Minimally Invasive Percutaneous TightRope® System Fixation for an Unstable Posterior Pelvic Ring: Clinical Follow-up and Biomechanical Studies

Objective: To evaluate the mechanical stability and clinical efficacy of minimally invasive percutaneous TightRope (R) systems applied via gun-shaped reduction forceps for unstable posterior pelvic ring fractures. Materials and methods: This study consists of two parts: a clinical retrospective study and a randomized controlled biomechanical test. For the clinical study, a retrospective analysis of posterior pelvic ring fractures was performed between June 2015 and May 2020. Eighteen patients underwent surgery using two TightRope (R) systems to fix a broken posterior pelvic ring because of unstable AO type C1 and C2 pelvic ring fractures. The patients were followed up for at least 2 years, and all patients were evaluated using the Majeed scoring system and vertical displacement. In the biomechanical tests, six embalmed adult pelvic specimens were used. The fractures were subjected to TightRope (R), IS screw, and TBP fixation in a randomized block design. The specimens were placed in a biomechanical testing machine in a standing neutral posture. A cyclic vertical load of up to 500 N was applied, and the displacement of the specimens was recorded by the testing machine. The ultimate load in each group of specimens was recorded. The displacement and ultimate load were compared and analyzed by statistical methods. Results: At a mean follow-up of 38.89 +/- 8.72 months, the functional Majeed score was excellent in 14 patients and good in four patients. The final radiological examinations showed that the outcome was excellent in 14 patients and good in four patients. In these patients, no serious clinical complications were found. Weight-bearing was delayed in four patients. In biomechanical tests, the displacement of the specimens fixed with TightRope (R) was significantly lower than that of the specimens fixed with TBP (P < 0.05) when the load ranged from 300 to 500 N. The displacement in the IS screw group was significantly lower than that in either the TBP or TightRope (R) group (P < 0.05) when the load ranged from 0 to 500 N. The ultimate load in the IS screw group (1798 +/- 83.53 N) was significantly greater than that in the TBP group (1352 +/- 74.41 N) (t = 9.78, P < 0.0001) and the TightRope (R) group (1347 +/- 54.28 N) (t = 11.11, P < 0.0001). However, no significant difference was observed between the TightRope (R) and TBP groups (t = 0.13, P = 0.90). Conclusion: Percutaneous posterior TightRope (R) system shows strong stability in mechanical experiments and shows good results in clinical follow-up while this system has certain advantages in lower surgical requirements and lower risk of related nerve and vascular structural damage.