Neck of femur fracture
Citation, DOI & article data
Neck of femur fractures (NOF), a.k.a. femoral neck fractures, are common injuries sustained by older patients who are both more likely to have 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.
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
trace Shenton’s line
assess for symmetry, particularly note lesser trochanter (may indicate external rotation)
Treatment and prognosis
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.
type 1 (transphyseal): ~90% risk of AVN
type 2 (subcapital): ~50% risk of AVN
type 3 (basicervical/transcervical): ~25% risk of AVN
type 4 (intertrochanteric): ~10% risk of AVN
As a general rule, internal fixation is recommended for young, otherwise, fit patients with small risk for AVN. While prosthetic replacement is reserved for fractures with a high risk of AVN and the elderly 10.
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