Research Title: Pseudotumor in Large-Diameter Metal-on-Metal Total Hip Articulation
This case study focuses on a patient who experienced pain in her hip following a large-diameter metal-on-metal (MoM) hip replacement. She also developed a pseudotumor, which is an abnormal swelling of tissue that resembles a tumor.
MoM hip implants are thought to be more stable and durable than metal-on-plastic implants, so they’ve become a popular choice for patients undergoing total hip replacement or hip resurfacing surgery in the United States.
However, MoM implants can cause conditions like an adverse reaction to metal debris (ARMD) and metallosis. ARMD is a form of implant failure that happens when the device sheds metal debris and causes negative effects like pseudotumors and collections of fluid around the implant. Metallosis is a type of metal poisoning that occurs when the implant’s metal debris raise the amount of metal in patient’s blood.
This patient developed a pseudotumor five months after receiving a Biomet Magnum device with the Taperloc femoral stem. Her complications have been observed in other cases.
A 39-year-old woman came to the authors with a 2-year history of hip pain. She had previously experienced bone tissue death in her left femur (a condition called avascular necrosis) but did not have any other medical problems. Prior to developing avascular necrosis, she was very physically active. She underwent total hip replacement surgery and received a Biomet Magnum device with the Taperloc femoral stem.
Right after her surgery, she made a full recovery, reported no pain, had full strength in her hip, and had a full range of motion in her hip. Three months after surgery, she began to feel pain in her left leg. Four months after surgery, she felt squeaking and popping in her hip.
Five months after surgery, she had such severe pain in her left hip, groin, and buttocks that she used crutches and could not go to work. She had swelling in her left hip and thigh. Her hip was weak and had impaired mobility. X-Rays revealed that her implant was not loose and had not moved. Her device’s femoral stem had an angle of 11.3 degrees, and the shell had an angle of 9.7 degrees. Blood tests indicated that she was experiencing inflammation but no infection.
The doctors took a sample of fluid from her left hip and found a liquid that looked like coconut milk with some yellow grains in it, but it had no signs of infection. Analysis showed that the fluid had chromium levels of 707.6 μg/L of chromium, titanium levels of 60 μg/L, and cobalt levels of 1068 μg/L. These levels are much higher than what is considered acceptable or healthy.
The patient underwent revision surgery because of these unusual and painful symptoms. During the surgery, doctors found a pseudotumor surrounding the implant and removed it. The doctors also found a type of dead tissue that resembled cheese. This tissue was sent for analysis but showed no sign of infection. Another tissue sample appeared to have an impaired blood supply and scarring. An analysis of the tissue surrounding the implant also showed impaired blood supply and scarring.
The patient received a metal-on-plastic implant during revision. The components were the Converge titanium acetabular shell, the Durasul Polyethylene insert, and the Biomet head. Two years after revision surgery, the patient had no negative symptoms other than occasional severe sharp pain in her left hip groin.
This patient’s Biomet implant failed because of its metal on metal bearing surface. The levels of chromium and cobalt in the fluid surrounding her hip joint were extremely high.
Pseudotumors are caused by implants shedding metal debris into patients’ bodies as they wear down. The release of metal debris might be related to the positioning of the implant’s components, implant devices rubbing together abnormally, the types of metal in the implant, the thickness of the implant components, and other factors.
The doctors believe the device failed because the femoral neck of the implant was excessively rotated forward (21 degrees). They believe this positioning caused the implant to wear down rapidly and shed metal particles.
This patient’s chromium levels were 18 times higher than the average measurements of other reports, and her cobalt levels were 13 times higher.
One of the authors has stopped using large-diameter MoM implants as his go-to device for hip replacement patients because he has seen way too many complications from the implants. The author has had to revise 25 implants because the implants failed to attach to the patients’ bone and caused the patients severe pain. None of the implants the author has given have dislocated. The author now only uses one brand of implant for MoM hip replacements because he has not experienced any complications with it.
Doctors need to monitor MoM implant patients very carefully, and they need to be very mindful of the way they position the implant because it can mean the difference between failure and success. Additionally, cup inclination should not exceed 50 degrees sideways and 20 degrees forward. The author also believes that large-diameter MoM hip replacement could still be used to treat degenerative hip diseases, but doctors must be very mindful of their implant choice and surgical techniques to prevent failure.
Shahrdar, C. The Journal of Arthroplasty, Vol. 26 No. 4 2011.
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