Historic below knee Prosthesis
Consists of a leather thigh corset + side bars+
open ended socket.
Weight bearing is carried on the residual limb
and through the suspension mechanism.
Advantages
The
thigh corset supports some of the weight bearing. Prevent
hyperextension at the knee. Provides
lateral-medial stability. The
socket is cooler than the total contact PTB because of lack of total contact
pressure.
Disadvantages
Edema, Bulky
and heavily, Uncosmetic, Atrophy, Relative
motion causing
irritation, Ischemia, The
hinge breaks frequently and abnormal gait.
Slip Socket Prosthesis
Design to minimize relative motion between the
socket and skin. The socket is either elastically suspended from
the sidebars or is attached to shank by a compression spring. The socket can rotate and piston up and down. Is used for only for those people with short or
tender limb.
ADVANTAGES
The
amputee with the slin graft can ambulate early. It
preserves the knee joint.
DISADVANTAGES
Uncosmetic, Bulky
and heavy, Produce
atrophy, Tear
of clothing, Walk
more like an A.K
amputees.
PATELLAR TENDON BEARING
Was developed at the University of California
(1959). More intimate fit and more efficient than historic. Total contact socket(prevent edema). Weight on patellar tendon.
Laminated/moulded Medial/lateral walls higher then the anterior. wall for Medio-lateral stability. Thigh corset is used for suspension
ADVANTAGES
Total contact design. Improve circulation of the stump. Prevent edema formation. To distribute the W.B. Better proprioception. Lighter than the historic. More freedom of movement than the thigh corset. More cosmetic gait. Gait looks essentially normal except for the
lack of push off. More cosmetic. Easier to don and remove. Require less time for fabrication.
DISADVANTAGES
Require more critical fit. Excessive perspiration is needed. There is a tendency for the amputee to
hyperextend the knee. Frequent readjustments may be necessary.
K.B.M (Kondylen Bettlung
Munster)
It is modified form of
patellar tendon bearing type of socket which has all the advantages of
the P.T.B type
and is modified to avoid the disadvantages.
Total contact is provided in KBM type socket. Medial supra condylar wedge is provided for
suspension. Triangular in shape for proper contact. Weight is distributed mainly on patellar tendon,
medial and posterior flares of the tibia counter pressure are provided by the
high popletial wall and from lateral flare of tibia.
Suspension prosthesis (Sc/sp)
Advantages
Better M_L stability is available in Sc/Sp type prosthesis. Also called supra condylar and supra patellar
type. The patellar shelf is less pronounced in the PTS
than in the PTB. Suitable for short stump: <7.5cm. Less restrictive & Easier to don. Prevents genu recurvatum. Cosmetically good.
Disadvantages
The prosthesis tend to slip down when the knee
is flexed 90. Patellar enclosure may inhibit extreme knee
flex. Is not suitable for long stump. Difficult for obese limb.
Posterior brim
The posterior brim is generally 0.6 to 1.3 cm
(1/2 to ¼ in) higher than the patellar shelf tendon shelf. For very short limbs the posterior brim may be
so high that flexion is limited to 60 degrees.
Anterior brim
The anterior brim comes to the midpatellar
level.
Medial and lateral brim
Medio-Lateral brims come to about the level of
the proximal edge of the patella. The proximal aspect of the medial and lateral
walls supports the femoral condoyle and is usually 6.5 cm (2.5in) above the
medial tibial plateau in height.
Ultralight below knee
Socket:
P.P is vacuum-formed.
Foot:
A sole and
heel cushion like that used with any SACH can be used for it.
Advantages:
Require less energy to walk. Less pistoning and Can be worn in and around water
Disadvantages:
Not durable and Difficult to modify.
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