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contact. Canadian Prosthetics & Orthotics Journal, Volume 1, Issue 2, No 2, 2018. DOI: https://doi.org/10.33137/cpoj.v1i2.30843 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 
 
 
 

 
 

 

 

 

 

 

 

 

 

 

 

 

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Campbell L, Lau A, Pousett B, Janzen E, Raschke S.U. How infill percentage affects the ultimate strength of 3D-printed transtibial sockets during 
initial contact. Canadian Prosthetics & Orthotics Journal, Volume 1, Issue 2, No 2, 2018. DOI: https://doi.org/10.33137/cpoj.v1i2.30843 

 

1 

 
RESEARCH ARTICLE  

 

 
HOW INFILL PERCENTAGE AFFECTS THE ULTIMATE STRENGTH OF 3D-PRINTED 
TRANSTIBIAL SOCKETS DURING INITIAL CONTACT 

 
Campbell L1, Lau A1*, Pousett B2, Janzen E3, Raschke S.U3 

 
1  Prosthetics and Orthotics, School of Health Sciences, British Columbia Institute of Technology (BCIT),  Burnaby, British Columbia,  

Canada. 
2 Barber Prosthetics Clinic, Vancouver, British Columbia, Canada.  
3 MAKE + Applied Research, Centre for Applied Research & Innovation (CARI), Burnaby, British Columbia, Canada. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 
 

 
OPEN  ACCESS 

ABSTRACT 

 
BACKGROUND: 3D printing is becoming more popular across many industries. 

The first step to safely introducing 3D printed sockets in to prosthetics is to 

conduct strength testing on these sockets. 

PURPOSE: This study tests how changing the infill percentage (the percentage 

of material between the internal and external socket wall) affects the strength 

of 3D-printed transtibial sockets. 

METHODS: A Fused Deposition Modelling (FDM) printer was used to print a 

total of nine transtibial (TT) sockets (three sockets at 30% infill, three sockets 

at 40% infill, and three sockets at 50%) using polylactic acid (PLA). A strength-

testing apparatus measured, in Newtons (N), the maximum load the 3D-printed 

transtibial sockets could withstand at initial contact of the gait cycle. 

RESULTS: Based on the specific criteria outlined in this research project, all 

nine sockets exceeded the 4480N threshold set by ISO Standard 10328. Eight 

out of nine sockets failed at approximately double the force required with one 

socket (socket #2) failing at 5360N. Seven out of nine sockets failed at the 

medial popliteal region and two out of nine sockets failed at lateral mid socket 

region. Differences in infill percentage from 30%, 40%, 50% did not appear to 

influence strength of sockets. 

CONCLUSION: Strength of 3D-printed TT sockets needs rigorous testing to be 

deemed safe for patient use. More definitive research and a higher number of 

samples are required to investigate how a larger range of infill percentage can 

affect strength. Until all the requirements of ISO Standard 10328 are satisfied, 

the safety of using 3D-printed TT sockets in clinical practice are uncertain. 

ARTICLE INFO 

Received: August   21, 2018 

Accepted: September 21, 2018 

Published: September 28, 2018 

 
CITATION 

Campbell L, Lau A, Pousett B, 

Janzen E, Raschke S.U. How 

infill percentage affects the 

ultimate strength of 3D-printed 

transtibial sockets during initial 

contact. Canadian Prosthetics & 

Orthotics Journal, Volume 1, 

Issue 2, No 2, 2018. 

https://doi.org/10.33137/cpoj.v1i

2.30843 

KEYWORDS 

Prosthetic socket, Transtibial, 

3D Printing, Infill percentage, 

Strength testing, Fused 

deposition modeling, Polylactic 

acid. 

INFILL PERCENTAGE EFFECTS ON 3D-PRINTED 
TRANSTIBIAL SOCKETS 

 
 

Volume 1, Issue 2, Article No. 2, September 2018 

 

 

ABBREVIATIONS 

FDM: Fused Deposition Modeling  

Fmax: Maximum force 

Fset: Settling test force 

Fsp: Static proof test force 

PLA: Polylactic Acid 

TIJ: Thermal Inkjet Printing 

SLS: Selective Laser Sintering  

*CORRESPONDING AUTHOR  
 

Adriel Lau, Prosthetics and Orthotics, School of Health Sciences,  

British Columbia Institute of Technology (BCIT),  3700 Willingdon Avenue, Burnaby, British Columbia, Canada. 

Email: lau.adriel@gmail.com 

 

DOI: https://doi.org/10.33137/cpoj.v1i2.30843 

 

https://doi.org/10.33137/cpoj.v1i2.30843
https://doi.org/10.33137/cpoj.v1i2.30843
https://doi.org/10.33137/cpoj.v1i2.30843
mailto:lau.adriel@gmail.com
https://doi.org/10.33137/cpoj.v1i2.30843


 

 

Campbell L, Lau A, Pousett B, Janzen E, Raschke S.U. How infill percentage affects the ultimate strength of 3D-printed transtibial sockets during 
initial contact. Canadian Prosthetics & Orthotics Journal, Volume 1, Issue 2, No 2, 2018. DOI: https://doi.org/10.33137/cpoj.v1i2.30843 

 

2 

 
OPEN  ACCESS 

INFILL PERCENTAGE EFFECTS ON 3D-PRINTED 
TRANSTIBIAL SOCKETS 

 
 

Volume 1, Issue 2, Article No. 2, September 2018 

 

 INTRODUCTION 

3D printing has been around for 30 years, but 

recently it has been making significant strides in the 

field of prosthetics. Some prosthetics and orthotics 

clinics have begun to use the technology in their 

practice due to the decrease in cost of 3D printers as 

well as the development of 3D scanning technology 

to efficiently capture the shape of a patient’s limb.1  

3D printing allows for increased cost efficiency and 

enhanced productivity.2 Because of this, 3D-printed 

prosthetic sockets are becoming an alternative 

option to traditional methods. However, 3D-printed 

sockets used for weight bearing should be tested 

rigorously to ensure patient safety.  

Ventola (2014) states that the three most common 

types of 3D printers used in medical applications are 

selective laser sintering (SLS), thermal inkjet (TIJ) 

printing, and fused deposition modeling (FDM).2 

During SLS printing, a laser draws the shape of the 

object in powder which fuses it together. TIJ printing 

“uses thermal, electromagnetic, or piezoelectric 

technology to deposit tiny droplets of ‘ink’ onto a 

substrate according to digital instructions”.2 FDM 

printers lay down layers of heated beads of plastic 

and these build the object layer by layer.  FDM 

printers are less expensive and more common than 

the SLS type printers.2  For this reason, they are likely 

the type of printer that prosthetics and orthotics 

clinics will have in their clinics.2 

The technology of 3D printing is advancing, but 

many of these designers are becoming more 

involved with the idea of creating prostheses when 

they have little to no concept of the intricacies of 

creating a prosthetic device nor the treatment 

planning involved. For example, Chhaya et al (2015) 

discuss several online groups that provide open‐

source files available for printing upper extremity 

devices.3 As both prosthetists and healthcare 

professionals, we believe there is a need to become 

more involved in the process of designing and 

testing safe 3D-printed sockets.  

Before additive manufacturing technology can be 

fully implemented in the prosthetics and orthotics 

field, there are barriers that must be addressed and 

resolved.4   

Strength Testing 

To ensure that weight bearing 3D-printed sockets are 

safe for patient use, they should adhere to the 

strength standards for lower extremity prostheses. 

ISO Standard 10328 is the international standard for 

the structural testing of lower limb prostheses and it 

outlines test methods.5   

ISO 10328 outlines the procedures for testing lower 

limb prostheses both statically and cyclically.5 The 

static test is a one-time, single-event test to 

determine the performance of a structure under a 

specific load. The cyclic test consists of a specific 

load applied to a structure multiple times or for many 

cycles, simulating conditions of normal walking.5   

Lower extremity prostheses must be tested to satisfy 

ISO 10328 standards loading condition I and II. 

Condition I loading “the instant of maximum loading 

occurring early in the stance phase of walking”.5  

Condition II loading “the instant of maximum loading 

occurring late in the stance phase of walking”.5 

There are three loading levels that can be tested in 

ISO 10328.  P5 is the loading condition that based 

on data from amputees with body masses are above 

and below 100 kg. P4 condition is for an amputee 

whose body mass is less than 80kg, and finally P3 

condition is less than 60 kg.5  

A literature search for the strength testing of 3D 

printed lower extremity prostheses did not produce 

any results. Other studies have used ISO standards 

to test the strength of non-3D printed lower extremity 

prostheses.  

Gerschutz et al., (2012) conducted a study 

examining static failure loads on traditional sockets.6 

In their study, mechanical testing on three different 

types of sockets was performed (thermoplastic 

check, copolymer and definitive laminated) for a total 

of n = 98 sockets. They were assessed for passing 

brittle failure = 4,426N and ductile failure = 3,421 N. 

This quantitative study evaluated socket strength to 

provide an understanding of the materials used for 

prosthetic sockets. 

Goh et al., (2002) tested complete prostheses using 

both cyclic and static procedures.7 The researchers 

conducted the static test procedure by subjecting the 

prosthesis to sinusoidal loads ranging from 50N to 

Fmax (Fmax=1330N for condition I and 

Fmax=1200N for condition II). The force was 

maintained for 30s and if permanent deformation of 

15mm or the prosthesis failed, the prosthesis was not 

found to be adhered to ISO 10328 standards.7 If the 

prosthesis did not fail, it proceeded to the failure 

https://doi.org/10.33137/cpoj.v1i2.30843


 

 

Campbell L, Lau A, Pousett B, Janzen E, Raschke S.U. How infill percentage affects the ultimate strength of 3D-printed transtibial sockets during 
initial contact. Canadian Prosthetics & Orthotics Journal, Volume 1, Issue 2, No 2, 2018. DOI: https://doi.org/10.33137/cpoj.v1i2.30843 

 

3 

 
OPEN  ACCESS 

INFILL PERCENTAGE EFFECTS ON 3D-PRINTED 
TRANSTIBIAL SOCKETS 

 
 

Volume 1, Issue 2, Article No. 2, September 2018 

 

 test. The article found that the polypropylene sockets 

passed the static load test with only minimal 

deformation and passed cyclic test of 250000 cycles 

with no failure. 

Infill percentage 

3D printing can change different parameters such as 

infill percentage. Infill percentage is the density of the 

plastic between the inner and outer walls of a printed 

object.8 Increasing the infill percentage on a 3D-

printed transtibial (TT) socket made from polylactic 

acid (PLA) should influence the ultimate strength of 

the socket.  Johansson (2016) states that low infill is 

weaker and more prone to cracking.8 Whereas, 

printing at 100% can increase printing time and cost 

and may not necessarily increase strength.8 It is 

valuable for the prosthetics and orthotics profession 

to determine at what infill percentage has adequate 

strength, but at the same time, does not take an 

excessive amount of time to print. 

The purpose of this study was to test how changing 

the infill percentage affects the strength of a 3D-

printed TT socket during initial contact. We 

hypothesized that greater infill percentage could 

correspond to a greater socket strength. This project 

collaborated with a research facility to investigate this 

concept and hope to be a part of a much bigger 

picture in progressing 3D printing as a tool to help the 

field of prosthetics. 

METHODS  

Settings 

This experimental study printed nine identical Total 

Surface Bearing (TSB) transtibial sockets. To 

maintain consistency, the sockets were all printed 

from the same data file supplied by the company 

Additive O&P in Charlotte, N.C. and Barber 

Prosthetics Clinic in Vancouver, B.C. 

The sockets were printed from a FDM printer located 

at Barber Prosthetics Clinic. The FDM printer uses a 

nozzle head that extrudes melted plastic layer by 

layer to create a three-dimensional structure.2 It took 

an average of 8-9 hours to print each socket. The 

sockets were all printed using a white PLA filament 

and were all reinforced with scotch cost. At the distal 

end, each socket was attached to a 5R1 wood block 

which served as the attachment point for the pylon in 

the strength testing apparatus. A Registered 

Prosthetic Technician oversaw the production and 

finished each 3D-printed transtibial socket as can be 

seen in Figure 1. 

Considering the various 3D printer parameters that 

were available to be evaluated, the authors chose to 

research infill percentage as a parameter because 

this variable was hypothesized to have a direct 

relationship with strength and print time. Three 

different infill percentages were chosen that would 

best represent realistic categories that clinicians may 

decide to print: Three sockets were printed at 30% 

infill, three sockets at 40% infill, and three sockets at 

50% infill. Table 1 describes the properties of each 

socket. 

Figure 1. 3D-Printed TT Socket 

Table 1. Characteristics of the 3D-Printed Sockets 

Socket # Infill % 
Length 
(cm) 

Weight - 
Unfinished (gr) 

Finished 
(gr) 

1 30 20.8 291 531 

2 30 20.8 304 543 

3 30 20.8 304 543 

4 40 20.8 297 527 

5 40 20.8 296 538 

6 40 21 302 543 

7 50 20.8 325 564 

8 50 20.9 324 574 

9 50 20.5 326 575 

Componentry 

This project worked closely with the Centre for 

Applied Research Institute (CARI) in Burnaby, BC to 

fabricate components that held the 3D-printed socket 

in the proper orientation for strength testing as can 

be seen in Figure 2. The components included an 

upper plate and bottom plate made from one-inch 

thick steel. The superior part of the upper plate and 

the inferior part of the lower plate contain a concave 

surface that articulated with two hitch balls which was 

attached to the strength testing apparatus. Firstly, 

this ensured a pure vertical force was generated as 

accurately and consistently as possible. Secondly, 

https://doi.org/10.33137/cpoj.v1i2.30843


 

 

Campbell L, Lau A, Pousett B, Janzen E, Raschke S.U. How infill percentage affects the ultimate strength of 3D-printed transtibial sockets 

during initial contact. Canadian Prosthetics & Orthotics Journal, Volume 1, Issue 2, No 2, 2018. DOI: https://doi.org/10.33137/cpoj.v1i2.30843 

 

4 

 
OPEN  ACCESS 

INFILL PERCENTAGE EFFECTS ON 3D-PRINTED 
TRANSTIBIAL SOCKETS 

 
 

Volume 1, Issue 2, Article No. 2, September 2018 

 

 
this allowed the plates to be oriented in the correct 

alignment for this project. This experiment focused 

on initial contact of the gait cycle as ISO 10328 states 

that during this phase, the socket experiences the 

largest loading force.5 Lastly, the plates can be 

placed in different orientations to test for multiple 

weight classes which are specified as P3, P4, and 

P5. Our study focused on P5 condition which is the 

loading condition that based on data from amputees 

with body masses are above and below 100 kg.  

 

Figure 2 (Left). Componentry Attached to 3D-Printed 
Socket. 

Figure 3 (Right). High-Density Urethane Residual Limb 
Model. 

To simulate a residual limb, a high-density urethane 

mold was fabricated as seen in Figure 3. The model 

was created from a mold of the socket shape which 

created an intimate fit thus simulating an appropriate 

fit with the TSB socket. The urethane mold and the 

upper plate were connected by a ⅝ bolt which 

allowed the load generated by the strength testing 

apparatus to be distributed throughout the entire 

socket. The bottom plate articulated with the socket 

through a solid piece of welded steel that acted as 

the pylon.  

Since existing prosthetic componentry such as the 

pylon, tube clamp adaptors and pyramids have 

already been tested to ISO standards, attempting to 

eliminate them from the equation is most logical to 

isolate the strength of the socket. Therefore, a 

311mm solid piece of steel was fabricated to satisfy 

these requirements. This piece of steel also 

contained a welded pyramid adaptor which allowed 

it to be attached to the wood block. 

 

Strength Testing Apparatus 

Strength testing was performed on a Tinius Olsen 

Universal testing machine as seen in Figure 4 (Left) 

and focused solely on static testing. Cyclic testing 

requires 3 million cycles,5 which would take 

approximately one year of continuous testing. Due to 

time and cost constraints, only ultimate strength 

testing was completed.   

The sockets were tested for ultimate strength. 

Ultimate strength is defined as static load 

representing a gross single event, which can be 

sustained by the prosthetic device/structure but 

which could render it unusable.5 The static load will 

be applied for testing condition I which is described 

as evaluating the instant of maximum loading during 

early stance phase or initial contact of the gait cycle. 

Each socket was tested to ISO standards where the 

force measurement data was gathered in Newtons 

(N). 4480N was the force required in order to pass 

the standards outlined in ISO 10338.5 Furthermore, 

if the sockets surpassed the threshold, they were 

subjected to further testing and compressed to failure 

to determine how much force is required before 

breaking the socket. 

The procedure for principal static ultimate strength 

test as per ISO standard 10328 is as follows:  

A force was steadily increased at a constant rate 

between 100 N/s and 250 N/s to 2240 N and held for 

10-30 seconds (Values are recorded). The force was 

removed and the socket rested at zero load for one 

minute. The force was again steadily increased at a 

constant rate between 100 N/s and 250 N/s to 4480 

N and held for 30 seconds (Values are recorded). If 

the socket had not failed, a compression force 

continued and the load was increased until failure 

was reached. Figure 4 (Right) provides a visual 

representation of the 3D-printed socket attached to 

all the componentry. 

RESULTS 

Force at Socket Failure 

The results of the strength testing procedure were 

recorded in Table 2. These recordings include the 

settling test force (Fset), the amount of time each 

socket spent at Fset, the amount of time the socket 

spent with no force between Fset and the static proof 

test (Fsp), the actual force at Fsp, the time the socket 

spent at Fsp, the force that the socket ultimately 

https://doi.org/10.33137/cpoj.v1i2.30843


 

 

Campbell L, Lau A, Pousett B, Janzen E, Raschke S.U. How infill percentage affects the ultimate strength of 3D-printed transtibial sockets 

during initial contact. Canadian Prosthetics & Orthotics Journal, Volume 1, Issue 2, No 2, 2018. DOI: https://doi.org/10.33137/cpoj.v1i2.30843 

 

5 

 
OPEN  ACCESS 

INFILL PERCENTAGE EFFECTS ON 3D-PRINTED 
TRANSTIBIAL SOCKETS 

 
 

Volume 1, Issue 2, Article No. 2, September 2018 

 

 
failed at, and whether the socket passed the 

minimum force dictated in the ISO Standard 10328. 

 

Table 2. Results of Loading Procedure (Note: Fset = 

Settling test force, Fsp = Static proof test force). 

 

Both the Fset and Fsp forces listed in table 2 are 

different for each socket due to the setting 

capabilities of the strength testing apparatus. The 

apparatus was controlled via a dial, so a specific set 

point for both Fset and Fsp was not possible. The 

accuracy of these points depended solely on the 

operator of the strength testing apparatus pausing 

the loading at a force close to the intended forces 

(laid out in the methods) of Fset = 1024 N and Fsp= 

2240 N.  

Figure 5 shows the force at failure of all 3D-printed 

sockets. The black threshold line indicates the 

minimum threshold (4480 N) that the ISO standards 

dictates for condition I, weight class P5. As shown in 

Figure 6, all the sockets surpassed the threshold and 

all sockets (with the exception of socket number 2) 

failed at approximately double the force required by 

ISO standards 

Figure 5. All 3D printed transtibial sockets failed above the 

ISO standard for this condition.  

Visual Analysis of Socket Failure 

Table 3 shows the area that the sockets failed at as 

well as the type of socket failure. Most sockets failed 

in the medial popliteal region (seven of nine sockets) 

and two of the nine sockets failed in the lateral mid 

socket region. An example of a medial popliteal area 

socket failure is shown in Figure 6 (left). Figure 6 

(right) shows an example of a socket failing in the 

lateral mid socket.  

Table 3. Area of Socket Failure and Failure Type 

Socket # Infill % Failure point Failure Type 

1 30 medial popliteal crack 

2 30 lateral mid socket crack 

3 30 medial popliteal complete 

4 40 medial popliteal crack 

5 40 lateral mid socket crack 

6 40 medial popliteal crack 

7 50 medial popliteal complete 

8 50 medial popliteal crack 

9 50 medial popliteal crack 

 

Figure 6. Left: Socket broken in the medial popliteal area; Right: 

Socket broken in the middle lateral area.  

S
o
c
k
e
t 

#
 

In
fi
ll 

%
 

F
s
e
t 

(N
) 

F
s
e
t 

ti
m

e
 

(s
) 

T
o
ta

l 
re

s
t 

ti
m

e
 (

s
) 

F
s
p
 (

N
) 

F
s
p
 t

im
e
 

(s
) 

F
o

rc
e
 a

t 
fa

ilu
re

 (
N

) 

P
a
s
s
 

M
in

im
u

m
 

(4
4

8
0
 N

) 

1 30 1079 15 60 2630 30 11854 Y 

2 30 1074 10 60 2438 30 5360 Y 

3 30 1070 10 60 2303 30 12841 Y 

4 40 1114 10 60 2314 30 9009 Y 

5 40 1147 10 60 2425 30 10345 Y 

6 40 1216 10 60 2266 30 11383 Y 

7 50 1252 10 60 3457 30 11965 Y 

8 50 1115 10 60 2371 30 12243 Y 

9 50 1177 10 60 2491 30 9847 Y 

Figure 4. Left: Tinius Olsen Universal Testing 

Apparatus; Right: Completed set-up.  

https://doi.org/10.33137/cpoj.v1i2.30843


 

 

Campbell L, Lau A, Pousett B, Janzen E, Raschke S.U. How infill percentage affects the ultimate strength of 3D-printed transtibial sockets during 
initial contact. Canadian Prosthetics & Orthotics Journal, Volume 1, Issue 2, No 2, 2018. DOI: https://doi.org/10.33137/cpoj.v1i2.30843 

 

6 

 
OPEN  ACCESS 

INFILL PERCENTAGE EFFECTS ON 3D-PRINTED 
TRANSTIBIAL SOCKETS 

 
 

Volume 1, Issue 2, Article No. 2, September 2018 

 

 Table 3 shows that the primary method for socket 

failure was a crack in the socket (seven of the nine 

sockets). A crack failure type was defined as a failure 

in which the proximal and distal aspects of the socket 

remained attached. Figure 6 shows examples of a 

crack failure. Figure 7 shows an example of a 

complete failure of the socket. In this case, the 

proximal and distal aspects of the socket are 

completely separated from each other. Two of the 

nine sockets failed in this manner. 

Figure 7: Complete Socket Failure 

DISCUSSION 

The purpose of this research project was to evaluate 

how changing infill percentage would affect the 

ultimate strength of a 3D-printed TT socket. To safely 

use these sockets in either a diagnostic or a definitive 

phase, the efficacy and effectiveness of these 

devices must be clearly shown.9 3D-printed sockets 

should satisfy the same requirements as lower limb 

conventional prostheses as stated in ISO Standards 

10328. Based on the results, the sockets in this study 

exceeded the threshold of 4480 N. However, it is 

important to note that the sockets were evaluated 

with a specific set of criteria. The conditions of static 

testing, initial contact (condition I) and P5 weight 

class were implemented and only under these 

conditions did all of the sockets exceed the 

threshold. To fully deem a 3D-printed socket safe for 

patient use, the other criteria explained in ISO 

standard 10328 will also need to be satisfied. For 

example, cyclic testing needs to be performed where 

the socket is continuously compressed through a low 

load, long duration setting. This will better simulate a 

socket when completing activities of daily living.  

Furthermore, it has been seen in clinical practice that 

sockets often fail during terminal stance in the gait 

cycle. Testing in this specific phase of the gait cycle 

in addition to initial contact, will provide a more 

encompassing picture as an individual ambulates. 

Testing each of these conditions in all the weight 

classes (P3, P4 and P5) will also need to be 

completed to fully satisfy safety requirements. 

The infill percentage did not appear to influence the 

ultimate strength of the sockets. It was hypothesized 

that a greater infill percentage would require a 

greater force for a socket to fail. However, the results 

show that all the sockets failed at approximately 

twice the required force (except for socket #2). 

Perhaps the range of infill percentage was not large 

enough to see a difference in ultimate strength. In the 

future, choosing a larger gap in infill percentage may 

show difference in the force values required for a 

socket to fail. Another possible explanation for this 

result is that the other parameters used for the 

sockets were structurally weaker so the infill 

percentage was not the factor that influenced failure. 

The failure points occurred in different areas of the 

socket during the experiment; however, it was 

observed that all the failure points occurred above 

the reinforced scotch cast. With a diagnostic socket, 

it is more advantageous that reinforcement methods 

be done to create additional strength and stability. 

With the breaks occurring above this area, this 

suggests that the reinforced area is successful in 

delegating the force to an area that is less strong. 

Knowing this, removing the reinforced scotch cast in 

might have shown different results when evaluating 

for ultimate strength. As mentioned earlier, the 

sockets broke in different areas with seven of the 

nine sockets failing on the medial popliteal area and 

two of the nine sockets failing at the middle, lateral 

area of socket. Two of the sockets also experienced 

complete failure where the socket was broken into 

two separate pieces. There was no predictability and 

no trend was seen as to how a socket broke 

compared to its failure values. 

Limitations 

The limitations of this study included the small 

sample size of sockets. Due to cost and time 

constraints, only nine sockets were printed as this 

was a logical way to compare sockets printed at 

different infill percentages. Because of the small 

sample size, we were unable to comment on any 

significant differences and can only comment on 

https://doi.org/10.33137/cpoj.v1i2.30843


 

 

Campbell L, Lau A, Pousett B, Janzen E, Raschke S.U. How infill percentage affects the ultimate strength of 3D-printed transtibial sockets 

during initial contact. Canadian Prosthetics & Orthotics Journal, Volume 1, Issue 2, No 2, 2018. DOI: https://doi.org/10.33137/cpoj.v1i2.30843 

 

7 

 
OPEN  ACCESS 

INFILL PERCENTAGE EFFECTS ON 3D-PRINTED 
TRANSTIBIAL SOCKETS 

 
 

Volume 1, Issue 2, Article No. 2, September 2018 

 

 
general trends. Future studies should focus on 

printing a larger number of sockets encompassing a 

wider variety of infill percentages which could enable 

the generation of a statistical analysis. 

In general, more testing is needed to be done on the 

strength of 3D-printed sockets. The settings of 3D 

printing can be optimized and customized to the user 

or practitioner’s preferences. As a result, evaluating 

how individual parameters affect the strength of a 

socket would be beneficial. This study focused on 

infill percentage as an attempt to isolate its effects 

and how changing this setting would ultimately affect 

its strength.  

No articles were found regarding the evaluation of 

the ultimate strength of a 3D-printed TT socket. 3D 

printing is a relatively new technology in the field; 

therefore, there is not enough data currently to 

perform meta-analysis. There are also no 

randomized control trials to investigate the efficacy of 

these sockets which created a challenge in 

narrowing down the testing procedures and 

methodology process. With 3D printing technology 

advancing at an impressive rate, future directions 

should consider investigating how different printers, 

different materials and how different methods of 

printing can affect the strength of a socket. 

CONCLUSION 

3D printing technology is currently being used in 

many different industries. The field of prosthetics and 

orthotics needs to embrace this technology and 

demonstrate how it can be successfully used in 

clinical practice. A logical first step is testing the 

strength of 3D-printed prosthetic sockets to 

determine if it is safe for patient use. This research 

project demonstrated that the amount of force 

required for a socket to fail exceeded the 4480N 

threshold set by ISO Standard 10328. Furthermore, 

infill percentages ranging from 30% to 50% did not 

seem to affect the ultimate strength of the sockets. 

However, it should be noted that the sockets were 

tested to specific and limited criteria (static testing, 

initial contact and P5 weight class). This project is a 

stepping stone to much more extensive research and 

as such, further work is recommended to investigate 

how different parameters can influence the strength 

of socket. Moreover, additional conditions outlined by 

the ISO standards need to also be satisfied to 

determine if 3D-printed prosthetic sockets are safe 

and suitable for patients. 

ACKNOWLEDGEMENT 

The authors would like to thank Dave Moe (CP), 

Daryl Murphy (RTP), and Malena Rapaport (CP) 

from Barber Prosthetics Clinic. The authors would 

also like to thank Additive O&P, the Centre for 

Applied Research Institute, Dr. Nathan Devos and 

Caroline Soo for their guidance and support 

throughout this project. 

DECLARATION OF CONFLICTING 
INTERESTS 

Barber Prosthetics Clinic donated the use of their 3D 

printer and the PLA used to print the sockets. The 

researchers did not receive any financial 

compensation for this project.  

ETHICAL APPROVAL 

Not required 

AUTHOR CONTRIBUTION  

• Leah Campbell: Conceptualization, formal 

analysis, investigation, methodology, 

visualization, writing original, review & editing. 

• Adriel Lau: Conceptualization, formal analysis, 

investigation, methodology, visualization, writing 

original, review & editing. 

• Brittany Pousett: Conceptualization, 

investigation, visualization, supervision, review & 

editing. 

• Ernie Janzen: Investigation, visualization, 

methodology, review & editing.  

• Silvia Ursula Raschke: Conceptualization, 

visualization, review & editing. 

 

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Campbell L, Lau A, Pousett B, Janzen E, Raschke S.U. How infill percentage affects the ultimate strength of 3D-printed transtibial sockets during 
initial contact. Canadian Prosthetics & Orthotics Journal, Volume 1, Issue 2, No 2, 2018. DOI: https://doi.org/10.33137/cpoj.v1i2.30843 

 

8 

 
OPEN  ACCESS 

INFILL PERCENTAGE EFFECTS ON 3D-PRINTED 
TRANSTIBIAL SOCKETS 

 
 

Volume 1, Issue 2, Article No. 2, September 2018 

 

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https://doi.org/10.33137/cpoj.v1i2.30843
http://dx.doi.org/10.1682/JRRD.2011.05.0091
https://doi.org/10.1243/095441102321032157
http://urn.kb.se/resolve?urn=urn:nbn:se:bth-12355
https://doi.org/10.1177/0309364617704803

