Evolution and future of surface replacement of the hip

Area of Science:

• Orthopedic Surgery
• Biomaterials Science
• Medical Device Engineering

Background:

• Surface replacement hip arthroplasty, a bone-conserving alternative to total hip arthroplasty, was initially hindered by polyethylene wear and aseptic loosening.
• Hemisurface replacement of the femoral head is the preferred treatment for osteonecrosis with preserved acetabular cartilage, showing 85% survival at 5 years in early series.
• Early polyethylene-bearing surface replacements faced challenges with component loosening due to high volumetric wear and tissue reactions.

Discussion:

• Modern metal-on-metal bearings in surface replacement have drastically reduced volumetric wear (20-100 times less than polyethylene), enabling larger ball sizes without adverse effects.
• Improved instrumentation and off-the-shelf components enhance the precision and applicability of surface replacement procedures.
• Hybrid or cementless fixation methods demonstrate superior outcomes compared to earlier cemented devices, with complication-free results and functional recovery.

Key Insights:

• Metal-on-metal bearings have revitalized surface replacement arthroplasty, offering significant wear reduction and improved longevity.
• The evolution of instrumentation and fixation techniques has enhanced the safety and efficacy of hip surface replacement.
• Patients undergoing modern surface replacement report pain-free recovery and a return to high functional levels, including sports participation.

Outlook:

• Further advancements in biomaterials and implant design are expected to enhance the long-term durability of surface replacement arthroplasty.
• Continued research into cementless fixation and patient selection will optimize outcomes for a broader range of hip conditions.
• The potential for surface replacement to provide a durable, bone-preserving solution for younger, active patients remains a key area for future development.