Anterior Dislocations of Hip


- Discussion:
    - see frx dislocations of the hip
    - comprise 10-15% of traumatic dislocations of hip;
    - occur when knee strikes dashboard w/ thigh abducted, falls from ht, or from a blow to the back of pt while in squatted position;
    - neck of femur or greater trochanter impinges on rim of acebulum & thereby levers head of femur out of acetabulum thru tear in anterior hip capsule;
    - degree of hip flexion determines whether superior or inferior type of anterior dislocation results;
    - subtypes: obturator, pubic, and iliac
    - inferior dislocation:
          - is result of simultaneous hip abduction, external rotation, & flexion;
          - sharp anterolateral margin of obturator foramen may indent anterosuperior aspect of the femoral head, resulting in the so called indentation frx;
          - assoc injuries include frxs of acetabulum, greater trochanter or femoral head;
    - superior dislocation:
          - results from abduction external rotation, and extension;
          - these mechanisms of anterior dislocations often result in associated femoral head fractures;
          - shear frx of femoral head may occur as femoral head passes superiorly over anteroinferior rim of the acetabulum results in transchondral type of fracture (type IB)

- Diagnosis:
    - may see slight shortening;
    - superior dislocations: (iliac or pubic):
         - hip is extended and externally rotated
         - femoral head is palpable in the vicinity of ASIS;
         - w/ superior dislocations note injury to femoral artery, vein, or nerve;
    - inferior dislocations (obturator, thyroid, or perineal)
         - hip is abducted, externally rotated, and varying deg of flexion;
         - fullness may be palpable in region of obturator foreamen;

- Associated Injuries:
    - femoral head is displaced anteriorly & may compress femoral NV bundle;
    - femoral head frx
         - may occur as often as 75% of cases
         - these will be difficult to diagnos w/o tomograms or CT scans;
         - transchondral frxs:
              - result in nonconcentric reduction require open reduction & either excision or internal fixation of fragment, depending on size and location;
         - indentation frxs: (more common);
              - located on superior on femoral head
              - require no specific treatment;

- Radiographic Findings:
    - on AP find that femoral head is out of the acetabulum in either superior or inferior position;
    - femoral head appears to be slightly larger than on the contralateral side, and the lesser trochanter is in full profile;
    - look for frx of acetabular rim or floor, femoral head, & femoral neck;
    - if of other fracture: get CT;

- Techniques of Closed Reduction
    - Closed Reduction is achieved by traction, followed by extension and internal rotation;
    - Gravity Method of Stimson
    - Allis's maneuver

- Complications:
    - AVN: occurs in approx 10% of anterior dislocations;
    - DJD:
    - Transchondral and Indentation Fractures



Posterior labral tear as a block to reduction in an anterior hip dislocation.

Anterior dislocation of the hip and associated femoral-head fractures.

Traumatic anterior dislocation of the hip in childhood.

Long-term outcome after traumatic anterior dislocation of the hip




Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Thursday, September 6, 2012 11:47 am