Background: Implant malposition is one of the most common causes for revision after prosthetic breast reconstruction. There is a paucity of research on the incidence, etiology and risk factors for implant malposition in this setting. Methods: Retrospective review of a single surgeon's prosthetic breast reconstructions was performed. Variables collected included age, BMI, radiation, chemotherapy, implant characteristics and malposition location (inferior or lateral). Binary logistic regression identified risk factors for malposition. Chi-square test assessed malposition rate as a function of implant volume to BMI subgroups. Results: Of 836 breasts, 82 (9.8%) exhibited implant malposition. Risk factors for any malposition were older age (OR 1.05, 95% CI 1.02-1.07), BMI<25 (OR 1.64, 95% CI 1.00-2.70) and bilateral reconstruction (OR 13.41, 95% CI 8.50-21.16). Risk factors for inferior malposition were older age (OR 1.04, 95% CI 1.01-1.06), BMI<25 (OR 3.43, 95% CI 1.88-6.26) and bilateral reconstructions (OR 11.50, 95% CI 6.79-19.49), while risk factors for lateral malposition were only older age (OR 1.05, 95% CI 1.02-1.08) and bilateral reconstructions (OR 7.08, 95% CI 4.09-12.26). Post-mastectomy radiation was protective against lateral malposition (OR 0.30, 95% CI 0.10-0.88). Stratification by implant volume and BMI demonstrated patient subgroups with distinct patterns of malposition (incidence 0.0% versus 10.9%, P = 0.001). Conclusions: This is the first study to identify risk factors for implant malposition after prosthetic breast reconstruction. Different risk factors contributed to malposition in different directions. The effect of implant size on malposition was mediated through BMI, highlighting the interplay of implant and patient characteristics with respect to malposition.
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