Determination of Crown-Rump Length from Fetal Long Bones: Humerus and Femur LALIT MEHTA AND H. M. SINGH D e p n r t m e n t of A n a t o m y , R. N . T . M e d i c n l College, U d a i p u r , Indici KEY WORDS Fetus . CR Length . Humerus Diaphysis . Age. . Femur . Growth . ABSTRACT Lengths of the ossified diaphysis of the humerus and femur were measured in 50 fetuses ranging from 65 to 290 mm Crown-Rump length. A significant correlation was found between the diaphyseal length and the CR length. No appreciable difference was noted in diaphyseal lengths of the humerus and femur i n fetuses of 85 mm CR length or below. Various growth phases were observed. The difference i n length of the femur and humerus is due to a comparative slow growth of the humerus during the later period of prenatal life. Diaphyseal growth rates of the humerus and femur are 0.18 mm and 0.21 m m respectively for every 1 mm increase in CR length. Regression coefficients for the lengths of the ossified shaft of the humerus and femur are 5.35 and 5.00 respectively. With the help of these coefficients, CR length of the fetus was estimated within a range of k 1 5 mm. From the estimated CR length, age of the fetus was determined with the help of a standard age and size curve with reasonable accuracy. Study of the correlation between linear growth of long bones and the CR (CrownRump) length of the fetus assumes importance in medicolegal practice, since the correlation can be used to estimate the age of the fetus from its available long bones. Growth of long bones during prenatal life has been studied in detail (Nishizuka, '26; Streeter, '49; Felts, '54). Radiographic studies on the prenatal ossification of human long bones recording the ratio of the lengths of the ossified shaft relative to the corresponding CR length have been undertaken (Bade, '00; Halonen, '29; ORahilly and Meyer, '56). Various phases of linear growth of long bones have been reported (Depreux and Fontaine, '51 ; Moss et al., '55) and a linear correlation between diaphyseal length and fetal height has been observed (Smith, '39; Saettle, '51; Olivier and Pineau, '60). Recently, Gray and Gardner ('69) and Gardner and Gray ('70) in their reports on the prenatal development of the humerus and femur published tables showing the lengths of the ossified shaft and the corresponding CR length in fetal specimens of 37 to 342 mm CR length. AM, J . PHYS. ANTHROP.. 36: 165-168. In the present study the lengths of the ossified diaphysis of the humerus and femur were measured in fetal specimens of 65 to 290 mm CR length and a formula derived to estimate the age of the fetus based on the correlation of the diaphyseal growth with the CR length. MATERIALS AND METHODS We studied 50 apparently normal fetuses, 30 male and 20 female, delivered by normal women and having a CR length ranging from 65 to 290 mm. The CR length was measured, after fixation of fetuses i n 10% formaline for four to six months, with a specially prepared osteometric board to the exactness of 1 mm. Values were verified by recording several times. The limbs were detached and placed in 5% KOH solution at room temperature for about two weeks. After thorough washing in running tap water, the humerus and femur were dissected out and cleaned. The cartilaginous ends were removed gently. The remaining ossified part of the shaft of each bone was dried at room temperature for 48 hours. The maximum length of the ossified shaft of 165 166 LALIT MEHTA AND H. M. SINGH TABLE 1 M e m i length oftlie oss$ed shaft of the Izumenis c c n d f e m u r for fetuses grouped by C R leitgth Lengths of the ossified shaft CR length No. of fetuses Humerus 11LnZ ?nm 2 3 2 2 3 3 2 2 5 4 2 6 4 3 3 2 2 11.5 16.0 18.0 20.7 21.5 26.5 26.7 26.7 29.1 29.5 33.5 35.3 37.8 38.8 43.3 48.5 51.5 11.5 16.0 19.0 21.5 22.5 27.0 28.0 28.0 30.4 31.2 34.5 37.5 40.5 41.5 47.3 52.2 59.0 iiinz 65 85 95 120 125 135 145 150 155 160 170 180 190 200 230 245 290 Femur each bone was measured with a sliding gauge. In order to exclude a possible crossed asymmetry, only the right bones were measured. The exactness of measuring was within 0.25 mm. Personal error was eliminated by random controls measured by a second person. The fetal specimens were grouped by CR length to the nearest 5 mm and the length of the ossified shaft of each was recorded. OBSERVATIONS AND RESULTS The CR length of fetuses in different groups and the corresponding lengths of the ossified shaft of the humerus and the femur are recorded in table 1. No appreciable difference occurs in the diaphyseal length of the humerus and femur i n fetuses of CR length 8 5 m m or below. The ossified diaphyseal length of both humerus and femur are plotted against CR length in figure 1. The correlation coefficient (r) is 0.9893 for the humerus and 0.9956 for the femur. The growth in length of both bones was rapid and regular in fetuses with CR length up to 99 mrn followed by a phase of slow growth lasting up to 150 m m CR length. Thereafter again there was a phase of regular growth in both bones up to 245 mm CR length. This was followed by a phase of slow 60 100 i40 f80 ,220 CROWN-RUMP LENGTH 260 300 IN mm. 1 Curve showing the growth of the ossified diaphyses of the humerus and femur and their correlation with the CR length growth, especially in the humerus. The difference in the diaphyseal lengths of the humerus and femur became greater during the later period of prenatal life. The diaphyseal growth, as observed graphically, was 0.18 m m and 0.21 mm for the humerus and femur respectively for every 1 mm increase in CR length. Regression formulae were used to find the regression coefficients for estimating the CR length from the measured length of the ossified diaphysis of the humerus and femur: Y (CR Y (CR & * 15 mm) = 5.35 x humerus 15 mm) = 5.00 X femur DISCUSSION As only the ossified portions of the bones are usually available for determination of age, only the length of the ossified portion of the diaphysis was studied. These lengths of the humerus and femur were equal in specimens of 85 m m or less CR length. Depreux and Fontaine ('51) recorded slow growth in both the bones of fetuses of four to six months, but in the present study such a slow growth phase was found during four to six months only. The lengths of the humerus and femur increased regularly from the fifth month onwards. However, the growth of AGE DETERMINATION OF FETUS FROM LONG BONES the humerus during this period was slow compared to the femur, resulting in the marked difference in length of both the bones a t the time of birth. Bade (‘00) found no correlation of growth in length of long bones with the body length, but Olivier and Pineau (‘60) showed linear correlation between the diaphyseal lengths and the fetal height. A similar correlation was observed in the present study between the lengths of the ossified shafts of the humerus and the CR length. Felts’ (‘54) observation that the length of the femur increased by 0.21 mm for every 1 m m increase in CR length was confirmed by the present study. Gardner and Gray (‘70) reported a n increase of 0.285 mm in the shaft of the femur for every 1 mm increase in CR length. Saettle (‘51), in his studies on determination of size of the human fetus based on linear measurements of bones, plotted growth curves of shafts against fetal height and reported that estimation of height on the basis of the growth curve is more accurate. A similar curve was obtained in the present study for the growth of the ossified shaft of the humerus and femur against the CR length. Scammon’s (‘37) nomogram showing maximum dried length of the femur i n fetuses of 180 to 375 mm CR length gives lower values when compared with those obtained in the present study. Due to different growth phases, a definite multiplying factor for a given diaphyseal length to estimate the exact CR length is difficult to derive. Smith (’39) reported multiplying factors of 7.60 and 6.71 for the diaphyseal lengths of the humerus and femur respectively to estimate the Crown-Heel (CH) length of the fetus. In the present study multiplying factors were derived to find the CR length. The values (5.35 and 5.00 for humerus and femur respectively) are a little higher than those of Smith’s observations after converting the values for CH length determination (CR:CH ratio taken as 1:1.45). The regression line of femur length on CR length is similar to but slightly lower than that found by Stewart (‘54) after maximum drying in the range for which they can be compared, 40-59 mm. Once the Crown-Rump length is estimated from the lengths of the ossified shaft of the humerus or femur, the age 167 of the fetus can be estimated with a reasonable accuracy from a standard age and size curve such as that published by Boyd (’41). ACKNOWLEDGMENTS We are thankful to Dr. R. P. Chaturvedi, Principal and Professor of Anatomy, R.N.T. Medical College, Udaipur, for permission to carry out this study and for his guidance. We are also thankful to Dr. K. C. Jain for his help and to Mr. D. K. Shrivastava for the statistical calculations. LITERATURE CITED Bade, P. 1900 Die Entwicklung des menschlichen skelets bis zur Geburt. Arch. mikr. Anat. Entw., 55: 245-290. Boyd, E. 1941 Outline of Physical Growth and Development. Burgess, Minneapolis. Depreux, R., and R. Fontaine 1951 Pousses et crises de croissance de l’humerus et du femur foetaux. Etude Bull. SOC.Anthrop., 2: 182-188. Felts, W. J. L. 1954 The prenatal development of the human femur. Am. J. Anat., 9: 1 4 4 , Gardner, E., and D. J. Gray 1970 The prenatal development of the human femur. Am. J. Anat., 129: 121-140. Gray, D. J., and E. Gardner 1969 The prenatal development of the human humerus. Am. J. Anat., 124: 431-446. Halonen, L. 1929 Rontgenlogisch-Anatomische Untersuchungen uber die Entwicklung der Knochen der freien Extremiteten beim Menschen. I . Die extremitenknochen der Feten. Acta Societatis Medicorum Fennicae “Doudecim.” Sounalaisen Laakariseur a n Duodecim ’in Toimituksia, Tom XI, Fase. 3 : 1-151, Helsinki. Moss, M. L., C. R. Noback and G. G. Robertson 1955 Critical developmental horizons i n hum a n fetal long bones. Am. J. Anat., 97: 155175. Nishizuka, T. 1926 Beitrage zur Osteologie der Foten, Neugeborenen, und Kinder nebst Erwachsenen (Japoner). Knochen der Extremitaten samt Schulter und Backen. 2. Morph. Anthr., 25: 1-90, Olivier, G., a n d H. Pineau 1960 Noubelle determination de la tailla foetale d’apres les longures diaphysaires des 0s longs. Ann. Med. Leg., 40:2 141-144. ORahilly, R., and D. B. Meyer 1956 Roentgenographic investigation of the h u m a n skeleton during early fetal life. Am. J. Roentgen., 76: 4 5 5 4 6 8 . Saettle, R. 1951 Korpergroszenbestimmung menschlicher Fruchte and Hand der Langemasze einzelner Skeletteile oder der en Dia- 168 LALIT MEHTA AND H. M. SINGH physen. Dtsch. Z . Ges. gerichtl. Med., 40: 567577. Scammon, R. E. 1937 Two simple nomographs for estimating t h e age and some of the major external dimensions of the h u m a n fetus. Anat. Rec., 68: 221-225. Smith, S. 1939 Quoted by W. M. Krogman. In: The Human Skeleton i n Forensic Medicine. Charles C Thomas, Springfield, 1962, p. 177. Stewart, T. D. 1954 Evaluation of evidence from the skeleton. In: Legal Medicine. Chap. 17. R. B. H. Gradwohl, ed. C. V. Mosby Co., St. Louis, pp. 420-421. Streeter, G. L. 1949 Developmental horizons i n h u m a n embryos (fourth issue). A review of the histogenesis of cartilage a n d bone. Contrib. Embryol., 33. 149-167. Publication No. 583, Carnegie Institution of Washington.