Polyethylene synovitis following canine total hip arthroplasty. Histomorphometric analysis

Area of Science:

• Orthopedic surgery
• Biomaterials science
• Veterinary medicine

Background:

• Polyethylene (PE) wear debris is a primary concern in total hip arthroplasties (THA).
• Understanding the biological response to wear debris is crucial for long-term implant survival.
• Canine models offer valuable insights into human THA complications.

Purpose of the Study:

• To investigate the synovial membrane's response to polyethylene wear debris in canine THA.
• To evaluate the progression of inflammation and tissue changes over 24 months post-surgery.
• To determine the joint capsule's tolerance to wear debris in the absence of implant loosening.

Main Methods:

• Fifty-four canine THAs were performed, with no signs of loosening observed.
• Synovial membrane biopsies were collected at 4, 6, 8, 12, and 24 months post-operation.
• Biopsies were analyzed for inflammation, PE debris, histiocyte density, and membrane thickness.

Main Results:

• Polyethylene (PE) wear debris levels generally increased with time up to 24 months.
• Despite increasing debris, inflammatory changes in the synovial membrane did not progress.
• A significant decrease in the total thickness of synovial membrane layers was observed (P = .008).

Conclusions:

• The canine joint capsule appears to tolerate polyethylene wear debris well up to two years post-THA.
• Absence of implant loosening correlates with a non-progressive inflammatory response to wear debris.
• This study suggests a potential threshold for wear debris accumulation before adverse biological reactions occur in THA.