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THR: Trial Reduction



- See: THR dislocation:

- Checklist:
    - need complete muscular relaxation;
    - irrigate any debris from acetabulum;

- Difficult Reduction:
    - capsule might have to be further released, esp if head and neck segment was short preoperatively;
    - if reduction is not possible & leg is lengthened, then recut neck;

- Leg Length:
    - note position of trial head relative to greater trochanter (& compare this distance to that templated from x-rays);
    - replace drill bit into greater troch & measure distance Steinman pin;
    - finally note degree of telescoping of thigh w/ traction;
         - a loose hip is usually result of high placement of the cup, inadequate femoral neck length, or short neck prosthesis;

- Anterior Instability:
    - if hip cannot be brought into full extension then use shorter neck;
    - if there was a severe flexion contracture preop, release psoas tendon;
    - in extension & neutral abduction, there should be no impingement of posterior polyethylene rim at 45 deg of external rotation;
         - consider 20 deg lipped liner is substituted to relieve impingement;
    - posterior trochanter:
         - if trochanter is located posteriorly, as in DDH, postraumatic disorders, hypertropic arthritis
         - perform osteotomy of greater trochanter & transfer it laterally;
         - w/ impingment in external rotation, consider removing bone from the posterior greater trochanter;

- Posterior Instability:
    - at 90 deg of flexion & neutral abduction, internal rotation should be w/o impingment or instability to at least 45 deg,
    - note point of subluxation w/ hip in flexion, adduction & Int. rotation;
         - look for anterior osteophytes which might cause impingement and subsequent posterior subluxation;
              - also that impingment results from too short femoral neck;
         - if hip dislocates easily & head can be manually distracted from socket > few milimeters, then use longer neck length;
         - use longer neck, becuase femoral component has angle < 45 to horizontal, hence longer neck increases offset > verticle ht;
    - if excessive lengthening of extermity would result from longer neck length, then osteotomize greater troch & transfer it distally to help 
         stabilize the hip;
         - also consider recutting femoral neck & then increasing neck length

- Impingement in Abduction:
    - remove a small amount of bone from tip of greater trochanter