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

One hundred-seventy embalmed cadaver wrists were dissected. The type of lunate (type I, no medial hamate facet; type II, medial hamate facet), the incidence and location of arthrosis (exposed subchondral bone) in the lunohamate joint, and the anatomic relationship of the volar triquetrocapitate (T-C) and the volar triquetrohamate (T-H) ligaments were identified and measured. 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 ligament, 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 proximal pole of the hamate. Eighty-two percent of type I lunates were associated with a type A relationship between the T-C and the T-H ligaments and 96% of type II lunates were associated with a type C relationship between the T-C and the T-H ligaments. Arthrosis at the proximal pole of the hamate was more commonly associated with the type II lunates (49%) and with the type C relationship (57%) of the T-C and T-H ligaments. The incidence of arthrosis in the lunohamate joint was also significantly greater in the type II lunate with a medial facet of 3 mm or more.