As you can see, the text is about the killing of animals (cows were mentioned) for meat consumption. If you follow this link, you will see what the process is like:
https://www.hsa.org.uk/bleeding-and-pithing/pithingWe can legitimately wonder, was it right for the original text to call it نخر? The answer is: it does not matter. We did not call it so. The Arabic document before us did. Perhaps they used the term correctly, perhaps not. What matters is that we know what they meant, and we know how to say it in English (correctly).
Incidentally, if you look in المعجم الطبي الموحد, you will find that "spinal pithing" is translated تخريب النخاع الشوكي.
Translation is a unidirectional process in the following sense: When you translate a text from Arabic to English (or vice versa), you find the correct English expression to convey the idea in the Arabic text. But if you were asked later to translate your English translation to Arabic, you may or may not translate it back to the Arabic text that you started with, because the original text may have been faulty. That fault is not our fault as translators. If the original text has a fault, we work around it to faithfully convey the idea.