Nuflex-SIV Above Knee Socket in Kansas City

Nuflex-SIV Above Knee Socket in Kansas City

By: Shelli Hale, CPO

Overcoming socket discomfort with the Nuflex-SIV Above the Knee Socket.

There are many challenges to everyday  life for amputees that many people wouldn’t understand.  s for the above knee amputee, despite all the technology and advancements in prosthetic componentry (knees and feet), the most limiting factor for an above knee amputee is often socket comfort.


The evolution of above the knee sockets & their discomfort

The last 4 decades have brought us many ideas and designs for ischial containment sockets. These designs have been very successful in providing the patient with improved socket stability and comfort.  But, by containing the ischium, the socket must come up very high on the patient’s limb (above the hip joint). The problem with this has been complaints of sitting discomfort, weight of the socket and lack of range of motion of the hip joint.

Causes of prosthetic discomfort:


The weight of the prosthesis can cause a decrease in energy efficiency.  This extra weight makes it much harder for the amputee to get through the day.

Skin issues

Skin issues are another problem that can limit the amputee from going through the day unrestrained by their prosthesis.  Sockets that go high into the groin area are much more likely to cause discomfort and irritation.

Limited hip range motion

Lack of hip range of motion limits the amputee from taking normal steps and limits sidestepping, getting in and out of cars, exercising and other activities that the active amputee wants to be able to do.





Several years ago, a prosthetist in Chicago (Ryan Caldwell, CP) developed a new subischial socket design which had good results for many of his patients. Particularly very active patients, including young veterans wanting to return to an active lifestyle. When he teamed up with Northwestern University and the Department of Defense to develop a teaching technique for this socket design it was obvious that this design had some merit. The NUPOC faculty, led by Ryan Caldwell, CP/L, FAAOP, and Stefania Fatone, PhD, BPO(Hons), began teaching the new socket technique to prosthetists throughout the United States and Canada.


The NU-FlexSIV Socket has lower proximal trim lines that do not impinge on the pelvis, it is also flexible, so muscles can move comfortably within  the socket as they contract during activity and splay during sitting.

Socket Comparisons

Nu-FlexSIV Socket                                                                   Traditional Socket

        –  Elevated vacuum suspension                                                       –  Suction suspension or belt

        –  Highly compressive liner                                                               –  Low compression liner or No liner

        –  Flexible inner socket                                                                      –  Rigid socket or Flexible inner socket

        –  Low profile brim                                                                              –  High brim into the groin area

        –  Sub-ischial trim line for comfort                                                   –  Ischial containment

This socket system includes a highly compressive liner; a flexible inner socket; and a shorter, rigid outer socket with vacuum applied between the liner and inner socket. 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.


In 2015, I was encouraged by HOPE president, Mike Schultz, to take the first Northwestern University class on this new socket design.  A sub-ischial design?  A flexible socket?  How could this work?  It wasn’t long into the training that I was convinced.  And so was my patient model. The sub-ischial design has been tried in many ways unsuccessfully.  By including the flexible socket and the elevated vacuum, the combination works.

Since the training, many NUFLEX-SIV sockets have been fit by the clinical staff at HOPE. Our patients report that they are much more comfortable, have more energy and fewer problems throughout their day. Having worn the NUFLEX-SIV socket, patients often say they would never want to go back to the old socket design.

The clinical team at HOPE is very excited to bring this socket technology to the amputee community of the Kansas City Area.  It is our goal to help people with amputations accomplish their goals and remaining active.