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biomechanics

Oct 04
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The Role of a Prosthetic Expert in Complex Workers’ Compensation Cases

By Amputee, biomechanics, Expert witness, HiFi, Outcome Measures, Prosthetics, Research

Prosthetic Expert Witness Services in Amputation Litigation

In complex amputation litigation, particularly high-value workers’ compensation and catastrophic injury cases, the prosthetic system is often central to disputes regarding functional capacity, future care costs, and long-term disability. A qualified prosthetic expert provides objective analysis of the entire prosthetic system, including interface design, component selection, outcome measures, and long-term performance expectations. While advanced prosthetic components such as microprocessor knees and multi-articulating hands attract attention, long-term function depends on how the entire prosthetic system works together.

Evaluating the Entire Prosthetic System

A prosthetic expert does not evaluate one component in isolation.

Comprehensive system analysis includes:

• Residual limb anatomy and condition
• Socket and interface biomechanics
• Suspension method and rotational control
• Alignment and load transmission
• Component selection relative to patient activity level
• Objective outcome measures
• Replacement projections

This whole-system approach allows the court to understand whether reported limitations are inherent to the injury or influenced by prosthetic design variables.

The Prosthetic Interface: A Critical System Variable

The human–device interface remains a primary determinant of prosthetic success.

The socket functions as a load-transfer and control system. Subtle differences in interface design can affect:

• Skeletal stabilization and rotational control
• Pistoning and micromotion
• Tissue shear and skin integrity
• Neuroma irritation
• Energy expenditure 
• Fall risk and balance

However, interface performance must be considered in the broader context of the entire prosthetic system. Alignment errors, inappropriate component prescription, or poor suspension strategies can produce similar symptoms.

An experienced prosthetic expert distinguishes among these factors.

Beyond “Standard of Care”: Biomechanical Considerations

Traditional socket strategies often rely on global compression and contouring which are documented to cause issues and provide inadequate biomechanical control, potentially contributing to instability or limited wear tolerance.

Randall Alley, CP, developed the patented High-Fidelity (HiFi) Interface System to address skeletal stabilization using alternating zones of compression and tissue release. This work was tested during service as the lead interface consultant on DARPA’s LUKE Arm program under physician oversight and through a Direct-to-Phase II DARPA contract.

Research and clinical observations have shown that improved skeletal stabilization can enhance gait symmetry, reduce center-of-mass deviation, improve dynamic control and enhance wearer proprioception and feedback.

In litigation, the relevant question is not whether one system is superior in all cases — but whether the prosthetic system provided aligns with accepted clinical standards and was appropriate for the individual claimant.

Complementing Surgical Advances

Modern amputation care increasingly includes:

• Osseointegration
• Targeted muscle reinnervation (TMR)
• Regenerative peripheral nerve interfaces

These surgical procedures enhance biological and neural integration. Yet even advanced surgical techniques can benefit from external mechanical stabilization.  A prosthetic expert evaluates how surgical factors, prosthetic interface design, component prescription, and alignment interact within the total prosthetic system.

Objective Outcome Measures in Amputation Cases

Validated functional outcome tools commonly used in prosthetic evaluation include:

• Amputee Mobility Predictor (AMP)
• Timed Up and Go (TUG)
• Prosthesis Evaluation Questionnaire (PEQ)
• Gait symmetry and center-of-mass analyses

An expert experienced in outcome analysis can translate these data into understandable, nontechnical explanations for judges, juries, administrative law judges, and arbitration panels.

Life Care Planning and Economic Impact

Prosthetic system design directly affects long-term cost projections, including:

• Fall frequency and secondary injuries
• Need for assistive devices
• Socket replacement intervals
• Component upgrade frequency
• Residual limb health complications
• Return-to-work potential

An expert in prosthetics will work with a Life Care Planner to help determine economic implications while remaining grounded in objective standards.

What a Prosthetic Expert Witness Evaluates

In complex claims, a prosthetic expert evaluates:

Residual limb status
Soft tissue coverage, neuromas, scarring, volume management.

Interface design
Socket type, skeletal stabilization strategy, materials, trim lines, suspension.

Component prescription
Appropriateness of knee, foot, hand, or ankle technology relative to activity classification.

Alignment
Static and dynamic alignment relative to gait mechanics.

System integration
How interface, suspension, and components function together.

Future projections
Reasonableness of life care plans, refitting frequency, and technological upgrades.

The objective is clarity.

Experience Supporting Expert Testimony

Randall Alley is a board-certified prosthetist with over 35 years of experience in upper and lower limb prosthetics. He holds a BSc in Kinesiology and a Prosthetics Certificate from UCLA.

He has served as:

• CEO and Chief Prosthetist at biodesigns, inc. in Southern California 
• Lead interface consultant on DARPA’s LUKE Arm program
• Principal investigator on a Direct-to-Phase II DARPA contract
• Co-founder and former director of the world’s largest upper limb prosthetic program

He holds multiple patents related to prosthetic interface systems and has published in numerous textbooks.

This blend of clinical practice, research, and system design supports the evidentiary standards required in technical medical litigation.

When to Engage a Prosthetic Expert Witness

Engaging a prosthetic expert witness may be appropriate when:

• There is dispute regarding the adequacy of the prosthetic system provided.
• Functional complaints appear inconsistent with documented device specifications.
• Future care projections rely heavily on prosthetic replacement assumptions.
• Conflicting medical opinions exist regarding functional capacity and return-to-work potential.

Early, objective system evaluation can clarify whether outcomes reflect unavoidable impairment or modifiable prosthetic factors.

Independent Prosthetic System Evaluation for Litigation

Complex amputation cases require specialized knowledge of prosthetic system mechanics, interface stabilization, component selection, and outcome measurement. For attorneys representing plaintiff or defense, an independent prosthetic expert provides analysis grounded in clinical standards.

To request consultation or case review, contact biodesigns regarding expert witness services with Randall Alley, CP.

Jun 13
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Biotensegrity Bridge and How It Relates To Improved Outcomes in Prosthetic Socket – Interface Design

By AK, Amputee, Articles, Biodesigns, biomechanics, biomeechanics, BK, DARPA, Exoskeletons, HiFi, ilimb, Knee Technology, Lower Extremity, Press Release / Media, Research, Socket Technology

In the February 2025 issue of the O&P edge, Randall Alley, CEO and Head of User-Interface Technolgy, expands on the concept of the Biotensegrity Bridge and how it relates to improved outcomes in prosthetic socket/interface design.

Socket designs conceived decades ago are still being taught and used when research, science and patient feedback continues to sound the alarm on all the inherent issues caused by the standard-of-care socket. The industry has fought back with improved liners, vacuum, advanced componentry, adjustability, additive manufacturing, and smart devices, yet the core principles of socket design remain unchanged. At biodesigns, we refuse to provide our patients with “buckets” (our patients’ term). Instead of distracting the wearer with 3D printing, adjustability, and advanced components, we look to the core of the interface platform and turn to biomechanics and the concept we have coined the Biotensegrity Bridge. Once a stable, effective, optimum interface platform is achieved, then it becomes more appropriate to apply innovative materials like 3D printing, determine if adjustability is necessary (including micro, macro and smart adjustments), discuss suspension options, apply desired configuration (solid socket vs. apertures) and finally determine which components are necessary, not the other way around.

“The osseostabilizing interface’s compression technology aligns prosthetic socket design with the principles of biotensegrity. By stabilizing the bone dynamically and replicating natural motion, the HiFi design supports the body’s tension-compression balance during both stance and swing phases. This improves gait efficiency and facilitates prosthetic embodiment, enhancing the overall health and well-being of prosthesis users. As a healthier alternative to traditional socket designs, osseostabilizing interfaces represent the future of prosthetic care, prioritizing function, comfort, and long-term outcomes,” stated Randall Alley in the article.

As an industry, the focus should be on interface biomechanics to improve comfort, performance and gait quality, instead of providing Band-aids for socket designs that are inherently flawed and shown to cause so many issues, short and long term. While change is difficult for many, patients have had to tolerate subpar designs for way too long. We believe patients’ lives are worth it.

Read the full article here

Biodesigns’ HiFi system is a patented prosthetic socket solution that integrates superior socket design, comfort, performance and support. We have built a global network of trained and certified prosthetic clinics that have integrated HiFi socket technology into their clinical workflow. To visit a clinic near you click here.

Mar 23
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Are You Able to Manage Bright Ideas and Promote Innovation?

By Biodesigns, biomechanics, Food for thought, HiFi, Lower Extremity, Military, Orthotics, Prosthetics, Upper Extremity
By: Julie Alley
Recently saw a “Bright Ideas” post and cartoon on LinkedIn (thanks Brent) stating how we manage and encourage bright ideas will determine the future of O&P. I have thought about the question of product and technique adoption a lot, as one of our goals is to improve the standard of care in interface designs in O&P, but more generally, improve all limb device integration.
   
Over the years, I have seen it is easier to ignore bright ideas or new discoveries instead of embracing them quickly. Look at Edison. Few could understand the life-altering benefits of the light bulb. And we see this time and time again. Many products take years to gain traction or adoption. So why are we so slow to move and why would someone ignore a bright area or new discovery? For me, everything comes down to motivation and if you are personally motivated to do something. So what motivates someone to disregard or pass on a big idea? Now I’m no psychologist and I don’t claim to be one, but I believe there are many possible answers. Is it pure laziness, a good enough mentality, complacency, or I’ve done it this way for so long that I don’t want to change? Is it ego or not created it here syndrome? Is it not knowing enough about something or the inability to comprehend the idea? Is it seen as helping the competition? Is it insecurities? Is it easier to try and rip it off? Is it a fear of failing? Is it a bad manager or supervisor? Is it too many distractions, the belief that it would take too long to implement, perhaps a disbelief in the benefit of the new idea or product, one not seeing it as being valuable or worth the price or investment? Is it short term vs. long term thinking, is it distractions at work or home, is it not having stake in the new idea, is it tunnel vision, is it how or what you were taught in school the dictates your world view, is it not a priority, and the list goes on. Coming from outside the industry into this industry, I quickly noticed that the value of the prosthetist is minimized and the main focus is on the components, with the threshold for success being acceptance or delivery of the device at that one moment in time, even before the patient has had ample time to test and use the device. If this is the best we can achieve, then innovation, at least in the interface will never be achieved by the masses. If the industry can look at themselves and say our high risk of falls in femoral and tibial prostheses, and low acceptance rates in upper limb, is not acceptable, then maybe there is hope. For us, biodesigns will continue as a company to push for superior interfaces, as this is the platform or core for the whole system. And we will stand with the few also pushing for improved designs, with the hope that the industy will follow. If the role of the prosthetist and interface continues to be minimized, reimbursement will continue to fall. The schools/master programs can help push the change, but if they continue to focus on the past with very little emphasis on newer designs, outcome measures, biomechanical principles, gait analysis, functional range of performance, energy expenditure, alignment, soft tissue management, etc., the future O&P clinicians, will have much to learn. And if the prosthetist doesn’t learn how to fight for their place in the system, based on an experience and expertise few other allied health professionals have, then you will be replaced. Anyone can learn how to take a few measurements and send them to fabrication. But very few can make a patient who has lost a limb feel whole again.
May 22
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Our Brain Can Change and Adapt, But Can You?

By Articles, Biodesigns, biomechanics, HiFi, Prosthetics, Socket Technology

In prosthetics, our ultimate goal should transcend the physical act of mere device delivery and extend into the realm of total device embodiment. This research is very interesting as it highlights the brain’s ability to adapt and change in significant ways. Prosthesis acceptance is a problem many struggle with and it is evident from the feedback we receive from amputees and others. Many prosthesis wearers come to us specifically because they are seeking a better connection to their prosthesis. They report that they feel very disconnected from their px, often stating it feels heavy, uncomfortable, inefficient, and unstable, resulting in a high risk and fear of falls. On the contrary, in our clinic and with our HiFi Licensees, we continue to document that most of our HiFi Prosthetic Interface wearers state their prosthesis feels like a part of them, feels significantly lighter, moves with them, and many report phantom sensations lost long ago now returning, allowing them to feel the ground, make quick adjustments and prevent falls. Some even forget they are wearing their prosthesis, the ultimate indication of device embodiment. I believe this to be the result of our High-Fidelity Interface’s emphasis on proper biomechanics, a term too often tossed around casually when referring to standard of care sockets with near total disregard for uncontrolled bone motion. Proper biomechanics is impossible if the primary mover is flailing about within the socket. With our patented and patents-pending osseostabilizing technology that was designed from its inception to control unwanted translation of the underlying bone shaft, we achieve a syncing of the prosthesis with skeletal motion. This synchronization in concert with a strongly activated fascial sensor network from targeted compression is a better match to the condition experienced prior to limb loss, allowing natural stimulation of the brain that is more representative of a sound limb. With skeletal control, the wearer can distance themselves from the artificiality of poorly connected prosthetic devices, allowing their brain to better “accept” this new condition and more fully incorporate it into the sense of self. In other words, get on with the business of living. While this is a great breakthrough in prosthetic technology, the limiting factor here is not our brain, as noted above, it instead is our industry’s reluctance to change, inability to break long established fitting habits (that yield subpar results), and refusal to acknowledge that perhaps the way we did things in the past was detrimental to our patients. My hope is to continue to work with those individuals, researchers, allied health professionals, etc., that continue to look forward – not backwards.

https://interestingengineering.com/human-brain-can-support-extra-robotic-body-part-third-thumb

Mar 04
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Alley Introduces the “Biotensegrity Bridge” for Human Device Interfacing

By Biodesigns, biomechanics, Food for thought, HiFi, Prosthetics, Socket Technology

In the March 2021 issue of the O&P Edge, Randall Alley, CEO and Head of User-Interface Technology, notes the issues with existing prosthetic socket designs and introduces a new model to consider for attachment, the Biotensegrity Bridge™, and describes how the patented and patents-pending HiFi Interface™ System creates a stable and functional “bridge” for attaching prosthetic devices.

“Since soft tissue (fascia) has a nonlinear stress/strain arrangement, traditionalists have incorrectly applied linear laws using levers and pulleys (mechanical physics) to explain the effects that the forces of gravity and tension elicit on our bodies. Biotensegrity has emerged as a new model of structural biology that is in diametric opposition to the Newtonian model of linear mechanical forces we all learned in school. Understanding the dynamic and continuous relationships between the soft tissue (fascia) and fluids within the body opens up new and exciting opportunities for better understanding the nature and role of the human-device interface,” stated Alley. “I give you what I am terming the Biotensegrity Bridge™ as a better way to approach interface integration.”

Read the full article: https://opedge.com/Articles/ViewArticle/2021-03-01/human-device-integration-introducing-the-biotensegrity-bridge

Mar 24
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biodesigns Delivers Advanced Arm During Corona Virus Outbreak

By Biodesigns, biomechanics, HiFi, Socket Technology, Upper Extremity

biodesigns, in California, best known for their prosthetic interface/socket technology, recently delivered an advanced arm system during this unusual time as a result of the Corona Virus. “We consider our business vital to our patients and want them to know we are here for them,” stated Randall Alley, CEO, Chief Prosthetist for biodesigns. The system delivered included advanced technology including Alley’s patented and patents-pending HiFi interface design, Coapt Engineering’s Gen2 Pattern Recognition, College Park’s Espire Powered Elbow, and Motion Control’s Wrist Rotator and External Terminal Device (ETD2). The system will also be used with the user’s existing ilimb Quantum hand. biodesigns takes great pride in designing prosthetic systems that are appropriate for their users. “This user is long time wearer that has proven time and time again the many functional benefits he receives from his prostheses,” stated Alley.

 

May 30
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Jason’s Bionic Arm – HiFi Interface, Coapt, LTI Elbow, I-Limb Hand

By Biodesigns, biomechanics, HiFi, ilimb, Myoelectric, Prosthetics, Socket Technology, Upper Extremity
“There is definitely a preconceived notion that a body-powered system is lighter, but with this HiFi socket it makes the arm feel just as light as body-powered. There is more stability across the entire length of the arm. There are no pinch points, way more degrees of freedom, more responsive, better connection to all the sensors.”

 

May 18
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Amputee Has Shocking Reaction to her Socket

By Biodesigns, biomechanics, BK, HiFi, Prosthetics, Socket Technology

Arlene, a below-knee amputee for almost 20 years, couldn’t believe the difference between her traditional socket and her new HiFi. With the HiFi, “it feels so much more natural. I don’t have to think about walking. That’s Amazing!”  In my old socket, it “feels like I’m going to go down. The knee is going to buckle. It’s a little scary.” Arlene shows the HiFi can help users of all ages. Everyone can benefit from HiFi’s ability to provide added stability and control.

Jan 12
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Biomechanical Design Considerations for Transradial Prosthetic Interface: A Review

By Biodesigns, biomechanics, HiFi, Prosthetics, Socket Technology, Upper Extremity
ABSTRACT. Traditional function and comfort assessment of transradial prostheses pay scant attention to prosthetic interface. With better understanding of the biomechanics of prosthetic interface comes better efficiency and safety for interface design; in this way, amputees are more likely to accept prosthetic usage. This review attempts to provide design and selection criteria of transradial interface for prosthetists and clinicians. Various transradial socket types in the literature were chronologically reviewed. Biomechanical discussion of transradial prosthetic interface design from an engineering point of view was also done. Suspension control, range of motion, stability, as well as comfort and safety of socket designs have been considered in varying degrees in the literature. The human–machine interface design should change from traditional “socket design” to new “interface design.” From anatomy and physiology to biomechanics of the transradial residual limb, the force and motion transfer, together with comfort and safety, are the two main aspects in prosthetic interface design. Load distribution and transmission should mainly rely on achieving additional skeletal control through targeted soft tissue relief. Biomechanics of the residual limb soft tissues should be studied to find the relationship between mechanical properties and the comfort and safety of soft tissues.
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