The Basic And Clinical Research Of Costochondral Graft For Temporomandibular Joint Reconstuction

Purpose:To develop the observation indexes and measurement method of costal cartilage and costa;to assess characteristics of 154 cases costal cartilage and costa calcification using Dual-Energy computed tomography（DECT）;to introduce the application of computer-assisted surgical simulation（CASS）and DECT for temporomandibular joint（TMJ）reconstruction with costochondral graft（CCG）.Methods:154 patients who underwent chest DECT scanning were included in our study.The sixth,seventh and eighth costal cartilages and costas were evaluated by using GSI Viewer-MD Analysis software.CT value,calcium and water concentrations were measured in costal cartilage,cortical or cancellous bone respectively.Consecutive patients who underwent TMJ reconstruction with CCG from November 2013 to March 2015 were included in this study.Before surgery,the cranial-maxillofacial and chest computed tomography（CT）scans were preformed and imported into the Mimics software for virtual positioning and osteotomy planning to guide the selection and placement of the rib and bone trimming of the condyle and ramus.Clinical and radiographic parameters were used to assess the efficacy of CASS guided CCG.Results:An increasing C pattern of cartilage was displayed in females,while P type preferred in males as age increased.Calcification degree generally changed from 1 to 2 or3 in females.CT value and calcium concentration of cartilage went through a gradual rising course and peaked in their 40-50 years,while those two indices of cancellous bone decreased gradually since their 50 years in females.7 consecutive patients（9 joints）who underwent CCG utilizing CASS were included.In 7 joint reconstructions,the 6^th rib was selected,while the 7^th rib was selected in 2 joints.All the grafted ribs were not trimmed or contoured intraoperatively.Postoperative CT scans indicated that all patients had successful reconstructions of the mandibular condyle with the CCG using CASS.46titanium screws in total were implanted and located behind the inferior alveolar neurovascular bundle.There were 16 titanium screws protruding from the medial surface of ramus,and the mean exposed length was 0.7mm（range,0.2 to 1.3mm）.The merged CT scans indicated that the distal end of the CCG was implanted obliquely and anteriorly compared with the predesigned positions,and the mean deviated degree was 5.4°（range,1.7 to 7.3°）.Conclusions:The findings suggest a gradual calcification of the costal cartilage took place before 40-50 years old and a sharp bone loss of the costa happened after 40-50years old in females.Computer-assisted surgical simulation is an accurate method to select a suitable rib(usually the 6^th and 7^th)matching with the TMJ anatomy and avoid the blindness of Costochondral graft.