What is the reasoning behind choosing total hip arthroplasty (THA) versus partial hip arthroplasty (PHA) for treating displaced femoral neck fractures?

Reasoning Behind THA vs PHA in Femoral Neck Fractures

Total hip arthroplasty (THA) should be chosen over partial hip arthroplasty (PHA/hemiarthroplasty) for healthy, active, independent older adults without cognitive dysfunction who have displaced femoral neck fractures, while hemiarthroplasty is preferred for frail patients with limited mobility or significant comorbidities. 1

Patient Selection Algorithm

The decision between THA and hemiarthroplasty hinges on specific patient characteristics that predict functional benefit versus complication risk:

THA is Indicated For:

• Healthy, active, independent older individuals without cognitive dysfunction 1
• Patients with life expectancy >4 years 2
• Patients younger than 80 years 2
• Mobile patients who lived independently before fracture 3

Hemiarthroplasty is Indicated For:

• Frail elderly patients with limited baseline mobility 1, 4
• Patients older than 80 years with shorter life expectancy 2
• Patients with significant cognitive dysfunction 1
• Patients requiring shorter operative time and lower dislocation risk 4

Functional Outcomes Supporting THA

The evidence demonstrates clear functional superiority of THA in appropriately selected patients:

• THA patients walk significantly farther (mean 2.23 miles vs 1.17 miles for hemiarthroplasty) 3
• Better Oxford hip scores (18.8 for THA vs 22.3 for hemiarthroplasty, where lower is better) 3
• Superior Harris Hip Score and Quality of Life (SF-36) compared to hemiarthroplasty 2
• Lower reoperation rates with THA 2
• Acetabular erosion is a major problem with hemiarthroplasty, occurring in 20 of 32 living patients at follow-up, with 5 requiring or indicating revision 3

Complication Trade-offs

The AAOS acknowledges that improved function with THA comes at the risk of increased complications, which is why the recommendation was downgraded from strong to moderate despite strong evidence for functional benefit 5:

Dislocation Risk:

• THA has higher dislocation risk in the first 4 years after surgery 2
• In one randomized trial, 3 THA hips dislocated vs 0 hemiarthroplasty hips 3
• After 4 years, dislocation rates equalize between THA and hemiarthroplasty 2
• Modern advances including larger femoral heads and improved bearing surfaces may be reducing dislocation rates 6

Other Complications:

• No difference in mortality or infection rates between THA and hemiarthroplasty 2
• THA has increased surgical time and blood loss compared to hemiarthroplasty 5

Economic Considerations

Long-term cost analysis favors THA because the additional cost of treating failures of hemiarthroplasty in patients who survive 2 years or longer exceeds the initial higher cost of THA 6

Technical Considerations

Regardless of whether THA or hemiarthroplasty is chosen:

• Cemented femoral stems are strongly recommended to improve hip function, reduce residual pain, and decrease periprosthetic fracture risk 5, 1, 4
• For hemiarthroplasty, unipolar or bipolar designs are equally beneficial 5

Common Pitfalls to Avoid

• Do not automatically default to hemiarthroplasty based solely on age without assessing functional status and independence 1
• Do not choose THA for frail patients simply because they are younger than 80 years—functional status matters more than chronological age 1, 2
• Do not underestimate acetabular erosion risk with hemiarthroplasty in active patients, as this leads to significant revision burden 3
• Do not use uncemented stems in elderly hip fracture patients due to increased periprosthetic fracture risk 5