Technical factors for success with metal ring acetabular reconstruction

Area of Science:

• Orthopedic Surgery
• Biomaterials Engineering

Background:

• Acetabular revision surgery aims to restore hip joint stability and function.
• Metal ring supports are utilized to reconstruct acetabular defects.
• High failure rates necessitate understanding of failure mechanisms and improved surgical techniques.

Purpose of the Study:

• To evaluate the mechanical failure rates and modes of acetabular metal ring supports (Mueller, Ganz, Burch-Schneider) in hip revision surgery.
• To identify risk factors for mechanical failure and dislocation.
• To provide recommendations for optimizing acetabular reconstruction.

Main Methods:

• Retrospective review of 64 hip revisions performed by a single surgeon.
• Use of Mueller ring, Ganz ring, or Burch-Schneider cage with cemented polyethylene cups.
• Analysis of radiographic and clinical outcomes, including aseptic loosening and dislocation.

Main Results:

• Overall mechanical failure rate was 17% (11/64), primarily due to aseptic loosening and migration.
• Acetabular support migration occurred with >60% superior bone defects filled with cement or particulate graft.
• Dislocation occurred in 23% (15/64) of hips, requiring reoperation in 8% (5/64).

Conclusions:

• Acetabular metal ring supports have a significant mechanical failure rate, influenced by the extent of bone defect and graft material used.
• Optimal support fixation requires >60% contact with host bone, utilizing bulk allograft for larger defects.
• Constrained liners are recommended for patients with trochanteric nonunion and significant abductor weakness to reduce dislocation risk.