• What you should know about hip implants

      Total Hip Replacement has proven to be a highly successful procedure for the relief of pain and restoration of function in patients with advanced arthritis.  Because it has been so effective it is now being done, in increasing numbers, in younger patients.  However, we must not forget that it is a mechanical implant and with use and age it tends to wear out and fail.

      One of the modes of failure has been wear of the articular or moving surfaces, namely the ball within the cup.  The original implants used in the United States consisted of a metal ball articulating within a high density polyethylene (plastic) socket.  With time the plastic tends to wear and needs replacement.  This usually occurs within 15 – 25 years.  The newer highly cross-linked polyethylene may last longer.

      There have been attempts to use surfaces that are more durable, namely ceramic on ceramic, or metal on metal.  Ceramic seemed ideal, but for some still undiscovered reason about 10% of the hips produce a loud squeak and their use has decreased.

      Metal on metal replacements have been around for many years and there has always been some concern about high levels of cobalt and chromium ions in the blood.  Studies for this condition have not demonstrated any long term problems.  The use of metal on metal increased as surface replacement, rather than total replacement became more popular in the younger (? Under 65) population.

      Now a new problem has presented.  Particles of cobalt and chromium in the tissues around the hip have caused an inflammatory response that loosens the prosthesis and causes very early failure.  A revision is required and is never as successful as the primary procedure.  Therefore, surgeons must be very cautious in using metal on metal prosthesis and must not be in a rush to operate on younger and younger patients.

      We must never forget the old adage, “Be not the first to try the new or the last to give up the old”

      Marvin S. Gilbert, M.D.
      Clinical Professor of Orthopedic Surgery
      Mount Sinai School of Medicine