RESUMO
OBJECTIVE: Segmental bone defect animal studies require stable fixation which is a continuous experimental challenge. Large animal models are comparable to the human bone, but with obvious drawbacks of housing and costs. Our study aims to utilize CAD and 3D printing in the construction of a stable and reproducible segmental bone defect animal mode. METHODS: CAD-aided 3D printed surgical instruments were incorporated into the construction of the animal model through preoperative surgical emulation. 20 3D printed femurs were divided into either experimental group using 3D surgical instruments or control group. In Vitro surgical time and accuracy of fixation were analysed and compared between the two groups. A mature surgical plan using the surgical instruments was then utilized in the construction of 3 segmental bone defect Beagle models in vivo. The Beagles were postoperatively assessed through limb function and imaging at 1, 2 and 3 months postoperatively. RESULTS: In vitro experiments showed a significant reduction in surgical time from 40.6 ± 14.1 (23-68 min) to 26 ± 4.6 (19-36 min) (n = 10, p < 0.05) and the accuracy of intramedullary fixation placement increased from 71.6 ± 23.6 (33.3-100) % to 98.3 ± 5.37 (83-100) %, (n = 30, p < 0.05) with the use of CAD and 3D printed instruments. All Beagles were load-bearing within 1 week, and postoperative radiographs showed no evidence of implant failure. CONCLUSION: Incorporation of CAD and 3D printing significantly increases stability, while reducing the surgical time in the construction of the animal model, significantly affecting the success of the segmental bone defect model in Beagles.
RESUMO
OBJECTIVE: To evaluate the feasibility and utility of computer-aided design (CAD) in surgical treatment of leg length discrepancy (LLD) using monorail external fixators. METHODS: In the present case series, we retrospectively analyzed seven patients diagnosed with LLD who were surgically treated using a monorail external fixator between June 2018 and August 2020. A personalized surgical emulation of each patient was designed using CAD based on preoperative CT scans to measure limb parameters. Through reverse engineering, a surgical guide plate was then designed to assist with correcting the limb deformity. Patient general information and clinical history, leg length, mechanical lateral distal femoral angle (mLDFA), anatomical anterior distal tibial angle (aADTA), and surgical parameters were recorded during the perioperative period. Three months after external fixator removal, distraction-consolidation time (DCT), healing index (HI), and lower extremity function score (LEFS) were calculated, and statistically analyzed by paired T-test. RESULTS: The mean limb lengthening achieved was 6.41 ± 2.54 (range, 3.30-10.54) cm with either varus or valgus correction. The mean operative duration was 151 ± 41.87 (84-217) minutes and mean blood loss was 53.58 ± 22.51(25-87) ml. The mean distraction-consolidation time was 3.67 ± 1.13 (range, 2.5-6.0) months and mean external fixator duration was 11 ± 2.45 (range, 8-14) months. The mean healing index (HI) was 18.11 ± 3.58 (range, 12.8-22.7) days/cm. Mean LEFS scores improved postoperatively from 32.17 ± 8.57 (range, 24-45) to 61.17 ± 6.68 (range, 50-67) with a significant difference (T = -14.26,P < 0.001). CONCLUSIONS: Simultaneous length and angular correction can be achieved by incorporating CAD into the surgical treatment of patients with LLD, without compromising postoperative lower limb function. CAD demonstrates utility in the surgical treatment of LLD by improving the functionality of monorail external fixators.
