The Pressure Is on: Dorsal Versus Volar Univalves for Long-arm Casts

Background:Fiberglass casts are routinely used to treat fractures of the upper extremity. When posttraumatic edema is anticipated, the cast is often valved to hopefully prevent potential complications, especially compartment syndrome. Due to volar forearm compartments being most involved with upper extremity compartment syndrome, volar skin surface pressures (SSP) are paramount. Despite past literature showing that a univalved cast will retain a 3-point mold better than a bivalved cast, there is a paucity of information analyzing the effects of univalving on the volar SSP. We hypothesized that a volar univalve technique would have a greater decrease in the volar skin surface pressures compared to a dorsal univalve in long-arm casts.Methods:A 100-mL saline bag attached to an arterial line pressure transducer was placed between a long-arm cast and the skin along the volar forearm of a single adult volunteer. Fourteen casts were applied by a single certified orthopaedic technologist with 30 years of experience and assigned randomly to receive either a volar or dorsal univalve. We calculated the change in volar forearm SSP on each cast in 4 stages: isolated univalve, with a 3-mm cast spacer, with a 6-mm spacer, and with bivalve. Statistical analysis of the data was performed using a Mann-Whitney U test.Results:When comparing volar versus dorsal univalve, volar SSP significantly dropped by a mean of 32.00 versus 20.43 mm Hg (P value=0.001) in stage I, 45.14 versus 38.00 mm Hg in stage II (P value=0.026), and 56.53 versus 49 mm Hg in stage III (P value=0.001). There was no significant difference between the 2 groups after a bivalve was performed at stage IV (P value=0.318).Conclusion:Our findings support that a volar univalve with a 6-mm spacer will provide the greatest reduction of skin surface pressure while theoretically maintaining the cast's structural integrity and biomechanical properties when compared to a bivalved cast.Level of Evidence:Level II, prospective comparative study.