Evaluation of the dermal effects of cast padding in coaptation casts on dogs

Abstract

Summary Three configurations of cast padding and no cast padding were evaluated for their effects on skin in dogs. Padding was placed over bony prominences, between bony prominences, and over both areas for full-length padding under short-limb walking casts applied to 1 pelvic limb of Greyhounds. Evaluations were performed by pressure measurement over the calcaneal tuberosity, measurement of skin thromboxane B2 (TxB2) concentrations in skin over bony prominences, and measurement of plasma TXB2 concentrations. Pressure studies were performed to evaluate cutaneous pressures related to no cast padding and various configurations of cast padding. Concentrations of TxB2 in the skin were determined to evaluate the skin inflammatory effects of no padding and the padding configurations, and TXB2 concentrations in the plasma were analyzed to ascertain whether they could be used to predict impending dermal pressure lesions. Flexion of casted limbs revealed the greatest pressure over the calcaneal tuberosity with full-length cast padding. This was followed in decreasing order by no cast padding, padding over the prominences, and padding between the prominences. Compared with all other bony prominences and padding configurations, TXB2 skin concentrations were significantly higher over the calcaneal tuberosity when no padding was used and over the lateral base of metatarsal V when padding was placed between the prominences. Over the calcaneal tuberosity, this was attributed to the sharpness of the prominence and its potential for movement. This high TxB2 concentration corresponded to the high pressure found in the pressure studies. Over the lateral base of metatarsal V, the increase in TxB2 concentration was related to the mass of the prominence and the tendency for localized padding to settle around the area. Although the fully padded cast produced the highest pressure over the calcaneal tuberosity in the pressure measurement studies, this form of padding had the lowest TXB2 skin concentrations over this prominence in the 7- day TXB2 measurement studies. This was attributed to compacting of cast padding over time with resultant decrease in pressure over the bony prominence. There were no significant differences in plasma TxB2 concentrations before and after casting. On the basis of cutaneous pressure measurements and or dermal or plasma TxB2 measurements after short-limb casts had been in place for 7 days, we concluded that absence of cast padding can cause dermal pressure injury over sharp prominences; in some areas, localized cast padding may settle around larger prominences, increase pressure, and potentiate dermal pressure injury; although pressure may be high after applying full-length cast padding, some compacting of the padding occurs, and this provides the best form of padding to prevent dermal pressure injury; and plasma TxB2 concentrations cannot be used to predict impending dermal pressure injury in a coaptation cast.