Carpal Fusions in Children of Four South African Populations ERROL L E V I N E D e p a r t m e n t of Dingnostic Rndiology a n d D e p a r t m e n t of A?iritomy, U ? ~ i u r r s i tof y the W i t w a t e r s r a n d , J o h a n n e s b u r g , Soutlz Africri KEY WORDS Carpal fusions . Hand-wrist X-rays . Children . South Africa . Genetic differences among populations. ABSTRACT The incidence of carpal fusions was determined from radiographs of both hands of 2,250 Pretoria schoolchildren aged 72 to 191 months. The group included White, Negro, Coloured and Indian subjects. Of the many possible varieties of carpal fusion, only lunato-triquetral fusion and capitate-hamate fusion were encountered. No examples of lunato-triquetral fusion were encountered i n children less than ten years of age. I n Pretoria Negroes aged 10 to 15 years, the incidence of lunato-triquetral synostosis is 4.5796, while Pretoria Coloureds show a n incidence of 1.51 % . This type of fusion was not noted i n the White or Indian populations. Two examples of capitate-hamate synostosis were encountered i n Pretoria Negroes. The available evidence suggests that these two varieties of carpal fusion may be added to the list of discrete traits varying in frequency from population to population and probably reflecting different underlying gene frequencies. No significant sex difference in incidence of lunato-triquetral fusion was noted in the present study. Lunato-triquetral fusion is about twice as commonly bilateral as unilateral i n occurrence. By carpal fusion is meant the cohesion of two or more normally adjacent, but separate elements of the carpus. Fusions have been encountered in almost every possible combination in the carpus and the recorded varieties of fusion have been reviewed by O’Rahilly (‘53, ’57). The present study has been carried out with the objective of determining the nature and incidence of carpal synostoses in children belonging to the four main population groups of South Africa. M A T E R I A L S AND M E T H O D S During the years 1962 to 1965, the National Nutrition Research Institute of the Council for Scientific and Industrial Research (CSIR) carried out an extensive cross-sectional nutritional status survey on the school children of Pretoria. The survey included the four main population groups of the Republic of South Africa namely, Southern African Bantu-speaking Negroes, Whites (Caucasoids of European extraction), Indians or Asians (descendants of immigrants from India), and ColAM. J. PHYS.ANTHROP.,37: 75-84. oureds (persons of mixed extraction). Anthropometric, clinical, biochemical, haematological, dietetic, radiological and socio-economic data were collected for a total of 2,250 children aged six to fifteen years. The statistical planning of the survey has been described by Fellingham (‘66). Radiographs of both hands of 2,250 Pretoria children were used in the present study. The children included 808 Whites (413 males, 395 females), 585 Negroes (288 males, 297 females), 450 Coloureds (225 males, 225 females), 407 Indians (202 males, 205 females). They ranged in age from 72 to 191 months. The children were grouped according to age, sex and population group and the frequency of carpal fusions in each group was determined. Skeletal age determinations were made by means of the GreulichI This paper is based on part of a thesis submitted for the degree of Doctor of Philosophy at the University of the Witwatersrand i n 1969. The study was supported i n part by the National Nutrition Research Institute of the Council for Scieiitific and Industrial Research, Pretoria, South Africa. 75 76 ERROL LEVINE Fig. 1 Early stage of lunato-triquetral fusion i n a Negro m a l e aged 161 months. There elongation of the triquetral a n d the two bones a r e i n close apposition. IS Pyle Radiographic Atlas of the Skeletal Development of the Hand and Wrist ('59). 1. Lunato-triqzietral fusion in Pretoria children FINDINGS I n all, 22 Pretoria children showed the presence of lunato-triquetral fusion in either one or both wrists. Serial radiographic studies by other workers (Silverman, '55; Dean and Jones, '59; Hughes and Tanner, '66) have shown Only two varieties of carpal fusion have been detected in the present study, namel y fusion of the lunate and triquetral and fusion of the capitate and hamate. CARPAL FUSIONS I N SOUTH AFRICAN C H I L D R E N 77 Fig. 2 Lunato-triquetral fusion in a Negro male aged 138 months. There is a line of increased density at the site offusion of the two centres. that fusion of the two centres progresses with increasing age. Figure 1 shows a n early stage of lunato-triquetral synostosis in a Pretoria Negro male aged 161 months. There is close apposition of the adjacent surfaces of the two centres and the radiological appearance resembles that of a pseudarthrosis. Figure 2 shows a somewhat later stage of fusion with a dense line at the site of junction of the two centres in another child. Figure 3 shows complete synostosis of the two centres in a Negro female. The incidence of fusion i n the different population groups is shown i n table 1. As no example was encountered under ten years of age, the incidence has been determined for children aged 10 to 15 years. Fusion was noted in 4.57% of Negro children and i n 1.51% of Coloured 78 ERROL LEVINE Fig. 3 Complete lunato-triquetral fusion in a Negro female aged 133 months children. No examples of fusion were encountered in the White or Indian groups. Negro and White children differ significantly i n incidence of lunato-triquetral fusion, in that the observed differences between the percentage incidences in the two groups exceeds three times the standard error of the difference. No significant difference in incidence of this variant exists between Coloured and White children and Negro and Coloured children. Hence, on the basis of the data, it may 79 CARPAL FUSIONS IN SOUTH AFRICAN CHILDREN TABLE 1 Incidence of liinato-triquetral f u s i o n in Pretoria children aged 10 to 15 gears Population group Total number Individuals with fusion (male and female) Of White Negro Coloured Indian children No. % 445 394 265 240 0 18 4 0 0.00 4.57 1.51 0.00 Total number of inales Males with No. % Total number of females 0 7 1 0 0.00 3.48 0.75 0.00 219 193 132 120 fusion 226 201 133 120 Females with fusion No. 5 0 11 3 0 0.00 5.70 2.27 0.00 TABLE 2 The frequency of unilatercil a n d bilateral lirnnto-triquetral fusioii in Pretoria Negro a n d Colorired children Negro Laterality of lunatotriquetral fusion NO. Coloured cc Total No 7% No % ~~ Bilateral fusion Unilateral fusion 13 72.2 2 50.0 15 68.2 Right carpus Left carpus 3 2 16.7 11.1 2 0 50.0 0.0 5 2 22.7 9.1 Total 5 27.8 2 50.0 7 31.8 be concluded that Negro children manifest the 0s lunato-triquetrum significantly more frequently than White children. The data in table 1 suggest that lunatotriquetral fusion is more common in Negro and Coloured females than in Negro and Coloured males. However, in both Pretoria Negroes and Coloureds the sex difference in incidence of the variant is not significant, the observed difference between the percentages in each instance being less than three times the standard error of the difference. The number of cases in the present study is clearly too small to pennit any conclusion regarding the significance of the observed sex difference in the incidence of fusion. Table 2 shows the frequency of unilateral and bilateral distribution of the 0 s lunato-triquetrum in Pretoria children. In 15 of the 22 children with this variant (68.2%), fusion was present in both wrists. In seven children (31.8%) fusion occurred on one side only. In five of the seven instances of unilateral occurrence, fusion was on the right and in two instances it was on the left side. Because of the small size of the sample, these data were not subjected to statistical analysis. Furthermore, the incidence of bilateral occurrence of lunato-triquetral synostosis in this series of children may, in fact, be higher. Some children with unilateral fusion at the time the radiographs were taken may subsequently have developed fusion in the opposite carpus. However, the available data suggest that fusion is about twice as commonly bilateral as unilateral. The data in the present study show a general trend for synostosis of the two ossific centres to commence in the circumpubertal period. No instances of fusion were detected in children between six and nine years of age. The median skeletal age of the 22 children exhibiting fusion is 154 months, the range being 87 to 204 months. The median chronological age of the 22 children is 167 months with a range of 126 to 191 months. 2. Fusion of the capitate and hnmate in Pretoria children Fusion of the capitate and hamate is less common than fusion of the lunate and triquetral. In the present study two examples of bilateral capitate-hamate fusion were encountered in 585 Negro children -an incidence of 0.34%. This variety of fusion was not detected in the White, Coloured or Indian population groups. Figure 4 shows partial fusion of the 80 ERROL LEVINE Fig. 4 Partial capitate-hamate fusion in a Negro female aged 189 months. There is complete fusion of the lunate and triquetral capitate and hamate in a Negro female aged 189 months. The fusion is bilateral and the child has, in addition, bilateral lunato-triquetral synostosis. The other example of fusion was noted in a Negro female aged 133 months. The fusion i n this iiistance is likewise bilateral and incomplete. DISCUSSION Carpal fusions may occur as isolated anatomical variants or they may be associated with generalised skeletal disorders (Poznanski and Holt, ’71). Generally the isolated carpal fusions involve bones in the same row, while the syndrome-associated fusions not infrequently involve co- hesion of adjacent carpals in the proximal and distal rows (Poznanski and Holt, ’71). It is considered that the term “fusion” applied to the isolated anatomical variant is a misnomer (O’Rahilly, ’57; Cockshott, ’59). According to O’Rahilly (’57), the first step i n the development of carpal fusions is either failure of separation of adjacent cartilages in the embryo or possibly fusion of cartilaginous anlagen at an early stage in embryonic development. Ossification begins from two centres in a single cartilaginous primordium. The existence of a single cartilage, where usually there are two, then inevitably leads to the subsequent fusion of the two ossific centres concerned. Thus the variant may be regarded not as a “fusion,” but rather 81 CARPAL FUSIONS IN SOUTH AFRICAN CHILDREN TABLE 3 The incidence of the 0s lu n a t o - t r i q u m x m zn dzflerext populations Individuals with fusion Population Size of series Negroid West African Negroes Baganda Baganda Wadigo Yoruba American Negroes South African Negroes Caucasoid Scandinavian Whites German Whites American Whites American Whites South African Indians South African Whites No. % 3 40 5 3.75 5.88 2.12 Dean and Jones ('59) 24 14 74 6.67 1.03 8.01 Davies ('59) Mackay ('52) Cockshott ('59) 7543 subjects 119 1.58 Garn et al. ('71) 394 children 18 4.57 Present study 2100 adults 5000 subjects 743 subjects 11663 subjects 3 4 12 0.14 0.08 0.13 0.10 Lonnerblad ('36) Arens ('50) ORahilly ('53) Garn et al. ('71) 240 children 0 0.00 Present study 445 children 0 0.00 Present study 80 children 680 adults 236 children 360 children and adults 1360 children 923 adults as a non-separation of cartilaginous carpals. There is evidence to suggest a genetic basis for certain types of carpal synostosis. There is now abundant evidence that lunato-triquetral fusion may be regarded as a familial trait (Dean and Jones, '59; Garn et al., '71). Cockshott ('59) has encountered capitate-hamate fusion in identical twins. Carpal fusions are frequently associated with hereditary skeletal disorders including symphalangism (Harle and Stevenson, '67; Geelhoed et al., '69), the Ellis-van Creveld syndrome (McKusick, '66) and the hand-foot-uterus syndrome (Poznanski et al., '70; Stern et al., '70). Certain types of carpal fusion vary in incidence from population to population. Lunato-triquetral synostosis is apparently rare in Mongoloid peoples. Only one example was found in 1,400 Japanese children, an incidence of 0.071 % (Wetherington, '61). The present study and other studies have shown that lunato-triquetral fusion is undoubtedly more common in Negroid than in Caucasoid subjects (table 3). The observed frequency in the African Negro is higher than that in the American Negro. The writer has been unable to find any record of lunato-trique- 1 Authors Smitham ('48) tral fusion in Indian subjects. No example of fusion was encountered in Pretoria Indian children. In Pretoria Coloureds, the incidence of lunato-triquetral synostcsis is higher than in Whites, but lower than in Negroes. Since the Coloureds include a fairly high incidence of Negroid genes, and the Indians are Caucasoid, the findings in the present study may be interpreted as suggesting strongly that lunato-triquetral fusion is genetically determined with a higher frequency of allele(s) in Negroid than in Caucasoid subjects. Capitate-hamate fusion also appears to be more common in Negroid than in Caucasoid subjects. It is the second most common variety of carpal synostosis in the African Negro (Smitham, '48; Beresowski and Lundie, '52; Mackay, '52; Dean and Jones, '59; Cockshott, '59). Capitatehamate fusion appears to be rare in White subjects. Isolated instances in Whites have been mentioned in the literature (White, '44), but Kohler ('56), in his radiological text, does not mention having encountered an example. It seems appropriate that these two varieties of carpal fusion should be added to the list of discrete traits differing in incidence from population to population 82 ERROL LEVINE and probably reflecting different underlying gene frequencies. In the present study, lunato-triquetral synostosis appears to be more common in females, while in the Yorubas of Nigeria (Cockshott, '59) and i n West African Negroes (Smitham, '48), there is a tendency for the variant to be more common in males. However, in none of the groups is the sex difference statistically significant. Of 119 instances of fusion encountered in 7,543 American Negroes, 86 instances occurred i n females (Garn et al., '71). A female preponderance for the trait in American Negroes thus seems firmly established. Very little information is available regarding the relative frequency of unilateral and bilateral lunato-triquetral fusion. This is because in some studies only one wrist has been X-rayed. Even when both wrists have been X-rayed, authors sometimes have not documented whether fusion was unilateral or bilateral. The finding in the present study that fusion is about twice as commonly bilateral as unilateral is confirmed by other studies. Of his 74 cases, Cockshott ('59) found bilateral fusion in 47 (63.5%), right-sided fusion in 12 (16.2%) and left-sided fusion i n 15 (20.3%). In all five cases of Gean and Jones ('59) synostosis was bilateral. Smitha m ('48) found that the variant was most frequently bilateral, but when unilateral, it occurred only i n the right carpus in his Negro subjects. Very few data dealing with the age at which fusion of the lunate and triquetral ossific centres occurs have been published. Table 3 indicates that the maximuin incidence of synostosis is found in adult Negroes. In the present study no example of fusion was encountered below ten years of age and a general trend was noted for synostosis to become apparent in the circumpubertal period. However, it seems that the chronological age at which fusion first becomes evident radiologically is variable. Examples of fusion have been noted at 102 months in a Japanese boy (Wetherington, '61), and at six years in a Yoruba girl (Cockshott, '59). Since synostosis is progressive with the maturation of the wrist (Silverman, '55; Dean and Jones, '59; Hughes and Tanner, '66), i t would seem likely that the onset of fusion may correlate better with skeletal age than with chronological age. ACKNOWLEDGMENTS I wish to thank Professor Phillip V. Tobias, Head of the Anatomy Department, University of the Witwatersrand, for his considerable help in the production of this paper; Dr. J. J. Theron, former Director of the National Nutrition Research Institute, Pretoria, and Dr. J. F. Potgieter, former Head of the Field Studies Division of the National Nutrition Research Institute, for allowing me freely to study their collection of radiographs. LITERATURE CITED Arens, W. 1950 Uber die angeborene synostose zwischen dem 0 s lunatum und dem 0 s triquetrum. Fortschr. Rontgenstr., 73: 772 (quoted by O'Rahilly, 1953). Beresowski, A., and J. K. Lundie 1952 Sequence in the time of ossification of the carpal bones in 705 African children from birth to 6 years of age. S. Afr. J. Med. Sci., 1 7 : 25-31. Cockshott, W. P. 1959 Carpal anomalies amongst Yorubas. W. Afr. Med. J.,8: 1 8 5 1 9 0 . Davies, A . G . M. 1959 Unpublished data quoted by Cockshott, 1959. Dean, R. F. A., and P. R. M. 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