presented by John Fergason
Why is the interaction between the residual limb and the socket so critical? Many fitting problems can be solved if a full understanding of the socket biomechanics is gained. This course relates the forces that occur on the limb in each phase of gait, allowing the clinician to isolate issues that may hinder progress in therapy. It also explores why the training of the patient with a transfemoral amputation is so much more complicated. The transfemoral patient has no direct muscle control of the knee function. Knee stability and control are of paramount importance to maintain safety and stability during ambulation. This course will correlate the forces that occur both on the limb and the knee to each phase of gait. Problem solving can be augmented by noting the knee stability at each phase of gait and how the skin appears after ambulation.
John Fergason, CPO, is the Chief Prosthetist at the Center for the Intrepid at San Antonio Military Medical Center. He was formerly an Instructor and Clinical Manager for the Prosthetics-Orthotics Program at UT Southwestern in Dallas, TX and proceeded to become the Director of the Division of Prosthetics-Orthotics at the University of Washington in Seattle, WA. He currently is adjunct faculty for the Baylor Prosthetics-Orthotics Program and the UT Southwestern Prosthetics-Orthotics Program. He has lectured extensively on all topics in lower limb prosthetics, has many peer-reviewed articles and has authored multiple book chapters. While at Brooke Army Medical Center, he has developed the services from a small laboratory serving the local needs of the hospital to an international Center aimed at improving function for service members who have sustained catastrophic limb injury. His staff continues to treat the most complex patients seen as a result of battlefield injury and has become established as one of the primary military centers for limb loss.
Socket design is directly related to the regions of weight bearing ability on the residual limb. This chapter will emphasize relation between the socket and residual limb in both the static and dynamic environment.
Biomechanics of transtibial gait is the foundation for successful early ambulation training with a transtibial prosthesis. Emphasis will be placed on the terminology most applicable to apply a framework of understanding of the forces placed on the residual limb during ambulation.
This chapter now builds on the previous knowledge of weight bearing regions of the limb and the biomechanical forces that act upon it during each phase of gait. Each phase of gait will be discussed in the context of the tibial position within the socket and how this affects the ability to ambulate efficiently.
Transfemoral socket design continues to evolve as various theories are introduced and incorporated into the field of study. General weight tolerant areas of the residual limb will be discussed and related to several common socket design approaches. This chapter emphasizes the dynamic nature of the femur position in both the coronal and sagittal planes during static standing and dynamic ambulation.
Biomechanics of transfemoral gait provides an understanding of how to train the patient to maintain knee stability during both level ground walking and when encountering environmental barriers. A review of terminology will provide a reference for a study of the importance of knee control in the context of each phase of gait.
Each phase of gait will be discussed in the context of the trochanter-knee-ankle (TKA) line, and the ground reaction force vector effect on the joint moments that affect knee stability.