Biomechanics In Lower Limb Prosthetics Engineering Essay

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The silicon liner socket has been used in the trans-tibial prosthesis since the 1980s. Silicon liner sockets are sleeves of silicon material that are rolled onto the stump and fix the prosthesis to it [1].Clinically the silicon liner socket is increasingly prescribed for reasons of better suspension, better cosmetic and socket comfort [2].

The last version of silicone liners is Seal-in Liner, a new suction suspension liner that incorporates a hypobaric sealing membrane (HSM) around the liner, providing a firm, comfortable suspension without an external sleeve or shuttle lock. The Seal-in Liner also accommodates the volume reduction of the residual limb. With the HSM, the hypobaric pressure will always be in direct proportion to the suspension force needed, ensuring superior stability, comfort and control. The membrane also provides a firm and comfortable suspension and amputees who may not have been able to use traditional suction may be able to use this sleeve [3-19].

The use of silicone liners, with or without the incorporation of shuttle locks, has greatly improved the function of artificial limbs compared to the conventional supracondylar fitting. They cushion and protect the stump and provide a means for prosthetic suspension and allowing more comfortable use, especially in active patients. They also allow greater movement at the proximal joint [4].

2. Statement of the Problem

The method of attachment of an external prosthesis to the limb stump, comfort and gait in amputees are a major consideration. The use of silicone liners in prosthetics is not new. It has two main functions, namely, protection of the amputation stump and suspension of the prosthesis [2]. Suspension in silicone suction socket can be achieved in different ways, such as shuttle lock, sleeve, or a Hypobaric Sealing Membrane (HSM) around the liner (a new technology in silicone liners). On the basis of the researcher's experience, a great number of amputees have some problems in their stump, like contracture, diabetic, or skin problem and they complain about silicone liner with shuttle lock. It was the starting point for dealing with this topic in general and searching about this problem in particular.

3. Review of Related Literature

Van DE Weg F. B. et al (2005) came to this conclusion that patients wearing liners reported a significantly poorer durability and higher maintenance time compared with patients using polyethylene foam (PEF) inserts. Analysis of individual items showed a significant difference only for satisfaction with sitting and with walking on uneven terrain in favor of PEF inserts [5].

A research done by JIA Xiaohong et al. (2008) showed that the amputee changes the knee joint moment, gait symmetry, and interface pressure with a misaligned prosthesis to improve his comfort and movement during walking. They came to this conclusion that high-quality liner also reduces the gait sensitivity to misalignment and enhances the amputee's ability to compensate for misalignment [6].

E. C. T. Baars & J. H. B. Geertzen (2005) asserted that there is a good indication to believe that the suspension of the prosthesis is improved when using a liner. Furthermore, the walking performance with the prosthesis is positively affected which results in increased walking distance outdoors and less dependence on walking aids. They stated that skin problems are not generally solved by liner use. Even these skin problems are also caused by line use[1].

Kim L. Coleman et al. (2004) compared Elastomeric gel liner with locking pin suspension versus polyethylene foam liner. There were no differences in satisfaction, pain, or comfort results. Ambulatory intensity profiles during bouts of activity did not differ between conditions. Subject feedback for each system was both positive and negative, and illustrated the multiplicity of factors influencing the experience with a prosthetic socket [7].

Hachisuka et al. (1998) found positive questionnaire responses to "piston movement during walking," "ease to swing the prosthesis," and "comfort to wear". They were significantly related to a rating of "satisfied" or "somewhat satisfied" with the Silicone Suction Socket system. They reported that out of 32 subjects, over 90 percent rated walking as "good" or "somewhat good" with the 3S system. They also found a decrease in pain sensation in liner users (53%) [8].

Lake and Supan (1997) reported that silicone liners provided a superior form of suspension with minimal pistoning that gave users a feeling of secure suspension. They concluded that for some amputees, finding the proper liner has made a huge improvement in ability by diminishing limitations [9]. Narita et al. (1997) used static x-ray and dynamic cineradiography to measure the suspension effect of TSB sockets with ICEROSS locking liners versus PTB sockets. They quantified statistically significant improvements with the ICEROSS condition [10].

In a survey of 72 doctors and prosthetists in the United Kingdom, McCurdie et al. (1997) found suspension to be the leading "absolute" or "primary" indicator for ICEROSS prescription. Pistoning, lack of success with other forms of suspension, and need for improved suspension due to change in type or level of activity were seen as clear indicators for ICEROSS use [11]. In that year, Dasgupta et al. (1997) studied 27 subjects and found statistically significant improvements in timed walks with ICEROSS systems [12].

In a study of 54 persons, Datta et al. (1996) found that subjects did not report walking more, having greater ease negotiating uneven surfaces, reducing the use of mobility aids or wearing the prosthesis more with the ICEROSS prosthesis compared to previously worn PTB prostheses[13]. Moreover, Cluitmans et al. (1994) compared the silicon liner socket to the KBM and other socket types. They examined changes in walking ability indoors and on uneven surfaces. They also examined changes in walking speed and distance with the most improvement in the latter (54%) compared to the KBM and other types of prostheses. They reported that elastomeric suspension liners provide improved Suspension [14].

The pistoning of the prosthesis was clinically studied by Yig˘iter et al. (2002). They marked the anterior superior border of the socket and measured the difference in the stance and swing phase of the prosthesis and found an average of 1.2 cm less pistoning in the liner socket compared to the PTB socket [15]. A.M. Boonstra, et al. (1996) reported that some amputees cited a preference for the 3S because of the close connection between liner and socket resulting from the mechanisms' shuttle-lock construction and the different pressure distribution of the 3S compared with the PTB socket with pelite liner [16].

Gailey and his colleagues studied SSWS (self selected walking speed) in 39 TFA patients wearing prosthesis with different weights. They found that the SSWS of amputee patients with a heavier prosthesis (2.7kg average) was 8% higher than the SSWS of patients with a lightweight prosthesis (2.0kg average); however, this difference was not statistically significant [17]. Lehmann et al. (1998) changed the prosthetic center of mass location of 15 below knee amputees from 47% to 60% distal to the knee without changing prosthetic mass, and found that the SSWS (self selected walking speed) did not significantly change when the center of mass location was altered [18].

Selles Ruud al. (2004) came to this conclusion that, trans-tibial amputees adapt to mass perturbation primarily by maintaining the same kinematic pattern and adjusting their joint torques, that is, they use a kinematic invariance strategy. This implies that manipulating prosthetic inertial properties does not directly influence gait kinematics and the inertial properties should be evaluated in terms of the energetic cost of the swing phase [20].

To the best of the researcher's knowledge, no studies have directly been done about differences between Seal-in and Locking liners on gait and comfort in trans-tibial amputees.

4. Objectives of the Study


This study embarks on the following objectives:

To study stump/liner socket interface pressure, and obtain kinematics and kinetics parameters of trans-tibial amputee gait using Locking liner and Seal-in liner (Will use Tekscan Inc. F-scan 6.11 pressure measurement system and Vicon Nexus motion capture system).

To study and identify any pistoning movements inside a prosthetic socket (Locking liner and seal-in liner)

To evaluate the biomechanical characteristics of liner (locking or seal-in) by mean of enhance comfort, function, and reduction of skin damage in Trans-Tibial amputees.

5. Methods

First, a large number of papers and theses regarding biomechanics in lower limb prosthetics will be carefully examined and relevant data will be manipulated for the review of literature section to know what previous researchers have done about this topic.

10 subjects of trans- tibial amputees ( unilateral) will participate in the study

10 trans-tibial prosthetics with silicone liner and shuttle lock will be made by researcher for the subjects and then Subjects will be required to walk with their prosthesis in the Brace and Limb Laboratory (Clinical P&O Lab) with shuttle lock and do various physical activities, i.e. donning and doffing of prosthesis, stand up, sit down, standing, sitting, walking and running.  

The researcher (Registered Prosthetist) will check the prosthesis alignment and fitness of the prosthesis socket.

Subjects will then ask to go back to their normal living and come back after one month for evaluation and fill the PEQ questionnaire. While subject waking in the motion analysis laboratory, kinematics and kinetics parameters were tracked simultaneously together with stump-liner-socket interface pressure measurement. Also, pistoning movements inside the prosthetic socket will be measured for each subject.

After one month, the subjects with Iceross shuttle lock will then change by the Prosthetist to make a new prosthesis with Seal-in liner and repeat a same procedure as in (i - iii).

All prostheses will be made by the researcher himself to ensure similar criteria of manufacture, fitting and alignment and avoid variability derived from these factors. Each subject will be recommended to wear seal-in (Iceross Seal-In® X5 Transtibial Liner) and locking liner (Iceross Dermo Locking liners) for at least one month in different situations and places. During the process of making the prosthetics if a patient complains about one of the silicone liners, that liner will be eliminated. Each prosthesis consists of a total surface weight bearing socket, silicone liner (locking or seal-in liner), shuttle lock or valve, tube adaptor, clamp adaptor, and foot.

Iceross Seal-In® X5 Transtibial Liner

Icelock Expulsion Valve 551

4-Prong Socket Adapter

Male Pyramid Insert for Prong

Female Pyramid Tube Clamp

Female Pylon - Short or Long


Iceross Dermo Locking liners

6. Work Schedule

After the final approval of this proposal, the research will be timetabled for 16 months and organized in a thesis with the following chapters:

It takes four months for the first two chapters to be completed. Chapter one includes introduction in which the problem under study will be introduced, and significance and background of the study will be presented as well. Chapter two consists of literature review which the most outstanding papers and theses regarding biomechanics in lower limb prosthetics will be carefully examined.

The remaining time will be devoted to the last three chapters. Chapter three will cover the method of the study in which some information about the subjects will be provided. It takes about eight months to design, Chapter four contains results and findings in which the results of the study will be presented in appropriate tables and figures. It takes 3 months to evaluate and analyze the kinematics and kinetics data. The last month will be devoted to administration of the Prosthesis Evaluation Questionnaire (PEQ). Chapter five includes summary, discussions, and conclusions in which the study will be summarized, the findings will be discussed, and some implications based on the findings of the study will be presented.

7. Required Equipment

According to the number of selected subjects, the following equipment and materials will be required:

Iceross Seal-In® X5 Transtibial Liner

Icelock Expulsion Valve 551

4-Prong Socket Adapter

Male Pyramid Insert for Prong

Female Pyramid Tube Clamp

Female Pylon - Short or Long


Iceross Dermo Locking liners

- Tekscan Inc. F-scan 6.11 pressure measurement system

- Vicon Nexus motion capture system

- good high quality measuring tape

- 3, 5 and 10 kg loads

- photo camera with high resolution