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VOLUME 4, ISSUE 2  
 2021 

 

STAKEHOLDER  PERSPECTIVES 

Klenow TD, Schulz J. Adjustable-volume prosthetic sockets: market overview and value propositions. Canadian Prosthetics & Orthotics Journal. 2021; Volume 

4, Issue 2, No.17. https://doi.org/10.33137/cpoj.v4i2.35208 

This article has been invited and reviewed by Co-Editor-In-Chief, Dr. Silvia Ursula Raschke. 
English proofread by: Karin Ryan, M.A., B.Sc., P.T.   
Managing Editor: Dr. Hossein Gholizadeh 
 

SPECIAL ISSUE 

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Klenow TD, Schulz J. Adjustable-volume prosthetic sockets: market overview and value propositions. Canadian Prosthetics & Orthotics Journal. 2021; Volume 4, 
Issue 2, No.17. https://doi.org/10.33137/cpoj.v4i2.35208 

 

 

 
STAKEHOLDER  PERSPECTIVES 

 

ADJUSTABLE-VOLUME PROSTHETIC SOCKETS: MARKET OVERVIEW AND VALUE 

PROPOSITIONS 

Klenow TD.1 *, Schulz J.2 
 

1 Martin Bionics Clinical Care, Fort Myers, Florida, USA. 
2 Martin Bionics Innovations, Oklahoma City, Oklahoma, USA. 

 

 

 

 

  

 

 

 

 

 

 

 

 

 

 

 

 

 

 

INTRODUCTION 

The human-device interface, referred to clinically as the 

socket, is commonly considered to be the most important 

part  of  a  prosthesis.1-6
  It  is  also  the  most  problematic,  

 

 

 

 

 

 

 

 

 

 

however, as lack of socket fit is a commonly reported issue 

among end-users.5 Since the socket is the only custom-

fabricated part of the prosthesis, it’s replacement represents 

the largest time commitment to the patient.1,7
 Approximately 

90% of amputations occur secondary to diabetes and 

vascular disorders which leads to complex clinical 

presentations in much of the population.4,8 Vascular 

compromise amplifies fluid retention difficulties and even 

small changes in limb volume can lead to socket fit issues.9 

 
OPEN  ACCESS Volume 4, Issue 2, Article No.17. 2021 

 

 

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

 

ABSTRACT 

The prosthetic socket is commonly considered to be the most important part of the prosthesis and lack 

of fit can lead to skin breakdown, reduction in wear, reduction in activity, and consequential deleterious 

health effects. Furthermore, approximately 90% of amputations are due to a vascular etiology, which 

affect fluid retention regularity, and even small limb volume fluctuations can lead to lack of fit. Adjustability 

in the socket volume has been suggested as a potential solution to common fit issues but has lacked 

market penetration mostly due to lack of reimbursement. Despite this there are several adjustable-volume 

sockets emerging on the market today including prefabricated, modular, custom with adjustable-volume 

component, custom with adjustable-volume feature, and adjustable-hybrid sockets. Prefabricated 

sockets are mass produced in common sizes and fit directly to the patient by a prosthetist using pad kits, 

BOA dials, or straps. Modular sockets are assembled to a patient or model with panels or struts attached 

to an adjustable base. Custom sockets with adjustable-volume elements are traditionally-fabricated 

sockets made to a model of a patient’s limb with a volume-adjustable component added or volume-

adjustable feature built in. Custom-hybrid sockets are made custom to a model of the patient’s limb and 

incorporate several aspects of the previous socket types and include some radically-unique design 

aspects which cannot be limited to one category. These adjustable-volume sockets offer several 

advantages to traditional rigid-volume sockets for the patient, prosthetist, and providing clinic. The micro-

adjustability for the patient allows them to alter fit without removing the socket, maintaining a more 

intimate fit throughout the day than traditional sockets. The macro-adjustability for the prosthetist allows 

for increased options for fit customization including the ability to reverse or undo changes without 

necessarily re-making the socket. This allows for the most optimal fit for the patient. Adjustable volume 

also present efficiencies in the fitting process by simplifying or eliminating steps including residual limb 

shape capture, form modification, diagnostic fabrication, iterative alteration, and definitive fabrication with 

the different socket types affecting different steps. Due to these factors, adjustable-volume sockets have 

disrupted the market to the point where reimbursement reform is needed including additional L-codes in 

the United States and fee-for-service or fee-for-outcome associated with prosthetic follow-up care. 

Prosthetic care should also be separated from durable medical equipment to allow for alternative 

reimbursement models. As reimbursement adapts prosthetists must adapt correspondingly to 

differentiate their skillset from other allied health providers including incorporating more objective 

methods to show superior care outcomes. This adaptation should include a continued push for state and 

municipal licensure of prosthetists.  

CITATION 

Klenow TD, Schulz J. Adjustable-

volume prosthetic sockets: 

market overview and value 

propositions. Canadian 

Prosthetics & Orthotics Journal. 

2021; Volume 4, Issue 2, No.17 

https://doi.org/10.33137/cpoj.v4i2.

35208 

KEYWORDS 

Innovation, Interface, Amputation, 

Limb Loss, Rehabilitation, 

Modular, Prosthetic Sockets, 

Prosthetics, Medical Equipment 

 

 

* CORRESPONDING AUTHOR 

Tyler D. Klenow, MSPO, MBA, CLPO, FAAOP 

Martin Bionics Clinical Care 

E-Mail: Tyler.klenow@martinbionics.com 

ORCID ID: https://orcid.org/0000-0002-6372-2241 

Special Issue: Health Economics in Prosthetics & Orthotics 

https://doi.org/10.33137/cpoj.v4i2.35208
https://jps.library.utoronto.ca/index.php/cpoj/index
https://doi.org/10.33137/cpoj.v4i2.35208
https://doi.org/10.33137/cpoj.v4i2.35208
mailto:Tyler.klenow@martinbionics.com
https://orcid.org/0000-0002-6372-2241


 

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Klenow TD, Schulz J. Adjustable-volume prosthetic sockets: market overview and value propositions. Canadian Prosthetics & Orthotics Journal. 2021; Volume 4, 
Issue 2, No.17. https://doi.org/10.33137/cpoj.v4i2.35208 

ISSN: 2561-987X 
ADJUSTABLE-VOLUME PROSTHETIC SOCKETS  

Klenow & Schulz. 2021 CPOJ 

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Lack of socket fit can lead to pain, discomfort, skin irritation 

and breakdown, subsequent prosthetic abandonment, and 

therefore activity reduction, reduced social participation, 

psychosocial problems, and deleterious health effects due 

to inactivity.2-8 Further, only 50% of individuals with 

amputation receive a prosthesis initially and 11-22% of 

patients abandon their prosthesis at one year.10 Re-

amputation and mortality rates surrounding amputation also 

remain remarkably high thereafter.4,11 

These pervasive issues, described above, among the 

patient population have stimulated several innovations in 

interface design over the past decade.5,9 A notable 

innovation is the introduction of additive manufacturing, or 

3D-printing, to prosthetic socket fabrication.12 3D-printed 

sockets offer an improved array of material selection, 

textured finishes, and elasticity. They also offer new design 

elements as wall thicknesses can be increased in areas 

where more structural support is required and decreased 

where more flexibility is desired. With all the benefits 

inherent in 3D-printed sockets, they still rely on traditional 

methods to accommodate residual limb volume changes.8,9 

Therefore, additive manufacturing alone does not 

adequately address residual limb fluid dynamics and 

associated socket fit issues over time. 

Adjustable sockets are designed as an innovation to provide 

on-demand micro-adjustability to the patient and/or macro-

adjustability to the prosthetist. Micro-adjustability is a socket 

feature which allows the patient to accommodate diurnal 

residual limb volume fluctuation without needing to remove 

the socket to implement a traditional volume management 

strategy. Macro-adjustability is a socket feature which 

allows the prosthetist to accommodate large physiological 

changes without necessarily replacing the entire socket or 

modifying the physical socket structure. Adjustability has 

been stated as a desire for patients and as a potential 

solution to socket fit issues for several years, but market 

penetration for adjustable sockets in clinical prosthetics has 

been limited primarily due to lack of reimbursement.2 

Adjustable-volume sockets present increased options for 

customization to the patient, present efficiencies during the 

fitting process, and allow for prolonged maintenance of fit 

compared to rigid-volume sockets.13 While there are several 

types of adjustable-volume sockets available on the market 

they are commonly omitted from literature reviews on socket 

design categorically.2,3,14,15 Therefore, the purpose of this 

article is to provide a market overview of adjustable-volume 

sockets and present their value proposition for end-users 

and potential providing clinics. 

MARKET OVERVIEW 

There are three major categories of adjustable-volume 

sockets available on the market today: prefabricated, 

modular, and custom sockets with adjustable elements 

(Figure 1). Prefabricated sockets are ordered by generic 

size from a supplier and individually fit to the patient by a 

skilled practitioner. These sockets must be individualized 

and fit in real-time with the patient and must be trimmed, 

bent, molded (with or without heat), padded, or otherwise 

modified resulting in alterations beyond minimal self-

adjustment. Prefabricated sockets are often bivalve in 

design and utilize an adjustable closure mechanism such as 

a cable and dial, toggle latch, ratchet straps, hook and loop 

Velcro, or similar derivative. These sockets often 

incorporate locking or anatomical suspension. They may or 

may not have additional adjustable elements. Notable 

prefabricated sockets include the Varos socket from 

Ottobock [Duderstadt, Germany], Connect® TF from Össur 

[Reykjavic, Iceland], and the iFit Prosthetics [Pewaukee, 

WI, USA] system. 

 

Figure 1: Examples of prefabricated, modular, custom with 

adjustable element, and custom-hybrid adjustable-volume sockets. 

Left to Right: Ottobock Varos, LIM Innovations Infinite TF, Click 

Medical RevoFit, Martin Bionics Socket-less Socket. 

Modular sockets are ordered as a set of several 

prefabricated parts and assembled directly to the patient or 

a model of the patient’s limb by a skilled practitioner. The 

process typically includes affixing generically-sized struts or 

panels to a common base with many possible configuration 

options. The struts or panels must be trimmed, bent, molded 

(with or without heat), or otherwise modified resulting in 

alterations beyond minimal self-adjustment to achieve an 

individual fit for the patient. Circumferential pressure and 

biomechanical control are then attained through some 

adjustable closure mechanism including ratchet straps, 

hook and loop Velcro, or similar derivative. They often use 

locking suspension but can be suspended via suction in 

some arrangements. The most notable modular system was 

the Infinite Socket™ line by LIM Innovations [San 

Francisco, CA, USA].5 

The third form of adjustable sockets are custom sockets 

with adjustable elements. These fully-laminated sockets are 

fit to a model of a patient’s limb with one or more adjustable 

elements added or fabricated in. These can include 

integrated adjustable features such as the tensioning cable 

with floating panel or ratchet straps which apply or release 

pressure to a cut-out or flexible portion of the socket. 

Addition of these adjustable socket features requires 

alterations in socket fabrication or disruption to the 

https://doi.org/10.33137/cpoj.v4i2.35208
https://shop.ottobock.us/Prosthetics/Lower-Limb-Prosthetics/Socket-Technologies-Liners/Varos/p/5A60~5R-M
https://www.ossur.com/en-us/prosthetics/sockets/connect-tf
https://www.ifitprosthetics.com/
https://shop.ottobock.us/Prosthetics/Lower-Limb-Prosthetics/Socket-Technologies-Liners/Varos/p/5A60~5R-M
https://www.liminnovations.com/
https://clickmedical.co/
https://clickmedical.co/
https://martinbionics.com/


 

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Klenow TD, Schulz J. Adjustable-volume prosthetic sockets: market overview and value propositions. Canadian Prosthetics & Orthotics Journal. 2021; Volume 4, 
Issue 2, No.17. https://doi.org/10.33137/cpoj.v4i2.35208 

ISSN: 2561-987X 
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traditional physical structure of sockets. Notable adjustable 

socket features are the RevoFit™ by Click Medical 

[Steamboat Springs, CO, USA] and Quatro™ socket by 

Quorum Prosthetics [Windsor, CO, USA].5 Adjustable 

components are separately manufactured items added to 

the custom socket following the fitting process, or which 

alter the process only slightly. These components include 

air or fluid bladders such as the former Simbex [Lebanon, 

NH, USA] Active Contact System or Prosthetic Concepts 

[Little Rock, AR, USA] Pneu-fit™ system.9 

An additional form of adjustable-volume socket, the custom-

hybrid adjustable socket, contains major attributes of the 

previous three types. Custom-hybrid sockets differentiate 

themselves, - as they utilize some other radically-unique 

design aspects to provide micro-adjustability to the patient 

and macro-adjustability to the prosthetist. These sockets 

are justly custom as they can only be fabricated from a 

model of the patient’s residual limb. They are hallmarked by 

removal of large portions of the conventional custom-

laminated socket and replacement of foundational, key 

socket elements with truly flexible materials. Custom-hybrid 

designs alter traditional mechanical properties of rigid 

frames and flexible inner sockets in exchange for increased 

customization, flexibility, and adjustability. These 

adjustability options are presented both during and after the 

initial fitting process. The most notable custom-hybrid 

adjustable systems include the Socket-less™ Socket 

system by Martin Bionics [Oklahoma City, OK, USA] and the 

Sail socket by CJ Socket Technologies [Beverly, MA, 

USA].5 

The Martin Bionics Socket-less Socket™ system replaces 

most of the conventional, rigid-volume socket with 

conforming materials which contour to the residual limb, 

providing a hammock-like fit. The inner socket is replaced 

with custom-configurable parts consisting of flexible, 

injection-molded plastic straps, adjustable webbing straps, 

thermoplastic and metal struts, and micro-adjustable 

closure mechanisms. These parts can be assembled in 

combination with each other to create a customized fit. The 

unique design of the Socket-less Socket™ allows for 

numerous configuration options for a wide variety of patient 

and limb types enabling macro-adjustability by the 

prosthetist and micro-adjustability by the patient. The Martin 

Bionics systems are available for all major amputation 

levels. All transfemoral (TF) applications utilize an 

adjustable SwingBrim™ which replaces the conventional 

rigid brim with a webbing-based conforming brim, thereby 

eliminating rigid contact at the ischial seat. A version called 

the Bikini Socket™, which utilizes Martin Bionics’ Iliac Crest 

Stabilizers™ and ratchet closures, also exists for hip 

disarticulation and hemipelvectomy levels. The Socket-

less™ designs have many ancillary benefits reported by 

Martin Bionics including improved comfort, breathability, 

range of motion, restored muscular activation in the residual 

limb, and reduced heat retention compared to rigid-volume 

sockets. 

Another custom-hybrid adjustable system is the CJ Sail 

Socket. This system replaces the traditional flexible inner 

socket with a textile Sail piece which has integrated Velcro 

closures. The sail is typically affixed to one side of a custom 

socket shell with rivets and the adjustable straps attach to 

the other side with chafes. The Sail socket is available for 

most major amputations levels and the TF systems are 

mostly sub-ischial. 

VALUE PROPOSITION 

• End-Users 

Adjustable-volume sockets are designed to accommodate 

a larger range of residual limb volumes from baseline than 

rigid-volume sockets.13 The solution to diurnal volume 

fluctuation in most traditional systems, which is typically in 

the form of limb volume loss with prolonged daily wear, is to 

add prosthetic socks to fill the resultant voids.8,9 This 

requires the user to fully remove the prosthesis which is 

inconvenient at best. This may occur several times daily 

resulting in substantial time lost. On the other hand, patients 

will often avoid going through the process of doffing the 

prosthesis to change socks to save time and convenience. 

This doffing avoidance exacerbates fit issues and can 

cause damage to the residual limb over time. 

Options are more limited in rigid-volume sockets when the 

volume of the residual limb increases due to edema, weight 

gain, or some other physiological factor.16 Systems with a 

flexible inner socket and rigid frame can allow for the flexible 

inner socket to be removed to reveal an increased socket 

volume.17 Patients then add socks, or prosthetists can add 

pads, to restore fit intimacy. This situation is considered 

suboptimal, as the benefits of the flexible inner socket are 

lost and socket design is compromised, unless previously 

anticipated. Further, sockets are not always fabricated with 

a flexible inner socket or one that can be removed. 

Since the volume accommodation strategies of adjustable-

volume sockets are easier for the patient to make, typically 

through clothing or discretely, they are more likely to be 

implemented. This can lead to longer durations of optimal 

fit, increased wear time, and increased physical activity. 

Increased wear leads to more stable limb volumes and 

accelerated maturation as well.8 This means adjustable-

volume sockets are not only able to accommodate residual 

limbs with frequent volume changes but may also reduce 

volume fluctuation over time. Therefore, adjustable-volume 

sockets present an opportunity for a short-term and long-

term solution to volume fluctuation. Independently of this 

effect, adjustable-volume systems provide a potential 

solution to long-term volume fluctuation in that the socket 

volume can be adjusted to the user through adjustment of 

components or features without necessarily fabricating a 

new socket. Therefore, the patient would not have to commit 

to the time required for a replacement socket fitting and 

would reduce costs through reduced payments or co-

insurance. 

 

https://doi.org/10.33137/cpoj.v4i2.35208
https://clickmedical.co/
https://opquorum.com/programs/


 

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Klenow TD, Schulz J. Adjustable-volume prosthetic sockets: market overview and value propositions. Canadian Prosthetics & Orthotics Journal. 2021; Volume 4, 
Issue 2, No.17. https://doi.org/10.33137/cpoj.v4i2.35208 

ISSN: 2561-987X 
ADJUSTABLE-VOLUME PROSTHETIC SOCKETS  

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• Clinics 

Rigid-volume sockets are currently fit through some form of 

residual limb shape capture, form modification, diagnostic 

fabrication, iterative alteration, and definitive fabrication 

(Figure 2).18 The shape capture portion is mainly 

accomplished through hand-casting -using plaster or 

fiberglass bandage, as well as three-dimensional scanning. 

Modification of the captured shape is accomplished 

manually to a physical model or digitally using a computer-

aided design (CAD) program and are often standardized. 

Diagnostic fabrication includes creation and application of a 

clear plastic socket, commonly PETG, to the patient’s 

residual limb to inspect fit and allow alterations.4 These 

alterations are made in an iterative fashion, sometimes with 

multiple check sockets, until a satisfactory fit is achieved. A 

definitive socket is then fabricated from the resultant form. 

Definitive sockets are designed for long-term use, with 

fewer options for alterations compared to the diagnostic 

sockets. 

While this fabrication process is commonplace, rigid-volume 

sockets are inherently limited with some alterations being 

exceedingly difficult, time-consuming, or impossible to 

make through the various modification techniques and each 

having their associated costs. Some alterations are 

impossible to reverse once made, requiring the socket to be 

remade altogether. Therefore, the patient and practitioner 

are unavoidably presented with the decision to make the 

alteration or not. This results in a sub-optimal situation for 

both parties involved to achieve the best socket fit possible. 

Further, third-party payers often limit the quantity and 

frequency at which new sockets can be reimbursed. The 

reimbursement for periodic replacement of sockets often 

constitutes a significant percentage or majority of a 

prosthetic clinic’s revenue stream. 

Adjustable-volume sockets create efficiencies in - the fitting 

process by eliminating or simplifying steps. Prefabricated 

sockets are manufactured in mass quantities to create an 

economy of scale for the manufacturer. They are loosely 

designed around traditional socket designs and present one 

or several options for custom-fitting by the skilled 

practitioner. These options include pad kits, adjustable 

cables, and air bladders, while also enabling trimming and 

heat-molding.13 Prefabricated sockets eliminate the 

modification step and definitive fabrication portions of the 

process while simplifying diagnostic fabrication and iterative 

alteration into configuration of macro-adjustable elements in 

real-time with the patient. Shape capture is simplified to 

measurement for accurate size order. Prefabricated sockets 

present reasonable fit options to a majority of amputees who 

present with standard residual limb anatomy. 

Biomechanical control is a topic of debate with prefabricated 

sockets as associated transtibial (TT) designs implement 

pre-tibial pads to offload bony prominences and the TF 

designs are mostly sub-ischial in nature. 

Modular sockets seek to create similar efficiencies in fitting 

by eliminating modification and simplifying diagnostic and 

definitive fabrication into assembly of prefabricated 

modules. An economy of scale can be realized in mass 

production of these modules similar to prefabricated 

sockets. Modular sockets present some advantages over 

rigid-volume sockets regarding customization as elements 

can be placed in direct response to residual limb anatomy 

and biomechanics. Many of the modules are themselves 

heat adjustable and can be individually customized in this 

way as well. Diagnostic sockets are sometimes used for 

TRADITIONAL 

Shape Capture

Measurements

Iterative adjustment

Real-time adjustment 
on patient

Delivery

Patient accepts 
definitive device

Shape Capture

Casting, 
measurements

Assembly

Prefabricated 
parts

Iterative adjustment

Real-time adjustment of 
modular elements

Delivery

Patient accepts 
definitive device

Shape Capture

Casting, measurements

Modification

Standard or 
Reduced set

Diagnostic fitting

Check socket

Iterative adjustment

Real-time 
adjustments of 

elements

Definitive fabrication

Laminate rigid socket

Delivery

Patient accepts 
definitive device

CUSTOM - ADJUSTABLE 

Shape Capture

Casting, measurements

Modification

Standard set

Diagnostic fitting

Check socket

Iterative adjustment

Heat-mold, cut down, 
pads, socks, etc.

Definitive fabrication

Laminate rigid socket

Delivery

Patient accepts 
definitive device

MODULAR 

PREFABRICATED 

Figure 2: Socket Fitting Processes. 

https://doi.org/10.33137/cpoj.v4i2.35208


 

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Klenow TD, Schulz J. Adjustable-volume prosthetic sockets: market overview and value propositions. Canadian Prosthetics & Orthotics Journal. 2021; Volume 4, 
Issue 2, No.17. https://doi.org/10.33137/cpoj.v4i2.35208 

ISSN: 2561-987X 
ADJUSTABLE-VOLUME PROSTHETIC SOCKETS  

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offsite fabrication of these systems but are not always 

required. Modules often include component attachment 

blocks, struts, panels, and some circumferential binding 

element. Upper extremity designs can include cuffs and TF 

designs often implement a telescoping ischial seat 

module.16,19 These systems typically, but not always, 

include a micro-adjustable element. 

Custom sockets with adjustable elements are varied in their 

fitting efficiencies. Many of the benefits with these systems 

come in the form of the aforementioned daily micro-

adjustability for the patient. In custom sockets with 

integrated adjustable features, such as the cable/panel 

type, more fabrication time and labor are often required at 

the outset. With the RevoFit™ and Quatro™ systems, for 

example, the same standard fabrication techniques are 

required in addition to the feature installation.5 The 

increased socket fit range these systems present, however, 

may potentially reduce the number of diagnostic fitting and 

iterative changes required as they present additional 

options for customization and biomechanical control 

depending on application. Reduced number of follow-up 

appointments are often marketed by the system 

manufacturers. Custom sockets with adjustable 

components alter fabrication only slightly or not at all, but 

also present those options for adjustability in real-time with 

the patient.9   

Custom-hybrid adjustable systems with multiple macro- and 

micro-adjustable attributes also present mixed efficiencies 

in fitting and follow-up.5 The Socket-less™ Socket systems 

by Martin Bionics simplify or eliminate several steps of the 

fabrication process including in shape capture, modification, 

and iterative alteration. Initial diagnostic and definitive 

fabrication are slightly prolonged by the additional assembly 

time needed to finish the increased topographical length of 

socket trimlines due to the many cut-outs, drilling holes to 

affix the Socket-less Socket™ components, and converting 

components from diagnostic to definitive.  The total number 

of fitting appointments is typically reduced since iterative 

alterations are made in real-time with the patient versus in 

the lab and need for additional check sockets is often 

reduced. Customization of the Socket-less Socket™ 

includes simply moving a Chicago-type thumb screw from 

one hole to another in the thermoplastic straps. So, 

significant adjustments or socket re-makes can be reduced 

to a matter of seconds. Additionally, the adjustable nature 

of these sockets and options for customization throughout 

the product life cycle could facilitate reduced overutilization 

costs per beneficiary thereby reducing overall cost to third-

party payers.   

Shape capture and modification are simplified with the 

Martin Bionics system since large portions of the laminated 

socket are eliminated. The TF version, for example, 

eliminates the need for high-definition shape capture of the 

pelvic anatomy and modification of the traditional brim due 

to integration of the SwingBrim™. One approach of the TF 

system includes replacement of the laminated lateral wall 

with metal bars to suspend the components, presenting an 

efficiency by limiting shape capture and modification further 

to the distal third of the residual limb. The iterative alteration 

step is simplified as the check socket no longer requires 

heat guns and grinders but utilizes the real-time 

adjustments through straps with thumb screws instead. The 

macro-adjustability of the systems allows for considerably 

more options for customization to the patient and, perhaps 

more profoundly, the ability to reverse a socket adjustment 

if it is ultimately deemed undesirable to the patient.  

The CJ sail socket is another custom-hybrid adjustable 

system. This system therefore presents efficiencies through 

simplification of the modification and iterative alteration 

steps of fabrication. Likewise, additional time may be 

required in diagnostic and definitive fabrication steps to 

prepare the socket and integrate the textile. Since the textile 

piece conforms to the patient’s residual limb shape though, 

the need for extensive form modifications are reduced. The 

sub-ischial TF version also reduces the amount of shape 

capture detail and modification needed at the ischial seat. 

Structural testing of the CJ sail socket and Martin Bionics 

systems have not been disseminated in the literature to 

date, so long-term maintenance requirements are unknown 

compared to rigid-volume sockets which are known for 

durability.  However, the major cause of socket replacement 

is from residual limb volume change and subsequent fit and 

discomfort issues which conforming and adjustable-volume 

sockets seek to resolve.  

CONCLUSION 

The purpose of this article is to provide a market overview 

for the subcategory of adjustable prosthetic sockets, their 

reported end-user benefits, and potential fitting process 

efficiencies. The subcategories of pre-fabricated, modular, 

and custom sockets with adjustable elements are identified. 

The custom sockets with adjustable elements subcategory 

is further delineated into addition of adjustable component 

or adjustable features. Custom-hybrid adjustable systems, 

which span all three major categories and have some other 

radically-unique design feature, are also presented. 

Adjustable sockets present opportunities for efficiencies 

through innovation of the various stages of fitting including 

shape capture, form modification, diagnostic fabrication, 

iterative alteration, and definitive fabrication. Long-term 

efficiencies are also created through reported reductions in 

follow-up time and overutilization. Adjustable sockets in 

their various forms are disruptive technologies, but likely 

represent a lasting innovation to the field of clinical 

prosthetics. 

CALL TO ACTION 

• Reimbursement Reform 

Adjustable-volume socket technologies have disrupted the 

traditional delivery model in clinical prosthetics and 

reimbursement reform is needed to ensure longevity and 

capitalization of the trend. Since the technology shifts the 

emphasis in fitting from skilled labor of fabrication to clinical 

expertise and long-term care, corresponding 

https://doi.org/10.33137/cpoj.v4i2.35208
https://cjsocket.com/


 

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Klenow TD, Schulz J. Adjustable-volume prosthetic sockets: market overview and value propositions. Canadian Prosthetics & Orthotics Journal. 2021; Volume 4, 
Issue 2, No.17. https://doi.org/10.33137/cpoj.v4i2.35208 

ISSN: 2561-987X 
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reimbursement items should be introduced. In the current 

fee-for-device delivery model this would manifest itself in 

the form of additional L-codes. In a hybridized model, 

allowances for clinical services not associated with initial 

delivery of the device should be implemented including 

evaluation, outcome measure collection, and long-term 

adjustment.20 In addition, the administrative burden for 

repair and replacement of minor parts billing should be 

reduced to encourage their use. These proposed reforms 

should ultimately reduce cost for third-party payers and the 

healthcare system overall through reduced costs per 

beneficiary resultant from reduced overutilization.  

The principles of these adjustable-volume systems also 

incorporate well into fee-for-outcome and fee-for-value 

models through the presented efficiencies and prospect of 

improved outcomes in the long-term. These reimbursement 

models have permeated allied health in other areas, but not 

durable medical equipment yet. Prosthetic services should 

be separated from DME in the policy of payers, as it is in the 

Uniform Glossary of Health Coverage and Medical Terms, 

establishing the field as its own independent specialty.21 

This would allow for simplified implementation of cost-

saving strategies apart from fee-for-device including fee-for-

outcome, bundled payments, and capitation. 

• Prosthetist Adaptations 

As innovation in the field of clinical prosthetics occurs and 

reimbursement models evolve in the current progressive 

healthcare climate, prosthetists must also advance care 

delivery systems. Currently, prosthetic prescription, fitting, 

and delivery relies heavily on the individual experience and 

expertise of the clinicians. However, the experience and 

educational background of these professionals is quite 

varied, reflecting the changing collective thought of the field 

at various points in time. If prosthetists are to set themselves 

apart from durable medical equipment suppliers, their 

associated skillset must also set itself apart. Since the 

patient population of prosthetic users is so unique, this 

skillset must include an unparalleled and self-evident 

expertise of the most unique aspect of the patient: the 

residual limb. Further acceptance of advanced assessment 

techniques, such as digital shape capture, activity 

monitoring, and physical performance outcome measures, 

is required. In addition, the field of prosthetics should 

continue and more earnestly push for licensure of its 

practitioners throughout the United States, Canada, and 

abroad. This will enable the true clinical independence, 

professional validation, and service-related reimbursement 

currently being sought. Other allied health professionals 

including physical therapists, occupational therapists, 

podiatrists, and audiologists have accomplished similar 

goals correspondingly. 

ACKNOWLEDGEMENTS 

None. 

DECLARATION OF CONFLICTING 

INTERESTS 

Tyler D. Klenow is an employee of Martin Bionics Clinical 

Care and Joel Schulz is an employee for Martin Bionics 

Innovations, the providers of the Socket-less™ Socket 

systems. 

SOURCES OF SUPPORT 

None. 

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Klenow TD, Schulz J. Adjustable-volume prosthetic sockets: market overview and value propositions. Canadian Prosthetics & Orthotics Journal. 2021; Volume 4, 
Issue 2, No.17. https://doi.org/10.33137/cpoj.v4i2.35208 

ISSN: 2561-987X 
ADJUSTABLE-VOLUME PROSTHETIC SOCKETS  

Klenow & Schulz. 2021 CPOJ 

Special  

 

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Available from:  https://www.healthcare.gov/SBC-GLOSSARY/. 

 

 

 

 

 

 

 

AUTHORS SCIENTIFIC BIOGRAPHY 

Tyler Klenow, MS, MBA, LCPO, 

FAAOP is a graduate of the 

Master of Science in Orthotics & 

Prosthetics program at Eastern 

Michigan University and the 

Master of Business Administration 

program in the Nathan M. Bisk 

School of Business at Florida 

Institute of Technology. He is 

currently the co-chair of the 

clinical education planning 

committee for the American 

Orthotic & Prosthetic Association 

(AOPA) and has previously 

served as the Chairman of the Outcomes Research Committee for 

the American Academy of Orthotists and Prosthetists. Tyler 

specializes in prosthetic research including outcome measures, 

biomechanics, and secondary knowledge. He joined Martin Bionics 

Clinical Care as a Program Manager and Clinic Leader in 2020.  

 

Joel Schulz, BA, BSPO, CLP is a 

graduate of the Prosthetics and 

Orthotics program at the 

University of Washington and has 

worked in several roles in the 

prosthetics industry over an 18-

year career. He worked on the 

The Defense Advanced Research 

Projects Agency (DARPA) 

Revolutionizing Prosthetics 2009 

Project with Johns Hopkins 

Applied Physics Laboratory while 

at Orthocare Innovations. Joel co-

developed a fabric-based 

exoskeletal jacket with the National Aeronautics and Space 

Administration Warrior Web program. He has experience in 

computer aided design (CAD), animatronics, prosthetic socket 

design, and has lectured for prosthetic manufacturers and training 

programs as well. He worked for the original Martin Bionics 

company in 2007 and joined Martin Bionics Innovations as a design 

engineer and research prosthetist in 2014. 

 

 

 

https://doi.org/10.33137/cpoj.v4i2.35208
https://issuu.com/americanoandp/docs/opn_spring_issuu_de9bd75400c720
https://issuu.com/americanoandp/docs/opn_spring_issuu_de9bd75400c720
https://www.healthcare.gov/SBC-GLOSSARY/

