Abstract-We present an approach to support massively multi-player 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.

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.

BackgroundLumbar 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.Questions/purposesWe (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.MethodsWe 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.ResultsMean (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.ConclusionsRepeat 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 of EvidenceLevel II, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.