| PART I Rib Cartilage Assessment with Low-Dose MSCT in Young Children with Microtia Requiring Ear ReconstructionABSTRACTBackground and Objective:The assessment method for auricular reconstruction is controversial. Rib cartilage growth is closely related to age, and determines the feasibility and outcomes of auricular reconstruction. A prospective study would involve elective radiation that is not otherwise clinically indicated. Direct definitive data such as preoperative rib cartilage growth is required. The aim of this study was to evaluate a method for rib cartilage assessment with low radiation dose.Materials and Methods:A total of 60 children with microtia who underwent auricle and hearing reconstructions from January 2011 to May 2013 were included.Forty-three children with microtia aged 5～7 years were examined by low-dose multi-slice CT with coronary scan technique, and 17 children aged 6～8 years were randomly examined with routine axial scan as controls. Low-dose chest MSCT was performed in coronary scan mode with a special support using GE Light Speed VCT 64. Scanning parameters were as follows:scanning layer thickness= 5 mm; rotation time= 0.4s; voltage= 100 kVp; current=145 mA; scan length was 50±12.2 mm in coronary scan mode and 250±25.2 mm in axial scan mode. The dose-length product (DLP) and the volume CT dose index (CDTIvol) were recorded from the scan protocol of each CT examination. The CDTIvol was 2.16 HU. Cartilage and rib images were reconstructed with maximum intensity projection and volume rendering technique. The fifth to ninth rib cartilages were chosen as the observation plane. Differences in the reconstructed image quality were randomly evaluated by two experienced radiologists with double-blind method.Differences in image quality and radiation dose of the two groups were compared.Results:The coronal scanning group had 42 images (97.7%) of above good (good and excellent) quality and one (2.3%) of poor quality. The routine axial scanning group had 15 images (88.2%) of above good quality and two (11.8%) of poor quality. Similar image quality was achieved by coronal scanning as compared to axial scanning (p<0.05). The noise levels in the two groups were similar (p>0.05). DLP was 19.4±3.3 mGy*cm in the coronal scanning group and 68.0±12.4 mGy*cm in the axial scanning group. Radiation dose of the coronal scanning group was significantly lower than the axial scanning group (p<0.001).Conclusion:The coronal scanning technique was a better choice for assessment of rib growth in young microtia children requiring ear reconstruction.PART II Rib Cartilage Assessment Relative to the Healthy Ear in Young Children with Microtia Guiding operative timingABSTRACTBackground and Objective:The optimal age for auricular reconstruction is controversial. Rib cartilage growth is closely related to age, and determines the feasibility and outcomes of auricular reconstruction. The aim of this study is to develope a predictable method to guide the timing of auricular reconstruction in children with microtia.Methods:Rib cartilage and the healthy ear were assessed using low-dose multi-slice CT. The sixth, seventh, and eighth rib cartilages were reconstructed to match the healthy ear cartilage framework and measured using ADW4.2 (GE Medical Systems, USA). The length of the eighth rib was measured bilaterally from the bone-cartilaginous junction to the sternal attachment and the width of the bilateral cartilaginous synchondrosis of the sixth and seventh rib cartilage was measured. Additionally, the length of the helix of the healthy ear was measured from the helical crus to its junction with the earlobe. If the length of the eighth rib cartilage on the contralateral side of microtia was approximately equal to the length of the helix of the healthy ear, and the auricular length of the patient was approximately equal to auricular length of their parents, the surgeon decided to operate. If the length of the eighth rib cartilage on the contralateral side was approximately 2.5 cm shorter than the length of the helix of the healthy ear, the operation was postponed by persuading the patient’s parents. The sixth,seventh and eighth rib cartilage on the contralateral side of microtia were havested for auricular reconstruction. The width of the synchondrosis of the sixth and seventh rib cartilage and the length of the eighth rib cartilage were measured intraoperatively, and the result was compared with the preoperative imaging measurement. The outcomes of the first-stage surgery in terms of shape, size, orientation, and structural details were assessed by the surgeon as well as the patients’ parents.Results:The preoperative rib measurements significantly correlated with the intraoperative measurements (P< 0.05). From 5 to 10 years of age, the growth of the synchondrosis of the sixth and seventh rib cartilage, the eighth rib cartilage and the helix of the healthy ear was not linear.Guided by the proximity of the length of the eighth rib cartilage on the contralateral side of microtia and the length of the helix of healthy ear cartilage framework, the operation was performed or delayed. In 76 (62.8%) of the 121 patients in the study, the length of the eighth rib cartilage was equal to that of the helix of the healthy ear, as measured preoperatively. Satisfactory surgical outcomes were achieved in all 76 of these patients, who underwent complete helix fabrication using the eighth rib. In 18 (14.9%) patients, whose eighth rib cartilage was approximately 1.0 cm shorter than the length of the helix of the healthy ear, helix fabrication was accomplished by adjusting the length of the helical crus in stent, Satisfactory surgical outcomes were achieved. Acceptable surgical outcomes were achieved in the 17 (14.0%) patients whose eighth rib cartilage was approximately 1.5 cm shorter than the length of the helix of the healthy ear, Helix fabrication was accomplished in these patients by combining the eighth rib cartilage and a spliced cartilage. In the 9 (7.4%) patients whose eighth rib cartilage was approximately 2.5 cm shorter than the length of the healthy ear cartilage framework, the operation was delayed. In one (0.8%) patient whose eighth rib cartilage was 2.3 cm shorter than the length of the healthy ear cartilage framework and in whom the operation could not be delayed due to the insistence of the parents, there was no cartilage left for splicing. The early surgical outcome in this patient was not adequate owing to our limited experience in early-stage operations.Conclusions:From years 5 to 10, growth of cartilaginous synchondrosis width between ribs 6 and 7 is not linear, the growth of the eighth rib cartilage is variable. Rib cartilage assessment relative to the healthy ear can guide auricular reconstruction and personalize treatment in young patients with microtia. |
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