3-Dimension Anatomy And Biomechanical Simulation Related To Functional Cleft Lip Repair

BackgroundAbout normal orbicularis oris muscle gross and elaborate anatomy, many studies have been reported. The role orbicularis oris muscle plays in normal lip and nose shaping is quite clear. However, due to the lack of objectives and other difficulties in observation, study of the anatomical structures of orbicularis oris muscle in cleft lip and other associated muscles surrounding remains a controversy.Functional repair of cleft lip is closely related to anatomy of the nasal-labial muscles. To achieve functional repair effects, we need not only to know about nasal-labial muscle anatomy in cleft lip, but also to understand the action mode of the muscles, and re-establish the equilibrium of muscle biomechanics during surgery. The most common surgical treatment for nasal-labial muscles are mostly too simple. There are many postoperative results can be improved via functional repair with proper muscle reconstruction.PurposeUse Micro-CT scanning on two iodine stained lip and nose specimens of 4 fetal cleft lip (2 bilateral complete cleft lip fetus and 2 with unilateral complete cleft lip). Then convert the tomographic images to DICOM format and export to 3D softwares to reconstruct a 3-D model of cleft lip nasal-labial muscles.Based on the 3-D model constructed in the previous step, and refer to data from previous studies, use computer-aided design softwares to build a skin-muscle- cartilage finite element model. Load the model in computer-aided engineering softwares to simulate the effect of muscle driven transformation of the nose and lip. Thus to verify the trend of cleft lip deformity development.With the same technology, establish corresponding postoperative models of unilateral cleft lip and bilateral complete cleft lip with intraoperatively reconstructed muscle tension system. Load the models, observe the changes driven by muscle tension force. Compare the results of methods that directly connect orbicularis oris muscle to the 3-dimensional nasal-labial muscle reconstruction and analyze the differences between the two methods.Reviewe 31 past cases of bilateral cleft lip repair based on the 3-dimensional nasal-labial muscle reconstruction technique. Evaluate their postoperative and follow-up results to prove the value of the technique in bilateral cleft lip functional repair.Materials and Methods(1) fetal cleft lip nasal-labial muscles’3D model reconstruction:Cut the lip and nose from 4 cases of aborted fetus with cleft lip. Fix the specimens’tissue with 4% formaldehyde. Then soak them in 3.75% iodine potassium iodide for 7 days to stain the specimens. Scan the specimens with Micro-CT scanner. Observe the scanned images for muscle fibers. Convert the resulting 2-dimensional tomographic images into a common format, DICOM. Import to Mimics for editing. Rendering the muscle fibers, and reconstruct the three-dimensional model of cleft lip labial-nasal muscle anatomical structure.(2) cleft lip nasal-labial finite element biomechanical model establishment:Refer to the former 3-dimensional model reconstructed from Micro-CT scanning result, combined with relevant research data, establish the cleft lip nasal-labial finite element model in Catia. After building the skin-muscle-cartilage model, simplify it to some extent. Import the model into Hypermesh for meshing. Define soft tissue as C3D4H tetrahedral units, muscle fibers as B31H beam units. Import the subdivided models to Abaqus for loading and further analysis.(3) finite element biomechanical simulation of cleft lip repair:With the clinical data and previous literature as references, along with the Micro-CT result as a basis for anatomy, stimulate different methods of cleft lip repair in finite element system. Respectively create the finite element biomechanical model of methods that directly connect the orbicularis oris muscle and the 3-dimensional nasal-labial muscle reconstruction in unilateral and bilateral cleft lip repair. Load the models, observe changes generated by the muscles disposed with those two methods. Compare the differences to evaluate the effects of reconstructed muscle in different surgical methods and the ability to maintain the effects. Select typical patients who have taken the two kinds of surgeries. Ask them to take 3-dimensional facial laser scanning in the relaxed state and pouting pose. Calculate the deviations between them within Geomagic Wrap. Generate fringes, which finite element model load results were compared to verify simulation credibility of the results.④ Apply the 3-dimensional nasal-labial muscle reconstruction technique to bilateral cleft lip repair. Observe and make statistics of 31 cases of bilateral cleft lip between Jan 2010 to Dec 2014. Ask two non-inteam surgeons to evaluate the postoperative and follow-up effects with 3-points visual analysis scale.Results(1) Micro-CT scan and 3-dimensional model reconstruction:① Unilateral complete cleft lip observations:on the healthy side of the upper lip there are still four parts of the orbicularis oris muscle visible (pars marginalis, pars peripheralis, muscle fibers of levator labii superioris and nasal muscle complex). But at the cleft edge, orbicularis oris muscle fibers and nasal muscle were deformed and displaced. Particularly severe maldevelopment and disorder of muscle fibers can be observed on the cleft side.② bilateral complete cleft lip observations:no significant muscle fibers can be observed in the prolabium. In both of the lateral outside can find hypoplasia, disorganized, and directionless muscle fibers. The boundaries between orbicularis oris muscle, levator labii superior and nasal muscle is not very clear.(2) Cleft lip FEM biomechanical analysis:① unilateral complete cleft lip FEA simulation results:lip peaks are uplifted. The cleft widened. Nostrils of the affected side widened, the nasal alar collapsed more with the alar feet outreached. Columella tilted to the affected side, while philtrum shifts to the contralateral.② bilateral complete cleft lip FEA simulation results:both sides of the outside upper lip expanded more. Lip peaks are uplifted. Both sides of the nasal alar collapsed more with the alar feet outreached, the nasal apex lowers.(3) finite element simulation of cleft lip repair:compare surgical methods that directly connect the orbicularis muscle to 3-dimensional nasal-labial muscle reconstruction.① unilateral cleft lip:directly connected orbicularis muscle can shrink the upper lip to the middle, but smaller impact on narrowing the nose. Philtrum morphology does not change significantly. No significant nasal floor elevation. Nasal alar collapse and alar feet outreach has not been significantly corrected. The 3-dimensional muscular reconstructed model has a more obvious contraction. The nose narrowed more.3-dimensional shape of the philtrum is quite enhanced along with the nasal floor elevation, narrowing of the nasal alar and collapse of the alar feet.② bilateral cleft lip:the simulation results basically are similar to unilateral cleft lip. Directly connected orbicularis muscle has very limited contribution to shaping aesthetic subunits. While 3-dimensionally reconstructed has a significant improvement in nose narrowing, philtrum shape enhancement, nasal floor elevation.③ Compare the simulation results to 3-dimensional laser scan face model. The changes of face when the patients were asked to pout consistent with the finite element simulation.(3) Clinical practice of bilateral cleft lip functional repair:31 cases of bilateral cleft patients received functional repair,22 of them followed up 6 months to 1 year after the operations. The results are satisfactory from the 3-points VAS evaluation.ConclusionCleft lip deformity in the trend of growth and development, is related to the impact of muscle tension. In the role of abnormal muscle interference, the cleft with the nostrils widened, nasal alar collapse, alar feet adducted, midline deviated, lip peaks uplifted and other deformities will increase further. This is the result of long-term imbalance in muscle strength. So that to achieve functional cleft lip repair, we must restore normal muscle biomechanical equilibrium as far as possible. But only by directly connect the orbicularis muscle obviously can not do this. We need to split orbicularis muscle flap into different branches according to the normal anatomy of the muscle structure. And in accordance with normal muscle tension structure, re-build the muscles’cross-cutting, overlap, and other three-dimensional relative antagonistic relationship. That is the 3-dimensional nasal-labial muscle reconstruction.The main innovations:① scan unilateral complete cleft lip and bilateral complete cleft lip fetal lip and nose specimens with Micro-CT and reconstruct 3-dimensional models of muscle anatomy of cleft lip. Replenish the field of cleft lip anatomy research.② apply finite element analysis technology from computer-aided engineering to cleft lip biomechanical study. Build finite element biomechanical models of unilateral and bilateral complete cleft lip. By means of computer-aided technology to conduct a visual display and data analysis of cleft lip deformity and muscle tension. Confirm relevance of cleft lip deformity and abnormal muscle biomechanical imbalance.③ set up a system of finite element biomechanical simulation of cleft lip repair. highlighting the importance of rebuilding muscle mechanical equilibrium in cleft lip functional repair. It provides some reference techniques for orthopedic surgery to analyze causes of deformity, design clinical techniques and other aspects of clinical surgical procedures.