Patellar sleeve fractures

DEFINITION

• Patellar sleeve fractures are rare injuries occurring in the skeletally immature population( 8 – 12 years) .
• Characterized by the separation of the cartilage “sleeve” from the ossified patella.
• Displaced bone-forming tissue will continue to grow and ossify, enlarging, and possibly duplicating the patella.

Epidemiology

• 1% of all fractures in pediatric population
• Accounts for approximately 50% of all patellar fractures
• The peak incidence of patellar sleeve fractures occurs around 12.7 years of age, with cases typically observed within a range spanning from 8 to 16 years.
• higher prevalence in boys
• male-to-female ratio ranging from 3:1 to 5:1 .
• Intense participation in sporting activities during this developmental period, coupled with rapid skeletal growth, may contribute to an increased risk.
• In children, sleeve fractures of the patella predominantly occur in the inferior pole
• Extremely rare condition in adults due to the biomechanical properties of the fully ossified patella.

Etiopathogenesis

• Patellar sleeve fractures typically result from distal or proximal avulsions
• These avulsions occur due to a sudden contraction of the quadriceps muscle during knee flexion.
• This forceful contraction of the quadriceps results in the separation of the inferior pole of the immature patella from the rest of the patella.
• The fragile nature of the immature patella, with its developing ossification centers and cartilaginous structure, predisposes it to such injuries, especially during periods of rapid growth and increased physical activity.
• Patella fractures are common in individuals who participate in activities that require explosive acceleration such as basketball, soccer, and volleyball.
• The biomechanical forces generated during these activities could exceed the tensile strength of the patellar tendon, resulting in the separation of the inferior pole of the patella.

ANATOMY

Osteology

• patella is largest sesamoid bone in body
• ossification begins at 3-5 years old
• superior 3/4 of posterior surface covered by articular cartilage
• articular cartilage thickest in body (up to 1cm)
• posterior articular surface comprised of medial and lateral facets
• lateral facet is larger facets separated by vertical ridge.

Soft tissue attachments

• quadriceps tendon and fascia lata attach to anterosuperior margin
• quadriceps tendon comprised of 3 layers
• superficial layer formed from rectus femoris tendon
• middle layer formed by vastus medialis and vastus lateralis tendons
• deep layer formed by vastus intermedius tendon
• patellar tendon attaches to inferior margin

Blood Supply

• derived from anastomotic ring originating from geniculate arteries
• most important blood supply to the patella is located at the inferior pole

CLASSIFICATION

• Anatomic
• superior pole-least common
• inferior pole-most common

PRESENTATION

History

• indirect injury – not associated with a direct blow to the knee

Symptoms

• severe knee pain
• inability to bear weight

 

Physical exam

Inspection : soft tissue swelling , diffuse tenderness , hemarthrosis of the knee joint .
High-riding patella or palpable gap at the distal end of the patella
indicates disruption of the extensor mechanism
ROM: difficulty with active extension of the knee, especially against resistance

IMAGINGS

XRAY
Views -AP ,lateral ,tangential

• small flecks of bone adjacent to superior or inferior pole
• slight anterior tilt of superior pole seen with proximal fractures
• patella alta seen with distal fractures
• patella baja seen with proximal fractures

May be useful for identifying a sleeve fracture when the diagnosis is not clear from the clinical and radiographic findings

TREATMENT

Nonoperative

• cylinder cast for 6 weeks

Indications

• nondisplaced fractures with intact extensor mechanism
  rare (most require ORIF)

Operative

• open reduction and internal fixation

Indications

• > 2-3mm displacement
• > 2-3mm articular step-off
• disrupted extensor mechanism

Open reduction and internal fixation

• approach
• medial parapatellar approach to knee
• soft tissue – repair torn medial/lateral retinaculum and/or quadriceps/patellar tendon
• instrumentation : stabilize fracture using transosseous sutures, modified tension band wiring, intraosseous suture anchors, interfragmentary screws
• Post-operative care : cylinder cast in extension for 2-3 weeks

COMPLICATION

• Patella alta
• Extensor lag
• Quadriceps atrophy
• Malunion
• Nonunion
• Painful hardware

 

• The blood supply of the young patella is derived from the anterior surface of the distal pole, with minimal contribution from the medial margins.
• Injury to the anterior and distal poles can result in avascular necrosis of the proximal pole .

REHABILITATION

• Immobilization and prevention of knee flexion for a period of three to six weeks postoperatively .
• The goal of physical therapy is to maintain strength through a combination of isometric, isotonic, and isokinetic exercises.
• The rehabilitation program should restore full ROM and function and reduce pain.
• ROM exercises may include passive ROM, isometric contraction of the quadriceps, and heel side.
• Manual and active stretching of the lower leg muscles.

CONCLUSIONS

• Patellar sleeve fractures, although rare in children, pose significant challenges both in terms of treatment and return to sports activity .
• Several surgical options have been shown to reduce immobilization time and speed rehabilitation.
• Evidence suggests that minimizing immobilization may play a critical role in achieving early and complete recovery of range of motion.
• Future studies should focus on refining diagnostic algorithms, optimizing surgical interventions, and standardizing rehabilitation protocols to improve patient outcomes and facilitate a rapid return to pre-injury activity levels.