|Year : 2021 | Volume
| Issue : 3 | Page : 148-154
Evaluation of neck–shaft angle of dry femora in the gangetic region of West Bengal
Barnali Mukherjee1, Anirban Sadhu2, Sudeshna Majumdar3
1 Assistant Professor, Department of Anatomy, KPC Medical College, Kolkata, West Bengal, India
2 Associate Professor, Department of Anatomy, North Bengal Medical College, Darjeeling, West Bengal, India
3 Professor, Department of Anatomy, North Bengal Medical College, Darjeeling, West Bengal, India
|Date of Submission||31-Dec-2020|
|Date of Decision||21-Feb-2021|
|Date of Acceptance||19-Jun-2021|
|Date of Web Publication||30-Jul-2021|
Department of Anatomy, North Bengal Medical College, Sushrutanagar, Darjeeling - 734 012, West Bengal
Source of Support: None, Conflict of Interest: None
Background: Femur being the strongest and longest bone of the skeleton plays a crucial role in maintaining the usual anatomy of the hip joint. The neck–shaft angle (NSA) contributes greatly to the daily activity of the hip joint and therefore is of considerable importance in planning a proper surgery. Knowledge of the usual range of NSA is, therefore, imperative in the proper treatment of patients who present with disease of the hip related to the NSA. The objective of the present study was to estimate the minimum, maximum, mean, median, and range of NSA and to determine the difference(s) between the right and left sides of dry adult femora in the Gangetic region of West Bengal. Methodology: The present study was conducted on 281 dry adult femora (144 on the left and 137 on the right sides). The femora were selected according to the inclusion and exclusion criteria. Measurements of NSA were based on the standard method. Results: The mean NSA of the total sample size was 124.12° ± 6.231°. The means for the left and right NSAs were 123.33° ± 6.47° and 124.91° ± 5.885°, respectively. The mean difference between the right and left femora was statistically significant. There was also a high degree of positive correlation between the NSAs of the left and right sides. Conclusion: This study establishes baseline data for the NSA of the Gangetic region of West Bengal, India. This will be helpful for orthopedic surgeons and implant makers to properly design and treat patients with problems of the NSA.
Keywords: Coxa valga, coxa vara, femur, neck
|How to cite this article:|
Mukherjee B, Sadhu A, Majumdar S. Evaluation of neck–shaft angle of dry femora in the gangetic region of West Bengal. Natl J Clin Anat 2021;10:148-54
|How to cite this URL:|
Mukherjee B, Sadhu A, Majumdar S. Evaluation of neck–shaft angle of dry femora in the gangetic region of West Bengal. Natl J Clin Anat [serial online] 2021 [cited 2022 May 22];10:148-54. Available from: http://www.njca.info/text.asp?2021/10/3/148/322809
| Introduction|| |
The neck–shaft angle (NSA) is defined as the obtuse angle formed by intersection of two axes: the axis of the femoral shaft with that of the femoral neck., This helps to keep the limb away from the pelvis during its movements. It is widest at birth and decreases gradually until the age of 10 years. Usually, the NSA value is 127° and it varies according to climate, clothing, lifestyle, sex, age, and side. Hence, the NSA is prone to variations. Usual ranges have been established through various studies in different populations.
A decrease in NSA is termed as coxa vara whereas an increase in the same is called coxa valga. The range of NSA varies for coxa vara and coxa valga as per different studies. The authors like Beall et al., Dolan et al., and Boese et al. consider a NSA <120° to diagnose coxa vara whereas Morvan et al. considered NSA <130° for the same. Beall et al. and Coskun Benlidayi et al. consider a NSA ≥135 to represent coxa valga. However, Dolan et al. and Morvan et al. view a NSA >140° to consider the same. For the present study, decreased and increased NSAs <120° and ≥135° are considered as coxa vara and coxa valga, respectively. In addition, the mechanical strength of the proximal femur is related to the NSA. The latter is also named as the angle of inclination, collo-diaphyseal angle, and cervico-diaphyseal angle.
The NSA along with the angle of anteversion is used for quantifying the orientation of the femoral neck. Improper orientation may lead to impaired gait and posture as well as injury to the joint. Proper knowledge of NSA is essential for designing implants and planning operations on the hip joint. A strong correlation has been established between the occurrence of thigh pain and the inadequate fit and fixation of the implant. Studies have also noted asymmetry of the NSA angles between the right and left femora.,,,,, Knowledge of this asymmetry is important for the treatment of femoral fractures. Morphological data for the proximal epiphysis of the femur are essential in anthropological, forensic, and clinic studies as well.
Significant differences exist among various ethnic groups and also between past and current populations. The NSA also varies with age, stature, and width of the pelvis. Thus, it is clear that data on the NSA obtained from studies conducted elsewhere are of less clinical significance in this region of the country. This study was, therefore, conducted to estimate the usual value of NSA in this region of the country.
| Methodology|| |
The study was carried out on 281 dry adult femora. It was a cross-sectional analytical study conducted at the Department of Anthropology, Ballygunge Science College, Kolkata, and KPC Medical College, Kolkata. Permission from the Institutional Ethics Committee, KPC Medical College, Kolkata, was obtained for the study. One hundred and forty-four left femora and 137 right femora were selected for the study. The side was determined as per the guidelines mentioned in the standard reference book of Anatomy. The sample was obtained by simple random method over 6 months. Femora that were intact with well-preserved landmarks and devoid of any arthritic change were selected for the study. There was no attempt to determine sex as it is erroneous to derive sex from a single bone. Bones with fracture, unossified portions, decay, deformity, and disease were excluded from the study.
Since there are several methods of measuring the NSA, the authors opted for a suitable approach based on the availability of resources at their disposal. The authors devised their method based on those of Singh and Bhasin, Sinha et al., and Siwach.
Each dry femur was fixed on a plane surface horizontally with the bony projections (trochanters and condyles) touching it. Thus, all markings and measurements were done on the surface of the femur that was directed superiorly, away from the plane surface on which it was fixed. Thus, the surface of the femur on which the study was done corresponded to the smooth and convex anterior surface of the shaft. Two relevant axes (neck and shaft) were then marked on the bone by a black marker. The long axis of the neck was determined by joining the line between two fixed points: the first point was marked at the center of the head by visual inspection. The second point was marked at the center of the neck. The latter point was determined by measuring the width of the most constricted part of the neck and choosing its midpoint by Vernier caliper [Figure 1].
|Figure 1: Method of determining the most constricted point of the neck of the femur|
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For the long axis of the shaft, two more points were marked at the middle of the lower [Figure 2] and upper ends of the shaft, respectively. The upper end is located at the intertrochanteric line and the lower end at the junction of the shaft with the condyles. The width of the shaft was measured at those two levels, and the midpoints were marked accordingly by Vernier caliper.
|Figure 2: Measurement of the width of the lower end of the femur at the junction of the shaft and the condyles|
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All these were measured in the transverse plane. The longitudinal axis was then marked by joining those points. The two axes so derived were extended in such a manner that they intersected at the upper end of the femur [Figure 3].
|Figure 3: Axes of shaft and neck of the femur are extended to intersect at the upper end, and neck–shaft angle is drawn on over the bone|
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The angle formed was then measured with the help of a goniometer [Figure 4]. The angles were measured by two observers. The data from each were stored in Microsoft Excel format. Mean, median, maximum value, minimum value, range, and standard deviation (SD) were calculated separately for the entire sample, 143 left femora and 137 right femora. The confidence interval was set at 95%. The independent sample t-test was applied to ascertain any statistically significant difference between the mean NSAs of the left and right femora, and P < 0.05 was considered to be statistically significant. Pearson's correlation coefficient was also calculated to estimate the strength of association between the two sets of femora. The data were analyzed with R software version 4.0.3.
| Results|| |
The mean NSA of 281 femora in the present study was 124.12°. The respective values for the left and right sides were 123.33° [Table 1] and 124.91°.
The difference between the mean values of the left and right NSAs was statistically significant (P = 0.03878) [Table 2]. Pearson's correlation coefficient was 0.9554, implying that there is a highly positive correlation between the NSAs of the left and right sides.
|Table 2: Difference in means of neck-shaft angles of the left and right femora by the independent sample t-test P (T≤t) two-tail=0.03878 which is <0.05|
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A frequency comparison of the left and right NSAs is also depicted [Figure 5]. The x-axis indicates the interval length of the left and right NSAs. The intervals are created using the 20th percentile of the sample range. The y-axis represents the frequency of the sample of the left and right femora for the corresponding interval length.
|Figure 5: Frequency comparison of neck–shaft angles of the left and right femora|
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Skewness and kurtosis of the left NSA were depicted through a histogram [Figure 6]. For the left side, a skewness of − 0.33 was observed. Thus, it was negatively skewed, indicating that more samples were in the upper value cells (right side) and few samples were in the lower value cells (left side). Kurtosis for the left side was − 0.96, which implies that the distribution of left NSAs was flatter than a normal curve with a mean and SD of 124.12° and 6.231°, respectively [Table 1]. Skewness and kurtosis for the right side, depicted in [Figure 7], were − 0.91 and − 0.19, respectively. Thus, it was also negatively skewed with implications similar to the left side. The value of kurtosis implied that the distribution of right NSAs was flatter than a normal curve with a mean and SD of 124.91° and 5.885°, respectively [Table 1].
| Discussion|| |
The present study has compiled data for the NSAs of the left and right femora in dry bones from the Gangetic region of West Bengal. These data may be compared with studies conducted elsewhere to observe variations and similarities in the NSAs of different groups of population. The overall mean value of NSA was in close agreement with the studies conducted by Sharma and Lal, Suresh et al., Sharma et al., Siwach, Roy et al., and Neelima et al. [Table 3]. This indicates that the population of Bihar, Kolar, Himachal Pradesh, Haryana, Andhra Pradesh, and Andhra Pradesh were closely related to the present study. The study conducted by Siwach was the only one to report lower values for mean NSAs. The authors of the present study assumed that the study sample was representative of this region. No attempt was made to ascertain the race and sex of those bones as it is erroneous to do so from a single bone. The authors, therefore, observed the range of NSAs belonging only to the Gangetic population of West Bengal, India. The variations among the studies are due to factors (climate, clothing, lifestyle, sex, age, and side) as mentioned by Giligan et al.
Regarding the left and right NSAs, values similar to the present study were observed by Suresh et al., Bharathi et al., and Gullapalli and Inuganti. Other investigators, as mentioned in [Table 6], Khan and Saheb from Karnataka, Choudhary et al. from Bihar, Rajendran et al. from South India, Ravi G O et al. from Karnataka, Agrawal et al. from Central India, Nallathamby et al. from South India, and Gujar et al. from Gujarat, Chaudhary et al. from Karnataka, have reported wider variations. The mean value of NSA on the right side was greater than that of the left side in the present study.
|Table 3: Comparison of the overall mean of the present study with previous Indian studies|
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|Table 4: Comparison of the overall mean of the present study with previous foreign studies|
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|Table 5: Comparison of the mean of both sides of the present study with previous foreign studies|
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|Table 6: Comparison of the mean of both sides of the present study with previous Indian studies|
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The disagreement with other studies as observed in [Table 4] and [Table 5] may be explained by the findings of Giligan et al. According to them, variations in age, climate, clothing, economic status, gender, lifestyle, occupation, and side are related to NSA. There may also be differences in measuring techniques of the NSAs by these authors. Such differences may include the use of sophisticated instruments, radio-imaging techniques, and reference landmarks on the bone. The present study has not addressed these parameters. The previous studies have also not focused on these points. The strikingly different data from these studies may be explained on the basis of highly variable sample characteristics and/or measuring methods of the respective NSAs.
A statistically significant (P < 0.05) difference was observed between the mean NSAs of the left and right sides [Table 2]. This can again be explained on the characteristics of the population of this region. No such difference was observed by Agrawal et al., Shrestha et al., and Rajendran et al. [Table 4] and [Table 6] and Osorio et al. [Table 5]. Rajendran et al. found the difference between the left NSAs of their study and those of Verma et al. to be highly significant., The present study did not perform any such comparison with other studies due to time and logistical constraint. The authors, however, agree that such comparison would definitely have added to the strength of the study.
In the present study, the mean right NSA was greater than the left. Indian studies with similar findings are those by Agrawal et al., Suresh et al., Bharathi et al., Ravi G O et al., and Khan and Saheb et al. The rest of the studies presented with a greater mean left NSA than the right [Table 6]. Among the international studies, only Macho et al. reported lower values than the present study. Anderson and Trinkaus reported quite higher values than the other authors. Other authors like Shrestha et al., Osorio et al., Mukhia et al., and Liang et al. reported values very close to the present study [Table 4].,,, Regarding sidedness, Mourão and Vasconcellos reported lesser mean values than the present study for both the sides. However, the mean values of NSA reported by them were lesser on the right than the left side. They opined that the different methodologies employed by different authors were the reason behind different values obtained by various authors. The other authors, Mukhia et al., Shrestha et al., Caetano et al., Osorio et al., and da Silva et al., reported a greater mean value than the present study on the left side.,,,, For the right side, Shrestha et al. and Caetano et al. observed a greater mean value than the present study whereas Mukhia et al., Osorio et al., and da Silva et al. reported lesser value.,,,, Ferrario et al. observed a common feature of NSAs in humans – asymmetry. They also observed a greater length of the left femur than the right. Furthermore, Issac et al. observed that a positive correlation exists between the NSA and the length of the femur – a greater length of the femur indicates a greater NSA and vice versa. According to them, since the left femur transmitted more weight, it was dominant. All these observations explain the greater mean NSA on the left side than on the right. The greater mean NSA on the right side in the present and other studies may be due to greater weight transmission on the right side, differences in the method of measuring the NSAs, or characteristics of the population. A combination of all these factors may also be of relevance. It would be beneficial to study the correlation of NSA with the length of the femur on the respective study in order to further shed some light on this aspect.
| Conclusion|| |
the present study has gathered data for the NSAs of dry femurs belonging to the Gangetic region of West Bengal on the basis of some inclusion and exclusion criteria. Analysis of these data revealed that the results were following some regional data of the country. This study has achieved its primary objective of compiling baseline data for NSAs of the Gangetic region of West Bengal. There is a strong positive correlation between the two sides. These normative data will give an insight to other investigators desirous of conducting more research on this topic.
The authors would like to express their gratitude to Mr. Tanmoy Majumdar (M. Sc. in Statistics) for his invaluable contribution in the statistical analyses of data in this original research article.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]