Letter to the Editor Does the 'hybrid multidirectional test method' generate quality data or paradoxical data?

摘要

Panjabi has proposed a new biomechanical testing protocol for studying adjacent-level effects (Panjabi, 2007), termed the "hybrid multidirectional test method," that is essentially specimen-specific displacement-controlled testing using pure moments. For this testing method, multilevel cadaveric spine specimens are used in which one or more levels will receive disc replacement, fusion, or other treatment. First, in normal intact specimens, the global range of motion (RoM) is found as the angle reached under applied load of a pre-chosen magnitude that induces in vivo-like motion (for example, 1.5 Nm for the cervical spine (Panjabi et al., 1991) or 10.0Nm for the lumbar spine (Panjabi et al., 1989)). Subsequently, after treating the index level(s), the applied moment is modulated to control global displacement to the same global RoM value previously reached in the normal condition. Any alteration in biomechanics at the adjacent untreated levels is then attributed to the changes in the biomechanics of thetreated index level. Although it is commendable to seek a testing method that can be easily reproduced among laboratories, I am skeptical of this proposed method and believe that the misleading and biased data generated by this testing protocol negate the value of its reproducibility.