Re-fractures of non fracture vertebral body after percutaneous kyphoplasty

Objective To investigate the causes of re-fractures of non fracture vertebral body after percutaneous kyphoplasty (PKP). Methods 512 patients (618 vertebral bodies) treated with PKP because of osteoporosis VCFs were recruited from June 2010 to June 2014. There were 107 males (121 vertebral bodies) and 405 females (497 vertebral bodies) with the mean age of 70.38±7.59 years old (51 to 91 years). There were 406 single segment fracture and 106 double segment fractures cases, and the fracture segments were T4 to L5. The T value of the patients' bone mineral density (BMD) was from -1.0 to -5.2 SD. The clinic characteristics of all the patients including age, sex, body weight, body height, body mass index (BMI), BMD score of the spine, volume of bone cement, restoration rate of anterior/middle vertebral height, postoperative complications (pulmonary embolism, bone cement leakage, nerve injury), and treated vertebral level were analyzed. Results 52 patients (10.16%, 52/512) experienced refractures of non fracture vertebral body after kyphoplasty, and 4 experienced re-fracture of the fracture vertebral body after kyphoplasty. The average age of the 52 patients was 71.88±7.74 years old, meanwhile, the ratio of female was 94.23% (49/52), the mean T value of BMD -4.03±0.60 SD, the ratio of initial double segment fractures 51.92% (27/52). In addition, among the 456 cases with no fracture, the average age was 70.21±7.56 years, the ratio of female was 77.19% (352/456); the mean T value of BMD was -2.89±0.55 SD; the ratio of initial double segment fractures was 17.32% (79/456). The data above (age, T value of BMD and initial double segment fractures) were all with statistical significant differences. Whereas the BMI, volume of bone cement, intervertebral disc leakage and restoration rate of anterior/middle vertebral height had no significant difference between the two groups. Furthermore, in the refracture of non fracture vertebral body group, 32 cases (61.54%, 32/52) were nonadjacent fractures, and 20 (38.46%, 20/52) were adjacent fractures. Conclusion Osteoporosis degree, female and initial double segment fractures were major risk factors in the development of re-fracture of non fracture vertebral body after PKP. Key words: Kyphoplasty; Osteoporotic fractures; Bone density