We carried out a cross-sectional study with analysis of the demographic, clinical and laboratory characteristics of patients with metal-on-metal hip resurfacing, ceramic-on-ceramic and metal-on-polyethylene hip replacements. Our aim was to evaluate the relationship between metal-on-metal replacements, the levels of cobalt and chromium ions in whole blood and the absolute numbers of circulating lymphocytes. We recruited 164 patients (101 men and 63 women) with hip replacements, 106 with metal-on-metal hips and 58 with non-metal-on-metal hips, aged < 65 years, with a pre-operative diagnosis of osteoarthritis and no pre-existing immunological disorders.

Laboratory-defined T-cell lymphopenia was present in13 patients (15%) (CD8⁺ lymphopenia) and 11 patients (13%) (CD3⁺ lymphopenia) with unilateral metal-on-metal hips. There were significant differences in the absolute CD8⁺ lymphocyte subset counts for the metal-on-metal groups compared with each control group (p-values ranging between 0.024 and 0.046). Statistical modelling with analysis of covariance using age, gender, type of hip replacement, smoking and circulating metal ion levels, showed that circulating levels of metal ions, especially cobalt, explained the variation in absolute lymphocyte counts for almost all lymphocyte subsets.

1. Seventy-four patients over the age of seventy with either subcapital or intertrochanteric fracture have been investigated for evidence of osteomalacia. To establish an index of suspicion the incidence of biochemically defined osteomalacia has been compared with quantitative histology in this group.

2. Whereas no significant difference in the incidence of the disease was noted in the comparison of subcapital with trochanteric fracture groups, there was a high incidence of osteomalacia overall. Furthermore, a subclinical form of the disease appears to exist.

3. The relevance of these observations is discussed with particular reference to the established diagnostic criteria of the condition.