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Clinical Anatomy 14:254 –257 (2001) Intercondylar Shelf Angle in Adult Black Malawian Subjects P.S. IGBIGBI,* B.C. MSAMATI, AND T.M. NG’AMBI Department of Anatomy, College of Medicine, University of Malawi, Blantyre 3, Malawi In this study, we determined the intercondylar shelf angle of the femur in adult black Malawian subjects as measured in lateral radiographs of the knee joint. A total of 856 radiographs were used: 464 from men and 392 from women, aged 18 –70 years. A goniometer measured the intercondylar shelf angle at the intersection between Blumensaat’s line and a line drawn along the edge of the distal third of the femur parallel to the posterior cortex of the bone. The mean intercondylar shelf angle of 136.60° ⫾ 5.90° in Malawians of both sexes was significantly different from 142.57° ⫾ 5.86° for American subjects (P ⬍ 0.001), as given by Craig (1995, J. Forensic Sci. 40:777–782), but the level of statistical significance between black Malawian females and black American females was at P ⬍ 0.01. Using the intercondylar shelf angle, 66.67% of male Malawians were correctly identified as such and 50.00% of Malawians females as such. Eighty-three percent of males and 81.30% of females were correctly identified as blacks. This angle has been shown to exhibit sexual dimorphism in Malawian subjects. Its importance in forensic anthropology is stressed. Clin. Anat. 14:254 –257, 2001. © 2001 Wiley-Liss, Inc. Key words: human knee; femur; racial variation; forensic anthropology INTRODUCTION Different methods exist for analyzing and describing human variation, but few of these utilize the femur to differentiate race (Stewart, 1962; Lavelle, 1973; Farrally and Moore, 1975; Gilbert, 1976; Craig, 1995). Still fewer methods use metric analysis of the intercondylar notch to distinguish race (Baker et al., 1990). The intercondylar notch of the femur is U-shaped, lies at the distal end of the femur, and separates two large oblong condyles that project posteriorly (Moore, 1992). The intercondylar shelf is a line of dense cortical bone that forms the “roof” of the intercondylar notch. This area is best seen in a sagittal section of the femur and it is represented as a relatively radiopaque line in a lateral radiograph of the knee (Fig. 1). Blumensaat (1938) first described the line and it is now named for him; it marks the normal position of the patella if the knee is flexed at 30° (Carson et al., 1984). The intercondylar shelf angle is the angle formed at the intersection of Blumensaat’s line and a line drawn parallel to the posterior cortex of the femur (Fig. 2). This angle shows a relatively consistent and statistically significant difference between American whites and blacks (Craig, 1995). © 2001 Wiley-Liss, Inc. In a study using skeletal samples, Baker et al. (1990) showed differences in height of the intercondylar notch between whites and blacks. This difference was shown to affect the intercondylar shelf angle in such a way that the more acute the angle was, the higher the notch, whereas a more obtuse angle indicated a lower notch (Craig, 1995). These investigators have further demonstrated that this angle exhibits racial variation, and hence its importance. The angle is easily measured and its variation is independent of the size of the femur, of the effect of arthritis in the notch, or of trauma to the articular surface. Moreover, the method is noninvasive, and can be applied to both skeletal material and to femora with intact soft tissue. The angle can be measured in fragmented femora, and only a single measurement is necessary (Craig, 1995). Despite the importance of this angle in forensic anthropology, there are few published reports, and they refer only to American whites and blacks. There *Correspondence to: P.S. Igbigbi, Department of Anatomy, College of Medicine, University of Malawi, Private Bag 360 Chichiri, Blantyre 3, Malawi. E-mail: [email protected] Received 15 September 1999; Revised 6 December 1999 Intercondylar Shelf Angle in Malawians 255 Fig. 1. Roentgenogram indicating the radiopaque roof of the intercondylar notch. Fig. 2. Roentgenogram illustrating the intercondylar shelf angle (A). B, Blumensaat’s line; P, A line drawn parallel to the edge of the cortex of the posterior distal third of femur. are no reports on the angle in Malawians, nor, indeed, in other African subjects. This study therefore provides baseline data for indigenous adult black subjects. These data will be useful in forensic anthropology because Malawi has both black and white people in its population. faced left, thereby reducing technical errors that occur if the femur is not properly positioned. To position the femur properly, the anterior aspect of the knee must face left with the medial condyle facing upwards, away from the table, and then a true lateral view will be closely approximated. In this position, the knee is normally placed at 30° (Lusted and Keats, 1978). Only radiographs that met these conditions were measured. A metal ruler was aligned with one edge against the distal one-third of the femur parallel to the posterior cortex of the bone, and a line was drawn along the opposite edge of the ruler. The ruler was then placed so that one edge went through Blumensaat’s line in a “best-fit” alignment. A second line was then drawn along the edge. Blumensaat’s line is the line drawn along the dome of the intercondylar fossa, and an extension of this line anteriorly meets the inferior pole of the patella (Fig. 2), provided the knee is flexed at 30°. A goniometer was placed over the intersection of these two lines and the interior angle was measured (Fig. 2). MATERIALS AND METHODS Lateral radiographs of 856 individuals (464 men and 392 women aged 18 –70 years) were examined. The radiographs were collected from hospitals in all three regions of the country: Queen Elizabeth, Lilongwe, and Zomba Central Hospitals and Mzimba, Rumphi, and Mchinji district hospitals. All the radiographs used were known to belong to indigenous black Malawians. Either the left or right knee was used to measure the intercondylar shelf angle from each roentgenogram. Each radiograph was placed on a light box and positioned so that the anterior aspect of the knee 256 Igbigbi et al. TABLE 1. Characteristics of Intercondylar Shelf Angle in Adult Black Malawians Intercondylar shelf angle (degrees) Range Mean and SD Men (n ⫽ 464) Women (n ⫽ 392) Both (n ⫽ 856) 130–143 135.09 ⫾ 4.81 125–153 138.68 ⫾ 6.82 125–153 136.60 ⫾ 5.90 TABLE 2. Means and SD of Intercondylar Shelf Angle (Degrees) by Race and Sex TABLE 3. Comparison of Intercondylar Shelf Angles in Various Groups of American and Malawian Subjects All by race Comparison between American blacksa American whitesa Black Malawiansb n 183 240 856 Mean 137.83 146.18 136.60 SD 4.18 4.29 5.90 All by sex American womena American mena Black Malawian womenb Black Malawian menb 188 235 392 464 142.59 142.55 138.68 135.09 6.31 5.61 6.82 4.81 Women by race Black American womena White American womena Black Malawian womenb 80 108 392 137.16 146.60 138.68 4.14 4.31 6.82 Men by race Black American mena White American mena Black Malawian menb 103 132 464 138.35 145.83 135.09 4.16 4.25 4.81 Malawian men and women American whites and blacks American blacks and Malawian blacks American whites and Malawian blacks American women and American men American women and black Malawian women American men and black Malawian men Black American women and white American women Black Malawian women and black American women Black American men and white American men Black American men and Black Malawian men White American men and Black Malawian men t values P values 8.73 20.00 3.32 25.89 0.07 7.52 ⬍0.001 ⬍0.001 ⬍0.001 ⬍0.001 nsa ⬍0.001 17.34 15.53 ⬍0.001 ⬍0.001 2.62 ⬍0.01 13.60 ⬍0.001 6.64 ⬍0.001 24.98 ⬍0.001 a a Source, Craig (1995). b Source, present study. A repeatability study was conducted in which the three authors independently marked and measured the angle on 50 radiographs, using the method described above. Each author measured each angle twice to ensure accuracy. The intercondylar shelf angle thus measured was recorded together with the name, age, and sex of the subject. The lines were erased from the radiographs between each of the three author’s measurements. We tested for interobserver error and the variation among them averaged less than 1°. Each radiograph was classified by sex and race using Craig’s (1995) method. Those with an intercondylar angle of 137° or greater were classified as female whereas those with an angle less than 137° were classified as male. Individuals with an angle of 142° or greater were classified as white and those with an angle of 141° or less were classified as black. All results were analyzed using the SAS statistical package for Windows 6.08 and are presented in Tables 1–3. RESULTS Table 1 shows the characteristics of the intercondylar shelf angle in the sample. The means and stan- ns, not significant dard deviations (SD) of intercondylar shelf angles by race and sex of the subjects are presented in Table 2 and are compared with results from Craig (1995) in Table 3. Malawian women have a significantly higher intercondylar shelf angle than Malawian men (P ⬍ 0.001) (Table 3). Table 3 also shows that most of the parameters were highly significantly different (P ⬍ 0.001) and significantly different between black Malawian and black American women (P ⬍ 0.01). There was, however, no significant difference between the angles in American men and women (P ⬎ 0.5). The results also revealed that the sex of 66.67% (n ⫽ 309) of the men and 50.00% (n ⫽ 196) of the women was correctly identified. About 83% (82.50%, n ⫽ 706) of the entire sample were correctly classified as black; and of these 706 individuals, 83.30% (n ⫽ 387) were correctly identified as men and 81.30% (n ⫽ 319) were correctly identified as women. DISCUSSION We have shown that the intercondylar shelf angles vary between men and women in this Malawian sample, being significantly greater in women. This is at variance with American subjects, who showed no significant difference between men and women (P ⬎ 0.5) Intercondylar Shelf Angle in Malawians (Craig, 1995). The lower limb angles represented by femoral neck-shaft and anatomic angles do exhibit sexual dimorphism (Igbigbi and Kwatampora, 1997), but the angles previously reported were normally larger in men than in women. The differences between the American series and ours might arise from environmental and dietary factors. It has also been shown that intercondylar shelf angles vary between races. In a study on American whites and blacks, Craig (1995) introduced a new method to determine race from measuring intercondylar shelf angles. He showed that it was relatively easy to do once the landmarks had been located and marked, that it could be used for fragmented femora, and that it gave reproducible results. Furthermore, the angle is not affected by arthritis, articular trauma or by size, length, or overall curvature of the femur (Craig, 1995). Previous studies have shown that the femora of blacks are generally longer and have less anterior curvature than those of whites (Trotter and Gleser, 1952; Stewart, 1962). Whites have more anterior bowing than blacks but this has not been found to affect the measurement of the intercondylar shelf angle (Craig, 1995). If the curvature of the femur were to be included in the intercondylar shelf angle analysis, it would further increase the differences between the races. Craig (1995) argued that this is because a more anterior bow, typical of whites, will create a more acute angle whereas in blacks with less anterior bowing, the angle will be more obtuse. The method employed here was based on the measurement of lateral radiographs of the knees of living subjects. In a clinical situation, the leg and knee can be positioned in such a way as to control rotation of the entire limb and a “true lateral” radiograph can be taken; the position of Blumensaat’s line will be consistently correct (Craig, 1995) and the method can be applied. The only problem with this method is with individuals whose intercondylar shelf angles are close to or overlap the watersheds of 137° for sex and 141– 142° for race. This problem, however, is a familiar one in forensic identification (Craig, 1995). Nevertheless, measurements of the intercondylar shelf angle were used to determine sex and race in the present study. We have demonstrated that the method gives a higher 257 determination of race than of sex. This finding confirms the reports on whites and blacks (Trotter and Gleser, 1952; Stewart, 1962; Craig, 1995). Its usefulness in forensic anthropology cannot be underestimated especially in mixed societies and populations. We recommend this method for determining race in mixed populations. Its usefulness is unquestionable in poor developing countries like Malawi where forensic anthropology is lacking or is a luxury. Since mixed societies have become an important ingredient of population dynamics in Africa, the method would indeed be invaluable for medico-legal cases in Africa and other developing countries. REFERENCES Baker SL, Gill GW, Kiefer DA. 1990. Race and sex determination from the intercondylar notch of the distal femur. In: Skeletal attributions of race. Albuquerque, NM: Maxwell Museum of Anthropology. Blumensaat C. 1938. Die lageabweichungen und verrenkungen der kniescheibe. Ergebnisse der chirurgie und orthopadie 31:149 –223. Carson WG Jr., James SL, Larson RL, Singer KM, Winternitz WW. 1984. Patellofemoral disorders: physical and radiographic evaluation. Part II: radiographic examination. Clin Orthop Rel Res 185:178 –186. Craig EA. 1995. Intercondylar shelf angle. A new method to determine race from the distal femur. J Forensic Sci 40:777– 782. Farrally MR, Moore WJ. 1975. Anatomical differences in the femur and tibia between Negroids and Caucasoids and their effects upon locomotion. Am J Phys Anthrop 43:63– 69. Gilbert BM. 1976. Anterior femoral curvature: its probable basis and utility as a criterion of racial assessment. Am J Phys Anthrop 45:601– 604. Igbigbi PS, Kwatampora J. 1997. Lower limb angles of East Africa subjects. West Afr J Anat 5:9 –15. Lavelle CLB. 1973. An analysis of the human femur. Am J Anat 141:415– 426. Lusted LB, Keats TE. 1978. The lower extremity. In: Atlas of roentgenographic measurement. 4th Ed. London: Yearbook Medical Publishers, Inc. p. 188. Moore KL. 1992. The lower limb. In: Clinically oriented anatomy. 3rd Ed. Baltimore: Williams and Wilkins. p. 377–379. Stewart TD. 1962. Anterior femoral curvature: its utility for race identification. Hum Biol 34:49 – 62. Trotter M, Gleser GC. 1952. Estimation of stature from long bones of American Whites and Negroes. Am J Phys Anthrop 10:463–514.