in spinal surgery was heavily influenced by instrumentation, but was not reduced by laminar airflow. Duration of operation and number of units of blood transfused were not significant factors