Figure 1

Time flow diagram of the study algorithm. All patients are assessed for 7 days in a recruitment period before commencement of the main study. They receive IVIG or Placebo on alternating days (day 1, 3, 5). Subsequently, a three-day period without monitoring is implemented because transitional pain increase has been noted in some patients, with no correlation with the ultimate efficacy of IVIG. Diary entries will be reviewed from day 9 onward. The main study ends at day 28. Crossover (upper half of diagram): all patients who leave the main study before 28 days will be offered crossover to the alternative treatment arm. Time points (day 1 C, 3 C, 5 C, etc.) are similar to those in the main study. Patients are being offered surgery if they have insufficient pain relief: either upon leaving the main study (as an alternative to crossover), or following crossover treatment. The treatment allocations will be unblinded when all patients have completed the study. Plac: Placebo