A Longitudinal Cohort Investigation of the Development of Symptomatic Adjacent Level Compression Fractures Following Balloon-assisted Kyphoplasty in a Series of 726 Patients.

Background Balloon-assisted kyphoplasty (BAK) is a well-accepted treatment for symptomatic vertebral compression fractures (VCF) secondary to osteoporosis. Some have raised a concern of an increased incidence of adjacent fractures due to alterations in spine biomechanics after cement augmentation. The incidence of subsequent VCFs following BAK is poorly understood. The aim of this study was to investigate the timing, location, and incidence of new VCFs following BAK and to identify risk factors associated specifically with the occurrence of new adjacent level fractures. Objectives The study was performed to determine the incidence of symptomatic subsequent adjacent and remote level compression fractures in a cohort of patients undergoing BAK. Study design Longitudinal cohort investigation at an academic medical center and a central referral center for VCFs. Setting A consecutive single surgeon series of 726 patients with osteoporotic compression fractures. Methods A prospectively collected cohort of 726 patients who underwent BAK between 2001 and 2014 for osteoporotic VCFs was evaluated. Seventy-seven patients were identified who underwent a second BAK for a new compression fracture and were include in the present series. The indication for BAK treatment was pain unresponsive to non-surgical management for all cases. Variables were recorded for each patient, including the time between index and subsequent fracture, fracture level, and number of initial fractures as well as with tobacco use, body mass index (BMI), and chronic steroid use. Results Seventy-seven of 726 patients (10.6%) underwent a second BAK procedure on average 350 days following the initial procedure (range 21 to 2,691 days). Third and fourth procedures were less common, treated in 11 and 3 patients, respectively. Forty-eight of 77 patients (62%) suffered a fracture at a level immediately adjacent to the index level at mean time of 256 days. Remote level fractures were treated at a mean time of 489 days, but no statistical difference was noted. There was no statistically significant difference between tobacco use, BMI, and chronic steroid use between patients suffering from remote and adjacent level VCFs. Limitations This was not a population based study, and the true incidence of subsequent fractures after BAK might be underestimated by this analysis. Conclusions Symptomatic compression fractures after BAK are relatively uncommon and may occur long after the initial kyphoplasty procedure. Only half of subsequent fractures occur immediately adjacent to the initially treated level; the others occur remotely. Patients with a single symptomatic thoracic or lumbar fracture suffered from remote and adjacent level fractures equally. In contrast, all patients who suffered both a thoracic and lumbar fracture at the same time had a second fracture at an adjacent level. Specific risk factors for remote versus adjacent level fractures could not be determined. Key words: Balloon kyphoplasty, cement augmentation, osteoporosis, vertebral compression fracture, adjacent level fracture, vertebroplasty.