Underdiagnosis of primary hyperparathyroidism in patients with osteoarthritis undergoing arthroplasty.

BACKGROUND: Primary hyperparathyroidism (HPT) is commonly underdiagnosed and undertreated. Joint pain is a nonspecific symptom associated with osteoarthritis or primary HPT. We hypothesize that patients treated for osteoarthritis are underdiagnosed with primary HPT. METHODS: Adult patients diagnosed with hip/knee osteoarthritis at the Medical College of Wisconsin from January 2000 to October 2020 were queried. Patients with a calcium level drawn within 1 year of diagnosis of osteoarthritis were included. Patients who had undergone prior parathyroidectomy were excluded. Patients were stratified by serum calcium level, HPT diagnosis, and PTH level. Arthroplasty rates were compared between groups. RESULTS: Of 54,788 patients, 9,967 patients (18.2%) had a high serum calcium level, of whom 1,089 (10.9%) had a diagnosis of HPT. Only 76 (7.0%) patients with HPT underwent parathyroidectomy, 208 (19.1%) underwent knee/hip arthroplasty, and 14 (1.3%) underwent both. Arthroplasty was performed in 1,793 patients without evaluation and/or definitive treatment for HPT. There were higher rates of arthroplasty performed in patients with a high serum calcium level compared with those without (21.2% vs 17.4%, P < .001). CONCLUSION: Patients with high serum calcium levels were more likely to undergo arthroplasty than those with normocalcemia. Hypercalcemia in the setting of hip or knee osteoarthritis should prompt a full evaluation for primary HPT.