Head size and dislocation rate in primary total hip arthroplasty.

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering
• Arthroplasty Research

Background:

• Dislocation after total hip arthroplasty (THA) is multifactorial, influenced by surgical approach, component positioning, and implant size.
• Literature suggests larger femoral head sizes may correlate with lower THA dislocation rates, but robust data is limited.

Purpose of the Study:

• To investigate if utilizing a larger femoral head size in primary THA leads to a decreased incidence of dislocation.

Main Methods:

• A retrospective study of 317 primary THAs performed between 2006-2009 using a posterolateral approach.
• Patients were divided into two groups: Group A (163 hips) received 36 mm heads, and Group B (154 hips) received 28 mm heads.
• Follow-up averaged 2 years, with specific assessment for dislocation events.

Main Results:

• The overall dislocation rate was 3.47% (11 out of 317 hips).
• Dislocation rates were significantly lower in the larger head group: 0.6% for 36 mm heads versus 6.49% for 28 mm heads (P=0.0107).
• This significant difference persisted regardless of cemented or uncemented stem usage.

Conclusions:

• Increasing femoral head size in primary THA is associated with a significant reduction in dislocation rates.
• Longer follow-up is warranted to assess potential long-term risks, such as polyethylene failure or fracture, which could impact future dislocation rates.