Implant Removal in Revision Total Knee Arthroplasty




Algorithm


This algorithm presents the approach for implant removal in total knee arthroplasty.









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Chapter Synopsis


Implant extraction should be performed cautiously and with attention to avoiding iatrogenic damage. A systematic and preplanned approach obviates the need for unwanted intraoperative creativity.


Important Points


Be conservative in making your way through the bone–implant interface by using thin and flexible instruments. Make sure you undermine the implants as much as possible before slamming them out.


Surgical Pearls





  • Provide adequate exposure in order to reach the bone–implant interface.



  • Use thin and flexible sawblades or osteotomes.



  • Undermine the implants as much as possible.



  • Consider a tibial tubercle osteotomy or femoral slot in cases with well-fixed stems.



Surgical Pitfalls





  • Subtotal undermining can cause major damage to the underlying bone during component extraction.



  • Failure to address the well-fixed keel or stem may lead to fracture or inability to remove the implant.





Introduction


Component extraction is not always the easiest aspect of the revision procedure, and it can lead to unnecessary additional damage or increased complexity if performed without sufficient patience or attention.


No absolute truth or consensus exists regarding the optimal strategy for implant removal, and surgical practices may differ based on personal insights and experience. Supportive data from the literature are lacking on this subject.


It is obvious that implant extraction should be performed cautiously and with attention to avoid iatrogenic damage. A systematic and preplanned approach facilitates removal and also avoids the need for the surgeon to rely on his or her intraoperative creativity.


This chapter describes a step-by-step approach that can serve as a basis even for the inexperienced surgeon who is only occasionally confronted with revision total knee arthroplasty (TKA). My colleagues and I have used this algorithm since 2001 at our institution, and more than 450 revision TKAs have been performed following this protocol.


The algorithm consists of twelve consecutive steps that are executed always in the same order. The intention of this chapter is not to convince the reader to follow this algorithm meticulously but to suggest how component removal can be performed in a preplanned way that has provided excellent results.




Equipment


The following equipment is required:




  • Motorized oscillating saw



  • Thin flexible sawblades (width 15 to 20 mm)



  • Set of thin osteotomes (widths ranging from 7.5 to 40 mm)



  • System-specific (in situ) tibial insert introducer/extractor



  • Standby: cerclage wire set or large fragment screw set





Surgical Technique



Start by Removing the Polyethylene Insert


The arthrotomy of the knee usually does not achieve adequate exposure for revision TKA, and additional release of peripatellar adhesions and resection of scar tissue are often required. Removal of the polyethylene tibial insert can facilitate this process dramatically, because the tension in the peripatellar and femorotibial soft tissue structures will immediately become reduced by removal of the space-occupying insert ( Fig. 11.1 ). Extraction of the polyethylene insert is usually easy and can be performed with the use of a lever that is either implant specific or generic. For example, the tip of a standard Hohmann retractor inserted between the plastic and the baseplate serves well for this purpose. Systems using a screw or interlocking part can equally easily be dealt with by using the implant-specific instruments. Prior knowledge of the system specifications is required, and it is the responsibility of the surgeon to prepare accordingly.




FIGURE 11.1


Start by removing the polyethylene insert, because this will reduce capsular tension and increase the working space.


If a monoblock or all-polyethylene tibial component is in place, its postpone its removal until after removal of the femoral component. Its removal at this stage would be severely compromised because the femur is sitting in the way.



Use a Thin, Flexible Sawblade to Undermine the Anterior Femur


Once the insert has been removed and adequate exposure is obtained such that the femoral component can be approached on both the medial and the lateral side, the anterior aspect of the femoral component is addressed first. An oscillating, 15- to 20-mm, flexible sawblade is used to cut just below the component’s surface, first medial and then lateral, and from proximal to distal. The sawcut is advanced distally as much as possible until the pegs or the box is reached. The anterior chamfer and the distal femur are addressed identically, and the sawblade again is advanced until it touches the pegs or the box ( Fig. 11.2 ). Adequate exposure and soft tissue retraction is required at this stage so as not to damage the skin or soft tissues with the base of the saw.




FIGURE 11.2


Use a thin, flexible sawblade for undermining the anterior femoral component.



Work Around the Distal Femoral Pegs, Box, and Posterior Femur Using Thin Osteotomes


The oscillating saw cannot be used for the posterior aspect of the femoral component because of the risk of iatrogenic damage to the surrounding collateral ligaments and soft tissues. Instead, the posterior chamfer and posterior condyle are undermined with a thin osteotome (7.5 mm wide), taking care not to damage the surrounding soft tissues ( Fig. 11.3 ). Thin osteotomes are also used to work farther around the femoral pegs, the femoral box, and the notch area ( Fig. 11.4 ). Again, care is taken to undermine as much area as possible and to stay as close to the femoral component as possible. On the lateral side, this requires sufficient downward retraction of the extensor mechanism, which is not always easily achieved. Sometimes an extension of the arthrotomy may be necessary, for example by performing a rectus snip.


May 29, 2019 | Posted by in ORTHOPEDIC | Comments Off on Implant Removal in Revision Total Knee Arthroplasty
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