Embryologic development and variations in the anatomy of the ulnocarpal ligamentous complex

Eighteen fetal hand specimens were reviewed in an effort to clarify variations in reports of the ligamentous anatomy of the ulnar side of the wrist. Sizes ranged from 45 mm crown-rump length (CRL) to 325 mm CRL. Representative coronal sections from the 2779 sections available were reviewed. Significant variations in size of triquetral attachment and thickness and consistency of the ulnocarpal ligamentous complex (UCLC) were observed. Each of the specimens exhibited one of four UCLC variations: (1) 5 of 18 (28%) with an average CRL of 187 mm had a dense, thin UCLC, with a focal triquetral attachment; (2) 7 of 18 (39%) with an average CRL of 209 mm had a focal, dense attachment of a thick UCLC to the triquetrum; (3) 5 of 18 (28%) with an average CRL of 220 mm exhibited a thick, dense UCLC with a broad attachment to the triquetrum; and (4) 1 of 18 (5%) with a CRL of 166 mm was unique, with a loose, areolar UCLC broadly attached to the triquetrum.