[Biomechanical study and clinical application of distraction reduction fixation system for treating thoracolumbar...

To investigate the biomechanical characteristics of self-developed distraction reduction fixation system (DRFS) and to evaluate its clinical effect on thoracolumbar vertebrate fracture.

Twelve fresh porcine spines were prepared for the biomechanical test. The stiffness of each intact specimen were recorded on forward bending (20 degrees), backward bending (10 degrees), lateral bending (30 degrees) and axial rotation (20 degrees), and then specimens of fracture dislocation were made by cuneiform osteotomy of L3 vertebral body and excision of posterior facet joints. Finally, DRFS internal fixation was performed on each specimen. The stiffness of specimens in fracture dislocation and after DRFS fixation were measured during the same movements mentioned above, respectively. The clinical effect of DRFS on thoracolumbar vertebrate fracture in 31 patients (aged 17-46 years with an average of 32.1) from April 1998 to October 2002 was summarized. Fracture types were classified according to Denis classification: 2 patients suffered simple compressed fracture, 16 burst fracture, and 13 fracture dislocation, including 2 cases of T11, 11 cases of T12, 14 cases of L1 and 4 cases of L2. Frankel and X-ray examination were adopted to assess the results.

The stiffness during forward bending, backward bending, lateral bending and axial rotation in the fracture-dislocation state was markedly lower than that of the corresponding movements of the intact porcine spines (P < 0.05). After DRFS, the stiffness during various movements increased to the level that significantly higher than that in the fracture-dislocation state (P < 0.05), and the stiffness during backward bending was of significant difference (P < 0.05), but without significant difference during the rest three movements (P > 0.05) when compared to that in intact spines. Regarding clinical observation, the operation time was 2.2-4.1 hours (2.7 hours on average) and blood loss was 250-600 mL (450 mL on average). The patients were followed up for 5-20 months (10.2 months on average). The healing time for fracture was 5-1 months (8 months on average). The mean anterior and posterior heights of the injured vertebrate recovered from 46.2% +/- 7.5% and 76.4% +/- 2.4% preoperatively to 89.8% +/- 4.6% and 94.1% +/- 1.5% postoperatively (P < 0.05).The median point height also raised from 60.8% +/- 6.4% to 90.7% +/- 2.9% (P < 0.05). The Cobb's angle decreased from (26.3 +/- 5.9)degrees to (5.2 +/- 1.8)degrees (P < 0.05), and all the slipped vertebrates were well repositioned. Spine function was assessed by Frankel classification as follows: 2 of 5 Class A preoperatively improved to Class B postoperatively, and the other 3 remained unchanged; 4 of 6 from B to C, and the other 2 to D; 6 of 13 from C to D, and the other 7 to E; and 7 from D to E.

DRFS is capable of providing sufficient stability, meeting the requirement of the spine physical activity without any obvious side effect. DRFS, as a handy, safe and effective technique in clinical practice, is featured by satisfying functions of distraction, reposition and fixation.