[How much intervertebral disk tissue is in reality removed in percutaneous nucleotomy?].

In an experimental study with standardized conditions nuclear material of 40 human lumbar discs was excised. In 20 the non-automated discectomy method was used (NAPLD-method). In the other 20 the automated discectomy method (APLD-method). The excised material was weighted. After the removal, the material of the NAPLD-method was wet with isotonic saline over 45 minutes and again weighted. Afterwards the wet material of both methods was freeze dried and again weighted. The weight of the wet material of the NAPLD-method in relation to that of the freeze dried material was a factor 11 (average value: 7.7 g in relation to 0.7 g) and in the APLD-method a factor 15 (average value: 4.5 g in relation to 0.3 g). This means, that the uptake and distribution of the saline is different in both methods and for this reason it is not allowed to compare the wet weight of the two methods. This has to be considered in clinical comparative studies. Because the biomechanical changes after a discectomy are dependent of the amount of the excised nuclear material, the NAPLD- and APLD-method can only be compared when the amount of the excised material is changed in a freeze dried weight.