Orthopaedic Knowledge Update®: Musculoskeletal Infection 2 Print + Ebook (AAOS - American Academy of Orthopaedic Surgeons)

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Section 4: Prosthetic Joint Infections

or a single-stage procedure is more likely to fail such as PJI with active sepsis or virulent/resistant pathogens. Stage One and Antibiotic Spacers The first stage involves the removal of implants, extensive débridement, and usually, the insertion of an antibiotic spacer. Implant removal can be extremely complex and time consuming if the implants are well-fixed. The goal with any implant removal is to perform an extensive synovectomy and preserve as much bone as possible. Techniques to remove implants are beyond the scope of this chapter but are integral to master when performing revisions for infection. Inserting a spacer during the interval between the first and second stage of a two-stage revision serves several purposes. It maintains the joint space and often can be a functional joint, providing patients com fort and making reimplantation easier. In addition, spacers are used to deliver antibiotics locally, which may aid in infection control. Spacers can be defined as static (nonarticulating) or dynamic (articulating). Dynamic spacers can be made entirely of cement or composed of normal arthroplasty components with a metal-on-polyethylene articulation, commonly referred to as a low-friction spacer. Knee A 2019 study reported on the use of static spacers as a temporary arthrodesis with antibiotic-loaded cement between the femur and tibia, usually with an intramedul lary device extending into the diaphysis of the femur and tibia. 25 These serve to maintain the joint space and pro vide increased stability of the knee. These are generally indicated for severe bone loss, collateral ligament insuf ficiency ( Figure 1 ), periarticular fracture, or extensor mechanism disruption. 26,27 Articulating cement spacers can be prefabricated or made intraoperatively. The benefit of the prefabricated spacers ( Figure 2 ) is time saved in the operating room. However, the antibiotic agent present in the prosthesis cannot be tailored to the sensitivities of the pathogen. Limitations of these spacers include patient discomfort, as they often report a grinding sensa tion with joint movement. In addition, these spacers can dislodge or fracture ( Figure 3 ). Low-friction spacers are gaining popularity because the joint feels more normal to patients ( Figure 4 ). Concerns regarding the use of metal and polyethylene in an infected joint are expected, but a 2020 study reported no increase in failure or subsequent reinfection with these spacers. 28 Some surgeons place antibiotic dowels in the medullary canal to help stabi lize the implant and to deliver additional antibiotics. A 2019 study evaluating their use reported no increase in infection eradication. 29

Hip Nonarticulating (Girdlestone) spacers in the hip are usually composed of packed antibiotic-laden cement in the acetab ulum and in the open femoral canal ( Figure 5 ). Antibiotic beads can also be used. The primary indication for nonar ticulating hip spacers is inadequate bone stock to support a dynamic spacer. Similar to the knee, dynamic spacers in the hip vary in design and composition. Hip spacers can be prefabricated with antibiotic cement or can be sized and molded intraoperatively. Real-component, low-friction spacers have gained popularity in the hip as well ( Figure 6 ). The benefit of articulating spacers is that the patient obtains a functioning hip during the interval between stages. Complications however have been described, including fracture, bone erosion, and dislocation. A and B , Lateral and AP radiographs showing pre vious hinged total knee arthroplasty with collateral ligament insufficiency. C and D , AP and Lateral radiographs show the same knee with subsequent prosthetic joint infection treated with static spacer rather than an articulating spacer because of collateral ligament insufficiency. FIGURE 1

Section 4: Prosthetic Joint Infections

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Orthopaedic Knowledge Update ® : Musculoskeletal Infection 2

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