[Modular construction (2 HS-1 SH), using Cotrel-Dubousset's universal instrumentation for comminuted fractures of the thoracolumbar junction. Comparison with various other constructions].

Introduction: The authors' objective was to study the anatomical and functional results of an original construct using the Cotrel-Dubousset instrumentation.

Material And Methods: This construct is called "Modular construct" or "2 H.S.-1 S.H." fits up two vertebrae above the fracture and a single below. So if the fracture is situated on the L1 level, a supra-laminar hook is set up on each side of T11, and two pedicular screws in T12 (2 H.S.). In the same way, a pedicular screw and an infra-laminar hook are set up on each side of L2 (1.S.H.). Two transverse bars connect together the right and the left rod. This retrospective work is based on the study of 24 patients who had a Thoraco-lumbar burst fracture according to Denis'classification, who were operated on in our Department, and started again to walk without external contention. All the patients had a postero-lateral bone graft. There were no [corrected] anterior arthrodesis performed. The average follow up was 4 years. This series was compared with a concomitant series of miscellaneous constructs realized by the same operators with the C.D. instrumentation.

Results: The average regional kyphosis angles went from 16.9 degrees in pre-operative to 3.9 degrees in post-operative, and 8 degrees at the maximum follow up. The average vertebral kyphosis angles went from 18 degrees in pre-operative to 3.8 degrees in post-operative, and 6.3 degrees at the maximum follow up. The miscellaneous constructs had poorer results. There were two severe infections, one early the other late.

Discussion: These results compared with the literature show that the 2 H.S.-1 S.H. construct is a competitive one. We think that its mechanical qualities arise from adding systematically hooks at the ends of the construct. These hooks protect the screws during flexion and from pull out constraints.