Particularly important for the patient whose femoral neck fracture has been treated with arthroplasty are efforts to reduce the risk of dislocation of the hip prosthesis. This risk is highest during the first weeks after arthroplasty, and appears to be higher with posterior and posterolateral surgical approaches. Prosthetic dislocations, occurring 2-6% or more in recent reports, are serious complications that often significantly compromise medical as well as functional outcomes.
Properly positioned prostheses, and appropriate soft-tissue tension are important intra-operative measures to reduce the dislocation risk. Postoperatively, avoidance of excessive hip flexion, adduction and extremes of rotation, at least for the first 6 weeks or so, are considered important. The patient, and her care givers, should be advised about avoiding low chairs, sitting with legs crossed, and encouraged to use additional support when arising from a sitting position. Toilet modifications may be necessary.
Dislocation precautions depend upon the surgical approach. After posterior approaches, it is important to avoid flexion > 90°, adduction, and internal rotation. After anterolateral approaches, extreme external rotation and hyperextension should be avoided, as well as adduction.