Hip fractures

Notes

Definition

A hip fracture is a bony injury of the proximal femur typically occurring in the elderly. 

Older patients are more likely to have gait unsteadiness and reduced bone mineral density, predisposing to fracture. 

It is a common serious injury in older people, costing the NHS and social care £1 billion per year.

Risk factors include:

  • Increasing age
  • Osteoporosis
  • Low muscle mass
  • Steroids 
  • Smoking 
  • Excess alcohol intake

Basic anatomy

The proximal femur consists of a head, neck, trochanters (greater and lesser) & shaft. It is the largest bone in the human body.

The inter-trochanteric line lies on the anterior surface of the femoral neck, running between the trochanters. It demarcates the inferior attachments of the hip capsule.

 

Hip capsule 

The capsule of the hip is attached proximally to margins of acetabulum and transverse acetabular ligament. Distally, to the inter-trochanteric line, bases of greater & lesser trochanters and to the femoral neck posteriorly (approx. 1/2 inch from the trochanteric crest). It contains the retinacular vessels - a major component of the blood supply to the femoral head.

Blood supply to the femoral head

The femoral head receives blood from three sources:

  1. Retinacular vessels - main blood supply. Originates from an extra-capsular arterial ring, supplied by medial and lateral circumflex vessels (profunda femoris A.). Reinforced by the superior and inferior gluteal arteries (internal iliac A.).

  1. Foveal artery - not a major source. During skeletal development, supplies the epiphysis with a small amount of blood. Said to become obliterated in adult life (ligamentum teres).
  2. Metaphyseal vessels - not a major source. After skeletal maturity, metaphysical arteries also contribute blood to the femoral head.

 

Blood supply to the femoral head and neck

Classification

Hip fractures may be categorised as either intra- or extra-capsular, depending on their location in relation to the inter-trochanteric line.

  • Above = intra-capsular
  • Below = extra-capsular

The type of fracture determines the likelihood of disruption to the blood supply of the femoral head. Broadly speaking, intra-capsular fractures are associated with a higher-risk of disruption, owing to the close proximity of the retinacular vessels.

Garden's classification (intra-capsular fractures)

Intra-capsular fractures are further sub-classified according to Garden’s classification. 
There are four types.

  • Type I - Incomplete, impacted in valgus
  • Type II - Complete, undisplaced
  • Type III - Complete, partially displaced
  • Type IV - Complete, completely displaced

With type 1 & 2 there is minimal displacement, and therefore a lessened risk of disruption to the femoral head blood supply. Conversely, with type 3 & 4, where there is much greater displacement, there is substantially higher risk. 

Classification is based on the integrity of the trabecular lines in an AP projection. It is used to guide management.

Aetiology

In the elderly, hip fractures are normally caused by falls.

The mechanism varies from direct falls onto the affected hip, to twisting, in which the patient’s foot is planted and the body rotates. Bones are typically osteopaenic (reduced bone density) and also deficient in elastic reserve (i.e. they are very brittle).

In younger patients, hip fractures are more commonly the result of major trauma (e.g. motor vehicle accidents), or in patients with gait disturbance (e.g. in multiple sclerosis) in which they are at increased risk of falls. Certain medications, such a prolonged corticosteroid use, can also predispose to osteopaenia.

Clinical features

Hip fractures are diagnosed radiologically, but may be suspected clinically.

Patients usually describe a fall or recent trauma; it is unusual for fractures to occur with no precipitating trauma. High-energy trauma (e.g. motor vehicle accident) is more common in younger patients, although accounts for only a small percentage (2-3%) of all hip fractures.

It is important to elucidate why an individual may have fallen; whether the fall was mechanical in nature (e.g. slipped on a wet floor) or if the event was precipitated (e.g. MI, stroke, chest infection, UTI etc.)

Patients typically report an inability to bear weight and pain in the affected side, with a reduced range of movement.

Symptoms

  • Hip / knee pain
  • Inability to bear weight
  • Limited range of motion

Signs

  • Bony tenderness over affected hip
  • Shortened / externally rotated leg (only present if significant displacement)

Investigations

A hip fracture is a radiological diagnosis, although additional investigations can be used to aid the diagnosis and look for complicating pathology.

Bedside

  • Observations
  • Urine dip
  • ECG
    • Required pre-operatively
    • ACS, undiagnosed arrhythmia  (e.g. AF)

Bloods

  • FBC
  • U&E
  • CRP
  • Clotting
  • Group & Save x 2

Imaging

  • CXR: required pre-operatively
  • Plain films: XR pelvis, hip, femur + knee (affected side); need to image the entire length of femur
  • MRI/CT: if plain films are inconclusive, to rule out occult fracture
  • Cardiac echo: if new murmur is auscultated or abnormal ECG, often required pre-operatively

X-ray interpretation

Shenton’s line - an imaginary curved line drawn along the inferior border of the superior ramus, along the inferomedial border of the proximal femur. It should be continuous and smooth.

Management

Most hip fractures are treated surgically, unless there are significant co-morbidities restricting surgical intervention. Surgical management differs between intra- and extra- capsular fractures.

In rare cases, conservative treatment can involve traction, bed rest or restricted mobilisation. Outcomes are often very poor in these patients.

NICE guidelines recommend surgery to be performed on the day of, or the day after, admission. The aim is to allow patients to fully weight bear (without restriction) in the immediate postoperative period; however, this often is not possible.

Surgical management is generally as follows:

  • Displaced intra-capsular fractures (e.g. Gardens III/IV) - NICE recommends total hip replacement (THR) for fit patients; or hemi-arthoplasty for patients with significant comorbidity. 
  • Minimally or non-displaced intracapsular fractures (e.g. Gardens I/II) - usually treated with cannulated hip screws (often 2 or 3).
  • Extra-capsular fractures - either a dynamic hip screw (DHS) or intra-medullary (IM) nail are utilised. DHS are unique in the fact that they allow the fracture ends to ‘slide’; this is thought to promote bone healing.

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