ORTHOPEDIC CHECK SHOES

Transcription

1 A transparent flexible plastic shoe formed over a patient's foot Last. The check shoe can be placed on the patient's foot and,being clear, allows the practitioner to see where modification would be necessary for ideal footwear design. Well-fitting, comfortable, orthopedic footwear can be crucial for people with mild to severe foot/ankle deformities, traumatic injuries, pathophysiological disorders or other mechanical anomalies. Properly fitting and functional orthopedic footwear can be the decisive factor between independent mobility, or forced reliance on crutches or confinement to a wheelchair. Transparent, flexible plastic "check shoes" can be an invaluable diagnostic and assessment tool, helping practioners achieve the best possible footwear design for their patients. Check shoes permit assessment of the degree of fit afforded by a given Last design. They enable visualization of the distribution and magnitude of pedal loading as revealed in pedal tissue blanching and blushing; as well as the amount of clearance afforded between the shoe and the foot in stress intolerant areas. If the check shoe fitting reveals modification of a given Last design is necessary, the locations and magnitudes of the changes required can be traced directly on the check shoe, and subsequently incorporated in the Last design, either in a Pedorthic CAD/CAM System or through conventional manual methods. New check shoes can then be fabricated over the resulting modified Lasts, and the process of check shoe fittings, in situ evaluation and Last design refinement, repeated until a well-fitting, functional, comfortable Last design is achieved. To produce check shoes that can support a patient's weight, without deforming more than definitiveorthopedic shoes do, and which have dorsa and sides with mechanical stiffnesses similar to those of orthopedic shoe upper (so donning and doffing is easily accomplishedwithout risk of pinching, scratching or abraiding patient's pedal tissues), a flexible elastic thermoplastic such as Duraflex should be used. A check shoe is fabricated by thermoforming a sheet of Duraflex over a positive model of a Last. Before thermoforming, the Last should be inverted so its plantar surface is upward. This enables the sole of the check shoe to be kept relatively thick during the thermoforming process, while the dorsum and sides of the check shoe are stretched thinner to achieve a flexibility and stiffness similar to that of definitive shoe uppers. As the plastic is drape molded around the Last, it is pinched together along the dorsal midline to give a separable seam extending from the ankle to the toes. This provides an opening that permits easy ingress and egress of the patient's foot during fitting, after the check shoe is trimmed and finished. If custom insoles are prescribed together with custom orthopedic shoes for a patient, the insoles can be designed and manufactured, Page 2

2 How to form a check shoe? (cont.) the model should be slightly dampened to prevent breakage when the lag bolt is screwed into the plaster, and when the plastic is pulled down over the model.) When the base board, support board, and Last are screwed together, they should form a solid unit ready for thermoforming. It is recommend that a 16" long x 16" wide x 1/2" thick sheet of Duraflex plastic be used to thermoform check shoes for adults. 3/8" thick Duraflex can be used for children and small adults. The plastic is placed between two 16" x 16" x 1/4" aluminum clamping frames that have a 13" diameter hole in the center. These frames fit over a thermoforming pedestal with a 12-1/4" round aluminum platen and vacuum attachment. A round vacuum platen and thermoforming frame are used to prevent creases from forming as the plastic is pulled over the Last. The plastic should be heated to glass temperature (approximately 115ºC/240ºF) on a rack in a convection oven. It should be heated until it droops down about half the height of the Last. If thermoforming is performed in a cool/cold room (especially if a plaster Last is used), it is recommended that the (plaster) Last be preheated in the oven for approximately five minutes to avoid local concentration of stresses, with accompanying surface hardening, shrinkage and/or warping of the thermoformed plastic from contact with the cold cast. When the plastic reaches glass temperature and begins to sag, it is ready to thermoform and should be removed from the oven while clamped in the frame, and quickly inverted so it forms a dome over the Last - support fixture - vacuum pedestal. The plastic should then be slowly lowered over the Last. The orthotist/pedorthist/technician can use his/her hands to ensure the plastic stretches along the sides of the Last, and not from the top. The plastic must remain relatively thick over the plantar surface of the Last, so the check shoe will properly support the patient s weight without excessively deforming. The orthotist/pedorthist/technician should guide the plastic in around the Last, pinching Page 3

3 it together along the forefoot dorsal surface center line. Only one seam should be allowed to form. As this is done, the vacuum should be applied. Care should be taken to prevent creases from forming at the toes and at the heel, as the vacuum is applied and the plastic pulls in around the Last. The orthotist/pedorthist/technician should continue to pull the plastic down over the Last and support fixture, until it locks over the platen on the vacuum pedestal creating a seal. After checking to ensure the plastic is pulled in tightly all around the Last, the molding process is complete. The vacuum should be kept on as the plastic cools, to ensure it continues to tightly encase the Last without any gapping. After approximately 20 minutes, when the plastic has cooled to room temperature, the vacuum can be turned off and the plastic can be trimmed from around the vacuum pedestal and the support fixture. The plastic should be left intact on the Last, however, and let stand for at least 24 hours to allow balance of the internal stresses induced during thermoforming, that otherwise would cause shrinkage and distortion of the check shoe if trimmed and removed from the Last too soon. When the plastic has set sufficiently so the stresses have balanced, the check shoe can be trimmed along the forefoot seam, and the Last removed. The inside of the check shoe should then be cleaned, and the edges trimmed to the appropriate contours, and smoothed so they will not scrape, abraid, or otherwise impinge on the patient s pedal tissues. The check shoe is then ready to try on the patient and assess the degree of conformity and fit between the Last/check shoe geometry and that of the patient s foot and ankle. In difficult cases with significant pedal deformity, or scarring from traumatic injuries, or pathophysiological conditions such as Charcot ankle, osteoarthritic joints, talpies equinovarus, etc. check shoes are invaluable tools for evaluation of footwear fit and derivation of optimum designs. If modivication is needed, use a heat gun at a low temperature. Be careful not to distort the check shoe by getting too close with the heat gun. Page 4

4 ORTHOPEDIC CHECK SHOES Vern L. Houston, PhD, CPO and Kenneth P. LaBlanc, BS, CPO VA New York Harbor HealthCare System / New York University School of Medicine Introduction Well-fitting, comfortable, orthopedic footwear can be crucial for people with mild to severe foot/ankle deformities, traumatic injuries, pathophysiological disorders, or other biomechanical anomalies, Figure 1. Properly fitting and functional orthopedic footwear can be the decisive factor between independent mobility, or forced reliance on crutches, or confinement to a wheelchair. Figure 1. Examples of pedorthics patients feet that require precision design and fitting of custom orthopedic footwear. Transparent, flexible plastic, check shoes, Figure 2, can be an invaluable diagnostic and assessment tool, helping pedorthists/orthotists achieve the best possible footwear design for their patients. Check shoes permit assessment of the degree of fit afforded by a given Last design. They enable visualization of the distribution and magnitude of pedal loading, as revealed in pedal tissue blanching and blushing; as well as the amount of clearance afforded between the shoe and the foot in stress intolerant regions. If check shoe fitting reveals modification of a given Last design is necessary, the locations and magnitudes of the changes required can be traced directly on the check shoe, and subsequently incorporated in the Last design, either in a Pedorthic CAD/CAM System or through conventional manual methods. New check shoes can then be fabricated over the resulting 5 GUARD INDUSTRIES

5 Figure 2. Evaluation of orthopedic Last design and resulting load distribution with transparent, flexible plastic check shoes. modified Lasts, and the process of check shoe fitting, in situ evaluation, and Last design refinement, repeated until a well-fitting, functional, comfortable Last design is achieved. Check Shoe Fabrication To produce check shoes that can support a patient s weight, without deforming more than definitive orthopedic shoes do, and which have dorsa and sides with mechanical stiffnesses similar to those of orthopedic shoe uppers (so donning and doffing is easily accomplished without risk of pinching, scratching, or abrading patients pedal tissues), a flexible, elastic thermoplastic, such as Duraflex, should be used. A check shoe is fabricated by thermoforming a sheet of Duraflex over a positive model of a Last. Before thermoforming, the Last should be inverted so its plantar surface is upward. This enables the sole of the check shoe to be kept relatively thick during the thermoforming process, while the dorsum and sides of the check shoe are stretched thinner to achieve a flexibility and stiffness similar to that of definitive shoe uppers. As the plastic is drape molded around the Last, it is pinched together along the dorsal midline to give a separable seam extending from the ankle to the toes. This provides an opening that permits easy ingress and egress of the patient s foot during fitting, after the check shoe is trimmed and finished. If custom insoles are prescribed together with custom orthopedic shoes for a patient, the insoles can be designed and manufactured, and placed on the respective Lasts for inclusion in the check shoes during thermoforming, Figure 3. This enables evaluation of the fit and function of the complete orthopedic footwear shoe insole complex. Figure 3. Check Shoe with custom contoured orthopedic insole. To hold the Last in an inverted, upright position for thermoforming, so it will be completely encompassed by plastic, a support fixture is required. An example of a simple support fixture is shown in Figure 4, which consists of a base board, a support board, and an attachment bolt. The base board is 24 cm long x 11 cm wide x 2 cm thick, with a 1.4 cm diameter hole drilled 5.5 cm from one of the ends and the two sides. Four 5 cm x 5 cm x 2.5 cm wooden feet are added at the ends of the base board to allow air to be evacuated around and under the Last and base board during thermoforming. The support board is 12 cm x 5 cm x 1.5 cm. A 1.4 cm diameter hole is drilled through the support board along its center line, 5 cm from one of its ends. The support 6 GUARD INDUSTRIES

6 board provides additional support for Lasts whose proximal talar sections extend beyond the base board. A 7.5 cm long, 1.3 cm diameter lag bolt is used to attach the Last to the base and support boards. If an attachment hole is not already present in the top of the Last, one should be Base Board Support Board Lag Attachment Bolt Figure 4. Last support fixture consisting of: base board, support board and lag bolt. drilled on the longitudinal center line, approximately 3.5 cm behind the anterior border of the proximal talar surface. (If a plaster of paris Last model is used for thermoforming, the model should be slightly dampened to prevent breakage when the lag bolt is screwed into the plaster, and when the plastic is pulled down over the model.) When the base board, support board, and Last are screwed together, they should form a solid unit ready for thermoforming, Figure 5. Plaster Last Model Lag Bolt Base Board Figure 5. Last aligned and secured to support fixture in preparation for thermoforming. It is recommended that a 40 cm long x 40 cm wide x 12 mm thick sheet of Duraflex plastic be used to thermoform check shoes for adults. 9 mm thick Duraflex can be used for children and small adults. The plastic is placed between two 40 cm x 40 cm x 6 mm aluminum clamping frames, that have a 33 cm diameter hole in the center. These frames fit over a thermoforming 7 GUARD INDUSTRIES

7 pedestal with a 31 cm round aluminum platen and vacuum attachment, Figure 6. A round vacuum platen and thermoforming frame are used to prevent creases from forming as the plastic is pulled over the Last. The plastic should be heated to glass temperature (approximately 115 C) on a rack in a convection oven. It should be heated until it droops down about half the height of the Last. If thermoforming is performed in a cool/cold room (especially if a plaster Last is used), it is recommended that the (plaster) Last be pre-heated in the oven for approximately five minutes to avoid local concentration of stresses, with concomitant surface hardening, shrinkage and/or warping of the thermoformed plastic from contact with the cold cast. Figure 6. Last on support fixture and vacuum pedestal, with Duraflex plastic clamped in frame ready for insertion into oven for heating and thermoforming. When the plastic reaches glass temperature and begins to sag, it is ready to thermoform, and should be removed from the oven while clamped in the frame, and quickly inverted, so it forms a dome over the Last support fixture vacuum pedestal, Figure 7. The plastic should then be slowly lowered over the Last. The orthotist/pedorthist can use his/her hands to ensure the plastic stretches along the sides of the Last, and not from the top. The plastic must remain relatively thick over the plantar surface of the Last, so the check shoe will properly support the patient s weight without excessively deforming. The orthotist/pedorthist should guide the plastic in around the Last, pinching it together along the forefoot dorsal surface center line. Only one seam should be allowed to form. As this is done, the vacuum should be applied. Care should be taken to prevent creases from forming at the toes and at the heel, as the vacuum is applied and the plastic pulls in around the Last. The orthotist/pedorthist should continue to pull the plastic down over the Last and support fixture, until it locks over the platen on the vacuum pedestal creating a seal. After checking to ensure the plastic is pulled in tightly all around the Last, the molding process is complete. The vacuum should be kept on as the plastic cools, to ensure it continues to tightly encase the Last without any gapping. After approximately 20 minutes, when the plastic has cooled 8 GUARD INDUSTRIES

8 Figure 7. Duraflex plastic heated to glass temperature, inverted, ready to pull down over the Last and support fixture, thermoforming a check shoe. to room temperature, the vacuum can be turned off and the plastic can be trimmed from around the vacuum pedestal and the support fixture. The plastic should be left intact on the Last, however, and let stand for at least 24 hours to allow equilibration of the internal stresses induced during thermoforming, that otherwise would cause shrinkage and distortion of the check shoe if trimmed and removed from the Last too soon. When the plastic has set sufficiently so the stresses have equilibrated, the check shoe can be trimmed along the forefoot seam, and the Last removed. The inside of the check shoe should then be cleaned, and the edges trimmed to the appropriate contours, and smoothed so they will not scrape, abraid, or otherwise impinge on the patient s pedal tissues. The check shoe is then ready to try on the patient and assess the degree of conformity and fit between the Last/check shoe geometry and that of the patient s foot and ankle, Figure 8. In difficult cases with significant pedal deformity, or scarring from traumatic injuries, or pathophysiological conditions such as Charcot ankle, osteoarthritic joints, talpies equinovarus, etc. check shoes are invaluable tools for evaluation of footwear fit and derivation of optimum designs. Figure 8. Check shoe and pedal cast of pedorthic patient with Charcot ankle and osteoarthritic deformity of the hallux. 9 GUARD INDUSTRIES