Abstract
Aims: Cobalt (Co) and chromium (Cr) ion associated carcinogenesis and chromosomal damage in animals have raised concerns that metal-on-metal (MOM) total hip replacement (THR) in humans may produce the same effects over time. Considering that the risks may be related to the level of these ions in the body, this study compared the serum Co and Cr levels in patients with unilateral versus bilateral 28 mm diameter MOM THR.
Methods: All patients having THR at our institution were prospectively registered on a computerised database. From our database, 108 Ultima MOM THR with 28 mm CoCrMo bearing were identified. After patient review in clinic and before blood results were known, patient matching was performed by date after surgery, activity level and weight. Using these stringent criteria, 11 unilateral THR could be adequately matched with 11 bilateral THR. Blood serum was taken with full anti-contamination protocols and serum analysed via inductively coupled plasma mass spectrometry (ICP-MS) Statistical analysis used the Mann-Whitney U test.
Results: The median serum Co level after unilateral MOM THR was 22 nmol (range 15 to 37 nmol) compared to 42 nmol (range 19 to 221 nmol) for bilateral MOM THR (p=0.001). The median serum Cr level after unilateral MOM THR was 19 nmol (range 2 to 35 nmol) compared to 52 nmol (range 19 to 287 nmol) for bilateral MOM THR (p=0.04).
Conclusions: This study has shown that the serum Co and Cr levels in patients with bilateral MOM THR are significantly higher than those with unilateral MOM THR. With levels of up to 50 times the upper of limit of normal, this finding may be of relevance for the development of potential long-term side effects.
Theses abstracts were prepared by Mr Peter Kay. Correspondence should be address to him at The Hip Centre, Wrightington Hospital, Appley Bridge, Wigan, Lancashire WN6 9EP.
