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Prediction of risk of fracture neck femur even without any radiation exposure simply by measuring the inter- epicondylar distance with the help of sensitive calipers
Associate Professor, Department of Anatomy, Nalanda Medical College Patna, INDIA. Email: subodh.nmc@gmail.com
Abstract Fracture neck femur is an important health related problem causing considerable morbidity and sometimes mortality. A number of radiologically measurable variables viz. the neck shaft angle, neck length and neck circumference of femur have been found to have relationship with the risk of fracture neck femur. Methods: Our study conducted at the department of Anatomy, Nalanda Medical College Patna, attempted to search for a correlation if any, between such variables and clinically measurable ones like interepicondylar distance and the distance between greater trochanter to lateral epicondyle of femur. After a careful screening, 50 properly seasoned and dry femora were selected in this study, during the period of April 2017 to March 2018. Results: All variables were skewed by Kolmogorov-Smirnoff goodness of fit test and right and left femoral groups did not differ significantly for any variable under study. No positive or negative correlation was detected amongst the variables measurable only radiologically and the clinically measurable variables. Conclusion: A screening test and subsequent prophylactic measures could have been suggested to prevent the fracture. However, at the end of the study, no suitable alternative to the radiological assessment was detected. Nevertheless, the wide applicability of such a procedure, if ever developed, warrants a quest for other anthropometric variables that can serve the purpose and future studies may be undertaken accordingly. Key Word: neck femur, epicondylar, greater trochanter, goniometer, calipers
INTRODUCTION Femur is the longest and strongest bone of the body having two ends and an intervening shaft and helps in transmission of body weight from hip bone to tibia in standing position. Proximal end of femur consists of head, neck and two trochanters. Femoral neck is a constricted part connecting head with shaft at an angle of about 125°-known as angle of inclination or neck shaft angle (NSA); this facilitates the movement of hip joint enabling the limb to swing clear of pelvis. Length of femur is associated with a striding gait and its strength with weight and muscular forces1. In standing position the alignment of femora are oblique-their head separated by the pelvic width, their shaft converging downwards and medially to where the knees almost touch. Femoral obliquity varies-it is greater in women due to wider pelvis and shorter femora in comparison to male. Abnormal femoral neck angle (FNA) may be associated with various clinical problems ranging from harmless in toeing gait in childhood to disabling osteoarthritis in adults2. Angle of femoral inclination is greatest at birth (almost straight) and gradually diminishes (become more acute) until adult angle is reached (125° approx). The angle is less in female due to wider pelvis and greater obliquity of shaft. The neck is also laterally rotated with respect to shaft-angle of ante-version which is about 10°-15°.There may be racial variation in angle of ante-version1. The neck of femur is narrowest in the midpoint and widest laterally and contour of neck is rounded1. The greater trochanter is a large quadrangular projection from junction of neck and shaft. Its postero-superior region projects supero-medially and overhangs the adjacent post surface of neck. The apex or highest point of greater trochanter can be felt sub-cutaneuoslyi.e palpable when muscles are relaxed. The proximal border of femur is about a hand’s breadth below the iliac tubercle. The distal end of femur is widely expanded for transmission of weight to tibia having two massive condyles -medial and lateral which are partly articular. Anteriorly the condyles unite and are continiuos with the shaft, posteriorly the are separated by a deep inter-condylar fossa. The lateral condyle is less prominent but more massive than medial condyle and more directed in line with femoral shaft and hence transmits more weight to tibia. The most prominent points on medial and lateral condyles are the two epicondyles which are palpable. The lateral epicondyle gives attachment to fibular collateral ligament. The medial epicondyle liesantero-inferior to adductor tubercle and gives attachment to tibial collateral ligament.
MATERIALS AND METHODS Study Type: Observational study Study Place: Our study was conducted at the department of Anatomy, Nalanda Medical College Patna. Study Period: April 2017 to March 2018. Study Population: 50 dry femora. Place of data collection: Dept of Anatomy of Nalanda Medical College Patna. Study Variables:
Inclusion criteria:
Exclusion criteria
Procedure of data collection Instruments Used
Dry femora were collected from the departments of Anatomy of various medical colleges following the inclusion and exclusion criteria. Bones with visible abnormalities like degeneration, decalcification and loss of bone tissue due to manipulation were excluded. The following measurements were taken from each femora meticulously -neck-shaft angle, neck-length, neck-circumference, inter-epicondylar distance and distance between lateral epicondyle and highest point of greater trochanter. When the plan of the study was undertaken the neck – circumference and the distance between lateral epicondyle and highest point of greater trochanter were not in the proposal. Nevertheless, during the process of data collection it was realized that these variables may also be useful to search for a co-relation among anthropometric parameters. Each parameter was measured thrice and then mean was calculated. All parameters were measured by same observer. The neck-shaft angle was measured by goniometer. The inter-epicondylar distance and the neck length were measured by calipers. The neck circumference and distance between greater trochanter and lateral epicondyle were measured by the metric tape3. For measurement of the neck shaft angle the respective bone was first held in its anatomical position, then the two limbs of the goniometer were made to align along the axis of neck and shaft. The angle between the two limbs of goniometer gives the value of the corresponding neck-shaft angle of femur. Circumference of femoral neck: Measured at midpoint between base of femoral head and inter-trochanteric line with the help of metric tape. For denoting the mid-point of the neck the neck length was first measured and then divided by two. The distance thus obtained is measured either from the inter trochanteric line or from base of head. The point is demarcated with the help of pencil. Neck shaft angle: Angle between major axis of shaft and major axis of neck (measured at posterior surface of neck). Length of femoral neck: Distance between inferior region of base femoral head and lower end of inter-trochanteric line on the anterior aspect of femur measured with the help of metric tape. Inter-epicondylar distance: Distance between medial and lateral epicondyles which are the most prominent points on medial and lateral condyles respectively. The two ends of calipers are fixed on the two epicondyles and distance in between the two ends of calipers gives the value of inter-epicondylar distance. Distance between lateral epicondyle and greater trochanter: Distance between highest point on greater trochanter to the lateral epicondyle measured by the metric tape. RESULTS Table 1: Descriptive statistics of numerical variables Whole cohort. LL = lower limit, UL = upper limit)
Table 2: Descriptive statistics of numerical variables – Left cohort [n =27]
Table 3: Descriptive statistics of numerical variables – Right cohort [n = 23]
Table 4: Comparison of numerical variables between Right and Left – Mann-Whitney U test
Table 5: Correlation between neck length and inter epicondylar distance
Table 6: Correlation between neck length and greater trochanter to lateral epicondylar distance
Table 7: Correlation between neck shaft angle and inter epicondylar distance
Table 8: Correlation between neck shaft angle and greater trochanter to lateral epicondylar distance
Correlation coefficient 0 to <0.3: No relationship; 0.3 to <0.5: Fair relationship; 0.5 to <0.7: Good relationship; >0.7 to 1: Excellent relationship. From the analysis it was revealed that no positive or negative correlation exists between the study variables. Therefore, it is not possible to predict the value of one or more of them from the magnitude of the other variable(s).
DISCUSSION Osteoporotic fracture accounts for >90% of all fractures above 50 years of age with almost 25% mortality. Of the patients who survive more than 6 months following fracture only 60% regain their pre-fracture walking ability and 50% regain their pre-fracture activities of daily life. In elderly patients hip fracture mainly results due to fall from height or tipping over any obstacle but in younger patients high energy trauma like road traffic accident may be the cause. Pathological fracture may occur at any age associated with metastasis, hyper-parathyroidism, osteogenesis imperfecta, Paget”s disease, steroid and alcohol use or infection. However osteoporosis remains the major cause of fracture which occurs mostly in elderly patients with low bone mineral density and risk of fracture doubles every decade after 50 years of age. Old age especially female sex or associated with excessive caffeine use, smoking, dementia, visual impairment, obesity, physical inactivity, arthritis, low body mass index further aggravate the risk. In developing country like India risk is even higher due to vitamin-D or calcium deficiency specially in post-menopausal women. The mortality and morbidity associated with fracture neck femur imposes immense physical, mental, social and economic trauma to both the patient and the family. It has been documented in various literature that neck-shaft angle of femur, neck-circumference, neck length i.e. proximal femoral geometry is well associated with risk of fracture neck femur. Lower values of neck-circumference is associated with low bone-mineral density and hence higher risk of fracture. The proximal femoral geometry can be accurately measured by either DEXA scan or CT-scan. Hence risk of fracture can be predicted in a person by doing DEXA or CT scan. Once the high risk group is identified proper preventive measures can be undertaken like Vitamin-D or calcium supplementation, exercise to strengthen bone mass, visual aids for elderly. DEXA or CT scan exposes the patient to radiation hazard which may predispose the patient to risk of development of leukemia, breast cancer and other malignancy in later life. DEXA or CT scan is not only expensive but facilities are also not available at all medical centres specially in rural and remote areas where lack of awareness, illiteracy, nutritional deficiency are even more prominent. Hence there is a need for an inexpensive, authentic, safe, sensitive yet easy procedure to predict the risk of fracture neck femur. This study was undertaken to find co-relation between proximal and distal femoral geometry i.e. between neck-shaft angle, neck-length, neck-circumference with inter-epicondylar distance and distance between lateral epicondyle to greater trochanter. The inter-epicondylar distance and distance between lateral epicondyle to greater trochanter are easily measurable in an individual by a pair of sensitive calipers and a metric tape. However, a more precise measurement of the aforementioned parameters could have been done by using a rectangular dioptograph which was not available in the study setting. Moreover, Vernier calipers and metric tape were suitable instruments for use at the peripheral health centres if our study could find the study variables useful for the bigger purpose. Had there been an association between the clinically measurable parameters like interepicondylar distance or distance between greater trochanter to lateral epicondyle and the radiologically measurable parameters associated with a risk of fracture neck femur viz. neck shaft angle, neck length or neck circumference, it would have been very useful to predict the risk of fracture in an individual by simply measuring the first two parameters clinically instead of exposing the patient to radiation hazard associated with DEXA or CT scan. This simple measurements can be even taken by para-medical staff or other health workers since it does not require much of expertise. After meticulous collection and analysis of data, it was revealed that there is no statistically significant association between the aforementioned clinical and radiological parameters. Therefore, for an estimation of the risk of fracture neck femur, radiological assessment cannot be replaced as yet. However, in view of the necessity and utility of a clinical procedure that can possibly be applied to a large population, future studies may be undertaken with a wide array of other anthropometric parameters to search for an interrelationship amongst them.
CONCLUSION Our study attempted to find out if it was possible to predict the risk of fracture neck femur without exposing the subjects to radiation hazards associated with a radiological imaging. It would have also been very useful in developing countries with restricted resources, if a simple measurement procedure could estimate the value of parameters associated with a fracture risk and measurable only radiologically. A screening test and subsequent prophylactic measures could have been suggested to prevent the fracture. However, at the end of the study, no suitable alternative to the radiological assessment was detected. Nevertheless, the wide applicability of such a procedure, if ever developed, warrants a quest for other anthropometric variables that can serve the purpose and future studies may be undertaken accordingly.
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This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.