OBJECTIVETo evaluate the biomechanical stability of Shen's instrumentation in the management of thoracolumbar fractures.

METHODSThe ranges of movement (ROM) in three dimensions of twelve T(12) - S(3) specimen of fresh adult cadavers were measured sequentially in the states of normal, injured, GSS and SOCON fixation, fatigued GSS and SOCON fixation. Data were then compared.

RESULTSFor the L(2 - 3) segment, the average normal ROM in flexion was 8.3 degrees. In the established spondylolisthesis models, the ROM was 14.7 degrees. After fixation with SOCON, the ROM was decreased to 3.0 degrees, indicating that SOCON fixation can produce good stability. The ROM after fatigue test was 3.6 degrees, significantly lower than that of the normal state, indicating that SOCON still produces good stability after fatigue. For the L(4 - 5) segment, the average normal ROM in flexion was 8.6 degrees. In the established spondylolisthesis models, the ROM was 13.7 degrees. After GSS fixation, the ROM was decreased to 3.2 degrees, significantly lower than that in the normal state, indicating that GSS fixation can produce good stability. ROM after fatigue test was 3.7 degrees, significantly lower than that of the normal state, indicating that GSS can produce good stability after fatigue. The ROM measurements in the other five directions were similar to those for flexion described above.

CONCLUSIONGSS produces good stability for spondylolisthesis, good fatigue resistance, and can be used in pedicle screw revision surgery. There were no significant differences between GSS and SOCON.