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Table 5 Undisplaced fractures: estimated study power for 250 patients per treatment arm (N = 500)

From: Fixation using alternative implants for the treatment of hip fractures (FAITH): design and rationale for a multi-centre randomized trial comparing sliding hip screws and cancellous screws on revision surgery rates and quality of life in the treatment of femoral neck fractures

Baseline risk
(Year 1)^ Relative risk reduction
  10% 15% 20% 25% 30% 40%
20% 8.0% 13.2% 20.6% 30.3% 42.0% 68.0%
25% 9.3% 16.0% 25.5% 37.8% 51.3% 79.0%
30% 10.7% 19.1% 31.0% 45.6% 61.4% 87.1%
35% 12.3% 22.6% 36.3% 53.7% 70.3% 92.7%
40% 14.1% 26.5% 43.3% 61.8% 78.2% 96.3%
  1. *Number of patients per treatment arm, alpha = 0.05.
  2. ^Year 2 risk is 1/3 that of year 1.
  3. Bold numbers indicate statistical power range for this study.