Northwestern University Feinberg School of Medicine

Northwestern University Prosthetics-Orthotics Center

Pilot Study of the Effect of Socket Characteristics on Coronal Plane Stability During Gait of Persons with Unilateral Transfemoral Amputation

Project Director: Stefania Fatone, PhD

Co-Investigator: Rebecca Stine, MS

Collaborator: Robert Tillges, CPO, Tillges Certified Prosthetics and Orthotics Inc.

Funded by: National Institute on Disability and Rehabilitation Research (NIDRR)

Status: Completed

Purpose

Results of a survey of the P&O field conducted in 2006 as part of the NU-RERC State of the Science Conference indicated that prosthetists and prosthesis users thought that the socket/interface was the most important area of prosthetics to which research efforts should be directed. Prosthetic sockets form the interface between the residual limb and the prosthesis and are important for the transmission of forces and distribution of pressure. Hence, socket design is important to the overall comfort, control, and function an amputee may have.

Medial view of MAS socket
Medial view of MAS socket

There are two basic types of transfemoral prosthetic sockets, the quadrilateral and ischial containment sockets. While the geometry of the quadrilateral socket has been consistently defined, there exist many variations in ischial containment socket design. A recent variant of the ischial contaiment socket design, the Marlo Anatomical Socket (MAS) (see picture) has been proposed and is purported to allow increased range of motion while still providing sufficient control and stability during gait. In the MAS, more aggressive containment of the ischial ramus medially (via the medial 'ear') is coupled with lower anterior and posterior trim lines than previous iterations of the ischial containment socket. Despite the proliferation of different transfemoral prosthetic socket designs, there is limited objective analysis available of their effect on the biomechanics of the gait of persons with transfemoral amputation. One area of debate is the ability of transfemoral prosthetic sockets to provide coronal plane stability during gait. Two features of ischial containment socket design are thought to contribute to coronal plane stability. The first is appropriate containment of the ischium and ischial ramus. The second, relies in part on the soft tissue, especially the adductors located medially, being compressed to increase stiffness. The well-defined geometry of the MAS socket provides an ideal tool to investigate the contribution of these features of socket design to coronal plane stability. Therefore, the purpose of this pilot study is to use the MAS socket to investigate the contribution of ramal containment and soft tissue compression on coronal plane stability of the pelvis and transverse plane motion of the prosthetic limb during gait in persons with unilateral transfemoral amputation.

Method

The test socket used in this study was a copy of the subjects' current MAS that included a removable medial 'ear' and removable medial panels that allowed for randomized alterations in socket configuration during gait analysis. Three soft-tissue compression conditions were tested: high, medium and low, with the high compression condition representing recommended clinical practice.

Gait analysis was conducted on a single day. Subjects walked at a comfortable self-selected speed in 6 socket conditions in random order: (1) intact MAS; (2) MAS with one medial panel removed; (3) MAS with both medial panels removed; (4) MAS with medial 'ear' removed and both panels in place; (5) MAS with medial 'ear' and the first panel removed; and (6) MAS with medial 'ear' and both panels removed.

We recorded Socket Comfort Score (0 represents the most uncomfortable socket fit imaginable and 10 represents the most comfortable socket fit) (Hanspal et al. 2003), walking speed, step width, coronal plane hip moments, lateral trunk lean in prosthetic stance for each socket condition. Comfort and stability were expected to decrease incrementally from sockets 1 to 6.

Results

Six subjects were assessed. We found a strong relationship between comfort and changes in containment and tissue loading such that with the ischium contained, tissue loading did not influence socket comfort. With no containment, the socket was equally comfortable with high tissue loading but comfort decreased significantly with less tissue loading. The gait variables assessed were invariant to changes in containment and/or tissue loading (Fatone et al., in press).

References

Hanspal, R. S., K. Fisher, et al. (2003). "Prosthetic socket fit comfort score." Disability and Rehabilitation 25(22): 1278-1280.

Publications and Presentations

Fatone S, Dillon M, Stine R, Tillges R. (2014) Coronal plane stability during gait in persons with unilateral transfemoral amputation: a pilot study. Journal of Rehabilitation Research and Development 51(8)1217-1228.

Fatone S, Dillon M, Stine R, Tillges R (2015) Coronal plane socket stability during gait in persons with transfemoral amputation: Pilot study. World Congress of the International Society for Prosthetics and Orthotics, June 22-25, Lyon, France. Prosthetics and Orthotics International, 39(Supplement 2):317. DOI number: 10.1177/0309364615591101.

Garrick RJ and Fatone S. "Marlo Anatomical Socket Studied for Coronal Plane Stability." Capabilities 21(1)1-2, winter 2013.

Fatone S, Stine R, Tillges R. (2013) Effect of socket characteristics on coronal plane stability during gait in persons with unilateral transfemoral amputation. 39th Academy Annual Meeting and Scientific Symposium of the American Academy of Orthotists and Prosthetists, February 20-23, Orlando, Florida.

Fatone S, Stine R, Tillges R. (2013) Effect of socket characteristics on coronal plane stability during gait in persons with unilateral transfemoral amputation. Midwest Chapter of the American Academy of Orthotists and Prosthetists, May 30-June 1, Lake Geneva, Wisconsin.