The risk factors of vertebral refracture after kyphoplasty in patients with osteoporotic vertebral compression fractures: a study protocol for a prospective cohort study

Background: Percutaneous kyphoplasty (PKP) is the first-line treatment for osteoporotic vertebral compression fractures (OVCFs) that can immediately relieve pain and allow the quick recovery of lost mobility. However, some studies reported that after PKP, the incidence of vertebral refracture, particularly adjacent vertebral fracture (AVF), was high. Our previous meta-analysis suggested that the risks for vertebral refracture and AVF did not increase after percutaneous vertebral augmentation in OVCF patients. Despite the negative results of our meta-analysis, there is still significant evidence regarding the relationship between kyphoplasty and AVF, so a new prospective cohort study is warranted. In addition, in our previous retrospective study, we found that advanced age, female sex and low oestradiol (E-2) concentrations might be related to the occurrence of postoperative vertebral refracture after PKP. To sufficiently evaluate the probable factors involved in the occurrence of postoperative vertebral refracture, we designed this prospective study. Methods: This is a prospective cohort study of patients admitted for PKP to treat painful OVCFs. The baseline data, including demographic information, lifestyle, bone metabolic status, sex hormone and sex hormone-binding globulin (SHBG) levels, and clinical characteristics will be collected at the time of enrolment. Surgical features of PKP will be recorded on the operation day. Lifestyle, bone metabolic status, sex hormone levels, and SHBG levels will be assessed during the follow-up period at 1 m, 3 m, 12 m, and 24 m postoperatively. Patients suffering from acutely aggravated back pain will be referred to an orthopaedist, and refractured vertebrae will be confirmed by magnetic resonance imaging and computed tomography. The primary outcome will be the incidence of vertebral refracture. Multivariate analyses will be carried out to evaluate the variables that are independently correlated with vertebral refracture. Discussion: To evaluate the risk of postoperative refracture preoperatively and to identify the surgical points related to postoperative refracture, this study will explore the risk factors related to vertebral refracture after PKP. The results may provide new information about defining OVCF patients suitable for PKP treatment.