P ITFALLS

• Removal techniques should:

   

  • minimize host bone destruction.

     

  • allow complete component and cement removal.

     

  • facilitate subsequent reconstructive options.

     

  • efficiently utilize operating room time.

Removing Well-Fixed Implants

Indications

• Presence of chronic infection

• Malposition of components leading to pain or failure

• Ligamentous instability requiring increased prosthetic constraint

• Severe osteolysis

• Failure of modular implant without suitable/ compatible polyethylene insert

• Significant damage to metal articular surfaces

  Examination/Imaging

• Preoperative radiographs should allow the surgeon to identify the type and manufacturer of the implant(s) to be removed (Fig. 1).

• Fixation interfaces should be closely inspected to reveal areas that may be particularly difficult to reach with extraction tools.

• Stemmed implants warrant particular attention due to the potential difficulty of reaching the binding interface and possible geometric block to axial extraction (Fig. 2).

  Surgical Anatomy

• Surgeons should remain cognizant of the location of three structures throughout exposure for component removal (Fig. 3).

  • The extensor mechanism, which inserts on the tibial tubercle, remains at risk during component removal. Injury due to avulsion from the tubercle or direct trauma should be avoided at all cost.

  • The superficial medial collateral ligament originates from the medial epicondyle and inserts longitudinally on the upper 5–7 cm at the proximal medial tibia.

  • The lateral collateral ligament takes its origin from the lateral epicondyle and terminates on the head of the fibula in a conjoined insertion with the distal tendon of the biceps femoris.

     

     

     

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    FIGURE 1 FIGURE 2

     

     

     

    Lateral collateral

    ligament

    Superficial medial collateral ligament

     

     

    Extensor mechanism

     

     

    FIGURE 3

     

     

     

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    Removing Well-Fixed Implants

     

    FIGURE 4

     

    Positioning

• The patient should be positioned supine with a tourniquet applied to the upper thigh.

• Knee range of motion should be unrestricted to facilitate access to all areas of the knee.

• Leg-holding devices may allow steady positioning and free the hands of an assistant (Fig. 4).

   

  P EARLS

  • No role exists for minimal access surgery.

     

  • A surgeon who spends time gradually obtaining adequate exposure is typically rewarded with less destructive implant removal as the degree of exposure equates to implant interface access.

     

  • Excision of fibrous and synovial tissues from the medial and lateral gutters of the knee facilitates soft tissue mobility and hence implant access.

     

    P ITFALLS

  • Avoid eversion of the patella as this may lead to infrapatellar ligament avulsion from the tubercle.

   

• Typically, femoral and tibial implant extraction is performed with the knee flexed 90° or greater.

  Portals/Exposures

• To the extent that revision success is contingent upon the restoration of the patient’s anatomy and presentation of the ligament structures, the overriding goal for component removal is to extract the implants with the least possible damage to these structures (Fig. 5).

  Procedure

• As a general rule when removing well-fixed implants, it is important that the surgeon disrupt the prosthesis-bone interface as completely as access will allow prior to attempting extraction. Failure to heed this rule will lead to excessive bone loss.

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Instrumentation

• Instrumentation required for components removal is basic to most operating theaters.

  • Thin-bladed oscillating saws

  • Gigli saws

  • Thin osteotomes

  • High-speed burrs

  • Small drills

• Specialized instruments such as ultrasonic devices for removing polymethylmethacrylate may be helpful with well-integrated diaphyseal cement.

• Disimpaction tools are commercially available with “universal” adaptors. These tools allow the surgeon to apply axial loads to the implant.

Removing Well-Fixed Implants

FIGURE 5

FIGURE 6

Step 1: Use of Osteotomes

• Thin, flat osteotomes in widths between ¼ and 1 are quite useful in disrupting the interface between the prosthesis and cement (Fig. 6).

• Angled osteotomes can be used to access hard-to-reach interfaces such as those with the posterior tibia or posterior femoral condyle.

• Osteotomes can be progressively stacked to lift an implant (Fig. 7). The widest osteotome is against the bone to disperse load.

  Step 2: Use of Oscillating Saws

• Narrow oscillating blades are useful tools for quickly disrupting the prosthesis-cement interface and are the first instrument of choice when removing cementless implants (Fig. 8).

• Pitfalls associated with oscillating saws include deflection of the blade into soft cancellous bone or difficulty navigating pegs, posts, or chamfer geometries.

P EARLS

• Know the implant being removed so appropriate screwdrivers or removal tools will be available.

   

• Osteotomes or small oscillating saws are directed toward the prosthesis-bone or prosthesis-cement interface.

   

• Oscillating saws may be preferable in cementless implants as osteotomes tend to crush the soft bone beneath a well-fixed, cementless implant.

   

• Curved osteotomes and Gigli saws are helpful in reaching intercondylar or posterior condyle geometries.

   

• “Rock” the implant off the distal femur with alternating blows from the medial and lateral side to avoid fracturing a femoral condyle.

   

• Placement of the femoral implant back on the femur after removal may protect the femoral bone and provide good retractor leverage to deliver the tibia forward.

   

  P ITFALLS

• Three obstacles to tibial component removal are (1) exposure to the interfaces behind the keel, (2) access to the posterior lateral corner, and (3) clearance of the tibia beneath the femur for axial disimpaction. All can be overcome with extensive exposure techniques.

   

• Avoid levering or prying a patella implant off of the host bone as this risks fracture and extensor mechanism disruption.

Removing Well-Fixed Implants

FIGURE 7

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FIGURE 8

Step 3: Use of Gigli Saws

• Gigli saws are useful interface disruption tools when navigating posterior condylar geometries (Firestone and Krackow, 1991), working around lugs, or releasing the posterior lateral corner beneath the tibial tray (Fig. 9A and 9B).

• These saws can skive quite easily if the surgeon fails to keep them in apposition with the prosthesis.

• Multiple saws should be available as wire breakage is common.

• Gigli saws are particularly useful in disruption of fibrous membrane of a fibrous fixed implant.

   

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  Removing Well-Fixed Implants

   

  Step 4: Use of High-Speed Burrs

  • Occasionally, well-fixed stems cannot be disimpacted without risking significant bone loss.

  • Metal cutting burrs can be used to section the implant to allow interface access (Fig. 10).

  • High-speed burrs are useful in partitioning, fractionating, or removing bone cement.

    Step 5: Component Removal

  • When all components are slated for removal, begin with removal of the polyethylene tibial insert. The space gained will facilitate component access.

  • The femoral component is usually addressed next as clearance of the femoral implant aids axial distraction of the tibial implant. Disimpaction is achieved with a punch or universal extraction device (Fig. 11).

A B

FIGURE 9

FIGURE 10

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Removing Well-Fixed Implants

FIGURE 11

• Femoral implants with well-fixed cemented stems typically will disimpact from the cement. When this does not occur despite disruption of the distal interfaces, the surgeon may either cut the stem housing free from the implant to gain access to

  the stem, or perform an anterior femoral opening osteotomy. In the latter instance, the osteotomy is wired closed and bypassed with the revision constraint.

• As with the femur, removal of well-fixed tibial stems that do not disengage with axial distractions may

FIGURE 12

287

Removing Well-Fixed Implants

A B

FIGURE 13

FIGURE 14

be accessed via cutting of the tray (Fig. 12) or an extended tibial tubercle osteotomy.

• Thin, oscillating saws are particularly helpful in removing all polyethylene patella components.

  • Metal cutting wheels may be used to transect well-fixed porous ingrown pegs of metal-backed patellar designs (Fig. 13A and 13B).

  • In aseptic cases these pegs can remain, thereby avoiding risk of further bone loss (Fig. 14).