Minimal-invasive triangular fixation with orthopaedic robot for unilateral unstable sacral fracture

Objective To compare the clinical outcomes between minimal-invasive triangular fixation with orthopedic robot and traditional open fixation method for unilateral unstable sacral fracture patients. Methods Data of 24 consecutive patients with unilateral unstable sacral fracture who were treated from August 2014 to February 2018 were retrospectively analyzed. All patients were associated with anterior ring injuries of pelvis and received magnetic resonance of nerve (MRN) preoperatively to exclude the compression of sacral nerve by bone. All patients received surgical treatment of sacral fractures with triangular fixation and the fixation of pelvic anterior ring injuries simultaneously and two groups were divided according to the different surgical methods of sacral fractures. There were 10 males and 2 females with an average age of 36.3±1.2 years in the orthopaedic robot group. According to Dennis classification, there were 4 type I and 8 type II fractures. Two patients were associated with nerve injuries (Gibbons II 1 case, III 1 case). In traditional posterior-midline open fixation group, there were 11 males and 1 female with an average age of 38.2±1.6 years. According to Dennis classification, there were 3 type I and 9 type II fractures. Three patients were associated with nerve injuries (Gibbons II 2 cases, III 1 case). The clinical data of two group patients were collected and compared statistically. T test was used to compare the operation time, intraoperative bleeding, intraoperative fluoroscopy times, Majeed function assessment which was to evaluate the patients' clinical prognosis and healing time of fracture. χ2 test was used to compare the healing rate of fracture, accuracy assessment of fixation insertion, and Mears radiological assessment which was applied to evaluate the reduction quality of fractures. The rank sum test was used to compare Gibbons score which was applied as the index of neurological deficiency recovery. The Fisher exact test was used to compare the infection rate. Results All patients were followed up continuously for an average time of 21.2±3.2 months. The average operation time of robot group was 100.3±14.5 minutes, meanwhile the open fixation group was 202.0±18.5 min. The average intraoperative bleeding of robot group was 180.0±17.4 ml, meanwhile the open fixation group was 850.0±15.2 ml. The average intraoperative fluoroscopy time of robot group was 23.3±4.5 s, meanwhile the open fixation group was 90.0±7.7 s. All fractures were healed and no loss of reduction or fail of fixation occurred in both groups. The healing time of fracture of robot group was 8.5±1.9 months, meanwhile the open fixation group was 12.8±2.4 months. The satisfaction rates of reduction which was based on Mears-Velyvis radiological criterion of both groups were 91.7%. The accuracy rate of fixation insertion of robot group was 100% meanwhile the open fixation group was 77.78%. Majeed function assessment score of robot group was 86.2±3.4, meanwhile the open fixation group was 84.2±2.7. There was no infection occurred in robot group, meanwhile 3 patients infected in open fixation group. The Gibbons score of one patient changed from II preoperative to I postoperative and one case changed from III preoperative to II postoperative in robot group, meanwhile two patients changed from II preoperative to I postoperative and one case changed from III preoperative to II postoperative in open fixation group. The healing rate of fracture, infection rate, Majeed function assessment, Mears-Velyvis radiological evaluation criterion and Gibbons score of two groups had no significant statistical difference (P >0.05), meanwhile the operation time (t=14.99), intraoperative bleeding (t=100.46), intraoperative fluoroscopy time (t=32.13), healing time of fracture (t=4.87) and accuracy rate of fixation insertion (χ2=9.00) of orthopedic robot group were better than traditional open group and had the significant difference (P< 0.05). Conclusion The minimal-invasive triangular fixation with orthopedic robot for unilateral unstable sacral fracture had the advantages of less operation time, less intraoperative bleeding and less times of fluoroscopy, more accurate of fixation insertion and less healing time of sacral fractures compared to traditional open fixation method and should be recommended as an effective and advanced choice. Key words: Sacrum; Fractures, bone; Fracture fixation, internal; Internal fixators