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British Medical Books Health Issues Computerized Tomography

Anatomy

  • lateral aspect of acetabulum forms an inverted Y
    • one limb forming the anterior & one the posterior column

Anterior Column

  • from iliac crest to symphysis pubis
  • includes anterior wall of acetabulum
  • follows iliopectineal line

Posterior Column

  • from superior gluteal notch thru acetabulum, obturator foramen & inferior pubic ramus
  • includes posterior wall & ischial tuberosity
  • follows ilioischial line on AP

Acetabular roof or dome

  • superior wt bearing area
  • including portion of anterior & posterior column
  • best seen on 3D CT

Mechanism of injury

  • pattern depends of position of femoral head in acetabulum
    • acts like a hammer - shattering acetabulum
  • usually high energy injuries – MVA
  • low energy in osteoporotic old patients – simple falls

Signs & Symptoms

  • suspect in any polytrauma patient
  • pain, deformity of hip
  • << ROM
  • local soft tissue injury
    • including local wounds, abrasions
    • Morel Lavale lesion - closed degloving injury over GT
    • risk for infection and/or poor healing

Associated injuries

  • pelvic fracture
  • dislocation of the hip
  • knee instability, patella
  • check sciatic nerve & pulses

Radiology of Acetabulum

AP view

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

Landmarks

  • iliopectineal line - denotes limit of 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 tear drop

Judet Views

Internal (Obturator) Oblique View

  • shows iliopectineal line (ant column & posterior wall)
  • pt supine with involved side of pelvis rotated anteriorly 45°

External (Iliac) Oblique View

  • shows ilioischial line (posterior 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 frx measurement
    • made on AP, obturator & iliac oblique views
    • vertical line drawn to the geometric center of the acetabulum
    • another line drawn thru point where line intersects acetabulum
    • angle represents medial, anterior, or posterior roof

CT scan

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

3D CT reconstruction

  • excellent overall view of injury

Judet-Letournel Classification

  • based on 3 x-ray views (AP, Obturator & Iliac view)
  • column theory
  • elementary – 20%
    • anterior wall
    • anterior column – iliopectineal line broken
    • posterior wall
    • posterior column - ilioischial line broken
    • transverse - involving both walls
  • associated – 80%
    • T-shaped
    • complex
    • combination of different elementary

AO comprehensive & classification

  • Type A – partial articular - one column ( mostly posterior )
  • Type B – transverse
  • Type C – complete articular, both column

Treatment

  • depending on fracture pattern & patient factors
    • displacement, comminution
    • age, bone quality

Non Operative Rx

  • if superior acetabular dome intact
    • based on the 3 standard roof arc measurements -> 45°
  • congruent joint with displacement < 2 mm
  • low transverse not involving wt bearing dome
  • in older, not fit patients
  • closed manipulation & skeletal traction
  • transcondylar - permitting active lower extremity exercise
  • trans GT
    • if needs lateral force
    • >> risk of infection
    • avoid in kids - growthplate injury
  • maintained 4-8 weeks to achieve bony union

Operative Rx

Indications

  • displacement > 2 mm
  • non-concentric reduction after dislocation of the hip
  • any intraarticular loose bodies associated with acetabular fracture

Contraindications

  • severe injuries to adjacent skin
  • bladder or bowel rupture
  • osteoporosis
  • “unfixable”

Pre Op Planning

  • timing - between 2 & 10 days after injury
    • decrease local intraop. bleeding
    • beyond 10 days fragments not as easily manipulated
    • associated injuries stabilised
    • pts must be afebrile & off AB for > 48 hrs prior to surgery
  • in skeletal traction preoperatively
  • reduction of femoral head confirmed on x-ray
  • X-ray work up – Judet views, CT scan, 3D CT

Surgical Approaches

  • Anterior
    • iliofemoral approach – anterior column
    • ilioinguinal approach – more extensive

Posterior - Kocher-Langenbach

  • for of posterior wall, posterior column, T shaped
  • sciatic nerve in danger – flex knee during surgery

Extensile

  • tri-radiate-transtrochanteric
  • extended iliofemoral
  • combined antero-posterior

Technique

  • leg free draped
  • specialized clamps
  • implants – 3,5 mm cortical screws, pelvic plates

Post Operative Management

  • mobilize in bed ASAP
  • crutch walking with PWB (15 kg) as soon as pain diminished
  • wt bearing increased progressively after 8 weeks

Complications

Intraoperative

Blood loss

  • expect intra-operative blood loss of 1000-1500 cc

Sciatic nerve palsy

  • flexion of the knee during surgery and intraop monitoring
  • early treatment consists of AFO
  • recovery may occur over a 3 year period
  • tendon transfers usually not performed until 3 year post op

Other nerves

  • femoral – anterior column injury or surgery
  • superior gluteal – posterior approach (greater sciatic notch)
    • paralysis of hip abductors
  • pudendal – traction table
  • lateral femoral cutaneous

Postoperative

Infection

  • acute, subacute or late
  • superficial or deep

Deep venous thrombosis

  • prophylaxis

Heterotopic ossification

  • rare with non operative treatment
  • with operative treatment & no prophylaxis - severe in 20-50%

Risk factors

  • iliofemoral approach > Koch Langenbeck > Ilioinguinal
  • multiple trauma, head injury, T-type fracture
  • young male

prophylaxis – indomethacin or single dose irradiation

AVN of femoral head

  • 5-20%
  • if delayed reduction

Chondrolysis

  • with or without surgery
  • early OA

Non-union

OA

  • incongruency
  • chondrolysis

Acetabulum in children

  • damage to tri-radiate cartilage in < 10 yrs old
  • growth disturbance
    • shallow acetabulum
    • hip subluxation