Neck of femur fracture

Last revised by Mohammad Taghi Niknejad on 14 Mar 2024

Neck of femur (NOF) fractures, or femoral neck fractures, are common injuries sustained by older patients who are more likely to have both unsteadiness of gait and reduced bone mineral density, predisposing to fracture. Elderly osteoporotic women are at greatest risk.

The incidence of femoral neck fractures is increasing as the proportion of the elderly population in many countries increases 4. In patients aged between 65 and 99 years, femoral neck and intertrochanteric fractures occur with approximately the same frequency 7. Hip fractures can be divided into intracapsular and extracapsular fractures with 60% being intracapsular and of that 80% are displaced 20

Femoral neck fractures are a subset of proximal femoral fractures. The femoral neck is the weakest part of the femur.

Since disruption of blood supply to the femoral head is dependent on the type of fracture and causes significant morbidity, the diagnosis and classification of these fractures is important. There are three types:

  • subcapital: femoral head/neck junction

  • transcervical: midportion of femoral neck

  • basicervical: base of femoral neck

Subcapital and transcervical fractures are considered intracapsular fractures. While there is disagreement in the literature as to whether basicervical fractures are truly intracapsular or extracapsular, they should usually be treated like extracapsular fractures 14.

Subcapital fractures are graded by the Garden classification of hip fractures.

Most commonly 9:

  • falls in the elderly

  • significant trauma (e.g. motor vehicle collisions) in younger patients

In elderly patients, the mechanism of injury varies from falls directly onto the hip to a twisting mechanism in which the patient’s foot is planted and the body rotates. There is generally deficient elastic resistance in the fractured bone 8.

The mechanism in young patients is predominantly axial loading during high force trauma 9, with an abducted hip during injury causing a neck of femur fracture and an adducted hip causing a hip fracture-dislocation.

Plain radiograph (sensitivity 93-98%) is the first-line investigation for suspected NOF fractures. In patients with a suspected occult NOF fracture, MRI (sensitivity 99-100%) is recommended by many institutions as the second-line test if available within 24 hours, with CT or nuclear medicine bone scan third-line 17,18. There is some evidence that thin-slice MDCT is as sensitive as MRI 19.

  • Shenton’s line disruption: loss of contour between normally continuous line from medial edge of femoral neck and inferior edge of the superior pubic ramus

  • lesser trochanter is more prominent due to external rotation of femur

  • femur often positioned in flexion and external rotation (due to unopposed iliopsoas)

  • asymmetry of lateral femoral neck/head

  • sclerosis in fracture plane

  • smudgy sclerosis from impaction

  • bone trabeculae angulated

  • non-displaced fractures may be subtle on x-ray

  • AP pelvis and lateral hip should be viewed because pelvic fractures can mimic clinical features of hip fracture

  • trace Shenton’s line

  • assess for symmetry, particularly note lesser trochanter (may indicate external rotation)

  • bone trabeculae

  • sclerosis

  • smudge

Point of care ultrasound may be utilized as an adjunct to radiography to facilitate timely diagnosis of femoral neck fractures and may be subsequently employed to deliver prompt relief of pain by delivery of a suitable nerve block (e.g. fascia iliaca compartment block).

Long and short axis views of the femoral neck with the overlying anterior synovial recess, femoral head and acetabulum and the greater and lesser trochanters are obtained with the following features consistent with a femoral neck fracture:

  • cortical discontinuity 22

    • breach in the normally smooth cortical surface

    • commonly associated with a hypoechoic fluid collection representing hematoma 21

  • joint effusion

    • representing hemarthrosis in the context of an intra-articular fracture

    • expansion of the anterior synovial recess with separation of the anterior and posterior synovial reflections by a collection of variable echogenicity

  • iliopsoas hematoma 23

Treatment of neck of femur fractures is important. Significant complications such as avascular necrosis and non-union are very common without surgical intervention. The treatment options include non-operative management, internal fixation or prosthetic replacement.

Internal fixation can be performed with multiple pins (cannulated screws), intramedullary hip screw (IHMS), crossed screw-nails or compression with a dynamic screw and plate 9. Replacing the femoral head is achieved with either hemiarthroplasty or total hip arthroplasty

In patients receiving hemiarthroplasty, evidence shows that cemented hemiarthroplasty has fewer prosthesis-related complications than uncemented prostheses, despite similar rates of mortality 20

The high morbidity and mortality associated with hip and pelvic fractures after trauma has been well documented. Prognosis is varied but is complicated by advanced age, as hip fractures increase the risk of death and major morbidity in the elderly 5,6,8.

The risk of osteonecrosis depends on the type of fracture. The Delbet classification, originally described by Delbet in adults but more frequently used with reference to pediatric fractures, correlates with the risk of osteonecrosis 12,13:

  • type 1 (transphyseal): ~90% risk of osteonecrosis

  • type 2 (transcervical): ~50% risk of osteonecrosis

  • type 3 (basicervical): ~25% risk of osteonecrosis

  • type 4 (intertrochanteric): ~10% risk of osteonecrosis

As a general rule, internal fixation is recommended for young, otherwise, fit patients with a small risk for osteonecrosis. While prosthetic replacement is reserved for fractures with a high risk of osteonecrosis and the elderly 10.

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