Comparative study of ischial containment socket and quadrilateral socket for functional ability in persons with unilateral transfemoral amputation.

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COMPARATIVE STUDY OF Ischial containment socket AND

Quadrilateral socket for functional Ability

IN PERSONS WITH UNILATERAL TRANSFEMORAL AMPUTATION

Dissertation submitted to the Tamil Nadu Dr. MGR Medical University,

Chennai, in partial fulfillment of requirements for the MD Branch XIX

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D E C L A R A T I O N

I hereby declare that “Comparative study of Ischial containment socket

and Quadrilateral socket for functional ability in persons with unilateral

transfemoral amputation” is my bona fide work in partial fulfillment of the

requirement of the Tamil Nadu Dr. MGR Medical University, Chennai, for

the MD Branch XIX (Physical Medicine and Rehabilitation) examination in

April 2016.

Dr. Nitha. J

Candidate Number 201329052

Department of Physical Medicine and Rehabilitation

Christian Medical College

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C E R T I F I C A T E

This is to certify that “Comparative study of Ischial containment socket

and Quadrilateral socket for functional ability in persons with unilateral

transfemoral amputation” is the bona fide work of Dr. Nitha. J, Candidate

Number 201329052 in partial fulfillment of the requirement of the Tamil

Nadu Dr. MGR Medical University, Chennai, for the MD Branch XIX

(Physical Medicine and Rehabilitation) examination in April 2016, done

under my supervision and guidance.

Dr. Henry Prakash

Professor

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This is to certify that “Comparative study of Ischial containment socket

transfemoral amputation” is the bona fide work of Dr. Nitha.J, Candidate

Number 201329052, in partial fulfillment of the requirement of the Tamil

Nadu Dr. MGR Medical University, Chennai, for the MD Branch XIX

(Physical Medicine and Rehabilitation) examination in April 2016, done

Dr. George Tharion

Professor and Head of the Department

Christian Medical College

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This is to certify that “Comparative study of Ischial containment socket

transfemoral amputation” is the bona fide work of Dr. Nitha.J, Candidate

Number 201329052, in partial fulfillment of the requirement of The Tamil

Nadu Dr. MGR Medical University, Chennai, for the MD Branch XIX

(Physical Medicine and Rehabilitation) examination in April 2016, done

Dr. Alfred Job Daniel

Principal

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ACKNOWLEDGEMENT

Even though my name appears primarily on the covers of this thesis, a great many

people have contributed to its production. I owe my humble gratitude to all these

people who have made this thesis possible and made this work a cherishable

experience.

I would like to express my deep gratitude to my guide Dr. Henry Prakash whose

advice and guidance have enabled me to successfully complete the study. I am also

thankful to him for reading my reports, helping me understand and enrich my ideas.

I would like to thank Dr. George Tharion, Professor and Head of the Department of

PMR for his support and encouragement for this study. His insightful comments and

constructive criticisms were deeply thought provoking.

I wish to thank various people without whom this study would not have been possible

– All who have been involved with the study from the department of Prosthetics and

Orthotics, for their valuable suggestions, time and efforts. Particularly, I would like

to acknowledge Mr. Vinoth Jacob, from P&O for his unstinted support and

cooperation. Special thanks to Mr. Mansur Ali and Mr. Dinesh from P&O for their

support in the completion of the thesis. The doctors in charge of the Amputee Clinic

who helped me enroll my patients, my teachers and friends in the department who

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A special thanks to Mrs. Joyce the neutral assessor and gait analyst, who have helped

me with the data acquisition.

I would like to express my great appreciation to the patients who took part in the

study without whom none of this would have been possible.

Most importantly, none of this would have been possible without the love and

patience of my family. I am deeply thankful to my 2 year old son Aadith, who

without any complaints for the limited time I spent with him, has loved me and made

my life meaningful. Special thanks to my loving husband and my ever caring parents,

who have stood by me always.

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LIST OF FIGURES

Figure 3-1 - FORCE VECTORS ACTING ON SINGLE LIMB SUPPORT ... 11

Figure 3-2 – PELVIS ACTING AS LEVER ... 12

Figure 3-3 - ALIGNMENT STABILITY ... 15

Figure 3-4 HIP ABDUCTOR INSUFFICIENCY ... 22

Figure 3-5 QUADRILATERAL SOCKET ... 22

Figure 3-6 LATERAL TRUNK LEAN ... 23

Figure 3-7 PROTO ISCHIAL CONTAINMENT SOCKET ALIGNMENT ... 25

Figure 3-8 ISCHIAL CONTAINMENT SOCKET ... 26

Figure 3-9 – COMPONENTS IN TRANSFEMORAL KIT OF ICRC ... 41

Figure 4-1 ISCHIAL CONTAINMENT FABRICATION PROCEDURE ... 55

Figure 4-2 – TIMED UP & GO TEST ... 60

Figure 4-3- GAIT ANALYSIS... 63

Figure 5-1 ETIOLOGY OF AMPUTATION ... 68

Figure 5-2-6MWT TEST IN QUADRILATERAL & ISCHIAL CONTAINMENT SOCKET ... 71

Figure 5-3 – RELATION OF 6MWT VS AGE ... 71

Figure 5-4- 6MWT VS ETIOLOGY ... 72

Figure 5-5- 6MWT VS DURATION OF PROSTETIC USE ... 72

Figure 5-6- TUG TEST IN QUADRILATERAL & ISCHIAL CONTAINMENT SOCKET ... 74

Figure 5-7- TUG VS ETIOLOGY ... 74

Figure 5-8- TUG VS AGE ... 75

Figure 5-9- TUG VS DURATION OF PROSTHETIC USE ... 75

Figure 5-10- SCS IN QUADRILATERAL & ISCHIAL CONTAINMENT SOCKET ... 77

Figure 5-11 – SOCKET PREFERENCE IN TRANSFEMORAL AMPUTEE PERSONS ... 77

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Figure 5-13- GAIT VELOCITY IN QUADRILATERAL & ISCHIAL CONTAINMENT SOCKET ... 81

Figure 5-14 – GAIT VELOCITY VS ETIOLOGY ... 81

Figure 5-15- GAIT VELOCITY VS AGE ... 81

Figure 5-16- GAIT CADENCE IN QUADRILATERAL & ISCHIAL CONTAINMENT SOCKET ... 83

Figure 5-17 – STRIDE LENGTH IN QUADRILATERAL & ISCHIAL CONTAINMENT SOCKET ... 83

Figure 5-18 – STRIDE LENGTH VS AGE ... 84

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LIST OF TABLES

Table 3-1PHASES OF AMPUTEE REHABILITATION ... 5

Table 3-2 COMPARISON OF QUAD & IC SOCKET ... 30

Table 5-1 DEMOGRAPHIC DATA OF PATIENTS... 66

Table 5-2 AGE DISTRUBUTION OF PATIENTS ... 67

Table 5-3 DURATION OF PROSTHETIC USE ... 69

Table 5-4 CORRELATION OF THE 6 MINUTE WALK TEST WITH AGE, ETIOLOGY AND DURATION OF PROSTHETIC USE IN QUAD AND IC GROUPS ... 70

Table 5-5 CORRELATION OF THE TIMED UP AND GO TEST WITH AGE, ETIOLOGY AND DURATION OF PROSTHETIC USE IN QUAD AND IC GROUPS ... 73

Table 5-6 CORRELATION OF THE SOCKET COMFORT SCORE WITH AGE, ETIOLOGY AND DURATION OF PROSTHETIC USE ... 76

Table 5-7 CORRELATION OF THE PHYSIOLOGICAL COST INDEX WITH AGE, ETIOLOGY AND DURATION OF PROSTHETIC USE ... 79

Table 5-8 CORRELATION OF THE GAIT VELOCITY WITH AGE, ETIOLOGY AND DURATION OF PROSTHETIC USE ... 80

Table 5-9 CORRELATION OF THE GAIT CADENCE WITH AGE, ETIOLOGY AND DURATION OF PROSTHETIC USE IN THE QUAD AND IC GROUPS. ... 82

Table 5-10 CORRELATION OF THE STRIDE LENGTH WITH AGE, ETIOLOGY AND DURATION OF PROSTHETIC USE IN THE QUAD AND IC GROUPS ... 84

Table 5-11 SINGLE LIMB SUPPORT OF AMPUTATED AND NORMAL SIDE LIMBS WITH QUAD AND IC SOCKET ... 85

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LIST OF EQUATIONS

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TITLE OF THE STUDY

Comparative study of ischial containment socket and

quadrilateral socket for functional ability in persons with

unilateral transfemoral amputation

PLACE OF STUDY

Dept. of Physical Medicine and Rehabilitation

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ABSTRACT

TITLE

Comparative study of ischial containment socket and quadrilateral socket for

functional ability in persons with unilateral transfemoral amputation

.

OBJECTIVE

To compare ischial containment socket with quadrilateral socket in transfemoral

amputee persons in terms of functional ability and socket preference.

METHODOLOGY

This is an interventional study where transfemoral amputee persons ambulant with

prosthetic limb fitted with quadrilateral socket were enrolled after informed consent.

First assessment was done with the quadrilateral socket during the initial visit. Then

they were provided with ischial containment socket. The knee component, pylon and

the foot piece were retained without alteration. Each patient was given two weeks’

time to acclimatize to the new socket. At the end of two weeks all the assessments

were repeated with the ischial containment socket.

OUTCOME MEASURES

Functional ability was measured with the 6-minute walk test (6MWT) and Timed Up

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final socket preference. The secondary outcome measures were energy efficiency

with Physiological Cost Index and gait parameters. The outcome measures were

statistically analyzed with the paired T test.

RESULTS

The ischial containment socket (IC) was preferred by 87 % of patients who were

already community ambulant with quadrilateral socket (QUAD). The socket comfort

score significantly improved with the ischial containment socket. The ischial

containment socket is superior to quadrilateral socket in terms of comfort. The

comfortable walking speed of transfemoral amputee persons improved with the

ischial containment socket. The gait velocity and stride length showed statistically

significant improvement with ischial containment socket. The 6MWT, TUG and PCI

showed better results with ischial containment socket even though the improvement

was not statistically significant. Observable variations in gait deviations were not

seen with the socket change.

CONCLUSION

The ischial containment socket is an evolutionary transfemoral socket design, which

provides better comfort for transfemoral amputee persons. The ischial containment

socket might potentially improve walking ability and endurance in unilateral

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INTRODUCTION

Amputation is a lifesaving as well as a life changing event. Once the decision for

elective amputation is made, the primary focus should be preparing the individual

physically and mentally for the surgical procedure. Such amputations should be

followed by a goal oriented extensive rehabilitation phase. Functional rehabilitation

of amputee person’s, especially ones with higher levels of amputation like

transfemoral levels is a challenge. To restore all the functional activities at their near

normal physiological level should be the ultimate goal.

The residual limb is fitted with prosthesis. The expected role of prosthesis is

substituting the functions of normal limb, which is independent ambulation in lower

limb amputee persons. The prosthesis should provide comfort as well as cosmesis.

Prosthetic rehabilitation should make the person capable of leading a normal and

successful life as far as possible.

Understanding of the complex biomechanics of human locomotion as well as

developments in material science has contributed in the advancement in field of

prosthetic design and fabrication. The prosthetic technology has evolved from the

plug fit wooden sockets to osseo-integrated prosthesis, microprocessor knee and

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A socket is a part of the prosthesis which attaches to the residual limb. For

transfemoral residual limb a few socket designs have been developed over the last

few decades. The Quadrilateral socket has been the socket design of choice for

transfemoral prosthesis from its inception in 1950’s till last two decades. The Ischial

containment socket emerged in 1980’s with sound biomechanical concepts while

addressing the short comings of quadrilateral socket. Even though the biomechanical

principles of the ischial containment socket is better; the quadrilateral socket

continued to be the preference in most of the nations.(1) The skill needed to fabricate

an ischial containment socket is more than the conventional quadrilateral socket.

This study aims at comparing the ischial containment socket with quadrilateral socket

in terms of functional abilities and socket preference. Does the theoretical advantage

of ischial containment socket, correlate with the functional outcome of transfemoral

amputee persons?

In this study transfemoral amputee persons who have been ambulant with

quadrilateral socket were recruited and were given prosthesis, where the quadrilateral

socket was replaced with an ischial containment socket. Outcome measures were

assessed with quadrilateral as well as ischial containment socket, followed by

statistical analysis. The outcome measures used in this study were 6 minute walk test,

timed up and go test, socket comfort score, socket preference, gait parameters and

physiological cost index. At the end of the study patients were given an option to

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AIMS & OBJECTIVES

2.1

AIM

To evaluate the theoretical advantage of ischial containment socket over quadrilateral

socket in rehabilitation of transfemoral amputee persons.

2.2

OBJECTIVE

To compare ischial containment socket with quadrilateral socket in transfemoral

amputee persons in terms of functional ability and socket preference.

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REVIEW OF LITERATURE

3.1

AMPUTATION

Amputation is the removal of a limb or a part of the limb by trauma, medical illness,

or surgery. History of amputation dates back to Hippocrates era. Then the surgical

principle was lost in Dark Ages and reintroduced in 1529 by Ambroise Pare, when he

first used ligatures to control bleeding. The introduction of tourniquet by Morel and

antiseptic technique by Lord Lister contributed in the further development of

amputation techniques. The discovery of chloroform as an anesthetic agent made the

surgery more reasonable. The surgical technique of amputation advanced rapidly

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3.1.1

STATISTICS

Global burden of disease refers disability as “loss of health where health is

conceptualized in terms of functioning capacity in a set of health domains such as

mobility, cognition, hearing and vision”.(3) According to WHO statistics the global

disability prevalence is 15 % that is about one in seven of world population is

disabled.(4) As per the Census of India 2011, 2.1 percent of Indian population is

estimated to have disability.(5) Even though amputation being a major contributor to

disability, its exact burden on disability or its global incidence is unknown. The

available data shows considerable variations among countries and within countries.

3.1.2

ETIOLOGY OF AMPUTATION

Globally the main three causes for amputation are trauma, diseases and congenital

malformation. Trauma is the major cause of amputation globally.(6) Diabetes

contributes 30-90 percent of lower extremity amputations.(7) In India the major

cause for amputation is trauma.(8,9) The next important cause is diseases. Chronic

diabetes and peripheral vascular disease is the most common non traumatic cause for

lower limb amputations.(10) The study conducted by Pooja et.al from Kolkata

observed that 70 percent of amputation was due to trauma and 27 percent due to

vascular disease. Traumatic amputations are more with young and active individuals,

with male predominance.(8) Lower limb amputations constitute about 95% of all

major amputations. The most common level of amputation is transtibial level.

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3.2

REHABILITATION OF PERSONS WITH TRANSFEMORAL

AMPUTATION

Rehabilitation of an amputee person includes a multidisciplinary approach, involving

surgeon, physiatrist, psychologist, physiotherapist, occupational therapist and

prosthetic technicians. Adequate rehabilitation should aim at restoring the acceptable

functional capacities allowing individuals to achieve their goals, allow participation

in society and to improve quality of life with or without prosthesis.(11) The

rehabilitation process should start when the decision for amputation is made,

covering pre and post-surgical period. The patient should be informed about the

anticipated functional outcomes according to the level of amputation and medical

[image:26.612.68.548.421.697.2]

conditions.(12)The phases of amputee rehabilitation are as follows(6,13,14)

TABLE 3-1PHASES OF AMPUTEE REHABILITATION

PHASES GOALS

1. Preoperative Preparing psychologically and physically for amputation,

determining the level of amputation, discussing the expected

functional outcomes, alleviating anxiety and stress,

sensitizing about phantom pain and phantom sensation.

2.Amputation

surgery

Myoplasty techniques for better femur adduction, Nerve

handling, Rigid dressing application

3. Acute

post-surgical

Optimization of analgesics. Emotional support, mobilization

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4.Preprosthetic Residual limb shaping, restoring sense of control, improving

muscle power and maintaining full range of motion

5.Prosthetic

Fabrication

Consensus on prosthetic prescription, prosthetic measurement

and fabrication

6.Prosthetic

Training

Functional use of prosthesis

7. Community

integration

Resuming social roles, developing healthy coping strategies,

recreational activities

8.Vocational

Rehabilitation

Job modifications and training

9.Follow up Lifelong medical, functional and prosthetic assessment and

emotional support

3.2.1

PRE-OPERATIVE PERIOD

The functional rehabilitation in the preoperative period includes maintaining ROM,

stretching out the contracted muscles, conditioning the normal side, increasing the

endurance, practicing the single limb gait. This preoperative initiation of

rehabilitation can reduce the time spent in postoperative rehabilitation.(12)

3.2.2

TRANSFEMORAL AMPUTATION

Trans femoral amputations forms about 30% of total major amputations.(6) Trans

femoral amputations can be classified as supracondylar, long, medium and short

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Gottschalk modification - Gottschalk found that the prosthetic shape or alignment is

not sufficient to keep hip in adduction. Hence he modified the transfemoral

amputation surgical principle by preserving the adductor magnus if possible and

attaching it to distal end of femur with drill holes, while femur is maintained in

adduction.(16) Even though the biomechanical principle was good, it didn’t evolve as

a standard surgical practice.

3.2.3

ACUTE POST SURGICAL MANAGEMENT

In the acute post-surgical period pain management and wound care is most important.

The residual limb can be fitted with immediate post-operative prosthesis or

prefabricated prosthesis.

IMMEDIATE POST OPERATIVE PROSTHESIS (IPOP) – It is applied in the

operation room itself. It consists of a rigid dressing made of POP or fiberglass, a

connector, pylon and a foot piece. Early ambulation in the second or third

post-operative day is the most important advantage of this technique. The other

advantages are reduction of edema, protection from trauma, lower rate of

complications, early definitive prosthesis fitting and shorter rehabilitation time. IPOP

is an emotional enhancer since the presence of prosthetic limb aids with better body

image. The disadvantages are mechanical stress, tissue necrosis and wound

dehiscence along with reduced access to wound inspection. To apply an IPOP skilled

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8 PREFABRICATED POSTOPERATIVE PROSTHETIC SYSTEMS (PFPS)

Prefabricated prosthesis are designed for early gait re-education following surgery.

They provide a psychological boost and decrease the time interval for definitive

prosthesis. They are similar to IPOP methods but use pneumatic technology for

socket holding. The residual limb with soft dressing will be lined by air cell, or air

bags which can be inflated and serves as the socket residual limb interface. This can

be inflated up to 20-40 mm of Hg, thus providing excellent external compression.

The advantages are early weight bearing, easy removal and replacement for wound

inspection. It reduces the limb swelling by pneumatic compression. The

disadvantages are expensive, bulky along with difficult donning and doffing.(18–20)

3.2.4

PRE-PROSTHETIC TRAINING

The goal of early post-operative period is functional rehabilitation.

PHYSICAL TRAINING

-

Individualized exercise schedule should be instructed to

improve or maintain the range of motion of all the limbs, to improve the strength of

the limbs and to improve endurance for daily activities.(6)

TRANSFERS AND MOBILITY- In the early phase amputee persons are taught bed mobility, transfers, and mobilization to a chair or wheelchair. Subsequently gait

training is initiated inside the parallel bar and progressed to elbow crutches. The

pre-prosthetic training provides the patient a safe return home with the temporary

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The residual limb will continue to shrink and hence definitive prosthesis fitting will

require 6- 8 months post amputation.(12)

3.3

PROSTHESIS

Prosthesis is a device which substitutes for a missing body part.

3.3.1

HISTORY

Humans for centuries have discovered ingenious ways to replace the lost body part.

The history of prosthesis dates back to Greek and Roman times, with little

advancement in the Dark Ages. In the year 2000, researchers in Cairo, Egypt,

unearthed the oldest documented prosthesis – 3000 year old toe made of wood and

leather. In 1500’s German’s made prosthetic limbs utilizing iron, springs and leather.

French surgeon Ambrose Paré invented transfemoral prosthesis with peg leg and foot

piece, adjustable harness, knee lock control and other engineering features that are

used in today's devices. Lorrain, a French locksmith used leather, paper and glue in

place of heavy iron in making prosthesis, which later became a major contribution in

prosthetic technology. In 1863, Dubois Parmlee invented an advanced prosthesis with

a suction socket, polycentric knee and multi-articulated foot. Following the U.S Civil

War and World War 2 the number of amputations increased astronomically. This

eventually led to the formation of the American Orthotic & Prosthetic Association

(AOPA) for better prosthetic design and technology.(21) Prosthetic devices which

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with new technologies and advancement of prosthetic design. In the last century new

sophisticated prosthesis were developed, with microprocessors and computerized

technologies. The socket fitting also got revolutionized with the introduction of

osseo-integrated prosthesis. (2,21)

3.3.2

BIOMECHANICAL PRINCIPLES OF TRANSFEMORAL PROSTHESIS

The requirements for a good transfemoral prosthesis is basically three in number—

comfort, function, and appearance. The user of the prostheses will not be able to wear

it unless it is comfortable. It should enable the wearer to perform functions with ease.

In addition to the above the prosthesis should be cosmetically acceptable and natural

to the wearer as well. The prosthesis should provide adequate support and a naturally

appearing gait. Hence to ensure that all the 3 functionalities are suitably met, the

correct bio mechanical principles are to be used.

MEDIO-LATERAL STABILITY

Two specific deviations of gait observed in transfemoral amputee persons were.

a) Exaggerated lateral movement of the torso from side to side.

b) Increased step width.

Hence achieving a narrow based gait and adequate medio-lateral stability is crucial

for a transfemoral prosthesis.(22) A normal person walks with a step width

measuring about 2-4 inches whereas in the case of an amputee person’s step width is

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[image:32.612.352.539.237.528.2]

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FIGURE 3-1 - FORCE VECTORS ACTING ON SINGLE LIMB SUPPORT

DEFINITIONS (22, 23)

The center of gravity of the body can be defined as a point within the body at which the effect of all body weight can be assumed to be concentrated. As per the

laws of physics the body weight must be assumed as acting vertically down from this

center of gravity. “The weight line of the body is a line through the center of gravity along which the body weight can be assumed to

act vertically downward at all times.” The total force exerted on the sole of the foot is known as

the floor reaction force which is the load which the leg transmits upwards. The load line can be defined as the line along which the force

between the foot and the floor acts. The support line is defined as a vertical or plumb line, passing through the support point, along

which the effective supporting force between the

socket rim and the residual limb can be assumed

to act.(Figure 3.1)

ROLE OF HIP ABDUCTORS

During midstance the pelvis drops 5 degree in the unsupported side. Further pelvic

drop is prevented by the eccentric contraction of hip abductors. In normal persons

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[image:33.612.356.514.379.595.2]

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FIGURE 3-2 – PELVIS ACTING AS LEVER

controlling the pelvic drop. In case of the transfemoral amputee persons, the residual

femur during weight bearing shift’s laterally since the femur floats in soft tissue mass

without any bony attachment distally.(24) There occurs increase in pressure in the

perineal area due to drop of pelvis towards the normal side, which is uncomfortable,

hence the amputee persons compensates by leaning over the prosthesis which results

in amputee persons’ list or walking with wide base. The gluteus medius has to be

maintained in functional position for providing comfortable and normal gait for the

amputee persons.(25)

THE PELVIC LEVER

As illustrated by the Figure 3.2, while the amputee

person is bearing weight on the prosthesis during

stance phase, the pelvis acts as a lever. The body

weight is supported by the pelvic lever by

balancing action of the hip abductors, using the

ischium as fulcrum. The body weight is balanced

by the tension in the hip abductors whereas the

lever action of the pelvis prevents the dropping of

the pelvis towards the unsupported side.(23)

However this is possible only if the residual limb

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13 DISTRIBUTION OF LATERAL PRESSURE

Distribution of counter pressure uniformly over the lateral side of the socket ensures

stabilisation of the residual limb. If the length of the residual limb is average, then

stabilisation can be achieved by fitting the residual limb over the entire lateral wall.

However if the hip abductors are used for pelvic stabilisation with residual limb not

properly supported against lateral wall, then end of residual limb may get subjected

to intense compressive forces causing pain.

The lateral stabilisation of the pelvis by the hip abductors is influenced by

predominately two factors (22)

a) Lever arm between the abductor and support point – _{The tension in}

abductors has greater advantage when the lever arm is at the lengthiest. If the

ischial seat and gluteal musculature support the body weight substantially then

amputee persons is at ease to balance the body weight.

b) Degree of residual limb adduction in socket - Efficiency of muscles is at

the peak when they are at normal rest length. If the movement of femur is

anticipated and pelvic femoral angle maintained, then the hip abductors are

most efficient.

KNEE CONTROL

Knee stability refers to maintain the knee in extension during the stance phase. Knee

instability happens when the prosthetic knee buckles under load. Excessive knee

stability will lead to difficult swing phase initiation and increased energy

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control. Depending on the age and residual limb condition of amputee persons, a

fine balance needs to be maintained between the degree of involuntary and voluntary

control.

Involuntary Control

If the weight line is anterior to the knee axis, the weight bearing tends to extend the

knee and locks it against the extension stop. Prosthesis can be said to be in a state of

high alignment stability when the socket is placed well forward on knee block or

aligned in hyper extension and knee joint posterior to angle.(22) This is

predominantly required for eliminating the fear of falling. However the limitation is

that the prosthesis being hard, flexibility is limited and normal gait gets

compromised.

Voluntary Control

In order to enable amputee persons to have near normal gait, the use of involuntary

control has to be minimised and voluntary control by residual limb action needs to

be emphasised. The key to voluntary control is effective utilisation of the hip

extensor musculature. For voluntary control, the hip extensors – gluteus maximus

and hamstrings should be able to exert enough force to maintain the knee in

extension. However voluntary control is exercised such that the residual limb should

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[image:36.612.313.515.413.646.2]

15

FIGURE 3-3 - ALIGNMENT STABILITY

INITIAL FLEXION

The hip extensors should be at an optimum resting length for exerting extension force

in the knee. For this the glutei has to be kept stretched. The socket is aligned in initial

flexion to increase the resting length.(Figure 3.3) Hence the amputee persons will

have greater knee stability during walking, as the length of the hip extensors is

increased by hip flexion. This enables the residual limb to exert sufficient force

without any conscious effort by the amputee persons, to keep the knee back against

the extension stop.(24) The transfemoral amputee persons walk with increased pelvic

lordosis if the hip extensors are weak, this can be decreased by keeping the socket in

initial flexion.(22,26) The hamstring muscles in the case of amputee persons with a

well-developed musculature tend to force the ischium off the ischial seat. This causes

tremendous pressure on the muscles and

the anterior brim of the socket. This is

reduced to a great extent by the initial

flexion, by allowing the body weight to be

borne by the hamstring musculature. The

flexibility of the prosthetic knee is

enhanced to a great extent by positioning

the socket anterior to the knee axis as this

allows easy transmission of weight from

the prosthesis to normal leg.

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16 FOOT POSITION

The feet of the amputee persons should be in medial position alignment to ensure

that weight is borne primarily by the ischial seat and the torso list is minimal.

Normally the center line of feet will be aligned below the ischium for an amputee

person. However this may not apply always, as it is dependent on the ability of

amputee persons to use hip abduction. If an amputee person has a very short

residual limb, then excessive dependence on the abductors may result in pain and

will force him to lean over the prosthesis and walk with wider base. (23)

DYNAMIC ALIGNMENT

The forces acting on the prosthesis in the case of an amputee person varies with the

different phases of gait. The dynamic forces will greatly influence the behaviour of

the prosthesis during the swing phase as well as stance to swing and swing to stance

phase. The pre requisite towards achieving a smooth swing phase is good transition

from the stance to swing phase.(27) When the alignment stability of the prosthesis

is high the initiation of the swing phase will be delayed and the energy required is

high. Swing phase vaulting happens when the prosthesis is too long. The lateral

knee movement along with medial foot movement of the prosthesis caused by poor

dynamic alignment is known as the whip of the prosthesis.(26)

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17 ROTATION OF KNEE AXIS

Extensive studies on human locomotion have indicated that during motion, when

the knee is brought forward by hip flexion the femur rotates by 40_{on an average.}

This medial rotation of the femur will result in lateral displacement of the feet. In

order to overcome this medial rotation of the femur on hip flexion, the knee axis is

also rotated laterally.(22)

ANKLE – FOOT - DYNAMICS

The most unstable phase of an amputee persons’ gait is ‘heel strike’. When the heel

of an amputee person contacts the ground, knee flexor moment is produced causing

the knee to buckle. In normal gait the controlled plantar flexion will stabilize the

knee. In transfemoral prosthesis the stiffness of plantar flexion is the most

significant factor affecting the knee stability. If the ankle is too stiff then, the feet is

not allowed to rotate forward to a flat stable position. This will cause the knee to

buckle on the transfer of weight to prosthesis. On the other hand if the plantar

flexion stiffness is not sufficient then the feet will have a tendency to slap at the

heel contact. Hence the key is to have a proper balance for each amputee

person.(26)

3.4

COMPONENTS OF TRANSFEMORAL PROSTHESIS

Transfemoral prosthesis is constituted by suspension systems, socket, knee joint,

(39)

18

3.5

SUSPENSION SYSTEMS

A prosthesis can be suspended using many methods like belts, liners, suction and

vacuum suspension.

Belt Suspension - Three different types of belt suspensions are used for a transfemoral prosthesis i.e. total elastic suspension belt, silesian belt and pelvic band

with hip joint.(12)

Elastomeric Liner Suspension - Liner suspension can be used either with pins / lanyards. The liner suspension with either pin / lanyard type has advantages like

increased shear control, cushioning, and greater suspension and comfort.(28)

However these liners require frequent replacement, add bulk and pose hygiene

challenges.

Suction Suspension– In this mode of suspension, air is only allowed to exit & not enter by placing a single side valve near the distal region. On placing the limb in the

socket, the sock is pulled out thereby sliding the limb in the socket. This can be

achieved by use of special nylon socks, elastic bandage or wet fit method. While the

suction suspension is the most secure of all suspensions, it has certain disadvantages

like it is difficult to don.(29) Moreover any weight gain may result in adductor roll,

(40)

19 Vacuum Suspension system - Vacuum systems are new and advanced version of the suspension systems which use an active mechanism to expel air from inner socket.

These systems require both gel liner and sealing sleeve and the air is removed and

vacuum achieved through a mechanical / electric pump. This provides for better

suspension, maintains the limb volume and increased tissue oxygenation in the

residual limb.(30) However the disadvantage of the system is that the vacuum seal is

lost if a hole is formed on the sleeve. Moreover the cost as well as the weight of the

device is increased on account of this.

3.6

SOCKET

Introduction

Socket is the human prosthesis interface. Earlier design of the transfemoral socket

was wooden socket with a conical interior shape – plug fit. The weight of the

amputee person was transferred through the thigh muscles. The quadrilateral socket

design which provided ischial-gluteal weight bearing was introduced in 1950s. In

1980s a second generation of transfemoral sockets – the ischial containment socket

emerged due to the work of Long, Mayfield and Sabolich. The socket evolution

continued and newer socket design like Marlo Anatomical System developed. By the

end of 19th century direct bony anchoring of the prosthesis – Osseo-integrated

(41)

20

3.7

QUADRILATERAL SOCKET

“The quadrilateral socket is truly more than a cross sectional shape at the ischial level, is a three dimensional receptacle for the residual limb with contour at every level which are justifiable on a sound biomechanical basis” -RADCLIFFE

Quadrilateral (QUAD) socket was introduced in 1950, by University of California at

Berkeley. It has been the standard socket design for transfemoral prosthesis for about

four decades. Quadrilateral socket has four distinct walls, hence the name. The

medio-lateral diameter is increased and the antero-posterior diameter is shortened. It

has posterior shelf on which ischium rests. The primary weight-bearing surface is the

ischial tuberosity and the gluteal muscles. Hence it’s an ischial gluteal weight bearing

prosthesis in which 83 % of the weight is borne by ischium and gluteal

musculatures.(23,33)

The lateral wall is higher than the posterior wall. The lateral wall primarily stabilizes

the femoral shaft and encloses the gluteus maximus, vastus lateralis and tensor fascia

lata. The lateral wall is kept in adduction and this stretches the hip abductors. The

medial wall is perpendicular to provide counter pressure. It stabilizes the residual limb by compressing the abductor muscles against the lateral wall. The posterior

wall contains hamstring medially. The hip is kept in flexion by anterior slant of about

7 -10 degrees. This will stretch the gluteus and hamstrings for maximum power

generation. The anterior wall is higher than the posterior wall. It stabilizes the

(42)

21 and it presses against the Scarpa’s triangle.(22,23,33) Distally the socket provides the total contact. Quadrilateral socket provides good stability in the sagittal

plane.(34) The medio-lateral and rotational stability is minimal. The quadrilateral

socket has a better fit with firm, long residual limbs with good adductor

musculature.(24)

3.8

ISCHIAL CONTAINMENT SOCKET

3.8.1

EVOLUTION

The Quadrilateral socket was the socket design of choice till 1980’s.(25) Ivan Long

and Mayfield investigated the performance of the quadrilateral socket in regard to

coronal-plane residual limb-socket biomechanics. They radiologically evaluated 100

transfemoral amputee persons standing erect in quadrilateral socket and found that

majority of them; the femur in residual limb was in abduction. There were gait

deviations like lateral bending of trunk and wide based gait.(35,36)

THE PROBLEM

Considering pelvis as a lever, the ischium as the fulcrum, the hip abductor tension

should be able to balance the weight of the body, preventing the pelvic drop during

stance phase of prosthetic limb. For the maximum physiological efficiency of the

abductors, the normal rest length should be maintained. (Figure 3.4) If not it will lead

to abductor insufficiency. (22) In quadrilateral socket when gluteus medius contracts,

(43)

[image:43.612.210.492.110.278.2]

22

FIGURE 3-4 HIP ABDUCTOR INSUFFICIENCY

maintain femur in adduction. The abduction of femur is mainly due to the wider

medio-lateral dimension of quadrilateral

socket. The abduction of the femur causes

more pressure on the distal aspect of the

residual limb.(Figure 3.5) When the

prosthetic side is bearing weight the residual

limb exerts force on the lateral wall which

shifts laterally since the ischium cannot check this displacement. When gluteus

contracts and abducts the femur the pelvis shift medially which makes the lateral

shift worse and cause high shearing force in the soft tissue around the ischial seat and

medial brim.(37) The lateral wall of the socket

is away from the lateral surface of thigh

except in the distal part. This lateral shift of

the socket results in a gap in the proximal

socket – limb interface. The lateral shift of the

socket resulted in compressive forces in the

medial proximal tissues of the limb. This

creates a shearing force in the soft tissue structures between medial brim and medial

structures of pelvis. Thus the quadrilateral socket exerts high pressures in proximal

medial and posterior brim.(37) This in turn results in pain and discomfort in the

[image:43.612.325.510.379.548.2]

(44)

23

trunk leaning gait.(Figure 3.6)(39) The biomechanical disadvantage of the

quadrilateral socket is more pronounced with shorter residual limb.

Goals of new socket technology were

1. The hip abductor to be maintained in its normal length.

2. The femur to be maintained in physiological position of

adduction.

3. The pressure in the distal lateral aspect of the residual

limb to be distributed for a painless and comfortable gait.

4. The lateral shift of the socket to be controlled

5. Pain and discomfort in the perineal area to be alleviated

6. The gait deviations to be minimized

7. The energy efficiency of the gait to be improved

EMERGENCE OF ISCHIAL CONTAINMENT SOCKET

Initially the alignment modification was tried. The newer alignment techniques were

focused on maintaining the femur in adduction. The head of the femur was aligned to

the center of the medio-lateral dimension of the socket. Ivan Long proposed Long’s

Line-”a straight line from the head of the femur (located approximately at the center

of a narrow socket), through the distal femur, and down to the center of the heel”.

[image:44.612.397.510.186.473.2]

(45)

24

alignment. The ischial seat, knee joint and foot should be perpendicular to the Long’s

line. The knee joint was placed laterally in order to avoid the knocking of knees.

Alignment modifications were followed by socket design alterations. To maintain hip

adduction the lateral wall was contoured with sloping medially from sub trochanteric

region to distal end of the socket. To achieve this alignment the medio-lateral

dimension was reduced. This lead to the emergence of the narrow medio-lateral

socket concept. The newer socket alignment method came to be known as Proto

ischial containment limb (Figure 3.7).(40) Femoral alignment, balance and gait

improved with new alignment method.(35,38,40)

Even though the alignment modifications were made, during weight bearing the

ischial tuberosity migrated medially. This resulted in the lateral gap in the proximal

brim of the socket along with medial wall digging inside and lateral leaning of pylon.

Hence amputee persons had pain and discomfort in the perineal area.(39) To maintain

the hip in adduction and for better comfort in the perineal region alignment

modification alone was not sufficient. Hence alterations in socket design were tried.

This lead to the emergence of the ischial containment socket with newer socket

design and alignment technology. It is an evolutionary design rather than a

revolutionary design.(23, 24) The ischial containment socket refers to postero-medial

extension of the proximal brim of the socket, so that the weight is borne against the

(46)

[image:46.612.73.536.97.416.2]

25

FIGURE 3-7 PROTO ISCHIAL CONTAINMENT SOCKET ALIGNMENT

Original Source – King. C, 2009 (40)

The postero-medial brim is oblique and sloping and the ischium is contained in it and

hence the name. Along with this there is contouring beneath the ischial tuberosity

resulting in the same amount of ischial weight bearing as quadrilateral socket.(39)

Radcliffe named this newer socket design as Ischial Ramal containment.(24) The

(47)

26

The femur is kept in adduction in the ischial containment socket by two methods.

1. The ischial tuberosity and ramus is held inside the socket. That will bear the forces

which are directed laterally. The lateral surface of the socket proximal to the

trochanter is snugly fit into the soft tissue. The ischium and ramus is held in position

by the medially directed forces borne by the proximal femur in the trochanteric and

sub-trochanteric region. The medially directed forces in the mid and distal femur help

in maintaining proper adduction angle. The ischial containment is like a locking

system in which ischium sits inside the socket and the opposing force is given from

the lateral aspect pushing the femur into adduction. The three point pressure system(

Figure 3.8) - laterally directed forces in the ischial tuberosity, the medially directed

forces in the supra-trochanteric region and the medially directed forces in the lateral

aspect of femur along with the bony lock maintains femur in adduction. The

increased adduction angle in ischial containment socket results in considerable

weight bearing by the femur. (24, 39)

2. The narrow medio-lateral dimension will lock

the femur, maintain the hip in adduction. Since the

medio-lateral dimension is narrow the weight is

borne directly by the skeletal structures, reducing

the motion lost through soft tissue interface. A

wide medio-lateral dimension cannot provide this

[image:47.612.357.505.485.663.2]

locking phenomenon since the femur can fall away

(48)

27

from the supporting surfaces. The antero-posterior dimension is widened to

compensate the narrow medio-lateral. Increasing the antero-posterior diameter allows

flexors and extensors which form the major muscle bulk around the hip to function

naturally.(23,39)

The rotational stability of the quadrilateral socket depends mostly on muscle

channels. In ischial containment socket the containment of the ischium and narrow

diameter between the greater trochanter and medial ischial surface provides sufficient

rotational stability.(24) Ischial containment is contoured throughout for total contact

socket. Since more area of the residual limb is contained inside and due to the

contour, it provides greater distribution of weight bearing and stabilization forces.

(34) The weight bearing in ischial containment socket is by ischial tuberosity, gluteal

musculature, femur and hydrostatic compression.(23)

The ischial containment is the socket design of choice for short, fleshy and unstable

residual limb. For functionally active amputee persons and high activity sports ischial

containment is the preferred socket design. For elderly debilitated patients walking

with walking aids quadrilateral socket will be sufficient.(24)

3.8.2

DIMENSIONS

MEDIAL-LATERAL DIMENSION

The ischium sits inside the postero-medial socket wall. To prevent the ischial ramus

(49)

28

side. This is achieved by reduction in the medio-lateral dimension of subtrochanteric

region. The proximal region is wide enough to accommodate the ischial ramus as

well as greater trochanter. Hence the medio-lateral dimension of ischial containment

at the ischial level is similar to quadrilateral socket. The decrease in the medio-lateral

dimension is mainly 4 cm distal to ischial tuberosity in the subtrochanteric

region.(23). The lateral wall is well above the greater trochanter for medio –lateral

stability. The lateral wall is slanted medially for better adduction.

ANTERIOR-POSTERIOR DIMENSION

The medio-lateral dimension is narrow, in order to accommodate the residual limb

volume the antero-posterior dimension is greater compared to quadrilateral socket.

The major muscle bulk acting in the hip joint is in the sagittal plane. Hence wider

antero-posterior dimension allows the flexors and extensors to function more

effectively (36, 37). Wider the antero-posterior dimension lesser will be the pressure

on Scarpa’s triangle.(39)

MEDIALBRIM

The postero-medial socket wall provides lateral pressure to the ischium in order to

prevent it from slipping medially. Hence the medial wall has to be loaded, while

providing pressure relief for the less pressure tolerant areas like adductor tendon and

pubic ramus. The medial brim extends posterior to enclose ischial ramus and dips

(50)

29

ischium from posterior to anterior direction, hence in the transverse plane it looks

internally rotated.(23)

ANTERIOR BRIM

The anterior trim line of ischial containment and quadrilateral socket is similar, up to

or just proximal to the inguinal crease. While sitting the socket should clear the

superior iliac spine. (23)

LATERAL BRIM

The lateral wall is extended proximally snugly fitting to provide counter pressure for

the ischium in the sloping medial wall. The contouring helps to distribute the

pressure over the entire area. In transverse plane posterior to greater trochanter, there

is extreme obliquity compared to quadrilateral socket. This is termed as wallet

hollow. The postero-lateral brim compresses gluteal muscles and helps in gluteal

weight bearing. Lateral brim locks around the greater trochanter & provides rotatory

stability.(23)

POSTERIOR BRIM

The posterior trim line of the ischial containment socket is 4 cm proximal to the

ischial tuberosity, higher than the quadrilateral socket in order to contain the

(51)

[image:51.612.65.549.115.638.2]

30

TABLE 3-2 COMPARISON OF QUAD & IC SOCKET

QUAD IC

Ischial containment Ischium is outside the socket resting in the ischial seat

Ischium is contained inside the socket in the postero-medial wall Weight bearing Ischial – Gluteal weight

bearing

Ischial tuberosity, ramus, femur and

hydrostatic compression Medio – lateral stability No bony lock, less

medio-lateral stability

Hip maintained in adduction with bony lock and contoured lateral wall, greater medio-lateral stability Rotational control Lesser rotational control

since ischium slips from the posterior shelf

Increased rotational control due to skeletal lock inside the socket Socket Shape Wider medio-lateral,

narrow antero-posterior

Narrow ML, Wider antero-posterior,

subtrochanteric concave shaped

Alignment Medial wall in line of progression

(52)

31

The ischial containment sockets were known in different names. The prosthetic

technique of University of California was named as CAT-CAM. The socket design

followed in Northwestern University was NSNA (Normal Shape-Normal Alignment

technique). In New York University it was known as Narrow Medio-lateral.(25)

3.8.3

NSNA (NORMAL SHAPE-NORMAL ALIGNMENT TECHNIQUE)

Long found that when foot is lined under femur head rather than ischium, the

amputee persons walk with a near normal narrow base. He proposed Long’s Line and

the alignment in NSNA is mainly based on it.

3.8.4

CAT-CAM (CONTOURED ADDUCTED

TROCHANTERIC-CONTROLLED ALIGNMENT METHOD)

The Contoured Adducted Trochanteric-Controlled Alignment Method is an ischial

containment socket developed by Sabolich. This design keeps the femur in adducted

position by undercutting of the trochanter. The ischium sits in special fossa in the

posterior wall, with a three dimensional support in the socket, thus forming a bony

lock.(24)

The prosthetic foot is lateral to the plumb line from the ischial tuberosity. In

variation to NSNA the foot is not always under the distal femur or center of hip joint.

In the geriatric population CAT – CAM offers superior comfort due to less pressure

in the Scarpa’s region.(39) The CAT-CAM socket offers more comfort due to

(53)

32

3.8.5

NARROW M-L (NARROW MEDIO-LATERAL SOCKET)

Narrow Medio-Lateral socket is a type of ischial containment socket. Here the

casting techniques are slightly different. The centralization of femur is achieved by

applying laterally directed forces in the medial distal end of residual limb, while

maintaining femur in adduction with a medially directed force applied on the middle

of the femur shaft. This will provide a distraction force displacing the soft tissue

mass in the distal aspect of residual limb, resulting in centralization of femur and

better contour of the end region of the residual limb.(25)

3.8.6

SCAT-CAM (SKELETAL CONTOURED ADDUCTED TROCHANTERIC

CONTROLLED ALIGNMENT METHOD)

Skeletal Contoured Adducted Trochanteric-Controlled Alignment Method is a

modified form of CAT–CAM in which skeletal anatomy is considered more. The

femur is kept in adducted position with Oklahoma fossa and compartment. The

medial brim line is advanced proximally to contain the maximum of the ischium and

the ramus.(39)

3.9

OTHER SOCKET DESIGNS FOR TRANSFEMORAL

PROSTHESIS

The prosthetics and orthotics is a developing field of science. The newer sockets are

being developed with advanced technology to meet the variety of needs of the

(54)

33

3.9.1

FLEXIBLE SOCKETS

"To label a socket as flexible I would say that you should be able to deform it by your hands, and the material should not be elastic enough to stretch under the loads it will be subjected to." - KRISTINSSON

The flexible socket design concept is introduced by Ossur Kristinsson. The design

was popularly known as Scandinavian Flexible socket or ISNY (Icelandic Swedish

New York) socket. The socket is formed by a flexible thermoplastic which is

supported by a rigid frame. The flexible socket materials are made of laminating

resins like polyurethane, polyester, acrylic, silicone, lynadure, surlyn along with

nylon stockinet with fiberglass stockinet in between. The rigid frame or socket

retainer should be of enough strength to support the residual limb and to resist

deforming forces. The socket retainer is mainly made of carbon fiber. The

suspension system for flexible sockets is mainly vacuum suspension. If needed other

suspension methods can be incorporated.(41–43) The advantages of flexible socket

design is maximal comfort, better proprioception and ability to accommodate minor

(55)

34

3.9.2

MARLO ANATOMICAL SOCKET

Marlo Ortiz Vasquez a Mexican prosthetist developed the Marlo Anatomical Socket

(MAS). Marlo Anatomical socket is an ischial ramal containment socket. It deviates

from ischial containment socket by lowering the posterior and anterior timelines. The

ischial ramus is contained inside the socket which provides the skeletal stability. The

medial and anterior portion of ischial tuberosity and ramus is captured inside the

socket with less of posterior aspect of ischial tuberosity. The posterior trim lines are

lowered so that the gluteus maximus is not included in the socket. The anterior trim

lines are also correspondingly lowered. The lateral trim line above the trochanter is

snugly fit and is lower compared to ischial containment socket. MAS is a total

contact socket and the vertical forces are mainly borne by the ischial ramus along

with quasi hydrostatic suspension. Its mainly designed like a flexible socket with

socket retainer made of carbon. The advantages are better cosmesis, easy donning

and doffing, improved proprioception along with more natural sensation of sitting

since there is no socket material beneath the gluteus maximus.(44) The amputee

persons gait is better with MAS socket due to superior containment of bony structure,

and improved range of motion of the hip.(45) The femur is kept in adduction and the

pelvis stability is improved with MAS socket. In comparison to the ischial

(56)

35

3.9.3

OSSEOINTEGRATION

The osseointegration is a newer and alternative method of attaching prosthesis to

human body. The concept of osseointegration dates back to 1960s when it was found

that titanium is bone friendly. Further research by Swedish Professor Branemark lead

to the use of osseointegrated implants in the dental surgery. The concept was

expanded in 1990s and the transfemoral amputee persons were fitted with

osseointegrated system. In this the prosthesis is directly anchored to the bone. This

requires two stage surgical procedures. In the first stage implant which is a threaded

titanium material is inserted into the marrow cavity of residual femur. This is known

as fixture. This fixture will get integrated to the bone with time. The second surgery

is conducted after six months. The abutment which is a titanium extension is inserted

into the fixture and secured with abutment screw. The abutment penetrates the skin

and protrudes out. The rest of the prosthetic components can be directly fixed to the

abutment in the following phase of comprehensive rehabilitation. This leads to a

gradual and progressive weight bearing of the prosthesis. The entire rehabilitation

will take 6 months for proper weight bearing and gait training. So from amputation to

independent walking with the osseointegrated prosthesis will require a minimum of

one year. The osseointegrated prosthesis the hip range of motion is not restricted

unlike the other sockets.(45) The cumulative survival rate, prosthetic use and

mobility is better with osseointegrated prosthesis.(47) Two years follow up of

transfemoral amputee persons with osseointegrated prosthesis showed better quality

(57)

36

energy consumption with osseointegrated and conventional transemoral prosthesis.

They found that amputee persons with osseointegrated prosthesis walk with higher

speed and lesser energy expenditure.(49)

The advantages of the osseointegrated prosthesis are. 1. Since there is no socket, the

discomfort, skin irritation, sweating, concentrated pressure and pain occurring in the

human- socket interface can be avoided. 2. The prosthesis can be easily detached

from the abutment. Hence donning and doffing is easy. 3. The suspension is good,

since it is directly anchored to the bone. 4. The hip movements are not restricted

since there is no socket wrapped around the residual limb. 5. The more natural

perception of the prosthetic limb, which is known as osseoperception.(50)

The disadvantages are 1. Need for extensive rehabilitation and longtime interval

between amputation and prosthetic walking. 2. Risk of implant related complications

like infection, implant loosening and failure. 3. Risk of fractures. 4. Permanent

abutment can lead to poor cosmesis. 5. High impact activities like running and

jumping are restricted. 6. Regular skin care for the abutment area is required.

3.10

KNEE JOINTS

Prosthetic knee joint is a complex structure which forms the integral part of the

transfemoral prosthesis. The prosthetic knee can be endoskeltal or exoskeltal. The

knee joint provides adequate support during the stance phase, preventing the failing

(58)

37 SINGLE-AXIS KNEE JOINT(12) - This is the basic or simplest knee joint which works

on a simple hinge mechanism. The stance phase stability is dependent on involuntary as

well as voluntary stability. The advantages are being simple, low cost and easy

maintenance. The disadvantage is compromised mechanical stability.

POLYCENTRIC-AXIS KNEE JOINT(26) – In Polycentric knee the instantaneous center

of rotation changes with respect to flexion and extension of thigh and shank component.

The polycentric knee mainly consists of four bar linkage. The advantage is varying

mechanical stability through the entire gait cycle. During flexion of the knee, there is

inherent shortening which aids in better foot clearance. The polycentric knees are

beneficial for amputee persons with weak hip extensors, short residual limbs and knee

disarticulation.

WEIGHT-ACTIVATED STANCE-CONTROL KNEE(26,27) – It consists of a braking

mechanism which prevents knee from buckling. This brake is activated by applying

weight. The weight required to activate this mechanism can be modified according to

each individual.

MANUAL LOCKING KNEE JOINT(12,26) – This has an automatic locking mechanism

which is activated in extension. This can be unlocked manually. This is the most stable

knee during stance phase. The disadvantage is maximal gait deviations and increased

(59)

38 FRICTION CONTROL KNEE JOINT(12,27) - A constant mechanical friction is applied

to the knee joint. The friction is adjusted to the normal cadence of the amputee persons.

Alteration in cadence by the amputee persons can result out of phase flexion and

extension of knee joint. The advantages are simple design, dependability and easy to

maintain. The disadvantage is amputee persons have to walk with single cadence.

EXTENSION ASSIST KNEE JOINT(26)– It helps in extending the shank in swing phase

by recoil of a spring mechanism which is being compressed while flexing the knee. It

provides initial stance support since full knee extension is ensured at the end of terminal

swing itself.

PNEUMATIC CONTROL KNEE JOINT (12,26)– Pneumatic knee contains a piston,

which is compressed during the knee flexion. This forces the air in the cylinder to travel

upwards through bottom valve and then back to the central cylinder through another

valve

Comparative study of ischial containment socket and quadrilateral socket for functional ability in persons with unilateral transfemoral amputation.