Analysis of triquetral-lunate fusion.

Fusion of the centers of the triquetral and lunate (the 0s lunatotriquetrum) was observed in 1.6% of 7,543 subjects primarily of African origin as compared with 0.1% of 11,663 persons of European origin. The fusion was twice as common in females as in males, multifactorial inheritance was suggested in the lineages studied, and a possible selective disadvantage was postulated after comparison with West African fusion frequencies, Although any pair of adjacent carpal centers may exhibit fusions (O’Rahilly, ‘53, ’57), those on the ulnar side and the same row are most commonly involved. The capitate and the hamate are the most frequently fused carpal centers of the distal row and those of the 0s triquetrum and 0s lunatum in the proximal row. Triquetrallunate fusion, moreover, exhibits notable geographical diversity, with a frequency well under 1% in Europeans, 1-2% in East Africans and a reported maximum of 8-9% in the Hausa of Nigeria (Smitham, ’48; MacKay, ’52; Silverman, ’55; Cockshott, ’63). In the course of the recent Ten-State Nutrition Survey of the United States, we have been able to provide new estimates of the frequency of triquetral-lunate fusion in an unusually large sample of non-hospitalized volunteers, exceeding in number all previous survey data combined. Starting with 26,304 postero-anterior handwrist radiographs of subjects of known age, sex and origin, we have narrowed the sample to 21,715 subjects in whom the radiographic images provided sufficient indication of lunate and triquetral development to make the diagnosis of fusion certain. Subjects with rheumatoid arthritis, arthrogryposis and other anomalies ordinarily associated with fusion were excluded. I As shown in the table, triquetral-lunate carpal fusion (the 0s lunatotriquetrum) is extremely rare in subjects of European ancestry, probably no more frequent than AM. J. PHYS. ANTHROP., 34: 431434. one per thousand, in our combined-sex tabulations. The frequency of fusion of these two bones appears to be of a comparable order for American Indians (primarily Navajos) and Mexican-Americans (“Chicanos”) studied. However, in participants indicated in the category “Black (American Negroes, American Colored), the frequency is nearly 16 per thousand. For combined-sex tabulations, the frequency of triquetral-lunate fusion is 1.0 per thousand in 11,663 subjects of European ancestry and 15.8 per thousand in 7,543 subjects primarily of African ancestry. In all groups considered here, triquetrallunate fusion was more frequent in females than males, both in children and adults, hence not an artifactual product of the developmental advancement of the female hand skeleton. Overall, the comparative frequencies were nearly a perfect 2 : 1 ratio, i.e., 0.80% in females and 0.38% in males, significantly different from a 1 : 1 ratio by any reasonable test of significance. Of the 133 triquetral-lunate fusions observed, 86 were registered in the Black females alone. Since the Ten-State Nutrition Survey emphasized family-line participation, whenever possible, the extent of parent-child and sibling concordance with respect to the 0s lunatotriquetrum could be determined. In 42 parents of affected subjects, the trait was observed in 5%. Among 65 children of adult propositi, triquetral-lunate fusion was present in 3% . Among 177 siblings of index cases, using only one such index case per lineage, the frequency of fusion