Hybrid casts: a comparison of different casting materials.

Casting and splinting materials used in orthopedics have historically consisted of plaster of Paris and, more recently, fiberglass. Plaster is cost-effective and malleable enough to help to hold reductions. Fiberglass is stronger and lighter, but more expensive. The hybrid cast of plaster and fiberglass optimizes the advantages of both materials in fracture management; it is sufficiently strong, yet still cost-effective.     

Is softcast (3M) strong enough for potentially unstable paediatric forearm fractures?

IntroductionThe majority of paediatric forearm fractures are treated using a circumferential splint, with prior manipulation as necessary. Plaster of Paris is often chosen for its ease of application, cost and proven reliability.Softcast is an alternative, providing a comfortable and water-resistant splint that can be removed without a plaster saw, and is in widespread use for immobilising buckle fractures. Softcast has not been recommended for acute unstable fractures. We established whether a Softcast splint could provide sufficient mechanical stability to control an unstable paediatric forearm fracture.MethodsA laboratory study was undertaken to compare the 3 point (kinking) and 4 point bending, and torsion loads to defined clinical failure points withstood by standardised 4-wrap POP compared to Softcast splints with 6-wrap, 4 wrap and reinforced 4-wrap configurations.ResultsThe load at clinically relevant failure of a 6-wrap Softcast forearm splint was 504 N in 4 point bending, 202 N in 3 point bending (kinking), and 11Nm in torsion (equalling 30.4%, 26% and 42.2% of the equivalent values for a circumferential 4-wrap POP). The 6-wrap Softcast was however stronger in all modes than a fibreglass-reinforced Softcast splint (previously recommended for acute fractures). Furthermore, the load to failure in all modes exceeds that which can be exerted by body weight in many paediatric patients.Softcast demonstrated complete recovery of its original shape on unloading, whereas POP was permanently deformed. 6-wrap Softcast splints were 4% lighter than POP.ConclusionA 6-wrap Softcast splint provides adequate mechanical stability and protection for paediatric patients up to approximately 20 kg, avoiding high-risk activities. The primary risk is not of fracture angulation and loss of position, but temporary indentation of the splint, causing discomfort or pain. Considering its ease of removal, Softcast may be preferable for younger paediatric patients. Its cost may be offset by reducing the number and duration of hospital visits.     

Mechanical properties and material characteristics of orthopaedic casting material

In this study, two types of orthopaedic casting materials were evaluated: the Johnson & Johnson Specialist plaster bandage and the 3M Scotch-cast Plus fiber glass bandage. The materials were evaluated using tensile tests to determine the elastic modulus, yield strength, and ultimate tensile strength. To determine the structural characteristics and stiffness of a cylindrical cast, each material was formed around a foam cylinder core and tested in a four-point bend jig. A computer-based model using the finite element method (FEM) was developed for a cylindrical cast of both types and compared with the experimental findings. A second FEM model with loads applied at the periphery was performed to simulate the clinical observations of plaster bandage breakdown at the ends of a cast. It is with these tests that the two bandage materials were compared and evaluated. It was concluded that the plaster bandage, while initially stiffer than the fiber glass bandage, had much lower yield stress. This implies that the plaster cast may break down under loads that would leave the fiber glass cast intact. It was also determined that the plaster bandage load displacement curve is bilinear. The bilinear characteristic of the plaster bandage explains its breakdown at the ends of a cast.     

PLASTER OF PARIS SPLINTAGE FOR THE HAND: VOLAR OR DORSAL?

The effectiveness of a volar or a dorsal plaster of Paris slab for splinting a hand in the ‘safe’ position was studied prospectively. Seventy-two splints, comprising 36 dorsal and 36 volar, were applied. Measurements of the metarcarpophalangeal joint angle and the proximal interphalangeal joint angle on the lateral radiograph revealed the volar splint to be significantly more consistent in securing the proximal interphalangeal joint angle at less than 15°. There was no significant difference between volar or dorsal splints for the metarcarpophalangeal joint angle. As the volar splint was also subjectively more comfortable, its use is recommended.     

Diagnosis of periprosthetic infection following total hip arthroplasty – evaluation of the diagnostic values of pre- and intraoperative parameters and the associated strategy to preoperatively select patients with a high probability of joint infection

Background

Most cast materials mature and harden via an exothermic reaction. Although rare, thermal injuries secondary to casting can occur. The purpose of this study was to evaluate factors that contribute to the elevated temperature beneath a cast and, more specifically, evaluate the differences of modern casting materials including fiberglass and prefabricated splints.

Methods

The temperature beneath various types (plaster, fiberglass, and fiberglass splints), brands, and thickness of cast material were measured after they were applied over thermometer which was on the surface of a single diameter and thickness PVC tube. A single layer of cotton stockinette with variable layers and types of cast padding were placed prior to application of the cast. Serial temperature measurements were made as the cast matured and reached peak temperature. Time to peak, duration of peak, and peak temperature were noted. Additional tests included varying the dip water temperature and assessing external insulating factors. Ambient temperature, ambient humidity and dip water freshness were controlled.

Results

Outcomes revealed that material type, cast thickness, and dip water temperature played key roles regarding the temperature beneath the cast. Faster setting plasters achieved peak temperature quicker and at a higher level than slower setting plasters. Thicker fiberglass and plaster casts led to greater peak temperature levels. Likewise increasing dip-water temperature led to elevated temperatures. The thickness and type of cast padding had less of an effect for all materials. With a definition of thermal injury risk of skin injury being greater than 49 degrees Celsius, we found that thick casts of extra fast setting plaster consistently approached dangerous levels (greater than 49 degrees for an extended period). Indeed a cast of extra-fast setting plaster, 20 layers thick, placed on a pillow during maturation maintained temperatures over 50 degrees of Celsius for over 20 minutes.

Conclusion

Clinicians should be cautious when applying thick casts with warm dip water. Fast setting plasters have increased risk of thermal injury while brand does not appear to play a significant role. Prefabricated fiberglass splints appear to be safer than circumferential casts. The greatest risk of thermal injury occurs when thick casts are allowed to mature while resting on pillow.     

Fixed-angle plate fixation in simulated fractures of the proximal humerus: a biomechanical study of a new device

This study was performed to evaluate the biomechanical properties of a new device for displaced fractures of the proximal humerus. The device is a low-profile, fixed-angle plate specially designed for percutaneous application. With the use of embalmed cadaveric humeri, we simulated both noncomminuted and comminuted 2-part surgical neck fractures of the proximal humerus. Each humerus of a pair was then randomly fixed with either the new experimental device or the Association for the Study of Internal Fixation (ASIF) T-plate and mechanically tested to failure in an axial shear-loading model. The two fixation devices were evaluated in paired humeri with regard to mode of failure, stiffness, displacement at physiologic loads, and displacement, load, and energy at the point of ultimate load before failure. In the noncomminuted fracture trials the experimental device exhibited significantly greater stiffness (P <.001; P =.002 for normalized values) and ultimate load before failure (P =.015) and significantly less displacement at higher physiologic loads (P =.031). In the comminuted fracture trials the experimental device exhibited significantly greater stiffness (P =.048), ultimate load (P <.001) and energy absorbed (P =.048) before failure, and significantly less displacement at higher (P =.004) and lower physiologic loads (P =.011). The study demonstrates improved biomechanical properties for the new experimental device over the T-plate in simulated fractures of the proximal humerus. We extrapolate that these improved biomechanical properties may prove advantageous in future clinical investigation.     

Plaster and synthetic cast temperatures in a clinical setting: an in vivo study

Previous studies have reported thermal injuries with thick cast materials and warm dip water temperatures, often much higher than is clinically applicable. The goal of this study was to assess the temperature produced in vivo by current casting techniques and materials. The study was done using clinically applicable materials and water temperatures. A single volunteer was used to test skin temperatures produced with various casting techniques. We tested several types of fiberglass and plaster of 5 or 10 layers, used soft roll of 1 or 3 layers, and used dip water temperatures of 30 °C and 40 °C. We tested 2 plaster types: Johnson & Johnson Specialist Fast Set and Specialist Extra Fast Set (New Brunswick, New Jersey). Fiberglass tested included 3M Scotchcast Poly Casting Tape and Scotchcast Plus (St Paul, Minnesota), Royce Medical Techform (Camarrillo, California), and DeBusk Classic Synthetic Tape (Powell, Tennessee). The highest temperature reached using 30 °C water temperature was 39 °C with 10 layers of 3M Scotchcast fiberglass and 1 layer of soft roll. The highest temperature reached with 40 °C water was 39.5 °C, which was reached twice: once with Johnson & Johnson Fast Set Plaster with 5 layers of plaster and 3 layers of soft roll, and once with DeBusk Classic Synthetic Casting Tape of 10 layers with 1 layer of soft roll. Under the clinically applicable conditions described in this study, using the materials we tested and with a normal vascular supply, it is unlikely that temperatures high enough to cause a burn will be produced. We caution that good clinical judgment is advised if a patient reports a cast is too hot.     

Splints and casts in the treatment of war injuries

The use of splints and casts in the treatment of war injuries varied according to the particular echelon of command in which they were required. In general, emergency splinting was effected with the regulation army halfring splint. For transportation following primary surgery plaster was almost universally employed. Definitive splinting in the Zone of Communication was accomplished by use of the halfring splint or plaster, frequently by a combination of the two. Internal splinting was, for the most part, reserved for the Zone of the Interior. Two points deserve especial attention; the use of splints in the protection of extensive soft tissue injuries during transportation and the abuse of splints in the treatment of fractures of the hand.     

Treatment of clubfoot with the Ponseti method: a comparison of casting materials

BACKGROUND: Popular initial treatment for congenital clubfoot includes the use of serial manipulations and casting as described by Ponseti et al. Plaster of Paris and semirigid fiberglass are 2 materials commonly used for casting. To our knowledge, no study to date has compared the clinical results of these 2 materials. The objective of this randomized prospective study was to compare the effectiveness of these materials in the initial management of clubfoot. METHODS: All clubfeet presenting to the 2 senior authors' outpatient clinics over a 15-month period were offered enrollment. Patients were randomly assigned for treatment with either plaster or semirigid fiberglass casts. The severity of the clubfoot deformity was documented using the scoring system devised by Diméglio et al. Serial casts were applied according to the technique described by Ponseti et al. At the completion of nonsurgical treatment, the final clubfoot severity was documented. RESULTS: A total of 42 clubfeet in 34 patients were enrolled in the study. After exclusion of 3 patients, 13 patients (16 feet) received fiberglass, and 18 patients (23 feet) received plaster casts. The mean baseline severity scores of the 2 groups were not significantly different. The mean final severity score was significantly higher in the feet treated with fiberglass than those treated with plaster (6.4 vs 4.1; P = 0.037). There was a trend toward higher scores for cast tolerance, durability, and parent satisfaction in the fiberglass group, but this did not reach significance. CONCLUSIONS: This study supports the use of plaster casting with the Ponseti technique. The use of plaster casts resulted in a statistically lower Diméglio-Bensahel score at the completion of serial casting. There was a trend toward higher patient satisfaction in the fiberglass-treated group. Whether this difference has an effect on long-term outcomes and recurrence remains to be studied. LEVEL OF EVIDENCE: Level II. Nonblinded randomized controlled prospective study.     

Biomechanical Stability of Four Fixation Constructs for Distal Radius Fractures

Implants available for distal radius fracture fixation include dorsal nonlocked plating (DNLP), volar locked plating (VLP), radial–ulnar dual-column locked plating (DCPs), and locked intramedullary fixation (IMN). This study examines the biomechanical properties of these four different fixation constructs. In 28 fresh-frozen radii, a wedge osteotomy was performed, creating an unstable fracture model and the four fixation constructs employed (DNLP, VLP, DCPs, and IMN). Dorsal bending loads were applied and bending stiffness, load to yield 5 mm displacement, and ultimate failure were measured. Bending stiffness for VLP (16.7 N/mm) was significantly higher than for DNLP (6.8 N/mm), while IMN (12.6 N/mm) and DCPs (11.8 N/mm) were similar. Ultimate load to failure occurred at 278.2 N for the VLP, 245.7 N for the IMN, and 52.0 N for the DNLP. The VLP was significantly stronger than the DNLP and DCPs, and the IMN and DCPs were stronger than the DNLP. The VLP has higher average bending stiffness, ultimate bending strength, and resistance to 5 mm displacement than the other constructs and significantly higher ultimate bending strength than the DCPs and DNLP. There was no statistically significant difference between the VLP and IMN. VLP and IMN fixation of distal radius fractures can achieve comparable stability.     

Orthopedic immobilization

The classical plaster bandage was devised in the mid 19th century. Until recently, osteoarticular trauma has been treated mostly by plaster cast immobilisation using plaster of Paris. Synthetic materials have been introduced on the market place in the seventies, but they have not superseded the traditional plaster of Paris. The more recent thermoplastic materials are used to make splints and orthoses, particularly at the wrist and hand. The present review of the literature confirms that synthetic materials present better physical and mechanical properties than the traditional plaster of Paris. In addition, they are lighter, they are more resistant to humidity, they are more radiotransparent and they generate less dust when removed. However, they are less malleable and cause higher pressure in case of limb edema. Plaster of Paris therefore remains indicated in the acute posttraumatic or postoperative period. This material is also cheaper, but the pecuniary benefit is limited for several reasons, particularly because plaster of Paris is associated with a higher rate of cast replacement.     

A novel technique for reduction and immobilization of tibial shaft fractures: the hammock

Standard techniques for immobilization of a tibia shaft fracture in the emergency department in a long-leg splint can be cumbersome, technically difficult, and often requires the use of an assistant. We have developed a novel technique for the reduction and splinting of tibial shaft fractures, which uses a "hammock" constructed of stockinette, which allows a single consulting orthopaedic physician to rapidly reduce and place a long-leg plaster splint or cast on a patient. This technique was performed on 12 consecutive patients with a total of 12 tibial shaft fractures. Translation, angulation, and shortening of the fracture were documented in anteroposterior and lateral views of the injured tibia and these parameters were compared against values measured after the hammock technique was used to reduce and splint the fracture. Pre-"hammock" average values for fracture displacement in the anteroposterior plane for translation, angulation, and shortening were 10.5 mm (53.1%), 12.0°, and 9.4 mm, respectively. Post-"hammock" average values for fracture displacement in the anteroposterior plane for the same parameters were 8.7 mm (44.4%), 4.2°, and 7.9 mm, respectively. Pre-"hammock" average values for fracture displacement in the lateral plane for translation and angulation were 4.9 mm and 8.7°. Post-"hammock" average values for fracture displacement in the lateral plane for the same parameters were 4.9 mm and 2.0°, respectively. These results show that this technique is able to achieve the goals of fracture reduction and immobilization in a rapid fashion when help is not available.     

新型塑质夹板的力学性能测试和分析

目的探讨新型塑质克雷氏夹板在不同力学状态下的力学参数,为临床应用提供依据.方法取6套塑质夹板和6套柳木夹板,随机分为2组,每组再随机编号,分别进行横向及纵向弯曲测试,得出两个方向的弯曲最大载荷和对应位移,并进行对比,从而也计算出两种夹板的弹性模量.结果在横向弯曲方向塑质夹板明显大于柳木夹板(P<0.01);在纵向弯曲方向两者无显著性差异(P>0.05).新型塑质夹板在不同受力状态下的弹性模量相同,而柳木夹板在不同受力状态下弹性模量不同,两者间有显著性差异(P<0.01).结论新型塑质夹板力学性质稳定,是一种理想的外固定材料.     

Three-dimensional analysis of the gap space under forearm casts

PurposeSecondary displacement represents a frequent complication of conservative treatment of fractures, particularly of the distal radius. The gap space between skin and cast may lead to a certain degree movements and this increased mobility might favor redisplacement. The aim of this study was to develop a new 3D method, to measure the gap space in all 3 geometrical planes, and to validate this new technique in a clinical setting of distal radius fractures.MethodsThis study applies 3D imaging to measure the space between plaster and skin as a potential factor of secondary displacement and therefore the failure of conservative treatment. We developed and validated a new methodology to analyze and compare different forearm casts made of plaster of Paris and fiberglass. An unpaired t-test was performed to document differences between the investigated parameters between plaster of Paris and fiberglass casts. The significance level was set at p < 0.05.ResultsIn a series of 15 cases, we found the width of the gap space to average 4 mm, being slightly inferior on the radial side. Comparing the two different casting materials, plaster of Paris and fiberglass, we found a significantly larger variance of space under casts made of the first material (p=0.39). A roughness analysis showed also a markedly significantly higher irregularity of the undersurface of plaster of Paris as compared with fiberglass.ConclusionThis study allows for a better understanding of the nature of the “gap space” between cast and skin and will contribute to develop and improve new immobilization techniques and materials.     

Editorial Commentary: Fascia Lata Allograft for Shoulder Superior Capsular Reconstruction: In the Fight Over Optimal Graft Choice for Irreparable Rotator Cuff Tears,Superior Capsular Reconstruction Proponents May Be Changing Their Gloves

Optimal treatment of irreparable rotator cuff tears is still debated. Proponents of the superior capsule reconstruction (SCR) have previously used fascia lata autograft and acellular dermal allograft. Interest is growing in using fascia lata allograft as a new graft material. Well-designed biomechanical studies are important to understand the mechanical properties of the superior capsular tissue and fascia lata allograft. Recent biomechanical research shows that fascia lata allograft has similar initial stiffness (over the first 2 mm) and ultimate load compared to the native superior capsule. That said, ultimate load is the load at which a construct fails, whereas the yield point is the load on the stress–strain curve at which a material transitions from elastic to plastic deformation. In the shoulder where the SCR, for example, is going to be repetitively loaded, it is potentially more meaningful to talk about the yield point in order to stay within the elastic range. Using this framework, the yield point for fascia lata allograft is approximately one third the yield point of native capsular tissue. Additionally, “initial” stiffness is not the entire story. At greater loads, fascia lata allograft has higher displacement compared to native tissue. Of importance, fascia lata allograft failed by sutures slowly cutting through the allograft tissue; this may represent a limitation of the construct that could be addressed using stitch configurations resistant to cut through. Fascia lata allograft is a promising solution for SCR. Biomechanical studies require nuanced interpretation, and most of all, do not evaluate clinical healing.     

Soak the cast off

Plaster of Paris cast is still the most common form of external splintage used in orthopaedics. It is usually removed by cutting it with an electric oscillating saw. The noise created by this instrument and the sight of the blade can both be frightening, particularly for young children. As Plaster of Paris gets soft with water, soaking it to remove plaster in children is a good option, particularly neonates treated by serial casting for clubfeet. Our experience with this method was very encouraging. There were no failures. Most patients or parents of neonates were satisfied and happy to remove the plaster at home. Average time taken to remove the plaster was 25 minutes.     

Experimental study on thermal burns caused by plaster bandage

Plaster bandage is frequently used in the field of orthopaedic surgery. Little is known however of thermal burns caused by plaster bandage. Experience has shown that heat producing levels differ depending on application conditions, i.e., water temperature into which plaster of Paris is dipped, thickness of the plaster cast, kind of plaster, etc. We made a series of experiments to find out what factors are related to elevation of the skin temperature in a plaster splint applied to a human forearm. The highest skin temperature of 47.7 degrees C was obtained upon application of a plaster bandage made of 30 layers of plaster with short setting time, dipped in water at 42 degrees C. In this condition the examinee had a first degree burn on the skin surface. Thus, care must be taken in applying a plaster bandage to assure that it does not cause a serious burn to the skin.     

Biomechanical stability of a volar locking-screw plate versus fragment-specific fixation in a distal radius fracture model

Eight matched pairs of cadaveric radii were osteotomized by removing a 4-mm dorsal wedge of bone at the level of the sigmoid notch designed to simulate dorsal comminution. They were then fixed with either a volar locking-screw plate or fragment-specific fixation. All constructs underwent biomechanical testing in a custom-designed, custom-fabricated 4-point bending device. No statistically significant difference in stiffness was noted between the groups. Linear displacement and angulation at the osteotomy site were significantly less in the group with fragment-specific fixation at loads expected to be encountered during postoperative rehabilitation. Angulation at the osteotomy site was significantly less in the locking-screw plate group at higher loads.     

Frozen storage increases the ultimate compressive load of porcine vertebrae

The use of freezing as a method of storage is commonplace in mechanical testing of biological tissues. The effects of freezing on tissues that comprise spinal segments have been examined separately, but little work has been done on intact specimens. We examined the effect of freezing on the structural properties of porcine cervical spines. The intact cervical spines of seven pigs (a total of 14 specimens–seven of C2–C4 and seven of C5–C7) were stored frozen (?20°C) for 1 month. The ultimate compressive load, displacement, stiffness, and energy absorbed were obtained using a monotonic compressive load applied at 3,000 N/sec. The structural properties were compared with those of another 14 porcine cervical specimens (control group, matched for age and weight) that were tested in a fresh state. The frozen storage of the vertebral specimens significantly increased the ultimate compressive load (24%) and energy absorbed to failure (33%). The stiffness and displacement at failure were not affected. We concluded that the use of freezing as a storage medium should be of concern when the resulting measures are used to quantify the ultimate compressive load of the spinal motion segments.     

Postoperative splinting of the pediatric upper extremity

The protective splint described above provides appropriate immobilization and protection for our postoperative pediatric population. The major advantages of this splint over plaster of paris include direct access to the wound, easy reapplication, and unnecessary use of the plaster-cast saw. In addition, thermoplastic splints are lightweight, less bulky, more durable, water-resistant, and easily remolded. The therapist's approach to the patient and parents is of utmost importance and will affect the outcome of the splint. In conclusion, postoperative pediatric splinting can be a challenging experience that requires a significant amount of patience, knowledge, and creativity on the part of the hand therapist.