Hip Dislocation

IncidencePosterior Hip Dislocation

 

Young men

 

Posterior / Anterior 9:1

 

Aetiology

 

High velocity injury

- head direction at impact decides direction of dislocation

 

Anterior Dislocation 

 

Externally rotated & abducted leg

- flexion = inferior dislocation

- extension = pubic dislocation

 

Posterior Dislocation

 

Axial compression of adducted leg

- more flexion causes pure dislocation without fracture

 

Anatomy

 

Inherently stable joint

- large head on smaller neck

- allows deep seating of femoral head

- acetabulum deepened by labrum

- capsule reinforced by ilio/pubo/ischio femoral ligaments

 

40% femoral head in contact with articular cartilage

10% in contact with labrum

 

Blood supply

 

Majority by deep branch of Medial Circumflex Femoral Artery

- minimal by medial epiphyseal artery via ligamentum teres

- little to non via LCFA

 

MCFA

- arises medial aspect of profunda

- along posterior intertrochanteric crest extracapsular / back of femoral neck

- passes between iliopsoas and pectineus medially

- runs along inferior border of obturator externus, above adductor brevis

- deep to quadratus femoris

- emerges between quadratus and inferior gemellus

- runs over conjoint tendon (2 gemelli and obturator internus)

- then penetrates capsule between conjoint and piriformis

- runs along superior aspect of neck to femoral head

 

Transverse branch (to ischium) and ascending branch (to trochanteric fossa0

- arise anterior to quadratus

 

Must protect this deep branch MCFA in a posterior approach

 

With dislocation and capsular tears

- some ascending cervical branches stretched/kinked

- emergent reduction can improve blood flow to femoral head

 

Associated Injuries

 

50-95% have other injury

 

Acetabular fracture

 

Femoral head fracture / Pipkin fracture

 

Sciatic nerve 10% / posterior dislocation

 

Patella fracture

 

PCL

 

Femoral artery injury - anterior dislocation

 

Femoral shaft fracture

- reduce head via steinman pin in proximal fragment

- then IMN femur

 

Classification

 

Direction

 

1. Medial / Central

- really medial displacement with acetabular fracture

 

2. Anterior 

- pubic / obturator / perineal

 

3. Posterior

 

Posterior Hip Dislocation Lateral

 

Pathoanatomy

 

Capsule & Ligamentum teres torn

 

Labral tears & muscular injuries also occur

 

Y / iliofemoral ligament often intact with posterior dislocation

- blocks reduction

- bony fragments also block reduction

 

Clinical Features / Xray

 

Posterior dislocation

- leg shortened, flexed, adducted & internally rotated 

- head small on xray

 

Posterior Hip Dislocation

 

Anterior dislocation 

- leg short and externally rotated

- head larger on xray

 

Check NV status / sciatic nerve

 

Management

 

Immediate

 

Assess & manage life threatening injuries

- EMST / ATLS principles

 

Principles

 

1. Emergent reduction

- closed +/- open

- reduce risk AVN 

 

AVN

- < 6 hours 10%

- 20% - 50% if >24 hours

 

2.  Assess stability

 

Posterior wall fracture > 40%

- need ORIF for stability

 

Hip Dislocation Posterior Wall FractureHip Dislocation Posterior Wall Fracture

 

Posterior wall fracture < 40%

- can be unstable

- EUA after reduction to assess stability

- should be able to flex to 90o and some IR without instability

 

3. Screen for retained fragments

 

Compulsory CT

- xray will not detect fragments < 2mm

 

Hip Dislocation Loose Body

 

Remove / ORIF depending on size of fragment and location / Pipkin type

 

4. Reconstruct acetabulum if unstable or incongruent

 

Closed Reduction Posterior Dislocation

 

Technique

 

Full muscle paralysis on radiolucent table 

- supine

- assistant places downward pressure on ASIS

- operator up on bed grasping leg

- flex hip to 90o, flex knee to 90o

 

Technique

- ER head around acetabulum / axial traction or

- IR head around acetabulum / axial traction

 

Post reduction

- check concentric reduction on II

- check stability in flexion

 

Unstable reduction

- skeletal traction / femoral steinman pin

 

Post op

 

NV examination when patient awake

- ensure sciatic nerve working

- ensure hasn't become entrapped with reduction

 

CT

 

Closed Reduction Anterior Dislocation

 

Technique

- as above

- traction in line with femur flexed

- internal rotation maneuver

 

Irreducible Dislocations

 

Incidence

- 2-15%

 

Causes

 

1.  Capsule / Labrum / Ligamentum teres

2.  Muscle interposition

- anterior usually rectus / psoas

- posterior usually piriformis / G maximus

3. Bone fragment

4.  Muscle tone

- patient requires relaxant

 

Management

 

Open reduction

 

Non-concentric Reduction

 

Esssential to obtain X-ray and CT after reduction

 

X-ray

- head - teardrop distance must equal contralateral side

 

CT

- only with CT can < 2mm fragments be seen

 

Pipkin Infrafoveal CT

 

MRI

- may be needed to see labral tears blocking reduction

 

Open reduction

 

Indications

 

1.  Irreducible dislocation

 

2.  Non-concentric reduction

- loose bodies / interposed tissue

 

3.  Post operative sciatic nerve palsy

 

4.  Unstable posterior acetabular fracture

 

5.  Associated NOF fracture

 

6.  ORIF Pipkin fracture

 

Approach 

 

Usually from direction of dislocation

- preserve intact capsule

- preserve remaining blood supply

- i.e. with posterior dislocation the posterior capsule will be torn

- provides entry into joint

 

Posterior Approach

 

Aim to preserve intact anterior capsule and blood supply

- beware sciatic nerve

- divide piriformis and conjoint tendon away from insertion to preserve deep branch MCFA

- may need to extend posterior capsular rent

- allows direct visualisation of blocks to reduction

- blocks include G. max, piriformis, capsule, bony fragments

- may need to excise ligamentum teres

- explore acetabulum for loose bodies

- close capsule afterwards

- may need to excise L Teres

 

Other issues

 

Posterior acetabular fracture

- ORIF if > 40% or unstable

 

Pipkin fracture

- manage as per Femoral Head Fractures

 

Subcapital fracture

- Watson Jones / Smith Peterson approach

- supplementary lateral approach to insert fixation

 

Post Operative

 

NWB for 6/52

 

Bone scan re vascularity 

 

Issue

- °AVN = FWB

- AVN = consider bisphosphonates

 

Yue et al J Orthop Trauma 2001

- 5/54 low blood flow on early SPECT

- no correlation with AVN

 

Complications

 

AVN

 

Related to

- time to reduction <12/24

- velocity of injury

- open reduction vs closed (x4)

- direction (anterior < posterior)

 

Timing

- < 6/24 = 2-10%

- > 12/24 = 52%

 

Direction

- posterior 17%

- anterior 2%

 

Tends to be localised

- revascularisation occurs on reduction

- damage to lateral & medial epiphyseal artery

- metaphyseal blood supply remains

- occurs in first 18 months

 

OA 

 

Incidence

- 15 - 20 %

 

Causes 

- AVN

- instability

- incongruous reduction

- cartilage damage at time of dislocation

 

Philippon et al Arthroscopy 2009

- hip arthroscopy post traumatic dislocation in 14 athletes

- all had chondral defects, 11 had loose fragments

- all patients had labral tears

 

Sciatic Nerve Palsy 

 

Posterior dislocation

- 8 - 19%

- more common after fracture / dislocation

 

Type

- usually partial CPN

- usually resolves

 

Only explore if onset after MUA

 

Else observe

 

Instability < 1%

 

Myostitis Ossificans

 

Uncommon

- usually little functional problem