Feasibility of Computer-Aided Design in Limb Lengthening Surgery: Surgical Simulation and Guide Plates

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 +/-$$ \pm $$ 8.57 (range, 24-45) to 61.17 +/-$$ \pm $$ 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.