Fracture of Patella

7/27/2019 Fracture of Patella

1/22

FRACTURE OFPATELLA


2/22

Anatomy

The patella is a sesamoid bone in continuity

with thequadriceps tendon and the patellar

ligament (also called the patellar tendon).

There are additional insertions from the vastusmedialis and lateralis into the medial and

lateral edges of the patella.


3/22

The extensor strap is completed by the

medial and lateral extensor retinacula (or

quadriceps expansions), which bypass the

patella and insert into the proximal tibia.


4/22

The mechanical function of the patella is to

hold the entire extensor strapaway from the

centre of rotation of the knee, thereby

lengthening the anterior lever arm andincreasing the efficiency of the quadriceps.


5/22

The key to the management of patellar

fractures is the state of the entire extensor

mechanism. If the extensor retinacula are

intact, active knee extension is still possible,even if the patella itself is fractured.


6/22

Mechanism of injury and

pathological anatomy

Direct injury usually a fall onto the knee or a

blow against the dashboard of a car causes

either an undisplaced crack or else a

comminuted (stellate) fracture without severedamage to the extensor expansions.


7/22

Indirect injury occurs, typically, when

someone

catches the foot against a solid obstacle and,

to avoid falling, contracts the quadricepsmuscle forcefully. This is a transverse fracture

with a gap between the fragments.


8/22

Clinical Features

Following one of the typical injuries, the knee

becomes swollen and painful. There may be

an abrasion or bruising over the front of the

joint. The patella is tender and sometimes agap can be felt.


9/22

Active knee extension should be tested. If the

patient can lift the straight leg, the quadriceps

mechanism is still intact. If this manoeuvre is

too painful, active extension can be tested withthe patient lying on his side. If there is an

effusion, aspiration may reveal the presence of

blood and fat droplets


10/22

X-ray.

The x-ray may show one or more fine fracture

lines without displacement, multiple fracture

lines with irregular displacement or atransverse fracture with a gap between the

fragments (Fig. 30.14). Comparative x-rays of

the opposite knee may help to distinguish

normal from abnormal appearances in

undisplaced fractures


11/22

Patellar fractures are classified as

1. Transverse

2. Longitudinal

3. Polar or comminuted (stellate)

Any of these may be either undisplaced or

displaced. Separation of the fragments is

significant if it is sufficient to create a step onthe articular surface of the patella or, in the

case of a transverse fracture, if the gap is

more than 3 mm wide.


12/22

A fracture with little or no displacement can be

treated conservatively by a posterior slab of plaster

that is removed several times a day for gentle

active exercises.


13/22

With severe comminutions, patellectomy is

arguably the best treatment, although

some surgeons would consider preserving

as many useful fragments as possible


14/22

A fracture line running obliquely across the

superolateral corner of the patella should not

be confused with the smooth, regular line of a

(normal) bipartite patella. Check the oppositeknee; bipartite patella is often bilateral


15/22

Undisplaced or minimally displaced fractures.

If there is a haemarthrosis it should be

aspirated. The extensor mechanism is intact

and treatment is mainly protective. A plastercylinder holding the knee straight should be

worn for 34 weeks, and during this time

quadriceps exercises are to be practised every

day.


16/22

Comminuted (stellate) fracture

The extensor expansions are intact and the

patient may be able to lift the leg However, the

undersurface of the patella is irregular andthere is a serious risk of damage to the

patellofemoral joint. For this reason some

people advocate patellectomy, whatever the

degree of displacement.


17/22

To others it seems reasonable to preserve the

patella if the fragments are not severely

displaced (or to remove only those fragments

that obviously distort the articular surface); ahinged brace is used in extension but

unlocked several times daily for exercises to

mould the fragments into position and to

maintain mobility.


18/22

Fractured patella

transverse Theseparated

fragments (a) are transfixed by K-wires;

(b) malleable wire

is then looped around the protruding ends

of the K-wires and tightened over the front

of the patella


19/22

Displaced transverse fracture

The lateral expansions are torn and the entire

extensor mechanism is disrupted. Operation is

essential.


20/22

Through a longitudinal incision the fracture is

exposed and the patella repaired by the

tension-band principle. The fragments are

reduced and transfixed with two stiff K-wires;flexible wire is then looped tightly around the

protruding K-wires and over the front of the

patella


21/22

The tears in the extensor expansions are then

repaired. A plaster backslab or hinged brace is

worn until active extension of the knee is

regained; either may be removed every day topermit active knee-flexion exercises.


22/22

Fracture of Patella

Documents

Transcript of Fracture of Patella