574162 research-article2015
POI0010.1177/0309364615574162Prosthetics and Orthotics InternationalConner et al.
INTERNATIONAL SOCIETY FOR PROSTHETICS AND ORTHOTICS
Technical Note
Dilatancy-based impression and fabrication technique for custom foot orthoses
Prosthetics and Orthotics International 1–5 © The International Society for Prosthetics and Orthotics 2015 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0309364615574162 poi.sagepub.com
Larissa A Sletto, Yeongchi Wu and Christopher Robinson
Abstract Background and aim: Current methods used to take impressions for custom foot orthoses include plaster bandage, foam box, fiberglass, and laser-optical scanner. Impressions are converted to positive plaster or foam models. These methods create waste and may not be feasible in resource-limited areas. This technical note presents an alternative, greener impression and fabrication technique for foot orthoses that utilizes the dilatancy principle. Technique: Steps of the dilatancy (vacuum-based) procedure include taking an impression of the foot, converting the negative mold to a positive sand model, modifying the positive sand model, and thermoforming the foot orthosis. Discussion: This plaster-less system is inexpensive to set up and maintain, is reusable thereby minimizing cost and waste, and is clean to use. It enables a practitioner to quickly take an impression for fabricating a foot orthosis in a short period of time during a single clinic visit by the patient. Clinical relevance The dilatancy casting system could potentially be a cheaper, faster, and greener alternative procedure for fabricating custom foot orthoses in both developing and developed countries. Keywords Foot, orthosis, custom, impression, modification, fabrication, dilatancy, vacuum-based Date received: 21 June 2014; accepted: 22 January 2015
Background and aim Currently, there are four methods commonly used by practitioners to take impressions for custom foot orthoses: plaster bandage, foam box, fiberglass, and laser-optical scanner. Impressions are then converted to positive plaster or foam models. All of these methods create waste and may not be feasible in resource-limited areas. A new impression and fabrication technique utilizing the dilatancy principle, initially investigated by Mead,1 has been developed,2,3 field tested,4,5 and adapted for transtibial prostheses.6 In a continued attempt to reduce waste created and dependency on costly equipment, we adapted this plaster-less, dilatancy prosthetic technique for fabrication of custom foot orthoses.7,8 This technical note describes this adapted procedure.
reservoir tank, the equipment needed is listed below. Please note that exact dimensions are not critical. Materials needed to create the equipment can be purchased at hardware stores.
Technique
Northwestern University Prosthetics-Orthotics Center, Chicago, IL, USA
Set-up In addition to a heating oven, a vacuum pump with a negative pressure of −25 to −27 inHg, and a minimum 30 gallon
1. Casting bag. The bag (Figure 1(a)) is approximately 36 × 50 cm2, is made of elastic fabric, is filled approximately 70% volume-wise with micropolystyrene beads, has a connector for vacuum, and has a capped opening for filling with polystyrene beads. 2. Casting frame. The u-shaped frame (Figure 1(b)), slightly shorter than the casting bag, comprises a plywood base with length-wise wooden side bars.
Corresponding author: Larissa A Sletto, Northwestern University Prosthetics-Orthotics Center, 680 N Lake Shore Dr, Chicago, IL 60611, USA. Email: [email protected]
Downloaded from poi.sagepub.com at Bobst Library, New York University on November 16, 2015
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Prosthetics and Orthotics International
Figure 1. (a) The casting bag is placed over (b) the casting frame to take (c) an impression.
Figure 2. The design of manifold (left) and vacuum mandrel (right) include connectors to (a) vacuum pump and (b) casting bag and thermoforming set up with (c) bleeders, (d) air flow valves, (e) glass-bottle air filter, (f) felt-covered ends to filter sand, and (g) formed positive sand model.
3. Plastic bags. Bags approximately 45 × 75 cm2 and 0.50–1.00 mm thick are used as air-tight, flexible containers throughout the process. 4. Vacuum control manifold. Comprising steel pipes, this manifold (Figure 2, left) connects the vacuum source to the casting bag and the positive sand model. Ball-type valves are used to control vacuum air flow. The air filter prevents sand from entering the vacuum pump. 5. Air hoses. Four flexible rubber tubes run from the manifold to the vacuum source, to the casting bag (impression), to the vacuum mandrel (positive sand model), and outside the positive sand model (vacuum forming). Tubes should be thick enough that they do not collapse under vacuum. 6. Vacuum mandrel. Used to vacuum form the positive sand model, this mandrel (Figure 2, right) comprises steel pipes, an air hose connector, felt filters, and a wooden base. The felt filter on the
7.
8. 9. 10.
vacuum mandrel can be replaced whenever dust accumulation is noticed in order to prevent dust from reaching the filter on the vacuum control manifold or entering the air filter on the vacuum pump. If this is done on an as-needed basis, manifold filter replacement should rarely be needed. Vacuum mandrel hose. A non-collapsible, flexible air hose with a quick disconnect female adapter on one end and a male adapter on the other is used to connect the mandrel to the manifold. Nylon socks. Low elasticity socks are used for the negative to positive model conversion process and for vacuum forming. Sand. Clean, dust-free (20 grit) sand is ideal for creating a smooth positive model. Local sand can be utilized if cleaned and sifted. General supplies. Electrical tape, scissors, a hammer, an awl, Pe-Lite, Plastazote, and a round rod will be utilized.
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Sletto et al.
Figure 3. Steps of (a–c) taking an impression and (d–g) converting to a (h) positive sand model.
Taking an impression (negative mold) 1. Place the casting bag in a new plastic bag and use electrical tape to seal the plastic bag to the air hose (Figure 1(a)). 2. With the patient seated and the foot covered with a nylon stocking, take a coronal diameter (ML) measurement at the metatarsal heads. 3. Place the casting bag on top of the casting frame (Figure 1(b)). Push casting bag beads to the sides and ends and drape the bag over the anterior and posterior ends of the casting frame. The frame limits length-wise shortening of the casting bag when vacuum is applied. 4. With the patient seated, have the patient place their foot on the casting bag and shift the foot anteriorly and posteriorly until the foot is flat on the baseboard of the frame. Check alignment of the talocrural and subtalar joints in both the coronal and sagittal planes and adjust the patient’s lower limb accordingly. 5. Apply partial vacuum by partially opening the vacuum control valve and opening the bleeder valve so that the casting bag can be molded to cover just above the intended trim lines. While under partial vacuum, push beads away from the patient’s toes to create an extended footplate for a full-length custom foot orthosis. In addition, push beads slightly away from the sides of the first and fifth metatarsal heads to create pressure reliefs. 6. While holding the casting bag over the ends of the casting frame, apply full vacuum to solidify the bag. Make the patient to stand in the mold to check for total contact and comfort (Figure 3(b)). Remove the patient’s foot and inspect the impression (Figures 1(c) and 3(c)). If necessary, repeat the impression process.
Converting to positive sand model 1. Place a new plastic bag in the impression (Figure 3(d)) with the seam of the bag “outside of the trim lines.” 2. Pour approximately two cups of sand into a nylon stocking and place the stocking in the plastic bag that was placed in the impression. Add enough sand into the nylon stocking to fill the negative mold and pack the sand down (Figure 3(d)), particularly in the heel so that the heel is fully captured. Next, with the mandrel positioned such that the valve is posterior, push the vacuum mandrel into the sand close to the heel. Without tension on the plastic bag, tape and seal the bag to the mandrel with electrical tape (Figure 3(e)). 3. Connect the mandrel to the manifold using the vacuum mandrel hose. Align the wooden base of the mandrel to the working surface in all planes and then apply vacuum (Figure 3(f)). Once rigid, disconnect the vacuum from the impression and remove the positive sand model (Figure 3(g)).
Modifying the positive sand model Please note that if prior to modifying the model is easily deformed, an additional plastic bag can be applied to the model and sealed to the mandrel to ensure that maximum vacuum is achieved: 1. With the wooden base of the mandrel on a flat surface (Figure 3(h)), evaluate the forefoot/hindfoot alignment. If minor re-alignment is needed, use an awl to puncture a small hole on the dorsal surface of the positive model to reduce the rigidity. Place one hand on the sides of the forefoot and another hand on the sides of the hindfoot and twist in opposite
Downloaded from poi.sagepub.com at Bobst Library, New York University on November 16, 2015
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Prosthetics and Orthotics International
Figure 4. By puncturing a hole into the positive sand model, one can re-align (a) the forefoot/hindfoot relationship or create (b, c) a flat footplate.
Figure 5. To thermoform the foot orthosis, add (a) an air hose under the nylon stocking, place (b) hot thermoplastic or soft material over the model, apply (c) a plastic bag to the model, then tape the bag to (d) the mandrel before applying (e) vacuum suction to form the foot orthosis.
2.
3.
4. 5. 6.
directions until desired alignment is achieved (Figure 4(a)). Tape the punctured hole to solidify the model. To create a flat footplate, puncture a hole on the dorsal surface of the forefoot (Figure 4(b)), apply a downward force over the area you wish to flatten (Figure 4(c)), and then tape the hole to re-seal the model. Measure the ML dimension of the model across the metatarsal heads and compare it to the anatomical measurement. If necessary, increase the dimension by puncturing a hole, manipulating the sand, and re-sealing it. Alternatively, water-based clay can be applied to create pressure reliefs. With the wooden base on the workbench, apply a nylon stocking to the sand model. In a circular motion, use a round rod to blend any irregularities. If intrinsic modifications are needed, such as a metatarsal pad, use a ball peen hammer to make the desired modifications. For large undercuts or anatomy that require pressure reliefs, remove the nylon stocking and apply water-based clay to the model as needed. Since water-based clay has a different specific heat than the sand, rippling may occur when thermoforming plastic. To prevent rippling, beveled Pe-Lite can be used instead. Once build-ups have been added,
apply another plastic bag to the model to cover the build-ups and apply two layers of nylon stocking to prepare the sand model for thermoforming.
Thermoforming the foot orthosis To thermoform the foot orthosis, add an air hose under the nylon stocking on the dorsal surface of the model, place hot thermoplastic or soft material over the model, apply a plastic bag to the model to seal the system, apply vacuum, and tape the outer bag to the mandrel (Figure 5(a) to (e)).
Discussion With repetitive lab testing on plaster models, able-bodied subjects, and pathological subjects, we believe this plasterless dilatancy-based orthosis impression and fabrication technique to be a viable alternative to current methods. Although further independent evaluation is needed, this procedure presents several potential advantages: 1. It requires minimal cost for set up and maintenance since custom equipment described in this technical note are made using supplies that can be purchased at hardware stores.
Downloaded from poi.sagepub.com at Bobst Library, New York University on November 16, 2015
5
Sletto et al. 2. The system is reusable, thereby reducing waste production and long-term cost. 3. The system is clean and fast to learn and use: (a) Do not have to wait for plaster to set or for the carver to carve the model. (b) Modifying the model is a quick and easy process. 4. Being plaster-less, fabrication of foot orthoses is possible even when plaster is not available.
Key points •• The plaster-less system is reusable, thereby minimizing waste and long-term cost. •• This process is potentially faster than traditional methods. Author contribution Larissa (Conner) Sletto wrote the initial draft of the manuscript, edited the manuscript, and took the photos included in the manuscript. Dr Yeongchi Wu assisted with editing and created the illustrations. Chris Robinson reviewed the manuscript and provided feedback.
Declaration of conflicting interests The authors declare that there is no conflict of interest.
Funding The procedure described above was developed and tested at Northwestern University Prosthetics-Orthotics Center in
Chicago, IL, and was funded by the National Institute on Disability and Rehabilitation Research (H133G110266). The opinions contained in this publication are those of the authors of this manuscript and do not necessarily reflect those of the Federal Government or Department of Education or Northwestern University administration.
References 1. Mead W. Method for making and maintaining an impression of the shape of objects. Patent 2472754, USA, 1949. 2. Wu Y, Casanova H, Smith W, et al. CIR sand casting system for trans-tibial socket. Prosthet Orthot Int 2003; 27(2): 146–152. 3. Wu Y, Casanova H, Reisinger K, et al. CIR Casting System for making transtibial sockets. Prosthet Orthot Int 2009; 33(1): 1–9. 4. Jensen J, Poetsma P and Thanh N. Sand-casting technique for trans-tibial prostheses. Prosthet Orthot Int 2005; 29(2): 165–175. 5. Thanh N, Poetsma P and Jensen J. Preliminary experiences with the CIR casting system for transtibial prosthetic sockets. Prosthet Orthot Int 2009; 33(2): 130–134. 6. Jivacate T, Buddhibongsa DML, Tipaya B, et al. Twentyone months’ experience with the PF-modified CIR casting system for trans-tibial prostheses. Prosthet Orthot Int 2012; 35(1): 70–75. 7. Robinson C, Wu Y and Michael J. Low-cost dilatancy system for orthotics. Presented at the annual AOPA national assembly, Boston, MA, 6–9 September 2012. 8. Wu Y, Robinson C, Casanova H, et al. Development of a low-cost dilatancy-based casting system for fabrication of AFO. Presented at the ISPO world congress, 2013, Hyderabad, India, 4–7 February 2013.
Downloaded from poi.sagepub.com at Bobst Library, New York University on November 16, 2015
POI0010.1177/0309364615574162Prosthetics and Orthotics InternationalConner et al.
INTERNATIONAL SOCIETY FOR PROSTHETICS AND ORTHOTICS
Technical Note
Dilatancy-based impression and fabrication technique for custom foot orthoses
Prosthetics and Orthotics International 1–5 © The International Society for Prosthetics and Orthotics 2015 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0309364615574162 poi.sagepub.com
Larissa A Sletto, Yeongchi Wu and Christopher Robinson
Abstract Background and aim: Current methods used to take impressions for custom foot orthoses include plaster bandage, foam box, fiberglass, and laser-optical scanner. Impressions are converted to positive plaster or foam models. These methods create waste and may not be feasible in resource-limited areas. This technical note presents an alternative, greener impression and fabrication technique for foot orthoses that utilizes the dilatancy principle. Technique: Steps of the dilatancy (vacuum-based) procedure include taking an impression of the foot, converting the negative mold to a positive sand model, modifying the positive sand model, and thermoforming the foot orthosis. Discussion: This plaster-less system is inexpensive to set up and maintain, is reusable thereby minimizing cost and waste, and is clean to use. It enables a practitioner to quickly take an impression for fabricating a foot orthosis in a short period of time during a single clinic visit by the patient. Clinical relevance The dilatancy casting system could potentially be a cheaper, faster, and greener alternative procedure for fabricating custom foot orthoses in both developing and developed countries. Keywords Foot, orthosis, custom, impression, modification, fabrication, dilatancy, vacuum-based Date received: 21 June 2014; accepted: 22 January 2015
Background and aim Currently, there are four methods commonly used by practitioners to take impressions for custom foot orthoses: plaster bandage, foam box, fiberglass, and laser-optical scanner. Impressions are then converted to positive plaster or foam models. All of these methods create waste and may not be feasible in resource-limited areas. A new impression and fabrication technique utilizing the dilatancy principle, initially investigated by Mead,1 has been developed,2,3 field tested,4,5 and adapted for transtibial prostheses.6 In a continued attempt to reduce waste created and dependency on costly equipment, we adapted this plaster-less, dilatancy prosthetic technique for fabrication of custom foot orthoses.7,8 This technical note describes this adapted procedure.
reservoir tank, the equipment needed is listed below. Please note that exact dimensions are not critical. Materials needed to create the equipment can be purchased at hardware stores.
Technique
Northwestern University Prosthetics-Orthotics Center, Chicago, IL, USA
Set-up In addition to a heating oven, a vacuum pump with a negative pressure of −25 to −27 inHg, and a minimum 30 gallon
1. Casting bag. The bag (Figure 1(a)) is approximately 36 × 50 cm2, is made of elastic fabric, is filled approximately 70% volume-wise with micropolystyrene beads, has a connector for vacuum, and has a capped opening for filling with polystyrene beads. 2. Casting frame. The u-shaped frame (Figure 1(b)), slightly shorter than the casting bag, comprises a plywood base with length-wise wooden side bars.
Corresponding author: Larissa A Sletto, Northwestern University Prosthetics-Orthotics Center, 680 N Lake Shore Dr, Chicago, IL 60611, USA. Email: [email protected]
Downloaded from poi.sagepub.com at Bobst Library, New York University on November 16, 2015
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Prosthetics and Orthotics International
Figure 1. (a) The casting bag is placed over (b) the casting frame to take (c) an impression.
Figure 2. The design of manifold (left) and vacuum mandrel (right) include connectors to (a) vacuum pump and (b) casting bag and thermoforming set up with (c) bleeders, (d) air flow valves, (e) glass-bottle air filter, (f) felt-covered ends to filter sand, and (g) formed positive sand model.
3. Plastic bags. Bags approximately 45 × 75 cm2 and 0.50–1.00 mm thick are used as air-tight, flexible containers throughout the process. 4. Vacuum control manifold. Comprising steel pipes, this manifold (Figure 2, left) connects the vacuum source to the casting bag and the positive sand model. Ball-type valves are used to control vacuum air flow. The air filter prevents sand from entering the vacuum pump. 5. Air hoses. Four flexible rubber tubes run from the manifold to the vacuum source, to the casting bag (impression), to the vacuum mandrel (positive sand model), and outside the positive sand model (vacuum forming). Tubes should be thick enough that they do not collapse under vacuum. 6. Vacuum mandrel. Used to vacuum form the positive sand model, this mandrel (Figure 2, right) comprises steel pipes, an air hose connector, felt filters, and a wooden base. The felt filter on the
7.
8. 9. 10.
vacuum mandrel can be replaced whenever dust accumulation is noticed in order to prevent dust from reaching the filter on the vacuum control manifold or entering the air filter on the vacuum pump. If this is done on an as-needed basis, manifold filter replacement should rarely be needed. Vacuum mandrel hose. A non-collapsible, flexible air hose with a quick disconnect female adapter on one end and a male adapter on the other is used to connect the mandrel to the manifold. Nylon socks. Low elasticity socks are used for the negative to positive model conversion process and for vacuum forming. Sand. Clean, dust-free (20 grit) sand is ideal for creating a smooth positive model. Local sand can be utilized if cleaned and sifted. General supplies. Electrical tape, scissors, a hammer, an awl, Pe-Lite, Plastazote, and a round rod will be utilized.
Downloaded from poi.sagepub.com at Bobst Library, New York University on November 16, 2015
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Sletto et al.
Figure 3. Steps of (a–c) taking an impression and (d–g) converting to a (h) positive sand model.
Taking an impression (negative mold) 1. Place the casting bag in a new plastic bag and use electrical tape to seal the plastic bag to the air hose (Figure 1(a)). 2. With the patient seated and the foot covered with a nylon stocking, take a coronal diameter (ML) measurement at the metatarsal heads. 3. Place the casting bag on top of the casting frame (Figure 1(b)). Push casting bag beads to the sides and ends and drape the bag over the anterior and posterior ends of the casting frame. The frame limits length-wise shortening of the casting bag when vacuum is applied. 4. With the patient seated, have the patient place their foot on the casting bag and shift the foot anteriorly and posteriorly until the foot is flat on the baseboard of the frame. Check alignment of the talocrural and subtalar joints in both the coronal and sagittal planes and adjust the patient’s lower limb accordingly. 5. Apply partial vacuum by partially opening the vacuum control valve and opening the bleeder valve so that the casting bag can be molded to cover just above the intended trim lines. While under partial vacuum, push beads away from the patient’s toes to create an extended footplate for a full-length custom foot orthosis. In addition, push beads slightly away from the sides of the first and fifth metatarsal heads to create pressure reliefs. 6. While holding the casting bag over the ends of the casting frame, apply full vacuum to solidify the bag. Make the patient to stand in the mold to check for total contact and comfort (Figure 3(b)). Remove the patient’s foot and inspect the impression (Figures 1(c) and 3(c)). If necessary, repeat the impression process.
Converting to positive sand model 1. Place a new plastic bag in the impression (Figure 3(d)) with the seam of the bag “outside of the trim lines.” 2. Pour approximately two cups of sand into a nylon stocking and place the stocking in the plastic bag that was placed in the impression. Add enough sand into the nylon stocking to fill the negative mold and pack the sand down (Figure 3(d)), particularly in the heel so that the heel is fully captured. Next, with the mandrel positioned such that the valve is posterior, push the vacuum mandrel into the sand close to the heel. Without tension on the plastic bag, tape and seal the bag to the mandrel with electrical tape (Figure 3(e)). 3. Connect the mandrel to the manifold using the vacuum mandrel hose. Align the wooden base of the mandrel to the working surface in all planes and then apply vacuum (Figure 3(f)). Once rigid, disconnect the vacuum from the impression and remove the positive sand model (Figure 3(g)).
Modifying the positive sand model Please note that if prior to modifying the model is easily deformed, an additional plastic bag can be applied to the model and sealed to the mandrel to ensure that maximum vacuum is achieved: 1. With the wooden base of the mandrel on a flat surface (Figure 3(h)), evaluate the forefoot/hindfoot alignment. If minor re-alignment is needed, use an awl to puncture a small hole on the dorsal surface of the positive model to reduce the rigidity. Place one hand on the sides of the forefoot and another hand on the sides of the hindfoot and twist in opposite
Downloaded from poi.sagepub.com at Bobst Library, New York University on November 16, 2015
4
Prosthetics and Orthotics International
Figure 4. By puncturing a hole into the positive sand model, one can re-align (a) the forefoot/hindfoot relationship or create (b, c) a flat footplate.
Figure 5. To thermoform the foot orthosis, add (a) an air hose under the nylon stocking, place (b) hot thermoplastic or soft material over the model, apply (c) a plastic bag to the model, then tape the bag to (d) the mandrel before applying (e) vacuum suction to form the foot orthosis.
2.
3.
4. 5. 6.
directions until desired alignment is achieved (Figure 4(a)). Tape the punctured hole to solidify the model. To create a flat footplate, puncture a hole on the dorsal surface of the forefoot (Figure 4(b)), apply a downward force over the area you wish to flatten (Figure 4(c)), and then tape the hole to re-seal the model. Measure the ML dimension of the model across the metatarsal heads and compare it to the anatomical measurement. If necessary, increase the dimension by puncturing a hole, manipulating the sand, and re-sealing it. Alternatively, water-based clay can be applied to create pressure reliefs. With the wooden base on the workbench, apply a nylon stocking to the sand model. In a circular motion, use a round rod to blend any irregularities. If intrinsic modifications are needed, such as a metatarsal pad, use a ball peen hammer to make the desired modifications. For large undercuts or anatomy that require pressure reliefs, remove the nylon stocking and apply water-based clay to the model as needed. Since water-based clay has a different specific heat than the sand, rippling may occur when thermoforming plastic. To prevent rippling, beveled Pe-Lite can be used instead. Once build-ups have been added,
apply another plastic bag to the model to cover the build-ups and apply two layers of nylon stocking to prepare the sand model for thermoforming.
Thermoforming the foot orthosis To thermoform the foot orthosis, add an air hose under the nylon stocking on the dorsal surface of the model, place hot thermoplastic or soft material over the model, apply a plastic bag to the model to seal the system, apply vacuum, and tape the outer bag to the mandrel (Figure 5(a) to (e)).
Discussion With repetitive lab testing on plaster models, able-bodied subjects, and pathological subjects, we believe this plasterless dilatancy-based orthosis impression and fabrication technique to be a viable alternative to current methods. Although further independent evaluation is needed, this procedure presents several potential advantages: 1. It requires minimal cost for set up and maintenance since custom equipment described in this technical note are made using supplies that can be purchased at hardware stores.
Downloaded from poi.sagepub.com at Bobst Library, New York University on November 16, 2015
5
Sletto et al. 2. The system is reusable, thereby reducing waste production and long-term cost. 3. The system is clean and fast to learn and use: (a) Do not have to wait for plaster to set or for the carver to carve the model. (b) Modifying the model is a quick and easy process. 4. Being plaster-less, fabrication of foot orthoses is possible even when plaster is not available.
Key points •• The plaster-less system is reusable, thereby minimizing waste and long-term cost. •• This process is potentially faster than traditional methods. Author contribution Larissa (Conner) Sletto wrote the initial draft of the manuscript, edited the manuscript, and took the photos included in the manuscript. Dr Yeongchi Wu assisted with editing and created the illustrations. Chris Robinson reviewed the manuscript and provided feedback.
Declaration of conflicting interests The authors declare that there is no conflict of interest.
Funding The procedure described above was developed and tested at Northwestern University Prosthetics-Orthotics Center in
Chicago, IL, and was funded by the National Institute on Disability and Rehabilitation Research (H133G110266). The opinions contained in this publication are those of the authors of this manuscript and do not necessarily reflect those of the Federal Government or Department of Education or Northwestern University administration.
References 1. Mead W. Method for making and maintaining an impression of the shape of objects. Patent 2472754, USA, 1949. 2. Wu Y, Casanova H, Smith W, et al. CIR sand casting system for trans-tibial socket. Prosthet Orthot Int 2003; 27(2): 146–152. 3. Wu Y, Casanova H, Reisinger K, et al. CIR Casting System for making transtibial sockets. Prosthet Orthot Int 2009; 33(1): 1–9. 4. Jensen J, Poetsma P and Thanh N. Sand-casting technique for trans-tibial prostheses. Prosthet Orthot Int 2005; 29(2): 165–175. 5. Thanh N, Poetsma P and Jensen J. Preliminary experiences with the CIR casting system for transtibial prosthetic sockets. Prosthet Orthot Int 2009; 33(2): 130–134. 6. Jivacate T, Buddhibongsa DML, Tipaya B, et al. Twentyone months’ experience with the PF-modified CIR casting system for trans-tibial prostheses. Prosthet Orthot Int 2012; 35(1): 70–75. 7. Robinson C, Wu Y and Michael J. Low-cost dilatancy system for orthotics. Presented at the annual AOPA national assembly, Boston, MA, 6–9 September 2012. 8. Wu Y, Robinson C, Casanova H, et al. Development of a low-cost dilatancy-based casting system for fabrication of AFO. Presented at the ISPO world congress, 2013, Hyderabad, India, 4–7 February 2013.
Downloaded from poi.sagepub.com at Bobst Library, New York University on November 16, 2015
