From the Lexicon Ambrosianum. Headword and gloss are present participles in the masculine nominative plural, the headword that of the verb ἐκαθίημι , in the middle voice.
This form occurs (otherwise) only in the Catena in Epistulam ad Romanos (Oxon. Boedl. Auct. 2.2) and in Cyril of Alexandria Fragmenta in Sancti Pauli epistulam ad Romanos 197 (quoting the former).
For the (commonplace) glossing participle cf. iota 152. Here its elucidatory function appears to be twofold: to show that the headword is middle rather than passive, and to convey the sense of the double compound ἐγκαθ .