Adjustable prosthetic sockets: a systematic review of industrial ...

Adjustable Prosthetic Sockets: An In-Depth Industrial Review

This investigation delves into the design attributes of prosthetic sockets, reasons behind their adjustability, and the limitations and safety considerations for each design. Clinical studies were examined to evaluate their scope and outcomes, both generally and within each specific adjustability principle. Control methods and the importance of aesthetics in design are also explored.

If you want to learn more, please visit our website prosthetic socket adapter.

Rationale Behind Design

Determining the reasoning behind design choices is challenging because patents and commercial products either cover a wide array of possible embodiments (patents) or promote product features (commercial products). We found minimal research publications connected to these designs. The Click Academy provides insights into different design approaches and their potential benefits, although these claims lack research backing. Some companies do present research on their websites, and Ottobock hosts a clinical research section on their site, though specific papers, such as those about their socket designs, might not be easily accessible.

Research often involved clinical expertise to determine if the initial socket fit was too tight or loose, or by replicating the participant's current clinical socket. This approach is preferred due to limited research guiding socket fit decisions. Some studies aimed to create a metric or pressure measurement for a well-fitted socket and maintain this through adjustments. Alternatively, pressure limits were approximated for the residuum tissue and adjustments were restricted to these limits. Notably, interface pressure alone is a poor predictor of tissue damage due to the varying internal tissue loads depending on factors like bony prominences and soft tissue characteristics. Articles about inflatable bladders often justified their design by maintaining a constant internal socket pressure or developing algorithms that adjusted the bladders automatically based on the limb's position.

Socket Adjustments

The adjustment range was commonly reported as a percentage change in socket volume. Some references cited "good" and "acceptable" fitting socket limits as 5% and 10% volume changes, respectively. However, there is little research comparing the effects of varying the volume locally or generally on fit, performance, comfort, and tissue health. Some studies had adjustments determined by the participants themselves. Small adjustments cater to minor residual limb volume changes or ease tasks like donning the socket, while clinician adjustments accommodate larger physiological changes without needing to redesign or replace major components.

Principles of Adjustability

The authors did not physically inspect sockets, leading to assumptions based on limited literature and patent details. Inflatable bladders control interface pressures and can focus on local areas or the residuum as a whole. These designs, often complex, add weight and risk of failure. Moveable panels cut from a fixed geometry socket ensure good fit and only adjust load-tolerant regions. The influence of panel size and location on comfort and mechanical coupling is unknown. Underactuated moveable panels' behavior needs further research, as does the actuator-to-panel ratio's impact on adjustments. Moveable panels may aid the donning process and socket suspension, particularly for joint disarticulations.

Circumferential adjustment designs rely on socket material flex to change shape, while strut designs allow volume changes where the residuum accepts additional compression. Strut designs handle large daily volume fluctuations well but can cause discomfort or tissue damage if overtightened. Designs combining variable length with other adjustability principles are useful for making off-the-shelf sockets suitable for low-resource settings. Clinicians set socket dimensions based on the patient's residuum geometry, with users making subtle adjustments away from this setting.

Safety and Limitations

Inflatable bladder designs are hard to evaluate for safety, but their constant pressure nature can be safer regarding tissue loads. However, risks include bladder leaks, bursts, or delamination. Liquid-filled bladders depend on reservoir capacity, while air bladders have greater potential and operate without reservoirs. Bladder volume changes during the gait cycle are limited by fluid viscosity and pump flow rates. Moveable panels and circumferential adjustment designs have defined minimum socket volumes, with user-visible limits. These designs offer less control over specific adjustment locations, potentially causing discomfort or damage. Further research is needed to understand how socket shape and gap/overlap location influence volume adjustments.

For more information, please visit foot is single.

Clinical Studies

Low participant numbers reflect the early stage of this field and limited eligible research participants, particularly with upper limb absence. Upper-limb tests were typically in controlled environments, rarely examining post-fit adjustment impacts due to lower volume fluctuations compared to lower limbs. Studies were often short-term, limiting safety and durability assessments.

Inflatable bladder studies varied in aims and outcome measures, hindering extrapolation. Some focused on residual limb fluid volume and recovery, while others on residuum-socket interface pressure. Optimal comfort was associated with different bladder pressures among participants, highlighting comfort subjectivity. Moveable panel studies had higher participant numbers, with some showing effective fluid retention during exercise and rest. However, few included comfort as an outcome measure, and those that did showed inconsistencies in methods. Circumferential adjustment socket studies used validated comfort measures, reporting improvements over original sockets but without documented reasons.

Outcome measures included bioimpedance, internal socket pressure, and comfort and pain scores, varying between studies. No clinical study compared different adjustable socket designs. Internal socket pressure measurements improved comfort by preventing overtightening. Unclear is if adjustable sockets improved gait; further research is needed to explore comfort and coupling changes and their impact on gait. Few studies reported adverse events despite adjustable sockets having the potential to cause harm if improperly adjusted.

Actuation Mechanisms

Micro-Adjustment Dials

Cable and dial strength limits tension and pressure, which are not visible to the user. External dials compromise aesthetics, catch on clothing, and require lamination capabilities. They may only be viable in clinics with such capabilities.

Straps

Straps can prevent over or under-tightening. Continuous and discrete mechanisms are easily implemented and cost-effective, especially in low-resource settings. However, Velcro adjustments require complete removal before reapplication, hindering small changes. Safety concerns are minimal, but continuous straps may slip under high forces and degrade over time.

Pumps or Motors

Pumps and motors offer precise adjustment limits, enhancing safety. However, additional components add bulk and weight, positioned distally, affecting gait and control. Their size may limit feasibility for longer residual limbs, and fluid or cable routing complicates design and manufacturing.

Cosmetics

Aesthetics can enhance prosthesis satisfaction and embodiment. Recently, clinical studies focused less on aesthetics, prioritizing socket observation and interaction. The low number of companies offering covers reflects the need for access to external control mechanisms and adaptive covers. The LIM Innovations socket design avoids this issue by positioning the adjustment dial away from the socket wall.

Patent Search Methodology

Most companies were found via patent search, but many patents could not be linked to active products or research institutions, suggesting search criteria refinement is needed. Using the same criteria for literature and patent searches would reduce effectiveness since patents use more generic terms.

Socket-less Socket™ Clinical Outcomes

Prosthetic sockets can cause skin issues, but the Socket-less Socket™ offers unique breathability and conformity, reducing skin problems for more active users.

The company is the world’s best orthotic knee joint supplier. We are your one-stop shop for all needs. Our specialized staff will help you find the right product.