Combined anteroposterior spinal fixation provides superior stabilisation to a single anterior or posterior procedure

Fusion is the main goal in the surgical management of the injured and unsta ble spine, A wide variety of implants is available to enhance this. Our stu dy was performed to evaluate the stabilising characteristics of several ant erior, posterior and combined systems of fixation, Six thoracolumbar (T11 t o L2) spines from 13-week-old calves were first tested intact. Then the ver tebral body of T13 was removed and the defect replaced and supported by a w ooden block to simulate bone grafting. Dorsal implants consisting of a Univ ersal Spine System (USS) fracture system and an AO Fixateur interne (AOFI), and ventral implants comprising of a Kaneda Classic, a Kaneda SR, a protot ype of the VentroFix single clamp/single rod construct (SC/SR) and the Vent roFix single clamp/double rod construct (SC/DR) were first implanted indivi dually to stabilise the removal of the vertebral body. Simulating the combi ned anteroposterior stabilisations, all ventral implants were combined with the AOFI, The range of motion (ROM) was measured under loads of up to 7.5 Nm. The load was applied in a custom-made spine tester in the three primary directions while measuring the intervertebral movements using a goniometri c linkage system. The dorsal systems limited ROM in flexion below 0.9 degrees and in extensio n between 3.3 degrees and 3.6 degrees (median values). The improved Kaneda System SR yielded a mean ROM of 1.8 degrees in flexion and in extension. Th e median rotation found with the VentroFix (SC/DR) was 3.2 degrees for flex ion and 2.8 degrees for extension. Reinforcement of the ventral constructs with a dorsal system reduced the ROM in flexion and extension in all cases to 0.4 degrees and lower. In rotation, the median ROM of the anterior systems ranged from 2.7 degrees to 5.1 degrees and for the posterior systems from 3.9 degrees to 5,7 degre es, while the combinations provided a ROM of 1.2 degrees to 1.9 degrees. In lateral bending, the posterior implants restricted movement to 1.1 degrees , whereas the anterior implants allowed up to 5.2 degrees. The combined sys tems provided the highest stability at less than 0,6 degrees. Our study revealed distinct differences between posterior and anterior appr oaches in all primary directions. Also, different stabilisation characteris tics were found within the anterior and posterior groups. Combinations of t hese two approaches provided the highest stability in all directions.