The shunt design trial: Variation in surgical experience did not influence shunt survival

Introduction: An international multicenter randomized trial comparing standard pressure differential valves, Orbis Sigma valves and PS Medical Delta valves for children with newly diagnosed hydrocephalus failed to show a difference in the time to first shunt failure. Surgeons' prior experience with the three valves varied. This analysis was performed to assess whether lack of surgical experience with any of the valves could explain the overall negative result. Methods: (1) Shunt survival was compared at high- and low-volume centers. (2) The 1-year shunt survival rates (+/- 95% confidence interval) for patients entered in the first quarter and the last quarter of the 25-month accrual period were compared (for all patients, and for each shunt). Results: Survival curves for high- and low-volume centers were similar. Ninety of the 344 randomized patients were accrued in the first quarter and 93 in the last quarter. The 1-year shunt survival for all patients entered in the first quarter was 72% (+/- 11%) compared to 64% (+/- 10%)for patients entered in the last quarter. The shunt-specific results were 66% (+/- 20%) compared to 54% (+/- 20%) for Delta valve patients, 75% (+/-20%) compared to 70% (+/- 17%) for standard valve patients and 76% (+/- 18%) compared to 66% (+/- 16%)for Orbis Sigma patients. Discussion: Shunt survival did not improve as surgeons accumulated experience over the course of the study. Although participating surgeons had varying levels of experience with the different shunts at the start of the trial, this does not appear to explain the overall negative trial result.