Development of Subischial Prosthetic Sockets with Vacuum-Assisted Suspension for Highly Active Persons with Transfemoral Amputations

Principal Investigator: Stefania Fatone, PhD, BPO(Hons)

Co-Investigators: Ryan Caldwell, CP**; Matthew Major, PhD; Steven A. Gard, PhD; Wei Chen, PhD*; Cheng Sun, PhD*

Consultants: Andrew Hansen, PhD; Brian Ruhe, PhD; R. J. Garrick, PhD

Post-doctoral Fellow: Oluseeni Komolafe, PhD

Research Assistants/Graduate Students: Brian Robillard, MS; Kevin Yngve, MS; Regan Radcliffe, MS; Sean Wood, MS; Kerice Tucker, BS; William Brett Johnson, PhD; Lilly Tran, MS

Clinical Faculty: Michael Cavanaugh, CPO; Christopher Robinson, MS, MBA, CPO; John Michael, CPO; John Brinkmann, CPO

Collaborators: Jason Wilken, PhD; John Fergason, CPO; Elizabeth Russell-Esposito, PhD; Andrea Ikeda, CP, Center for the Intrepid, Brooke Army Medical Center, San Antonio, TX

*Department of Mechanical Engineering, Northwestern University; **Visiting Scholar, Northwestern University and Prosthetist, Scheck & Siress Prosthetics, Orthotics & Pedorthics

Funded by: Department of Defense #W81XWH-10-0744

Status: In Progress

Introduction

Transfemoral (above-the-knee) amputation results in the loss of two major lower-limb joints: the ankle and knee. Loss of active knee control is one factor that makes mobility extremely challenging for persons with transfemoral amputation. Current transfemoral prosthetic socket designs encase the hip joint and portions of the pelvis, limiting range of motion at the hip and compromising comfort. While current prosthetic sockets are reasonably functional for persons with amputation levels below the knee and for those persons with low to moderate levels of function, they provide limited functional restoration for those with higher levels of amputation, especially highly active individuals.

Service persons with amputation present challenges that are different from the more typical older amputee with vascular problems. Individuals who enter the military are generally young and in excellent health prior to their combat-related injury. Many wounded soldiers wish to return to the level of activity they enjoyed before their injuries, including active duty. Therefore, they have much higher expectations of their function after amputation. Given the resources and time invested in training our military personnel and the substantial negative functional impact of a transfemoral amputation, providing these highly skilled, dedicated and motivated individuals with the rehabilitation and prosthetic technology necessary to return to an active and fulfilling life-style, including continued service is a desirable goal and worthwhile investment of resources.

Examples of transfemoral sockets: (a) Ischial Containment and (b) Sub-ischial

To address these issues, a teachable subischial socket technique, the Northwestern University Flexible Sub-Ischial Vacuum (NU-FlexSIV) Socket that aims to improve comfort without compromising function, was developed.

Outcomes of the Project

The Northwestern University Flexible Sub-Ischial Vacuum (NU-FlexSIV) Socket has lower proximal trim lines that do not impinge on the pelvis; is flexible so muscles can move comfortably within the socket as they contract during activity and improve sitting comfort; and is held securely to the residual limb by vacuum pump suction as well as compression of an undersized liner and socket. The socket includes a highly compressive, cylindrical fabric covered silicone liner, a flexible inner socket, and a shorter rigid outer socket with vacuum applied between liner and inner socket. An algorithm and rectification mapping were developed to facilitate decision making for socket fabrication. Socket comfort score, gait analysis, and clinical outcome measures (Rapid-Sit-To-Stand, Four-Square-Step-Test and T-Test of Agility) were used to assess socket performance. A hands-on workshop to teach this technique was piloted.

The undersized liner and socket are used to compress the residual limb, stiffening the soft tissue and decreasing relative motion of the limb within the socket. The impression is taken over the liner with the patient seated and the limb flexed and slightly abducted, allowing gravity to pre-modify the tissues. Rectifications were quantified using a program that aligned a series of 30 scans of rectified and unrectified negative molds and calculated changes in shape. A color coded scale on the rectification map indicates the depth and contours of the rectifications required for the NU-FlexSIV Socket, showing that plaster is primarily removed from the proximal-lateral and posterior regions, while the medial and anterior regions remain relatively untouched. No plaster is added. For 2 subjects, socket comfort increased in the NU-FlexSIV Socket compared to an ischial containment socket. Walking speed increased for the NU-FlexSIV Socket but other gait variables, including coronal plane trunk flexion and sagittal hip motion, were comparable for level ground walking. Clinical outcome measure performance was comparable in both sockets. Three workshops held in summer 2015 were attended by 31 prosthetists from the US and Canada. Attendees were taught to cast, rectify, fit and align the NU-FlexSIV Socket. Patient models responded positively to the comfort, range of motion and stability of the NU-FlexSIV Socket while prosthetists described the technique as “straight forward, reproducible”.

To the best of our knowledge, this is the first attempt to create a teachable subischial socket technique that results in improved comfort and comparable function to ischial containment sockets. Color coded rectification maps help communicate an important step in this socket technique, enhancing dissemination. Socket stability during walking was confirmed by lack of lateral trunk flexion and lateral socket gapping at mid stance. Clinical experience fitting this socket to nearly 100 patients confirms these research findings. Initial evaluation of the NU-FlexSIV Socket with military amputees is promising. Future work includes an assessor-blinded, randomized cross-over trial comparing comfort and functional performance with the NU-FlexSIV Socket to the ischial containment socket in persons with unilateral transfemoral amputation.

Supplemental Funding

Supplemental funding was awarded through the Joint Warfighter Medical Research Program (JWMRP), to augment and accelerate high priority Department of Defense initiatives that are close to achieving their objectives and yielding a benefit to military medicine. Vacuum-assisted suspension uses an active pump to create a negative pressure differential between the interior of a prosthetic socket and the surface of a residual limb.

Figure 1 (a) NU-FlexSIV Socket, (b) and (c) range of motion; (d) single limb stance stability; (e) rectification map.
Figure 1 (a) NU-FlexSIV Socket, (b) and (c) range of motion; (d) single limb stance stability; (e) rectification map.

Within the scope of our original project, we developed plans and submitted patent applications for a hybrid, integrated electric/mechanical pump system. We fabricated prototypes and tested these hybrid vacuum pumps to demonstrate that they create suitable vacuum for suspension of the prosthesis in persons with transfemoral amputation.  

Acknowledgements

NUPOC would like to acknowledge the support of Össur in providing knees and feet for use in the NU-FlexSIV Socket Courses held in 2016; and the support of Össur and Medi in donating liners for patient models who participated in the NU-FlexSIV Socket Courses held in Summer 2015.

Patents

Caldwell R, Hansen A, Wood S, Chen W, Radcliffe R, Yngve K, Kuhar B, Nelson AJ, Nickel E. Vacuum Pump Systems for Prosthetic Limbs and Methods of Using the Same. United States Patent 9,066,822. Issued on June 30, 2015. 

Related Publications

Gissal J (2014) Scheck & Siress Prosthetist Ryan Caldwell, CP/L, FAAOP, Contributes to NUPOC Research. Scheck it out, February 24, 2014. http://www.scheckandsiress.com/scheck-it-out/index.php/scheck-siress-prosthetist-ryan-caldwell-cpl-faaop-contributes-nupoc-research-2/ 

Giving Highly Active Transfemoral Amputees a Lift: Shorter Prosthetic Sockets with a Vacuum Fit

Komolafe O, Wood S, Caldwell R, Hansen A, Fatone S (2013) Methods for characterization of mechanical and electrical prosthetic vacuum pumps . Journal of Rehabilitation Research and Development, 50(8):1069–78. PMID: 24458892.

Major M, Caldwell R, Fatone S (2015) Comparative effectiveness of electric vacuum pumps for creating suspension in transfemoral sockets. Journal of Prosthetics and Orthotics, 27(4):149–153.

Major M, Caldwell R, Fatone S (2015) Evaluations of a Hybrid Vacuum Pump to Provide Vacuum-assisted Suspension for Above-knee Prostheses. American Society of Mechanical Engineers, Journal of Medical Devices. doi:10.1115/1.4030507. Online Technical Brief at ASME Digital Collections: http://medicaldevices.asmedigitalcollection.asme.org/article.aspx?articleid=2290859

Murphy C (2013) Socket Technology and Design: the Future of an Evolving Practice. O&P Business News, February 2013.

World Congress highlight – Subischial sockets for persons with transfemoral amputation. ISPO ANMS eNews, March 2013.

Researchers Showcase Prosthetic Socket Design.” Northwestern Research News, September, 2015;8(1):11.

“Study Examines Comparative Effectiveness of Electric Vacuum Suspension Pumps” September 20, 2015. http://www.oandp.com/articles/NEWS_2015-09-20_02.asp 

Advanced O&P Solutions Facebook Page, September 29 2015. https://www.facebook.com/AOPSolutions/photos/a.462843250481741.1073741828.460835084015891/823255034440559/?type=3&theater 

Fairley M (2016) Expanding Clinical Skills and Knowledge: Rehabilitative Care for Wounded Warriors Meets Unique Challenges. The O&P Edge, February, 15(2):26-36. http://www.oandp.com/articles/2016-02_02.asp 

Kahle J and Highsmith JM (2016) The Newest Technology in Transfemoral Socket Interfaces. InMotion, March/April, 26(2):38-43. http://www.amputee-coalition.org/inmotion_online/inmotion-26-02-web/

Caldwell R, Fatone S (2016) Development of the Northwestern University Flexible Sub-Ischial Vacuum (NU-FlexSIV) Socket for Persons with Transfemoral Amputation. OT World Congress, May 3-6, Leipzig, Germany. Spotlighted in The O&P Edge “OTWorld Session Sneak Peeks.” http://www.oandp.com/articles/2016-04_10.asp

Related Presentations

Brown SE, Russell Esposito E, Ikeda A, Fergason J, Caldwell R, Fatone S, and Wilken JM (2016) Effect of Socket Design and Suspension on Walking Mechanics. George E. Omer Jr. Research and Alumni Lectureship. Brooke Army Medical Center, June 16, San Antonio, TX.

Caldwell R (2016) Modern Transfemoral Socket Alternatives and Technologies: The Science behind TFAs. 42nd American Academy of Orthotists and Prosthetists Annual Meeting & Scientific Symposium, March 9-11, Orlando, FL.

Fatone S (2016) The Final Frontier: Developments in Transfemoral Sockets. Invited speaker, NUFSM PM&R/RIC Clinical Research Grand Rounds, July 11, Chicago, IL. 

Fatone S, Caldwell R (2016) Socket-Related Research Collaborations at Northwestern University. Scheck Fair. April 8-9, Lombard, IL.

Caldwell R, Fatone S (2016) Development of the Northwestern University Flexible Sub-Ischial Vacuum (NU-FlexSIV) Socket for Persons with Transfemoral Amputation. OT World Congress, May 3-6, Leipzig, Germany.

Caldwell R and Fatone S (2016) Development of the Northwestern University Flexible Sub-Ischial Vacuum (NU-FlexSIV) Socket for Persons with Transfemoral Amputation 12th Annual Lewis Landsberg Research Day, April 7, Northwestern University, Chicago, IL (poster).

Caldwell R, Fatone S (2016) NU-FlexSIV Socket. NUPOC Biennial Symposium for the German-Speaking Travel Fellows of Initiative ’93, February 25, Chicago, Illinois. 

Caldwell R and Fatone S (2014) "Subischial Socket with Vacuum-Assisted Suspension for Persons with Transfemoral Amputation". Online webinar hosted by the American Academy of Orthotists and Prosthetists.

Caldwell, R. Subischial Socket Technology: Transfemoral Vacuum Concepts and Case Studies. Midwest Chapter American Academy of Orthotists and Prosthetists (AAOP) Annual Meeting & Scientific Session, September 27-29, 2012, Lake Geneva, WI.

Esposito ER, Fatone S, Wilken J, Caldwell R, Fergason J (2015) Sub-Ischial Prosthetic Sockets Improve Hip Range of Motion and Performance for Individuals with Transfemoral Amputations. 41st American Academy of Orthotists and Prosthetists Annual Meeting & Scientific Symposium, February 18-21, New Orleans, Louisiana.

Fatone S (2013) Development of Subischial Sockets for Persons with Transfemoral Amputation. Invited Speaker, ISPO Norge Seminar on “Lower Limb Socket Design and Rehabilitation”, October 22-23, Oslo and Åkershus University College, Norway.

Fatone S (2013) Evaluation of Subischial Sockets for Persons with Transfemoral Amputation. Invited Speaker, ISPO Norge Seminar on “Lower Limb Socket Design and Rehabilitation”, October 22-23, Oslo and Åkershus University College, Norway.

Fatone S (2016) Subischial Socket with Vacuum Assisted Suspension for Persons with Transfemoral Amputation. Danske Bandagister, April 1-2, Nyborg, Denmark. 

Fatone S and Caldwell R (2014) Subischial Socket with Vacuum Assisted Suspension for Persons with Transfemoral Amputation. Instructional course presented at the Canadian Association for Prosthetics and Orthotics (CAPO) Annual Conference, August 6-9, 2014, Halifax, Nova Scotia, Canada.

Fatone S, Caldwell R (2014) Subischial Socket with Vacuum Assisted Suspension for Persons with Transfemoral Amputation. 40th American Academy of Orthotists and Prosthetists Annual Meeting & Scientific Symposium, February 26-March 1, Chicago, Illinois.

Fatone S, Caldwell R (2015) An Introduction to Sub Ischial Sockets with Vacuum Assisted Suspension. Midwest Chapter, American Academy of Orthotists and Prosthetists Annual Meeting and Scientific Session, May 27-29, Rosemont, IL.

Fatone S, Caldwell R, Komolafe O, Tucker K. Subischial Sockets with Vacuum Assisted Suspension for Persons with Transfemoral Amputation. Instructional Course, World Congress of the International Society for Prosthetics and Orthotics, February 4-7, 2013, Hyderabad, India.

Fatone S, Howell J, Caldwell R, Komolafe O, Stine R. Role of socket design, flexibility and suspension in transfemoral sockets during walking (poster). 39th Academy Annual Meeting and Scientific Symposium of the American Academy of Orthotists & Prosthetists, February 20-23, 2013, Orlando FL.

Fatone S, Wood S, Caldwell R, Chen W, Sun C, Hansen A, Komolafe O. Characterization of Mechanical and Electrical Vacuum Pumps for Use in Vacuum-Assisted Suspension (poster). 14th World Congress of the International Society of Prosthetics and Orthotics, February 4-7, 2013, Hyderabad, India.

Fatone S, Wood S, Caldwell R, Chen W, Sun C, Hansen A, Komolafe O (2013) Characterization of Mechanical and Electrical Vacuum Pumps for Use in Vacuum-Assisted Suspension (poster). 9th Annual Lewis Landsberg Research Day, Northwestern University, April 4, Chicago, Illinois.

Fatone S, Wood S, Komolafe O, Caldwell R, Chen W, Sun C, Hansen A. Socket/Liner Interface Volume and Vacuum Pressure Decay in Persons with Transfemoral Amputations. 14th World Congress of the International Society of Prosthetics and Orthotics, February 4-7, 2013, Hyderabad, India.

Fatone S. Sub-ischial Prosthetic Socket with Vacuum-Assisted Suspension for Persons with Transfemoral Amputation, in Design of Medical Devices Conference. April 10-12, 2012, Minneapolis MN.

Komolafe O and Fatone S. Stress Analysis of Different Transfemoral Prosthetic Socket Frame Designs. Midwest Chapter American Academy of Orthotists and Prosthetists (AAOP) Annual Meeting & Scientific Session, September 27-29, 2012, Lake Geneva, WI.

Komolafe O, Caldwell R, Fatone S (2013) An analytic approach to assessing transfemoral socket flexibility. Midwest Chapter of the American Academy of Orthotists and Prosthetists, May 30-June 1, Lake Geneva, Wisconsin.

Komolafe O, Caldwell R, Fatone S. An analytic approach to assessing transfemoral socket flexibility. 39th Academy Annual Meeting and Scientific Symposium of the American Academy of Orthotists & Prosthetists, February 20-23, 2013, Orlando FL.

Komolafe O, Caldwell R, Fatone S. Stress Analysis of Different Rigid Frame Designs with a Flexible Transfemoral Prosthetic Socket. 14th World Congress of the International Society of Prosthetics and Orthotics, February 4-7, 2013, Hyderabad, India.

Komolafe O, Caldwell R, Tucker K, Sun C, Chen W, Hansen A, Fatone S. Stress Analysis of Different Rigid Frame Designs of within a Flexible Transfemoral Prosthetic Socket, in 38th American Academy of Orthotists and Prosthetists Annual Meeting and Scientific Symposium. March 21-24, 2012, Atlanta GA.

Komolafe O, Tucker K, Caldwell R, Fatone S. Quantification of Transfemoral Prosthetic Socket Fabrication (poster). Military Health System Research Symposium, August 13-16, 2012, Fort Lauderdale FL.

Komolafe OA, Caldwell, R, Fatone S. (2013) An Analytic Approach to Assessing Transfemoral Socket Flexibility. Texas Association of Orthotists and Prosthetists Annual Meeting, April 19-20, Dallas, Texas.

Robillard B, Komolafe O, Caldwell R, Fatone S (2013) Design of a process for fabricating prosthetic sockets with rapid prototyping technology (poster). InNUvations Applied Research Day, Northwestern University, May 2, Evanston, Illinois.

Robillard B, Komolafe O, Caldwell R, Fatone S (2013) Fabricating prosthetic sockets with rapid prototyping technology (poster). 3rd Annual Musculoskeletal Research Day, Northwestern University, August 27, Chicago, Illinois.

Robillard B, Komolafe O, Caldwell R, Fatone S (2013) Design of a Process for Fabricating Prosthetic Sockets with Rapid Prototyping Technology. 9th Annual Lewis Landsberg Research Day, Northwestern University, April 4, Chicago, Illinois.

Robillard B, Komolafe O, Caldwell R, Fatone S (2013) Fabricating prosthetic sockets with rapid prototyping technology. Biomedical Engineering Society (BMES) Annual Meeting, September 25-28, Seattle, Washington.

Wood S, Caldwell R, Chen W, Sun C, Hansen A, Fatone S. Socket/Liner Interface Volume and Vacuum Pressure Decay in Persons with Transfemoral Amputations in 38th American Academy of Orthotists and Prosthetists Annual Meeting and Scientific Symposium. March 21-24, 2012, Atlanta GA.

Wood S, Caldwell R, Chen W, Sun C, Hansen A, Komolafe O, Fatone S. Characterization of Mechanical and Electrical Vacuum Pumps for Use in Vacuum-Assisted Suspension in 38th American Academy of Orthotists and Prosthetists Annual Meeting and Scientific Symposium. March 21-24, 2012, Atlanta GA.

AOPS Features NU-FlexSIV Socket at AOPA 2015 
Photo courtesy of Mike Angelico, AOPS

Dr. Fatone to Present Plenary Lecture 

Dr. Fatone will present "Flexible Subischial Vacuum Socket for Transfemoral Amputee" at the 2016 Asian Prosthetic and Orthotic Scientific Meeting (APOSM) on November 5, 2016, in Seoul, Korea.

Slides from 2016 NU-FlexSIV Socket Course

The 2016 Courses were fully subscribed and attend by Prosthetists and their patients from throughout the USA and Canada. 

Prosthetists Fill NU-FlexSIV Socket Courses

Socket developer Ryan Caldwell, CP, FAAOP, presents information about subischial socket and vacuum technology.

Prosthetists engaged in didactic and hands-on activities during the 2-day NU-FlexSIV Socket Courses.

Socket developer Ryan Caldwell, CP, provided group and individual training.

Socket developer Ryan Caldwell, CP, FAAOP, conducted demonstrations and interacted one-on-one with participating prosthetists.

Prosthetists brought patient models to fit with an NU-FlexSIV socket.

Prosthetists from throughout the USA and Canada brought their patient models and fit them with a NU-FlexSIV Socket. Most persons with TFA said that they felt comfortable and stable wearing the NU-FlexSIV Socket.