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Pediatric Knee

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Ovid: Handbook of Fractures

Authors: Koval, Kenneth J.; Zuckerman, Joseph D.
Title: Handbook of Fractures, 3rd Edition
> Table of Contents > V – Pediatric Fractures and Dislocations > 49 – Pediatric Knee

49
Pediatric Knee
Overview
  • The knee is a ginglymoid (hinge) joint consisting of three articulations: patellofemoral, tibiofemoral, and tibiofibular.
  • Under normal cyclic loading, the knee may experience up to five times body weight per step.
  • The normal range of motion is from 10
    degrees of extension to 140 degrees of flexion, with 8 to 12 degrees of
    rotation through the flexion/extension arc.
  • The dynamic and static stability of the
    knee is conferred mainly by soft tissues (ligaments, muscles, tendons,
    menisci) in addition to the bony articulations.
  • Because ligaments in the immature
    skeleton are more resistant to tensile stresses than are physeal
    plates, trauma leads to physeal separation and avulsions not seen in
    the skeletally mature patient.
  • There are three physeal plates with secondary ossification centers.
  • Appearance of ossification centers is as follows:
    • Distal femur: thirty-ninth fetal week
    • Proximal tibia: by 2 months
    • Tibial tubercle: 9 years
  • Physeal closure is as follows:
    • Distal femur: 16 to 19 years
    • Proximal tibia: 16 to 19 years
    • Tibial tubercle: 15 to 17 years
  • The patella is a sesamoid bone, with its own ossification center, which appears at age 3 to 5 years.
  • Tibial spine: This is the site of insertion of the anterior cruciate ligament (ACL).
  • Two-thirds of longitudinal growth of the
    lower extremity is provided by the distal femoral (9 mm/year) and
    proximal tibial (6 mm/year) physes.
DISTAL FEMORAL FRACTURES
Epidemiology
  • The most commonly injured physis around the knee.
  • These comprise 1% to 6% of all physeal injuries and less than 1% of all fractures in children.
  • Most (two-thirds) are Salter-Harris Type II fractures and occur in adolescents.
Anatomy
  • The distal femoral epiphysis is the largest and fastest growing physis in the body.
  • There is no inherent protection of the physis; ligamentous and tendinous structures insert on the epiphysis.
  • The sciatic nerve divides at the level of the distal femur.

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  • The popliteal artery gives off the superior geniculate branches to the knee just posterior to the femoral metaphysis.
Mechanism of Injury
  • Direct trauma to the distal femur:
    Uncommon, but it may occur from vehicular trauma, falling onto a flexed
    knee, or during athletic activity, such as a lateral blow to the knee
    with a planted, cleated foot in football. In infants, this injury must
    be suspected to be the result of child abuse.
  • Indirect injury: Varus/valgus or
    hyperextension/hyperflexion; it usually results in simultaneous
    compression to one aspect of the physis with distraction to the other,
    with the epiphysis separating from the metaphysis owing to tension.
    Most typically, the physeal separation begins on the tension side and
    exits the metaphysis on the compression side (Salter-Harris Type II).
  • Birth injury secondary to breech presentation or arthrogryposis may cause this injury.
  • Minimal trauma in conditions that cause
    generalized weakening of the growth plate (osteomyelitis, leukemia,
    myelodysplasia) may also be causative.
Clinical Evaluation
  • Patients are typically unable to bear
    weight on the injured lower extremity, although patients with a
    nondisplaced physeal injury from a low-energy mechanism (e.g., athletic
    injury) may ambulate with an antalgic gait.
  • Older children and adolescents may relate
    a history of hearing or feeling a “pop;” along with associated knee
    effusion and soft tissue swelling, this may be confused with a
    ligamentous injury.
  • The knee is typically in flexion owing to hamstring spasm.
  • Gross shortening or angular deformity is
    variable, with potential compromise of neurovascular status resulting
    from traction injury or laceration. A complete neurovascular assessment
    is thus critical.
  • Point tenderness may be elicited over the
    physis; this is usually performed by palpating the distal femur at the
    level of the superior pole of the patella and adductor tubercle.
  • Most commonly, epiphyseal displacement is in the coronal plane producing varus/valgus deformity.
Radiographic Evaluation (Table 49.1)
  • Anteroposterior (AP), lateral, and
    oblique views should be obtained. Radiographs of the contralateral
    lower extremity may be obtained for comparison.
  • Stress views may be obtained to diagnose
    nondisplaced separations in which the clinical examination is highly
    suggestive of physeal injury (knees with effusion and point tenderness
    over physis in setting of negative AP and lateral x-rays). Adequate
    analgesia is necessary to relax muscular spasm and to prevent both
    false-negative stress radiographs and physeal injury.
  • The physeal line should be 3 to 5 mm thick until adolescence.
  • Salter-Harris Type III injuries usually
    have vertically oriented epiphyseal fracture components that are best
    appreciated on an AP view.
  • Computed tomography may be useful to assess articular involvement or to aid in fracture definition.

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  • In infants, separation of the distal
    femoral physis may be difficult to assess unless there is gross
    displacement because only the center of the epiphysis is ossified at
    birth; this should be in line with the anatomic axis of the femur on
    both AP and lateral views. Magnetic resonance imaging, ultrasound, or
    arthrography may aid in the diagnosis of distal femoral injury in these
    patients.
  • Arteriography of the lower extremity should be pursued if vascular injury is suspected.
Table 49.1. Imaging studies in the evaluation of distal femoral physeal fractures
Study Indications Limitations
Plain films First study, often sufficient May miss nondisplaced Salter Type I or III fractures or underestimate fracture displacement
Computed tomography scan Best defines fracture pattern and amount of displacement; useful in deciding whether surgery is needed and for planning surgery Poor cartilage visualization; less useful than magnetic resonance imaging in evaluating for occult Salter Type I or III fracture
Magnetic resonance imaging Evaluation of occult Salter I or III fracture possible; infants with little epiphyseal ossification Availability, cost, insurance
company authorizations; identifies associated soft tissue injuries;
unclear that study changes initial treatment
Stress views Differentiate occult Salter fracture from ligament injury Painful, muscle spasm may not permit opening of fracture if patient awake; unclear that study changes initial treatment
Contralateral x-rays Infants, or to assess physeal width Usually not needed
Modified from Bucholz RW, Heckman JD, Court-Brown C, et al., eds. Rockwood and Green’s Fractures in Adults, 6th ed. Philadelphia: Lippincott Williams & Wilkins, 2006.
Classification
Salter-Harris (Fig. 49.1)

Type I: Seen in newborns and adolescents; diagnosis easily missed; physeal widening may be demonstrated on stress radiographs
Type II: Most common injury of the
distal femoral physis; displacement usually medial or lateral, with
metaphyseal fragment on compression side
Type III: Intraarticular fracture exiting the epiphysis (typically medial condyle from valgus stress
Type IV: Intraarticular fracture exiting the metaphysis; high incidence of growth inhibition with bar formation; rare injury
Type V: Physeal crush injury; difficult diagnosis, made retrospectively after growth arrest; narrowing of physis possible

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Displacement
Figure 49.1. The Salter-Harris classification of fractures involving the distal femoral physis.

(From Bucholz RW, Heckman JD, Court-Brown C, et al., eds. Rockwood and Green’s Fractures in Adults, 6th ed. Philadelphia: Lippincott Williams & Wilkins, 2006.)

Anterior: Results from hyperextension injury; high incidence of neurovascular injury from proximal metaphyseal spike driven posteriorly
Posterior: Rare injury caused by knee hyperflexion
Medial: Valgus force most common, usually Salter-Harris Type II
Lateral: Varus force
Treatment
Nonoperative
  • Indicated for nondisplaced fractures.
  • A tense effusion may be addressed with sterile aspiration for symptomatic relief.
  • Closed reduction using general anesthesia may be performed for displaced fractures in which a stable result can be obtained (Fig. 49.2).
    Figure
    49.2. Closed reduction and stabilization of a Salter-Harris Type I or
    II distal femur fracture. (A) With medial or lateral displacement,
    traction is applied longitudinally along the axis of the deformity to
    bring the fragments back to length. (B) For anterior displacement, the
    reduction can be done with the patient prone or supine. Length is
    gained first, then a flexion moment is added.

    (From Bucholz RW, Heckman JD, Court-Brown C, et al., eds. Rockwood and Green’s Fractures in Adults, 6th ed. Philadelphia: Lippincott Williams & Wilkins, 2006.)

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  • Sufficient traction should be applied
    during manipulation to minimize grinding of physeal cartilage (90%
    traction, 10% leverage). The position of immobilization varies with
    direction of displacement:
    • Medial/lateral: Immobilize in 15 to 20
      degrees of knee flexion. Cast in valgus mold for medial metaphyseal
      fragment and varus mold for lateral metaphyseal fragment to tension
      intact periosteum.
    • Anterior: Immobilize initially at 90 degrees of knee flexion, then decrease flexion with time.
    • Posterior: Immobilize in extension.
  • A residual varus/valgus deformity after reduction tends not to remodel.
  • Crutch ambulation with toe-touch weight bearing may be instituted at 3 to 6 weeks after injury.
  • The cast may be discontinued at 4 to 8
    weeks depending on the patient age and healing status. A removable
    posterior splint and active range-of-motion exercises are instituted at
    this time.
  • Athletic involvement should be restricted
    until knee range of motion has returned, symptoms have resolved, and
    sufficient quadriceps strength has been regained.
Operative
  • Indications for open reduction and internal fixation include:
    • Irreducible Salter-Harris Type II
      fracture with interposed soft tissue: Cannulated 4.0- or 6.5-mm screw
      fixation may be used to secure the metaphyseal spike (Fig. 49.3).
    • Unstable reduction.
    • Salter-Harris Type III, IV: Joint congruity must be restored.
  • To minimize residual deformity and growth disturbance, certain guidelines should be observed for internal fixation
    • Avoid crossing the physis if possible.
    • If the physis must be crossed, use smooth pins as perpendicular as possible to the physis.
    • Remove fixation that crosses the physis as soon as possible.
  • Postoperatively, the patient is
    maintained in a long leg cast in 10 degrees of knee flexion. The
    patient may be ambulatory with crutches in 1 to 2 days with non–weight
    bearing on the injured extremity. At 1 week, the patient may begin
    straight leg raises.
  • If at 4 weeks evidence of osseous healing
    is demonstrated radiographically, the cast may be discontinued with a
    posterior splint in place for protection. The patient may be advanced
    to partial weight bearing with active range-of-motion exercises.
  • The patient typically resumes a normal, active lifestyle at 4 to 6 months after injury.
Complications
Acute
  • Popliteal artery injury (<2%):
    Associated with hyperextension or anterior epiphyseal displacement
    injuries in which a traction injury may be sustained or by direct
    laceration from the sharp metaphyseal spike.

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    • A cool, pulseless foot that persists despite reduction should be worked up with angiography to rule out laceration.
      Figure
      49.3. Screw fixation following closed or open reduction of a
      Salter-Harris Type II fracture with a large metaphyseal fragment. (A)
      When using cannulated screws, place both guide wires before screw
      placement to avoid rotation of the fragment while drilling or inserting
      screw. Screw threads should be past the fracture site to enable
      compression. Washers help increase compression. Screws may be placed
      anterior and posterior to each other, which is particularly helpful
      when trying to fit multiple screws in a small metaphyseal fragment. (B)
      This form of fixation is locally “rigid,” but it must be protected with
      long leg immobilization or long lever arm.

      (From Bucholz RW, Heckman JD, Court-Brown C, et al., eds. Rockwood and Green’s Fractures in Adults, 6th ed. Philadelphia: Lippincott Williams & Wilkins, 2006.)
    • Vascular impingement that resolves
      following reduction should be observed for 48 to 72 hours to rule out
      an intimal tear and thrombosis.
  • Peroneal nerve palsy (3%): Caused by
    traction injury during fracture or reduction or secondary to initially
    anterior/medial displaced epiphysis. Persistent peroneal palsy over 3
    to 6 months should be evaluated by electromyography, with possible
    exploration as indicated.
  • Recurrent displacement: Fractures of
    questionable stability following closed reduction should receive
    operative fixation (either percutaneous pins or internal fixation) to
    prevent late or recurrent displacement. Anterior and posterior
    displacements are particularly unstable.
Late
  • Knee instability (up to 37% of patients): Knee instability may be present, indicating concomitant ligamentous compromise that

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    was not appreciated at the time of index presentation. The patient may
    be treated with rehabilitation for lower extremity strengthening or may
    require operative treatment. Collateral ligaments may be acutely
    repaired if instability exists after fixation.

  • Angular deformity (19%): Results from the
    initial physeal injury (Salter-Harris Types I, II), asymmetric physeal
    closure (bar formation, Salter-Harris Type III, IV), or unrecognized
    physeal injury (Salter-Harris Type V).
    • Observation, physeal bar excision
      (<30% of physis, >2 years of remaining growth),
      hemiepiphysiodesis, epiphyseolysis, or wedge osteotomy may be indicated.
  • Leg length discrepancy (24%): Usually
    clinically insignificant if <2 years of growth remain; otherwise,
    the discrepancy tends to progress at the rate of 1 cm per year.
    • Discrepancy <2.5 cm at skeletal maturity usually is of no functional or cosmetic significance.
    • Discrepancy of 2.5 to 5 cm may be treated with contralateral epiphysiodesis (femoral or tibial) or femoral shortening.
    • Discrepancy >5 cm may be an indication
      for femoral lengthening combined with epiphysiodesis of the
      contralateral distal femur or proximal tibia.
  • Knee stiffness (16%): Results from
    adhesions or capsular or muscular contracture. It is usually related to
    the duration of immobilization; therefore, early discontinuation of the
    cast with active range of motion is desirable.
PROXIMAL TIBIAL FRACTURES
Epidemiology
  • Comprise 0.6% to 0.8% of all physeal injuries.
  • Average age is 14 years.
  • Most occur in adolescent boys.
Anatomy
  • The popliteal artery traverses the
    posterior aspect of the knee and is tethered to the knee capsule by
    connective tissue septa posterior to the proximal tibia. The vascular
    supply is derived from the anastomosis of the inferior geniculate
    arteries.
  • The physis is well protected by osseous
    and soft tissue structures, which may account for the low incidence of
    injuries to this structure.
    • Lateral: fibula
    • Anterior: patellar tendon/ligament
    • Medial: medial collateral ligament (MCL; inserts into metaphysis)
    • Posteromedial: semimembranosus insertion
Mechanism of Injury
  • Direct: Trauma to the proximal tibia (motor vehicle bumper, lawnmower accident).
  • Indirect: More common and involves
    hyperextension, abduction, or hyperflexion from athletic injury, motor
    vehicle accident, fall, or landing from a jump with a concurrent MCL
    tear.

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  • Birth injury: Results from hyperextension during breech delivery or arthrogryposis.
  • Pathologic condition: Osteomyelitis of the proximal tibia and myelomeningocele are causes.
Clinical Evaluation
  • Patients typically present with an
    inability to bear weight on the injured extremity. The knee may be
    tense with hemarthrosis, and extension is limited by hamstring spasm.
  • Tenderness is present 1 to 1.5 cm distal to the joint line, and variable gross deformity may be present.
  • Neurovascular status should be carefully
    assessed for popliteal artery or peroneal nerve compromise. The
    anterior, lateral, superficial posterior, and deep posterior
    compartments should be palpated for pain or turgor. Patients suspected
    of having elevated compartment pressures should receive serial
    neurovascular examinations with measurement of compartment pressures as
    indicated.
  • Associated ligamentous injuries should be
    suspected, although it may be difficult to appreciate these injuries
    secondary to the dramatic presentation of the fracture.
Radiographic Evaluation
  • AP, lateral, and oblique views of the
    affected knee should be obtained. Radiographs of the contralateral knee
    may be obtained for comparison.
  • Stress radiographs in coronal and
    sagittal planes may be obtained, but hyperextension of the knee should
    be avoided because of potential injury to popliteal structures.
  • Most patients with proximal tibial
    physeal injuries are adolescents in whom the secondary ossicle of the
    tibial tubercle has appeared. A smooth, horizontal radiolucency at the
    base of the tibial tubercle should not be confused with an epiphyseal
    fracture.
  • Magnetic resonance imaging may aid in identification of soft tissue interposition when reduction is difficult or impossible.
  • Computed tomography may aid in fracture definition, especially with Salter-Harris Type III or IV fractures.
  • Arteriography may be indicated in patients in whom vascular compromise (popliteal) is suspected.
Classification (Table 49.2)
Salter-Harris
Table 49.2. Classifications and implications of proximal tibial physeal fractures
Classification Implications
Mechanism of injury  
   I. Hyperextension Risk of vascular disturbance
   II. Varus/valgus Usually results from jumping; very near maturity
   III. Flexion See tibial tubercle fractures, type IV, in the next section
Salter-Harris pattern  
   I 50% nondisplaced
   II 30% nondisplaced
   III Associated collateral ligament injury possible
   IV Rare
   V Has been reported; diagnosis usually late
Modified from Bucholz RW, Heckman JD, Court-Brown C, et al., eds. Rockwood and Green’s Fractures in Adults, 6th ed. Philadelphia: Lippincott Williams & Wilkins, 2006.

Type I: Transphyseal injury; diagnosis often missed; may require stress or comparison views; 50% initially nondisplaced.
Type II: Most common; transphyseal
injury exiting the metaphysis; one-third nondisplaced; those that
displace usually do so medially into valgus
Type III: Intraarticular fracture of the lateral plateau; MCL often torn
Type IV: Intraarticular fracture of the medial or lateral plateau; fracture line exiting the metaphysis
Type V: Crush injury; retrospective diagnosis common after growth arrest

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Treatment
Nonoperative
  • Nondisplaced fractures may be treated
    with a long leg cast with the knee flexed to 30 degrees. The patient
    should be followed closely with serial radiographs to detect
    displacement.
  • Displaced fractures may be addressed with
    gentle closed reduction, with limited varus and hyperextension stress
    to minimize traction to the peroneal nerve and popliteal vasculature,
    respectively. The patient is placed in a long leg cast in flexion
    (typically 30 to 60 degrees, depending on the position of stability).
  • The cast may be discontinued at 4 to 6
    weeks after injury. If the patient is symptomatically improved and
    radiographic evidence of healing is documented, active range-of-motion
    and quadriceps strengthening exercises are initiated.
Operative
  • Commonly, displaced Salter Type I or II
    fractures in which stable reduction cannot be maintained may be treated
    with percutaneous smooth pins across the physis (Type I) or parallel to
    the physis (metaphysis) in Type II.
  • Open reduction and internal fixation are indicated for displaced Salter-Harris Types III and IV to restore articular congruity.

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    This may be achieved with pin or screw fixation parallel to the physis; articular congruity is the goal.

    Figure
    49.4. Posterior displacement of the epiphysis following
    fracture-separation at the time of injury can cause arterial injury. In
    addition, a posteriorly displaced fragment can cause persistent
    arterial occlusion by direct pressure.

    (From Bucholz RW, Heckman JD, Court-Brown C, et al., eds. Rockwood and Green’s Fractures in Adults, 6th ed. Philadelphia: Lippincott Williams & Wilkins, 2006.)
  • Postoperatively, the patient is
    immobilized in a long leg cast with the knee flexed to 30 degrees. This
    is continued for 6 to 8 weeks, at which time the cast may be removed
    with initiation of active range-of-motion exercises.
Complications
Acute
  • Recurrent displacement: This may occur if
    closed reduction and casting without operative fixation are performed
    on an unstable injury. It is likely secondary to a lack of collateral
    ligamentous attachment to the epiphysis.
  • Popliteal artery injury (10%): This
    occurs especially in hyperextension injuries; it is related to
    tethering of the popliteal artery to the knee capsule posterior to the
    proximal tibia (Fig. 49.4). Arteriography may be indicated when distal pulses do not return following prompt reduction of the injury.
  • Peroneal nerve palsy: This traction
    injury results from displacement, either at the time of injury or
    during attempted closed reduction, especially with a varus moment
    applied to the injury site.

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Late
Figure 49.5. Development of the tibial tubercle. (A) In the cartilaginous stage, no ossification center is present in the cartilaginous anlage of the tibial tubercle. (B) In the apophyseal stage, the secondary ossification center forms in the cartilaginous anlage of the tibial tubercle. (C) In the epiphyseal stage, the primary and secondary ossification centers of the proximal tibial epiphysis have coalesced. (D) In the bony stage, the proximal tibial physis has closed.

(From Rockwood CA Jr, Wilkins KE, Beaty JH, eds. Rockwood and Green’s Fractures in Children, 4th ed, vol. 3. Philadelphia: Lippincott-Raven, 1996:1274.)
  • Angular deformity: Results from the
    initial physeal injury (Salter-Harris Types I, II), asymmetric physeal
    closure (bar formation, Salter-Harris Type III, IV), or unrecognized
    physeal injury (Salter-Harris Type V). However, Salter-Harris
    classification has shown to be not useful in predicting growth
    disturbance in proximal tibial fracture types.
    • Observation, physeal bar excision
      (<30% of physis, >2 years of remaining growth),
      hemiepiphysiodesis, epiphyseolysis, or wedge osteotomy may be indicated.
  • Leg length discrepancy: This is usually
    clinically insignificant if <2 years of growth remain; otherwise,
    discrepancy tends to progress at the rate of 1 cm per year. Treatment
    for leg length discrepancy remains similar to that for distal femur
    physeal injuries.
TIBIAL TUBERCLE FRACTURES
Epidemiology
  • Represent 0.4% to 2.7% of all physeal injuries.
  • They are seen most commonly in athletic boys 14 to 16 years old.
  • It is important to differentiate these fractures from Osgood-Schlatter disease.
Anatomy (Fig. 49.5)
  • The tibial tubercle physis, which is
    continuous with the tibial plateau, is most vulnerable between the ages
    of 13 and 16 years, when it closes from posterior to anterior.
  • The insertion of the medial retinaculum extends beyond the proximal tibial physis into the metaphysic; therefore, after

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    tibial tubercle fracture, limited active extension of the knee is still
    possible, although patella alta and extensor lag are present.

  • The tubercle is located one to two
    fingerbreadths below the joint line. It is in line with the medial
    patella in flexion and the lateral patella in extension.
Mechanism of Injury
  • The mechanism of injury is typically
    indirect, usually resulting from a sudden accelerating or decelerating
    force involving the quadriceps mechanism.
  • Predisposing factors include:
    • Patella baja.
    • Tight hamstrings (increase flexion torque).
    • Preexisting Osgood-Schlatter disease (uncertain whether mechanical vulnerability or overdevelopment of quadriceps mechanism).
    • Disorders with physeal anomalies.
Clinical Evaluation
  • Patients typically present with a limited
    ability to extend the knee as well as an extensor lag. The leg is held
    in 20 to 40 degrees of flexion by spastic hamstrings.
  • Swelling and tenderness over the tibial tubercle are typically present, often with a palpable defect.
  • Hemarthrosis is variable.
  • Patella alta may be observed if displacement is severe.
Radiographic Evaluation
  • AP and lateral views of the knee are
    sufficient for the diagnosis, although a slight internal rotation view
    best delineates the injury because the tibial tubercle lies just
    lateral to the tibial axis.
  • Patella alta may be noted.
Classification
Watson-Jones

Type I: Small fragment avulsed and displaced proximally; fracture through secondary ossification center
Type II: Secondary ossification center
already coalesced with proximal tibial epiphysis; fracture at level of
horizontal portion of tibial physis
Type III: Fracture line passing
proximally through tibial epiphysis and into joint; possibly confused
with Salter-Harris Type III tibial physeal injury
Ogden
This modification of the Watson-Jones classification
(see earlier) subdivides each type into A and B categories to account
for the degree of displacement and comminution (Fig. 49.6).
Treatment
Nonoperative
  • Indicated for Type IA fractures with intact extensor mechanism.

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  • It consists of manual reduction and immobilization in a long leg cast with the knee extended, with patellar molding.
    Figure 49.6. Ogden classification of tibial tuberosity fractures in children.

    (From Ogden JA. Skeletal Injury in the Child, 2nd ed. Philadelphia: WB Saunders, 1990:808.)
  • The cast is worn for 4 to 6 weeks, at
    which time the patient may be placed in a posterior splint for an
    additional 2 weeks. Gentle active range-of-motion exercises and
    quadriceps strengthening exercises are instituted and advanced as
    symptoms abate.
Operative
  • Indicated for Types IB, II, III fractures or irreducible Type IA fractures (periosteum may be interposed).
  • A vertical midline approach is used; the
    fracture can be stabilized using smooth pins (>3 years from skeletal
    maturity), screws, threaded Steinmann pins, or a tension band.
  • Postoperatively, the extremity is placed
    in a long leg cast in extension with patella molding for 4 to 6 weeks,
    at which time the patient may be placed in a posterior splint for an
    additional 2 weeks. Gentle active range-of-motion exercises and
    quadriceps strengthening exercises are instituted and advanced as
    symptoms abate.
Complications
  • Genu recurvatum: This occurs secondary to
    premature closure of anterior physis; it is rare because injury occurs
    typically in adolescent patients near skeletal maturity.

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  • Loss of knee motion: Loss of flexion may
    be related to scarring or postoperative immobilization. Loss of
    extension may be related to nonanatomic reduction and emphasizes the
    need for operative fixation of Type IB, II, and III fractures.
  • Patella alta: May occur if reduction is insufficient.
  • Osteonecrosis of fracture fragment: Rare because of soft tissue attachments.
  • Compartment syndrome: Rare, but it may
    occur with concomitant tearing of the anterior tibial recurrent vessels
    that retract to the anterior compartment when torn.
TIBIAL SPINE (INTERCONDYLAR EMINENCE) FRACTURES
Epidemiology
  • Relatively rare injury, occurring in 3 per 100,000 children per year.
  • Most commonly caused by a fall from a bicycle (50%).
Anatomy
  • There are two tibial spines: anterior and
    posterior. The ACL spans the medial aspect of the lateral femoral
    condyle to the anterior tibial spine.
  • In the immature skeleton, ligaments are
    more resistant to tensile stresses than are physeal cartilage or
    cancellous bone; therefore, forces that would lead to an ACL tear in an
    adult cause avulsion of the incompletely ossified tibial spine in a
    child.
Mechanism of Injury
  • Indirect trauma: The mechanism includes rotatory, hyperextension, and valgus forces.
  • Direct trauma: Extremely rare, secondary to multiple trauma with significant knee injury.
Clinical Evaluation
  • Patients are typically reluctant to bear weight on the affected extremity.
  • Hemarthrosis is usually present, with painful range of motion and a variable bony block to full extension.
  • The MCL and lateral collateral ligament (LCL) should be stressed with varus/valgus pressure to rule out associated injury.
Radiographic Evaluation
  • AP and lateral views should be obtained.
    The AP view should be scrutinized for osseous fragments within the
    tibiofemoral articulation; these may be difficult to appreciate because
    only a thin, ossified sleeve may be avulsed.
  • Obtaining an AP radiograph to account for
    the 5 degrees of posterior slope of the proximal tibia may aid in
    visualization of an avulsed fragment.
  • Stress views may be useful in identification of associated ligamentous or physeal disruptions.

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Classification
Figure
49.7. Classification of tibial spine fractures. (A) Type I, minimal
displacement. (B) Type II, hinged posteriorly. (C) Type III, complete
separation.

(From Bucholz RW, Heckman JD, Court-Brown C, et al., eds. Rockwood and Green’s Fractures in Adults, 6th ed. Philadelphia: Lippincott Williams & Wilkins, 2006.)
Meyers and McKeever (Fig. 49.7)

Type I: Minimal or no displacement of fragment
Type II: Angular elevation of anterior portion with intact posterior hinge
Type III: Complete displacement with or without rotation (15%)
Type IV: Comminuted (5%)
Types I and II account for 80% of tibial spine fractures.
Treatment
Nonoperative
  • Indicated for Type I and II fractures of the tibial spine.
  • The knee should be immobilized in extension; the fat pad may contact the spine in extension and thus help with reduction.
  • After 4 to 6 weeks, the

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    cast is removed with initiation of active range-of-motion and quadriceps and hamstrings strengthening.

Operative
  • Indicated for Type III and IV fractures of the tibial spine owing to uniformly poor results with nonoperative management.
  • Debridement of fracture site is recommended with fixation using sutures, pins, or screws.
  • The fracture may be repaired arthroscopically with an ACL guide.
  • Postoperatively, the patient is placed in
    a long leg cast with the knee in slight (10 to 20 degree) flexion. In 4
    to 6 weeks, the cast is removed with initiation of active
    range-of-motion and quadriceps and hamstrings strengthening.
Complications
  • Loss of extension: Present in up to 60%
    of cases. Extension loss is typically clinically insignificant and may
    represent a bony block to extension caused by malunion of a type III
    fracture.
  • Knee instability: May persist with Type
    III or IV fractures accompanied by collateral ligament injuries and/or
    physeal fractures.
PATELLA FRACTURES
Epidemiology
  • Very rare in children; only 1% of all patella fractures are seen in patients less than 16 years of age.
Anatomy
  • The patella is the largest sesamoid in the body.
  • The function of the patella is to
    increase the mechanical advantage and leverage of the quadriceps
    tendon, aid in nourishment of the femoral articular surface, and
    protect the femoral condyles from direct trauma.
  • Forces generated by the quadriceps in
    children are not as high as in adults owing to a smaller muscle mass
    and shorter moment arm.
  • The blood supply to the patella derives
    from the anastomotic ring from the superior and inferior geniculate
    arteries. An additional supply through the distal pole is from the fat
    pad.
  • The ossification center appears between 3
    and 5 years. Ossification then proceeds peripherally and is complete by
    10 to 13 years.
  • Patella fracture must be differentiated
    from a bipartite patella (present in up to 8% of patients), which is
    located superolaterally. One should obtain contralateral films because
    bilateral bipartite patella is present in up to 50% of cases.
Mechanism of Injury
  • Direct: Most common and involves trauma
    to the patella secondary to a fall or motor vehicle accident. Cartilage
    anlage acts as a cushion to a direct blow.
  • Indirect: A sudden accelerating or decelerating force on the quadriceps.
  • Marginal fracture: Usually medial owing to patellar subluxation or dislocation laterally.
  • Predisposing factors include:
    • Previous trauma to the knee extensor mechanism.
    • Spasticity or contracture of the extensor mechanism.
Clinical Evaluation
  • Patients typically present with refusal to bear weight on the affected extremity.
  • Swelling, tenderness, and hemarthrosis are usually present, often with limited or absent active extension of the knee.
  • Patella alta may be present with avulsion or sleeve fractures, and a palpable osseous defect may be appreciated.

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  • An apprehension test may be positive and
    may indicate the presence of a spontaneously reduced patellar
    dislocation that resulted in a marginal fracture.
    Figure 49.8. Patellar fractures in children.

    (From Ogden JA. Skeletal Injury in the Child, 2nd ed. Philadelphia: WB Saunders, 1990:761.)
Radiographic Evaluation
  • AP, lateral, and patellar (sunrise) views of the knee should be obtained.
  • Transverse fracture patterns are most
    often appreciated on lateral view of the knee. The extent of
    displacement may be better appreciated on a stress view with the knee
    flexed to 30 degrees (greater flexion may not be tolerated by the
    patient).
  • Longitudinally oriented and marginal
    fractures may be best appreciated on AP or sunrise views. It is
    important to distinguish this from osteochondral fracture, which may
    involve a large amount of articular surface.
  • Stellate fractures and bipartite patella
    are best appreciated on AP radiographs. Comparison views of the
    opposite patella may aid in delineating a bipartite patella.
Classification
Based on Pattern (Fig. 49.8)

Transverse: Complete versus incomplete
Marginal fractures: Generally resulting from
lateral subluxation or dislocation of the patella; may be either medial
(avulsion) or lateral (direct trauma from condyle)
Sleeve fracture: Unique to immature skeleton;
consisting of an extensive sleeve of cartilage pulled from the osseous
patella with or without an osseous fragment from the pole
Stellate: Generally from direct trauma in the older child
Longitudinal avulsion  
Treatment
Nonoperative
  • Indicated for nondisplaced fractures (<3 mm) with an intact extensor mechanism.

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  • Consists of a well-molded cylinder cast with the knee in extension.
  • Progressive weight bearing is permitted as tolerated. The cast is generally discontinued at 4 to 6 weeks.
Operative
  • Displaced fractures (>3 mm diastasis
    or >3 mm articular step-off): Stabilization involves use of cerclage
    wire, tension band technique, sutures, or screws; the retinaculum must
    also be repaired.
  • Sleeve fracture: Careful reduction of the
    involved pole and cartilaginous sleeve is performed with fixation and
    retinacular repair; if this is missed, the result is an elongated
    patella with extensor lag and quadriceps weakness.
  • Postoperatively, the leg is maintained in
    a well-molded cylinder cast for 4 to 6 weeks. Quadriceps strengthening
    and active range-of-motion exercises are instituted as soon as possible.
  • Partial patellectomy should be reserved for severe comminution.
Complications
  • Quadriceps weakness: Compromised
    quadriceps function occurs secondary to missed diagnosis or inadequate
    treatment with functional elongation of the extensor mechanism and loss
    of mechanical advantage.
  • Patella alta: Results from functional
    elongation of the extensor mechanism and is associated with quadriceps
    atrophy and weakness.
  • Posttraumatic osteoarthritis: Degenerative changes occur secondary to chondral damage at the time of injury.
OSTEOCHONDRAL FRACTURES
Epidemiology
  • Typically involve the medial or lateral femoral condyles or the patella.
  • Often occur in association with patellar dislocation.
Anatomy
  • As the knee flexes, the patella engages the condylar groove. At 90 to 135 degrees, the patella rides within the notch.
Mechanism of Injury
  • Exogenous: A direct blow or a shearing force (patellar dislocation). This is the most common pathologic process.
  • Endogenous: A flexion/rotation injury of
    the knee. Contact between the tibia and the femoral condyle results in
    osteochondral fracture of the condyle.
Clinical Evaluation
  • The patient presents with knee effusion and tenderness over the site of fracture.
  • The knee is held in a position of comfort, usually in 15 to 20 degrees of flexion.

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Radiographic Evaluation
  • Standard knee AP and lateral x-rays often establish the diagnosis.
  • Schuss and Tunnel views may be helpful to localize the fragment near the notch.
Treatment
  • Operative excision versus fixation of
    fragment depends on the size and location of the defect as well as on
    the timing of surgery.
  • Small fragments or injuries to non–weight-bearing regions may be excised either open or arthroscopically.
  • Large fragments may be fixed with subchondral or headless lag screws.
  • If surgery is delayed more than 10 days
    after the injury, the piece should be excised because the cartilage is
    not typically viable.
  • Postoperatively, in patients with
    internal fixation, a long leg cast with 30 degrees of flexion is
    applied. The patient is typically non–weight bearing for 6 weeks.
  • If excision is performed, the patient may bear weight as tolerated and range the knee after soft tissues heal.
PATELLA DISLOCATION
Epidemiology
  • Patella dislocation is more common in
    women, owing to physiologic laxity, as well as in patients with
    hypermobility and connective tissue disorders (e.g., Ehlers-Danlos or
    Marfan syndrome).
Anatomy
  • The “Q angle” is defined as the angle
    subtended by a line drawn from the anterior superior iliac spine
    through the center of the patella and a second line from the center of
    the patella to the tibial tubercle (Fig. 49.9).
    The Q angle ensures that the resultant vector of pull with quadriceps
    action is laterally directed; this lateral moment is normally
    counterbalanced by patellofemoral, patellotibial, and retinacular
    structures as well as patellar engagement within the trochlear groove.
    An increased Q angle predisposes to patella dislocation.
  • Dislocations are associated with patella
    alta, congenital abnormalities of the patella and trochlea, hypoplasia
    of the vastus medialis, and hypertrophic lateral retinaculum.
Mechanism of Injury
  • Lateral dislocation: The mechanism is
    forced internal rotation of the femur on an externally rotated and
    planted tibia with the knee in flexion. It is associated with a 5% risk
    of osteochondral fractures.
  • Medial instability is rare and usually
    iatrogenic, congenital, traumatic, or associated with atrophy of the
    quadriceps musculature.
  • Intraarticular dislocation: Uncommon, but
    it may occur following knee trauma in adolescent boys. The patella is
    avulsed from the quadriceps tendon and is rotated around the horizontal
    axis, with the proximal pole lodged in the intercondylar notch.

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Clinical Evaluation
Figure
49.9. The Q (quadriceps) angle is measured from the anterior superior
iliac spine through the patella and to the tibial tubercle.

(From Insall JN. Surgery of the Knee. New York: Churchill Livingstone, 1984.)
  • Patients with an unreduced patella
    dislocation will present with hemarthrosis, an inability to flex the
    knee, and a displaced patella on palpation.
  • Patients with a lateral dislocation may also present with medial retinacular pain.
  • Patients with reduced or chronic patella
    dislocation may demonstrate a positive “apprehension test,” in which a
    laterally directed force applied to the patella with the knee in
    extension reproduces the sensation of impending dislocation, causing
    pain and quadriceps contraction to limit patellar mobility.
Radiographic Evaluation
  • AP and lateral views of the knee should
    be obtained. In addition, an axial (sunrise) view of both patellae
    should be obtained. Various axial views have been described by several
    authors (Fig. 49.10)
    • Hughston 55 degrees of knee flexion: sulcus angle, patellar index
    • Merchant 45 degrees of knee flexion: sulcus angle, congruence angle
    • Laurin 20 degrees of knee flexion: patellofemoral index, lateral patellofemoral angle
  • Assessment of patella alta or baja is based on the lateral radiograph of the knee.
    • Blumensaat line: The lower pole of the
      patella should lie on a line projected anteriorly from the
      intercondylar notch on the lateral radiograph with the patient’s knee
      flexed to 30 degrees.

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    • Insall-Salvati ratio: The ratio of the
      length of the patellar ligament (LL; from the inferior pole of the
      patella to the tibial tubercle) to the patellar length (LP; the
      greatest diagonal length of the patella) should be 1.0. A ratio of 1.2
      indicates patella alta, whereas 0.8 indicates patella baja (Fig. 49.11).
Figure
49.10. Representation of the (A) Hughston (knee flexed to 55 degrees)
(B) merchant (knee flexed to 45 degrees) and (C) Laurin (knee flexed to
20 degrees) patellofemoral views.

(From Bucholz RW, Heckman JD, eds. Rockwood and Green’s Fractures in Adults, 5th ed. Baltimore: Lippincott Williams & Wilkins, 2002.)
Classification
  • Reduced versus unreduced
  • Congenital versus acquired
  • Acute (traumatic) versus chronic (recurrent)
  • Lateral, medial, intraarticular, superior
Treatment
Nonoperative
  • Reduction and casting or bracing in knee extension may be undertaken with or without arthrocentesis for comfort.
  • The patient may ambulate in locked extension for 3 weeks, at which time progressive flexion can be instituted with physical

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    therapy for quadriceps strengthening. After a total of 6 to 8 weeks, the patient may be weaned from the brace.

    Figure 49.11. Insall-Salvati technique for measuring patellar height.

    (From Insall NJ. Surgery. New York: Churchill Livingstone, 1984.)
  • Surgical intervention for acute dislocations is rarely indicated except for displaced intraarticular fractures.
  • Intraarticular dislocations may require reduction with patient under anesthesia.
  • Functional taping with moderate success has been described in the physical therapy literature.
Operative
  • Primarily used in cases of recurrent dislocations.
  • No single procedure corrects all patella
    malalignment problems—the patient’s age, diagnosis, level of activity,
    and condition of the patellofemoral articulation must be taken into
    consideration.
  • Patellofemoral instability should be addressed by correction of all malalignment factors.
  • Degenerative articular changes influence the selection of realignment procedure.
  • Surgical interventions include:
    • Lateral release: Indicated for
      patellofemoral pain with lateral tilt, lateral retinacular pain with
      lateral patellar position, and lateral patellar compression syndrome.
      It may be performed arthroscopically or as an open procedure.
    • Medial plication: May be performed at the time of lateral release to centralize the patella.
    • Proximal patellar realignment: Medialization of the proximal pull of the patella is indicated when a lateral release/medial

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      plication fails to centralize the patella. The release of tight
      proximal lateral structures and reinforcement of the pull of medial
      supporting structures, especially the vastus medialis obliquus, are
      performed in an effort to decrease lateral patellar tracking and
      improve congruence of the patellofemoral articulation. Indications
      include recurrent patella dislocations after failed nonoperative
      therapy and acute dislocations in young, athletic patients, especially
      with medial patella avulsion fractures or radiographic lateral
      subluxation/tilt after closed reduction.

    • Distal patella realignment: Reorientation
      of the patella ligament and the tibial tubercle is indicated when an
      adult patient experiences recurrent dislocations and patellofemoral
      pain with malalignment of the extensor mechanism. This is
      contraindicated in patients with open physes and normal Q angles. It is
      designed to advance and medialize tibial tubercle, thus correcting
      patella alta and normalizing the Q angle.
Complications
  • Redislocation: A younger age at initial
    dislocation increases the risk of recurrent dislocation. Recurrent
    dislocation is an indication for surgical intervention.
  • Loss of knee motion: May result from prolonged immobilization.
  • Patellofemoral pain: May result from retinacular disruption at the time of dislocation or from chondral injury.
KNEE DISLOCATION
Epidemiology
  • Infrequent in skeletally immature
    individuals, because physeal injuries to the distal femur or proximal
    tibia are more likely to result.
Anatomy
  • Typically occurs with major ligamentous
    disruptions (both cruciates or equivalent spine injuries with
    disruption of either MCL or/and LCL) about the knee.
  • Associated with major disruption of soft
    tissue and damage to neurovascular structures; vascular repair must
    take place within the first 6 to 8 hours to avoid permanent damage.
  • Associated with other knee injuries, including tibial spine fractures, osteochondral injuries, and meniscal tears.
Mechanism of Injury
  • Most dislocations occur as a result of multiple trauma from motor vehicle accidents or falls from a height.
Clinical Evaluation
  • Patients almost always present with gross
    knee distortion. Immediate reduction should be undertaken without
    waiting for radiographs in the displaced position. Of paramount
    importance is the arterial supply, with secondary consideration given
    to neurologic status.
  • The extent of ligamentous injury is related to the degree of displacement, with injury occurring with displacement greater

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    than 10% to 25% of the resting length of the ligament. Gross instability may be appreciated after reduction.

  • A careful neurovascular examination is
    critical both before and after reduction. The popliteal artery is at
    risk during traumatic dislocation of the knee owing to the bowstring
    effect across the popliteal fossa secondary to proximal and distal
    tethering. Peroneal nerve injuries are also common, mostly in the form
    of traction neurapraxias.
Radiographic Evaluation
  • Gross dislocation should be reduced first and not delayed for films.
  • AP and lateral views are sufficient to establish the diagnosis; the most common direction is anterior.
  • Radiographs should be scrutinized for
    associated injuries to the tibial spine, distal femoral physis, or
    proximal tibial physis. Stress views may be obtained to detect
    collateral ligament injury.
  • It remains controversial whether all
    patients should have an arteriogram. Some authors state that if pulses
    are present both before and after reduction, arteriography is not
    indicated. The patient must be monitored for 48 to 72 hours after
    reduction because late thrombus may develop as a result of intimal
    damage.
Classification
Descriptive
Based on displacement of the proximal tibia in relation
to the distal femur. It also should include open versus closed and
reducible versus irreducible. The injury may be classified as occult,
indicating a knee dislocation with spontaneous reduction.

Anterior: Forceful knee hyperextension
beyond 30 degrees; most common; associated with PCL with or without ACL
tear, with increasing incidence of popliteal artery disruption with
increasing degree of hyperextension
Posterior: Posteriorly directed force
against proximal tibia of flexed knee; “dashboard” injury; accompanied
by ACL/PCL disruption as well as popliteal artery compromise with
increasing proximal tibial displacement
Lateral: Valgus force; medial supporting structures disrupted, often with tears of both cruciate ligaments
Medial: Varus force; lateral and posterolateral structures disrupted
Rotational: Varus/valgus with rotatory component; usually result in buttonholing of femoral condyle through capsule
Treatment
  • Treatment is based on prompt recognition
    and reduction of the knee dislocation, with recognition of vascular
    injury and operative intervention if necessary.

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  • No large series have been reported, but early ligamentous repair is indicated for young patients.
Complications
  • Vascular compromise: Unrecognized and
    untreated vascular compromise to the leg, usually in the form of an
    unrecognized intimal injury with late thrombosis and ischemia,
    represents the most serious and potentially devastating complication
    from a knee dislocation. Careful, serial evaluation of neurovascular
    status is essential, up to 48 to 72 hours after injury, with aggressive
    use of arteriography as indicated.
  • Peroneal nerve injury: Usually represents
    a traction neurapraxia that will resolve. Electromyography may be
    indicated if resolution does not occur within 3 to 6 months.

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