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    Managing the Number One Complication of THA

    Instability/dislocation remains the number one complication of primary and revision total hip arthroplasty (THA).

    Prevention of dislocation is, of course, easier than treating it. John Masonis, MD, from OrthoCarolina, Charlotte, North Carolina, recently outlined the patient, implant, and surgeon factors that affect whether a patient will be at risk for dislocation following THA and offered his insights on how to manage them.

    But what if, despite your best efforts, the patient dislocates? Dr. Masonis has some advice on that for you, too.

    First-time Dislocation

    • Check the component alignment.
    • If it’s acceptable, consider using a brace or knee immobilizer for 4 weeks.
    • If the alignment is not acceptable, correct the problem (usually cup version). Otherwise, the patient is likely to go on to multiple dislocations.

    Recurrent Instability

    In this situation, Dr. Masonis recommends using all the tools at your disposal, from a modularity standpoint, to ensure that the hip is stable.

    • Maximize stability surgically by going back to the basics.
      • Can you maximize head size better than it currently is?
      • Can you increase the offset of the hips?
      • Should you increase leg length? (Note: Make sure you discuss the tradeoffs with your patient.)
      • Does the patient have a capsular contracture that needs to be released?

    Re-recurrent Instability

    At this point, the goal is stability alone, and bipolar and tripolar constructs will be helpful in achieving that goal. Dr. Masonis offers this trick: Use a 40-mm liner (44 mm if the head size will accommodate it) and put a bipolar construct inside it. He says this is similar to dual mobility constructs, which have little wear data available but are an improvement for stability.

    Constrained liners can be a problem – not all are created equal, but all will fail eventually under strain. If you are using a constrained liner:

    • Know the range-of-motion limits
    • Avoid the snap-on rings on 32-mm heads
    • Remember that tripolar designs seem to function best
    • Know the inner diameter of the cup

    Dr. Masonis noted that if the patient has well-fixed cup, you may be able to cement in a tripolar construct and get out of a difficult situation.