Matthew S. Austin, S. Mehdi Jafari, and Benjamin Bender
DEFINITION
Estimates indicate that by the year 2030 the volume of primary total knee arthroplasty cases will have increased to 3,480,000, and the number of revision procedures is expected to rise accordingly, to 268,200.1
Indications for removing well-fixed total knee components include infection, malalignment, malpositioning, instability, periprosthetic fracture, stiffness, or aseptic loosening of the other part(s).
Achieving the goal of safe removal of well-fixed components during revision total knee arthroplasty (TKA) depends on meticulous surgical technique and availability of the appropriate instruments. In many ways, these are the most important portions of the revision TKA procedure, because careless technique may lead to damage of the remaining bone stock, iatrogenic fracture, and disruption of soft tissues, ultimately compromising the quality of the revision construct and the outcome for the patient.
ANATOMY
Removal of well-fixed TKA components necessitates adequate exposure.
Proper management of the extensor mechanism is essential. A medial parapatellar arthrotomy may not provide the exposure required for component removal and subsequent reconstruction. Extensile exposure techniques using a tibial tubercle osteotomy, quadriceps snip, or V-Y quadricepsplasty, are described in Chapters AR-26 and AR-27.
PATHOGENESIS
Indications for removal of well-fixed TKA components include infection, malalignment, malpositioning, instability, periprosthetic fracture, stiffness, or aseptic loosening of the other component(s).
PATIENT HISTORY AND PHYSICAL FINDINGS
The history and physical examination should be directed to determine whether the patient's pain is extrinsic or intrinsic to the TKA.
Extrinsic sources of pain (eg, lumbar radiculopathy, referred hip pain) should be considered in the differential diagnosis.
Pain that is determined to be intrinsic to the TKA should be correlated with the history, physical examination, and radiographic findings to confirm that the cause of the pain can be corrected with revision TKA.
Failure to identify a cause for the patient's pain before performing the revision TKA portends a poor prognosis.
Physical examination includes the following:
Visual inspection of the previous incision and the surrounding skin. The most appropriate, lateral-most incision is selected to avoid wound necrosis and maximize healing potential.
Passive and active range of motion (ROM) are assessed. ROM postoperatively predominantly depends on their preoperative ROM. Normal ROM after TKA ranges from full extension to 120 to 135 degrees. It is important to inform patients that revision TKA may not improve their ROM. Stiff knees may require extensile exposure techniques or capsular releases. Extensor lag may indicate a deficient extensor mechanism.
The medial and lateral collateral ligaments are tested in full extension and at 30 degrees of flexion. Coronal plane instability may make it necessary to remove well-fixed components and implant components with more constraint.
The anterior and posterior stability of the knee is assessed. Sagittal plane instability may make it necessary to remove components to improve flexion–extension gap balancing or to compensate for a deficient posterior cruciate ligament in patients with a cruciate-retaining design.
The coronal plane alignment is assessed with the patient standing. The femorotibial angle is measured; it usually is 5 to 7 degrees of valgus. It may be necessary to remove wellfixed components to correct malalignment.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Standing anteroposterior (AP), lateral, and patellofemoral radiographic views are essential.
Full-length standing AP radiographs are useful to determine the overall mechanical alignment of the lower limb.
The radiographs must show the diaphysis well above the femoral prosthesis and well below the tibial prosthesis.
The radiographs are assessed for alignment, component positioning and size, joint line position, loosening, and bone stock and osteolysis.
CT scans may be useful to assess for osteolytic lesions or to assess for femoral and tibial component rotation.
Inflammatory markers, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), are obtained to screen for the presence of infection.
Aspiration of the knee is indicated if either the ESR or CRP is elevated or if there is clinical suspicion of infection.
DIFFERENTIAL DIAGNOSIS
Lumbar radiculopathy
Hip pathology
Neuropathy
Complex regional pain syndrome
Vascular claudication
Primary bone tumors
Metastatic disease
Trauma
NONOPERATIVE MANAGEMENT
Nonoperative management of the failed TKA may consist of activity modification, physical therapy, bracing, and consultation with pain management specialists.
SURGICAL MANAGEMENT
Surgical management begins with preoperative planning.
The patient's history, physical examination, radiographs, and laboratory studies are reviewed well in advance of the surgery, to allow for adequate preparation time.
The cause for failure of the TKA is determined.
The surgical plan is delineated, with a primary plan formulated and contingency plans developed.
The appropriate instrumentation, implants, and bone graft (if necessary) are ordered.
The knee is exposed, with extensile approaches if necessary.
The components are removed carefully, with meticulous attention paid to preservation of bone stock and the soft tissues.
The knee is subsequently reconstructed.
Layered closure is performed carefully.
Preoperative Planning
The key to any successful revision TKA is preoperative planning. The reason for failure of the original TKA is determined from study of the preoperative history, physical examination, imaging studies, and laboratory results.
It is decided whether removal of all femoral, tibial, and patella components is necessary or if an individual component can be left in situ.
The previous operative reports are reviewed, with particular attention paid to the surgical approach, releases performed, and implants that were used.
The operative report or implant stickers should be reviewed carefully. One should determine whether the tibial polyethylene component is modular and what sterilization method was used for it. If some of the index TKA components are to remain in situ, the surgeon must determine whether compatible parts are available.
Radiographs are reviewed for bone stock quality and quantity.
Particular attention is paid to the fixation method of the components. Stems that were cemented may require the use of ultrasonic tools for removal of the remaining cement.
FIG 1 • Positioning for revision TKA surgery. The foot bump is positioned to prevent the foot from sliding while the knee is flexed.
Positioning
The patient is positioned supine on the operating room table.
A bump is placed so that the foot can be supported with the knee in flexion (FIG 1).
The knee is draped to allow for an extensile surgical exposure.
Approach
The preferred surgical approach is a standard medial parapatellar approach, although an extensile approach may be necessary (see Chaps. AR-27 and AR-28).
Adequate exposure of the components to ease implant removal and subsequent reconstruction is crucial.
A variety of instruments can be used to remove the wellfixed TKA implant: osteotomes, Gigli saws, punches, saws, burrs, metal-cutting discs or burrs, and ultrasonic tools.
Implant removal proceeds in the following order (if all components are being removed): tibial polyethylene, tibial tray, femoral component, patella component.
We prefer to remove the tibial tray before we remove the femoral component to protect the femoral bone from the retractors. However, if it is difficult to remove the tibial tray with the femoral component still in place, it may be necessary to remove the femoral component first. If this is the case, the femoral bone can be protected with sponges.
TECHNIQUES
Exposure
The extensor mechanism must be subluxated laterally, with careful attention to avoid detaching the insertion of the patella tendon.
A thorough synovectomy is performed, and the medial and lateral gutters are recreated.
The collateral ligaments must be identified and protected.
The interface of the femoral, tibial, and patellar components with bone must be visualized.
TIBIAL COMPONENT POLYETHYLENE REMOVAL
The tibial polyethylene is removed first to increase the space within which the surgeon can work to remove the components.
If a modular implant was used, it is removed by inserting an osteotome at the interface of the polyethylene and the tray and levering the polyethylene out. This can even be accomplished with a nonmodular design (TECH FIG 1).
Certain posterior-stabilized designs have a reinforcing metal pin in the post that may need to be removed before the insert can be levered out. A saw can be used to divide the post, and the pin can be removed with a rongeur.
Some inserts also are secured to the tray with a clip or screws. Therefore, it may be necessary to order special instruments from the implant manufacturer to facilitate removal.
TECH FIG 1 • Method of removing the tibial polyethylene from the tray. The osteotome is inserted between the polyethylene and the tray, and the insert is levered out.
TIBIAL COMPONENT REMOVAL
The prosthesis–cement interface is targeted in cemented components.
The prosthesis–bone interface is targeted in uncemented components.
The target interface is disrupted with a thin sawblade, with careful protection of the soft tissues (TECH FIG 2A).
The area under the tray that is not accessible to the saw is disrupted with osteotomes (TECH FIG 2B). The tibia can be externally rotated to provide access to the posterior aspect of the component. Care must be taken to protect the neurovascular structures posteriorly.
A clear path for egress of the tibial component must be achieved. The posterolateral aspect of the tibial component must clear the posterolateral femoral condyle. To achieve this, hyperflexion and anterior dislocation of the knee is necessary. Care must be taken to avoid avulsion of the patella tendon.
It may be necessary to remove the femoral component first if it blocks a clear trajectory for tibial component removal.
The tray can be gently disimpacted with a punch (TECH FIG 2C). If the component does not separate readily from the cement mantle–bone portion, then further work with the osteotomes is necessary. Excessive force will lead to unnecessary bone loss or fracture.
The implant can be separated from the cement or bone by stacking broad osteotomes. One should avoid trying to lever the implant out with the osteotomes, because this may lead to fracture. Once the implant is separated from the cement or bone, it can be removed by hand or with a punch.
The remaining cement is then removed with curettes, osteotomes, saws, and burrs. Reverse curettes, commonly used in hip revision surgery, can be useful in removing cement from the canal.
TECH FIG 2 • A. The interface between the component and the cement is disrupted with a thin sawblade. The soft tissues are protected. B. Osteotomes are used between the component and the cement in areas where the sawblade was unable to disrupt the interface. Hyperflexion, external rotation, and anterior dislocation of the knee facilitates access to the posterior aspect of the tibial component. C. The tibial component is gently disimpacted with a punch. Excessive force should be avoided. If the component cannot be extracted with gentle force, then further work with the osteotomes is needed.
FEMORAL COMPONENT REMOVAL
The prosthesis–cement interface is targeted in cemented components.
The prosthesis–bone interface is targeted in uncemented components.
The target interface is disrupted with a thin osteotome or saw with careful protection of the soft tissues (TECH FIG 3A).
TECH FIG 3 • A. The femoral component–cement interface is disrupted with an osteotome. The osteotome should be inserted parallel to the component. Smaller-width osteotomes can be used at the interface of the chamfer cuts and around distal pegs. Curved or angled osteotomes are helpful to work the interface of the posterior condyles. B. It should be possible to remove the femoral component easily by hand or with light taps from a punch. If the component is not extracted with gentle force, then further work with the osteotomes is needed.
In general, use of Gigli saws results in the removal of more bone than is seen with the meticulous use of osteotomes.
The interfaces should be worked from the medial and lateral sides rather than attempting to traverse the entire prosthesis with the instruments. This allows a more controlled division of the interface and minimizes iatrogenic bone loss.
Care is taken to direct the instruments parallel to the component to avoid removing additional bone unnecessarily.
Narrow osteotomes are used for the chamfer cuts and for prostheses where there are pegs at the distal aspect of the component.
The posterior condylar interface can be disrupted with a curved or angled osteotome.
It should then be possible to remove the implant easily by hand or with light taps from a punch set on the anterior flange (TECH FIG 3B). Alternatively, an extraction device that grasps the distal aspect of the femoral component can be used. The key point is gentle removal of the implant. Excessive force may result in unnecessary bone loss or fracture.
The remaining cement is then removed with curettes, osteotomes, saws, and burrs.
PATELLA COMPONENT REMOVAL
The removal of a well-fixed polyethylene component should be done only after thoughtful consideration. The remaining patella bone stock often is thin and osteopenic with one or several stress-risers from previous fixation pegs.
The prosthesis–cement interface is targeted in cemented components.
The prosthesis–bone interface is targeted in uncemented components.
The target interface is disrupted with a thin sawblade (TECH FIG 4A).
All polyethylene components can be removed with a sawblade, and the pegs subsequently burred (TECH FIG 4B). Cementless components may require the use of a metal cutting disc to sever the pegs from the plate. A pencil-tip burr can then be used to remove the pegs.
Any remaining cement is removed with curettes, saws, and burrs.
TECH FIG 4 • A. The patella button is removed with a thin sawblade. The pegs remain embedded in the cement. B. A pencil-tip burr is used to lever the polyethylene pegs out of the cement mantle. The burr is advanced into the polyethylene and stopped; the polyethylene is then easily levered out of the cement mantle. A larger burr is then used to remove the remaining cement mantle.
STEMMED IMPLANT REMOVAL
Stemmed implants usually can be removed once the fixation between the condylar portion of the femoral component and the tray portion of the tibial component has been separated from the bone.
Preoperative planning should take into consideration the use of stemmed implants, which may complicate extraction of the component.
Some designs allow for disassembly of the stem from the remainder of the implant.
Metal cutting burrs and discs may be necessary to separate the condylar portion of the femoral implant or the keel portion of the tibial implant from the stem. The stem can then be removed with trephine reamers, burrs, or ultrasonic tools. Some companies may make special extraction devices available to assist in removal of the stem.
Rarely, it may be necessary to perform an osteotomy to extract particularly difficult stems.
COMPLICATIONS
Bone loss
Fracture
Ligament disruption
Tendon disruption
REFERENCE
1. Kurtz S, Ong KL, Schmier J, et al. Future clinical and economic impact of revision total hip and knee arthroplasty. J Bone Joint Surg Am 2007;89A:144–151.