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Design of a Rotational Stability Measurement Device For Analysis of ACL Reconstruction

University of Pittsburgh Senior Design – BioE 1160/1161. Design of a Rotational Stability Measurement Device For Analysis of ACL Reconstruction. Stephanie Bechtold Katie Dillon Kara Wagner Mentor: Thore Zantop, M.D. April 18, 2005. Goal.

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Design of a Rotational Stability Measurement Device For Analysis of ACL Reconstruction

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  1. University of Pittsburgh Senior Design – BioE 1160/1161 Design of a Rotational Stability Measurement DeviceFor Analysis of ACL Reconstruction Stephanie BechtoldKatie Dillon Kara Wagner Mentor: Thore Zantop, M.D. April 18, 2005

  2. Goal To develop and test a novel device to measure the rotational stability of the knee after an Anterior Cruciate Ligament (ACL) reconstruction

  3. ACL anatomy • Two distinct fiber bundles • Anteromedial (AM) • Translational stability • Posterolateral (PL) • Rotational stability www.aclsolutions.com/ images

  4. Current Reconstruction Methods • Single bundle • Restore only the AM bundle • Susceptible to reinjuries by pivoting • Double bundle • Restores both AM and PL bundles • More anatomically correct

  5. Devices to Evaluate ACL Reconstruction • Current devices only measure translational stability of the knee • Double bundle technique creates need for device to measure rotational stability • Evaluate effectiveness of PL bundle reconstruction http://www.medmetric.com/kt1.htm http://www.aircast.com

  6. Problem Statement • A device is needed to measure the rotational stability of the knee • Comprehensive analysis of reconstruction techniques • An immobilization device is needed to comfortably restrict movement in the hip and ankle joints • Ensure pure rotation of the knee is measured

  7. Market Considerations • Market size • 16,000 Orthopedic Surgeons (AAOS) • Predicate Devices • KT1000: $3900 • Rolimeter: $850

  8. Initial Design Considerations • Adjust boot to keep ankle immobile • Fix knee at various flexion angles (0, 30, 45, 60, 90 degrees) • Comfortably immobilize hip • Consistently and safely apply known moment • Collect repeatable data

  9. Prototype Development- Boot • Aircast® Pneumatic Walker Brace • Nest of BirdsAscension Technology Corporation, Burlington, VT/USA • Universal force-moment sensor(JR3, Woodland, California) Photos courtesy of Ferguson Lab

  10. Initial Design Considerations • Adjust boot to keep ankle immobile • Fix knee at various flexion angles (0, 30, 45, 60, 90 degrees) • Comfortably immobilize hip • Consistently apply known moment • Collect repeatable data

  11. Prototype Development- Hip Brace • Lateral Decubitus position • Wheelchair leg rest

  12. Initial Design Considerations • Adjust boot to keep ankle immobile • Fix knee at various flexion angles (0, 30, 45, 60, 90 degrees) • Comfortably immobilize hip • Consistently and safely apply known moment • Collect repeatable data

  13. Prototype development • Redesign of initial prototype • Patient placed in supine position • Lower leg horizontal • Adjustable leg rest • Knee flexion angle • Length of femur • Minimize metal components

  14. Prototype Fabrication

  15. Materials Selection • Constructed of acrylic • Eliminates metal components • Minimizes interference with magnetic sensors • Durable • Comfortable for patient

  16. Evaluation of Device • 4 subjects - at 3 flexion angles • 5 trials each • Ensure repeatability • Goal: Range of motion within ±1° • Subject reports stability of ankle and hip joints

  17. Experimental Methods • Subjective knee evaluation performed by a clinician to determine health of knee • Subject fitted with boot and brace to comfort • Nest of Birds (NOB) sensors placed on • Proximal Tibia • Distal Femur • Front of Boot

  18. Experimental Methods • Lower leg leveled at horizontal • Creates neutral start position • Moment applied by clinician (10Nm) • Range of motion recorded by Nest of Birds

  19. Experimental Methods

  20. Sample Results

  21. Preliminary Results • Range of Motion, in degrees • 4 subjects, 5 trials each

  22. Initial Design Considerations • Adjust boot to keep ankle immobile • Fix knee at various flexion angles (0, 30, 45, 60, 90 degrees) • Comfortably immobilize hip • Consistently and safely apply known moment • Collect repeatable data

  23. Discussion • Range of motion was repeatable within ±2° for all subjects • Subjects reported ease of use and comfort of the boot and brace • Overall apparatus is heavy for operator

  24. Competitive Analysis • Predicate Devices • Strengths • Lightweight • Simple design • Weaknesses • Limited analysis of reconstruction techniques Our Device • Strengths • More comprehensive analysis of ACL reconstruction • Weaknesses • Complex design • Higher cost • Race for “first to market” • Competition to develop similar device

  25. Constraints limiting Phase I testing • IRB approval • Create baseline data for normal subjects • Overhead cost of measurement devices

  26. Quality System Considerations • Class I device: non-invasive • Human factors • Biocompatibility • Ease of use for clinician • Patient’s Comfort • Ethical issues • Broad range of normal subjects • Reduce cost

  27. Future • Streamline design • Minimize cost • Lower weight of apparatus • Testing on reconstruction patients • Evaluate effectiveness of technique • Possible combination device based on KT1000 or Rolimeter • To measure both translational and rotational • stability in the same device

  28. Acknowledgements • Kevin Bell M.S. • Volker Musahl M.D. • Ryan Costic M.S. • Larry Herman • Department of Bioengineering • Drs. Hal Wrigley and Linda Baker

  29. IKDC form • Standard, subjective knee evaluation • Patient • History of injury • Symptoms • Activity Level • Clinician • Translational stability evaluated using KT1000 or rolimeter • Subjective evaluation of rotational stability

  30. Background • 100,000 ACL reconstructions per year • 6th most common orthopedic procedure in the US • Debate over best method • Single vs. double bundle • Complex anatomy • AM bundle - translation • PL bundle - rotation Courtesy of Ferguson Lab

  31. Work Breakdown • Kara Wagner • Background research, contact with machine shop • Katie Dillon • Testing • Stephanie Bechtold • Solidworks prototype • Everyone • Design History File, SBIR

  32. Milestones • Initial meeting with mentor – October 2004 • Initial draft of design history file – December 8, 2004 • Initial draft of SBIR – December 17, 2004 • Ordered materials – First week of March 2005 • Completed Solidworks – Third week of March • Prototype Completed – Last week of March • Preliminary testing – First week of April

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