With the growth of the elderly population, the number of fractures caused by osteoporosis is expected to increase year by year. The incidence and mortality of OVCF in the elderly are rapidly increasing [9–10]. Therefore, it is particularly important to screen out high-risk groups of OVCF in the elderly and carry out early intervention in time. Existing studies have shown that gender, age, bone mineral density, and bone transformation markers are closely related to the occurrence of OVCF [11–12]. Among them, bone mineral density examination is mainly determined by dual-energy X-ray absorptiometry. The inspection equipment is relatively expensive, the execution operation is relatively complex, and there are shortcomings such as X-ray radiation. It has been reported that the accuracy of using bone mineral density alone to predict osteoporotic fractures remains to be further improved [13]. Bone transformation markers including bone resorption markers and bone formation markers such as N-terminal propeptide of type I procollagen (PINP), C-telopeptide of type I collagen (CTX-I) and osteocalcin have many limitations in clinical application [14], which still cannot be used as diagnostic markers and individualized diagnosis and treatment basis for osteoporotic fractures.
In this study, we retrospectively investigated the serum Ca-P product and its correlation with OVCF. The results showed that the serum calcium, serum phosphorus, corrected serum calcium, Ca-P product and corrected Ca-P product in patients with OVCF were lower than those of the same age group with relatively healthy bone. Serum calcium and phosphorus metabolism has been proved to be an important part of bone metabolism. The main factors that keep blood calcium and phosphorus are 1,25 - dihydroxyvitamin D3 (1,25(OH)2 D3), parathyroid hormone (PTH), and fibroblast growth factor 23 (FGF23) [15–17]. Blood calcium and phosphorus in human body maintain a relative balance and play an important role in the differentiation of osteoblasts and osteoclasts [18]. The concentration of calcium and phosphorus in human blood are closely related. Low calcium level may lead to the increase of parathyroid hormone (PTH), and then promote bone to release calcium ions into the blood, increase renal phosphorus excretion, and maintain serum calcium and phosphorus homeostasis [19–20]. The product of blood calcium and phosphorus is closely related to osteogenesis and osteolysis. When the product of calcium and phosphorus is large, calcium and phosphorus are deposited in bone tissue. When the product of calcium and phosphorus is small, the calcification of bone is inhibited and the osteogenesis is affected.
To the best of our knowledge, Ca-P product has not been used as a predictor of OVCF in previous studies, and our study concluded that Ca-P product can be used as a new and useful predictor of OVCF. We further quantitatively analyzed the best indicators for predicting risk efficacy and obtained that when the Ca-P product of the elderly was less than 29.88 or the corrected Ca-P product was less than 30.50, we should pay close attention to the risk of OVCF and carry out standardized and scientific anti-osteoporosis intervention as soon as possible to reduce the incidence of OVCF and the resulting decline in the quality of life and even death risk of the elderly.
In this study, patients with osteonecrosis of the femoral head and osteoarthritis undergoing knee and hip replacement were randomly selected as the control group. The average age was similar, which potentially reduced the impact of age on bone metabolism and increased the reliability of the results to some extent. However, considering that the sample size of this study was still small, the ratio of male to female was quite different, and the lack of multi-center and large sample data support. At the same time, we failed to compare serum Ca-P product with bone mineral density and bone transformation markers to obtain the predictive value and effectiveness of the indicators for the occurrence of OVCF. In addition, the prediction sensitivity and specificity of Ca-P product and corrected Ca-P product for OVCF in this study were not very high, and the prediction accuracy needed to be improved.