Knee Arthrodesis for Recurrent Periprosthetic Knee Infection.

UNLABELLED

Knee arthrodesis for recurrent periprosthetic knee infection is a limb salvage procedure that simultaneously provides a stable limb for weight-bearing and effective eradication of the chronic infection. Knee arthrodesis is a final resort for limb salvage that is appropriate for patients with multiple recurrent revisions for infection, a history of failed 2-stage exchanges, medical comorbidities, and an inability to tolerate multiple additional procedures. Another important consideration is whether the patient has a poor soft-tissue envelope that leaves knee arthrodesis as the only viable option. The procedure is a definitive surgery to eliminate return trips to the operating room.

DESCRIPTION

This technique involves knee arthrodesis using a long intramedullary rod inserted proximally through the piriformis fossa that spans the entire medullary canal of the femur and the tibia. Before insertion, the surgeon may elect to create a long antibiotic cement-coated intramedullary rod. The rod is locked proximally and distally. An alternative method for large bone defects (>6 cm) at the level of the knee is to create intercalary antibiotic-impregnated cement spacers.

ALTERNATIVES

Alternative surgical treatments for this problem include above-the-knee amputation or resection arthroplasty, neither of which provides a functional limb for weight-bearing. The most common alternative methods for knee arthrodesis include external fixation using circular or biplanar frames, as well as short intramedullary modular rods.

RATIONALE

Knee arthrodesis using a long intramedullary rod is a very effective and efficient method of fusion. With recurrent periprosthetic knee infections, metaphyseal bone loss is common and short knee-fusion rods may not provide adequate stability. Long rods for knee arthrodesis use the diaphysis for stability and have the additional advantage of being easily accessible for removal in the event of a recurrent infection with a well-healed fusion. Long intramedullary rods also provide the additional advantages of immediate weight-bearing. Immediate weight-bearing on the affected limb is critical because often these patients have been unable to bear weight preoperatively secondary to pain and infection. External fixation techniques are effective but come with pin-site problems. Pin-site problems are amplified in patients with obesity who have large soft-tissue envelopes, and the long intramedullary rod avoids pin problems in such patients. Antibiotic cement coating of the long intramedullary rod also provides local antibiotic delivery.