







































Söderberg B, Guerra G, Fagerstrom T, Permpool K, Phaipool S. The Söderberg socket 2.0: A technical note. Canadian Prosthetics & Orthotics Journal. 
2019;Volume2, Issue2, No.3. https://doi.org/10.33137/cpoj.v2i2.33505  

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 
 

 
 

 
 

 

 

 

 

 

ISSN: 2561-987X 

VOLUME 2, ISSUE 2 

 2019 

 

(ONLINE) 

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  1 

 
OPEN  ACCESS 

THE SÖDERBERG SOCKET 2.0 

Volume 2, Issue 2, Article No.3, 2019 

 

 

Journal Homepage: https://jps.library.utoronto.ca/index.php/cpoj/index 

 

TECHNICAL NOTE 

 

THE SÖDERBERG SOCKET 2.0: A TECHNICAL NOTE  

 
Söderberg B1, Guerra G2*, Fagerstrom T1, Permpool K1,2, Phaipool S1,2  
 

1 Centre of Excellence for Prosthetics and Orthotics, Scandinavian Orthopaedic Laboratory, Bangkok, Thailand.   
2 Sirindhorn School of Prosthetics and Orthotics, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand. 

 

 

 

 

 

 

 

 

 

 

 

 

 

INTRODUCTION   

Prosthetic interface, socket technologies and suspension 

variants have evolved in recent years to allow for a greater 

adjustability of the prosthesis to the extremity. Numerous 

transtibial prosthesis technologies work to facilitate an 

improved dynamic fitting or aid the overall function of the 

individual.1 Various modifications to the socket can 

augment suspension characteristics and even assist gait 

of the user.2 Some companies have focused on utilizing 

ratcheting technologies to aid in adjustability of the 

prosthesis socket, such as the BOA system (Click Medical, 

BOA, Steamboat Springs, Colorado, USA). In this same 

vein, it is equally important to augment the range of motion 

for individuals with specific seating, cycling, kneeling and 

walking requirements. Trim lines have remained 

consistent in the literature and exploration of various 

socket trim lines might offer patient functional 

improvements. 

 

Transtibial prosthesis wearers participating in cycling or 

squatting and seating might benefit from an enhanced 

knee range of motion. This is also true when sitting down, 

for example, in a chair or a car seat. Traditional transtibial 

socket trim lines extend the medial and lateral walls 

proximally over the epicondyles.3 The rationale for doing 

so is rooted in habits and seldom questioned. Higher trim 

lines of the supra-condylar and Patella Tendon Bearing 

(PTB) styles were previously justified because of the 

introduction of the supracondylar suspension and to 

enhance medial lateral stability. Anterior-posterior and 

medial-lateral trim lines are rigid and encompass the 

proximal aspect of the socket in the below knee prosthesis. 

This conventional design has still remained, even if supra-

condylar and cuff suspension methods have shifted 

towards vacuum.1 Recent transtibial socket clinical 

guidelines have served to aid the prosthetist decision 

ABSTRACT 

BACKGROUND: Transtibial prosthesis socket trim lines have remained fairly consistent over the past 

decade, and based on methods such as a supracondylar cuff suspension. However, with vacuum 

suspension methods, trim lines can change.  

OBJECTIVE: An objective of this technical note was to inform practitioners how to fabricate a socket in a 

better way. A step-by-step fabrication guide is provided for the prosthetist. 

METHODS: A unilateral transtibial amputee was selected for this technical note. We provide a detailed 

description of the different steps of fabrication as well as patient feedback. The fabrication involved 

fabrication of a vacuum socket using Pre-preg carbon fiber and anti-bacterial Ethylene-Vinyl-Acetate 

(EVA), as a proximal flexible brim.  

FINDINGS: The properties of EVA and Pre-preg carbon fiber allow for fabrication of a transtibial socket 

with a flexible proximal brim. The new design resulted in greater comfort and increased range of motion in 

the patient studied. The patient subjectively noted enhanced squatting and cycling capabilities while using 

the updated socket and flexible proximal brim.  

CONCLUSION: This technical note presented a fabrication guide for a new style of socket and preliminary 

patient feedback. Clinical studies evaluating functional and biomechanical effects of this new socket design 

are needed. 

CITATION 

Söderberg B, Guerra G, 

Fagerstrom T, Permpool K, 

Phaipool S. The Söderberg 

socket 2.0: A technical note. 

Canadian Prosthetics & 

Orthotics Journal. 

2019;Volume2, Issue2, No.3. 

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

2i2.33505 

 KEYWORDS 

Prosthesis, Transtibial 

Amputees, Amputation, 

Transtibial socket, Prosthetic 

suspension 

* CORRESPONDING AUTHOR 

Gary Guerra, Ph.D.  

Sirindhorn School of Prosthetics and Orthotics, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand.  

Email: gary.gue@mahidol.edu 

ORCID: https://orcid.org/0000-0002-0161-4616 

 

DOI: https://doi.org/10.33137/cpoj.v2i2.33505 

ARTICLE INFO 

Received: December 26, 2019 

Accepted: March 6, 2020 

Published: March 10, 2020 

 

https://jps.library.utoronto.ca/index.php/cpoj/index
https://doi.org/10.33137/cpoj.v2i2.33505
https://doi.org/10.33137/cpoj.v2i2.33505
mailto:gary.gue@mahidol.edu
https://doi.org/10.33137/cpoj.v2i2.33505


 

 

Söderberg B, Guerra G, Fagerstrom T, Permpool K, Phaipool S. The Söderberg socket 2.0: A technical note. Canadian Prosthetics & Orthotics Journal. 2019;Volume2, Issue2, 
No.3. https://doi.org/10.33137/cpoj.v2i2.33505  

 

2 

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Söderberg et al. 2019 

 THE SÖDERBERG SOCKET 2.0 

making process by offering greatly needed 

recommendations.4 Such as using vacuum suspension as 

a viable alternative to supracondylar and cuff  

suspensions.  

Our previous Söderberg socket 1.0 research evidenced 

that a lowered trim line design can mitigate excessive 

motion at the knee whilst still allowing the epicondyles to 

travel anteriorly out of the proximal walls during knee 

flexion.5 In our clinic we have witnessed the success of this 

socket design for users with recreational lifestyles 

performing activities such as cycling and hiking. More 

recently, the initial Söderberg socket 1.0 design presented 

in 2001 has been adjusted, and much of the rigid socket is 

now replaced with a flexible integrated proximal socket 

brim and trim line. It has been our clinical experience, that 

this additional removal of material when combined with 

elevated vacuum and a reduced trim line, elicits a greater 

range of knee motion, protects the suspension sleeve from 

breaking and can afford a shorter residual limb these same 

benefits.  

It was the purpose of this technical note to reintroduce an 

updated version of the Söderberg socket design and 

provide preliminary patient feedback. We questioned 

whether these updates would be viewed as a useful 

benefit to a patient with a desire for more range of motion. 

METHODOLOGY 

The patient for the Söderberg 2.0 socket is typically a 

transtibial amputee with a desire for enhanced range of 

motion during sitting, squatting or cycling or for aesthetic 

reasons during sitting. Patients with a short transtibial 

residual limb can also potentially benefit from the elevated 

flexible brim for better suspension. Often times the user is 

already wearing an endoskeletal modular prosthesis with 

liner and sleeve aided passive suspension.  

One active male participant was recruited (65 years, 

180cm, 87kg) K3 functional level,6 with residual limb length 

of 29cm mid-patella tendon to distal end of residual limb. 

The cause of amputation was trauma at age 55 and prior 

prosthesis socket and experience was with a pin lock 

suspension, total surface bearing style prosthesis, 

endoskeletal design and dynamic response foot. This 

patient had previously expressed a dislike of traditional 

socket trim lines, especially during daily trail cycling. 

Without objection, he agreed to volunteer for custom fitting 

of the Söderberg 2.0 socket. This single case record was 

granted approval through policies of the ethical committee 

at the Faculty of Medicine, Siriraj Hospital, Mahidol 

University. Our sampling method for this particular study 

was a convenience sample, and the participant was 

recruited from our clinic by word of mouth. As the 

participant was a healthy ambulator with a high functional 

level and a unique need, he was recruited for the study. 

Moreover, the patient had no other underlying health 

conditions or activity restrictions which would exclude 

them from participation. 

Casting and rectification 

The patient first donned a Simplicity tapered PUR liner 

(Otto Bock, Germany), the residuum was covered with 

protective wrap and bony landmarks were drawn with an 

indelible marker. The medial and lateral femoral 

epicondyles were marked, and a trim line across the 

proximal limb was drawn. An outline of the tibia and fibular 

head was defined, and any anatomical points of interest 

were noted for later rectification. The prosthetist performed 

a routine evaluation of the patient and created a Plaster of 

Paris positive cast of the residual limb using a total surface 

bearing (TSB) technique. We recommend to extend the 

proximal trim lines of the cast well over the condyles (3-

5cm) as these higher than traditional trim lines provide 

landmarks which can later be identified during rectification. 

A two-stage cast was created, firstly, an anterior slab was 

made to capture the head of the fibula, patella and tibial 

crest in 30 of knee flexion. This initial flexion permits 

easier definition of the anatomy of the tibia and patella 

tendon. Secondly, a circumferential plaster wrap was 

provided to encapsulate limb volume, posterior wall, and 

the entirety of the limb was cast in 10-20 knee flexion. 

These varying casting angles are based off of experience 

and are modifications of previously established stage 

casting methods. Flexion in the first stage allows for 

capturing the bony aspects of the limb.7 During the second 

stage of casting it also important to capture the remaining 

residual muscle activity by asking the patient to contract 

and relax numerous times. Cast rectification was then 

performed using traditional principles of the TSB 

prosthesis with PUR liner.8 A sketch, as well as illustration 

of the Söderberg socket trim lines is provided in order to 

give a better understanding of the socket concept in Figure 

1 and Figure 2. 

Figure 1: Illustration demonstrating femoral movement within the 

Söderberg socket.5 

Fabrication and fitting  

Diagnostic (clear check socket) prosthesis fabrication was 

manufactured using a 12mm thick Northplex square sheet 

(North Sea Plastics Ltd, Glasgow, Scotland). The socket 

was aligned using modular componentry, a one-way 

expulsion valve was added to the socket and patient was 

fit with VAS, knee sleeve, and a PUR liner (Otto Bock, 

Germany) to create vacuum suspension. This suspension 

was selected based on the need for an improved 

connection between the residual limb and socket, to 

reduce volume fluctuations,9 and because of the socket’s 

less rigid trim lines.10 Typical below knee socket designs 

are higher along the lateral and medial aspects in order to 

provide medial lateral support around the condyles. The 

anterior trim line runs along the mid-patella region or 

slightly below as to not restrict movement.  Posteriorly, the 

https://doi.org/10.33137/cpoj.v2i2.33505


 

 

Söderberg B, Guerra G, Fagerstrom T, Permpool K, Phaipool S. The Söderberg socket 2.0: A technical note. Canadian Prosthetics & Orthotics Journal. 2019;Volume2, Issue2, 
No.3. https://doi.org/10.33137/cpoj.v2i2.33505  

 

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Söderberg et al. 2019 

 THE SÖDERBERG SOCKET 2.0 

trim line allows both hamstring tendons to move freely and 

travels slightly proximal to the posterior compartment. The 

previous Söderberg design trim lines did not have the 

added advantage of a flexible proximal brim. At this stage, 

the patient donned the check socket and trim lines were 

evaluated and trimmed to provide maximum medio-lateral 

and rotational stability as well as comfort according to the 

Söderberg 1.0 trim line.5 Each patient will present with 

individual needs, however, we recommend reducing trim 

lines on the rigid socket approximately 1-2cm. The patient 

ambulated and was evaluated to confirm socket fit, 

alignment and patient comfort. The check socket will allow 

for minor adjustments, though this was not required in this 

patient. Finally, a new circular cast was performed with the 

patient wearing the check socket to capture the proximal 

portion of the knee. The check socket, now with extended 

plaster cast, was filled with plaster and rectified into an 

updated model. 

Figure 2: Images illustrating the anterior, 45° anterior, posterior 

view as well as lateral views of the SOL style positive plaster 

model. Where (A) indicates trim lines for supracondylar 

suspension, (B) trim line for a PTB type socket with cuff 

suspension, and (C) trim line for a Söderberg type socket. 

 

The definitive fabrication was split into two processes; the 

first being the fabrication of the proximal brim and the 

second being creation of the distal definitive socket. To do 

so, an antibacterial ethylene-vinyl-acetate (EVA) material 

(Agruquero, Madrid, Spain) was formed over the proximal 

part of the updated positive model. This material self-

adheres well and leaves no seams after joining. The oven 

setting temperature for this material was 140º Celsius for 

10 minutes and model set time was 20 minutes.  After the 

brim was set, it was removed and trimmed to a proper 

thickness and skived down along the distal areas to allow 

for a good integration between the layers of carbon fiber. 

Upon completion of the proximal brim, a second process 

occurred to create the distal portion of the definitive socket. 

The distal portion was made from multiple layers of pre-

impregnated with resin (Prepreg) carbon fiber. The 

pregreg carbon fiber must be stored at a temperature of  -

20°C prior to curing. Storing the material at this 

temperature extends the life of the material to about one 

year.11  

Preparation of the positive model for the Prepreg requires 

removal of the proximal brim. A PVA bag is then drawn 

over the model in the same method as in traditional resin 

lamination. Prepreg strips were then individually adhered 

onto the model, layer by layer, whilst controlling fiber 

directions to achieve the desired design and strength. A 

total of 4 layers of carbon fiber were then wrapped 

circumferentially in an evenly distributed manner.  The 

proximal brim was then placed back onto the model and 

finally an additional 4 layers of Prepreg were wrapped 

along the brim transition point. This sandwiching allows 

flexibility of the proximal portion of the socket. The 

transition from the EVA to the carbon fiber will show no 

ridges as this EVA material adheres to the prepreg carbon 

fiber in the definitive socket uniformly. Moreover, a one-

way expulsion valve was placed between the model, 

Prepreg and distal socket adapter. A second PVA bag was 

then applied to enable vacuum suction during curing. The 

socket was then placed in an oven overnight for curing per 

Prepreg manufacturer recommendations (Figure 3). 

Initial cutting and trimming of the socket were performed 

after the device was assembled. The patient donned the 

device and flexible proximal trim lines as well as alignment 

were assessed and adjustments made. Trim lines were 

trimmed to permit full range of motion during the clinic visit. 

The patient returned to daily activities, and over the course 

of a year, was asked to return to his typical cycling, hiking 

and rock-climbing activities and to informally record  

subjective feedback with respects to range of motion, 

stability and comfort. The patient returned to living abroad, 

and subjective feedback from the patient was evaluated in 

person at the clinic a year later. 

RESULTS  

The new Söderberg 2.0 socket technical achievement is in 

its ability to blend two different materials together in a 

socket which enhanced user function. Subjective feedback 

was received from the patient in person at the clinic. 

Although terse, feedback was noteworthy and useful, with 

the patient describing his cycling and daily activities as 

“enhanced and without restriction in the knee”. The user 

expressed that they were able to cycle as often as they 

wished and do so without any discomfort or restriction of 

motion. On a side note, he also reported that the silicone 

knee sleeve had lasted longer than with his previous 

sockets. Ta 

DISCUSSION  

This technical note explored a new socket design using a 

combination of materials that improved both range of 

motion and comfort for the transtibial prosthesis user. Our 

technical achievements were seen in the ability to 

seamlessly integrate two new materials together in a 

single rigid-flexible socket design. This technique proved 

beneficial for the patient during activities of daily living.  

https://doi.org/10.33137/cpoj.v2i2.33505


 

 

Söderberg B, Guerra G, Fagerstrom T, Permpool K, Phaipool S. The Söderberg socket 2.0: A technical note. Canadian Prosthetics & Orthotics Journal. 2019;Volume2, Issue2, 
No.3. https://doi.org/10.33137/cpoj.v2i2.33505  

 

4 

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Söderberg et al. 2019 

 THE SÖDERBERG SOCKET 2.0 

Figure 3: Images illustrating the (a) proximal brim over the first 

layer of prepreg carbon fiber, (b) trimmed version with second 

layer of prepreg carbon fiber applied and (c) final socket after 

curing. 

The previous Söderberg socket design does not provide 

the user with the superior proximal socket comfort and 

sleeve protection offered in the current socket style. The 

patient noting increased lifespan of the liner was most 

likely due to the flexible brim reducing strain on the sleeve, 

whereas a regular hard socket brim might not have been 

able to do so. Although, outside of the purview of this 

technical note, a more robust set of research outcome 

measurements and comparison between traditional 

sockets could provide further insight. Due to a small 

sample size, care should be taken not to generalize 

current findings. In addition, this user’s residual limb length 

was longer than average which might have affected his 

feedback of the device.  In Figure 4, we provide an image 

of the patient fit with the Söderberg 2.0 prosthesis. 

A potential caveat of this socket design is the requirement 

of costly Prepreg technology, however, this material is 

critical because of the rigid socket’s seamless interweave 

of the EVA flexible brim. Prepreg carbon fiber is widely 

used in P&O clinics and we believe that this technical note 

demonstrates a new option in manufacturing of prosthetic 

sockets that can further improve quality of life for the user. 

The positive subjective results provided by the patient, 

encourages us to further evaluate the technique and 

hopefully, with future clinical studies, the Söderberg 2.0 

socket design will add to available options for the 

transtibial prosthesis user.   

 

Figure 4: Image of the patient wearing the Söderberg 2.0 

prosthesis. 

ACKNOWLEDGEMENTS 

We wish to thank the patient for his assistance in this technical 

note. 

DECLARATION OF CONFLICTING 

INTERESTS 

The authors have no conflicts of interest to declare. 

ETHICAL APPROVAL 

This single case record was granted approval through policies of 

the ethical committee at the Faculty of Medicine, Siriraj Hospital, 

Mahidol University. 

AUTHOR CONTRIBUTION 

• Bengt Söderberg,  

conceived the idea for the project, supported technical 

aspects and contributed to the writing of the manuscript  

• Teddy Fagerstrom,  

conceived the idea for the project, supported technical 

aspects and assisted in the writing of the manuscript  

• Gary Guerra,  

supported the technical aspects and contributed to the writing 

of the manuscript  

A B 

C 

https://doi.org/10.33137/cpoj.v2i2.33505


 

 

Söderberg B, Guerra G, Fagerstrom T, Permpool K, Phaipool S. The Söderberg socket 2.0: A technical note. Canadian Prosthetics & Orthotics Journal. 2019;Volume2, Issue2, 
No.3. https://doi.org/10.33137/cpoj.v2i2.33505  

 

5 

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Söderberg et al. 2019 

 THE SÖDERBERG SOCKET 2.0 

• Kwannate Permpool,  

supported the technical aspects and contributed to the writing 

of the manuscript 

• Sarawanee Phaipool, 

supported the technical aspects and contributed to the writing 

of the manuscript  

SOURCES OF SUPPORT 

The authors received no financial support or assistance for this 

research.  

 

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https://doi.org/10.33137/cpoj.v2i2.33505
http://dx.doi.org/10.1682/JRRD.2014.08.0184
https://doi.org/10.21300/18.2-3.2016.167
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