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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 - PowerPoint PPT Presentation
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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