Objective:To compare the clinical effects of direct anterior approach (DAA) and posterolateral piriformis-sparing approach (Mis-PLA) for minimally invasive surgery of total hip arthroplasty.Methods: The patients who had total hip arthroplasty from March 2015 to February 2016 were randomly divided into 2 groups: DAA group and Mis-PLA group.In the study,43 patients (45 hips) were performed with total hip replacement via the direct anterior approach (DAA group).As comparison,39 patients (42 hips) were performed with total hip replacement via the posterolateral piriformis-sparing approach (Mis-PLAgroup) at the same period.DAA group:27 male patients (27 hips),and 16 female patients (18 hips),with an average age of (57.4±7.3) years,preoperative Harris score (41.4±8.7),body mass index(BMI)(24.3±2.2) kg/m2;Mis-PLA group: 25 male patients (26 hips),14 female patients (16 hips),with an average age of (59.2±7.3) years,preoperative Harris score (39.6±8.4),BMI (24.7±2.5) kg/m2.The length of incision,operation time,blood loss,postoperative Harris score were observed and specially the hip functional recovery was fully assessed.Results: (1) All the incisions healed by first intention.No complications were found in both groups.The length of incision:DAA group:(9.2±0.7) cm and Mis-PLA group:(9.5±0.6) cm.No statistical significant differences were found (P=0.053).The operation time:DAA group (74.3±10.1) min and Mis-PLA group(37.5±4.3) min,which showed statistically significant differences(P<0.01).Blood loss:DAA group(229.6±79.2) mL and Mis-PLA group (215.7±56.0) mL.Nostatistical significant differences were found (P=0.366).(2) The patients in both groups were followed up for 6-12 months.The Harris hip scores for 6 weeks' follow-up:(85.5±4.1) in DAA group and (79.0±4.4) in Mis-PLA group,which indicated statistically significant differences (P<0.01).The Harris scores for the 6-month follow-up:(94.3±2.7) in DAA group and (95.2±1.9) in Mis-PLA group.No statistically significant differences were found (P=0.125).The basic daily hip function analysis for the 6-week follow-up:walking speed: no statistically significant differences were found between the two groups(P=0.298);Climbing stairs: Mis-PLA group' outcome was better than DAA group's with statistical differences (P=0.047);Circling,sitting and wearing shoes and socks: outcomes in DAA group exceeded Mis-PLA group's with statistically significant differences (P<0.01,P=0.016,P<0.01).Conclusion: Total hip arthroplasty through either DAA or Mis-PLA approaches could result in very satisfactory clinical effect.Comparing with DAA,Mis-PLA requires less operation time,shorter learning curve,which indicates that it is a re-latively safer approach.The advantages of total hip arthroplasty through direct anterior approach lie in less positional limitation in the early stage of postoperative period,as well as a faster recovery of hip function.

Objective:To explore the significance of digital orthopedic technology in surgical plan for spinal tumor and the preliminary outcomes of 3D printed vertebral bodies in spinal tumor surgery.Methods:The clinical data of 2 patients were retrospectively analyzed who had had a 3D printed vertebral body implanted at Center of Orthopaedics, Shenzhen Hospital from June 2018 to December 2019. One was a 32-year-old male, diagnosed with cervical neurinoma; the other was a 27-year-old female, diagnosed with giant cell tumor of lumbar bone. 3D virtual reconstruction of tumor and surrounding structures was established via Mimics software for surgical plan. Virtual osteotomy was simulated, their disease models and guide templates were 3D printed, and their metal artificial vertebral bodies were 3D printed after personalized design of the vertebral body diameter, porosity and procedures of reconstruction and fixation. Lesion resection and prosthesis implantation were carried out in accordance with the preoperative plan. After operation, the motor function of cervical or lumbar vertebrae, tumor recurrence, and spinal stability reconstructed were regularly observed.Results:Resections and reconstructions went uneventfully in both cases. The 2 patients were followed up for 21 and 13 months respectively. Their postoperative images showed that their 3D printed vertebral bodies fitted the neighboring vertebral bodies well. The spinal stability was reconstructed without any loosening or periprosthetic osteolysis, and the tumors were removed completely with no recurrence in both cases. Their spinal motor function was satisfactory.Conclusions:Digital orthopedic technology can offer accurate guidance in the treatment of spinal tumors. It is necessary to consider local physiological anatomy in personalized design of a metal vertebral body 3D printed. Clinical application of 3D printed metal vertebral bodies is a new strategy for spinal reconstruction following spinal tumor resection.