“Gail was having awful pain in her right hip which had been worsening for 4-years to the point where she was needing to use a walking stick to mobilise. This was on the background of bilateral metal-on-metal Pinnacle S-ROM total hip replacements which had been in situ for 8-years on the right and 6-years on the left.
For Gail, the greatest challenge was working out the source of her pain. We had to consider loosening, an infection and an adverse reaction to metal debris. This required a very detailed work-up.”
To be checked by PROF
On clinical examination:
Very painful right hip movements
Reduced range of movement on the right
Able to straight leg raise on the right but this caused considerable discomfort
Her oxford hip scores were 17/48 and 29/48 for the right and left hips respectively.
Blood inflammatory markers demonstrated a raised ESR (26mm/Hr) and CRP (10mg/L). Blood metal ion levels demonstrated a normal level of cobalt (2.8ppb) and chromium (3.5ppb). Greater than or equal to 7ppb of either cobalt or chromium is defined as concerning by the MHRA.
Due to her raised inflammatory markers, an aspiration of the right hip was performed however no growth was seen after extended cultures.
Anteroposterior plain radiograph of the pelvis demonstrates bilateral well fixed and well positioned S-ROM Pinnacle MOM hip replacements. Both cups appear stable and well positioned.
Metal artefact reduction sequence (MARS) MRI demonstrating a large pseudotumour posterior to her right hip. This is an area of inflammation secondary to metal debris which can mimic an infective process in the absence of infection.
Gail unfortunately had an adverse reaction to metal debris (ARMD) as a result of the metal on metal (MOM) bearing in used in her right hip replacement.
In the presence of the well fixed Pinnacle cup and SROM stem on the right side, we planned to perform an isolated liner exchange, changing the bearing from metal-on-metal to ceramic-on-polyethylene. As part of the same operation, we aimed to excise Gail’s pseudotumour.
We used a posterior approach to access the right hip and the pseudotumour. We excised as much of the joint lining and the pseudotumour as possible. As with all of our procedures where a possible infection may be the cause, we sent 5 samples of the hip capsule for extended microbiological culture.
We then extracted the femoral head. With an SROM stem this is normally a straightforward task. With other stems, there can be cold welding of the stem to the femoral head. In this case, sometimes you need to perform a full stem extraction in order to change the bearing of the stem. The metal liner was then extracted from the Pinnacle cup using a Depuy alternate bearing extractor.
We completed the procedure by inserting a 52mm polyethylene liner and a 36mm ceramic head with a titanium sleeve. The joint was relocated and then washed out before the musculature, fascia and skin was sutured.
Anteroposterior plain radiograph demonstrating the new liner of the right THR. The head bearing surface is visible on the right side because the right acetabular liner is now made of polyethylene.
Components, such as the acetabular shell and femoral stem, can be retained if they are: well fixed to bone; well orientated; and not infected.
To be completed by PROF
Evidence for this treatment
In closer detail