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Adult Acetabular Fractures

Definition

Incidence

  • M 2: F 1

Classification

  • There are five simple patterns & five associated fracture types

    Simple fracture types:

    1. Posterior wall
      1. Commonest type (25-33%). Very commonly associated with a hip dislocation (eg 86/100 in Moed’s study)
    2. Posterior column
    3. Anterior wall
    4. Anterior column
    5. Transverse fractures
      1. Transtectal – transverse fracture line crosses superior acetabular articular surface
      2. Juxtatectal – fracture line crosses at the junction of the superior acetabular articular surface & the superior cotyloid fossa
      3. Infratectal – fracture line crosses through the cotyloid fossa

    Associated fracture types:

    1. Associated posterior column & posterior wall
    2. Associated transverse & posterior wall
    3. T shaped
    4. Associated anterior column & posterior hemitransverse – subtle distinction from T shaped fractures. In the T shaped fracture the fracture line is horizontal with a stem; in the anterior column/posterior hemitransverse the anterior component is higher up & typically more displaced than the posterior component
    5. Both column fractures – the essential component of this fracture is that all elements of the articular cartilage are divided from the ilium. This sets this type of fracture apart from the transverse, T shaped, associated anterior column & posterior hemitransverse & associated transverse & posterior wall fractures

    In Matta’s series 21% were simple fracture types & 79% associated fracture types (this was a tertiary referral load).

    Commonest fracture type was both column fracture (35%)

Types of Acetabular Fractures

Aetiology

  • Young adults, car crashes
  • ~50% have another serious injury

Pathology

Bony anatomy

The acetabulum can be divided into two columns, anterior & posterior

    1. Anterior column
      • Anterior border of the iliac wing
      • Entire pelvic brim
      • Anterior wall of the acetabulum
      • Superior pubic ramus
    2. Posterior column
      • Greater sciatic notch
      • Lesser sciatic notch
      • Posterior wall of the acetabulum
      • Majority of the quadrilateral surface
      • Ischial tuberosity

    Judet & Letournel consider the acetabulum to be located in the cavity of an arch formed by two columns of bone, one anterior & the other posterior.

    The posterior column is also called the ilioischial column & the anterior column iliopubic

Biomechanics of normal hip

  • normal hip is not completely congruent
  • There is conflicting data on the patterns of loading in the normal hip.
    • ? weight in born on the periphery of the acetabulum (Charnley & Hammond)
    • ? loading occurs predominantly in the roof of the acetabulum

Pathoanatomy & classification

  • fracture pattern depends on the orientation of the femoral head at the moment of impact.
    • If it is internally rotated, a posterior wall fracture will be produced
    • If it is adducted, the dome of the acetabulum will be disrupted
  • Many surgeons use Letournel’s modification of Judet’s 1964 classification.
    • It is designed to guide the operative approach rather than provide a prognosis
    • There are five simple patterns & five associated fracture types

History

Examination

Investigations

Xrays

  • AP, obturator oblique, iliac oblique (Judet views)
  • AP
    • there are certain lines that if disrupted indicate a fracture of that region:
      • Iliopectineal line
        • a landmark of the anterior column
      • Ilioischial line
        • represents the posterior portion of the quadrilateral surface & therefore a radiographic landmark of the posterior column
      • teardrop
        • which consists of a lateral & medial limb
          • Lateral limb: inferior aspect of the anterior wall of the acetabulum
          • Medial limb: obturator canal & anteroinferior portion of the quadrilateral surface
        • teardrop & ilioischial line are always superimposed in a normal acetabulum.
      • Roof of the acetabulum
        • superior aspect of the acetabulum
  • Obturator oblique view
    • taken with the pelvis internally rotated 45° (by lying on a wedge shaped cushion)
    • This view throws the anterior column into prominence
    • best way of making out fractures of the posterior wall of the acetabulum
  • Iliac oblique view
    • taken with the pelvis externally rotated 45°
    • shows the iliac wing & posterior column, & the anterior rim of the acetabulum best

CT scan

  • provides additional information, e.g. on bony fragments within the joint space, cartilage fragments which can be inferred from joint space widening, & 3D reconstruction which can allow removal of the femoral head from the picture to simplify things

Treatment

Non-operative treatment

  • Indications
    • Nondisplaced fractures
    • Acceptable displacement
      • Large part of roof of acetabulum is intact & femoral head articulates with this surface
        • eg. low anterior column or transverse type fractures (infratectal)
        • assessed by looking at the CT films 10mm below the apex of the roof
          • if there are no displaced fracture lines (>2mm) here there will be an arc of at least 90° of normal roof
        • provided the hip is congruent nonoperative treatment can be considered
        • Roof arcs can also be measured on plain films
      • Secondary congruence after moderate displacement of both column fracture
        • often contingent on the presence of an intact acetabular labrum
        • treatment skeletal traction
          • prevents further shortening.
          • traction must not distract the femoral head from the acetabulum
          • traction cannot be used to reduce a displaced acetabular fracture
          • 20 to 30 pounds via a supracondylar pin in nonoperatively treated fractures
    • Surgical contraindications
      • eg infection or gross osteoporosis
  • Treatment
    • 45 days of bed rest
    • passive ROM & massage
    • then another 45 days of touch weightbearing.

Operative

  • Inidication
    • Displacement of more than 2mm through weight bearing dome
    • Special situations:
      • Posterior wall fragments
        • Loading is altered by as little as 33% loss of posterior wall
        • Hip instability occurs with loss of 20-65% of width of posterior wall
        • If in doubt about need to fix can assess with EUA & fluoroscopy
      • Osteochondral fragments
        • If the fragments are preventing a congruent reduction of the hip joint they should be removed
  • Timing of surgery
    • delayed for at least 2-3 days
      • to allow bleeding to settle
    • immediate
      • dislocation of the femoral head which mandates immediate reduction
    • If performed more than 10 days post
      • fracture callus makes the operation more difficult

Surgical approaches

  • No one surgical incision is ideal for all fractures of the acetabulum
  • All three of the main approaches provide some access to both the columns
Surgical approaches for Acetabular Fractures
Approach
Kocher-Langenbeck best access to the posterior column
ilio-inguinal approach anterior column & the inner aspect of the innominate bone.
extended iliofemoral approach best simultaneous approach to both columns but:
  • approach to the anterior column isn’t as good as the ilio-inguinal approach
  • It has the longest postoperative recovery
  • It has the highest incidence of ectopic bone formation
  • It has the highest blood loss
  • it is preferable to choose the Kocher-Langenbeck or ilio-inguinal approach if possible.
    • Surgery should be done through one approach if possible

Kocher-Langenbeck approach

  • Indications
    • posterior wall & column fractures
  • Position
    • prone
    • This has several advantages:
      • Femoral head lies in a reduced position
      • tendency for the femoral head to translate medially is eliminated
      • Controlled traction is available by means of a fracture table while allowing flexion of the knee to relax the sciatic nerve
  • Incision
    • starts lateral to the PSIS, proceeds to the greater trochanter & then continues along the axis of the femur to almost the midpoint of the thigh
  • Deep
    • Gluteal fascia is split in line with the fibres of gluteus maximus
    • Fascia lata is split in line with the axis of the femur
    • gluteus maximus is posteriorly reflected
    • sciatic nerve is identified on the posterior surface of quadratus femoris & followed proximally until it disappears under piriformis
    • tendons of piriformis & obturator internus are transected at their trochanteric insertion & retracted posteriorly which exposes the greater & lesser sciatic notch
    • Subperiosteal elevation exposes the inferior aspect of the iliac wing
    • capsule can be opened along its rim & the femoral head distracted to expose the interior of the joint
    • Virenque suggested a modification whereby the sciatic spine is cut at its base; this provides an excellent view of the quadrilateral plate

Ilioinguinal approach

  • Indications
    • anterior column fractures
  • Position
    • supine, with hip flexed 20 to 30° to relax the psoas tendon. Insert IDC
  • Incision
    • from 2 fingerbreadths above the symphysis pubis, to ASIS, then two thirds along the iliac crest
  • Deep
    • periosteum is incised along the line of the iliac crest
    • iliacus is reflected from the interior aspect of the iliac wing
    • aponeurosis of the external oblique (which forms the roof of the inguinal canal) is incised & the spermatic cord isolated & protected; beware of ilioinguinal & iliohypogastric nn
    • An incision is then made along the floor of the inguinal canal & then the inguinal ligament from the pubic tubercle to the ASIS
    • iliopectineal fascia, which covers the internal aspect of the iliacus & plasters down the femoral nerve is released
    • Access to the internal aspect of the innominate is obtained via three windows, medial to the femoral artery & vein, between the neurovascular structures & iliopsoas & lateral to psoas. The vertical structures are defined, isolated with vessel loops & moved from side to side to gain access to the bone
    • Note:
      • interior of the joint cannot be seen after the fracture has been reduced

Extended iliofemoral approach

  • Indications
    • both column fractures
    • Provides access to the entire acetabulum, external iliac wing & the entire posterior column
  • Position
    • lateral, with knee flexed to relax the sciatic nerve or
    • supine with a sandbag under the ipsilateral buttock
  • Incision
    • starts at the PSIS
    • follows the iliac crest to the ASIS
    • then turns laterally to parallel the femur on the anterolateral aspect of the thigh
  • Deep
    • periosteum is reflected from the iliac crest & the gluteal muscles released from the iliac wing
    • Beware of the superior gluteal vessels, which nourish the gluteal flap thus created
    • anastomotic supply to the abductors is the ascending branch of the lateral femoral circumflex artery, & this is necessarily divided
    • tendons of gluteus medius, gluteus minimus, piriformis & obturator internus are transected & reflected posteriorly to expose the ischial spine & sciatic notches
    • An incision along the acetabular rim through the joint capsule provides access to the interior of the joint if the femoral head is distracted
    • reflected tendon of rectus femoris is usually divided
    • Sartorius & rectus femoris can be released from the ASIS to provide access to the internal aspect of the iliac wing, & this also allows access to the upper portion of the anterior column

Triradiate transtrochanteric

  • Indication
    • both column fractures
  • Position
    • lateral, with knee flexed
  • Incision
    • From the PSIS to the GT, from the ASIS to the GT, & then from the GT down the femoral shaft
  • Continuation
    • Generous flaps are raised down to the fascia
    • gluteus maximus & tensor fascia lata is exposed & incised in a Y type incision
    • This exposes the gluteus medius which is elevated via a trochanteric osteotomy
    • entire side wall of the pelvis is thus exposed from the anterior to the posterior iliac spine

Summary Choice of Incision

Ilioinguinal approach

  1. Anterior wall
  2. Anterior column
  3. Anterior column-posterior hemitransverse

Kocher-Langenbeck

  1. Posterior wall
  2. Posterior column
  3. Posterior column-posterior wall

Situational

  1. Transverse fractures
    • Kocher-Langenbeck except if the fracture line crosses the acetabulum from proximal anterior to distal posterior & the displacement is greatest anteriorly choose the ilioinguinal approach
  2. Transverse-posterior wall fractures, T shaped fractures
    • Kocher-Langenbeck unless the fracture looks very difficult in which case the extended iliofemoral approach may be used
  3. Both column fractures
    • Ilio-inguinal unless the fracture looks very difficult in which case choose the extended iliofemoral approach

A couple of points on reduction techniques

  • Specific instruments are available to ease reduction & fixation.
    • A Schanz pin inserted into the femoral neck can ease distraction of the femoral head
    • A Schanz pin into the posterior column is useful in the many cases of posterior column fractures where there is a rotational deformity
    • Farabeuf clamps are used with small screws drilled into each segment & provide significant reducing power
  • Consider using intraoperative fluoroscopy to avoid intraarticular screw placement
  • Difficult transverse posterior wall fractures
    • if they include a transverse transtectal component
    • if there is an extended posterior wall fracture involving the posterior border of the bone
    • if they consist of T-shaped & posterior wall fractures
    • if they are associated with dislocation of the pubic symphysis or fracture of contralateral pubic ramus
  • Difficult T-shaped fracture
    • Tranverse transtectal component
    • those with wide separation of the vertical stem of the T
    • those associated with pubic symphysis disruption or contralateral pubic ramus fracture
  • Difficult both column fractures
    • complex fracture of posterior column
    • displaced fracture line crossing the sacroiliac joint
    • wide separation of the anterior & posterior columns at the rim of the acetabulum

Complications

    • Wound infection
      • Rates are higher if there is associated bowel or vaginal injury
      • Higher if there is significant degloving. Degloving over the greater trochanter is known as a Morel-Lavale lesion. These injuries are frequently infected (46% rate of positive cultures)
    • Nerve palsy
      • Higher rate in the Kocher-Langenbeck approach
      • Sciatic nerve affected, usually peroneal branch
      • Attempt to always keep the knee flexed 60°
      • Femoral nerve may rarely be affected by a spike of bone from an anterior column fracture
    • Heterotopic ossification
      • Highest rate is with extended iliofemoral approach (57%), then Kocher-Langenbeck approach (26%). Very uncommon after ilio-inguinal approach
      • Other factors associated with HO are male sex, associated head or chest trauma, high ISS, T-shaped fractures
      • Decrease rate with indomethacin 25mg TDS for six weeks postoperatively, or with 800 Gy of radiation within 72 hours postoperatively. A recent low powered RCT in the HTO
      • If HO is extensive it can be removed at 15-18 months post surgery, with an expectation of around 80% of normal motion at this time
      • HO sometimes spontaneously regresses
    • Thromboembolic disease
      • 33% in pelvic veins on one MRI study
      • 61% in patients receiving no prophylaxis
      • PE in 10%, fatal PE in 2%
      • If a DVT is diagnosed prior to OT a caval filter should be inserted
      • Mechanical pumps may be the answer to perceived problems about blood loss from anticoagulants. These maintain venous flow & stimulate endogenous fibrinolytic activity. Pulsatile mechanical compression may be superior to low pressure sequential mechanical compression devices
    • AVN
      • 3-4% overall
      • incidence is related to the time to reduction
    • Blood loss
      • Highest with extended iliofemoral (1.6L in Matta’s study)
      • Lowest with Kocher-Langenbeck (900mL)
    • Osteoarthritis
      • Occurs within 5 years in 15-45% of patients (OKU7)
  • Arthritis is delayed for 10 years or more with an excellent reduction

Prognosis

Possible sequelae of acetabular fractures

    1. Post traumatic osteoarthritis
    2. AVN
    3. Acetabular non-union
    4. Protrusio
    5. Leg length discrepancy
    6. Nerve palsy

Measurement of outcomes

  • Matta’s classification of reduction on postoperative radiographs is:
    • Anatomic 0 to 1mm of displacement
    • Imperfect 2 to 3mm of displacement
    • Poor Greater than 3mm displacement

Outcomes

  • Dependent on
    • Timing of Intervention
      • Fractures treated after 21 days are more difficult to reduce & have poorer outcomes.
        • Letournel’s large series of 569 fractures treated within 21 days demonstrated clearly that anatomical reduction is essential for long-term success
        • If anatomical reduction was achieved 90% of patients had a good result, but this ideal was achieved in only 74% of cases
        • At a 20-year followup 28 of 35 cases initially graded as excellent remained excellent
    • Type of Fracture
      • In Matta’s study the outcomes were related to the type of fracture
        • He was able to achieve an anatomical reduction in 96% of the simple fracture types but only 64% of the associated fracture types
        • There was no statistically significant relation to the degree of initial displacement, but there was a trend towards worse results with greater displacement
      • Posterior wall fractures
        • Posterior wall fractures can often be anatomically reduced but the results do not reflect this
        • eg 94% of Letournel’s posterior wall fractures were anatomically reduced but only 82% had a good or excellent result
        • Many posterior wall fractures are associated with posterior hip dislocations, & these have a high rate of AVN
    • Age of Patient
      • Older patients (>40) have a lesser chance of an anatomical reduction
    • Abductor strength
      • related to the approach;
        • ilioinguinal approaches (89% normal abductors) were better than Kocher-Langenbeck (85%) & extended iliofemoral (66%)