Hip Dislocations

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

Hip Dislocations