Download Cd Jota Quest Ao Vivo 2003
Sandrine Willert
Methods: The caudal 3/4 intervertebral disc (IVD) of the rat tail was approached by two surgical techniques: blunt dissection, stripping and retracting (Technique 1) or incising and repairing (Technique 2) the dorsal longitudinal tendons. The intervertebral disc was dissected and removed, and then either discarded or reinserted. Outcome measures were perioperative complications, spontaneous tail movement, 7T MRI (T1- and T2-sequences for measurement of disc space height (DSH) and disc hydration). Microcomputed tomographic imaging (micro CT) was additionally performed postmortem.
Results: No vascular injuries occurred and no systemic or local infections were observed over the course of 1 month. Tail movements were maintained. With tendon retraction (Technique 1) gross loss of DSH occurred with both discectomy and reinsertion. Tendon division (Technique 2) maintained DSH with IVD reinsertion but not without. The DSH was demonstrated on MRI measurement. A new scoring system to assess IVD appearances was described.
Conclusions: The rat tail model, with a tendon dividing surgical technique, can function as an orthotopic animal model for IVD research. Mechanical stimulation is maintained by preserved tail movements. 7T MRI is a feasible modality for longitudinal monitoring for the rat caudal disc.
The athymic rat tail model does appear to provide a potential animal model for future investigation into intervertebral disc replacement with appropriate technique in this prospective randomized animal study. This paper clearly demonstrates sharp dissection is superior to blunt detachment to maintaining intervertebral disc height, an interesting tangent as we learn more about soft-tissue dissection and maintenance of viable margins. There are, however, some significant limitations to this study.
One limitation lies in the inability of the rat tail model to provide significant axial loading upon the discs as would be the case in bipedal animals or in the actual spinal column of the investigated animals, as mentioned by the authors. In addition, the short-time frame of follow-up is of concern. Longer outcomes involving athymic rats may be necessary in order to understand if the replanted discs can withstand longer durations than just the 30 days. A 90-day window or even longer would seem to be more relevant to establish ingrowth and cartilage cell survival.
Detailed analysis of the results of the disc replacement or removal with clinical assessments, function, and imaging with MRI and micro CT is clearly one of the strengths of this paper. The comprehensive approach to imaging allows for very clear comparisons between the two surgical approaches of discs that were replanted or discarded.
There is no question of the importance of developing an appropriate animal model for the future quest for biological intervertebral disc replacements in an in vivo setting. A workable animal model will certainly facilitate future research opportunities and development of the disc replacements. Whether the athymic rat tail model will turn out to be the optimal model or not, this novel model certainly presents a laudable launching point for further investigations.