Objective:To explore the application value of digital technology in free transfer of ALTPF to repair large-area soft tissue defect of limbs.Methods:A total of 13 patients with large-area soft tissue defects of limbs treated from April 2017 to April 2020 were selected in the study, including 9 males and 4 females, aged 39-58 years old. The average age was (42.75±1.94) years old. The area of flap was 16 cm×10 cm-27 cm×18 cm. Before operation, CTA was performed on the donor and recipient areas, and the 3-dimensional image of arterial blood supply in the donor area was obtained by 3-dimensional digital reconstruction technology of CT angiography, so as to clarify the origin, course, classification, length vascular pedicle, of diameter and location of perforating fulcrum of the blood supply of ALTPF. According to the image parameters 3-dimensional, of the defect of the recipient area was reconstructed and designed with Mimics software, and the 3-dimensional digital designed flap was used accurately and standardized during the operation.Results:All the 13 flaps survived without a vascular crisis. The patients entered the follow-up for 6 to 24(mean 16) months by outpatient clinic visits combined with WeChat reviews. At the last follow-up, the surviving flaps had soft texture and good blood supply, the shape and colour of the flap were basically the same as those of normal skin. The limb function recovered well. According to Chinese Medical Association Upper Limb Function Evaluation (TAM) method and Maryland ankle function evaluation method: 8 cases were in excellent, 3 cases were in good and 2 cases were in fair.Conclusion:The preoperative application of digital technology to assist the reconstruction of large-area soft tissue defects of limbs with free ALTPF has high accuracy and standardisation. It improves the quality and success rate of free flap repair. This method is reliable, practical and with clinical value.

Objective:To compare internal fixation with 3 cannulated screws versus with an anteromedial support plate plus 3 cannulated screws using finite element analysis for unstable femoral neck fractures (Pauwels type Ⅲ).Methods:Recruited for this study was a 34-year-old male volunteer with a height of 173 cm and a weight of 75 kg. Continuous thin-layer helical CT was conducted to scan the segment from his hip joint to the middle shaft of his tibia. Digital medical software was used to establish three-dimensional models of the femur based on his femoral CT data. The digital femoral necks were dissected as necessary to simulate femoral neck fractures of Pauwels type Ⅲ. The fractures were fixated with 3 ordinary cannulated screws in a mode of inverted triangle (screw group) and with 3 ordinary cannulated screws in a mode of inverted triangle plus an anteromedial steel plate (screw-plate group). After the 2 groups of models were subjected to identical constraints and 3 kinds of load (slow walking, twisting and standing on one leg), they were compared in terms of distribution of Von Mises stress and deformation.Results:Under various loads in both groups, the maximum deformation occurred in the femoral head. In the condition of slow walking, the deformation in the screw-plate group was 1.97 mm, which was smaller than that in the screw group (2.26 mm). In the conditions of twisting and standing on one leg, similar deformations were observed in both groups. Under all kinds of load, the maximum stress occurred in the middle part of the bottom screw and the fracture line in all the models. In the screw group, the peak stresses were 318.09 MPa, 92.11 MPa and 147.21 MPa for conditions of slow walking, twisting and standing on one leg, greater than those in the screw-plate group (229.86 MPa, 86.94 MPa and 124.48 MPa).Conclusions:The cannulated screws plus an anteromedial support plate are a recommendable fixation method for young adults with unstable femoral neck fracture, because they can effectively share the stress on the cannulated screws, lead to better mechanical stability of the fracture ends than the fixation with merely 3 cannulated screws and effectively prevent shortening of the femoral neck.