Hip fractures, Garden and AO classification, DHS vs IMN, hemiarthroplasty vs THA, timing and perioperative optimisation

Overview

Femoral neck fractures represent >50% of all hip fractures and constitute approximately 20% of the operative orthopaedic trauma workload. They carry a ~10% 30-day mortality and ~25-30% one-year mortality in elderly patients, conferring a combined health and care cost exceeding that of stroke or myocardial infarction. The majority are intracapsular, occurring in osteoporotic elderly women following low-energy falls. Displacement is the single most important determinant of management, underpinning both the Garden and AO/OTA classification systems.

Anatomy and Biomechanical Considerations

Blood Supply to the Femoral Head

The femoral head receives its dominant blood supply via the medial femoral circumflex artery (MFCA), whose retinacular branches ascend along the femoral neck within the synovial lining. The superior retinacular artery (lateral epiphyseal artery) is traditionally cited as the dominant contributor; the inferior retinacular artery has more recently been shown to also provide significant perfusion with a consistent anatomical course. Both are vulnerable to disruption with displacement or malreduction. The artery of the ligamentum teres (obturator artery) contributes minimally in adults. Intracapsular haematoma may elevate intra-articular pressure and compromise retinacular flow, the rationale for capsulotomy/decompression, though benefit remains unproven and controversial.

Biomechanical Relevance to Fixation

The femoral neck is predominantly cortical with limited cancellous bone, screws will settle until abutting intact cortex, so positioning is critical. Fixation failure occurs through:

• Varus collapse (inadequate medial buttress)
• Posterior comminution/retroversion
• Screw cut-out (tip-apex distance >25 mm, poor positioning)

Higher Pauwels angles generate predominantly shear forces, increasing failure risk with standard cannulated screws.

Classification Systems

Garden Classification (1961)

Based on the relationship of trabecular lines in the femoral head to those in the acetabulum on the AP radiograph alone.

Practical grouping:

• Stable: Grades I and II (non-displaced/impacted) → internal fixation
• Unstable: Grades III and IV (displaced) → arthroplasty in elderly; ORIF in young

The four-grade system has poor inter-observer reliability. The binary collapse (non-displaced vs displaced) has superior reproducibility and greater clinical utility, some authors advocate abandoning the four-grade system in favour of this binary classification.

Examination pitfall: Garden IV fractures paradoxically show near-normal trabecular alignment on AP radiograph because the head has completely rotated. Grades III and IV are managed identically in clinical practice.

AO/OTA Classification

Proximal femoral fractures (segment 31):

Femoral neck (31-B) subgroups:

The AO system additionally captures fracture location. Its inter-observer reliability is comparable to binary Garden grouping. Both systems are examinable; the Garden classification remains more widely used in clinical communication.

Pauwels Classification

Based on the angle of the fracture line relative to the horizontal on AP radiograph:

Pauwels III ("vertical") fractures are most relevant in young patients where head preservation mandates internal fixation.

Clinical Assessment

History

• Mechanism: low-energy fall (elderly/osteoporotic) vs high-energy trauma (young)
• Premorbid mobility and walking aids
• Cognitive function (influences arthroplasty type selection)
• Comorbidities and anticoagulation status
• Pre-injury ipsilateral hip symptoms or arthritis

Examination

• Displaced fracture: shortened, externally rotated limb
• Garden I (impacted): near-normal posture; groin pain on axial load or log roll; may be walking
• Neurovascular assessment of lower limb
• Systematic medical evaluation for modifiable perioperative risk
• Skin assessment (pressure area risk)

Occult Fractures

Approximately 4% of patients present with hip pain, normal plain radiographs, and an occult fracture. Investigate with MRI (gold standard; detects trabecular injury within 24 hours) or CT (more accessible but lower sensitivity). Bone scan sensitivity is delayed 48-72 hours post-injury.

Investigations

Non-operative Management

Reserved for approximately 5-8% of patients:

• Terminal illness with prohibitive surgical risk
• Non-ambulatory, minimal-pain patients
• Prohibitive anaesthetic risk where surgical benefit cannot be justified

When non-operative: fascia iliaca or PENG block analgesia, pressure area nursing, early palliative input, family discussions. Touch-down weight bearing 6-8 weeks if managed without surgery.

Garden I fractures: historically managed non-operatively, but up to 30% of valgus-impacted fractures displace without fixation, operative fixation is now recommended for the majority of Garden I and II fractures.

Operative Management

Decision Framework

$$\text{Non-displaced (Garden I/II)} \rightarrow \text{Internal fixation (all ages)}$$

$$\text{Displaced (Garden III/IV), elderly} \rightarrow \text{Arthroplasty (HA or THA)}$$

$$\text{Displaced (Garden III/IV), young} \rightarrow \text{Urgent ORIF (head preservation)}$$

Operative Management by Patient Profile

Internal Fixation: Indications and Principles

Indications: Garden I and II (all patients); Garden III/IV in young patients where head preservation is the priority.

Technical principles:

• Tip-apex distance (TAD) should be $<25\ \text{mm}$ to minimise cut-out:

$$\text{TAD} = d_{AP} + d_{LAT}$$

where $d_{AP}$ and $d_{LAT}$ are the distances from the screw tip to the femoral head apex on AP and lateral views respectively.

• Inferior and posterior screw placement provides the best cortical buttress against displacement
• Avoid starting point distal to the lesser trochanter (increased subtrochanteric peri-implant fracture risk)
• Varus malreduction is strongly associated with fixation failure, anatomical or slight valgus reduction preferred
• Internal fixation carries up to 30% failure rate in displaced fractures; higher with sagittal plane deformity (retroversion)
• Decompression of intracapsular haematoma to reduce AVN risk: rationale exists but benefit is unproven and controversial

Hemiarthroplasty (HA): Indications and Principles

Indications: Displaced femoral neck fractures in elderly patients with lower functional demands or cognitive impairment (dementia, Parkinson disease, unable to comply with dislocation precautions).

Total Hip Arthroplasty (THA): Indications and Principles

Indications: Active, independently mobile elderly patients with displaced femoral neck fractures; pre-existing ipsilateral hip OA or RA; patients likely to outlive a hemiarthroplasty.

HEALTH Trial (NEJM 2019): Among patients ≥50 years with displaced femoral neck fractures, THA did not result in significantly better functional outcomes (WOMAC) than HA at 24 months in an unselected elderly cohort. THA was associated with a higher rate of re-operation at 2 years (mainly dislocation). This supports selective rather than universal application of THA.

AAOS CPG: THA more beneficial than HA in properly selected patients with displaced femoral neck fractures (moderate recommendation strength).

Timing of Surgery

Key principle: The 48-hour threshold for mortality benefit is well-supported and should prompt expedited theatre access. ASA grade predicts operative risk, most modifiable factors can be optimised within 24 hours without unacceptable delay.

ANZ context: The ANZHFR tracks 48-hour surgical compliance as a key performance indicator, alongside 30-day mortality, early mobilisation, bone protection prescribing, and falls prevention.

Complications

Fracture-Related Complications

Arthroplasty-Specific Complications

General Complications

• Mortality: 30-day ~10%; 1-year ~25-30%
• Delirium: 15-50%; predicted by pre-existing cognitive impairment, pain, and anaesthetic type
• DVT/PE: DVT rates up to 50% without prophylaxis; LMWH or aspirin standard (CRISTAL trial: aspirin non-inferior to enoxaparin for symptomatic VTE in hip/knee arthroplasty)
• Contralateral hip fracture: ~10% at 5 years, DEXA, falls prevention, and osteoporosis treatment essential
• Pressure injuries, pneumonia, UTI: reduced by expedited surgery and early mobilisation

Outcomes and Prognosis

Prognostic predictors:

• Pre-fracture mobility and cognitive status are the strongest predictors of postoperative function
• ASA grade and Charlson Comorbidity Index (CCI) predict perioperative mortality
• Age alone should not preclude surgical intervention

Paediatric Considerations

Femoral neck fractures in children are rare, high-energy injuries with distinctly different management.

Examination Summary

Sources

• AAOS guidelines (American Academy of Orthopaedic Surgeons)
• AOA (Australian Orthopaedic Association) position statements
• Cochrane Library reviews