Hip Dislocations

Phillip A. Pullen, D.O.

Garden City Hospital

Anatomy

Ball and socket joint The osseous structures are less likely to dislocate

than those of any other joint in the body 90lbs of force is needed to distract the femoral

head from the acetabulum Strong capsular ligaments support the hip joint:

iliofemoral anteriorly and the ischiofemoral ligament posteriorly

The short external rotators are also located posteriorly adding more stability

Anatomy

Blood supply comes mainly from the cervical arteries at the base of the femoral neck which form a ring

The ring is made up of the medial and lateral circumflex arteries

The capital branches pass through the capsule and enter the femoral head just below the articular surface

The largest of the capital branches are the superior and posterior which come from the medial circumflex artery

Anatomy

Lesser contribution to the head comes from the foveal artery via the ligamentum teres (of sufficient size to contribute in about 75% of hips)

Mechanism of Injury

Usually high energy trauma from a MVA Unrestrained occupants are at a much higher

risk than those wearing seat belts Direction of dislocation is dependent on the

direction of the force and the position of the hip as well as the anatomy of the femur

Anterior dislocations are the result of abduction and external rotation forces If hip flexed – inferior dislocation (obturator disloc.) If hip extended – pubic dislocation

Mechanism of Injury

Posterior dislocations occur 9x more frequently than anterior

These occur by a longitudinal force on an adducted hip (fracture may occur depending on the direction the head is forced)

Increased flexion and adduction favors pure dislocation

Upadhyay et al. JBJS 1985 showed decreased anteversion in patients who sustained fracture dislocations and even less in those who had pure dislocations compared to normal control subjects

Associated Injuries

The rule, not the exception One study, 95% of patients had other injuries

necessitating inpatient treatment Suraci, AJ. J. of Trauma 1986

Ipsilateral injuries that commonly occur: femoral head, neck or shaft fractures; acetabular fractures; pelvic fractures; sciatic nerve injury; knee injuries; and foot and ankle injuries

Posterior dislocations: patella fractures and ligament ruptures and knee dislocations due to direct trauma to the knee

Associated Injuries

Rarely anterior dislocations injure the femoral vessels

An associated injury to the thoracic aorta due to the deceleration typically involved in hip dislocations

Careful trauma evaluation is essential for anyone who suffers a hip dislocation

A high index of suspicion must be maintained for all of the above injuries

Pathoanatomy

When there is a hip dislocation the capsule and ligamentum teres must be disrupted

Labral tears and muscular injury occur as well In anterior dislocations the psoas is the fulcrum

and the capsule is disrupted anteriorly and inferiorly

In posterior dislocations the capsule is disrupted inferoposteriorly or directly posterior (depending on flexion)

Classification

Direction: anterior or posterior Central dislocation (old term referring to

an acetabular fracture) Stewart and Milford and Thompson and

Epstein classification schemes are the most widely used

Classifications

Diagnosis

Position of the leg is key to diagnosis In posterior dislocations: leg is flexed,

internally rotated and adducted In anterior dislocations: leg is externally

rotated with varying amounts of flexion and abduction

Careful exam of the entire LE to r/o concomitant injury

Diagnosis

Single AP view is all that is needed to confirm the diagnosis

In posterior dislocations: head will appear small and lie superiorly overlapping the roof

In anterior dislocations: the head appears large and will lie near the obturator foramen or overlap the medial acetabulum

This AP xray needs to be of good enough quality to evaluate the femoral neck and head, the acetabulum and the pelvis for fractures prior to closed reduction maneuvers

Diagnosis

The rest of the standard radiographic w/u is done following reduction

Treatment

Begins with emergent reduction AVN incidence increases with delayed reduction CR should be attempted first unless there is

associated hip or femoral neck fracture The patient should be completely paralyzed to

avoid further cartilage injury during manipulation If this can’t be done (our ER) conscious sedation

can be used

Treatment

Closed Reduction: Post. Dislocations: traction in the flexed position followed

by gentle rotation and adduction -- post reduction the leg is externally rotated and extended to maintain it. (Stimson – pt. prone / Allis – pt. supine)

Ant. Dislocations: traction is applied in line with the femur with gentle rotation and lateral pressure on the medial thigh -- post reduction the leg is internally rotated and adducted to maintain reduction

Regardless of the direction, gentle traction should be maintained to overcome muscle spasm and elastic restraints (jerky motions don’t work)

Treatment

Femoral neck fractures can also be caused by overzealous reduction maneuvers

If CR fails after 2-3 attempts it should be considered irreducible by closed means.

Further attempts will just cause more injury to the cartilage and increase the risk of arthritis

Treatment

Irreducible Dislocations Approximately 2-15% Usual cause is anatomic obstacle In anterior dislocations: buttonholing through

the capsule, interposition of the rectus, capsule, labrum or psoas

In post. Dislocations: piriformis, gluteus maximus, capsule, ligamentum teres, labrum or bony fragment may prevent reduction

Treatment

Irreducible Dislocations Must be reduced open Judet views, inlet and outlet views of the

pelvis and CT study should precede surgery These are to identify coincident bone injury

and possible obstructions to reduction

Treatment

Nonconcentric Reductions Complete and concentric reduction is required To assess this standard views (Judet, inlet/outlet and

AP) and a CT scan (2 mm cuts) must be obtained On plain films: the joint space and the distance from

the head to the ilioischial line medially should be equal to the normal hip

On the CT scan the distance from the ant. Articular surface to the head should be equal to the normal side (.5 mm difference = subluxation)

Treatment

Nonconcentric Reductions These can be caused by a fragment of bone

or cartilage or soft tissue or blood Since small pieces of bone or cartilage can be

missed on plain film, it is essential to get a CT study after reduction of all hip dislocations

Treatment

Surgical Treatment Absolute indications: irreducible dislocations, and

nonconcentric reductions with free intraarticular bony or cartilaginous fragments

Open reduction should be performed from the direction that the hip dislocated

It is imperative that the acetabulum be fully examined for loose bodies before the hip is reduced

Forceful and copious lavage is also useful

Treatment

Surgical Treatment The ligamentum teres often has a fragment of bone

attached to it (can be removed with rongeur) After the joint has been cleaned out, the hip can be

reduced If an associated posterior-wall fracture exists, stability

testing is required After confirmation of reduction, the capsule and soft

tissue injuries are repaired. If the labrum is torn, it should be repaired

Treatment

Surgical Treatment Nonconcentric reductions should be treated

on an urgent, not emergent, basis MRI may be indicated if no osseous block to

reduction is found (more sensitive to labral and other soft tissue injuries)

During the time it takes to obtain appropriate studies the leg should be placed in traction to avoid injury to the articular cartilage

Treatment

Surgical Treatment Small fragments that are seen in the fovea and do not

impinge on the head need not be removed For small fragments that do not require fixation can

be arthroscopically removed Redislocation of the hip is not needed Additional vascular insult is avoided May be used to diagnose labral tears

Regardless of the surgery, concentric reduction should be confirmed on plain radiographs before wound closure

Treatment

Surgical Treatment The final indication for surgery is an unstable fracture-

dislocation Posterior wall fragments of the same size may be

found in both stable and unstable hips Cadaveric studies revealed that hips with 20% to 25%

of the post. Wall displaced were all stable Those with more than 40% to 50% of the wall

displaced were unstable

Treatment

Surgical Treatment The definitive test for stability is a stress test If more than 20% of the post wall is fractured,

stress testing should be performed To measure stability: pt is supine, hip is

flexed to at least 90 degrees, and internally rotated slightly and a post force is applied

Treatment after Reduction

Strict immobilization leads to intraarticular adhesions and arthritis – avoid

Most recommend a temp. period of traction or balanced suspension until the pain subsides (rarely longer than several days)

Controlled PROM with a CPM and early mobilization are beneficial

Extremes of motion should be avoided for 4-6 wks to allow for healing

Treatment after Reduction

The biggest controversy is wt bearing following reduction. (several days to 1 yr have been suggested)

Prolonged non wt bearing may diminish the amount of collapse in those who develop AVN

A delay in full wt bearing of 8-12 wks for pts with risk of collapse is a reasonable time frame (when reduction took place >6 hrs after dislocation)

For pts reduced sooner, PWB can begin when comfortable and advanced as tolerated with FWB usually becoming possible after 2-4 wks

Treatment after Reduction

Rehab should include: strengthening exercises and proprioceptive training

High demand activities should be delayed until the hip strength returns to normal levels

Outcome

Long term prognosis of simple dislocations: excellent or good in 48-95%

Ant dislocations have better long term prognosis than post dislocations

Outcome for individual pts depends mostly on the development of arthritis or AVN (in their absence, prognosis is usually good)

Pts who did heavy work after their injury were found to have higher risk of a poor outcome

Outcome

Most important prognostic indicator is time to reduction (the longer the time the worse the outcome)

Stewart and Milford reported 88% good results if reduced in <12 hours

Brav reported an increase in unsatisfactory results from 22 to 52% if done >12 hrs

Reigstad found no AVN if reduced <6 hrs Hougaard and Thomsen found increased rates

of AVN and arthritis if >6hrs to reduction

Complications

AVN Arthritis Sciatic Palsy Redislocation Myositis

Avascular Necrosis

Occurs in up to 1.7% to 40% of hip dislocations and the rate increases with delay in reduction

If reduced within 6 hours, the incidence of AVN is approximately 2-10%

Cause of AVN is thought to be an ischemic insult to the femoral head

In rabbit models, the revascularization commences at the time of reduction

The natural history of AVN varies: usually appears within 2 years but has been as long as 5 years after injury

Arthritis

Most common problem seen after hip dislocation

Reported in 20% of cases Rates as high as 70% have been

observed after open reduction Most widely held belief is consequence of

cellular injury to the cartilage from the impact causing the dislocation

Sciatic Palsy

More common after fracture-dislocation Usually partial and most often affects the

peroneal division Resolution after reduction generally

occurs Exploration is not required unless nerve

function was intact prior to reduction

Redislocation

Uncommon Reported in only 1% of dislocations Poor healing of the posterior soft tissues

or large labral tears accounts for most cases

Myositis

Calcification of the soft tissues is uncommon after dislocation

It is usually seen as a late complication and does not restrict motion