Eccentric jaw deformity, also known as asymmetrical mandibular protrusion or unilateral mandibular hypoplasia, is mainly caused by overdevelopment of the condylar neck on one side, manifested by asymmetry of the lower 1/3 of the face, chin point deviation to the healthy side, anterior teeth anticlinal, midline deviation, the affected side of the posterior teeth are often submedial relationship, the healthy side of the posterior teeth are often anticlinal. Due to the asymmetric development of the jaws, the position and direction of the muscles attached to the jaws are also shifted and changed, and the dynamic balance of the perioral muscles is out of balance, resulting in orofacial deformity. Through orthognathic surgery, combined with preoperative and postoperative orthodontic treatment, we corrected the jaw deformity and reestablished the dynamic balance of perioral expression muscles, and all patients achieved satisfactory results. 1. Clinical data Patients with clinically diagnosed deviated jaw deformity, excluding benign mandibular condylar hypertrophy, tumor, trauma, first and second gill arch syndrome, hemimandibular hypertrophy and other craniofacial syndromes, were admitted between December 2004 and December 2006. 24 patients, aged 18-33 years, average age 23 years, 10 males and 14 females, were treated. All patients showed facial asymmetry, with the chin joint located on the sagittal side of the face, and the upper and lower central incisors were not aligned in the midline, including 18 cases of left mandibular deviation and 6 cases of right deviation, with the mandibular midline deviating 3 to 15 mm to the healthy side, averaging 6 mm. All patients had varying degrees of deep coverage or open dentition of the affected posterior teeth, and the healthy posterior and anterior teeth were anticlinal or antagonistic dentition. 10 patients were accompanied by synergistic overgrowth of the maxilla, resulting in a reduction of the affected dentition plane. Eight patients had pain or popping symptoms in the temporomandibular joint. Among the 24 patients, 6 cases (25%) were first consulted for the purpose of correcting facial shape; 14 cases (58.3%) were for the purpose of improving tooth and jaw relationship and restoring occlusal function; 4 cases (16.7%) required both correction of facial shape and restoration of function. 2, Treatment methods 2.1 Preoperative preparation All patients had preoperative cephalometric frontal and lateral radiographs, curved tomography, and temporomandibular joint Xue’s radiographs. The cephalometric analysis was performed mainly by positioning cephalometric ortho-lateral radiographs. The orthodontic and orthognathic departments jointly consulted to determine the treatment plan. 19 patients underwent preoperative orthodontic treatment to align the teeth to remove compensatory tilt and coordinate the arch morphology and width irregularities. After the completion of orthodontics, model surgery simulation design and again cephalometric analysis and effect prediction (VTO) were performed. The non-anatomical jaw frame was used for the model surgery operation and the positioning jaw plate was made for the single jaw surgery, and the patients with double jaw surgery used the face arch transfer jaw relationship and the anatomical jaw frame to complete the model surgery and make the jaw plate. 2.2 Surgical method According to the degree of deformity, labiodental relationship and inclination of the dental plane, Le Fort I osteotomy and mandibular ascending sagittal osteotomy or vertical osteotomy were used, and some patients were assisted with horizontal osteotomy chinplasty or chin trimming. Intraoperatively, the broken ends of the bone were fixed internally with titanium nail plates. Intermaxillary traction was performed 48h after surgery and maintained for 3-4 weeks. After removing the intermaxillary traction, orthodontic treatment was performed again to finely adjust the occlusal relationship. 2.3 Effect evaluation 2.3.1 Clinical observation and measurement All patients were photographed before treatment and 3-6 months after treatment in frontal, lateral, oblique and elevation positions for comparative observation. The oral and lip measurements were performed using special anthropometric tools (triangular parallel gauges and two-foot gauges), with the subject seated, lips naturally closed and eyes level, and then direct measurements were performed. Referring to Shao Xiangqing’s Anthropometric Manual [1] and Farkas’ Anthropometry of the head and face, we customize some of the measurement points. Fixed points: subnasal point (sn) the apex of the angle formed by the lower edge of the nasal tubercle and the skin part of the upper lip; external canthus point (ex) the point where the upper and lower eyelid margins meet at the external canthus; internal canthus point (en) the point where the upper and lower eyelid margins meet at the internal canthus; nasal wing point (al) the outermost point of the nasal wing; oral cleft point (sto) the point where the red edge of the upper lip intersects with the median sagittal plane; labial arch high point (cph) the highest point of the upper labial arch, i.e., the labial peak point; Lip arch low point (ls) the lowest point between the two labial peaks of the upper lip arch, i.e., the human midpoint; corner point (ch) the outer corner of both sides of the oral fissure, the point where the upper and lower lip migrations meet at both ends. 2.3.2 Statistical analysis For statistical convenience, the measurements between the symmetry points were converted to variables, and the variable of the symmetry marker point was the difference between the affected side (the long side of the condylar neck) and the measurement of the healthy side, expressed as Dif. A positive value of the difference between the two indicates that the distance on the affected side is greater than that on the healthy side, and a negative value indicates that the distance on the affected side is less than that on the healthy side. A larger difference indicates a significant offset, while a smaller difference indicates a closer symmetry.