Introduction

Alterations in Femoral neck Anteversion (FAV), is defined as the angle between a conceived transverse line through the knee joint and an imaginary transverse line passing through the center of the femoral head and neck (1). On the average, FAV ranges from 30–40 degrees at birth which dwindles throughout life due to several hereditary and environmental factors (1). FAV has been proposed to be engaged in the pathogenesis of several diseases including slipped capital femoral epiphysis, knee and patella instability, and in or out-toeing gait patterns. There is controversial hypothesis that a persistent increase in FAV predisposes to osteoarthritis of the hip. Some previous studies have supported the hypothesis (2-4), whereas others have not (5,6). Osteoarthritis is a common degenerative joint disease and one of the leading causes of physical and psychological disability in the elderly that can affect any joint in the body, including hips (7). The pathogenesis of osteoarthritis involves process of progressive cartilage matrix degradation causing the cartilage to soften and lose elasticity and leading to surface integrity and resulting in loss of joint function and angular deformity or malalignment (8).

Osteoarthritis of the hip is classified into two groups.

Primary or idiopathic disease which its etiology is not completely understood and it has been suggested that it might be caused by unrecognized or mild hip dysplasia, previous slipped capital femoral epiphysis, Perthes’ disease, or other morphological abnormalities around the hip; and secondary disease which is caused by hemochromatosis, hyperparathyroidism, hypothyroidism, acromegaly, hyperlaxity syndromes, Paget’s disease, gout, chondrocalcinosis, etc. (9-14) .

FAV has also been hypothesized to be a predisposing factor in early osteoarthritis of the hip. Terjesen in an evaluation of 50 osteoarthritic patients and 30 normal controls by means of biplanar radiographies, reported no osteoarthritis in 3 of patients with increased anteversion and most of the patients with the osteoarthritis of the hip had normal anteversion angle, however, as there was a significant relationship between increased FAV angle and osteoarthritis of the hip comparing to control group, it was suggested that increased FAV in adults might contribute to later development of osteoarthritis of the hip as a predisposing factor (15).

Accurate and objective measurement of FAV is extremely consequential in selecting patients and treatment, as well as an accurate imaging technique.

Beside clinical examination, there are several imaging techniques for the measurement of FAV, including bi-plane radiography, fluoroscopy, ultrasound, Computed Tomographic Scanning (CT), and Magnetic Resonance Imaging (MRI) (16-18). Most femoral torsion problems are evaluated by CT, thus it is widely believed as the most accurate and the gold standard of diagnosis of FAV (19).

There are several CT methods employed in measuring FAV. The classic method defined by Weiner, which is based on a single CT image; another method introduced by Reikeras, in which the neck axis is defined by two superimposed images of the femoral head and neck. In the method of Murphy two proximal and one distal images and the angle in the transverse plane between the intersection of the plane of anteversion and the condylar plane defines the accorded angle. The latter method is the most popular CT method which is broadly used (20-22).

The purpose of this study is to evaluate the femoral neck anteverion angles in CT images of patients with hip osteoarthritis and in normal control group in order to illuminate the probability of its contribution to osteoarthritis of the hip.

Materials and Methods

This was a cross-sectional study on 36 patients with different degrees of hip osteoarthritis and 36 normal controls which was conducted during late-2013 to mid-2014, following obtaining confirmation from medical research ethics committee, Mashhad University of Medical Sciences, Mashhad, Iran.

Eligible patients were divided into two groups of hip osteorthritis and control, according to evidences of osteoarthritis of the hip in previous CT images and a thorough physical examination. The normal controls were selected from patients in whom CT of the pelvic region was indicated for various disorders other than hip joint problems. Objective data including age, gender, weight, prior surgeries and history of any background congenital or systemic diseases were collected and inputted in a predesigned form. Osteoarthritis of the hip were classified to five different grades according to severity of the disease (Table 1) (23).

CT images of all cases with 20 years of age or older who referred to radiology ward of Imam Reza hospital, Mashhad, Iran were evaluated by an experienced radiologist who was blind to the patients’ group.

Sample size were calculated according to previous study of Reikeras and colleagues (24).

Images were obtained axially through the hip and femoral neck above the knee while patients were in supine position with slice thickness of 1.25-mm and 1.25-mm of reconstruction interval (120 kV; automatic dose modulation; pitch, 1.375:1) and finally they were reconstructed in the coronal, sagittal, and oblique axial planes. The CT imaging was done with GE VCT 64, GE LightSpeed 16, GE BrightSpeed 16, and GE Plus 8 (GE Healthcare Technologies, Waukesha, WI) scanners.

The CT measurements were performed by an expert radiologist blinded to patients’ group and anteversion degree of femoral neck from was studied both limbs.

The technique for determining the version of the femoral neck was done in a systematic mode, and using the classic method, in every patient we chose a CT image containing the best scan of femoral head and neck, trochanter, and hip joint. Then, we measured the angle between an imaginary line passing through the chosen image and horizontal plane, and the angle between the imaginary line passing tangentially thorough both femoral condyles and horizontal plane.

The difference between these two measured angles defined the anteversion angle and the angular deviation from the normal range indicated the severity of the FAV in our study. The same procedure was done on the front hip and the obtained angles were studied in both osteoarthritic and control group. The anteversion angles were analyzed with respect to variables such as age, sex and severity of degenerative joint disease.

Inclusion benchmarks were restricted to all adult patients aging 20 years of age or more who filled and signed the written informed consent. Patients with any acquired or congenital musculoskeletal deformity of the hip and lower limb, any history of trauma leading to this situation or orthopedic surgery on lower limb, as well as patients with acquired or congenital infectious,