Poster Presentation ESA-SRB-ANZOS 2025 in conjunction with ENSA

Bioabsorbable bone substitutes have been used in orthopaedic surgery for the last century, providing a low cost and readily available osteoconductive alternative to autografting. Calcium sulfate beads, such as Stimulan, offer the additional benefit of delivering local antibiotic therapy in deep bone infections.⁽¹⁾ This is especially important with increasing incidence of periprosthetic joint infections (PJI) and the global increase in infections caused by antibiotic-resistant bacteria.⁽²⁾ With increasing use of Stimulan, a few cases are emerging of subsequent hypercalcaemia.^(3-11) (Table 1)

We present a case of a 71-year-old Caucasian male who had a stage 1 revision procedure for an acute, delayed right knee PJI. He developed PTH-independent hypercalcaemia to 2.92 mmol/L on day 3 post-operatively, with associated acute kidney injury. He was otherwise asymptomatic. He had no known history of calcium, endocrine, kidney or malignant disorders. He was not on any medications that cause hypercalcaemia. Notably, his pre-operative calcium and kidney function had been in the normal range. Four boxes of Stimulan were used intra-operatively.

Initial bloods investigating the cause of hypercalcaemia are outlined in Table 2, excluding primary hyperparathyroidism, thyroid disease, myeloma and granulomatous disease as causes. He was treated with aggressive intravenous fluids with good response. Bisphosphonate therapy was avoided due to the likely transient nature of the cause. Intravenous fluids were weaned at day 13 (after failing initial wean on day 7). His hypercalcaemia resolved 2 weeks post-operatively.

This case illustrates the potential for transient PTH-independent hypercalcaemia following the use of Stimulan, with onset 3 days post-operatively and resolution 2 weeks post-operatively. This is the first report of hypercalcaemia following Stimulan in Australia, with only limited literature in the US, UK and Europe. Recognition of Stimulan as a potential cause will allow for appropriate timely intervention in severe cases and provide reassurance given the time-limiting natural history.