SUMMARY

• Acetabulum fractures are pelvis fractures that involve the articular surface of the hip joint and may involve one or two columns, one or two walls, or the roof within the pelvis.

• Diagnosis can be made radiographically with dedicated pelvis radiographs (including Judet views) but frequently require CT pelvis for surgical planning.

• Treatment can be nonoperative for non-displaced fractures but displaced injuries require anatomic open reduction and internal fixation to minimize development of post-traumatic osteoarthritis.

EPIDEMIOLOGY

• Incidence

  • ~ 4 per 100,000 per year

• Demographics

  • fractures occur in a bimodal distribution

    • high energy trauma in younger patients (e.g., motor vehicle accidents)

    • low energy trauma in elderly patients (e.g., fall from standing height)

ETIOLOGY

• Pathoanatomy 

  • fracture pattern predominately determined by

    • force vector

    • position of femoral head at time of injury

    • bone quality (e.g., age)

• Associated conditions

  • orthopaedic manifestations

    • lower extremity injury (36%)

    • nerve palsy (13%)

      • most commonly seen in transverse + posterior wall fracture patterns

      • most commonly affects the peroneal division of the sciatic nerve 

    • spine injury (4%)

  • systemic injuries

    • head injury (19%)

    • chest injury (18%)

    • abdominal injury (8%)

    • genitourinary injury (6%)

ANATOMY

• Osteology

  • acetabular inclination & anteversion

    • mean lateral inclination of 40 to 48 degrees

    • anteversion of 18 to 21 degrees

  • column theory

    • acetabulum is supported by two columns of bone 

    • form an "inverted Y" 

    • connected to sacrum through sciatic buttress

      • posterior column 

        • comprised of

          • quadrilateral surface

          • posterior wall and dome

          • ischial tuberosity

          • greater/lesser sciatic notches

      • anterior column 

        • comprised of

          • anterior ilium (gluteus medius tubercle)

          • anterior wall and dome

          • iliopectineal eminence

          • lateral superior pubic ramus

• Vascular

  • corona mortis 

    • anastomosis of external iliac (epigastric) and internal iliac (obturator) vessels

    • at risk with lateral dissection over superior pubic ramus

LETOURNEL CLASSIFICATION

• Judet and Letournel

  • most common referenced classification system

    • classifed as 5 elementary and 5 associated fracture patterns 

  • most common fracture patterns

    • younger

      • posterior wall

      • transverse fracture "family"

        • transverse

        • T-type

        • transverse + posterior wall

    • elderly

      • anterior column (e.g., quadrilateral plate fractures)

      • anterior column, posterior hemitransverse

      • assoicated both column fractures

  • Elementary patterns
    	Illustration	AP	Obturator ob.	Iliac ob.	CT	Comments
    Posterior wall						Most common "gull sign" on obturator oblique view Check for injury to superior gluteal NV bundle
    Posterior column						Check for injury to superior gluteal NV bundle
    Anterior wall						Very rare
    Anterior column						More common in elderly patient with fall from standing
    Transverse						Axial CT shows anterior to posterior fx line Only elementary fx to involve both columns

  • Associated patterns
    	Illustration	AP	Obturator ob.	Iliac ob.	CT	Comments
    Associated Both Column						Characterized by dissociation of the articular surface from the innominate bone    "spur sign" on obturator oblique
    Transverse + Post. Wall						Most common associated fx Associated with the highest incidence of nerve injury
    T-type						May need combined approach
    Anterior column or wall + Post. hemitransverse						Most common in elderly patients
    Post. column + Post. wall						Only associated fracture that does not involve both columns

IMAGING

• Radiographs

  • recommended views

    • AP

    • judet 

       

      • obturator oblique 

        • shows profile of obturator foramen 

        • shows anterior column and posterior wall 

      • iliac oblique 

        • shows profile of involved iliac wing

        • shows posterior column and anterior wall 

  • optional views

    • inlet/outlet if concerned for pelvic ring involvement

    • examination under anesthesia (EUA) 

       

      • used to best assess posterior wall stability 

      • hip positioned in flexion, adduction and axial load

      • obtain obturator oblique view

      • opening of the medial clear space suggests instability of the posterior wall fracture 

  • findings

    • radiographic landmarks of the acetabulum 

      • iliopectineal line (anterior column)

      • ilioischial line (posterior column)

      • anterior wall

      • posterior wall

      • teardrop

      • weight bearing roof

        • superior acetabular rim may show os acetabuli marginalis superior which can be confused for fracture in adolescents 

           

      • Shenton's line

    • roof arc angle 

      • angle between vertical line through femoral head and line through fracture

      • helps to define fracture pattern stability

      • considered stable if the fracture line exits outside the weight bearing dome of the acetabulum

      • defined as < 45° on AP, obturator and iliac oblique views

      • not applicable for associated both column or posterior wall pattern because no intact portion of the acetabulum to measure

    • gull sign 

      • represents impaction of superomedial roof

      • seen on iliac oblique view

      • pathognomic for posterior wall fractures

    • spur sign 

      • represents most caudal part of intact ilium due to medialization of articular components

      • seen on obturator oblique view

      • pathognomic for ABC fractures

• CT scan 

  • indications

    • now considered a gold standard in management

  • findings 

    • fracture pattern orientation

    • define fragment size and orientation 

    • identify marginal impaction 

       

    • identify loose bodies (e.g., post-reduction) 

    • look for articular gap or step-off

  • roof-arc measurements

    • view

      • 2 mm fine cuts on axial view

    • findings

      • assess stability of the weight bearing dome based on the exiting fracture line

      • defined as an intact subchonral ring in the superior 10 mm of the acetabulum

      • > 2 mm incongruity in the articular segment is considered unstable

• Duplex doppler ultrasound

  • indications

    • delayed presentation to treating hospital

    • rule out DVT

TREATMENT

• Nonoperative

  • protected weight bearing for 6-8 weeks

    • indications

      • patient factors

        • high operative risk (e.g., elderly patients, presence of DVT)

        • morbid obesity

        • open contaminated wound

        • late presenting > 3 weeks

      • fracture characteristics

        • minimally displaced fracture (< 2 mm)

        • < 20% posterior wall fractures

          • treatment based on size of posterior wall is controversial

          • recommend an exam under anesthesia (EUA) using fluoroscopy best method to test stability 

             

        • femoral head congruency with weight bearing roof (out of traction)

          • both column fracture pattern with secondary congruence (out of traction)

        • displaced fracture with roof arcs > 45° in AP and Judet views or >10 mm on axial CT cuts

    • techniques

      • skeletal traction NOT required if stable fracture pattern, outside the weight-bearing dome

      • activity as tolerated with crutches/walker

      • weight-bearing

        • lowest joint reactive forces seen with toe-touch weight bearing and passive hip abduction 

           

          • greatest joint contact force seen when rising from a chair on the affected extremity 

             

      • DVT prophylaxis

      • close radiographic follow-up

• Operative

  • open reduction and internal fixation (ORIF) 

    • indications

      • patient factors

        • < 3 weeks from date of injury

        • physiologically stable

        • adequate soft-tissue envelope

        • no local infection

          • pregnancy is not contraindication to surgical fixation 

             

      • fracture factors

        • displacement of roof (> 2 mm)

        • unstable fracture pattern (e.g. posterior wall fracture involving > 40-50%)

        • marginal impaction

        • intra-articular loose bodies 

           

        • irreducible fracture-dislocation

    • outcomes

      • timing

        • associated hip dislocations should be reduced within 12 hours for improved outcomes 

           

          • incarcerated fragments upon reduction can be treated with urgent ORIF or placement of skeletal traction and delayed ORIF 

             

        • worse outcomes with fixation of fracture > 3 weeks from time of injury 

           

          • earlier operative treatment associated with increased chance of anatomic reduction 

      • peri-operative

        • clinical outcome correlates with quality of articular reduction 

           

          • postoperative CT scan is most accurate way to determine posterior wall accuracy of reduction which has greatest correlation with clinical outcome 

             

          • ideally articular reduction <2mm

      • post-operative

        • greatest stress on acetabular repair occurs when rising from a seated position using the affected leg, and occurs in the posterior superior portion of the acetabulum 

        • functional outcomes most strongly correlate with hip muscle strength and restoration of gait postoperatively 

           

  • total hip arthroplasty 

      

    • indications

      • usually elderly patients with

        • significant osteopenia and/or significant comminution

        • pre-existing arthritis

      • post-traumatic arthritis in all ages

    • timing

      • immediate vs. delayed THA

        • immediate THA (with, or without, fracture fixation)

          • wall fractures 

             

            • butress plate with multi-hole cup

          • column fracture 

             

            • cage and cup constructs

          • elderly patient with posterior wall acetabular fracture and associated posterior hip dislocation, marginal impaction, comminution, or femoral head damage.

            • superior functional outcomes with acute ORIF and immediate THA  

               

        • delayed THA

    • techniques

      • typically done with posterior approach when acetabular fracture

    • outcomes

      • patients older than 60 years have approx. a 30% late conversion rate to THA after acetabular fractures

      • 10-year implant survival noted to be around 75-80%

TECHNIQUES

• Closed reduction percutaneous screws (CRPP)

  • approach

    • anterograde (from iliac wing to ramus)

    • retrograde (from ramus to iliac wing)

    • posterior column screws

  • imaging 

    • obturator outlet best view to rule out joint penetration 

    • iliac inlet view best to determine anteroposterior position of screw within the pubic ramus 

       

    • obturator inlet view best to determine position of a supraacetabular screw within tables of the ilium 

        

• Open reduction internal fixation (ORIF)

  • approaches

    • approach depends on fracture pattern

    • two approaches can be combined

    • approaches include

      • anterior

        • ilioinguinal

        • iliofemoral

        • modified stoppa

      • posterior

        • Kocher-Langenbach

      • combined

        • extended iliofemoral

  • Approaches
    	Indications	Risks
    Anterior Approach (Ilioinguinal)	Anterior wall and anterior column  Both column fracture    Posterior hemitransverse	Femoral nerve injury    LFCN injury  Thrombosis of femoral vessels  Laceration of corona mortis in 10-15%.
    Posterior Approach (Kocher-Langenbach)	Posterior wall and posterior column fx  Most transverse and T-shaped  Combination of above	Increased HO risk compared with anterior approach    Sciatic nerve injury (2-10%)  Damage to blood supply of femoral head (medial femoral circumflex)
    Extensile Approach (extended iliofemoral)	Only single approach that allows direct visualization of both columns    Associated fracture pattern 21 days after injury  Some transverse fxs and T types  Some both column fxs (if posterior comminution is present)	Massive heterotopic ossification    posterior gluteal muscle necrosis
    Modified Stoppa Approach	Access to quadrilateral plate to buttress comminuted medial wall fractures	Corona mortis must be exposed and ligated in this approach

COMPLICATIONS

• Post-traumatic DJD 

   

  • most common complication

  • 80% survival noted at 20 years for patients s/p ORIF 

     

  • risk factors for DJD include 

     

    • age >40 

    • associated fracture patterns

    • concomitant femoral head injury

  • treat with hip fusion or THA

• Heterotopic ossification 

   

  • highest incidence with extensile approach

    • treat with

      • indomethacin x 1 weeks post-op

      • low dose external radiation

      • debridement of gluteus minimus intraoperatively 

  • lowest incidence with anterior ilioinguinal approach

• Osteonecrosis 

  • 6-7% of all acetabular fractures

  • 18% of posterior fracture patterns

• DVT and PE

• Infection

• Bleeding

• Neurovascular injury

  • risk factor

    • highest incidence with transverse + posterior wall fractures

• Intraarticular hardware placement

• Abductor muscle weakness

PROGNOSIS

• Poor outcomes are associated with:

  • multi-system trauma

  • increasing age

  • poor articular congruency

  • associated femoral head articular injury

  • post-traumatic arthritis