Bone density after reverse shoulder arthroplasty declines over time

Driven by the potential advantages in bone stock preservation and easier implant removal during revision surgery, the use of cementless short-stem implants in shoulder arthroplasty has increased in recent years. Despite this, joint replacement procedures outside of the shoulder have reported postoperative bone loss in studies using the dual-energy X-ray absorptiometry (DEXA) technique to measure bone density. In shoulder replacements, DEXA is uncommon, and assessments of bone changes around implants largely rely on qualitative evaluation using plain radiographs. However, this method has limitations and makes it difficult to objectively measure how bone density changes over time.

To improve postoperative assessments, a research group led by Dr. Katsumasa Nakazawa and Professor Hidetomi Terai at Osaka Metropolitan University's Graduate School of Medicine used DEXA to compare patients who underwent anatomical total shoulder arthroplasty (aTSA) and reverse shoulder arthroplasty (RSA). The retrospective study examined changes in bone mineral density (BMD) around the humeral implant during the first two years after surgery and investigated their relationship with osteoporosis and clinical outcomes. After dividing the upper humeral area into five zones, the BMD of 94 RSAs and 43 aTSAs were analyzed.

The results revealed distinct patterns of bone density change between the two procedures. In patients who underwent RSA, significant decreases in BMD over time were observed in certain regions around the implant stem. In contrast, patients who underwent aTSA showed decreased BMD during the period from three weeks to six months after surgery in areas below the humeral head, but with little further decline thereafter. Furthermore, in the RSA group, bone loss in the humeral mid-shaft region was significantly associated with osteoporosis. Both bone loss and osteoporosis also associated with a lower likelihood of achieving a clinically meaningful improvement in shoulder function after surgery.

Our study showed that bone density around the implant after RSA declines over time, particularly in patients with osteoporosis/ These findings suggest that assessing osteoporosis before surgery, monitoring bone density after surgery, and optimizing osteoporosis treatment may play important roles in improving long-term outcomes after RSA."

Dr. Katsumasa Nakazawa, Osaka Metropolitan University's Graduate School of Medicine 

Furthermore, these results may enhance preoperative evaluation and postoperative care for elderly patients undergoing shoulder arthroplasty, particularly those with osteoporosis undergoing RSA, and contribute to safer treatment strategies and more stable long-term outcomes.

The findings were published in The Bone & Joint Journal.