What is the most common site of hip dislocation?

Explanation

## Hip Dislocation: Frequency and Mechanism **Key Point:** Posterior hip dislocation accounts for approximately 80–90% of all hip dislocations, making it by far the most common type. ### Mechanism of Posterior Dislocation Posterior dislocation typically occurs when: 1. The hip is flexed and adducted 2. A posterior-directed force is applied (e.g., dashboard injury, fall on flexed knee) 3. The femoral head is driven posteriorly out of the acetabulum ### Comparison of Hip Dislocation Types | Type | Frequency | Mechanism | Associated Injury | | --- | --- | --- | --- | | **Posterior** | 80–90% | Flexion + adduction + posterior force | Acetabular fracture, sciatic nerve injury | | **Anterior** | 10–20% | Abduction + external rotation + anterior force | Femoral head fracture, obturator nerve injury | | **Superior** | <1% | Rare; high-energy trauma | Pelvic fracture | | **Inferior** | <1% | Extremely rare | Pelvic involvement | ### Clinical Pearl **High-Yield:** Posterior dislocation is classically associated with **sciatic nerve injury** (in ~10% of cases) and **acetabular fracture**. The classic examination finding is the **flexed, adducted, internally rotated hip** (FADI position). ### Mnemonic **FADI = Flexed, ADducted, Internally rotated** → Posterior dislocation (most common). **Tip:** In exam vignettes, if a patient has a motor vehicle accident with the knee striking the dashboard while the hip is flexed, think posterior hip dislocation with possible sciatic nerve injury and acetabular fracture.