CPT code 21146 covers LeFort I midface osteotomy with microsurgical reconstruction and bone grafting to advance and reposition the maxilla for correction of congenital or acquired facial deformities. This code captures complex craniofacial reconstructive work that has implications for surgical planning, facility resource use, and national payment policy due to its operative complexity and potential need for inpatient care. Key payers in national analyses include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will gain a concise overview of the clinical context for the procedure, typical sites of service, and which major payers underwrite care. The publication summarizes common billing considerations, expected service lines, and benchmarking themes relevant to payers and provider organizations. It also outlines areas where policy changes or coverage edits could affect authorization, utilization management, and reimbursement pathways. Data not available in the input is explicitly noted where applicable; the focus remains on clinical and billing characterization for a national audience rather than state-level program specifics.