How do I determine if an adult patient (elderly with possible osteoporosis or younger with direct trauma) has a lateral femur fracture?

Determining a Lateral Femur Fracture in Adults

Initial Imaging Approach

Plain radiography (anteroposterior and lateral views of the femur) is the first-line diagnostic modality and provides 90-95% sensitivity for detecting femoral fractures. 1

• Obtain standard AP and lateral radiographs of the entire femur, including the hip and knee joints 1
• Plain films are sufficient for diagnosis in the vast majority of cases and should be performed immediately when fracture is suspected 1

CT Imaging for Complex Cases

CT without contrast should be obtained when plain radiographs are equivocal or when detailed assessment of fracture pattern, comminution, and surgical planning is needed. 1

• CT is particularly valuable for evaluating the supracondylar region where fracture lines may be subtle on plain films 1
• Use CT to assess the degree of comminution and intra-articular extension in distal femur fractures 1

MRI Considerations

MRI is reserved only for cases where occult fracture is suspected despite negative plain films, or when soft-tissue pathology needs evaluation—it is not required for routine femoral fracture diagnosis. 1

• MRI is not part of the standard workup for clinically obvious lateral femur fractures 1
• Consider MRI only when clinical suspicion remains high but radiographs and CT are negative 1

Critical Distinction: Traumatic vs. Atypical Femoral Fractures

Traumatic Supracondylar Fractures (Most Common)

Any fracture occurring after significant trauma (fall from height, motor vehicle collision, direct blow) is classified as a traumatic fracture and follows standard orthopedic management. 1

• Traumatic supracondylar femur fractures typically show comminution and occur at or within the supracondylar flare 1
• These fractures are managed with osteosynthesis in most cases, though prosthetic replacement may be considered in elderly patients with severe comminution and poor bone quality 2

Atypical Femoral Fractures (Rare, Specific Criteria Required)

Atypical femoral fractures occur with minimal or no trauma and are located between the lesser trochanter and the distal supracondylar flare—fractures at the supracondylar region itself are excluded from this definition. 1

The ASBMR Task Force requires ALL of the following major features to diagnose an atypical femoral fracture:

• Minimal or no trauma (fall from standing height or less) 1
• Transverse or short oblique orientation originating at the lateral cortex 1
• Non-comminuted or minimally comminuted pattern 1
• Location between lesser trochanter and supracondylar flare (NOT in the supracondylar region) 1
• Complete fractures extend through both cortices; incomplete fractures involve only the lateral cortex 1

Minor features that support the diagnosis include:

• Localized periosteal or endosteal thickening of the lateral cortex ("beaking") 1
• Prodromal dull or aching groin/thigh pain for weeks to months before fracture 1
• History of long-term bisphosphonate therapy (≥3-5 years), denosumab, or romosozumab use 1
• Bilateral involvement (occurs in up to 30% of cases—always image the contralateral femur) 1

Risk Stratification by Patient Population

Elderly Patients with Suspected Osteoporosis

In patients ≥65 years with low-energy trauma, assess for underlying osteoporosis after fracture diagnosis, as this confirms skeletal fragility regardless of bone mineral density. 3

• A fragility fracture (from fall from standing height or less) confirms skeletal fragility even if BMD T-score is >-2.5 3
• The relative risk of a subsequent fracture increases approximately 2-fold after any initial fracture 3
• Hip fracture carries the highest imminent fracture risk, with hazard ratios of 46.7 in women and 92.4 in men aged 40 years 3
• Initiate fracture liaison services and consider pharmacologic treatment immediately after fracture diagnosis 4

Younger Adults with Direct Trauma

In younger patients with high-energy trauma, focus on fracture pattern characterization for surgical planning rather than metabolic bone disease evaluation. 1

• Standard imaging with plain radiographs ± CT is sufficient 1
• Osteoporosis screening is not indicated in premenopausal women or men <50 years unless secondary causes are present 3

Common Pitfalls to Avoid

Do not diagnose an atypical femoral fracture based solely on radiographic appearance—the mechanism of injury (minimal/no trauma) is mandatory. 1

• A transverse lateral cortex fracture occurring after significant trauma is NOT atypical, regardless of appearance 1
• Supracondylar fractures are excluded from the atypical fracture definition by anatomic location 1
• Always obtain bilateral femur imaging when an atypical fracture is confirmed, as 30% are bilateral 1

Do not rely on bone mineral density alone to assess fracture risk—advancing age is a stronger determinant than BMD. 3

• Elderly patients have higher fracture rates than younger adults with identical BMD due to declining bone quality and increased fall risk 3
• Clinical risk factors (age, prior fracture, low body weight, parental hip fracture history, smoking, excess alcohol) must be integrated with BMD 3