Hypercalcemia and Kidney Complications from Joint Implants

Introduction: Acute kidney injury after revision knee and hip arthroplasty is common with rates of 20% reported. An uncommon complication for the nephrologist to be aware of is hypercalcemia, which can occur with use of calcium sulfate-based volume expanders i.e. Stimulan. These absorbable drug-eluting beads deliver local antibiotics to manage prosthetic joint infections (PJI). Complications of transient hypercalcemia are reported in 5%, with treatment required in 0.2% of cases. We present a case of symptomatic severe hypercalcemia suspected from Stimulan use. Case Description: A 67 year old male with history of DM, HTN, CKD stage 4, and knee arthroplasty with recurrent PJI who presented for joint revision. His post-op course was complicated by non-oliguric AKI related to perioperative hemodynamic changes with low renal reserve. On POD#3, he had symptoms of constipation, nausea/vomiting; hypercalcemia was noted (Fig 1). Serological workup for hypercalcemia was unrevealing with PTH appropriately low; serum electrophoresis, PTHrp, 25-OH and 1,25-OH Vit D levels were low-normal. OR notes indicated implantation of 20mL stimulan beads during surgery. Interestingly an additional 20mL of stimulan was also implanted 6 months earlier during prior revision. Due to worsening hypercalcemia and renal function despite adequate IV hydration, pamidronate was given at reduced dosing, with subsequent normalization of Ca levels. However, he continued to have rising serum Cr suspected from bisphosphonate use. A renal biopsy showed ATN with 53% global glomerulosclerosis from HTN and 50% IFTA. Discussion: Hypercalcemia has been reported with calcium sulfate-based volume expanders, typically associated with higher bead volumes, e.g. 30-40mL. Many cases are mild and self-resolving up to a reported 2-6 weeks. In 0.2% of cases, severe or persistent hypercalemia requires treatment similar to other causes of severe hypercalcemia including use of bisphosphonates or RANK-L receptor antibodies. Washout of beads may not be beneficial and can exacerbate hypercalcemia from bead agitation.