Dr. Kevin Yip

Dr Kevin Yip
Orthopaedic Surgeon
MBBS(UK), FRCS(EDIN), FAM(SING), FHKCOS(ORTHO)

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Knee Supracondylar Fracture

Basics
Description
  • These fractures involve the supracondylar (metaphyseal) area of the distal femur.
  • Classification AO/ASIF:
    • Type A: Extra-articular:
      • A1: Simple fracture
      • A2: Metaphyseal wedge
      • A3: Comminuted metaphyseal fracture
    • Type B: Unicondylar:
      • B1: Lateral condyle
      • B2: Medial condyle
      • B3: Fracture in the frontal plane
    • Type C: No part of the joint is attached to the shaft.
      • C1: Simple articular fracture with simple metaphyseal fracture
      • C2: Simple articular fracture with comminuted metaphyseal fracture
      • C3: Fractures with articular comminution
  • Synonym: Distal femur fracture
Epidemiology
Incidence
  • Up to 30% of all femur fractures
  • Less common than femoral shaft fractures
  • Most pediatric supracondylar femur fractures occur in adolescents.
  • 2 peaks:
    • Young (<35 years old): High-energy fractures
    • Older (>50 years old): Low-energy fractures
  • In the young, high-energy group, males are affected more commonly than females.
  • In the older, low-energy group, females are affected more often than males.
  • Osteopenia is prevalent in the older, low-energy group.
Risk Factors
Risk factors in the older group are osteopenia and previous age-related fractures.
 
Etiology
  • Young group: High-energy trauma (e.g., motor vehicle collision, falls from heights)
  • Older group: Low-energy trauma (e.g., falls on flexed knee)
  • Rarely, a complication of total knee arthroplasty
  • In pediatric patients, injuries usually are traumatic, with the fracture exiting at the metaphysis on the compression side, resulting in a Salter-Harris type II fracture.
Associated Conditions
  • Acetabular fractures
  • Hip dislocations
  • Femoral neck and shaft fractures
  • Knee ligamentous injuries
  • Tibial plateau and shaft fractures
  • Femoral artery disruptions
Diagnosis
Signs and Symptoms
  • Pain
  • Tenderness to palpation
  • Edema
  • Deformity
  • Inability to walk
  • Ecchymosis
Physical Exam
  • Complete musculoskeletal and neurovascular examination is essential.
  • Full examination of the knee is difficult until after fracture fixation.
Pathological Findings
  • Muscle spasm often leads to shortening of the femur and limb.
  • The femoral shaft often overrides anteriorly as the gastrocnemius pulls the distal fragment posteriorly into an apex-anterior deformity.
  • The adductors often cause a varus deformity.
Tests
Imaging
  • Radiography:
    • Knee:
      • AP and lateral radiographs of the knee and supracondylar region
      • 45° oblique radiographs if intercondylar involvement is present
    • Pelvis:
      • AP radiograph (to rule out other fractures) in trauma settings
    • Hip and femur:
      • AP and lateral radiographs of the hip and the whole femur (to rule out other fractures) in trauma settings
  • Angiogram if distal vascular status is questionable
  • CT may be beneficial for operative planning for complex fractures.
  • Pediatric patients:
    • Standard trauma radiographs should be obtained.
    • Stress views may be taken when occult injury to the epiphysis is suspected.
    • The physeal line should be 3-5 mm thick until adolescence.
Differential Diagnosis
  • Bruise
  • Knee ligamentous injury
  • Fracture of the patella or proximal tibia
Treatment
General Measures
  • Anatomic articular alignment is paramount.
  • For nondisplaced and impacted fractures, a splint, cast, or fracture brace is used.
  • For extra-articular fractures and medically unstable patients, skeletal traction is an option.
  • For severe open fractures, external fixation is used.
    • May be applied across the knee to provide initial fracture stabilization
    • May be converted to internal fixation when soft-tissue injuries are controlled
  • Open reduction and internal fixation are used for most closed fractures.
  • In pediatric patients with epiphyseal injury, closed reduction with casting can be done if the fracture is stable.
Activity
  • Initial activity should be nonweightbearing on the affected extremity until fracture callus forms.
  • Then, weightbearing is advanced gradually.
Special Therapy
Physical Therapy
  • ROM and quadriceps and hamstring strengthening may begin early postoperatively.
  • The patient can advance to gait training as tolerated.
    • Some advocate toe-touch weightbearing.
  • Progressive weightbearing and resistance exercises when clinical and radiographic evidence of healing occurs (usually 2-3 months)
  • Complete union usually takes 4-6 months.
Medication
  • Analgesics such as narcotics or acetaminophen are given.
  • NSAIDs are avoided because they may inhibit bone healing.
Surgery
  • Goals are anatomic alignment and stable fixation of the fracture to allow early motion of the limb.
  • Indications include:
    • Open or displaced fractures
    • Fractures with vascular compromise
    • Irreducible fractures
    • Fractures in the patient with multiple injuries or ipsilateral lower-extremity fractures
  • Relative contraindications to surgery include:
    • Infection of the fracture area
    • A medically unstable patient
    • Very osteopenic bone
  • Surgical implant options include:
    • Metal plates angled blade plate
    • Condylar buttress plates
    • Locked plates
    • External fixation
    • Intramedullary nails
    • Total knee replacement
  • Metal plates:
    • Come in a variety of shapes
    • Can be used with simple and comminuted fractures
    • Can be applied through small incisions and placed on the bone submuscularly
  • External fixation most frequently is used to temporize fractures with extensive soft-tissue damage or in the unstable, polytrauma patient.
  • Intramedullary nails work well to stabilize comminuted fractures and can be placed antegrade or retrograde.
  • Total knee replacement with distal femoral replacement can be used in patients with severe osteopenia or pre-existing arthrosis.
  • When fractures occur near a knee prosthesis:
    • Fixation can be achieved through a retrograde intramedullary nail, fixed-angle device, or revision arthroplasty.
    • In general, the best treatment choices are (8):
      • Intramedullary nails for proximal fractures
      • Fixed-angle devices for fractures at the level of the implant
      • Revision arthroplasty for distal fractures or those with implant loosening
Pediatric Considerations
  • Closed reduction with percutaneous pinning has been shown to give satisfactory results for displaced pediatric fractures.
  • If the fracture is unstable, open reduction with internal fixation can be performed.
  • Postoperatively, the knee is immobilized in 10° of flexion until radiographic evidence of healing is present (~4 weeks).
Follow-up
Disposition
Patients should be monitored closely after initial trauma to rule out the development of compartment syndrome of the thigh.
 
Prognosis
  • The prognosis depends on the type and severity of the fracture; more complex fractures generally have poorer prognoses.
  • In general, patients have a good to excellent result with appropriate treatment.
  • Midterm results of treatment of periprosthetic fractures with intramedullary nails are excellent.
Complications
  • Knee stiffness
  • Infection
  • Nonunion
  • Malunion
  • Loss of fixation
  • Traumatic arthritis
  • Compartment syndrome
  • Physeal injury can result in an angular deformity or leg-length inequality.
    • Discrepancies >2.5 cm can be managed by contralateral epiphysiodesis, femoral shortening, or ipsilateral femoral lengthening.
Patient Monitoring
  • Patients are seen initially a few weeks after definitive fixation and then approximately monthly until the fracture heals and ROM is acceptable.
  • Clinical (pain to palpation) and radiographic (callus) monitoring is done until the fracture is healed.
  • Limited weightbearing may be started when good callus is evident and the patient is not tender to palpation around the fracture.
Miscellaneous
Codes
ICD9-CM
821.23 Femur supracondylar fracture
 
FAQ
Q: How should a distal femur fracture be treated?
A: Most fractures are treated with surgery using an intramedullary retrograde nail or a percutaneous locking plate. Rigid fixation allows for early motion of the knee to prevent knee stiffness.

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