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Volume VII, Number 1 | April 2023

The Pressure is On: Dorsal versus Volar Univalves for Long Arm Casts

1Udall D, 2Schlechter J
1Riverside University Health System, Moreno Valley, CA, USA; 2Childrens Hospital of Orange County, Orange, CA, USA

Fiberglass casts are routinely used to treat fractures of the upper extremity. In settings where post traumatic edema is anticipated, the cast is often valved in hopes of preventing potential complications of an excessively tight cast with the most clinically significant being compartment syndrome. There are several studies in the literature looking at different methods for valving casts including univalves, bivalves, how they affect structural stability, and the utilization of cast spacers. However, there is a paucity of information analyzing the difference between a volar and dorsal univalve and its effect on the volar skin surface pressures. These volar skin surface pressures are of utmost importance due to the volar forearm compartments being the most affected in forearm compartment syndrome. 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.

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. Each cast was applied in a standard fashion by a single certified orthopedic technologist (OTC) who has over 30 years of experience in the field. Each group consisted of 7 individually applied casts. Group I received a volar univalve. Group II received a dorsal univalve. We calculated the change in volar forearm skin surface pressures on each cast in four stages: the univalve, the univalve with a 3mm cast spacer, the univalve with a 6mm spacer, and a bivalve.

Statistical analysis of the data was performed using a Mann Whitney U test. The change in volar forearm skin surface pressures, volar versus dorsal univalve, dropped by a mean of 32.00 mmHg versus 20.43mmHg (p-value = 0.001) in stage I, 45.14mmHg versus 38.00mmHg in stage II (p-value = 0.026), 56.53mmHg versus 49mmHg in stage III (p-value = 0.001). There was no significant difference between the two groups after a bivalve was performed at stage IV (p-value = 0.318).

Volar univalves on a long arm cast significantly reduced the volar forearm skin surface pressures compared to dorsal univalves. Given the dramatic consequences of volar forearm compartment syndrome, in addition to being the compartment most likely to develop compartment syndrome in the upper extremity, we feel it prudent to do whatever is possible to mitigate this area of concern. We know that a bivalved cast will cause the greatest decrease in skin surface pressures. However, it has already been shown that a single univalved cast (volar or dorsal) will retain a three-point mold better than a bivalved cast. In rare circumstances where the suspicion for impending compartment syndrome is clinically high, we would defer to the treating physician as to their choice of immobilization and/or treatment for the injury. However, in the setting of a clinically stable patient without concern for acute compartment syndrome at the time of intervention, we feel that a single volar univalve with a cast spacer set at 6mm will provide the greatest reduction of skin surface pressure while still maintaining the reduction of the fracture.

The Journal of the American Osteopathic Academy of Orthopedics

Steven J. Heithoff, DO, FAOAO

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