Type I versus type II lunates: Ligament anatomy and presence of arthrosis

One hundred-seventy embalmed cadaver wrists were dissected. The type of lun ate (type I, no medial hamate facet; type II, medial hamate facet), the inc idence and location of arthrosis (exposed subchondral bone) in the lunohama te joint, and the anatomic relationship of the volar triquetrocapitate (T-C ) and the volar triquetrohamate (T-H) ligaments were identified and measure d. The relationship between the T-C and T-H ligaments was classified into 3 types. In type A the T-C ligament was completely separate from the T-H lig ament, in type B the T-C ligament overlapped the T-H ligament, and in type C the T-C ligament had an additional ligament from the triquetrum to the pr oximal pole of the hamate. Eighty-two percent of type I lunates were associ ated with a type A relationship between the T-C and the T-H ligaments and 9 6% of type II lunates were associated with a type C relationship between th e T-C and the T-H ligaments. Arthrosis at the proximal pole of the hamate w as more commonly associated with the type II lunates (49%) and with the typ e C relationship (57%) of the T-C and T-H ligaments. The incidence of arthr osis in the lunohamate joint was also significantly greater in the type II lunate with a medial facet of 3 mm or more. Copyright (C) 2001 by the Ameri can Society for Surgery of the Hand.