Posterior hip dislocation is an orthopedic emergency requiring reduction within 6 hours to minimize the risk of avascular necrosis (AVN) of the femoral head. [1-2] It accounts for approximately 90% of all traumatic hip dislocations and is most commonly caused by high-energy mechanisms such as motor vehicle collisions ("dashboard injury"). [1][3]
1. History
- Mechanism: High-energy trauma — classic "dashboard injury" (axial force through a flexed knee striking the dashboard), falls from height, sports injuries, pedestrian struck [1][3]
- Lower-energy mechanisms possible in children, elderly, and those with acetabular retroversion or cam morphology [4-5]
- Characterize: time of injury (critical for reduction timing), position of limb at impact, ability to bear weight
- Associated symptoms: severe hip/groin/buttock pain, inability to move the leg, numbness/tingling in the foot (sciatic nerve)
- Important negatives: knee pain (ipsilateral knee ligament injury in ~29% of cases), back pain, abdominal pain (polytrauma) [6]
2. Alarm Features
- Sciatic nerve injury — foot drop, peroneal distribution numbness (occurs in up to 27.5% of posterior dislocations) [6]
- Open dislocation
- Associated femoral neck fracture (risk of iatrogenic displacement during reduction)
- Vascular compromise — absent distal pulses
- Polytrauma with hemodynamic instability
- Delay >6 hours from injury — significantly increases AVN risk (OR 5.6 for AVN when reduced after 12 hours vs. before) [2][7]
- Irreducible dislocation suggesting entrapped fragment or buttonholing through capsule [8]
3. Medications
- Procedural sedation agents:
- Propofol is significantly more effective than fentanyl/midazolam for closed reduction (79% vs. 36% success; p = 0.04) [9]
- Ketamine is an alternative, especially in hemodynamically unstable patients
- Fentanyl/midazolam associated with 6.4× odds of failed reduction and longer time to reduction [9]
- If sedation >6 hours from injury fails, consider general anesthesia with paralysis [10]
- Post-reduction analgesia: NSAIDs, acetaminophen, opioids as needed
- DVT prophylaxis if admitted and non-weight-bearing
- Avoid: no specific contraindicated medications, but be cautious with sedation in polytrauma/TBI patients
4. Diet
- NPO if procedural sedation or operative intervention anticipated
- No specific long-term dietary considerations for this condition
5. Review of Systems
- Neurologic: numbness, tingling, weakness in the affected leg (especially foot dorsiflexion — peroneal nerve)
- MSK: ipsilateral knee pain (dashboard mechanism causes concurrent PCL/meniscal injury in ~29%) [6]
- Vascular: coolness, pallor, or pulselessness of the distal extremity
- GU: urinary symptoms if associated pelvic injury
- Abdominal: pain suggesting intra-abdominal injury in polytrauma
6. Collateral History and Family History
- Witnesses to mechanism (speed of MVC, position in vehicle, seatbelt use, airbag deployment)
- Prior hip surgery, prosthetic hip (prosthetic dislocations are managed differently)
- History of connective tissue disorders or hypermobility (Ehlers-Danlos, Marfan)
- Family history generally not contributory in acute traumatic dislocation
7. Risk Factors
- High-energy motor vehicle collision (most common) [1][3]
- Contact/collision sports (football, rugby, martial arts) [11]
- Acetabular retroversion and cam morphology are independent anatomic risk factors [5]
- Prior hip dislocation or hip dysplasia
- Prosthetic hip (lower energy threshold for dislocation)
- Younger males disproportionately affected (mean age ~43 years) [6]
8. Differential Diagnosis
- Acetabular fracture without dislocation — may mimic on exam; radiographs differentiate
- Femoral neck or intertrochanteric fracture — shortened, externally rotated leg (opposite rotation pattern)
- Anterior hip dislocation — leg held in abduction, external rotation, extension (opposite of posterior)
- Femoral head fracture (Pipkin) — often coexists with posterior dislocation (40% of cases) [6]
- Pathologic fracture through metastatic lesion
- Septic hip — atraumatic, febrile, unable to bear weight
- Slipped capital femoral epiphysis (SCFE) — in adolescents, internally rotated leg
9. Past Medical History
- Prior hip dislocation or subluxation (recurrence rate ~3%) [11]
- Prior hip surgery or prosthetic hip
- Osteoporosis, osteopenia
- Connective tissue disorders
- Chronic conditions affecting sedation risk (cardiac, pulmonary, hepatic)
10. Physical Exam
- Classic presentation: affected leg is shortened, flexed, adducted, and internally rotated [3][12]
- Severe pain with any attempted range of motion
- Palpable femoral head in the buttock (posterior prominence)
- Neurovascular exam is critical:
- Sciatic nerve: test ankle dorsiflexion (peroneal division most commonly affected — 65% of sciatic injuries are isolated peroneal) [13]
- Distal pulses (dorsalis pedis, posterior tibial)
- Sensation in peroneal (dorsal foot) and tibial (plantar foot) distributions
- Examine the ipsilateral knee for effusion, ligamentous laxity (PCL, collaterals)
- Assess for signs of polytrauma (chest, abdomen, pelvis, spine)
11. Lab Studies
- Type and screen — if operative intervention or polytrauma
- CBC, BMP — baseline for sedation and surgical planning
- Coagulation studies if anticoagulated or significant hemorrhage
- Lactate, blood gas — if hemodynamically unstable
- Urinalysis — if pelvic/GU injury suspected
- No specific labs diagnose hip dislocation
12. Imaging
- First-line: AP pelvis radiograph — will show the dislocation in most cases (femoral head superiorly and laterally displaced relative to acetabulum, appearing smaller due to posterior position) [8]
- Pre-reduction CT: generally not recommended as it delays reduction; obtain only if femoral neck fracture is suspected (reduction attempt could displace it) [1]
- Post-reduction imaging:
- AP pelvis and cross-table lateral radiographs to confirm concentric reduction [8]
- CT without contrast is recommended post-reduction to evaluate for intra-articular fragments, joint congruence, and acetabular fracture characterization [8]
- CT sensitivity for intra-articular fragments is 87.3%, though small fragments may be missed [8]
- MRI: useful for detecting AVN (typically at 4–6 weeks post-injury), labral tears, ligamentum teres injury, and soft tissue pathology; particularly valuable in pediatric patients [11][14]
13. Special Tests
- Thompson-Epstein Classification (posterior dislocations):
- Type I: Simple dislocation, no fracture
- Type II: Dislocation with small posterior wall fragment
- Type III: Dislocation with large posterior wall fragment
- Type IV: Dislocation with acetabular floor fracture
- Type V: Dislocation with femoral head fracture
- Pipkin Classification (femoral head fractures with posterior dislocation):
- Type I: Fracture below fovea
- Type II: Fracture above fovea
- Type III: Type I or II + femoral neck fracture
- Type IV: Type I or II + acetabular fracture
- Point-of-care ultrasound (POCUS) can be used to confirm reduction at bedside
14. ECG
- ECG indicated for procedural sedation monitoring
- Obtain baseline ECG in elderly patients or those with cardiac history prior to sedation
- No specific ECG findings associated with hip dislocation itself
- Continuous cardiac monitoring during procedural sedation is standard
15. Assessment
- Posterior hip dislocation is a time-sensitive orthopedic emergency [1][15]
- Outcomes are largely driven by time to reduction and associated injuries: [1-2]
- Reduction within 6 hours: 88% excellent/good outcomes [2]
- Reduction after 6 hours: only 42% excellent/good outcomes [2]
- AVN rate: ~5% for isolated dislocations, up to 35% with associated acetabular fracture-dislocations [16]
- Post-traumatic osteoarthritis develops in ~32% at intermediate follow-up [6]
- Long-term morbidity is significant: only 33% return to pre-injury sports level, ~25% do not return to work [6]
16. Treatment Plan
Initial stabilization
- ABCs, ATLS protocol if polytrauma
- Immobilize the limb in position of comfort; do not force into anatomic position
- Document neurovascular status before and after any intervention
Closed reduction (>90% success rate in ED): [17]
- Procedural sedation — propofol preferred; if dislocation >6 hours, consider general anesthesia with paralysis [9-10]
- Reduction techniques (success rates 60–92%): [17-18]
- Captain Morgan technique (92% success): physician places knee behind patient's flexed knee and lifts anteriorly [19]
- Allis maneuver: inline traction with hip flexed to 90°, assistant stabilizes pelvis
- Stimson (gravity) technique: patient prone, leg hanging off bed, downward pressure on calf
- Whistler technique, Rocket Launcher technique, Hydraulic lift technique — alternatives [18][20]
- Gentle internal/external rotation during traction to disengage the femoral head
- A palpable/audible "clunk" confirms reduction
- If closed reduction fails: CT to evaluate for entrapped fragments → open reduction in OR [8][15]
Post-reduction
- Confirm concentric reduction with radiographs ± CT [8]
- Repeat and document neurovascular exam
- Protected weight-bearing (toe-touch/crutch-assisted) for 2–6 weeks [11]
- DVT prophylaxis during non-weight-bearing period
- Orthopedic follow-up for serial imaging and rehabilitation
17. Disposition
- Admit if:
- Associated fractures (acetabular wall, femoral head/neck — Pipkin or Thompson-Epstein ≥ Type II)
- Failed closed reduction requiring operative intervention
- Sciatic nerve injury
- Polytrauma or hemodynamic instability
- Non-concentric reduction on post-reduction imaging
- Observation/short stay may be appropriate for:
- Orthopedic consultation is required for all native hip dislocations [1]
- Prosthetic hip dislocations may be discharged after successful reduction with orthopedic follow-up if stable
18. Follow-Up / Return Precautions
- Orthopedic follow-up within 1–2 weeks post-reduction
- MRI at 4–6 weeks to screen for AVN of the femoral head [11]
- Follow-up should continue for a minimum of 2 years to detect late AVN [4]
- Protected weight-bearing with gradual progression per orthopedic guidance
- Return precautions — seek immediate care for:
- Increasing hip pain, inability to bear weight
- New numbness, tingling, or weakness in the leg/foot
- Sensation of hip "giving way" or re-dislocation
- Fever (concern for post-traumatic septic arthritis)
- Counsel patients on long-term risks: AVN (10–13%), post-traumatic arthritis (~32%), potential need for total hip arthroplasty (~19%) [6][21]
References
1. Traumatic Hip Dislocation: Pediatric and Adult Evaluation and Management. — Benedick A, Lopas L, Daley E, Jang Y. The Journal of the American Academy of Orthopaedic Surgeons. 2024.
2. Coxarthrosis Following Traumatic Posterior Dislocation of the Hip. — Hougaard K, Thomsen PB. The Journal of Bone and Joint Surgery. American Volume. 1987.
3. Hip Dislocation: Evaluation and Management. — Foulk DM, Mullis BH. The Journal of the American Academy of Orthopaedic Surgeons. 2010.
4. Traumatic Hip Dislocation in the Paediatric Population: A Case Series From a Specialist Centre. — Archer JE, Balakumar B, Odeh A, Bache CE, Dimitriou R. Injury. 2021.
5. Acetabular Retroversion and Cam Morphology Are Contributing Risk Factors for Posterior Hip Dislocation Independent of the Trauma Mechanism. — Jaecker V, Regenbogen S, Shafizadeh S, et al. Archives of Orthopaedic and Trauma Surgery. 2024.
6. Intermediate to Long-Term Results Following Traumatic Hip Dislocation: Characteristics, CT-Based Analysis, and Patient-Reported Outcome Measures. — Jaecker V, Zocholl M, Friederichs J, et al. The Journal of Bone and Joint Surgery. American Volume. 2024.
7. Systematic Review and Meta-Analysis of Avascular Necrosis and Posttraumatic Arthritis After Traumatic Hip Dislocation. — Kellam P, Ostrum RF. Journal of Orthopaedic Trauma. 2016.
8. ACR Appropriateness Criteria® Acute Hip Pain: 2024 Update. — Bartolotta RJ, Ha AS, Bateni CP, et al. Journal of the American College of Radiology : JACR. 2025.
9. Comparing Propofol With Fentanyl and Midazolam for Sedation in Closed Reductions of Traumatic Hip Dislocations. — Lurie BM, Siow MY, Bongbong DN, Mitchell BC, Kent WT. Orthopedics. 2022.
10. Conscious Sedation Versus Rapid Sequence Intubation for the Reduction of Native Traumatic Hip Dislocation. — Bommiasamy AK, Opel D, McCallum R, et al. American Journal of Surgery. 2018.
11. Hip Dislocation and Subluxation in Athletes: A Systematic Review. — Chona DV, Minetos PD, LaPrade CM, et al. The American Journal of Sports Medicine. 2022.
12. Closed Reduction of the Traumatic Posterior-Dislocation of Hip Joint Using a Novel Sitting Technique: A Case Series. — Zhou Y, Zhang C, Zhao S, Wang Q. Medicine. 2018.
13. Nerve Injury With Acetabulum Fractures: Incidence and Factors Affecting Recovery. — Simske NM, Krebs JC, Heimke IM, Scarcella NR, Vallier HA. Journal of Orthopaedic Trauma. 2019.
14. MRI as a Reliable and Accurate Method for Assessment of Posterior Hip Dislocation in Children and Adolescents Without the Risk of Radiation Exposure. — Mayer SW, Stewart JR, Fadell MF, Kestel L, Novais EN. Pediatric Radiology. 2015.
15. Initial Treatment of Traumatic Hip Dislocations in the Adult. — Yang EC, Cornwall R. Clinical Orthopaedics and Related Research. 2000.
16. Avascular Necrosis of the Femoral Head After Traumatic Posterior Hip Dislocation With and Without Acetabular Fracture. — Milenkovic S, Mitkovic M, Mitkovic M. European Journal of Trauma and Emergency Surgery : Official Publication of the European Trauma Society. 2022.
17. Hip Dislocations in the Emergency Department: A Review of Reduction Techniques. — Gottlieb M. The Journal of Emergency Medicine. 2018.
18. Rocket Launcher: A Novel Reduction Technique for Posterior Hip Dislocations and Review of Current Literature. — Dan M, Phillips A, Simonian M, Flannagan S. Emergency Medicine Australasia : EMA. 2015.
19. The Captain Morgan Technique for the Reduction of the Dislocated Hip. — Hendey GW, Avila A. Annals of Emergency Medicine. 2011.
20. A New Technique for Reduction of a Posteriorly Dislocated Hip Joint. — Zwank MD, Kumasaka PG. The American Journal of Emergency Medicine. 2024.
21. Long-Term Outcomes of Traumatic Hip Dislocation: A Minimum 10-Year Follow-Up Study in 18 Patients. — Regenbogen S, Grützner PA, Beck M, et al. Archives of Orthopaedic and Trauma Surgery. 2025.