Objective: To discuss the clinical outcomes of treating delayed acetabular fractures by combined anterior and posterior approach. Methods: A retrospective analysis was conducted of 31 delayed acetabular fractures from February 2012 to February 2017 in the First Affiliated Hospital of Chongqing Medical University, including 18 males and 13 females with age of 48.5 years(23 to 67 years) .The injury to the operation time was 35.9 days(22 to 183 days). Of these 31 cases, there were 6 cases of transverse and posterior wall fracture, 8 cases with anterior column+ posterior half transverse fracture, 12 cases with double column fracture and 5 cases of "T" type fracture according to Letournel-Judet classification.All fractures were treated combined anterior and Kocher-Langenbeck approaches, including 13 cases of ilioinguinal approach+ Kocher-Langenbeck(K-L approach), 4 cases of extensile acetabular approach, 7 cases of stoppa approach + K-L approach and 7 cases of side rectus femoris approach.Correlation was analyzed by Pearson correlation regression testing. Results: Follow up to August 2017, all patients were followed up with 36.0 months(from 6 to 55 months). As calculated, the restorational effect was positively with result of the X-ray film and the clinical effect(r=0.823, 0.856; both P<0.05). The evaluation was conducted with Matta′s reduction criteria: there were 11 cases classified as anatomic reduction(35.5%), 13 cases as satisfactory reduction(41.9%), and 7 cases as unsatisfactory reduction(22.6%). Excellent and good rate was 77.4%. Functional reductions were categorized by the standard of Matta hip score: 8 excellent cases(25.8%), 11 good cases(35.5%), 8 fail cases(25.8%), and 4 poor cases(12.9%). Conclusion The treatment of delayed acetabular fracture by combined anterior and posterior approach can fully exposure the anterior and posterior acetabular fcloumns, which is beneficial to the release and fixation of the old acetabular fractures.

Objective To compare the dose difference between the 12-bit and 16-bit CT images containing metallic implants calculated by different algorithms. Methods The titanium alloy rod was inserted into the phantom and subject to CT scan and then the 12-bit and 16-bit CT images were reconstructed. The CT images were online transmitted to the Monaco planning system and a 0° of single field was designed. The dose distribution was calculated by PB (Pencil Beam), CC (Collapsed Cone) and MC (Monte Carlo) algorithms, respectively. The CT-ED curve was expanded and the dose was recalculated. The depth dose curve through the center of the metallic implants along with the direction of the field was obtained by using the Matlab 8. 3 statistical software. The dose distribution curves between 12-bit and 16-bit CT images calculated by different algorithms and the dose difference of varying distances between the incident and the exit surfaces of metallic implants were statistically compared. The dose was measured by thimble chamber. Results The 16-bit CT images accurately read the CT values of the metallic implants. After the CT-ED curve was expanded, the dose on the incident surface of metallic implant was reduced by 5. 43% and that on the exit surface was increased by 25. 56% calculated by PB algorithm compared with MC algorithm. The dose on the posterior exit surface was higher than that of MC algorithm. The dose on the incident surface of metallic surface was decreased by 4. 5%, whereas that on the exit surface was reduced by 4. 31% using CC algorithm. The dose on the posterior exit surface was more significantly reduced. The calculated values by MC algorithm were the most close to the measured values. Conclusions Application of 16-bit CT image, CT-ED curve expansion of the treatment planning system combined with MC algorithm can enhance the accuracy of dose calculation for the patients containing metallic implants during radiotherapy.