The issues surrounding raised levels of metal ions in the blood following large head metal-on-metal total hip replacement (THR), such as cobalt and chromium, have been well documented. Despite the national popularity of uncemented metal-on-polyethylene (MoP) THR using a large-diameter femoral head, few papers have reported the levels of metal ions in the blood following this combination. Following an isolated failure of a 44 mm Trident–Accolade uncemented THR associated with severe wear between the femoral head and the trunnion in the presence of markedly elevated levels of cobalt ions in the blood, we investigated the relationship between modular femoral head diameter and the levels of cobalt and chromium ions in the blood following this THR.

A total of 69 patients received an uncemented Trident–Accolade MoP THR in 2009. Of these, 43 patients (23 men and 20 women, mean age 67.0 years) were recruited and had levels of cobalt and chromium ions in the blood measured between May and June 2012. The patients were then divided into three groups according to the diameter of the femoral head used: 12 patients in the 28 mm group (controls), 18 patients in the 36 mm group and 13 patients in the 40 mm group. A total of four patients had identical bilateral prostheses in situ at phlebotomy: one each in the 28 mm and 36 mm groups and two in the 40 mm group.

There was a significant increase in the mean levels of cobalt ions in the blood in those with a 36 mm diameter femoral head compared with those with a 28 mm diameter head (p = 0.013). The levels of cobalt ions in the blood were raised in those with a 40 mm diameter head but there was no statistically significant difference between this group and the control group (p = 0.152). The levels of chromium ions in the blood were normal in all patients.

The clinical significance of this finding is unclear, but we have stopped using femoral heads with a diameter of ≤ 36 mm, and await further larger studies to clarify whether, for instance, this issue particularly affects this combination of components.

Cite this article: Bone Joint J 2014;96-B:43–7.

Introduction: The national comparative audit in 2007 of blood use in primary elective hip replacement, showed a 25% transfusion rate. Of those 93% received two or more units. Orthopaedic surgeons are large users of blood, so reducing blood use, should save costs and reduce risk from unnecessary donor exposure.

Methods: Over two years 221 consecutive primary total hip replacements were performed, on 84 male and 137 female patients, average age 70 years (42–91yrs). For each the Haematinics cell salvage system was used. Throughout the surgery the cell salvage system was used. At the end of the operation all swabs were washed, the washings were salvaged. Iodine/peroxide contaminated washing and swabs were discarded.

Results: Were we using blood at the level suggested by the comparative audit, 55 patients would have received an average of 2.4 units (132 units total). The actual number of patients transfused was 12, receiving an average of two units (24 units total). This is 108 units less with 43 fewer patients receiving allogenic blood. Using a test of proportions using the Normal distribution then the significance probability is extremely small (SP< 0.001) indicating that this group of patients had a significantly smaller number of transfusions than would be expected compared with the National Average. The transfused patients were older (78.9 vs. 69.8, p< 0.01), had a greater Hb drop (45 g/l vs. 31.2 g/l, p< 0.01), had a lower pre-op Hb (121.3 g/l vs. 138 g/l, p< 0.001), and a greater length of stay (12.8 days vs. 5.8 days, p< 0.05). Gender was not significant.

Discussion: Using the cell salvage system leads to a significant reduction in allogenic blood use. It may not be cost neutral once the use of disposables is factored in, but may represent a useful tool to cost effectively reduce allogenic blood use.