Unilateral Cleft Lip Closure: Development of a New Hybrid Technique

Background and goals: Unilateral cleft lips can be treated by different incision techniques. The currently used Millard-II technique pivots a cleft-sided advancement flap from the cleft side into the rotation flap of the non-cleft side, which mainly serves to lengthen the philtrum. However, the two components are often insufficient to adequately elongate the philtral ridge on the cleft side. The result is a raised lip or a so-called whistle-hole deformity. To compensate for these shortcomings, a triangular flap is currently formed in the area of the white roll to ensure sufficient elongation. However, the scar of the triangular flap runs exactly opposite to the aesthetic unit. Furthermore, it often causes a step formation within the white roll. Knowing the weaknesses of the previous techniques, further development of the incision was made. The rotational flap of the Millard-II technique was expanded by extending the incision into the columella - similar to the well-known Mohler technique. The caudal portion of the advancement flap of the Millard-II technique was extended by a wave incision, as known from the Pfeifer procedure. The aim of this paper is to compare the Millard-II technique with the new hybrid technique and to analyse which of the two techniques lengthens the cleft-sided philtrum ridge more. For this purpose, ex-vivo models were used to investigate which of the methods provides the greatest gain in length of the philtral ridge and thus also the greatest benefit in the treatment of a cleft lip. This work will then form the basis for further studies to be able to apply the new hybrid technique to unilateral cleft lip patients in the future. Methods: To obtain initial results on the new hybrid technique, 31 pig snouts were procured, fitted with a standardised cleft lip, and then operated on. One of the pig snouts was treated with the Tennison-Randall technique as a proof-of-concept, 15 snouts with the Millard-II 3 technique, and another 15 snouts with the new hybrid technique. Special attention was paid to the gain in length of the cleft-sided philtrum ridge. To obtain reproducible results, a template was made in advance so that all clefts were standardised. In order to be able to measure the different distances as accurately as possible, the snouts were scanned with a 3D scanner at previously determined intervals. The Trios 4 intraoral scanner with the Move+ station from the company 3Shape A/S was used for the work. In a subsequent step, the scanned models were evaluated with the Blender programme from the Blender Foundation. Results: The study showed that the new hybrid technique made it possible to lengthen the cleft side philtrum ridge by 7% more than the Millard-II technique after surgery. The average length gain was 6.68 mm with Millard-II and 7.74 mm with the hybrid technique. The post- operative length difference between the cleft side philtrum ridge and the non-cleft side philtrum ridge was also reduced more with the new hybrid technique from 23% (Millard-II) to 10%. The absolute difference, cleft side philtrum to non-cleft side philtrum, was 3.14 mm on average with Millard-II and 1.52 mm with the hybrid technique. Discussion: The study shows that the philtrum ridge on the cleft side can be lengthened significantly more with the new incision technique than with the Millard-II technique. According to the results, the triangular flap in the white roll can be avoided in the future. Since the pig snouts lack some important anatomical features, further investigations should first be carried out on realistic simulation models to obtain even more precise results.