Beyond Spine and Hip - The Clinical Importance of the Forearm Site (33% Radius) in Osteoporosis Diagnosis

Osteoporosis is a major public health problem characterized by reduced bone mass and microarchitectural deterioration, leading to increased fracture risk. Current diagnostic strategies rely primarily on bone mineral density (BMD) measurements at the lumbar spine and proximal femur using dual-energy X-ray absorptiometry (DXA) which may not fully capture skeletal involvement. To evaluate the diagnostic and clinical value of incorporating the 33%radius (forearm) site into osteoporosis diagnosis and its impact on diagnostic accuracy and fracture risk assessment. A narrative review of classical and contemporary literature was conducted, focusing on skeletal site discordance, diagnostic accuracy, and the role of forearm DXA in specific clinical conditions. BMD varies significantly across skeletal sites, and reliance solely on spine and hip measurements may lead to underdiagnosis. The inclusion of the 33% radius improves diagnostic sensitivity, particularly in conditions affecting cortical bone. Site discordance is frequent, and the number of osteoporotic sites correlates with fracture risk. Clinical conditions such as hyperparathyroidism, chronic kidney disease, and glucocorticoid induced osteoporosis preferentially affect cortical bone and are more accurately detected at the forearm. Studies indicate that adding forearm assessment can identify approximately 9% to 24.4% additional cases that would otherwise remain undiagnosed. Incorporating the 33% radius into DXA assessment enhances diagnostic accuracy, reduces misclassification, and improves identification of patients at high fracture risk. Forearm DXA should be considered a complementary component of comprehensive skeletal evaluation, particularly in selected clinical scenarios.