THE UNSTABLE SPINAL COLUMN - AN IN-VITRO AND IN-VIVO STUDY TO UNDERSTAND CLINICAL INSTABILITY BETTER

In cases of suspected painful instability of a cervical segment, tempo rary external fixation by means of external fixator was applied. The s egmental immobilization caused immediate relief of pain. The pain reoc curred after removal of the immobilization. The effect of immobilizati on by external fixation was investigated in biomechanical tests using fresh cadaveric C4-7 specimens. Multidirectional flexibility was measu red before and after application of the fixator at C4/C5, C5/C6 and C4 -6. We measured the reduction in motion between the different segments . In every situation the neutral zone decreased more than the range of motion. The findings are helpful to understand the clinical instabili ty of the spine and support the hypothesis that the neutral zone is mo re closely associated with clinical instability than range of motion. The combination of clinical application and biomechanical investigatio n allowed us to establish a direct correlation between instability and pain.