Polyethylene and Tibial Baseplate Wear in a TKA Patient with a PJI
A 61-year-old male presents with an acute periprosthetic infection of his left knee. Radiographs demonstrate severe polyethylene wear and likely tibial base plate damage. What is the best option to manage this patient?
Arjun Saxena, MD, and John R. Schnell, MD
A 61-year-old male patient with rheumatoid arthritis presented to our office after experiencing pain, discomfort, and swelling in the left knee and a temperature of 104F. He was referred to our office by his rheumatologist.
The patient was taking methotrexate, etanercept (Enbrel), and prednisone to treat his rheumatoid arthritis. He had no previous history of infection or recent illness, although he had had a dental cleaning about 1 week prior to presentation. He had not taken antibiotic prophylaxis before the cleaning.  A thick, brown fluid likely consistent with infection was aspirated from his left knee in the office, and he was sent directly to the hospital for blood work and imaging.
The patient had undergone total knee arthroplasty about 25 years prior to presentation. Eleven years after the index surgery, he was treated for a left knee periprosthetic femur fracture. He underwent open reduction and internal fixation with lateral plating of the femur. Overall, he had done well since then, but he did report increased pain and limited range of motion over the past few years.
- Height: 5 feet, 5 inches; weight: 180 pounds; body mass index: 30 kg/m2
- Severely antalgic gait
- Healed surgical incisions about the left knee and distal femur
- Limited range of motion of the left knee, likely secondary to pain
- White blood cell count: 13.1 K/uL (normal 4-11K/uL)
- Erythrocyte sedimentation rate (ESR): 89 mm/hour (normal < 30 mm/hour)
- C-reactive protein (CRP): > 30.0 mg/dL (normal < 1.0 mg/dL)
- Knee aspiration: 5925 white blood cells, with 80% neutrophils
Figure 1. Anteroposterior (AP) and lateral radiographs taken on presentation show polyethylene wear and damage to the tibial baseplate.
- Left knee periprosthetic joint infection
- Left knee polyethylene wear, possible tibial baseplate failure
The diagnosis of left knee periprosthetic joint infection was clear based on criteria from the American Academy of Orthopaedic Surgeons and the Musculoskeletal Infection Society.  Standard treatment includes open irrigation and debridement, synovectomy, and polyethylene exchange. This procedure has demonstrated variable success in the orthopaedic literature. 
Given the patient’s recent onset of symptoms, this treatment would seem to be a reasonable approach. However, radiographs showed a concerning amount of polyethylene wear and damage to the tibial baseplate (Figure 1, above), leading us to believe that a polyethylene exchange would not be successful.  A resection arthroplasty with removal of the hardware about the lateral femur might be indicated.
After carefully discussing the risks and benefits of various treatment options, we took the patient to the operating room with a plan for standard treatment of irrigation and debridement, synovectomy, and polyethylene exchange. But we were also prepared to perform a resection arthroplasty with hardware removal if necessary, depending on the operative findings.
After performing the arthrotomy, we removed frank purulent material from the knee. The polyethylene insert was completely worn through, as was the tibial baseplate on the medial side (Figure 2). In addition, there was significant metallosis throughout the joint. The patient would require resection arthroplasty with removal of the lateral femoral plate.
Figure 2. Worn tibial baseplate.
The femoral component was removed, revealing significant bone loss of the lateral femoral condyle with osteolysis (Figure 3). No distal or posterior condyle was observed, and only a shell was present along the lateral epicondylar region. This is consistent with a Type 3 AORI defect.  The tibia was removed without significant bone loss (Type I AORI defect).
Figure 3. Intraoperative photos showing significant bone loss and metallosis.
Next, an incision was made on the lateral aspect of the femur and the screws and plate were removed. Purulent material was also found in the area of the lateral femoral plate. The knee was irrigated and debrided, and a thorough synovectomy was performed. An articulating antibiotic cement spacer was fashioned using molds.  The wound was closed and drains were placed (Figure 4).
Figure 4. Postoperative AP and lateral radiographs.
The patient remained in the hospital for 12 days following surgery due to a persistently elevated temperature and serous drainage from the wound. We recommended repeat irrigation and debridement and revision of the antibiotic spacer.
No purulent material was encountered during the second procedure, although there was brownish serous fluid. The knee was again irrigated and debrided and the antibiotic spacer was removed. We observed significant distal femoral bone loss on the lateral side and significant loss of the anterior cortex of the femur.
Infectious disease was consulted. When cultures grew Escherichia coli, the patient was placed on levofloxacin (Levaquin) via a PICC line. Antibiotic treatment continued for 6 weeks.
Two months after surgery, the patient had an elevated CRP (10.7 mg/dL) and a normal ESR (17 mm/hour). Repeat aspiration of the left knee yielded no fluid. The patient’s incisions had healed without incident, and his left knee had a range of motion from 0 to 80. The patient had no obvious signs of infection, a normal ESR, and a significantly decreased CRP, leading us to recommend reimplantation of a knee prosthesis. 
Careful consideration was given to the type of implant that would be utilized. A standard constrained prosthesis would typically be appropriate in a patient with bone loss. Metaphyseal fixation with sleeves and diaphyseal fixation with stems have demonstrated excellent results. 
This patient had significant metaphyseal bone loss about the distal femur and we were concerned that we would not be able to implant a standard constrained prosthesis due to lack of fixation. When reconstruction is not possible, a distal femoral replacement is required. We had misgivings about using this type of implant due to the patient’s age and activity level – loosening/failure rates have been reported to be at least 10% within 5 years of surgery.  In addition, given the patient’s previous history of femoral shaft fracture with an abnormal femoral canal, we had some concern that a long stem would be difficult to implant in the femoral shaft.
The patient returned to the operating room. The spacer was removed, and the wound was debrided and soaked in a povidone-iodine and saline mixture for 3 minutes.  The tibia was evaluated first and again was found to have minimal defects. Reamers and broaches were used for a sleeve and the tibia was reconstructed without difficulty.
Attention was then turned to the distal femur. We determined that fixation could not be achieved with a standard constrained prosthesis given the significant anterior and lateral bone loss. Thus, the decision was made to perform a distal femoral replacement. Once the distal femur was cut, broaches were sequentially used until appropriate fixation was achieved. Reaming was attempted for a proximal stem, but we were concerned about perforation due to the irregular shape of the femoral canal from the previous fracture. We decided to use metaphyseal fixation alone with the distal femoral replacement component.
Figure 5. Postoperative AP and lateral X-rays
Four months after surgery, the patient has a range of motion from 0 to 87 with excellent stability in the varus-valgus plane. He walks without an ambulatory aid and has minimal pain. His biggest complaint is persistent generalized swelling and stiffness, which is to be expected given his recent surgery.
- Careful implant removal in revision surgery preserves bone and aids in reconstruction.
- AORI classification of bony defects aids in determining reconstruction options.
- Metaphyseal fixation is helpful and indicated in patients with large bony defects.
- Patients with femoral and tibial canal defects may benefit from the use of fluoroscopy in revision surgery.
- Povidone-iodine lavage has been shown to be effective for infection prevention in primary joint replacement and may be an option in revision surgery; further study is recommended. 
- Further study should be performed to determine the correlation between late hematogenous periprosthetic infection and surgical/dental procedures. 
- Chronic antibiotic suppression may help to prevent recurrent infection in patients treated for periprosthetic infection. 
The authors have no disclosures relevant to this article.
Adult Reconstruction Section Editor, Rothman Institute Grand Rounds
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