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Underdiagnosis Of Hyperparathyroidism In Patients With Osteoarthritis Undergoing Arthroplasty
*Sarah Y. Park, *Oliver Scotting, Tina W. F. Yen, Douglas B. Evans, Tracy S. Wang, Sophie Dream
Medical College of Wisconsin, Wauwatosa, WI

Objective: Hyperparathyroidism (HPT) is commonly underdiagnosed and undertreated. Joint pain is a nonspecific symptom which can be associated with osteoarthritis or HPT. We hypothesize that patients treated for osteoarthritis are underdiagnosed with HPT.
Methods: Adult patients diagnosed with hip or knee osteoarthritis (ICD-9/10 M16, M17) from 01/2000 to 10/2020 were queried from our hospital system database for hyperparathyroidism (ICD-9/10 code E21), parathyroidectomy (CPT codes 60500, 60502), and/or arthroplasty (CPT codes 27441, 27447, 27443, 27446, 27437, 27442, 27438, 27440, 27130). We included patients with at least one serum calcium level drawn within 1 year before or after diagnosis of osteoarthritis and excluded patients who had undergone prior parathyroidectomy (PTX). Patients with a high serum calcium level (normal 8.6-10.2 mg/dL) were divided into two groups: those with and without ICD diagnosis of hyperparathyroidism (HPT). The latter group was further subdivided into 3 groups: “likely HPT,” “unlikely HPT” (PTH <30 mg/dL), and “incomplete workup” (no PTH available). “Likely HPT” was defined as a high PTH (normal 15-70 pg/mL) or inappropriately high PTH (30-70 mg/dL). Arthroplasty rates were compared between all study groups using Chi-square tests.
Results: Of 54,707 patients, 9924 patients (18.1%) had an above-normal serum calcium level, of whom 1088 (11.0%) had a confirmed diagnosis of HPT. Only 76 (7.0%) patients with HPT underwent PTX, 208 (19.1%) underwent knee/hip arthroplasty, and 14 (1.3%) underwent both. The remaining 8836 patients included those categorized as having an “incomplete workup” (5934, 67.2%), “likely HPT” (2354, 26.6%), and “unlikely HPT” (548, 6.2%). Arthroplasty was performed in 1790 patients (497 “likely HPT” and 1293 “incomplete workup”) without evaluation and/or definitive treatment for HPT. There were higher rates of arthroplasty performed in patients with a high serum calcium level compared to those with normocalcemia (21.2% vs 17.4%, p<0.001). (Figure 1)
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 HPT.



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