Quadrilateral Socket

Quadrilateral Socket was developed in UCBL.

Ischial Tuberosity and gluteals are the two wt. bearing areas in Quadrilateral Socket.

Socket Orientation -

1. It has four walls - anterior, posterior, medial and lateral. 

Lateral wall is the highest while medial wall is the lowest. Posterior wall has posterior shelf or the ischial seat. 

Lat. Wall = Posterior Shelf Level + 2 to 2.5'

Ant. Wall = Shelf + 1.5'

Med. Wall= Shelf - half inch.

Position of Ischial tuberosity on posterior shelf is 1" lateral to the medial wall.

2. It has four corners to accommodate four group of muscles.

Antero-medial = adductor longus

Antero lateral = rectus femoris  

Postero medial = hamstrings

Postero lateral = gluteus maximus.

3. Medial-lateral diameter is more than Antero-posterior diameter.

     i.e. ML > AP

This is due to pressure given on the anterior wall.

Indications-

1. Longer residual stumps.

2. Patient having high voluntary control.

3. Previous Users.

Control and stability of Quad. Socket-

AP Control- 

Anterior wall creates a pressure on Scarpa's Triangle to put the Ischial Tuberosity on the Ischial Seat or Posterior Shelf.

In short stump pressure is given on the deepest point of Scarpa's Triangle but in long stump whole anterior wall can be loaded.

Location of Scarpa's Triangle-

On anterior wall,

1. Draw a horizontal line at level of posterior shelf.

2. Divide the horizontal line by drawing two vertical line in medial , middle and lateral part.

3. From intersection point of horizontal and medial line move 1 inches ahead and from this point move one and half inches upward and name this point A and move four inches down and name this point B.

4.  From point of intersection of lateral and horizontal line move 2 inches above and name this point C.

5. Join point A,B and C the triangle thus formed is Scarpa’s Triangle.

ML Control-

 Normal femur is in adduction but the transected femur has more tendency to go in abduction. Due to which the distal femur hits the lateral wall of the socket. 

Abduction of femur is countered by flattening the lateral wall.

Drawbacks of Quad. Socket - 

1. Lateral socket displacement during midstance due to wider ML.

   

     Wide ML diameter of Quad. Socket allows the socket to displace laterally during midstance. This increases pressure to the perineal tissues & decreasing the efficiency of gluteal medius muscle. 

 

 Socket displacement also reduces pelvic stability .

2. No bony lock so lesser rotational control.

3. Lateral trunk bending

  Many quad users walk with extremely wide base gait.

  Wide base gait leads to trendelenburg or gluteal medial limp which causes individuals to lean on the amputed side.

4. Slipping of Ischial Tuberosity inside the socket.

During terminal stance IT slips inside the socket as socket extends while pelvis remains vertical. But this problem can be prevented by giving 5° initial flexion. 

5° flexion also avoids further lumbar lordosis. 

Abduction of femur inside the socket results in medial displacement of IT which is the major drawback of Quad Socket . So there's a need to contain the Ischial Tuberosity within the socket then there comes Ischial Containment designs.