Thermal Risk During Bivalving of Fiberglass Casts Following Orthopaedic Reduction: A Comparative Analysis of 2 Commercially Available Cast Padding Products.

Abstract

Background: Cast saw burns (CSBs) are a preventable, iatrogenic complication that may occur during bivalving or removal of fiberglass casts. Children undergoing fracture reduction with the use of procedural sedation, typically in the emergency department (ED), are at heightened risk for CSBs because they cannot provide real-time pain feedback during cast saw use. While prior investigations have examined the effects of cast material, cast thickness, and water dip temperature, the comparative thermal performance of commercially available cast padding products during cast bivalving has not been systematically evaluated. This study used thermal probes to compare measured temperatures beneath 2 widely used cast padding products, Webril (Kendall/Cardinal Health) and Specialist (BSN Medical), during a standardized cast application, molding, and bivalving protocol.

Methods: A custom upper-extremity model was instrumented with 2 calibrated thermocouples (labeled "near" and "far"). Twenty experimental runs were performed, 10 each per padding product, with bivalving performed separately for near and far probes (N=40 total). Temperatures were recorded at 3 time points: baseline (before the application of any materials), prebivalve (immediately after fiberglass application ), and at maximum temperature during bivalving with an oscillating cast saw. The primary outcome was the change in temperature from prebivalve to maximum bivalve temperature (ΔT) measured by near and far probes. Secondary outcome included maximum temperatures relative to established burn injury thresholds.

Results: The mean ΔT during bivalving was 13.2±13.0°C for Specialist padding and 13.0±6.9°C for Webril padding ( P =0.95). The mean absolute maximum temperature was 40.8±13.2°C for Specialist and 39.5±6.8°C for Webril. In the Specialist group, 6/10 runs exceeded the 44°C adult burn threshold on at least one probe, compared with 4/10 runs in the Webril group. Linear mixed-effects analysis with Kenward-Roger degrees of freedom revealed a significant material×probe interaction during bivalving ( P =0.020): at the near probe, Specialist peak temperatures averaged 8.5°C higher than Webril ( P =0.041), whereas the 2 materials did not differ significantly at the far probe ( P =0.146).

Conclusion: Maximum temperatures exceeded clinically relevant burn thresholds in both cast padding groups, supporting the high-risk thermal environment at cast mold sites during bivalving. While Webril had some protective effect, neither commercially available cast-padding product provided consistently sufficient or statistically superior thermal protection.

Levels of evidence: Not applicable (biomechanical study).