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British Medical Books Health Issues Computerized Tomography

Dislocation of Hip

  • pure hip dislocations
  • dislocations with fracture of the femoral head or acetabulum
  • posterior, anterior, central
  • acute or chronic (rare)

Mechanism of injury

  • high energy - MVA, fall from height
  • complicated by injuries to other organ systems
  • may injure the sciatic, femoral, or obturator nerve

Orthopaedic emergencies

  • should be reduced as quickly as possible
  • closed manipulation
  • operative reduction

Radiology

AP view

  • demonstrate the iliac bone, sacrum, pubis, ischium, femoral heads & necks, greater & lesser trochanters
  • arcuate, iliopubic, ilioischial, and teardrop lines, sacral foramina, & SI joint
  • patient supine with feet slightly (15°) IR

Landmarks

  • iliopectineal line –> denotes Anterior Column
  • ilioischial line –> denotes limit of Posterior Column
  • anterior lip of the acetabulum
  • posterior lip of acetabulum
  • superior wt bearing surface of acetabulum, ending in medial teardrop

Judet Views

Internal (Obturator) Oblique View

  • shows iliopectineal line (ant column & posterior wall)
  • pt supine with involved side of pelvis rotated anteriorly 45°
  • should be done unreduced & reduced -> help classification - UCT

External (Iliac) Oblique View

  • shows ilioischial line (post. column & anterior wall)
  • pt supine with uninvolved side of pelvis rotated ant. 45°

Roof Arc Measurements (Matta)

  • helps determine the amount of intact acetabular dome
  • useful method for determining need for surgery
  • less predictive for two column injuries & posterior wall #

Measurement

  • made on AP, obturator & iliac oblique views
  • vertical line drawn to geometric center of acetabulum
  • another line drawn thru point where # line intersects acetabulum
  • angle represents medial, anterior, or posterior roof involvement

CT scan

  • always
  • shows anterior or posterior involvement, impaction or fragments in joint
  • helps pre-op. planning

3D CT reconstruction

  • excellent overall view of injury

Older classification systems

  • posterior
  • anterior
  • central
    • rare –> with significant metabolic bone disease
    • more commonly central fracture-dislocation

Posterior dislocation of the hip

Thompson & Epstein classified into five types:

  • Type I – with or without minor fracture
  • Type II – single fracture of posterior acetabular rim
  • Type III – comminution of posterior acetabular rim with or without major fragment
  • Type IV – fracture of the acetabular floor
  • Type V – of the femoral head
    • further classified by Pipkin I - IV
    • CT scan in planning treatment

UCT modified classification

  • associates floor #s with type II & III
    • Type I
      • pure dislocation
      • large single fragment
      • with associated floor #
      • comminuted #
      • with associated floor #
      • “Pipkin injury”

General guidelines

  1. long-term results related to severity of initial trauma
  2. reduction performed ASAP
  3. only one attempt at closed reduction

Type I dislocation

  • treated by closed reduction
  • followed by immobilisation in Buck’s traction for 2/52
  • if stable after reduction –> prolonged immobilization & NWB unnecessary
  • check for sciatic nerve injury

Open reduction

  • posterior or lateral approach
  • if closed reduction failed
  • non-concentric
    • loose body, labrum or soft tissue caught within the joint

Type II fracture dislocation

  • immediate closed reduction
  • stability determined –> flexion & extension of the hip through 30 to 70°
  • CT –> determining loose fragments
  • if stable & no loose bodies –> traction 6/52, then PWB on crutches 6/52
  • if loose bodies or unstable –> fixation later –> PWB for 12/52

Types III, IV, and V fracture-dislocations

  • almost always treated surgically
    • Kocher-Langenbeck post. approach
  • CT for planning
  • PWB 3 to 6 months after surgery

Sciatic nerve injury

  • if fail to improve in 4/52 after closed reduction –> explore
  • if open reduction –> nerve explored

Anterior dislocation of the hip

  • uncommon - 12%
  • femoral vessels & nerve may be injured
  • leg externally rotated, flexed and abducted
  • position assumed by the femoral head
    • pubic, obturator, or perineal
  • usually can be reduced closed
  • if not –> open reduction (anterior iliofemoral approach)
    • interposition of soft tissues(rectus femoris & iliopsoas, torn hip capsule)
  • CT scanning

Overall prognosis and complications

  • excellent function –> if neither AVN nor traumatic OA of the joint develops

Avascular necrosis (AVN)

  • early, gentle reduction preventing
  • < 12 hrs –> 15%
  • > 12 hrs –> 50%
    • worse if open reduction necessary
    • ? effect of trauma
  • prolonged protection from WB –> little effect
  • clinically apparent ~ 18 months
  • when any hip pain develops –> weight bearing avoided until it subsides

Rx

  • see AVN

Traumatic arthritis

  • related to the nature of the injury to the joint

incidence

  • 30% after closed methods
  • 20 - 70% after open techniques
  • may develop after 4 to 5 years after the injury

Ectopic ossification

  • especially after open reduction
  • incidence of 3%
  • usually not disabling
  • early active exercises –> little if any effect
  • muscle contusions & intramuscular hematoma formation causing factors

Chronic dislocation of the hip

  • rare
  • delay in reduction –> AVN, OA, ankylosis
  • closed reduction may be possible if < 4⁄52
    • ? pre-op. traction
  • open reduction often necessary
    • if acetabular # < 3⁄12 –> ORIF
    • if > 3/12 –> reconstruction (arthrodesis, THR)