82 Chapter 6 ABSTRACT Introduction: Implant loss following breast reconstruction is a devastating complication which should be prevented as much as possible. This study aimed to validate a previously developed multicenter risk model for implant loss after implant-based breast reconstructions, using national data from the Dutch Breast Implant Registry. Methods: The validation cohort consisted of patients who underwent a mastectomy followed by either a direct-to-implant or two-stage breast reconstruction between September 2017 and January 2021 registered in the Dutch Breast Implant Registry. Reconstructions with an autologous adjunctive and patients with missing data on the risk factors extracted from the multicenter risk model (obesity, smoking, nipple preserving procedure, direct-to-implant reconstruction) were excluded. The primary outcome was implant loss. The predicted probability of implant loss was calculated using beta regression coefficients extracted from the multicenter risk model and compared to the observed probability. Results: The validation cohort consisted of 3769 reconstructions and implant loss occurred after 307 reconstructions (8.1%). Although the observed implant loss rate increased when the risk factors accumulated, the predicted and observed probabilities of implant loss did not match. Of the four risk factors in the multicenter risk model, only obesity and smoking were significantly associated to implant loss. Conclusion: The multicenter risk model could not be validated using nationwide data of the Dutch Breast Implant Registry and is therefore not accurate in Dutch practice. In the future, the risk model should be improved by including other factors to provide a validated tool for the preoperative risk assessment of implant loss.
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