CPT code 21145 denotes LeFort I midface reconstruction with maxillary advancement using microsurgery and bone grafting to correct congenital or acquired deformities. This major craniofacial procedure is clinically important for restoring facial form, dental occlusion, and airway function, and it carries implications for surgical planning, facility resources, and payer coverage decisions across the United States. Key payers addressed in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise explanation of the procedure and service setting, an overview of payer coverage patterns and common modifiers, and contextual clinical considerations relevant to authorization and claims submission. The publication highlights benchmarks for site-of-service utilization, typical reimbursement considerations, and policy updates that influence coverage and coding practice. It also outlines issues commonly encountered on claims for complex craniofacial reconstructive surgery, including bundling, documentation expectations, and the role of multidisciplinary teams. Data not available in the input is noted where applicable; the content focuses on national-level clinical and billing context rather than state-specific rules.