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        ALIGNMENT METHODS OF ABOVE KNEE PROSTHESIS

                                                                                                                              By-Sibasis pattanayak

                                                                                                                        student,NILD,KOLKATA

ALIGNMENT:-The geometrical (angular and linear) relationship between socket,knee joint,foot and ankle complex is known as alignment.

There are different types of alignment method.

Mostly used methods are;

(1)BENCH ALIGNMENT 

(2)STATIC ALIGNMENT

(3)DYNAMIC ALINGNMENT

1-BENCH ALIGNMENT:-

                                       A-Initial socket flexion

                                       B-Initial socket adduction

                                       C- Anterior-Posterior

                                       D-Medio-Lateral

A)Initial socket flexion:-The initial socket flexion of 5 degrees is generally provided for following purposes.

1.It activates the hip extensors.

2.Knee stability

3.To sit the ischial tuberosity on the posterior brim of the socket.

4.To prevent excessive lumbar lordosis.

B)Initial socket adduction:-(7 degrees of adduction is provided)

1.It maintains the adductor muscles of the hip.

2.It gives pelvic stability.

3.It maintains width of walking base with normal range.

4.It is cosmetically well accepted.

C)A-P ALIGNMENT:-

                            (1)GERMAN SYSTEM (AIR SPACE)

                            (2)U.S. SYSTEM (T.K.A)

                            (3)MODIFIED SYSTEM (M.K.A)

(1)GERMAN ALIGNMENT SYSTEM:-In german alignment system because of the presence of air space the plumbline draw from the mid of the lateral wall of the socket fall at the bisector of the foot keeping the knee centre well posterior with respect to plumb line.

(2)U.S SYSTEM:-(T.K.A)  TROCHANTER -KNEE-ANKLE

In TKA system of alignment -the trochanter and ankle line passess 1/2 inch anterior on that line or slightly posterior with respect to knee axis.

This alignment method is useful in the case of SHORT to MEDIUM stump,LONG stump VERY LONG STUMP or knee disarticulation.

 (3)MODIFIED SYSTEM(MKA):-Mid of the medial wall of the socket in MKA system of alignment the mid of the medial wall of the socket,knee and ankle are kept on the same line.To keep the in 5 degrees of external rotation the lateral location of the knee bolt pass 5 degrees posterior w.r.t. location of previous reference line in transverse plane.

(4)M-L ALIGNMENT:-In M-L alignment the plumb line drawn from the ischial tuberosity level should fall between the knee axis and centre of the heel ,this remains constant for all the system of alignment .

Alignment Considerations:-

The transfemoral alignment considerations in his statement that the artificial limb 

“… must provide both adequate support and a natural-appearing gait 

with as modest consumption of energy as possible.” 

These standards have not appreciably changed.

 Prosthetists at-tempt to create a stable and effective transfemoral gait 

pattern with proper socket fit; effective suspension; and 

diligence in bench, static, and dynamic alignments.  

ALIGNMENT PARAMETERS:-

•  The socket is generally set in a flexion angle  greater than

 the individual’s maximum hip extension.

• This orientation is especially important for proper fitting of IC sockets .
• With the socket in the proper ori-entation, the focus is on the placement of 
• the prosthetic knee and foot. 

In able-bodied individuals, coronal alignment of the hip joint is

 typically directly over the knee and ankle joints 

(Figure 3, A). 

For initial bench alignment of the transfemoral prosthesis,

 the actual hip joint cannot be used as a ref-

erence point because it cannot be located on the prosthetic socket.

 However, locating a point on the socket brim that is 1 inch (2.54 cm) lateral

 to the location of the ischium will provide a reasonable 

approximation.

 The prosthetic knee and ankle joints are placed directly

 below this identified point. The initial coronal 

bench alignment allows for stability.

SAGGITAL PLANE ALIGNMENT 

Attachments area

Illustrations show the process of initial sagittal alignment

 of the prosthetic trochanter-knee-ankle. 

A, Lateral view of anatomic alignment in the sagittal plane.

 The hip joint is placed over the knee joint and over the ankle joint.

B, The trochanter-ankle reference line. t = the approximation

 of the position of the anatomic hip joint center.

 This point can be reasonably estimated by bisecting the socket, 

but it does not necessarily represent the anatomic placement of the trochanter.

 a = ankle joint or the functioning position of the 

ankle joint recommended by the manufacturer for the selected prosthetic foot.

 C, The location of the prosthetic knee joint center (k)

 is shown in alignment with the trochanter-ankle line. 

D, The knee center of the prosthetic knee has been

 moved posterior (arrow) to the trochanter-ankle line to

 achieve a more stable alignment. This is considered 

a voluntary alignment. 

E, The knee center of the prosthetic knee now 

positioned anterior (arrow) to the trochanter-ankle

 line creates a more unstable alignment. 

This is considered an involuntary alignment.

 F, A completed transfemoral alignment is shown

 with the initial socket flexion angle (black line) and

 the connecting pylons from the socket to the knee to the foot.

IMAGE CREDIT:-Atlas of Amputation and limb deficiencies(latest edition)

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