Skin surface pressures under short leg casts

Extremity Pressure in Splints Wrapped With an Elastic Bandage Versus Bias Cut Stockinette: An Experimental Model

BACKGROUND

Many variables affect the pressure caused by splinting or casting. The purpose of this study was to compare pressure underlying a splint wrapped with either an elastic bandage or a bias cut stockinette.

METHODS

Thirty-two plaster volar resting splints were applied to a simulated extremity with a saline bag secured to it. A pressure transducer was connected to the saline bag to monitor changes in pressure once splints were applied, and 15 mL increments of saline were added to the bag to simulate swelling. Each dressing type was tested with normal application and tight application.

RESULTS

Normal application splints wrapped with either bias cut stockinette or an elastic bandage demonstrated similar initial splint pressures (P = .81). With simulated swelling, splints wrapped with bias cut stockinette demonstrated a 15 mmHg (95% confidence interval [CI], 1.5-28.5) higher average pressure than those wrapped with an elastic bandage (P = .035). Tight application splints with an elastic bandage wrap demonstrated a 46 mmHg (95% CI, 16-77) higher initial splint pressure than those wrapped with bias cut stockinette (P = .009).

CONCLUSIONS

Splints wrapped using either an elastic bandage or bias cut stockinette appear to have a similar safety profile, although in cases of excessive swelling, an elastic bandage may provide additional compliance. Tight splint application appears to be more hazardous with the use of an elastic bandage compared with a bias cut stockinette. Further study of the use of elastic bandages and bias cut stockinettes in the clinical setting may be warranted.

Effects of Upper Extremity Elevation on Intra-Cast Pressure and Digital Perfusion in a Fiberglass Short-Arm Cast Model

The goal of this study was to determine the relationship of digital artery pressure to arm position and forearm skin surface pressure using a short-arm cast experimental setup, to ascertain the safest position for the injured casted upper extremity. A total of 27 volunteers were placed in bilateral short-arm fiber-glass casts with an empty 50-mL bladder bag under the cast and attached to a pressure transducer. Digital systolic pressure (P_dig), and skin surface pressure under the cast (P_skin) were assessed in 4 positions. Measurements were taken with and without 50 mL air in the bladder bag. A total of 54 forearms were evaluated. Both arm position and P_skin had a significant effect on P_dig (P<.001 for both), with increasing elevation leading to a decrease in P_dig (r=-0.50). The effect size of position on P_dig was large, whereas that of Pskin was small (partial eta-squared=0.371 and 0.028, respectively). Linear regression analysis of P_skin and P_dig with air in the neutral position yielded a moderate negative relationship with body mass index (r=-0.64, P<.001 for P_skin; r=0.49, P<.001 for P_dig) and wrist circumference (r=-0.66, P<.001 for P_skin; r=0.52, P<.001 for P_dig), without significant association with forearm length. For volunteers with short-arm fiberglass casts, increasing arm elevation had a large effect size on digital arterial pressure, whereas 50 mL simulated swelling had only a small effect size. Decreasing body mass index and forearm circumference correlated with increased skin surface pressure and decreased digital arterial pressure. These findings show that aggressive elevation of the injured limb may not be as desirable as previously believed. [Orthopedics. 2021;44(4):e487-e492.].

Patients’ perspectives on the conventional synthetic cast vs a newly developed open cast for ankle sprains

BACKGROUND

Orthopedic physicians typically apply a cast to immobilize a body part that has been injured. There have been no significant structural changes or advances in synthetic casts since the development of the modern cast. The Opencast^® is a recently developed type of cast that allows ventilation and direct visual inspection of the skin to avoid cast-related complications. Although this novel cast appears to have more benefits than the conventional synthetic cast, its clinical efficacy and advantages have not been established.

AIM

To investigate the clinical efficacy and advantages of the newly developed Opencast^® based on patients’ perspectives in those with ankle inversion injury.

METHODS

A specifically designed questionnaire consisting of 19 items was used to compare patients’ opinions and concerns of the Opencast^® and the conventional synthetic cast. The items were focused on subjective patient satisfaction, discomfort, and adverse effects while wearing the cast. Patients with an ankle inversion injury diagnosed as a high-grade ankle sprain were enrolled. The subjects were randomized and instructed to fill the questionnaire after wearing a synthetic cast or an Opencast^® for 2 wk. They were then required to fill the questionnaire again, after switching to the alternative type of cast for 2 more weeks.

RESULTS

A total of 22 subjects participated in the study. The synthetic cast appeared to be more rigid and stable than the Opencast^®, but there was no significant difference in the amount of pain relief. The likelihood of adverse effects when wearing the synthetic cast was significantly higher. Patient satisfaction tended to be rated higher after wearing the Opencast^®. Opencast^® showed more subjective vulnerability than the synthetic cast, but there was no significant difference in the redo rate. Patients were more anxious about removal of the synthetic cast than of the Opencast^®.

CONCLUSION

The results indicate that the Opencast^® could replace the conventional synthetic cast as it offers increased patient satisfaction, which would in turn increase compliance to treatment.

Under Pressure: The Utility of Spacers in Univalved Fiberglass Casts

BACKGROUND

Univalving fiberglass casts after fracture manipulation or extremity surgery reduces the risk of developing compartment syndrome (CS). Previous experiments have demonstrated that univalving decreases intracompartmental pressures (ICPs), but increases the risk for loss of fracture reduction due to altering the mechanical properties of the cast. The purpose of this study was to correlate cast valve width within a univalved cast model to decreasing ICP.

METHODS

Saline bags (1 L) were covered with stockinette, Webril, and fiberglass tape then connected to an arterial pressure line monitor. Resting pressure was recorded. A water column was added to simulate 2 groups (n=5 each) of clinical CS: low pressure CS (LPCS range, 28 to 31 mm Hg) and high pressure CS (HPCS, range, 64 to 68 mm Hg). After the designated pressure was reached, the fiberglass was cut (stockinette and Webril remained intact). Cast spacers were inserted into each univalve and secured with varying widths: position #1 (3 mm wide), #2 (6 mm), #3 (9 mm), and #4 (12 mm). Pressure was recorded after cutting the fiberglass and following each spacer placement.

RESULTS

In LPCS and HPCS groups, after univalve and placement of spacer position #1, pressure dropped by a mean of 52% and 58%, respectively. Spacer #2, decreased the pressure by a mean of 78% and 80%, respectively. Both spacer sizes significantly decreased the underlying pressure in both groups. Spacer #3 and #4 progressively reduced pressure within the cast, but not statistically significantly more than the previous spacer widths.

CONCLUSIONS

This experimental model replicates the iatrogenic elevation in interstitial compartment pressure due to rigid cast application, not necessarily a self-sustained true CS. Increasing the univalved cast spread by ≥9 mm of the initial cast diameter will reduce pressure to a pre-CS level; however, a spread of only 6 mm can effectively reduce the pressure to <30 mm Hg depending on the initial elevated ICP. Cutting the Webril and stockinette in our model yielded a pressure decrease of 91% and 94% from the starting experimental pressure in the LPCS and the HPCS groups, respectively.

CLINICAL RELEVANCE

Although the utility of splitting fiberglass casts has been previously demonstrated, we present evidence highlighting the benefit of spacing the split by at least 6 to 9 mm.

Reducing the Incidence of Cast-related Skin Complications in Children Treated With Cast Immobilization

BACKGROUND

Cast immobilization remains the mainstay of pediatric orthopaedic care, yet little is known about the incidence of cast-related skin complications in children treated with cast immobilization. The purposes of this quality improvement project were to: (1) establish a baseline rate of cast-related skin complications in children treated with cast immobilization, (2) identify trends in children who experienced cast-related skin complications, (3) design an intervention aimed at decreasing the rate of cast-related skin complications, and (4) determine the effectiveness of the intervention.

METHODS

A prospective interrupted time-series design was used to determine the incidence of cast-related skin complications overtime and compare the rates of skin complications before and after an intervention designed to decrease the incidence of cast-related heel complications. All consecutive patients who were treated with cast immobilization from September 2012 to September 2014 were included. A cast-related skin complications data collection tool was used to capture all cast-related skin complications. A high rate of heel events was noted in our preliminary analysis and an intervention was designed to decrease the rate of cast-related skin complications, including the addition of padding during casting and respective provider education.

RESULTS

The estimated cast-related skin events rate for all patients was 8.9 per 1000 casts applied. The rate for the total preintervention sample was 13.6 per 1000 casts which decreased to 6.6 in the postintervention sample. When examining the heel-only group, the rate was 17.1 per 1000 lower extremity casts applied in the preintervention group and 6.8 in the postintervention group.

CONCLUSIONS

Incorporating padding to the heel of lower extremity cast was an effective intervention in decreasing the incidence of cast-related skin complications in patients treated with cast immobilization.

LEVEL OF EVIDENCE

Level II.

Valve or No Valve: A Prospective Randomized Controlled Trial of Casting Options for Pediatric Forearm Fractures

The purpose of this study was to determine the rate of cast-related complications when using split or intact casts. A total of 60 patients aged 3 to 13 years with closed shaft or distal third radius and ulna fractures requiring reduction were recruited for this study. Patients underwent closed reduction under sedation and were placed into a long-arm fiberglass cast with 1 of 3 modifications: no valve, univalve, or bivalve. Patients were followed to 6 weeks after reduction or surgical treatment if required. The frequency of neurovascular injury, cast saw injury, unplanned office visits, and cast modifications, the need for operative intervention, and pain levels through the follow-up period were recorded. The results showed no incidents of compartment syndrome or neurovascular injury. Additionally, there were no differences between complications associated with cast type (P=.266), frequency of cast modifications (P=.185), or subsequent need for surgical stabilization (P=.361). Therefore, cast splitting following closed reduction of low-energy pediatric forearm fractures does not change clinical outcomes with respect to neurovascular complications, cast modifications, pain levels, or the need for repeat reduction. Consideration should be given to minimizing cast splitting after reduction of low-energy pediatric forearm fractures for practice efficiency and to potentially decrease saw-related injury. [Orthopedics. 2017; 40(5):e849-e854.].

Litigation related to casting in Orthopaedics-An analysis of claims against the National Health Service in England

Orthopaedic casts have been used to treat musculoskeletal conditions for hundreds of years and are still a fundamental component of treating a variety of disorders. As surgical techniques have advanced the frequency of use of orthopaedic casts has declined. With Orthopaedics being is one of the most litigious specialties in medicine we sough to evaluate how this related to casting in Orthopaedics and how we could learn from past mistakes. We analysed litigation claims related to Orthopaedic casts from 1995 to 2010 in which the claims were closed. 43 cases were related to orthopaedic casts. The total costs of these claims were over £2.3 million with an average total cost of £48,500 per claim. The most common cause for claim was harm caused when a cast was applied too tight and secondly from removing the cast. This is the first study to evaluate litigation claims related to Orthopaedic casts and highlights potential complications that if avoided will certainly improve the care of the patients and avoid unnecessary litigation.

Lower limb intracast pressures generated by different types of immobilisation casts

AIM

To determine if complete, split casts and backslabs [plaster of Paris (POP) and fiberglass] generate different intracast pressures and pain.

METHODS

Increased swelling within casts was modeled by a closed water system attached to an expandable bag placed directly under different types of casts applied to a healthy lower limb. Complete fiberglass and POP casts, split casts and backslabs were applied. Twenty-five milliliter aliquots of saline were injected into the system and the generated intracast pressures were measured using a sphygmomanometer. The subject was blinded to the pressure scores to avoid bias. All casts were applied to the same right limb on the same subject to avoid the effects of variations in anatomy or physiology on intracast pressures. Pain levels were evaluated using the Visual Analogue Score after each sequential saline injection. Each type of cast was reapplied four times and the measurements were repeated on four separate occasions. Sample sizes were determined by a pre-study 90% power calculation to detect a 20% difference in intracast pressures between cast groups.

RESULTS

A significant difference between the various types of casts was noted when the saline volume was greater than 100 mL (P = 0.009). The greatest intracast pressure was generated by complete fiberglass casts, which were significantly higher than complete POP casts or backslabs (P = 0.018 and P = 0.008 respectively) at intracast saline volumes of 100 mL and higher. Backslabs produced a significantly lower intracast pressure compared to complete POP only once the saline volume within casts exceeded 225 mL (P = 0.009). Intracast pressures were significantly lower in split casts (P = 0.003). Split POP and fiberglass casts produced the lowest intracast pressures, even compared to backslabs (P = 0.009). Complete fiberglass casts generated the highest pain levels at manometer pressures of 75 mmHg and greater (P = 0.001). Split fiberglass casts had significantly reduced pain levels (P = 0.001). In contrast, a split complete POP cast did not produce significantly reduced pain levels at pressures between 25-150 mmHg. There was no difference in pain generated by complete POP and backslabs at manometer pressures of 200 mmHg and lower.

CONCLUSION

Fibreglass casts generate significantly higher intracast pressures and pain than POP casts. Split casts cause lower intracast pressures regardless of material, than complete casts and backslabs.

Effect of Casting Material on the Cast Pressure After Sequential Cast Splitting

BACKGROUND

Circumferential casting is a vital component of nonoperative fracture management. These casts are commonly valved to release pressure and decrease the risk of complications from swelling. However, little information exists regarding the effect of different casting supplies on the pressure within the cast.

METHODS

Seventy-five long-arm casts were performed on human volunteers, divided between 5 experimental groups with 15 casts in each groups. Testing groups consisted of 2 groups with a plaster short-arm cast overwrapped with fiberglass to a long arm with either cotton or synthetic cast padding. The 3 remaining groups included fiberglass long-arm casts with cotton, synthetic, or waterproof cast padding. A pediatric blood pressure cuff bladder was placed within the cast and inflated to 100 mm Hg. After inflation, the cast was sequentially released with pressure reading preformed after each stage. Order of release consisted of cast bivalve, cast padding release, and cotton stockinet release. After release, the cast was overwrapped with a loose elastic bandage. Difference in pressure readings were compared based upon the cast material.

RESULTS

Pressures within the cast were found to decrease with sequential release of cast. The cast type had no effect of change in pressure. Post hoc testing demonstrated that the type of cast padding significantly affected the cast pressures with waterproof padding demonstrating the highest pressure readings at all time-points in the study, followed by synthetic padding. Cotton padding had the lowest pressure readings at all time-points.

DISCUSSION

Type of cast padding significantly influences the amount of pressure within a long-arm cast, even after bivalving the cast and cutting the cast padding. Cotton cast padding allows for the greatest change in pressure.

CLINICAL RELEVANCE

Cotton padding demonstrates the greatest change in pressure within a long-arm cast after undergoing bivalve. Synthetic and waterproof cast padding should not be used in the setting of an acute fracture to accommodate swelling.

The effectiveness of bivalving, cast spreading, and webril cutting to reduce cast pressure in a fiberglass short arm cast

BACKGROUND

A fiberglass short arm cast can be used to treat a distal radial fracture, but posttraumatic edema may lead to excessive cast tightness and resultant soft-tissue injury. We sought to quantify a simulated edema-induced pressure within a fiberglass short arm cast and to determine the effectiveness of different cast-cutting methods for pressure reduction. We hypothesized that cast cutting could eliminate all clinically relevant pressure and Ace wrap would insignificantly increase pressure.

METHODS

Skin surface pressure under fiberglass short arm casts was measured on ninety wrists from forty-five volunteers randomly assigned to one cast-cutting method: single-cut (cast bivalve and Ace wrap), double-cut (cast bivalve, spread, and Ace wrap), or triple-cut (cast bivalve, spread, Webril cut, and Ace wrap). Each wrist was immobilized in a cast in the neutral position with one roll of 2-inch (5.1-cm) cotton Webril and one roll of 2-inch (5.1-cm) fiberglass. Each fiberglass short arm cast contained an empty intravenous fluid bag in which we infused air. This simulated edema, which generated a skin surface pressure, which was measured by a pressure transducer.

RESULTS

Each cast-cutting method significantly reduced (p < 0.0001) the skin surface pressure from the average maximum of 92.5 mm Hg in a non-fracture setting. Prior to Ace wrapping, there was a reduction in skin surface pressure of 70.8% for the single-cut method, 85.1% for the double-cut method, and 99.9% for the triple-cut method. Ace wrap significantly increased skin surface pressure (p < 0.0001), lessening the effectiveness of cast cutting. There was an overall reduction in skin surface pressure of 55.9% for the single-cut method, 64.3% for the double-cut method, and 77.2% for the triple-cut method. Throughout our study, women had significantly higher skin surface pressure than men (p < 0.0001); the average maximum was 104.4 mm Hg for women and 81.1 mm Hg for men.

CONCLUSIONS

The single-cut method provides the greatest pressure reduction, but only the triple-cut method eliminated all relevant skin surface pressure. Ace wrapping a cut cast noticeably increased skin surface pressure.

CLINICAL RELEVANCE

In volunteers without a fracture, only the triple-cut method is effective enough to eliminate clinically relevant skin surface pressure. Ace wrap should be applied with caution after the cast is cut. The specific effect on pressure reduction in a patient who requires some soft-tissue pressure to maintain fracture reduction was not studied.

Cast-saw injuries: assessing blade-to-skin contact during cast removal. Does experience or education matter?

BACKGROUND

Cast-saw injuries are sustained during cast removal or splitting of a cast when a hot cast-saw blade touches the patient's skin inadvertently during cast removal. Other studies have evaluated risk factors associated with saw-blade temperature, however, none have documented the number and duration of blade-to-skin contacts during cast removal.

METHODS

Using a pediatric long-arm model capable of detecting cast-saw blade contact, we tested the ability of health care providers to apply and remove casts before and after a brief education module. The total number and duration of "touches" between the saw and the model's "skin" were recorded. Correlations between user "touches," and experience and comparisons between pre- and post-education "touches" were performed.

RESULTS

Of the 18 study participants, 16 touched the model surface with the cast saw; 7 of the 18 participants maintained blade contact with the skin for > 1 second 22 times during the testing process. Participants with less experience averaged 20 (± 16) touches, whereas more experienced participants averaged 24 (± 19) touches (P = 0.7). Average number of touches was similar-before 22 (± 20) and after 25 (± 22); P = 0.5-participants completed an education module. No correlation between experience or participation in the education program was found with decreased number of blade-to-skin touches.

CONCLUSION

Nearly all clinicians inadvertently contacted the underlying skin with the cast-saw blade. In our limited sample size, experience and education did not prevent this; therefore, minimizing time of contact and blade temperature may be more important factors in minimizing cast-saw injuries.

External skeletal fixation of fractures in cattle

External skeletal fixation (ESF) is a versatile method for rigid immobilization of long bone fractures in cattle. Traditional ESF devices may be used in young calves for clinical management of open fractures. Transfixation pinning and casting is an adaptation of ESF principles to improve versatility and clinical management of selected fractures.

Bier block regional anesthesia and casting for forearm fractures: safety in the pediatric emergency department setting

BACKGROUND

Bier block regional anesthesia was first described in 1908; however, it is uncommonly used for fears of cardiac and neurological complications. Although recent studies have documented safe usage in an adult population, no study to date has investigated its use in a pediatric setting. In addition, most emergency departments feel that splint placement is safer than casting after acute forearm fracture reduction in the pediatric population. However, to our knowledge there is no such study that documents the complication rates associated with immediate casting. The goal of this study was to assess the safety and efficacy of Bier block regional anesthesia and immediate cast application after closed reduction of pediatric forearm fractures.

METHODS

A retrospective review was conducted of patients treated for forearm fractures in a 2-year period at a major metropolitan pediatric hospital. Rates of complications and length and costs of the 2 procedures were analyzed.

RESULTS

A total of 600 patients were treated with Bier block regional anesthesia and 645 were treated with conscious sedation for displaced fractures of the forearm in the 2-year study period. No complications requiring admission were seen in either group. No patient experienced compartment syndrome or a need for readmission secondary to cast application. 2.2% and 4.3% (P=0.0382) of patients in the Bier block and sedation groups, respectively, needed their cast bivalved secondary to swelling. The average time from initiation of procedural sedation to discharge was 1 hour and 42 minutes, whereas the time to discharge from initiation of Bier block regional anesthesia was 47 minutes (P<0.0001). The average cost for a patient treated with procedural sedation was $6313, whereas the average cost for the Bier block regional anesthesia group was $4956.

CONCLUSIONS

Bier block regional anesthesia is a safe, efficient, and cost-effective method of reducing pediatric forearm fractures. Immediate cast application can be used without fear of major complications.

LEVELS OF EVIDENCE

Level III--retrospective review.

Cast and splint immobilization: complications

During the past three decades, internal fixation has become increasingly popular for fracture management and limb reconstruction. As a result, during their training, orthopaedic surgeons receive less formal instruction in the art of extremity immobilization and cast application and removal. Casting is not without risks and complications (eg, stiffness, pressure sores, compartment syndrome); the risk of morbidity is higher when casts are applied by less experienced practitioners. Certain materials and methods of ideal cast and splint application are recommended to prevent morbidity in the patient who is at high risk for complications with casting and splinting. Those at high risk include the obtunded or comatose multitrauma patient, the patient under anesthesia, the very young patient, the developmentally delayed patient, and the patient with spasticity.

An experimental study of pressure-volume dynamics of casting materials

Casting materials are commonly used in a trauma and post-operative setting in orthopaedic practice. Swelling after trauma or surgery is universal, hence, the importance of understanding the pressure-volume dynamics of various materials commonly used for casting. This study attempts to define the pressure response of casts made from three commonly used materials to increasing volume, using a cylindrical model cast. Plaster of Paris (PoP), rigid fibreglass and semi-rigid non-fibreglass (Softcast) were chosen for comparison. Softcast had the best compliance and rate dependency characteristics, accommodating significantly more volume of fluid compared to plaster of Paris or Rigid fibreglass material. The latter two had similar compliance. All three materials demonstrated stress-relaxation which is of advantage in reducing peak pressures for a given volume change. This study shows that the casting materials behave in a viscoelastic manner, which allows them to accommodate more volume change than would otherwise be possible. The use of semi-rigid material may be safer than other materials as far as response to swelling (volume expansion) is concerned.

Skin surface pressure beneath an above-the-knee cast: plaster casts compared with fiberglass casts

Complications related to immobilization in a cast after an injury or an operation may be related to the materials used for the cast or to the techniques of application, or to both. To evaluate the widely held clinical opinion that the use of a fiberglass cast is dangerous and inappropriate when subsequent swelling of the extremity is anticipated, we studied the skin surface pressures that were generated beneath above-the-knee casts made with different materials and applied with different techniques. A prosthetic model of the lower extremity was designed with an expandable calf compartment to simulate swelling after an injury or an operation. With use of this model, we measured the skin surface pressure beneath a plaster-of-Paris cast, a fiberglass cast that had been applied with a standard technique, and a fiberglass cast that had been applied with a stretch-relax technique. The highest mean skin surface pressure after application of the cast (p < 0.001) and after simulated swelling of the limb (p = 0.04) was generated by the fiberglass cast that had been applied with a standard technique. The lowest mean skin surface pressure after application of the cast (p = 0.006), simulated swelling of the limb (p < 0.001), and all subsequent steps of the experimental protocol (p < 0.001) was generated by the fiberglass cast that had been applied with the stretch-relax technique. The mean skin surface pressure generated by the plaster cast and by the fiberglass cast applied with the standard technique did not return to the value before application of the cast until anterior and posterior longitudinal cuts had been made in the cast and the cast had been spread at those cuts. When the fiber-glass cast had been applied with the stretch-relax technique, the mean pressure returned to the baseline value after only an anterior longitudinal cut and spreading at that cut. The principal pitfall of the use of a fiberglass cast is related to the technique of application. When the fiberglass cast had been applied with the standard technique, it generated a mean skin surface pressure that was higher than that associated with the plaster cast and it accommodated simulated swelling poorly. When the fiberglass cast had been properly applied, with the stretch-relax technique, it generated a mean skin surface pressure that was significantly lower (p = 0.006) than that associated with the plaster cast and it better accommodated simulated swelling without the need to sacrifice the structural integrity of the cast.

Pressure generation beneath a new thermoplastic cast

A new cast immobilizer that is heat-shrunk to conform to an injured extremity was examined. The purpose of these studies was to compare pressures beneath the thermoplastic cast with those beneath fiberglass casts on a laboratory model and on the forearms of human volunteers. Pressures measured beneath fiberglass casts on metal cylinders averaged 36 mm Hg. Thermoplastic casts on the smaller cylinder that allowed 42% shrinkage produced a mean pressure of 25 mm Hg; those placed on the larger cylinder that allowed 17% shrinkage produced a mean pressure of 39 mm Hg. Pressures measured on the forearms of healthy volunteers averaged 22 mm Hg beneath fiberglass casts and 31 mm Hg beneath the thermoplastic casts. These pressures were considerably less than pressures that have been shown to occlude the microcirculation of the skin. Acute compartment syndromes result from swelling within a limited space and remain a serious concern clinically when swelling is anticipated under any type of constraining cast. The results of these studies indicate that the new cast should not produce a greater risk of circulatory compromise to the limb than previously used fiberglass materials.