Abstract
Femoral neck anteversion (FNA) is the angle between the femoral neck and femoral shaft, indicating the degree of torsion of the femur. Differences in FNA affect the biomechanics of the hip, through alterations in factors such as moment arm lengths and joint loading. Altered gait associated with differences in FNA may also contribute to the development of a wide range of skeletal disorders including osteoarthritis. FNA varies by up to 30° within apparently healthy adults. FNA increases substantially during gestation and thereafter decreases steadily until maturity. There is some evidence of a further decrease at a much lower rate during adulthood into old age, but the mechanisms behind it have never been studied. Development of FNA appears to be strongly influenced by mechanical forces experienced during everyday movements. This is evidenced by large differences in FNA in groups where movement is impaired, such as children born breech or individuals with neuromuscular conditions such as cerebral palsy. Several methods can be used to assess FNA, which may yield different values by up to 20° in the same participant. While MRI and CT are used clinically, limitations such as their cost, scanning time and exposure to ionising radiation limit their applicability in longitudinal and population studies, particularly in children. More broadly, applicable measures such as ultrasound and functional tests exist, but they are limited by poor reliability and validity. These issues highlight the need for a valid and reliable universally accepted method. Treatment for clinically problematic FNA is usually de‐rotational osteotomy; passive, non‐operative methods do not have any effect. Despite observational evidence for the effects of physical activity on FNA development, the efficacy of targeted physical activity remains unexplored. The aim of this review is to describe the biomechanical and clinical consequences of FNA, factors influencing FNA and the strengths and weaknesses of different methods used to assess FNA.
Highlights
US results are closer to magnetic resonance imaging (MRI) than to computed tomography (CT) (Tomczak et al, 1995), which may be because the landmarks can be obtained
The freehand US methods appear more repeatable compared with regular US (Keppler et al, 1999; Keppler et al, 2007; Passmore et al, 2016), with average errors as low as 1.8° (Passmore et al, 2016) and MRI and ICC of 0.95 (Greatrex et al, 2017)
Abnormal Femoral neck anteversion (FNA) changes the biomechanics of the hip, altering muscular lever arms, hip contact forces and femoral neck shear forces, which may contribute to development of a wide range of skeletal disorders, such as osteoarthritis and alter the kinematics of the lower limbs
Summary
The decreased congruity could result in hip dysplasia, a condition that displays FNA averages of 6°– 18° above normal (Alvik, 1962; Fabry et al, 1973; Anda et al, 1991; Sugano et al, 1998b; Li et al, 2014; Lerch et al, 2018), whereas hip congruity (Reikerås et al, 1983) and loading (Heller et al, 2001; Satpathy et al, 2015) might be a contributors to femoral acetabular impingement (Sutter et al, 2015; Chadayammuri et al, 2016; Gómez-Hoyos et al, 2016; Lerch et al, 2018). Some methods place the probe horizontally and measure the inclination on the image on the screen or later on the printed image Moulton and Upadhyay, 1982; Upadhyay et al, 1987; Elke et al, 1991) but results are not consistent at high angles of anteversion (Phillips et al, 1985; Terjesen and Anda, 1987; Elke et al, 1991) where the distal part of the femoral neck becomes deeper and harder to image To adjust for this issue, others use inclinometers mounted on the probe (Terjesen and Anda, 1987; Terjesen et al, 1993; Aamodt et al, 1995; Ehrenstein et al, 1999) and take the measurement when the chosen features are showing horizontally on the screen, or use additional hardware to place the femur in internal rotation (Elke et al, 1991). US results are closer to MRI than to CT (Tomczak et al, 1995), which may be because the landmarks can be obtained
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
