For an 85‑year‑old woman with a displaced sub‑capital femoral neck fracture, type 2 diabetes mellitus and hypertension, should I use a cemented unipolar or bipolar hemiarthroplasty?

Bipolar vs Unipolar Hemiarthroplasty for Displaced Femoral Neck Fracture

For your 85-year-old patient with a displaced subcapital femoral neck fracture, either unipolar or bipolar cemented hemiarthroplasty is appropriate, as they produce equivalent clinical outcomes in mortality, morbidity, and quality of life. 1

Primary Recommendation Based on Guidelines

The American Academy of Orthopaedic Surgeons (AAOS) 2022 guidelines provide a moderate strength recommendation that unipolar or bipolar hemiarthroplasty can be equally beneficial for displaced femoral neck fractures. 1 This means you should generally follow this recommendation but remain sensitive to patient-specific factors and cost considerations.

Key Evidence Supporting Equivalence

Functional Outcomes and Quality of Life

• Multiple high-quality randomized trials demonstrate no significant differences in hip function scores (Harris Hip Score, Oxford Hip Score) between unipolar and bipolar prostheses at 12-month follow-up. 2, 3, 4
• Health-related quality of life (EQ-5D scores) shows no significant difference between groups, though one study showed a trend toward better quality of life with bipolar at 4 months (0.62 vs 0.54, p=0.06). 3
• Walking speed and endurance measured by Six-Minute Walk tests are equivalent between both prosthesis types. 4

Complication Rates

• Dislocation rates are equivalent between unipolar and bipolar hemiarthroplasty. 2
• Postoperative medical and wound complications occur at similar rates in both groups. 2
• Revision surgery rates show no significant differences between the two implant types. 2

The Acetabular Erosion Consideration

Common pitfall: Acetabular erosion is often cited as a reason to prefer bipolar prostheses, but its clinical significance is questionable.

• One randomized trial found 20% acetabular erosion with unipolar versus 5% with bipolar at 12 months (p=0.03). 3
• However, this radiographic finding showed only trends toward worse outcomes (not statistically significant): Harris Hip Score 70.4 vs 79.3 (p=0.09) and EQ-5D 0.48 vs 0.63 (p=0.13). 3
• At 36-month follow-up, another study found no functional differences despite theoretical concerns about acetabular wear. 2

Practical Decision Algorithm

Use either unipolar or bipolar based on these factors:

Favor Unipolar When:

• Cost is a significant institutional concern (unipolar is substantially less expensive). 5, 4
• Patient has limited pre-injury mobility and is less active. 5
• Patient has severe osteopenia and is at high risk for periprosthetic fracture (shorter operative time with unipolar). 5

Consider Bipolar When:

• Patient has better pre-injury functional status and may benefit from theoretical acetabular preservation. 3
• Institutional cost difference is negligible.
• Patient or family preference after shared decision-making.

Essential Technical Requirements (Regardless of Choice)

Both prostheses MUST be cemented in your 85-year-old patient with likely osteoporosis. The AAOS provides a strong recommendation for cemented femoral stems in elderly patients undergoing arthroplasty for femoral neck fractures. 1, 6, 7 Cemented fixation:

• Improves hip function. 6
• Reduces residual pain. 6
• Decreases periprosthetic fracture risk in osteoporotic bone. 7

Surgical Approach

• Posterior approach with meticulous capsular repair minimizes dislocation risk. 6, 8
• No outcome differences exist between surgical approaches in the general population, but avoid posterior approach if your patient has neurological or cognitive impairment due to increased dislocation risk. 6, 8

Perioperative Management Priorities

• Surgical timing: Operate within 24-48 hours of admission for better outcomes. 1
• Anesthesia: Either spinal or general anesthesia is appropriate (strong recommendation). 1, 7
• Tranexamic acid: Administer at surgery start to reduce blood loss. 7
• Multimodal analgesia: Include preoperative femoral nerve block with regular paracetamol. 6, 7
• Thromboprophylaxis: Use fondaparinux or low molecular weight heparin. 6
• Early mobilization: Weight-bearing as tolerated starting postoperative day one reduces DVT risk and improves functional recovery. 6, 8

Long-term Considerations

• Arrange outpatient DEXA scan and bone health clinic referral for osteoporosis treatment to prevent subsequent fractures. 6, 7
• Utilize interdisciplinary care programs involving orthopedics, geriatrics, physical therapy, and nursing to decrease complications. 7, 8