Amputee socks

Abstract

Background: The term 'sock ply' may be a source of confusion in prosthetics practice because there may not be a consistent relationship between sock ply and sock thickness. Objectives: The purpose of this study was to characterize how sock ply related to sock thickness for different sock materials commonly used in limb prosthetics. We also evaluated how sock thickness changed under loading conditions experienced while wearing a lower limb prosthesis compared with unstressed conditions. Study Design: Experimental. Mechanical assessment. Methods: Seven sock materials of varying ply and sheaths were tested using a custom instrument. Sock thickness under eight different compressive stress conditions and two different biaxial in-plane tensile strain conditions were measured. Results: For socks woven from a single material, thickness under walking stance phase conditions averaged 0.7, 1.2 and 1.5 mm for 1, 3 and 5-ply, respectively. For socks woven from several materials, the corresponding results were 0.4, 0.7 and 0.8 mm, respectively. Sock ply did not sum, e.g. a 3-ply sock was not three times the thickness of a 1-ply sock. Conclusions: Sock thickness and compressive stiffness are strongly dependent upon sock material, interface pressure, and in-plane biaxial strain. Clinical relevanceData may be useful towards selecting socks during fitting and towards understanding volume changes induced by adding socks. An alternative nomenclature for thickness based on sheath equivalence may be more intuitive to practitioners and to the industry.

How does adding and removing liquid from socket bladders affect residual-limb fluid volume?

“…The issue is relevant for people with trans-tibial amputation because socket fit is so sensitive to small volume changes. A study on 10 subjects with trans-tibial limb loss showed that an experienced practitioner, using static fitting procedures, identified sockets oversized by just 0.25 mm mean radial thickness (approximately half the thickness of a new 3-ply Soft Sock (Knit-Rite) while worn on a residual limb during walking [12]) as needing sock addition or other modification [13]. If increasing bladder liquid volume reduces residual limb fluid volume then more bladder liquid may need to be added, either manually or automatically, to compensate.…”

Effects of socket size on metrics of socket fit in trans-tibial prosthesis users

“…Since relationships between ply and thickness vary by sock model and because sock thickness changes over time [12,13,56] , use of a sock thickness caliper may facilitate measurement.…”

“…A custom tabletop instrument that applied controlled pressures during measurement was used [12] . Thickness was recorded under four different pressure conditions to reflect the following clinical activities: donned (6.3kPa); donned-conditioned (subject to compressive loading cycles before testing) (6.3kPa); equal weight-bearing (50.6kPa); and stance phase weight-bearing (101.2kPa) [13] .…”

Technical note: Computer-manufactured inserts for prosthetic sockets

“…If the fit was deemed acceptable for regular clinical use, sock thickness was measured using a custom instrument [10]. If sock thickness was less than 1.8mm (approximately the thickness of a new 5-ply sock under weight-bearing) then the participant was continued in the study, and a new socket and insert were created.…”