# CIM Case: Posterior Hip Dislocation ## Clinical Scenario **Patient:** 55-year-old male truck driver **Presentation:** Right hip pain following motor vehicle accident (hitting a cow at 100km/hr), unable to move right leg, brought to ED by ambulance **Relevant history:** Unrestrained driver, dashboard impact to right knee, no loss of consciousness, GCS 15, no other injuries identified in primary survey, no significant past medical history **Examination findings:** - Right lower limb shortened, internally rotated, and adducted (classic attitude) - Flexed hip position - Unable to actively move right hip - Severe pain with any attempted movement - No obvious external wounds - Palpable knee contusion (dashboard injury) - Sciatic nerve examination: Ankle dorsiflexion 5/5, plantar flexion 5/5, sensation intact - Pedal pulses palpable bilaterally - Left hip and both knees appear normal - No spinal tenderness --- ## Investigations Provided ### Laboratory Results | Test | Result | Normal Range | Interpretation | |------|--------|--------------|----------------| | Hb | 138 g/L | 130-180 g/L | Normal | | WCC | 11.2 ×10⁹/L | 4-11 ×10⁹/L | Mildly elevated (stress response) | | Platelets | 286 ×10⁹/L | 150-400 ×10⁹/L | Normal | | Creatinine | 88 μmol/L | 60-110 μmol/L | Normal | | Coagulation | Normal | - | Safe for procedure | | Group & Screen | Complete | - | Available for transfusion | ### Imaging **Image 1: AP Pelvis Radiograph** **Radiological features:** - Right femoral head not in acetabulum - Femoral head appears smaller on right (superior displacement) - Lesser trochanter not visible on right (internal rotation) - Shenton's line disrupted - No obvious acetabular fracture visible on AP view - No obvious femoral head fracture visible - Left hip normal - Pubic symphysis and SI joints intact **Image 2: Post-Reduction CT Scan (after closed reduction)** **CT findings:** - Femoral head concentrically reduced in acetabulum - Small posterior wall fragment (15% of acetabular articular surface) - No intra-articular loose bodies - No femoral head fracture - No other pelvic injuries - Joint space symmetric to contralateral side ## Questions & Model Answers **Diagnosis: Traumatic Posterior Hip Dislocation** **Classic Clinical Presentation:** - **Mechanism:** Dashboard injury with knee striking dashboard, axial load transmitted through femur to hip - **Position:** Shortened, internally rotated, adducted (SIA) - **Pain:** Severe, cannot move hip **Urgency:** | Timing | Importance | |--------|------------| | **Reduce within 6 hours** | CRITICAL - minimises AVN risk | | **0-6 hours** | AVN risk 5-10% | | **6-12 hours** | AVN risk 10-20% | | **>12 hours** | AVN risk 40-50% | **Why Urgent?** | Mechanism | Effect | |-----------|--------| | **Posterior capsule rupture** | Damages blood supply to femoral head | | **Femoral head ischemia** | Medial femoral circumflex artery kinked/stretched | | **Cartilage damage** | Prolonged compression leads to chondral injury | | **Muscle spasm** | Increases difficulty of reduction with time | **Immediate Actions:** | Step | Action | |------|--------| | 1 | **ATLS protocol** - primary survey, secondary survey | | 2 | **AP pelvis X-ray** - confirms dislocation | | 3 | **Document neurovascular status** - especially sciatic nerve | | 4 | **Urgent closed reduction** - within 6 hours | | 5 | **Analgesia and muscle relaxation** - for reduction | | 6 | **Post-reduction imaging** - CT scan mandatory | > **Consultant Tip:** Time to reduction is the SINGLE MOST IMPORTANT factor for AVN. This is an orthopaedic emergency - don't delay for non-essential investigations. **Thompson-Epstein Classification (Posterior Dislocation):** | Type | Description | Prognosis | |------|-------------|-----------| | **I** | Simple dislocation, no fracture | Best | | **II** | Posterior wall fracture, small fragment (single) | Good | | **III** | Posterior wall fracture, large fragment (comminuted) | Fair | | **IV** | Acetabular floor fracture | Poor | | **V** | Femoral head fracture | Poorest | **This Patient:** Likely Type II (small posterior wall fragment on CT) **Pipkin Classification (Femoral Head Fractures with Dislocation):** | Type | Description | Treatment | |------|-------------|-----------| | **I** | Fracture below fovea (infrafoveal) | Excise if small, fix if large | | **II** | Fracture above fovea (suprafoveal) | Fix (weight-bearing area) | | **III** | Type I or II + femoral neck fracture | THA (usually) | | **IV** | Type I or II + acetabular fracture | Fix both | **Associated Injuries to Exclude:** | Injury | Incidence | How to Assess | |--------|-----------|---------------| | **Sciatic nerve palsy** | 10-20% | Document motor/sensory before reduction | | **Femoral head fracture** | 10-15% | CT scan post-reduction | | **Acetabular fracture** | 10-30% | CT scan post-reduction | | **Knee injury (dashboard)** | Variable | Examine knee, X-ray | | **Femoral shaft fracture** | Rare | X-ray femur | | **Ipsilateral femoral neck** | Rare but important | CT scan, review X-ray carefully | **Sciatic Nerve Injury:** - **Peroneal division** most commonly affected (lateral position) - Document BEFORE and AFTER reduction - Footdrop if complete peroneal palsy - Most (70-80%) recover spontaneously > **Consultant Tip:** Always get a CT scan after reduction. You cannot exclude femoral head fracture, loose bodies, or acetabular fracture on plain films alone. **Closed Reduction Techniques:** **Prerequisites:** | Requirement | Rationale | |-------------|-----------| | **Adequate analgesia** | IV opioids | | **Muscle relaxation** | Sedation or general anaesthesia | | **Assistant** | Counter-traction and stabilisation | | **Fluoroscopy available** | Confirm reduction, assess stability | **Technique 1: Allis Manoeuvre (Most Common):** | Step | Action | |------|--------| | 1 | Patient supine on trolley/floor | | 2 | Hip and knee flexed to 90° | | 3 | Assistant stabilises pelvis (downward pressure on ASIS) | | 4 | Operator applies inline traction to femur | | 5 | Gentle internal/external rotation to disengage head | | 6 | Pull hip anteriorly with continued traction | | 7 | Feel/hear "clunk" as head reduces | | 8 | Confirm with X-ray/fluoroscopy | **Technique 2: Stimson Technique:** | Step | Action | |------|--------| | 1 | Patient prone with legs hanging off table | | 2 | Hip and knee flexed to 90° | | 3 | Assistant stabilises pelvis | | 4 | Operator applies downward pressure on calf | | 5 | Gentle rotation to reduce | **Technique 3: Bigelow Manoeuvre (Historical):** - Requires more force, higher complication rate - Rarely used now **Post-Reduction:** | Action | Purpose | |--------|---------| | **X-ray/fluoroscopy** | Confirm concentric reduction | | **Examine stability** | Flex to 90°, adduct - stable? | | **Repeat neuro exam** | Document post-reduction sciatic function | | **CT scan** | MANDATORY - assess for fractures, loose bodies | | **Check range of motion** | Full flexion, extension, rotation | **Criteria for Successful Closed Reduction:** | Finding | Significance | |---------|--------------| | **Symmetric joint space** | Head is concentric | | **Shenton's line restored** | Anatomic position | | **No loose bodies** | On CT | | **Stable to examination** | Won't redislocate | > **Consultant Tip:** If you cannot reduce within 2-3 attempts, go to open reduction. Repeated attempts damage cartilage and increase AVN risk. **Assessment of Posterior Wall Fragment:** **Factors Determining Stability:** | Factor | Stable | Unstable | |--------|--------|----------| | **Fragment size** | <20-25% of posterior wall | >50% of posterior wall | | **Clinical stability** | Stable at 90° flexion | Dislocates at 90° flexion | | **Impaction** | Minimal | Significant articular impaction | | **Comminution** | Single fragment | Multiple fragments | **This Patient:** - 15% posterior wall fragment (small) - Needs dynamic stability assessment under anaesthesia **Dynamic Stability Testing (Under Anaesthesia):** | Test | Technique | Interpretation | |------|-----------|----------------| | **Flexion test** | Flex hip to 90°, apply posterior force | Stable if doesn't subluxate | | **Adduction test** | With hip flexed, adduct | Stable if doesn't subluxate | | **Fluoroscopy** | Watch reduction through ROM | Concentric throughout | **Management Based on Stability:** **If Stable (This Patient Likely):** | Management | Details | |------------|---------| | **Protective weight-bearing** | Non-weight-bearing 6 weeks, then progressive | | **DVT prophylaxis** | Chemical + mechanical | | **Hip precautions** | Avoid extreme flexion, adduction | | **Physiotherapy** | Range of motion, strengthening | | **Follow-up** | Serial X-rays, watch for AVN | **If Unstable:** | Management | Details | |------------|---------| | **Operative fixation** | ORIF of posterior wall | | **Approach** | Kocher-Langenbeck | | **Fixation** | Buttress plate, spring plate, screws | | **Timing** | Within 1-2 weeks ideally | **Indications for ORIF of Posterior Wall:** | Indication | |------------| | Fragment >40-50% of posterior wall | | Instability on dynamic testing | | Incarcerated fragments | | Marginal impaction requiring elevation | | Associated femoral head fracture requiring fixation | > **Consultant Tip:** A small posterior wall fragment with a stable hip on dynamic testing can be managed non-operatively. Size alone doesn't determine need for surgery - stability does. **Complications:** **Early Complications:** | Complication | Incidence | Prevention/Management | |--------------|-----------|----------------------| | **Sciatic nerve palsy** | 10-20% | Document pre/post reduction; most recover | | **Irreducible dislocation** | 5% | Open reduction required | | **Recurrent dislocation** | Rare if stable | Assess stability, fix if unstable | **Late Complications:** | Complication | Incidence | Risk Factors | |--------------|-----------|--------------| | **AVN** | 10-40% | Time to reduction, severity | | **Post-traumatic arthritis** | 20-50% | Articular damage, AVN, instability | | **Heterotopic ossification** | 5-10% | Delayed surgery, multiple attempts | | **Chronic instability** | Rare | Unfixed posterior wall | **AVN Monitoring:** | Timing | Assessment | |--------|------------| | **6 weeks** | X-ray - baseline | | **3 months** | X-ray - early AVN signs | | **6 months** | X-ray - if symptoms, consider MRI | | **12 months** | X-ray - late AVN | | **2 years** | X-ray - final assessment | **AVN X-ray Signs:** | Stage | Findings | |-------|----------| | **Early** | Subtle increased density | | **Intermediate** | Crescent sign (subchondral collapse) | | **Late** | Flattening, collapse, secondary OA | **MRI for AVN:** - Earlier detection than X-ray - Low signal on T1, high on T2 in early AVN - Consider at 6-12 weeks if high-risk patient **Post-Traumatic Arthritis:** | Factor | Effect on OA Risk | |--------|-------------------| | **Time to reduction** | Longer = higher risk | | **Articular damage** | Femoral head or acetabular fracture | | **Incongruent reduction** | Residual subluxation, loose bodies | | **AVN development** | Leads to secondary OA | **Long-Term Outcomes:** | Outcome | Rate | |---------|------| | **Good/Excellent** | 70-80% (simple dislocation) | | **Fair/Poor** | 20-30% | | **THA within 10 years** | 5-15% (higher if complications) | > **Consultant Tip:** AVN may not appear for 1-2 years after injury. Patients need long-term follow-up. Warn them about this risk at the time of injury. **Indications for Open Reduction:** | Indication | Rationale | |------------|-----------| | **Failed closed reduction** | 2-3 adequate attempts | | **Incongruent reduction** | CT shows loose bodies, incarcerated fragments | | **Irreducible dislocation** | Buttonholed capsule, inverted limbus | | **Associated fracture requiring fixation** | Posterior wall, femoral head | | **Non-concentric reduction** | Widened joint space on imaging | **Causes of Irreducible Dislocation:** | Cause | Mechanism | |-------|-----------| | **Buttonhole through capsule** | Femoral head trapped | | **Inverted labrum** | Blocks reduction | | **Loose osteochondral fragment** | In joint | | **Incarcerated posterior wall** | Blocks head | | **Myositis ossificans** | In chronic cases | **Surgical Approach: Kocher-Langenbeck** **Position:** Lateral decubitus or prone **Incision:** - Curved incision from PSIS towards greater trochanter, then distally along femoral shaft **Internervous Plane:** - Between gluteus maximus (inferior gluteal nerve) and gluteus medius (superior gluteal nerve) **Key Steps:** | Step | Action | Structure at Risk | |------|--------|-------------------| | 1 | Incise fascia lata | - | | 2 | Split gluteus maximus | Inferior gluteal vessels | | 3 | Identify sciatic nerve | PROTECT throughout | | 4 | Detach short external rotators | Sciatic nerve (tag and protect) | | 5 | Capsulotomy/assess capsule | - | | 6 | Reduce hip | May need lever or traction | | 7 | Fix posterior wall if needed | - | | 8 | Repair capsule and rotators | Stability | **Protecting the Sciatic Nerve:** | Technique | |-----------| | Identify early and tag | | Keep hip extended during approach | | Retract gently with vessel loops | | Avoid excessive traction | | Keep nerve moist | **Fixation of Posterior Wall:** | Technique | Indication | |-----------|------------| | **Buttress plate** | Large fragments, comminution | | **Spring plate** | Marginal impaction | | **Lag screws** | Simple large fragments | | **Combination** | As needed | **Post-Operative Management:** | Phase | Management | |-------|------------| | **DVT prophylaxis** | Chemical (LMWH) + mechanical | | **HO prophylaxis** | Indomethacin 75mg daily × 6 weeks or radiation | | **Weight-bearing** | Toe-touch 6 weeks, progressive thereafter | | **ROM** | Early passive, protect from instability positions | > **Consultant Tip:** Know the anatomy. The sciatic nerve is the most important structure. Identify it early, protect it throughout, and document its function before and after surgery. --- ## Key Teaching Points ### Pattern Recognition **This pattern suggests Posterior Hip Dislocation:** - Dashboard mechanism (knee strike with hip flexed) - Classic SIA position: Shortened, Internally rotated, Adducted - Severe pain, unable to move hip - High-energy mechanism **Compare with Anterior Dislocation:** | Feature | Posterior | Anterior | |---------|-----------|----------| | **Frequency** | 90% | 10% | | **Mechanism** | Dashboard | Abduction/ER force | | **Position** | SIA (shortened, IR, adducted) | Extended, ER, abducted | | **Associated injuries** | Posterior wall, sciatic nerve | Femoral head, femoral nerve | ### Critical Management Points 1. **Time is critical** - reduce within 6 hours to minimise AVN risk 2. **Document sciatic nerve** - before AND after reduction 3. **CT scan is mandatory** - after reduction, assess for fractures and loose bodies 4. **Assess stability** - dynamic testing under anaesthesia 5. **Long-term follow-up** - AVN may appear up to 2 years post-injury 6. **Open reduction if needed** - don't persist with multiple closed attempts --- ## Common Examiner Follow-ups **Q: "What is the blood supply to the femoral head and why is AVN a concern?"** Blood supply to femoral head: | Artery | Source | Importance | |--------|--------|------------| | **Medial femoral circumflex artery** | Profunda femoris | MAIN supply (80%) | | **Lateral femoral circumflex artery** | Profunda femoris | Minor contribution | | **Ligamentum teres artery** | Obturator | Variable, minor | In posterior dislocation: - Medial femoral circumflex artery is stretched/kinked - Posterior capsule ruptures, further compromising blood supply - Longer dislocation = longer ischemia = higher AVN risk --- **Q: "What associated injuries must you exclude with dashboard mechanism?"** Dashboard injury triad: 1. **Posterior hip dislocation** - as discussed 2. **Patella fracture** - direct impact 3. **PCL injury** - posterior tibial translation 4. **Femoral shaft fracture** - axial load Also consider: - Acetabular fracture - Femoral head fracture - Patellar tendon rupture - Tibial plateau fracture Always examine the ENTIRE limb and obtain appropriate imaging. --- **Q: "The patient develops footdrop after reduction. What is your management?"** Post-reduction sciatic nerve palsy: **Causes:** - Traction injury during reduction - Contusion from dislocation - Incarceration (rare) **Management:** 1. **Document** - which component affected (peroneal vs tibial) 2. **Expectant management** - most (70-80%) recover spontaneously 3. **Splint** - AFO for footdrop 4. **Physiotherapy** - maintain ROM, strengthening 5. **EMG/NCS** - at 6 weeks if no recovery 6. **Observe 12-18 months** - for spontaneous recovery 7. **Consider exploration** - if no recovery and incarceration suspected Most sciatic injuries from dislocation are neuropraxia and recover. Surgery is rarely needed. --- **Q: "How does management differ if there is an associated femoral neck fracture?"** Pipkin Type III - Dislocation with femoral neck fracture: This is a devastating injury: - AVN rate very high (often >50%) - Union of neck fracture compromised - Usually requires total hip arthroplasty Management: - **Young patient:** Attempt reduction and internal fixation of neck (emergently) - **Older patient or delayed presentation:** Primary THA - **Must reduce dislocation first** to assess neck fracture This is one of the worst combinations in hip trauma - counsel patient about poor prognosis. --- ## Related Topics - Acetabular Fractures - Femoral Head Fractures - Hip Dislocation After THA - Kocher-Langenbeck Approach - Sciatic Nerve Injury - AVN of Femoral Head