Complications following closed reduction and casting of pediatric forearm fractures are rare, but they do occur. Arguably the most devastating of these complications is the risk of developing compartment syndrome or Volkmann contracture secondary to injury-associated swelling under a circumferential cast.1-4 The peak in swelling can develop from 4 to 24 hours following the initial cast application,5 and as such, medical providers may not be able to identify it early because most children are discharged following closed reductions. For this reason, many providers implement prophylactic measures to minimize pressure-related complications.
A popular method for reducing pressure accumulation within a cast is to valve, or cut, the cast. Previous investigations have shown that cast valving results in significant reductions in cast pressure.2,6-9 Bivalving a circumferential cast results in significantly greater reductions in cast pressure when compared with univalve techniques;6,7,9 however, bivalving has also been shown to result in significant impairment in the structural integrity of the cast.10 An additional method to facilitate cast pressure reduction without impairing the structural integrity of the cast that accompanies a bivalve is to incorporate a cast spacer with a univalve technique to hold the split cast open.11 Although this method is commonly used in clinical practice, its ability to mitigate cast pressures has not previously been investigated.
The goal of this study is to investigate the influence of incorporating cast spacers with valved long-arm casts. We hypothesized that cast spacers would provide a greater pressure reduction for both univalved and bivalved casts when compared with the use of an elastic wrap. Additionally, we proposed that by incorporating a cast spacer with a univalved cast, we could attain pressure reduction equivalent to that of a bivalved cast secured with an elastic wrap.
MATERIALS AND METHODS
Upon receiving approval from the Institutional Review Board, experimental testing began with the application of 30 total casts performed on uninjured adult human volunteers. Pressure readings were provided with the use of a bladder from a pediatric blood pressure cuff (Welch Allyn Inc), as previously described.6 The bladder was placed on the volar aspect of the volunteer’s forearm, held in place with a 3-in diameter cotton stockinet (3M). Cotton cast padding (Webril-Kendall) was applied, 3 in wide and 2 layers thick, and a long-arm cast was applied, 2 layers thick with 3-in wide fiberglass casting material (Scotchcast Plus Casting Tape; 3M).
Once the cast was applied and allowed to set, the blood pressure bladder was inflated to 100 mm Hg. After inflation, forearm cast circumference was measured at 2 set points, assessed at points 2 cm distal to the elbow flexor crease and 10 cm distal to the previous point (Figure 1). Using these data, we calculated estimated cast volume using the volumetric equation for a frustum. Following this point, casts were split into 2 experimental groups, univalve or bivalve, with 15 casts comprising each group. The univalve group consisted of a single cut along the dorsum of the extremity, and the bivalve group incorporated a second cut to the volar extremity. Cast valving was performed using an oscillating cast saw (Cast Vac; Stryker Instruments), with care taken to ensure the continuity of the underlying cast padding.
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