A patient with primary hyperparathyroidism presenting with hypercalcemia and elevated intact parathyroid hormone who is scheduled for elective knee replacement—should she undergo parathyroidectomy before the knee surgery?

Should Parathyroidectomy Precede Knee Replacement in Primary Hyperparathyroidism?

Yes, this patient should undergo parathyroidectomy before knee replacement surgery. With a serum calcium of 11.1 mg/dL (>1 mg/dL above the upper limit of normal) and confirmed primary hyperparathyroidism, she meets established surgical criteria and faces significant perioperative risks if hypercalcemia is not corrected before elective orthopedic surgery. 1, 2

Rationale for Surgical Priority

Established Surgical Indications Are Met

• This patient's calcium of 11.1 mg/dL exceeds the surgical threshold of >1 mg/dL above the upper limit of normal (>10.3 mg/dL), which is a clear indication for parathyroidectomy regardless of symptoms. 1, 3

• The combination of hypercalcemia (11.1 mg/dL) with elevated intact PTH (100 pg/mL) confirms primary hyperparathyroidism and establishes the need for definitive surgical treatment. 1, 3

• Parathyroidectomy is the only definitive curative therapy for primary hyperparathyroidism and is recommended even in asymptomatic patients due to the potential negative effects of long-term hypercalcemia. 2

Perioperative Risk Mitigation

• Hypercalcemia significantly increases perioperative complications during major surgery, including cardiac arrhythmias, impaired wound healing, increased infection risk, and acute kidney injury—all of which can compromise outcomes after total knee replacement. 3

• Moderate hypercalcemia (10.6–12 mg/dL range) causes polyuria, polydipsia, nausea, vomiting, myalgia, and confusion, which can complicate postoperative recovery and rehabilitation after orthopedic surgery. 3

• Normalizing calcium levels before elective surgery reduces the risk of perioperative cardiovascular events, as primary hyperparathyroidism is recognized as a secondary cause of hypertension. 2

Surgical Approach and Timeline

Preoperative Localization

• Ultrasound of the neck combined with 99mTc-sestamibi scintigraphy with SPECT/CT should be obtained to enable minimally invasive parathyroidectomy, which offers shorter operative times and faster recovery. 1, 2

• Accurate preoperative localization of a single parathyroid adenoma facilitates minimally invasive parathyroidectomy rather than bilateral neck exploration, reducing surgical morbidity and recovery time. 2

Expected Surgical Outcome

• Minimally invasive parathyroidectomy with intraoperative PTH monitoring is the appropriate approach for patients with a single adenoma, allowing immediate confirmation of adequate removal of hyperfunctioning tissue. 2

• Patients should be referred to high-volume, experienced parathyroid surgeons, as outcomes—including cure rates and complication profiles—are significantly better with specialized expertise. 2

Postoperative Management Considerations

• Ionized calcium should be monitored every 4–6 hours for the first 48–72 hours after parathyroidectomy to detect hungry bone syndrome, which can occur after removal of hyperfunctioning parathyroid tissue. 2, 3

• If ionized calcium drops below 0.9 mmol/L postoperatively, intravenous calcium gluconate infusion at 1–2 mg elemental calcium/kg/hour should be initiated, with transition to oral calcium carbonate 1–2 g three times daily plus calcitriol up to 2 μg/day once oral intake is tolerated. 2, 3

Timeline for Knee Replacement

Recommended Interval

• The knee replacement should be scheduled 4–6 weeks after parathyroidectomy to allow for:
  • Biochemical normalization of calcium and PTH levels 3
  • Resolution of any postoperative hypocalcemia or hungry bone syndrome 2, 3
  • Confirmation of surgical cure with repeat calcium and PTH measurements 1
  • Optimization of bone metabolism before orthopedic intervention 2

Verification of Cure

• Serum calcium and intact PTH should be measured 2–4 weeks after parathyroidectomy to confirm biochemical cure before proceeding with elective knee surgery. 3

• Normal postoperative calcium levels (8.6–10.3 mg/dL) and appropriately suppressed PTH confirm successful parathyroidectomy and clearance for subsequent elective surgery. 3

Common Pitfalls to Avoid

• Do not proceed with knee replacement while hypercalcemic, as this significantly increases perioperative morbidity and mortality from cardiac, renal, and wound-healing complications. 3

• Do not attempt medical management alone (bisphosphonates, cinacalcet) as a bridge to knee surgery in a patient who meets clear surgical criteria for parathyroidectomy, as this does not address the underlying disease and provides only temporary calcium control. 2, 4

• Do not delay parathyroidectomy based on the misconception that mildly elevated calcium (11.1 mg/dL) is "not severe enough"—this level exceeds established surgical thresholds and warrants definitive treatment. 1, 5, 6

• Ensure vitamin D status is assessed and optimized (>20 ng/mL) before surgery, but do not use calcitriol or active vitamin D analogs, as these can worsen hypercalcemia in primary hyperparathyroidism. 1, 3