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    Stem Exchange in Revision TKA for Periprosthetic Fracture

    After a fall at home, a 93-year-old female patient sustains a left periprosthetic tibial fracture around a well-functioning implant from a prior total knee arthroplasty. What is the best treatment option to avoid compromising bone quality and the extensor mechanism in this patient?

    Authors

    Joseph A. Karam, MD; David G. Nazarian, MD; and P. Maxwell Courtney, MD

    Introduction

    Periprosthetic fractures around a total knee arthroplasty (TKA) present a treatment dilemma for the orthopaedic surgeon. With an aging population and an increase in the number of TKAs being performed worldwide, the incidence of associated periprosthetic femur and tibia fractures continues to rise as well. [1,2] Classically, however, treatment algorithms have been developed based on the stability of existing knee implants. [3,4]

    Because most periprosthetic fractures around the TKA implant occur in older patients, pre-existing bone stock is typically poor. Non-union rates are also high, as implants can interfere with adequate reduction and internal fixation. [5,6] Megaprostheses are an option to facilitate early weight-bearing, but are fraught with complications including infection. [7-9]

    In this article, we present a unique case of a periprosthetic proximal tibial fracture just distal to a well-fixed component and not enough bone stock to support a lateral locking plate.

    Case Presentation

    A 93-year-old female patient presented to the emergency department with left knee pain and the inability to bear weight following a fall down the stairs. She had undergone left primary TKA 18 years prior and had been functioning quite well despite her advanced age. She needed a cane only occasionally for ambulation and had no pre-existing knee pain.

    Her past medical history was significant for hypertension and hyperthyroidism.

    Physical Exam

    • Height: 5 feet, 4 inches; weight: 165 pounds.
    • Well-healed anterior midline incision
    • Obvious deformity of the left knee with ecchymosis
    • Knee range of motion unable to be evaluated
    • Normal distal left lower extremity motor and sensory exam
    • Palpable pedal pulses

    Laboratory Tests

    • Erythrocyte sedimentation rate: 18 mm/hour
    • C-reactive protein: 0.6 mg/L

    Imaging

    Figure 1. Radiographs on presentation to the emergency department showed a periprosthetic tibia fracture distal to a well-fixed, well-aligned tibial component.

    Diagnosis

    • Acute periprosthetic proximal tibial fracture just distal to a well-fixed tibial TKA component

    Treatment

    There are several considerations for the management of this patient:

    • Is there enough proximal bone stock to accommodate a lateral or dual locking plates for fixation?
    • If revision arthroplasty is attempted, what is the best technique to remove the component to minimize damage to the tibial tubercle and extensor mechanism?
    • How should we manage proximal tibial bone loss following component removal? With a proximal tibial megaprosthesis? Or a revision tibial component with metaphyseal cones?
    • Are there any other options to minimize morbidity and facilitate early weight-bearing in this 93-year-old patient?

    We discussed the risks and benefits of surgical treatment with the patient, and she agreed to a revision arthroplasty. The knee implant (NexGen, Zimmer Biomet; Warsaw, Indiana) that had been used in the patient’s primary TKA offers the surgeon the unique ability to place a modular tibial stem onto the tibial baseplate. With that in mind, we planned to retain the well-fixed, well-aligned components and place a press-fit, fluted modular stem on the tibia through the fracture. This technique, as described by the senior surgeon (DGN), would:

    • Allow for immediate weight-bearing
    • Prevent disruption of the tibial tubercle during removal of the tibial component
    • Serve as an intramedullary guide for anatomic reduction to restore the mechanical axis of the knee

    Surgical Procedure

    • Dissection was taken down to the extensor mechanism through her old anterior incision and a medial parapatellar arthrotomy was performed.
    • The femoral and tibial components were found to be well-fixed and well-aligned. The polyethylene liner was removed.
    • The tibial tubercle was found to be fractured off the proximal tibia.
    • The distal tibial segment was subluxed anteriorly and cement was removed from the canal (Figure 2).
    • Reaming was begun until a good fit was achieved in the canal (12 mm in this patient).
    • The plastic button was removed from the bottom of the existing tibial component and a press-fit stem was inserted into the canal (Figure 3).
    • The proximal fragment with the component was reduced onto the distal segment.
    • With a threaded wrench placed through the hollow tibial component, the tibial stem was engaged and then back-slapped into the Morse taper (Figure 4).
    • A new polyethylene liner was inserted with a final screw into the tibial component, and 3.5-mm screws were used to secure the tubercle and additional fracture fragments back to the prosthesis.
    • Immediate postoperative radiographs are shown in Figure 5.

    Figure 2.

    Figure 3.

    Figure 4.

    Figures 2-4. Intraoperative photographs show the novel technique of tibial stem exchange for management of a periprosthetic tibial fracture.

    Figure 5. Immediate postoperative radiographs demonstrate the use of a press-fit stem to dictate reduction of the proximal tibial periprosthetic fracture without removing well-fixed components.

    Postoperative Follow-up

    • The patient was made weight-bearing as tolerated with a hinged knee brace locked in extension for 6 weeks to allow for healing of the periprosthetic fracture and to protect the extensor mechanism.
    • Range of motion was gradually advanced for 3 months, at which point the brace was removed.
    • By 6 months, the patient was walking at her baseline with only minimal use of a case. She had an intact extensor mechanism and range of motion from 0° to 115°. Radiographs at 6 months after surgery are shown in Figure 6.

    Figure 6. Radiographs 6 months following revision arthroplasty with stem exchange show that the periprosthetic fracture has healed.

    Surgical Pearls

    • Very proximal periprosthetic tibia and very distal periprosthetic femur fractures make plate fixation difficult. Surgeons should consider the addition of a modular stem if existing components allow.
    • Distruption of the extensor mechanism and tibial tubercle adds to the challenges of treating these fractures.
    • Megaprosthesis reconstruction with a proximal tibial replacement or revision arthroplasty with cones should be available to address bone loss should the component need to be revised in these fracture patterns.

    Author Information

    Joseph A. Karam, MD, is an adult reconstruction fellow at The Rothman Institute and Thomas Jefferson University, Philadelphia, Pennsylvania. David G. Nazarian, MD, is an attending orthopaedic surgeon at Thomas Jefferson University Hospital and The Rothman Institute, Philadelphia, Pennsylvania. P. Maxwell Courtney, MD, is an assistant professor of orthopaedic surgery at Thomas Jefferson University Hospital and attending surgeon at The Rothman Institute, Philadelphia, Pennsylvania.

    Adult Reconstruction Section Editor, Rothman Institute Grand Rounds

    P. Maxwell Courtney, MD

    Disclosures: The authors have no disclosures relevant to this article.

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