Lee A, Christmas KN, Simon P, et al. - Researchers assumed that patient factors (age, gender, hand dominance), disease factors (diagnosis, radiographic severity of contralateral shoulder), and surgical factors (type of arthroplasty) impact timing to contralateral surgery. Researchers performed a retrospective review of 332 patients treated with bilateral anatomic (TSA) or reverse (RSA) shoulder arthroplasty (172 TSA/TSA, 107 RSA/RSA, or 53 TSA/RSA) to classify into groups depending on the interval timing between arthroplasty surgeries: group 1 – 142 (≤ 1 year), group 2 – 62 (1-2 years), and group 3 – 128 (≥ 2 years). This research confirmed the hypothesis distinguishing preoperative variables correlated with different time intervals between arthroplasties. According to the findings, the preoperative factors correlated with the highest likelihood of having contralateral shoulder arthroplasty within one year included: osteoarthritis, radiographic bilateral shoulder disease, and TSA for the first surgery.