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Bowleggedness Correction Brace

University of Pittsburgh Senior Design – BioE 1160/1161. Bowleggedness Correction Brace. Amy Macevoy Daniel Steed Lauren Wolbert Sarah Wyszomierski April 18, 2006 Mentor: Morey S. Moreland, M.D. Children’s Hospital, UPMC. Background. Redesign of pediatric bowleggedness correction brace

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Bowleggedness Correction Brace

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  1. University of Pittsburgh Senior Design – BioE 1160/1161 Bowleggedness Correction Brace Amy Macevoy Daniel Steed Lauren Wolbert Sarah Wyszomierski April 18, 2006 Mentor: Morey S. Moreland, M.D. Children’s Hospital, UPMC

  2. Background • Redesign of pediatric bowleggedness correction brace • Focus: • Correction and Support for • Blount’s disease (tibia vara) • Bowleggedness (genu varum) • Rickets • Children 2-13 years old • Specifically, 6.5 – 10.5 yrs

  3. Background • In U.S., ~ 277,000 children have severe bowleggedness (Frost & Sullivan) • Improper growth in femur and tibial growth plates • Rickets occurs most often in malnourished children • eg.) In Mongolia, 32.1% of children under 5 (UNICEF) • disorder, usually in children, involving softening and weakening of the bones • caused by lack of vitamin D, calcium, or phosphate

  4. Problem Statement • Current devices are expensive, non-adjustable, custom-molded • Outgrowth: rapid, frequent • Too expensive for low income households (up to $3,500) • Also applicable in 3rd world countries • Project goal: • Redesign pediatric bowleggedness correction brace • Applies forces to correct angle of tibia and femur growth plates • Adjustable • Affordable • Lightweight/Non-bulky

  5. Design Requirements • Material • Inexpensive • Easy to acquire • Durable • Design • Simple to machine and assemble • Plans to orthotists, companies • Parts easily acquired and replaced • Correction • 3 point system • Corrective force at knee • Counteracting forces • for stability

  6. Design, cont’d Adjustable Interchangeable b/w R and L leg Length Circumference S/M/L braces Medium (5th – 95th percentile, 6.5 – 10.5 yrs) Lightweight < 2.3 kg (5 lbs) Affordable < $300 per brace Comfort Reduce occurrence of pressure sores Design Requirements, cont’d

  7. Economic Considerations Significantly lower price • Up to $3,500 vs. ~ $250-300 • Not custom molded • Adjustable Market size • ~$83 million market LSGH (Frost & Sullivan Reports) Distribution • Medical supply companies • Private Orthotists and Rehabilitation Specialists

  8. Initial Design Considerations • Design Problems: • Lack of: • Support and correction at knee • Straps to secure • Foot interface • Wanted sturdier design • Nested tubing • Too heavy • Difficult to acquire • correct dimensions Version 1.0 Version 1.1

  9. Initial Design, cont’d  Proposed Solution • Too many adjustment holes • Difficult to machine Version 2.0 Version 2.1

  10. Design Solution • Correction: • 3 pt system (shown in gold) • Easily machined, common materials: • Aluminum 6061 Alloy • Side holes • Velcro/Neoprene straps • Grommets, elastic • Machine screws/washers/bolts • Lock washers • Optional padding • Washable • Water clog • Breathable • Waterproof • Inexpensive

  11. Prototype Fabrication Insert strap grommets for adjustability Milled/Drilled Beams Drilled Shoes FINAL PRODUCT Trim bolts Insert padding

  12. Experimental Methods Used to Test Device Performance • Human Subject Testing • Comfort • Usability • Strap Corrective Pressure • Materials Testing • COSMOSWorks testing • Deformation • Factor of Safety

  13. Experimental Methods- Human Subject Testing • 1 Human Subject Volunteer • Male, 9 yrs 9 mos • Height: 54” (60th percentile) • Weight: 70.5 lbs (50th percentile) • Subject fitted with brace • Insertion of Pressurex-Micro pressure transducer film to record corrective pressure values • Standing for 10 minutes • Walking for 2 minutes

  14. Experimental Methods- Human Subject Testing • Comfort • Subject answered survey questions, based on a scale of 1 to 5: • How uncomfortable are you feeling? (5 = most discomfort) • How much do you feel the brace is slipping as you walk? (5 = most slipping) • Do you feel that the heaviness of the brace is keeping you from moving normally? (5 = most hindering) • Overall, how comfortable do you feel in the brace? (5 = most comfortable) ** “No discomfort” does not imply “comfort” • Usability • Gait alterations • Slipping of straps

  15. Experimental Methods- Human Subject Testing • Pressure Transducer Film Readings • Analyzed using Matlab program • Converts scanned film .jpg to grayscale • Uses reference image and scaling factor to interpret grayscale values as pressure values within input range • Determined: • Average maximum pressure (highest 10% of values) • Average overall pressure

  16. Comfort & Usability Results • COMFORT:Subject answered survey questions, based on a scale of 1 to 5: • Discomfort = 2 • Slipping = 1 • Heaviness = 1 • Comfort = 3 • USABILITY: • Altered gait pattern • Walked with slight limp • No slipping of straps

  17. Pressure Results Pressure in Corrective Straps (psi) Highest concentration of max values occurred approx. at points of varus/valgus pressures Calf Knee Thigh

  18. Discussion – Human Subject Testing • Comfort • Overall, minimal discomfort, slipping, and hindrance due to heaviness • Sources of Error: • Subject pool size • Use of able-bodied child • Unaccustomed to brace usage • Responses from children may be skewed • Usability • Limp severity may be due to uneven foot height • No slipping • Allows for normal activity

  19. Discussion – Human Subject Testing • Pressure • Mean pressure < Literature skin breakdown values • ~ 15 – 35 psi • Highest values at knee (as compared to calf and thigh) • Angle corrected • Targeted location of max pressure concentrations • Sources of error: • Subject pool size, no specified conditions • Film handling • Reference to grayscale • Uses: • Fitting • Correction progress

  20. Experimental Methods – Materials Testing • COSMOSWorks Testing • Each beam fixed on ends at bolt placement • Pressure applied at corrective force strap interface • ~ Average pressure • ~ 20 psi (max pressure) • Analyzed for • Deformation • Factor of Safety

  21. Materials Testing Results COSMOSWorks Results

  22. Discussion – Materials Testing • Small values for deformation • Determined to be insignificant • Will not affect integrity of brace • High factors of safety • Desirable FOS values are those that are > 1 • FOS > 1 represents how much the stress is within the allowable limit • Value > 1 for average pressures • Value > 1 for maximum pressures

  23. Competitive Analysis Custom-Molded HKAFO (Hip-Knee-Ankle-Foot Orthosis) • DeLaTorre O & P • ~$1,400 KAFO, Metal (Knee-Ankle Foot Orthosis) • DeLaTorre O & P • $795

  24. Strengths Affordability Adjustability Modularity Pieces may be replaced and moved without full brace replacement Weaknesses Not custom molded May hinder comfort, exact fit Competitive Analysis

  25. Constraints limiting Phase I testing Economic • Pressurex-Micro transducer film reader ~$4000 Resources/Regulatory • Human Subject Testing • Need more subjects, with specified conditions • Long-term testing to assess correctiveness • Gait testing with motion capture • Lower body kinematics • Materials Testing • Repetitive motion testing for durability

  26. FDA Regulation TITLE 21--FOOD AND DRUGS CHAPTER I—FOOD AND DRUG ADMINISTRATION DEPARTMENT OF HEALTH AND HUMAN SERVICES PART 890-Physical Medicine Devices • Subpart D--Physical Medicine Prosthetic Devices • Sec. 890.3475 Limb orthosis • (a) Identification. limb orthosis (brace) is a device intended for medical purposes that is worn on the upper or lower extremities to support, to correct, or to prevent deformities or to align body structures for functional improvement. Examples of limb orthoses include the following: A whole limb and joint brace, a hand splint, an elastic stocking, a knee cage, and a corrective shoe. • (b) Classification. Class I (general controls). US Food and Drug Administration: http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm

  27. Regulation • Pre-existing Devices and Patents • Majority: custom molded • wide variety of devices, as well as device components, already existing • some with patents

  28. Manufacturability Simple Design Common components Easy assembly Human factors Anthropometry Collected data for children to determine proper sizes (used 5th-95th percentile data for medium size) Shoe interface Breathable Waterproof Soft material (contours to individual) Optional padding Washable Straps Adjustable Comfortable fit Quality System Considerations

  29. Schedule • January • Improved sketches • Ordered materials • February • Finalized sketch • Ordered pressure sensors • Practiced testing (using pressure sensors) • Completed market analysis • March • Finished acquiring materials • Fabrication • April • Finished design/fabrication improvements • Completed testing • Finalized documentation

  30. Amy Market and Competitive Analysis Background/Statistics Clinical Correspondence Dan Design Market Research Materials/Fabrication Human Subject Recruitment & Testing Mentor Correspondence Lauren Initial Design COSMOSWorks testing Human Factors Analysis Sarah Final Design & Anthropometry Materials/Fabrication Human Subject Testing & Analysis Clinical Correspondence Group Task Breakdown

  31. Future • Design Improvements • Improved locking knee joint • More cost-effective straps • Neoprene sheets ~$30 : Reduce overall price by $80 • Improved shoe interface • Threaded inserts: reduce shearing in shoe sole • Materials testing to find more optimal beam • material/fasteners • Improved system for reading pressure • Formulate instructions for fabrication and use • Sent to companies, orthotists, 3rd world countries, etc.

  32. Acknowledgements • Morey S. Moreland, M.D. • Children’s Hospital of Pittsburgh, UPMC • April J. Chambers • Human Movement and Balance Lab • Gregory R. Frank • Augmented Human Performance Lab • Kevin McNulty • McNulty Landscaping & Handyman Services • Brian Wlahofsky • Human Subject Testing • Beverley Welte • Life Sciences Greenhouse • The generous gifts of: • Dr. Hal Wrigley • Dr. Linda Baker

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