ObjectiveTo investigate the effectiveness of the mortise-tenon orbicularis oris muscle flap for philtrum column deformity secondary to the unilateral cleft lip repair. MethodsBetween January 2009 and August 2011, 43 patients with philtrum column deformity secondary to unilateral cleft lip repair were treated. There were 23 males and 20 females with an average age of 23.6 years (range, 18-31 years). The left philtrum column was involved in 26 cases, and the right side in 17 cases. Cleft lip was repaired with Millard I in 15 cases and with Millard II in 28 cases. The time between cleft lip repair and philtrum column deformity correction was 15-30 years (mean, 21.7 years). The bilateral double orbicularis oris muscle flap was obtained, and then was divided horizontally into two layers. The overlapping suture of the bilateral lower muscle flap was perfomed, and the upper layer muscle was designed into the mortise-tenon orbicularis oris muscle flap and was sutured with contralateral skin. ResultsAll incisions healed by first intention. Forty cases were followed up 13.4 months on average (range, 6-34 months). The patients achieved satisfactory effects in bilateral symmetry philtrum column and normal concave shape. At 6 months after operation, significant improvement was observed in 38 cases and no obvious improvement in 2 cases. ConclusionThe mortise-tenon orbicularis oris muscle flap is a simple operation and can obtain good results in the appearance and function of the upper lip in the correction of philtrum column deformities secondary to the unilateral cleft lip repair.