Case 1
A 72-year-old woman underwent a total knee arthroplasty (TKA) for primary osteoarthritis that was revised to a hinged TKA 12 years later because of loosening. Twelve months after the revision TKA, she was referred to our center. A postoperative infection occurred 3 weeks after the index implantation. The knee was reoperated to provide surgical débridement. A fistula persisted postoperatively, and the patient continued to have severe pain. Early loosening was observed on sequential radiographs ( Fig. 35.1 ). Persistent infection was diagnosed after culture of a knee aspirate grew Staphylococcus aureus that was sensitive to methicillin.
We performed a one-stage exchange with reconstruction using a hinged prosthesis with cemented stem extensions and provided immediate coverage with a gastrocnemius flap. Intraoperative samples confirmed the diagnosis. Postoperative antibiotic treatment was given intravenously for 2 weeks and orally for 3 months. The postoperative course was uneventful. After 2 years, the patient had only minor pain after strenuous activities. There were no signs of persistent infection, and no pathologic changes were observed on the final radiographs ( Fig. 35.2 ).
Case 2
A 70-year-old man underwent a TKA 6 months before referral to our center. He was never satisfied with the results because of persistent pain. Prosthetic loosening with tibia subsidence was observed after 6 months ( Fig. 35.3 ). The result of a perioperative aspiration was negative, but the clinical history supported a diagnosis of chronic infection.
We performed a one-stage exchange with reconstruction using a stabilized prosthesis with cemented stem extensions. Intraoperative samples confirmed the diagnosis of infection, and culture grew Propionibacterium acnes . Postoperative antibiotic treatment was given intravenously for 2 weeks and orally for 3 months. The postoperative course was uneventful. At follow-up after 2 years, the patient had no complaints of knee pain. There were no signs of persistent infection, and no pathologic changes were observed on the final radiographs ( Fig. 35.4 ).
Chapter Preview
Two-stage exchange is considered the gold standard for treatment of chronic infection after total knee arthroplasty (TKA). However, a one-stage exchange may be an alternative to provide infection control and better knee function. In our experience, routine one-stage revision has not been associated with a higher rate of infection recurrence, but knee function was not improved compared with the results of two-stage revisions. One-stage exchange may be a reasonable alternative for some patients with chronically infected TKAs, improving their quality of life and reducing hospital costs.
Introduction
Infection after TKA is a devastating complication that threatens life and function. With the use of modern prophylactic measures, a low incidence of postoperative infection (1% to 2%) is to be expected. However, with the increasing number of TKAs performed, the number of infections will increase in proportion.
Treatment of infected TKAs usually requires surgery. Débridement should be performed only for early-stage infections. For chronic infection, prosthesis removal is considered mandatory. Implantation of a new prosthesis usually is performed in a subsequent stage after a variable waiting period (i.e., two-stage protocol) for healing of the infection. The period without any implant in place theoretically allows better control of the infection with systemic antibiotic therapy, but the patient must endure functional impairment during this period, and the final outcome may be poorer.
One-stage reimplantation was first proposed by Wroblewski. The theoretical advantage is that this approach suppresses the waiting period before reimplantation and improves the final functional outcome. It also avoids the need for a second demanding procedure with inherent risks of complications, including the occurrence of a new infection. However, the one-stage procedure has a higher risk of persistent or recurrent infection due to deficient débridement or insufficient antibiotic treatment.
Two-stage protocols are considered the gold standard for the treatment of infected TKAs. One-stage procedures usually are considered contraindicated or reserved for selected cases (e.g., those with no fistula, no severe bone damage, and a known pathogen with high sensitivity to antibiotics). However, only limited, nonprospective studies have addressed these issues, and systematic literature analyses have been inconclusive.
A routine one-stage protocol that includes prolonged oral antibiotic treatment may be applied to all cases of chronically infected TKA except for fungal infections and repeat failures of previous infection treatments. This chapter presents this protocol, with its important points and pitfalls, and compares its results with those reported in the literature.
Indications and Contraindications
At our institution, a routine one-stage protocol is used for almost all cases of chronically infected TKA, provided that certain conditions are met. There are few contraindications:
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Cases of early postoperative infection are considered for débridement with implant retention when the surgical treatment is performed up to 6 weeks after the index implantation.
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Cases of hematogenous infection are considered for débridement with implant retention when the surgical treatment is performed up to 7 days after the onset of the symptoms.
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Fungal infection is routinely treated with a two-stage procedure.
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Repeat failure of TKA exchange (one or two stage) is routinely considered for a two-stage protocol.
All other cases are typically treated with a one-stage prosthesis exchange. In selecting patients, we do not take into account the classic contraindications for such a protocol, such as fistula, resistant pathogen, poor medical status, or extensive bone destruction. The only contraindication might be a chronic infection with a pathogen (e.g., fungus) with virtually no possibility of prolonged antibiotic treatment. However, these cases are rare.
Equipment
No special orthopedic equipment is required beyond the usual instruments, devices, and implants used for a revision TKA. However, surgeons must be prepared to solve any technical complexities arising during the revision procedure, including the need for a bone allograft, prosthesis augmentation, stem extension of the appropriate length and diameter, or a more constrained prosthesis, including a hinged prosthesis. Extraction of a cemented resurfacing prosthesis may be facilitated by the use of a Gigli saw. Extraction of a cemented stemmed prosthesis may be helped by the use of an ultrasound device (Orthosonics System for Cemented Arthroplasty Revision [OSCAR], Orthosonics, Chatham, NJ), which may preclude a diaphyseal osteotomy. In special cases, it may be necessary to reconstruct the extensor mechanism with an autograft or allograft. Intraoperative fluoroscopic imaging may be helpful.
Soft tissue that is compromised by multiple scars or a fistula must be excised. A one-stage exchange implies a primary skin closure or at least effective flap coverage. The orthopedic team should be able to perform the commonly used flaps (mostly gastrocnemius or soleus muscular flaps) in the same stage after prosthetic implantation. If they are not, a reconstructive plastic surgery team must be available to perform the operation immediately. This point may preclude the use of a one-stage protocol, especially if a fistula complicates the septic revision.
The prolonged postoperative antibiotic regimen includes many types of oral drugs tailored to the responsible microorganism. If the patient cannot undergo prolonged oral antibiotic treatment or a fungal species is identified, a one-stage procedure is contraindicated.
Surgical Technique
Preoperative Radiologic Planning
The preoperative radiologic planning includes standard anteroposterior and lateral plain radiographs to assess the quality of fixation of the implant, the presence of loosening, and any bone defects. Stress radiographs in varus and valgus are used to assess ligamentous balance. Anteroposterior and lateral long leg radiographs are obtained to assess leg alignment and to guide the direction of the anatomic axes of the femur and tibia in cases of implantation of a stem extension. Computed tomography (CT) may be useful to accurately assess bone defects, especially on the femoral side.
Anatomy and Approach
The scar of the index implantation must be considered in planning the revision procedure. Another skin incision may be used if the scar tissue seems to be of poor quality or the surgeon is accustomed to another approach. However, it is usually easier and safer to use the previous scar, to avoid creating a poorly vascularized cutaneous flap in the area lying between the two incisions. A fistula may be excised by a separate incision. In the case of multiple skin incisions, the most lateral one is usually the most suitable due to its blood supply.
Procedure
We prefer a transvastus anteromedial approach. The articular incision is extended proximally according to the requirements of the specific case. It may be necessary to perform a tibial tubercle osteotomy to gain better access to the joint. We routinely use a navigation system in such cases, with anatomic and kinematic registrations on the index prosthesis, but a purely conventional procedure is possible.
The first step is removal of all implants, including a patellar prosthesis, and of all metallic devices implanted during the index TKA. Meticulous technique should be used to minimize iatrogenic bone damage.
For cemented and cementless implants, small chisels are used to detach the tibial tray from the proximal tibia. A cemented stem can then be removed by hammering up the tibial tray proximally. Removal of a well-fixed cementless implant may require an extensive proximal tibia osteotomy.
Small chisels and a Gigli saw are used to detach the cemented or cementless femoral implant from the distal femur. A cemented stem can then be removed by hammering out the femoral component in a distal direction. Removal of a well-fixed cementless implant may require an extensive distal femur osteotomy.
Complete, but not necessarily extensive, débridement of all soft tissue and bone surfaces must be carefully performed. Multiple samples must be taken for microbiologic analysis and bacterial identification. Cement removal must be complete. An ultrasound device may help this removal, especially for the diaphyseal cement plugs, without the need for an extensive diaphyseal osteotomy. The medullary canal of the femur and tibia must be reamed if an intramedullary rod was used at the time of the index implantation. Pulsatile lavage with saline is used to clean the joint space and the medullary canals, after which gloves and surgical drapes are changed before the reconstruction stage begins.
Prosthetic reconstruction was performed with a standard implant in nine patients, a posterior-stabilized implant with stem extension in twenty, and a hinged prosthesis in eighteen. Antibiotic-loaded cement was used in all cases for fixation of the implants. In one case, the reimplantation was delayed because of an extensive bone defect requiring a custom-made reconstruction prosthesis; the infection eventually healed, and the knee outcome was good. Allografts were used for bone reconstruction in eleven patients, and metallic augments were used in eight patients. Suction drains were placed in thirty-nine patients, and immediate flap coverage was required in five.
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