CASE 34: Revision for adverse reaction to metal debris (ARMD) using a non-modular long femoral stem
The Story
“This case was a male aged 55, who was fit and well, living with a left sided metal-on-metal modular neck Symbios total hip replacement.
He presented with a history of 6 weeks of left lumbar back pain and an incident of hearing a crack in the left hip region while pulling up his trousers causing increased pain.
The Investigation
On examination, the patient had a negative Trendelenburg test, he had a good range of motion in both hips and was able to straight leg raise on both sides. The left hip movements were apprehensive and caused some groin pain.
His inflammatory markers (CRP and ESR) were normal but his blood cobalt level was very high at 89ppb.
The Evidence
Pre-op AP Radiograph This anteroposterior (AP) pre-operative radiograph shows a well-fixed and well-sized metal on metal modular neck hip replacement with some proximal femoral osteolysis.
Pre-op Lateral Radiograph shows a united fracture of the lesser trochanter, which may explain the crack the patient heard.
An MRI scan showed a thick walled psuedotumour compatible with an adverse reaction to metal debris. There with no muscle wasting present on the MRI scan.
The Diagnosis
Adverse reaction to metal debris causing a thick walled psuedotumour to form surrounding the left prosthesis. Additionally, this patient has suffered from a fracture to the lesser trochanter on the left hand side.
The Treatment
Left hip revision surgery to replace the current Symbiosis with a long stem Corail and a ceramic-on-polyethylene bearing.
The components were well fixed at the point of operation.
There was a considerable amount of fluid as well as bone and soft tissue necrosis, however samples were negative for infection.
A large 54mm Pinnacle Gription socket was used with a polyethylene liner for a 36mm femoral head.
Extended trochanteric osteotomy was required to remove the stem.
A long Corail was used with a ceramic head.
The Outcome
This post-operative AP radiograph shows a long stem corail within the left femur articulating with a Pinnacle Gription socket. Evidence of the extended femoral osteotomy to remove the exiting stem can be seen, and the wires are in place to hold the bone fragments together until they heal.
The Verdict
Modular necks create more taper junctions within a prosthesis, which provides areas for corrosion and the release of metal ions. This, in some patients with a high metal ion load, can lead to adverse reactions to metal debris (ARMD).
The patient was able to return to playing 18 holes of golf while “forgetting” he had a left hip revision,
He had a good range of pain free motion in both hips .
His cobalt and chromium levels have reduced over time too to a cobalt of 1.7ppb and a chromium of 9.3ppb.
