Incidence of serious adverse events associated with readmissions after vertebral augmentation using an expandable implant: Follow-up analysis of KAST

BACKGROUND CONTEXT: Vertebral compression fractures (VCFs) are costly, with expenditures exceeding a billion dollars annually in the United States. The effectiveness of different vertebral compression fracture treatment approaches for preventing re-admissions associated with VCFs or other related conditions is important to assess. PURPOSE: To compare incidence of serious adverse events (SAEs) associated with re-admissions in patients randomly assigned to one of two vertebral augmentation approaches. METHODS: KAST (Kiva Safety and Effectiveness Trial) was a pivotal, multicenter, randomized, controlled investigational device exempt (IDE) trial performed to compare an expandable implant-based vertebral augmentation approach (Kiva System, Benvenue Medical, Santa Clara, CA) to balloon kyphoplasty (BK; Medtronic, Inc., Minneapolis, MN). KAST included 21 sites in North America and Europe and enrolled adults with painful VCFs due to primary or secondary osteoporosis in the thoracic and/or lumbar spine. Patients were randomly assigned to the expandable implant (n=144) or BK (n=141). Protocol-specified serious adverse events (SAEs) were catego- rized using the standardized terminology from the Medical Dictionary for Regulatory Activities. The proportion of patients experiencing SAEs associated with re-admission was statistically evaluated. The number of SAEs associated with re-admissions was tabulated for each patient. The incidence of total number and specific types of SAEs were calculated for each treatment group using a per-person-month metric and statistically compared. RESULTS: Forty (27.8%) expandable implant patients had 67 SAEs associated with re-admission compared to 44 (31.2%) BK patients having 102 SAEs. Significantly fewer expandable implant patients had re-admissions associated with cardiovascular disorders (4 or 2.8% versus 12 or 8.5%, p=.041). The expandable implant patients had significantly fewer total re-admissions during the one-year after the KAST index procedure (p<.01). In order to control for history of previous VCF(s), SAEs associated with re-admissions for VCF were tabulated for patients after stratifying them by whether or not history of VCF was reported at the KAST study baseline visit. The expandable implant patients demonstrated a significant tendency for avoiding VCFrelated SAE re-admissions (p=.048). CONCLUSIONS: The lower rate of repeated re-admissions seen with vertebral augmentation using the expandable implant are salient to patients and to health care organizations.