Segmental induction heating of orthopaedic metal implants

Area of Science:

• Orthopaedic surgery
• Biomaterials engineering
• Thermal therapy

Background:

• Prosthetic joint infection (PJI) is a severe complication of total joint arthroplasty.
• Non-contact induction heating is an emerging treatment for PJI.
• Concerns exist regarding potential thermal damage to surrounding tissues.

Purpose of the Study:

• To evaluate the thermal dose distribution from segmental induction heating of common orthopaedic implants.
• To determine thermal dose at varying distances from the heating center (HC).
• To assess the safety of induction heating for limiting collateral thermal injury.

Main Methods:

• Segmental induction heating was applied to hip stems, intramedullary nails, and locking compression plates (LCPs).
• Thermal dose was measured using a thermal camera and expressed as cumulative equivalent minutes at 43°C (CEM43).
• A threshold of 16 CEM43 was used to define thermal damage to bone.

Main Results:

• High thermal doses were achieved at the HC (7161–66,640 CEM43).
• Thermal doses remained below the 16 CEM43 damage threshold at distances from the HC for hip stems and nails.
• For LCPs without screws, thermal doses exceeded 16 CEM43 up to 5 mm from the HC.

Conclusions:

• Segmental induction heating effectively concentrates thermal dose on target implants.
• Non-heated portions of the implant act as heat sinks, minimizing collateral thermal injury.
• Implant type and geometry significantly influence heat dissipation and potential thermal damage.