Femoral neck abnormalities

Last updated: March 14, 2023

Summary

Femoral neck abnormalities are axial malalignments of the femoral neck involving the caput-collum-diaphyseal angle and the femoral angle of anteversion. Four common femoral version abnormalities are discussed here: coxa vara, coxa valga, femoral anteversion, and femoral retroversion. Clinical features include an abnormal gait and pain with prolonged weight-bearing. Some abnormalities may resolve spontaneously. However, severe cases require surgical correction. Common complications include secondary arthrosis and femoroacetabular impingement.

Overview

Definition: axial malalignments of the femoral neck involving the caput-collum-diaphyseal angle (CCD angle) and the angle of anteversion
Femoral neck axis: a line that equally divides the femoral neck through the center of the femoral head ^[1]
Caput-collum-diaphyseal angle (CCD angle) ^[1]
- The angle formed by the main axis of the femoral neck and the longitudinal axis of the femoral shaft (coxa norma)
- Normal angle ^[2]
  - ∼ 125° in adults
  - ∼ 150° in newborns
Femoral anteversion angle ^[3]^[4]
- The angle formed by the longitudinal axis of the femoral neck and the transverse axis of both femoral condyles of the distal femur
- Indicates the normal torsion of the femur
- Normal angle
  - 8–15° in adults
  - 30–40° in newborns
Hilgenreiner epiphyseal angle ^[5]
- The angle formed by the intersection of a line drawn from the triradiate cartilages (Hilgenreiner line) and another line drawn through the capital femoral physis
- Used to measure the severity of femoral deformities
- Normal angle: ∼ 25°

Femoral neck anomalies are initially diagnosed using plain x-ray.

Femoral neck abnormalities Femoral anteversion angle

Coxa vara

Definition: a deformity of the proximal femur due to a decreased femoral neck-shaft angle (< 120°), with shortening and thickening of the femoral neck

Overview of coxa vara ^[5]^[6]
	Congenital	Developmental	Acquired
Etiology	Present at birth Typically occurs with other skeletal deformities or as part of a syndrome Skeletal deformities Spondyloepiphyseal dysplasia Multiple epiphyseal dysplasia Cleidocranial dysplasia Proximal femoral focal deficiency Fibular deficiency Congenital short femur Associated syndromes Femoral facial syndrome Camptodactyly arthropathy coxa vara pericarditis syndrome	Develops during the perinatal period and may progress during childhood	Secondary to metabolic, neoplastic, or traumatic conditions Infection (e.g., septic arthritis, osteomyelitis) Legg-Calvé-Perthes disease Osteopetrosis Slipped capital femoral epiphysis (SCFE) Fibrous dysplasia Paget disease of bone Vitamin D-dependent rickets Trauma (e.g., fracture of the femoral neck or trochanter, epiphyseal injuries) Vascular injury to the femoral growth plate (e.g., avascular necrosis of the femoral head) Osteomalacia Osteogenesis imperfecta
Clinical features	Unilateral involvement (typically in the subtrochanteric area) Abductor muscle weakness Limb length discrepancy (shorter leg on the affected side) Associated with: Femoral retroversion Knee valgus	Presents by walking age (2–3 years of age) Bilateral involvement Trendelenburg gait Limited hip abduction and internal rotation Positive Trendelenburg sign: The hip is abducted when reduced.	Clinical features of the underlying disorder Typically, unilateral involvement Limb length discrepancy
Diagnostics	AP and lateral x-rays Reduced angle between femoral neck and shaft Vertically orientated and widened physis Overgrowth of the greater trochanter Small fractures may be present medially. MRI To assess the hip joint cartilage and labrum Findings: widened physis, bone marrow edema, and expanded cartilage tissue	AP and lateral x-rays Triangular shaped ossification of the femoral neck Changes in the femoral head and acetabulum Widening of the physis CT/MRI: presurgical planning	Depends on the underlying disorder (e.g., laboratory tests to diagnose rickets, vitamin D deficiency) AP and lateral x-rays: reduced angle between femoral neck and shaft
Treatment	Expectant management Hilgenreiner epiphyseal angle < 45° Asymptomatic patients with Hilgenreiner epiphyseal angle of 45°–60° Surgery: valgus derotation osteotomy (at the subtrochanteric or intertrochanteric level) ^[7] Progressive or severe deformities Symptomatic patients with a Hilgenreiner epiphyseal angle of 45°–60° A Hilgenreiner epiphyseal angle > 60°		Depends on the underlying disorder
Complications	Persistence of abnormal gait and functional impairment Hip dysplasia Hip subluxation Premature closure of the femoral physis Pseudoarthrosis Osteoarthritis

Coxa vara

Coxa valga

Definition: deformity of the femur due to an increased femoral neck-shaft angle (> 140°)

Overview of coxa valga ^[6]^[8]
	Congenital	Secondary
Etiology	Seen in newborns or toddlers Possible genetic predisposition	Low axial load Neuromuscular disorders (e.g., cerebral palsy, meningomyelocele) Skeletal dysplasias (e.g., hip dysplasia, Turner syndrome) Trauma leading to arrest of the growth plate
Clinical features	Usually asymptomatic Typically bilateral Groin pain due to long periods of weight-bearing Limited hip abduction In some cases, a positive Trendelenburg sign	Depend on the underlying disease Typically unilateral Limited hip abduction Positive Trendelenburg sign
Diagnostics	AP x-ray of the hips: increased angle between femoral neck and shaft
Treatment	Spontaneous normalization can be expected once skeletal development is complete. Physiotherapy Persistent cases: varus derotation osteotomy (VDRO)	Treatment of underlying disease Physiotherapy Surgical correction may be considered.
Complications	Secondary arthrosis

Coxa valga

Femoral anteversion

Definition: a forward rotation of the femoral neck in relation to the femoral condyles due to an increased femoral anteversion angle
Epidemiology ^[6]^[9]
- Occurs between 3–6 years of age
- More common in girls
Etiology
- Physiologic (present in up to 10% of children)
- Congenital
  - Genetic predisposition
  - Abnormal intrauterine position of the fetus
- Trauma (e.g., femur fracture)
Clinical features
- Typically bilateral
- Hip extension abnormalities
  - Increased internal rotation
  - Limited external rotation
- Bowing of the legs
- In-toeing gait
- Hip or thigh pain (due to long periods of weight-bearing)
- Often associated with coxa valga
Diagnostics
- Usually, a clinical diagnosis based on physical examination findings
- Imaging
  - X-ray
  - CT/MRI
Treatment
- Expectant management
  - In cases of physiologic anteversion
  - Usually resolves spontaneously by 10 years of age
- Surgery: intertrochanteric derotation osteotomy
  - Severe gait deformities
  - Symptoms that impair normal gait
  - Children 8–10 years of age with impaired gait
Complications: femoroacetabular impingement (an abnormal contact between the acetabulum and proximal femur during terminal hip flexion, which leads to damage of the articular cartilage and acetabular labrum) ^[10]

Toddlers that repeatedly or easily stumble may have femoral anteversion.

Femoral anteversion and retroversion In-toeing

Femoral retroversion

Definition: a backward rotation of the femoral neck in relation to the femoral condyles due to a decreased femoral anteversion angle
Etiology ^[6]^[9]
- Physiologic
- Congenital
  - Genetic predisposition
  - Abnormal intrauterine position of the fetus
- Trauma (e.g., femur fracture)
Clinical features
- Usually bilateral
- Usually late walkers
- Hip extension abnormalities
  - Increased external rotation
  - Limited internal rotation
- Out-toeing gait
- Hip or thigh pain (due to long periods of weight-bearing)
- Flat feet
- Often associated with tibial torsion
Diagnostics
- Usually, a clinical diagnosis based on physical examination findings
- Imaging
  - X-ray
  - CT/MRI
Treatment
- Orthotics
- Physiotherapy
- Splinting or casting of the legs (to stretch and improve internal rotation)
- Surgery: intertrochanteric derotation osteotomy
Complications ^[10]
- Femoroacetabular impingement
- Hip osteoarthritis

Femoral anteversion and retroversion Out-toeing

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