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Background: Lumbar spinal stenosis (LSS) is a common disorder in older people. Inactivity secondary to the disease state can further increase LSS symptoms. Initial care includes physiotherapy to relieve symptoms and optimize patient function and quality of life. It is currently unclear whether inactivity before surgery for LSS is associated with postoperative outcomes. Our aim was to investigate associations between self-reported exercise before LSS surgery and self-reported outcomes at 1 -year follow-up. Methods: Using a retrospective cohort study design, prospective data were collected from the National Swedish Register for Spine Surgery (Swespine) between September 2006 and December 2012: 11,956 patients diagnosed with LSS completed the 1 -year follow -up. The primary outcome measure was the Oswestry Disability Index (ODI). Secondary outcome measures were back and leg pain reported on a visual analog scale (VAS). The independent variable was dichotomized into no regular exercise (NRE) and regular exercise (RE). Adjusted analysis of covariance models were used to analyze differences in outcome improvement between the NRE and RE groups. Results: The mean improvement in the ODI was 15.9 (95% CI, 15.5-16.3) in the NRE group and 19.2 (95% CI, 18.5- 19.8) in the RE group (P < 0.001). Improvement in back pain (P < 0.001) and leg pain (P < 0.001) were also inferior in the NRE group compared to the RE group. The NRE group improved 21.8 (95% CI, 21.2-22.5) units in back pain and 28.8 (95% CI, 28.1-29.5) in leg pain on the VAS compared to 25.2 (95% CI, 24.2-26.3) units in back pain and 32.5 (95% CI, 31.3-33.6) in leg pain in the RE group. Conclusions: Inactivity defined as self-reported NRE before surgery for LSS is associated with worse outcomes 1 -year postsurgery compared to patients reporting RE. Clinical Relevance: This study is relevant to currently practicing spinal surgeons and spine physiotherapists. Level of Evidence: 3.

Background The purpose of this study was to compare the cumulative incidence of postoperative periprosthetic fracture (PPF) in a cohort of femoral neck fracture (FNF) patients treated with two commonly used cemented stems: either a collarless, polished, tapered Exeter stem or the anatomic Lubinus SP2 stem. Methods In this retrospective multicenter cohort study of a consecutive series of patients, we included 2528 patients of age 60 years and above with an FNF who were treated with either hemiarthroplasty or total hip arthroplasty using either a polished tapered Exeter stem or an anatomic Lubinus SP2 stem. The incidence of PPF was assessed at a minimum of 2 years postoperatively. Results The incidence of PPF was assessed at a median follow-up of 47 months postoperatively. Thirty nine patients (1.5%) sustained a PPF at a median of 27 months (range 0–96 months) postoperatively. Two of the operatively treated fractures were Vancouver A (5%), 7 were Vancouver B1 (18%), 10 were Vancouver B2 (26%), 7 were Vancouver B3 (18%), and 13 were Vancouver C (32%). The cumulative incidence of PPF was 2.3% in the Exeter group compared with 0.7% in the SP2 group (p p Conclusions The Exeter stem was associated with a higher risk for PPF than the Lubinus SP2 stem. We suggest that the tapered Exeter stem should be used with caution in the treatment of FNF. Trial registration The study was registered at clinicaltrials.gov (identifier: NCT03326271).

Objective The objective of this study was to describe aspects of suffering related to being a person with LSS and how suffering is managed before LSS surgery. Methods/design/setting A Swedish county hospital. Interviews with 18 consecutive patients on the waiting list for LSS surgery. The themes that emerged from content analysis were further interpreted using Antonovsky salutogenic model as a sensitizing concept. Results The suffering from LSS before surgery included the main theme of experiencing an impaired physical and social life and struggling to be believed and taken seriously. This had coping strategies to manage symptoms before surgery: a good physician-patient relationship alleviates the burden of long waiting times; ways to manage pain and disability; ambiguous expectations and hope for recovery, and; ways to handle concerns before surgery). Conclusion Being a person with LSS includes suffering and a possibility to discover coping abilities or having support structures for doing so. Our study emphasizes the importance of a supportive dialogue, where physicians and patients make the suffering from LSS and care before LSS surgery more comprehensible and manageable.

Introduction The mortality of femoral neck fracture (FNF) is high and every effort should be made to identify and manage any possible risk factors. The aim of this study was to evaluate whether on-admission hemoglobin (Hb) level, C-reactive protein (CRP), and serum creatinine were associated with 2-year mortality after FNF. Patients and Methods In this retrospective observational cohort study, we considered for inclusion all displaced FNF patients 65 years and above treated with hemi-arthroplasty between February 2011 and May 2015. We documented the age, sex, cognitive status, and American Society of Anesthesiologists (ASA) classification. The Hb level, CRP, and serum creatinine were measured. The medical records were followed up for 2 years. We fitted different crude and adjusted Cox proportional hazards models to examine whether Hb level 20 mg/L, and serum creatinine >100 μmol/L were associated with the 2-year mortality, adjusted for age, sex, and ASA class. Results A total of 290 patients [208 females (72%), mean age 84 years] were included in the study. More than 50% of patients had impaired cognition and ASA class 3–4. Of the 290 patients, 38.3% ( n = 111) had died within 2 years after surgery. Mortality among males was 46.3% ( n = 38) while mortality among females was 35,1% ( n = 73), p = 0.07. We found that on-admission Hb level 20 mg/L and serum creatinine >100 μmol/L were not associated with 2-year mortality ( p = 0.89 and p = 0.31, respectively). Conclusion On-admission Hb level 20 mg/L and serum creatinine >100 μmol/L, was associated with 2-year mortality. These results can help healthcare providers identify high-risk FNF patients who probably would benefit from optimized perioperative medical management.

Tobacco smoking is an injurious habit associated with a number of chronic disorders. Its influence on disc metabolism and degeneration including lumbar spinal stenosis (LSS) has been investigated in the literature.We aimed to investigate whether tobacco smoking is an independent risk factor for undergoing surgical intervention for LSS.This is a prospective cohort study.The patient sample of 331,941 workers was derived from a Swedish nationwide occupational surveillance program for construction workers.The outcome measure included the incidence of undergoing surgical intervention for LSS in tobacco smokers versus no smokers.At inclusion, age, sex, body mass index (BMI), workers' job title, and self-reported smoking habits were registered. The workers were divided into four categories: never smoked, former smoker, moderate current (1-14 cigarettes/day), and heavy current (≥15 cigarettes/day). Patients who underwent a surgically treated LSS were defined using the relevant International Classification of Diseases (ICD) disease code derived from the Swedish National Patient Register.A total of 331,941 participants were included in the analysis. Forty-four percent of the participants were non-smokers, 16% were former smokers, 26% were moderate smokers, and 14% were heavy smokers. The vast majority of construction workers were males (95%). During the average follow-up of 30.7 years, 1,623 participants were surgically treated for LSS. The incidence rate ratio (IRRs) of LSS varied across smoking categories, with the highest values found in heavy smokers. Compared with non-smokers, all smoking categories show an increased incidence of surgically treated LSS. The findings were consistent even when the comparison was performed for participants with BMIs between 18.5 and 25 and for participants aged between 40 and 74 years.Tobacco smoking is associated with an increased incidence of surgically treated LSS. The effect seems to be dose related, whereby heavy smokers have a higher risk than moderate or former smokers.

Background: Low back pain (LBP) with or without lumbar disc herniation (LDH) is one of the most commonly found symptoms worldwide. The etiology is often unclear, but a low-grade infection caused by the anaerobic skin bacterium Cutibacterium acnes (formerly Propionibacterium acnes), sometimes found on culture during LDH surgery, has been suggested as a cause. Given worldwide concern over multidrug resistant bacteria, further investigation is highly warranted. Our study aimed to compare findings regarding bacterial presence in painful lumbar degenerative disc disease (DDD) in adults having LDH with findings in young patients with scoliosis, but without DDD or relevant lumbar pain. Methods: Between 2015 and 2017, 40 adults with LDH (median age 43, IQR 33-49) and 20 patients with scoliosis (median age 17, IQR 15-20) underwent surgery at seven Swedish hospitals. Samples were collected and cultured from skin, surgical wound, discs and vertebrae. Genetic relatedness of C. acnes isolates was investigated using single nucleotide polymorphism (SNP) analysis. DNA samples collected from discs/vertebrae were analysed using 16S rRNA-based PCR sequencing. Preoperative MRI findings were assessed for inflammatory Modic changes. Findings: No bacterial growth was found in 6/40 (15%) LDH patients, compared with 3/20 (15%) scoliosis patients. A single species, C. acnes, was found exclusively in the disc/vertebra from one patient in each group; in the LDH group, 29/40 (72%) patients had at least one sample with growth of C. acnes, while the corresponding figure in the scoliosis group was 14/20 (70%). There was no association between bacterial findings and Modic changes. Interpretations: The results suggest that finding bacteria like C. acnes in discs and vertebrae during surgery is likely due to contamination. Antibiotic use to treat LBP/LDH without signs of clinical discitis/spondylitis should be seriously questioned. Funding Statement: The study was funded by FORSS, a Swedish regional research foundation Declaration of Interests: The authors state: " no conflicts of interest to declare." Ethics Approval Statement: The study was approved by the ethical committee in Linkoping (EPN, Ref. no. 2015/152-31). All patients gave their written informed consent.

Purpose To compare bacterial findings in pain-generating degenerated discs in adults operated on for lumbar disc herniation (LDH), and mostly also suffering from low back pain (LBP), with findings in adolescent patients with non-degenerated non-pain-generating discs operated on for scoliosis, and to evaluate associations with Modic signs on magnetic resonance imaging (MRI). Cutibacterium acnes (Propionibacterium acnes) has been found in painful degenerated discs, why it has been suggested treating patients with LDH/LBP with antibiotics. As multidrug-resistant bacteria are a worldwide concern, new indications for using antibiotics should be based on solid scientific evidence. Methods Between 2015 and 2017, 40 adults with LDH/LBP (median age 43, IQR 33–49) and 20 control patients with scoliosis (median age 17, IQR 15–20) underwent surgery at seven Swedish hospitals. Samples were cultured from skin, surgical wound, discs and vertebrae. Genetic relatedness of C. acnes isolates was investigated using single-nucleotide polymorphism analysis. DNA samples collected from discs/vertebrae were analysed using 16S rRNA-based PCR sequencing. MRI findings were assessed for Modic changes. Results No bacterial growth was found in 6/40 (15%) LDH patients, compared with 3/20 (15%) scoliosis patients. Most positive samples in both groups were isolated from the skin and then from subcutis or deep within the wound. Of the four disc and vertebral samples from each of the 60 patients, 235/240 (98%) were DNA negative by bacterial PCR. A single species, C. acnes, was found exclusively in the disc/vertebra from one patient in each group. In the LDH group, 29/40 (72%) patients had at least one sample with growth of C. acnes, compared to 14/20 (70%) in the scoliosis group. Bacterial findings and Modic changes were not associated. Conclusions Cutibacterium acnes found in discs and vertebrae during surgery for disc herniation in adults with degenerated discs may be caused by contamination, as findings in this group were similar to findings in a control group of young patients with scoliosis and non-degenerated discs. Furthermore, such findings were almost always combined with bacterial findings on the skin and/or in the wound. There was no association between preoperative Modic changes and bacterial findings. Antibiotic treatment of lumbar disc herniation with sciatica and/or low back pain, without signs of clinical discitis/spondylitis, should be seriously questioned. Graphic abstract These slides can be retrieved under Electronic Supplementary Material.

Unfortunately, the 5th author name was incorrectly published in the original paper. The complete correct name is given below.

A prospective cohort study that used a Swedish nationwide occupational surveillance program for construction workers (period of registration from 1971 to 1992). In all, 364,467 participants (mean age at baseline 34 yr) were included in the study.To determine whether overweight and obesity are associated with a higher risk of lumbar spinal stenosis (LSS).During recent decades, LSS has become the most common indication for spine surgery, a change that coincides with a higher prevalence of obesity.A diagnosis of LSS was collected through individual linkage to the Swedish National Patient Register through December 31, 2011. Poisson regression models were employed to estimate multivariable-adjusted incidence rate ratios (IRRs) for LSS.At baseline, 65% had normal weight (BMI [body mass index]: 18.5-24.99 kg/m), 29% were overweight (BMI: 25-29.99 kg/m), 5% were obese (BMI ≥30 kg/m), and 2% were underweight (BMI18.5 kg/m). During 11,190,944 person-years of follow-up, with a mean of 31 years, 2381 participants were diagnosed with LSS. Compared with normal weight individuals, obese workers had an IRR of 2.18 (95% confidence interval, 1.87-2.53) for LSS and overweight workers had an IRR of 1.68 (95% confidence interval, 1.54-1.83). Workers who were underweight halved their risk of LSS (IRR: 0.52, 95% confidence interval, 0.30-0.90).Obese and overweight persons are at a higher risk of developing LSS. Furthermore, our results indicate that obesity might be a novel explanation for the increased number of patients with clinical LSS.3.

Lumbar disc herniation (LDH) is a common indication for lumbar spine surgery. The proportion of patients having a second surgery within 2 years varies in the literature between 0.5% and 24%, with recurrent herniation being the most common cause. Several studies have not found any relevant outcome differences between patients undergoing surgery for primary LDH and patients undergoing reoperation for a recurrent LDH, but these studies have limitations, including small sample size and retrospective design. We (1) compared patient-reported outcomes between patients operated on for primary LDH and patients reoperated on for recurrent LDH within 1 year after index surgery and (2) determined risk factors for worse outcomes. We obtained data from the Swedish National Spine Register, Swespine, where patient-reported outcomes are collected using mailed protocols at 1, 2, 5, and 10 years after surgery. Of the 13,562 patients identified who underwent LDH between January 2000 and May 2011, 13,305 (98%) underwent primary surgery for LDH and 257 (2%) underwent reoperation for a recurrent LDH within the first year. Patient-reported outcomes at 1 to 2 years were available for 8497 patients (63%), 8350 of 13,305 (63%) in the primary LDH group and 147 of 257 (57%) in the recurrent LDH group (p = 0.068). We compared leg and back pain (VAS: 0-100), function (Oswestry Disability Index [ODI]: 0-100), quality of life (EQ-5D: -0.59 to 1.0), patient satisfaction, and global assessment of leg pain between groups. We also analyzed rsik factors for worse global assessment and satisfaction. Mean (95% CI) differences in improvement between groups favoring patients with primary LDH were VAS leg pain 9 (4-14), ODI 6 (3-9), and EQ-5D 0.09 (0.04-0.15). While statistically significant, these effect sizes may be lower than the minimal clinically important differences often referred to. Percentage of satisfied patients was 79% and 58% in the primary and recurrent LDH groups, respectively (p < 0.001), and percentage of patients with no or better leg pain (global assessment) was 74% and 65%, respectively (p = 0.008). Reoperation for recurrent LDH represented the largest independent risk for dissatisfaction; this factor and smoking represented similar risks for less improvement in leg pain. Repeat surgery for a recurrent LDH was performed with good probability for improvement, although not as good as for primary LDH surgery, and patients undergoing repeated surgery were less satisfied. Studies on risk factors for recurrence are warranted. Level II, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.

Study Design. SWESPINE, the Swedish Spine Register, was used for this cohort study. Objective. Our primary aim was to determine weight change in obese patients after surgery for lumbar spinal stenosis (LSS). Our secondary aim was to study any possible associations between weight loss after surgery and improvement in patient-related outcome measures (PROMs). Summary of Background Data. Only meager evidence is available as to how surgery for LSS affects weight and whether weight loss is associated with improvement in PROMs after surgery for LSS. Methods. All obese patients who underwent surgery for LSS from January 1, 2006 through June 30, 2008 with a completed 2-year follow-up in SWESPINE were included. Data for weight were collected before surgery and then 1 and 2 years after surgery. The cohort was divided into 3 subclasses (weight stable, weight loss, or weight gain). Results. Totally, 538 obese patients were enrolled. Mean weight loss was 1.9 kg (95% confidence interval, 1.5–2.3) 1 year after surgery and 2.0 kg (95% confidence interval, 1.5–2.4) after 2 years after surgery. Only 8% of the patients reported a clinically important weight loss (≥10%). No significant differences in PROMs were observed. The weight-stable group reported a mean improvement of 0.22 (standard deviation, 0.36) in EQ-5D, 14 (18) units in the Oswestry Disability Index, 18 (33) units in back pain (visual analogue scale), and 23 (36) units in leg pain (visual analogue scale). The corresponding changes in the weight-loss group were 0.23 (0.35) in EuroQol 5D, 15 (19) in Oswestry Disability Index, 27 (29) in back pain, and 31 (36) in leg pain. Conclusion. Modest weight loss was reported 1 and 2 years postsurgery; a small proportion (8%) of these patients reported a clinically important weight loss at the 2-year follow-up. The weight loss was unrelated to changes in PROMs. Conclusion. Level of Evidence: 3

Study design A cohort study based on the Swedish Spine Register. Objective To determine the association between body mass index (BMI) and outcome of lumbar spine surgery for spinal stenosis. Summary of background data Several small studies have sought to evaluate the importance of obesity in relation to results after surgery for lumbar spinal stenosis (LSS), but the findings are inconsistent and relatively weak. Methods All patients who underwent surgery for LSS from January 1, 2006, to June 30, 2008, with a completed 2-year follow-up in the Swedish Spine Register were included. Logistic regression was used to assess the association between BMI and different outcomes. Results Of the 2633 patients enrolled, 819 (31%) had normal weight, 1208 (46%) were overweight, and 606 (23%) were obese. On average, all 3 BMI groups achieved significant improvements after surgery. A higher BMI, however, was associated with greater odds of dissatisfaction after surgery and inferior results at the 2-year follow-up. After adjusting for differences in baseline characteristics, the obese group demonstrated inferior function and quality of life as measured by the Oswestry Disability Index (ODI) and the EuroQol Group Index (EQ-5D), respectively. At the 2-year follow-up, obese patients had a mean ODI of 33 (95% confidence interval [CI], 31-34) and mean EQ-5D of 0.56 (95% CI, 0.54-0.59) compared with a mean ODI of 25 (95% CI, 24-26) and mean EQ-5D of 0.64 (95% CI, 0.62-0.66) in the normal weight group. When compared with the normal weight patients, the adjusted odds ratio for dissatisfaction was 1.73 in the obese group (95% CI, 1.36-2.19). Differences between the normal weight and overweight groups were modest and therefore could not be considered clinically relevant. Conclusion Obese patients achieved significant pain reduction, better walking ability, and improved quality of life after surgical treatment of LSS. Nevertheless, obesity was associated with a higher degree of dissatisfaction and poorer outcomes after surgery for LSS.

INTRODUCTION: Femoral neck fracture (FNF) is a devastating injury with serious medical and social consequences. One-third of these patients have some degree of impaired cognitive status. Despite this, a high proportion of hip fracture trials exclude patients with cognitive impairment (CI). We aimed to evaluate whether moderate to severe CI could predict walking ability, quality of life, functional outcome, reoperations and mortality in elderly patients with displaced FNF treated with hemiarthroplasty (HA). METHODS: This cohort study included a consecutive series of 188 patients treated with HA for a displaced FNF. Patients were assessed for estimated preoperative and 1 year postoperatively with regard to walking ability, cognitive status, quality of life with EQ-5D and hip function with Harris hip score. RESULTS: There were 188 patients who met the inclusion criteria. A total of 130 patients were in the control group, and 58 were in the CI group. At 1-year follow-up, 31 patients (24%) had died in the control group and 22 patients (38%) had died in the cognitive impaired group. This difference in reoperation and mortality rate was statistically significant (log-rank test, p = 0.016). The CI had a significantly higher incidence of being non-walker (28 vs. 4%, OR 9.2, p = 0.001). The EQ-5D was higher in the control group, while the Harris hip score was comparable in the two groups. CONCLUSIONS: Moderate to severe CI was associated with a high incidence of non-walking ability, worse quality of life, high mortality and re-operation rate after femoral neck fractures treated with HA.

Introduction Periprosthetic joint infection (PJI) is a severe complication of hip arthroplasty for femoral neck fractures (FNF). Debridement, antibiotics and implant retention (DAIR) is recommended in early PJI in association with stable implants. Few studies have evaluated the outcome of DAIR in this fragile population. The purpose of this study was to analyse risk factors for PJI and the short-term outcome of DAIR in FNF patients treated with a hip arthroplasty. Methods A consecutive series of 736 patients (median age 81 years, 490 women, 246 men) had been treated with either a total hip arthroplasty or a hemi hip arthroplasty for a displaced FNF at our institution. 33 (4.5%) of the hips developed an early (Results DAIR eradicated the PJI in 82% (23/28) of patients at a median follow-up of 31 (SD 29.8) months of the infected hips. The logistic regression analysis indicated that 2 or more changes of the primary dressing due to wound bleeding was associated with an increased risk for developing PJI (OR 4.9, 95% 1.5 to 16.1, p = 0.01). Conclusions The short-term success-rate of DAIR was unexpectedly favourable in this fragile patient population; the results being on par with that after PJI in osteoarthritis patients. The need for repeated bandage changes postoperatively indicates an increased risk for PJI and should prompt early surgical intervention.

There is a shortage of spine surgeons in Sweden. To guarantee the legal right to healthcare, many counties must hire doctors, with increasing costs. In our new out-patient department routine, the majority of the patients are examined by a physiotherapist at their first visit. History taking and clinical and radiographic examinations are discussed in a team conference, and possible candidates for spine surgery are selected for an appointment with a spine surgeon. Furthermore, the patients were more satisfied with the new routine and management plan.

In this paper, we present a model for transport level compression with dynamic compression level adaptation, and we present an implementation of this model in Linux TCP, together with measurements showing what performance to expect when using adaptable end-to-end compression over wireless radio links and over an Ethernet. Measurements from our implementation show that for link speeds up to 10 Mbps, employing compression yields a throughput gain for most types of data. For slower speeds (e.g. 1–2 Mbps wireless radio links) this gain is significant (for the Calgary Compression Corpus files, the throughput increase is typically in the range of 50–200%, depending on link speed and data characteristics).

During recent decades, lumbar spinal stenosis (LSS) has become the most common indication for spine surgery, a change that coincides with a higher worldwide prevalence of overweight and obesity. Thus, surgical treatment of LSS in the overweight and obese population is common and increasing in scope.The overall aim of this thesis was to investigate whether body mass index (BMI) is related to the development of LSS, and whether BMI is linked to outcome after surgery for LSS. We further evaluated whether there are specific experiences of LSS from a patient perspective.Data were obtained for all patients registered in the Swedish Spine Register who had undergone surgery for LSS between January 1, 2006 and June 30, 2008. After adjusting for differences in baseline characteristics, patients with obesity showed both poorer results after surgery and a higher rate of dissatisfaction than patients with normal weight (odds ratio 1.73; 95% confidence interval, CI, 1.36-2.19).Furthermore, patients with obesity in the cohort reported modest weight loss at follow-up (2.0 kg; 95% CI, 1.5-2.4), and only 8% reported a clinical important weight loss 2 years after surgery.Our analysis of 389,132 construction workers, showed that overweight (incidence rate ratio, IRR 1.68; 95% CI, 1.54-1.83) and obesity (IRR 2.18; 95% CI, 1.87-2.53) were associated with an increased future risk in developing LSS when compared with patients with normal weight.To gain insight into the patients' perspective of LSS, we performed interviews with 18 patients who were on a waiting list for LSS surgery. The transcripts, analyzed with content analysis, revealed that living with LSS is a physical, mental and social challenge in which resources to cope with the condition are of major importance.In summary, obesity is associated with poorer results after surgery, and patients with obesity report modest weight loss during follow-up. In addition, obesity is associated with an increased risk to develop LSS. Our findings revealed that being a patient with LSS, naturally involves considerable suffering and pain, but it also implies being a person with his or her own resources who is able to cope with these adverse conditions.

A common pitfall of many proposals on new information-centric architectures for the Internet is the imbalance of upfront costs and immediate benefits. If properly designed and deployed, information-centric architectures can accommodate the current Internet usage which is at odds with the historical design of the Internet infrastructure. To address this concern, we focus on prospects of incremental adoption of this paradigm by introducing a peer-to-peer based transport protocol for content dissemination named Swift that exhibits properties required in an Information-Centric Network (ICN), yet can be deployed in the existing Internet infrastructure. Our design integrates components while highly prioritizing modularity and sketches a path for piecemeal adoption which we consider a critical enabler of any progress in the field. QC 20120802

Previous studies of large-scale (multimillion node) Kademlia-based DHTs have shown poor performance, measured in seconds, in contrast to the far more optimistic results from theoretical analysis, simulations and testbeds. In this paper, we unexpectedly find that in the Mainline BitTorrent DHT (MDHT), probably the largest DHT overlay on the Internet, many lookups already yield results in less than a second, albeit not consistently. With the backwards-compatible modifications we present, we show that not only can we reduce median latencies to between 100 and 200 ms, but also consistently achieve sub-second lookups. These results suggest that it is possible to deploy latency-sensitive applications on top of large-scale DHT overlays on the Internet, contrary to what some might have concluded based on previous results reported in the literature. QC 20110825

We present an approach to support massively multiplayer games on peer-to-peer overlays. Our approach exploits the fact that players in MMGs display locality of interest, and therefore can form self-organizing groups based on their locations in the virtual world. To this end, we have designed scalable mechanisms to distribute the game state to the participating players and to maintain consistency in the face of node failures. The resulting system dynamically scales with the number of online players. It is more flexible and has a lower deployment cost than centralized games servers. We have implemented a simple game we call SimMud, and experimented with up to 4000 players to demonstrate the applicability of this approach.