SAT-490 Severe Hypercalcemia after Revision of Septic Left Total Knee

Background Antibiotic-loaded calcium sulfate beads have been used in the treatment and prevention of periprosthetic joint infection. We present the case of a 58 year old female who developed severe hypercalcemia after implantation of calcium sulfate beads. Clinical Case 58 year old woman with history of acromegaly s/p resection with subsequent panhypopituitarism. She had total knee arthroplasty however two months after surgery, continued to have mild pain and drainage from the surgical wound. She underwent revision of left total knee and implantation of calcium sulfate beads. Serum calcium was within normal limit at baseline but in post-op day 2 a gradual increase in calcium was noted with a peak of 13.6 (8.4-10.3 mg/dl) and ionized calcium 1.88 (1.07-1.33 mmol/l) on post-op day 4. Work-up to determine cause was done: FT4 1.82 (0.7-1.9 ng/dl) , PTH 9.2 (11-68 pg/ml), Phosphorous 2(2.5-4.5mg/dl), PTHrP <2 pmol/l, 25 Vitamin D 29.6 (30-100 ng/ml), 1,25 Vitamin D 11.9 (19.9-79.3 pg/ml), Vitamin A 41.6 (33.1-100 ug/dl), SPEP and UPEP revealed normal protein pattern. She had non-PTH mediated hypercalcemia and after ruling out other causes, we concluded that likely cause is the calcium sulfate beads. She was treated with IV NS, calcitonin and pamidronate. Despite aggressive intravenous fluids, she developed acute renal failure. Due to persistent hypercalcemia, joint aspiration was done on day 6 to decrease calcium load. Her serum calcium started to trend down by post-op day 8 and returned to normal 9.7 mg/dl on post-op day 10. Her renal function also improved but has yet to return back to normal. Discussion Antibiotic-loaded calcium sulfate beads are being used more frequently to prevent and treat infected prosthetic joints. Development of acute hypercalcemia following implantation of these antibiotic beads should be monitored and work up to establish non-PTH mediated hypercalcemia should be initiated. Aggressive IV fluids is very important. It is still not well understood why these beads cause hypercalcemia however, one theory postulates that it maybe due to placement of majority of the beads in adjacent vascular soft tissue. Considering this theory, early arthrocentesis should be contemplated. Conclusion Antibiotic-loaded calcium beads have been adopted as an effective way for the local delivery of antibiotics to infected prosthetic joints. Hypercalcemia is a rare but important risk to consider in patients especially those with renal disease. It is recommended that baseline calcium and renal function be measured and monitored post-operatively. Reference 1.Kallala R et al. Hypercalcemia following use of antibiotic-eluting absorbable calcium sulphate beads in revision arthroplasty. Journal of Bone Joint, 2015.