Sixty-four postmenopausal women with osteoporosis undergoing adult spinal deformity surgery were randomized to receive perioperative teriparatide (n=32) or denosumab (n=32). The primary outcome of interest was the incidence of proximal junctional kyphosis (PJK) and proximal junctional failure (PJF) within 12 months after surgery. Secondary outcomes of interest included changes in hip bone mineral density (BMD), Visual Analog Scale (VAS) back pain, EuroQol-5D (EQ-5D), Oswestry Disability Index (ODI), and SRS-22r scores. Teriparatide 20 µg was given daily subcutaneously from 3 months preoperatively to 3 months postoperatively, while denosumab 60 mg was administered subcutaneously at 3 months preoperatively and 3 months postoperatively; thereafter, both groups received bisphosphonates. Outcomes were assessed at baseline and at 3, 6, and 12 months postoperatively. Overall, the results of the study revealed that teriparatide did not significantly reduce PJK but did significantly lower PJF incidence at 1 year (3.4% vs 22.2%, p=0.034, modified intention-to-treat) and produced greater improvements in back pain (VAS) and EQ-5D compared with denosumab, without differences in hip BMD. These findings suggest that short-term perioperative teriparatide may help prevent clinically important junctional failures and improve pain and quality of life in osteoporotic women undergoing adult spinal deformity surgery.