Title: “Neuropsychiatric symptoms following metal-on-metal implant failure with cobalt and chromium toxicity”
Many metal-on-metal (MoM) total hip replacement implants have been recalled due to high failure rates. This study assesses the mental health of 10 patients who underwent revision surgery for failed MoM implants. The authors believe this is the first study to find a correlation between mental health complications and implant-caused cobalt and chromium poisoning.
Before undergoing revision surgery, 9 patients had toxic levels of chromium and cobalt in their blood. The authors diagnosed all 9 patients with depression; 3 of them were already being treated for depression. 7 out of 9 patients showed short-term memory loss and possible dementia.
The authors found a high incidence of cognitive disability and depression among patients who suffered from implant-caused metal poisoning (metallosis).
MoM implants, which have a metal ball and socket, have been very popular in total hip replacement and hip resurfacing surgeries. When the components of MoM implants rub together over time, they release metal debris into patients’ bodies; this can lead to cobalt and chromium metal poisoning and require patients to undergo revision surgery.
High cobalt and chromium levels in the blood have been known to damage the way that visual stimulation is transmitted to the brain, among other disastrous effects.
Neurological problems, such as changes in brain structure and function, have been associated with high levels of cobalt and chromium in the blood following MoM hip replacement surgery.
Although some papers describe the physical effects of implant-caused cobalt and chromium poisoning, the authors believe this is the first paper to carefully describe the psychiatric problems associated with MoM implants.
This study looked at patients who received their original MoM implants between 2005 and 2009. All 10 patients underwent revision surgeries between 2008 and 2012 and were assessed for mental health in 2014 and 2015.
All patients received DePuy ASR hip implants; specifically, they received the acetabular implant, the taper sleeve adaptor, and unipolar femoral implants.
Patients’ brain function (or cognition) was evaluated using the Mini-Mental State Examination (MMSE) questionnaire. This exam gives a maximum score of 30, and most people up to age 85 have an average score of 28. A score of 25 or less in patients aged over 65 indicates cognitive disability and possible dementia.
Patients’ moods were evaluated using a questionnaire called the Beck Depression Inventory (BDI). A BDI score above 12 is high enough to diagnose depression.
The patients’ average age was 60.5 years. Six patients were female, four were male. On average, patients received the implants at age 52.5 and had them for an average of 4.44 years before undergoing revision.
Observed metallosis: Nine patients’ bloodwork was analyzed prior to undergoing revision surgery, and they all had toxic levels of cobalt and chromium in their blood. Their average chromium levels were 338 nmol/l; normal chromium levels are below 134.5 nmol/l. Their average cobalt levels were 669.4 nmol/l; normal cobalt levels are below 119 nmol/l.
The authors received the post-revision surgery bloodwork for only 3 patients. Two of these patients had acceptable metal levels in their blood. One patient still had toxic metal levels in his blood; his cobalt levels were normal, but his chromium levels were still high at 173 nmol/l.
Observed mood and cognitive function: The patients had moderately severe depression with an average BDI score of 27.6. Such high rates of depression are unusual.
There were significant cognitive abnormalities among the patients; their average MMSE score was 24.2. Seven out of 10 patients had short-term memory loss. This means that 70% of the patients showed signs of early-onset dementia, which is extremely unusual because only .00081% of the general population suffers from early-onset dementia. Additionally, some patients suffered from disorientation, concentration issues, and difficulty finding words.
The patient with the highest pre-revision surgery levels of chromium (664 nmol/l) and cobalt (2470 nmol/l) had the lowest MMSE score.
Patient vignettes: The authors provide more detail on 4 of the 9 patients, who will be referred to as Ms. X, Mr. Y, Mrs. Z, and Mrs. A.
Ms. X felt anxious, guilty, was tearful, had an unstable mood, and had a lowered self-esteem. She had a perfect dementia score (30), but a very high depression score (33) even though she was being treated for depression.
Mr. Y complained of social withdrawal, poor concentration, memory loss, and increased irritability, among other problems. His dementia score was lower than average (26), and his depression score was also very high (30) even after being treated for depression.
Mrs. Z complained of low mood, emotional instability, forgetfulness, a tendency to repeat herself, and inability to feel pleasure, among many other things. She was disoriented in person. She had a very low dementia score (17) and a significantly high depression score (38) even after being treated for depression.
Mrs. A had the highest pre-revision surgery metal levels (664 nmol/l of chromium and 2470 nmol/l of cobalt). She complained of chronic pain, low mood, low self-confidence, difficulty recalling words, inability to feel pleasure, and anxiety, among other things. She was unable to spell the word “world” backwards. She had significant cognitive abnormalities, a very low dementia score (18) and a very high depression score (33).
This study finds a strong connection between depression, cognitive problems, and cobalt and chromium poisoning following a failed MoM implant.
Depression might be caused by the psychological impact of undergoing revision. Patients frequently reported fear of the need for further surgery and insecurity about pain and mobility.
Chromium and cobalt toxicity may have caused permanent but unchanging brain damage in the patients, which in turn may have caused the cognitive problems. Alternatively, metal poisoning may have triggered early onset dementia in these patients.
All doctors should assess the mental health of patients who received metal on metal implants. Additionally, patients who show signs of cognitive impairment should have their chromium and cobalt levels tested.
The authors urge that patients undergo revision surgery immediately after metal poisoning is detected, as this is the only way to fix elevated cobalt and chromium levels.
This study’s findings suggest that, in the future, patients with metal on metal implants might require care for dementia caused by cobalt poisoning. The authors recognize that public safety is jeopardized by MoM implants.
Green et al. BMC Psychiatry (2017) 17:33.
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