Femoral neck anteversion: a clinical vs radiological evaluation

Abstracts

The purpose of the present study was to verify the correlation between the femoral anteversion angle measured by biplanes radiography and the values of internal and external rotation of the hip obtained by clinical assessment. Sixty-four hips of 32 individuals with no previous coxofemoral pathologies were studied by taking their hip rotation values with a proper instrument - the fleximeter - and taking radiographic images using the Rippstein- Müller method. The results obtained were statistically analyzed and it was concluded that there was no statistically significant correlation and that it is possible that other factors, in addition to the femoral anteversion angle, may be important in determining the range of rotation of the hip joint.

Statistics; Nonparametric; Femur neck; Hip

O objetivo deste trabalho foi o de verificar a correlação entre o ângulo de anteversão femoral medido radiograficamente e os valores das rotações dos quadris apresentados clinicamente. Para isso, foram estudados 64 quadris de 32 pessoas sem nenhuma patologia coxo-femoral prévia, avaliando-se suas rotações com o auxílio de um aparelho específico - o flexímetro - e radiografando os quadris dos pacientes de acordo com o método de Rippstein-Müller. Os resultados obtidos foram analisados estatisticamente, concluindo-se que não houve correlação estatisticamente significante e que, possivelmente, outros fatores, além da anteversão femoral, têm importância na determinação da amplitude das rotações do quadril.

Estatísticas não Paramétricas; Colo do fêmur; Quadril

ORIGINAL ARTICLE

Femoral neck anteversion: a clinical vs radiological evaluation

Roberto Sérgio de Tavares Canto^I; Gilton Santos Anjos Filho^II; Lissejo Magalhães^II; Merandolino Queiroz Moreira^II; Fabiano Ricardo de Tavares Canto^II; Mario Antonio Baraúna^III; Hugo Machado Sanchez ^IV; Ruiz Angelo Ventura Silva^IV

^IDoctor, Post-PhD in Traumatology, University Center of the Triângulo, UNITRI

^IIDoctor, Expert in Traumatology and Orthopaedics, Federal University of Uberlândia, UFU

^IIIPhysical Therapist, PhD in Human Motility, University Center of the Triângulo, UNITRI

^IVPhysical Therapist, Master student in Physical Therapy, University Center of the Triângulo, UNITRI

SUMMARY

The purpose of the present study was to verify the correlation between the femoral anteversion angle measured by biplane radiography and the values of internal and external rotation of the hip obtained by clinical assessment. Sixty-four hips of 32 individuals with no previous coxofemoral pathologies were studied by taking their hip rotation values with a proper instrument - the fleximeter – and taking radiographic images using the Rippstein- Müller method. The results obtained were statistically analyzed and it was concluded that there was no statistically significant correlation and that it is possible that other factors, in addition to the femoral anteversion angle, may be important in determining the range of rotation of the hip joint.

Keywords: Statistics; Nonparametric; Femur neck; Hip.

INTRODUCTION

The anteversion angle (declination) of the femur neck can be defined as the angle formed by the femoral condyles plane (bicondylar plane) and a plane passing through the center of the neck and femoral head^(1,2). If this transverse plane (bicondylar) passes behind the center of femoral head, neck anteversion is present; if the plane described above passes in front of the femoral head, retroversion is present^(2,3).

Femoral neck anteversion usually diminishes with age(4). Between three and 12 months of age, the anteversion average value is 39º, reaching adult life with a value close to 16º^(5,6).

There are many imaging methods described and used for measuring femoral anteversion, such as fluoroscopy⁽⁶⁾, biplane x-rays^(5,6,7), axial x-ray⁽⁶⁾, ultrasound^(1,9), computed tomography^(1,3), nuclear magnetic resonance⁽¹⁾ and 3D modeling⁽¹⁾. From these, the method with biplane x-rays is the most widely used and the one with the lowest cost.

According to Staheli et al.⁽¹⁰⁾, there is a clinical correlation among inward and outward hip rotations and femoral anteversion angle measured by x-ray. A clinical evaluation of patients is important for those presenting with pathologic hips, since such pictures may or may not change the anteversion angle⁽²⁾.

Determining the anteversion angle value is crucial for the diagnostic and therapeutic planning of patients with various pathologies, such as hip development dysplasias, cerebral palsy, varum thigh, flat thigh, epiphysiolysis, congenital club foot, other development abnormalities and metabolic diseases⁽²⁾.

Therefore, the objective of this study is exactly to check the statistical significance of the correlation among the femoral anteversion angle measured by x-ray, and hip rotation values in a population presenting with no previous pathology.

MATERIALS AND METHODS

The sample was formed by clinical and radiographic evaluation of 32 individuals from both genders, with average age of 35.34 + 16.38, proceeding from the Orthopaedics and Traumatology Outpatient Care Facility, of the Federal University of Uberlândia (UFU), either patients or their escorts, randomly selected, being the only pre-requirement the absence of any hip conditions or gait problems.

This research was conducted with the approval of the Committee on Ethics in Research in human beings, from the same institution and with the consent of the volunteers, after they were informed about the objectives of the proposed study.

The clinical evaluation of the universe of individuals studied was restricted to the comparison of inward and outward hip rotations.

For this, a proper instrument was used - the fleximeter - designed from studies⁽¹⁵⁾, developed and manufactured in Brazil, patented and registered at the Code Research Institute (REG.UM 8320-3 RJ).

In this series, measurements were taken, positioning the patient in ventral decubitus, with pelvis horizontally stabilized, being the patient duly relaxed and wearing clothes that allowed for hips full range of motion (the majority wearing underwear). No previous warm-up, passive or active movements were performed with lower limbs. The fleximeter was positioned at the distal third of the leg anterior region, fixed by means of a Velcro band with the tip placed in neutral position 0º/360º (Figure 1). From this position, the right hip inward rotation (RIR), right hip outward rotation (ROR) (Figure 2), and the left hip inward rotation (LIR), left hip outward rotation (LOR) were performed and measured, up to the angle that gravity would support, according to Staheli et al.⁽¹⁰⁾. The test was performed three times in both hips, and the result taken was the arithmetic average of the three measurements.

In the radiological evaluation, x-rays were standardized according to the method by Müller for determining femoral necks anteversion angle values⁽⁷⁾.

Frontal pelvic x-ray was performed with the patient positioned in dorsal decubitus, with parallel extended thighs and knees flexed in 90º, at the edge of the x-ray table (Figure 3).

In order to determine the femoral neck anteversion, the Rippstein-Müller position was used: hips remained flexed at 90º, with abduction of 15º and legs strictly in parallel from each other and to the plane of exam table. Such parallelism is important, as well as the vertical position of the femur in a perpendicular plane to the table, because it was from this plane that the projection of the posterior surface of the femoral condyles appeared in parallel to the x-ray lower edge⁽⁹⁾. In order to facilitate, and in order to obtain standardized x-rays, a proper instrument was used, which maintained the thighs and legs angles steady. That instrument was built using a cursor to adjust variable distances of the hips, as well as to adjust the length of the thighs (Figures 4a and 4b).

After x-rays were taken, the anteversion and inclination angles were determined (Figures 5a and 5b).

The inclination angle corresponds to the angle formed between the femur neck axis and the diaphysis axis: it is also called Muller's cervicodiaphyseal angle⁽⁷⁾.

The anteversion angle is formed between the condylar transversal axis and femoral neck axis. This angle could be precisely measured only when an axial x-ray of the femur was captured⁽⁷⁾.

Because of the femoral neck anteversion, indeed, at the frontal x-ray to the inclination angle measurement, only the projection of the same angle could be measured. Thus, in usual, anteroposterior, and Rippstein-Müller position projections, we measure such an angle with an accuracy of ± 5º. As it is impossible to take in vivo x-rays in femoral axial measurements, the x-ray for determining the anteversion angle was performed with abduction of 15º (Rippstein projection). As such errors are systematic, they are potentially correctable⁽⁷⁾.

For this, tables exist allowing for the correction of values obtained directly from x-rays. In this case, the Müller Table was used (Figure 6), in which corrected values for right hip anteversion angle (RA) and left hip anteversion angle (LA) were found⁽⁷⁾.

The authors divided themselves into two teams so that those who performed clinical measurements with the fleximeter could not participate on determining x-ray angles.

The collection provided the following data: gender; age; race; ROR; RIR; ROR+RIR; RA; LOR; LIR; LOR+LIR, and; LA.

For the statistical analysis, the verification on data distribution normality or abnormality was firstly performed by the proof "An analysis of variance test for normality". Such test indicated that the distribution did not comply with normality curve.

In view of those results, nonparametric methods were applied.

With the purpose of checking the existence or not of significant correlations among rotation measurements and anteversion angles, the Spearman's Correlation Coefficient by Posts was applied to the data.

With the purpose of comparing inward and outward rotations in the same side, the Wilcoxon test was applied to the values series, combined in pairs.

The significance level was established at 0.05 for all tests applied.

RESULTS

Table 1 presents, in a systematized way, the descriptive analysis of data regarding right and left hips, concerning the femoral neck anteversion angle measured by x-ray, the inward and outward rotations measured with the fleximeter, and the left hip rotation range, represented by the sum of outward and inward rotations.

Tables 2 and 3 show the rs values found and the probabilities associated to them, obtained when the Spearman's Correlation Coefficient by Posts was applied to ROR and RIR measurements, and to the sum of the ROR and RIR measurements with the measurements of the right femoral neck anteversion angle, as well as when applied to LOR and LIR measurements, and to the sum of the LOR and LIR measurements with the measurements of left femoral neck anteversion angle, with and without differentiation by gender. In Table 2, a significant negative correlation can be observed only among the measurements of LOR x LA and LOR + LIR x LA, and, in Table 3, a significant negative correlation was found only among the measurements of LOR x LA, within the female group.

Significant differences were found among outward and inward rotations to the right (p=0.0002) and to the left (p=0.00006).

DISCUSSION

According to Maud⁽¹¹⁾ ten to twenty full range passive movements should be performed in order to assure an appropriate musculoarticular relaxation for a more accurate measurement of the hip motion degree. Nevertheless, we chose not to perform such warm-up, because it does not represent the daily reality of an orthopaedic doctor. On the hip inward and outward rotation range evaluation by Bloomfield et al.⁽¹²⁾ and on the correlation study between passive rotation and femoral anteversion in children, performed by Kozic et al.⁽¹³⁾, volunteers were assessed when positioned in dorsal decubitus on the bed, with extended lower limbs. The goniometer was positioned at planta pedis, and the outward and inward rotations from the feet were performed, respectively, and recording the ranges of motion indicated by the tip. In turn, Staheli et al.⁽¹⁰⁾ preferred the patient positioned in ventral decubitus, with knees flexed at 90º, rotating thighs inwards and outwards, allowing legs to be pending from one side to the other by gravitational forces, thus recording the angles found. In this study, the methodology by Staheli et al.⁽¹⁰⁾ was preferable to those by Bloomfield et al.⁽¹²⁾ and Kozic et al.⁽¹³⁾, because it was considered that, when evaluation was performed with the extended limb and the fleximeter positioned at the foot, there is a higher potential for errors due to movements on knee joints, tibiotarsal and subtalar. The evaluation with knee flexed at 90º and fleximeter positioned at the leg eliminates those potentials and allows for a clearer assessment, since leg's range of motion is more noticeable than foot's, due to its dimension.

In this study, we saw that, in a 95% confidence interval, the anteversion angle ranged from 12.10° to 17.59° to the right, and from 14.77° to 19.73° to the left, making an average of 14.84° + 7.60° to the right and, to the left, 17.25° + 6.89, which perfectly agrees with literature, describing an average of 16º^(4,5) in adult life. Results are also in accordance to literature concerning hip rotations. In the studied population, the left outward rotation angle, measured by the fleximeter, varied in an interval of 42.31° to 47.63°. In Table 1, we can see an average for the left outward rotation angle of 44.97° + 7.37°, and for the right angle of 43.95º + 7.36°, while Staheli et al.⁽¹⁰⁾ expect an average of 45º.

According to the results shown in Table 2, a significant negative correlation was found only among the LOR x LA and LOR + LIR x LA measurements. This means that, as values for one variant increase, the values for the other variant decrease, and vice-versa. The statistical evaluation, thus, as opposite to expected from literature, does not present a correlation among hips rotations (ROR and RIR), range of hip rotation (ROR + RIR and LOR + LIR) and femoral necks anteversion angles of the respective sides. Exceptions are those two situations in which a negative correlation occurs (LOR x LA and LOR + LIR x LA), according to foreseen in literature^(1,10,14).

According to the results shown in Table 3, a significant negative correlation was found only among LOR x LA measurements, within the female group, which only corroborates the observations on the previous table, demonstrating the lack of correlation among rotations, joint range of motion, and femoral neck anteversion angles, being the only correlation existent due to the LOR in female patients.

Although there is a statistical significance between LOR x LA only for females, no other significant correlation was found among the anteversion angle and rotation measurements. This single statistically significant correlation found in this group comprised of 11 women (hardly explained) allow us to confirm, based on all other findings, that a statistical significance would really be inexistent, by the design in which the study was developed, among the x-ray anteversion angle and inward and outward rotation degrees measured by the fleximeter. Although Staheli et al.⁽¹⁰⁾ and Kozic et al.⁽¹³⁾ state that the anteversion strongly clinically influences hip rotations, also reporting that, in the severe form of anteversion, inward rotation is greater than 90º and the outward rotation is equal to 0º, and that the evaluation of hip passive range of rotation serves as a predictor to abnormal femoral anteversion in children. However, it is worthy to highlight that those studies were performed in children presenting with lower limbs' orthopaedic problems, such as "in toe" and "out toe"⁽¹⁵⁾, as opposed to our research, performed in healthy adult individuals, not presenting with any deformities.

Nonetheless, in the studies by Tonnis and Heinecke⁽¹⁴⁾ performed in adults with no lower limbs' problems, the significant correlation between the hip anteversion angle and hip rotation was found, although minimal. According to those authors, patients with an outward rotation greater than the inward rotation had femoral retroversion, while those with greater inward rotation presented femoral anteversion.

In this study, statistically significant differences were found among rotations, being the outward rotation averages higher than inward rotation averages. However, there was no influence of femur neck retroversion on the outward rotation.

In view of these results, we can conclude that, for the great majority of people whose anteversion degree is close to normal values in the general population, hips rotation range of motion is also influenced by other factors, and not only by femoral anatomical configuration.

We can say that, although most of times the clinical test gives a close view of the femoral neck anteversion, the values found cannot be fully reliable in representing the value of the x-ray angle, according to the findings of this study. Grunert et al.⁽⁸⁾ report, however, that the Rippstein-Muller method shows a variance of 5 to 15º on the evaluation of femoral neck anteversion and propose the use of alternative methods for this kind of orthopaedic evaluation.

It would be interesting in the future, if this investigation method is maintained, to submit volunteers to a warm-up and flexibility gain program before taking clinical measurements. Some authors advocate the use of controlled temperature rooms for measuring the range of motion⁽⁹⁾.

CONCLUSION

There were no statistically significant correlations among clinical measurements of hips inward and outward rotations, measured with the use of a fleximeter, with femoral necks anteversion angles measured by x-ray.

REFERENCES

Received in 25/02/05 approved in: 03/05/05

Study conducted at the Orthopaedics Outpatient Care Facility, Federal University of Uberlândia – UFU – and University Center of the Triângulo – UNITRI

Correspondences to: Secretaria de Pós Graduação - Av. Nicomedes Alves dos Santos, 4545 – Bloco E – B - Gávea – Uberlândia – MG – CEP: 38411-106 - e-mail: [e-mail]

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Publication Dates

• Publication in this collection
  09 Nov 2005
• Date of issue
  2005

History

• Received
  25 Feb 2005
• Accepted
  05 May 2005