2. Definition
• Patellar fractures are classified as either nondisplaced or
displaced.
• Those that are less than 1 to 2 mm articular step-off or 3
mm of fragment separation displaced are considered
nondisplaced fractures.
• Patellar fractures may also be described as transverse,
longitudinal, or comminuted (Figures 26-1 and 26-2).
• Extraarticular patellar fractures involve the poles of the
patella and are usually secondary to avulsion injuries.
3. Mechanism of Injury
• A direct blow to the patella accounts for the
majority of patellar fractures.
• Indirect force from a violent contraction of the
quadriceps muscle can also result in a patellar
fracture.
4. Treatment Goals
• Orthopaedic Objectives
• Alignment
o Fracture displacement. Fractures displaced greater than 3 mm are
usually associated with retinacular tears and a disruption of the extensor
mechanism. If an extensor lag is present, open repair of the retinaculum
should be performed.
o Articular congruity. Any fracture with a step-off of greater than 2 mm on
the articular surface should be considered significant. In such a case,
open reduction should be performed to decrease the risk of future
posttraumatic degenerative changes.
• Stability
o Stability is best achieved by restoring bony congruity and using hardware
to rigidly fix the fracture.
5. • Rehabilitation Objectives
Range of Motion
1. Restore full range of motion of the knee in flexion and extension
to prevent extension lag.
2. Restore the rectus femoris (two-joint muscle) to its full length so
as to achieve full range of motion of the hip and knee.
3. Maintain ligamentous flexibility, which may be reduced
secondary to trauma and immobilization.
6. • Muscle Strength
1. Improve the strength of the quadriceps muscle, which is an
extensor of the knee, and the rectus femoris, also a flexor of the
hip, which crosses two joints. The quadriceps may have sustained
direct trauma from injury or sustained reflex inhibition.
The vastus medialis is the first muscle affected and the last muscle
to recover.
Its oblique head is the stabilizer of the patella and prevents
subluxation.
2. Improve the strength of the hamstring muscles, which are strong
knee flexors.
3. Improve the quadriceps-hamstring balance.
7.
8. • Functional Goals
Normalize the gait pattern, especially in the stance
phase.
Undertake proprioceptive and sport-specific
training.
9. • Expected Time of Bone Healing
Eight to 12 weeks.
• Expected Duration of Rehabilitation
Twelve to 15 weeks.
10.
11. Methods of Treatment
• Cast or Knee Immobilizer
• Biomechanics: Stress-sharing device.
• Mode of Bone Healing: Secondary.
12. • Indications:
• This is the treatment of choice for nondisplaced patella fractures,
including extraarticular fractures as long as the extensor mechanism
remains intact.
• A cylinder cast is most often used, which allows full range of motion
at the ankle.
• Examine the knee carefully for its ability to perform active extension.
• Loss of active extension signifies tearing of the retinacular
mechanism, which requires an open repair.
• The choice of the knee immobilizer versus casting is made based on
patient compliance; if the patient is noncompliant, a cast should be
used.
• (See Figure 8-1A.)
13. • Open Reduction and Internal Fixation
• Biomechanics: Stress-shielding and stress-sharing
depending on the device used.
• Mode of Bone Healing: Primary, unless a solid
fixation is not achieved, in which case secondary
healing also occurs.
14. • Indications:
• This is the method of choice for the treatment of
comminuted and displaced fractures.
• The main goal of open reduction is to align the
articular surface in the hope of decreasing
posttraumatic degenerative changes.
• Any retinacular destruction is openly repaired (Figures
26-3, 26-4, 26-5, 26-6, and 26-7).
15.
16.
17.
18. Partial/Total Patellectomy
• If there is significant comminution that cannot be adequately
repaired, partial patellectomy or total patellectomy is performed.
• However, the excision of the patella can lead to pain, loss of
extensor strength, an extensor lag, and decreased range of motion
of the knee.
• Following partial or total patellectomy, the extremity is immobilized
in full extension for approximately 4 weeks.
• This allows tendon-to-bone healing (in case of partial patellectomy)
or tendon-to-tendon healing (in case of total patellectomy).
• After 4 weeks, full active range of motion of the knee is begun with
a gradual increase in the degree of flexion permitted.
19. Special Considerations of the Fracture
• Bipartite Patella
• Care should be taken not to mistake a bipartite
patella for a patella fracture.
• The knee should be carefully examined for
tenderness, and a comparison radiograph of the
opposite extremity should also be obtained to assist
in diagnosis.
20. • Long-Term Sequelae
• From the outset, the patient should be
warned of the possibility of degenerative joint
disease, decreased knee range of motion,
permanent extensor lag, and prolonged
swelling secondary to the injury.
21. Associated Injury
• Retinacular Tear
• In any patella fracture, the knee should be evaluated for its ability
to perform active extension.
• Loss of this ability signifies a tear of the retinacular mechanism.
• Generally speaking, displaced fractures of the patella (greater than
3 mm of displacement) are associated with a tear of the extensor
mechanism.
• Open repair of the patellar retinaculum should be undertaken in
this circumstance.
• This may also help to prevent extensor lag.
22. • Weight Bearing
• Typically, the patient is allowed full weight
bearing in a cast or knee immobilizer following
the initial treatment, regardless of whether
that treatment is casting or open reduction
and internal fixation.
23. Gait Cycle
• Stance Phase
The stance phase constitutes 60% of the gait
cycle.
24. • Heel Strike
• The quadriceps maximally contracts concentrically to
control knee extension.
• Tension is placed across the fracture line, which may cause
pain.
• The patella rides in the patellar groove at the distal end of
the femur.
• The patient may experience pain if there is step-off at the
fracture site and surfaces are not smooth.
• If the quadriceps is weak, knee buckling occurs; the patient
compensates by hyperextending and locking the knee to
prevent falling (see Figure 6-1).
25. • Foot-Flat
– The quadriceps begins to contract in elongation to
allow the beginning of flexion at the knee.
– The patient may experience pain as a result of
quadriceps contraction (see Figure 6-2).
26. • Mid-Stance
• Mid-stance represents the single-leg support phase in which full
weight bearing occurs.
• The knee is further flexed, and the patella may grind in the
patellofemoral groove if the undersurface of the patella across
the fracture site is uneven.
• Knee buckling may occur with quadriceps weakness (see Figure 6-3).
• Push-Off
Push-off is usually not a problem, because the calf muscles
dominate until the swing phase (see Figures 6-4 and 6-5).
27. • Swing Phase
The swing phase constitutes 40% of the gait cycle.
• Acceleration
– The quadriceps contracts to bring the tibia forward
on the femur.
– There may be patellofemoral grinding as the patella is
pressed into the patellar groove.
– However, this is usually not as much of a problem as
in the stance phase (see Figure 6-6).
28. • Mid-Swing
This phase is usually not problematic because the
hamstrings are contracting to slow the swing of
the tibia (see Figure 6-7).
• Deceleration
This phase is usually not problematic because the
hamstrings are contracting to slow the swing of
the tibia for heel strike (see Figure 6-8).
37. LONG-TERM CONSIDERATIONS AND PROBLEMS
• At every stage of treatment, radiographs should be checked
for loss of correction, defined as persistence of greater than
1 to 2 mm of articular step-off or greater than 2 to 3 mm of
displacement.
• If this occurs early in treatment before any operative
procedure, casting can be performed again, but more likely
open reduction and internal fixation will be necessary.
• If the loss of correction occurs after open reduction and
internal fixation, possibly as a result of broken fixation
devices, a revision of the procedure can be performed.
38. • If this is not successful, a partial or total patellectomy can be
performed.
• On the other hand, the knee can simply be followed up for
any future degenerative changes, which may manifest as pain
with knee motion.
39. • Quadriceps shortening can reduce knee extension.
• Watch for knee flexion contractures, because the resting
position for a swollen knee is about 30 degrees and is not
uncommon for a contracture.
• If there is a 15-degree contracture, then knee extension in
terminal swing, initial contact, mid-stance, and terminal
stance is inadequate.
• If there is a decrease in extension (in terminal swing), step
length shortens.
• If the knee is not appropriately extended in the mid-stance
and terminal stance phases, then there is an increase in the
demand of quadriceps activity.
40. • Chondromalacia patella may be present because of direct
trauma to the cartilaginous undersurface of the patella.
• This may present long-term problems, especially in stair
climbing when the patella is forced against the femur.
41. • Reflex inhibition of the iliopsoas muscle is possible
after surgery on the knee.
• Rehabilitation of the iliopsoas is needed if it has not
recovered on the affected side.
