From a transcription on constitution.org, including footnotes, we have what seems to be a fuller text of this clause (Tablet III, law X)
Law X - Where a party is delivered up to several persons, on account of a debt, after he has been exposed in the Forum on three market days, they shall be permitted to divide their debtor into different parts, if they desire to do so; and if anyone of them should, by the division, obtain more or less than he is entitled to, he shall not be responsible
The footnote for this law being:
While a strict construction of the provisions of this law has been rejected by some jurists, there can be little doubt that its abhorrent features, far worse than those of the famous claim of Shylock, were susceptible of literal interpretation, and that the partition of the body of the unfortunate debtor was entirely dependent upon the inclination of his creditors to whom he had been adjudged. The statement of Aulus Gellius relative to a fact evidently well known to his countrymen, would seem to be conclusive upon this point. "Nam, si plures forent, quibus reus esset judicatur, secare si vellent, atque partiri corpus addicti sibi hominis permiserunt." (Aul. Gell. Nodes Atticæ. I. XX. 1.)
Fabius, alluding to the same law, says that public sentiment was opposed to its enforcement. "Quam legem mos publicus repudiavit." In view of the eminent authority of these Roman writers, and the clear meaning of the text, the opinion entertained by some respectable commentators, that the word "secare," "to divide," merely has reference to the apportionment of the debtor's property, is hardly tenable, as it must have been already taken in execution and divided, before his person was delivered up to gratify the resentment of his disappointed creditors.
You'd imagine that if there were any notable cases of this law being enacted and documented by classical commentators, it would have been mentioned here. I assume therefore that there probably aren't any documented cases of debtors being torn asunder.
The source (as used by the Constitution website) of the quoted text appears to be:
The Civil Law, tr. & ed. Samuel Parsons Scott (1932) — Includes the classics of ancient Roman law: the Law of the Twelve Tables (450 BCE), the Institutes of Gaius (180), the Rules of Ulpian (222), the Opinions of Paulus (224), the Corpus Juris Civilis of Justinian (533), which codified Roman Law, and the Constitutions of Leo.