Novel cast-saw alarm system reduces blade-to-skin contact in a pediatric upper extremity model

Purpose: To determine the effectiveness of a novel cast-saw alarm system in minimizing the number and duration of cast-saw blade-to-skin contacts. Methods: Twenty orthopaedic residents removed a pair of long-arm casts applied to instrumented pediatric upper extremity models. The model and cast-saw were instrumented to detect blade to “skin” contact at a rate of 600 Hz. Each resident performed cast removal with and without the use of a cast-saw alarm, the order of which was randomized. Eleven additional “new” cast-saw users then removed pairs of casts, without and then with the cast alarm, to evaluate what effect the alarm would have on preventing blade-to-skin contact in users with no previous cast-saw experience. The number and duration of cast-saw touches were then evaluated. Statistical significance was determined paired 1-sided students t tests (number of touches). Results: For the residents (n = 20), the total number of blade-to-skin contacts was 233. One hundred eighty-one blade-to-skin contacts without the alarm and 52 with the alarm (71% reduction) (t₍₁₉₎ = -3.42, P = 0.001), averaging 6.45 more blade-to-skin contacts per cast without the alarm. The median blade-to-skin contact duration was 0.166 seconds without the alarm and 0.087 seconds with the alarm. This was a 48% reduction in contact time (P = 0.073). For the inexperienced users (n = 11), the total number of blade-to-skin contacts was 356, 324 blade-to-skin contacts without the alarm and 32 with the alarm (90% reduction) (t₍₁₀₎ = -2.78, P = 0.009), averaging 26.5 more blade-to-skin contacts without the alarm. The median blade-to-skin contact duration for the novice was 0.313 seconds without the alarm and 0.1 seconds with the alarm (68% reduction). Contact time was reduced in both groups but failed to reach statistical significance. However, alarm use significantly reduced the number of touches of > 0.5 seconds duration (62 vs. 3) in the novice group, P = 0.0176. Blade-to-skin contact of > 0.5 seconds were felt to represent touches that were more likely to result in thermal injury to a living patient. Conclusion: Blade-to-skin contact can be reduced with the use of a cast-saw alarm. These effects appear most amplified in users with little prior cast-saw experience.