Implant Removal
Ashton H. Goldman
Kevin I. Perry
Key Concepts
Bone preservation is critical to ensure host bone for uncemented metaphyseal fixation augmented with either uncemented or cemented diaphyseal fixation in the revision setting.
For the removal of cemented implants, first define and delineate the implant/cement interface, then disrupt the implant/cement interface for a few millimeters with a saw, and then use osteotomes to complete interface disruption.
Do not try to remove a component before complete interface disruption.
Often the patellar component can be retained. Scenarios that require patella removal include significant patellar wear, patellar component loosening, or periprosthetic joint infection.
The patellar tendon should be protected throughout the entirety of the case.
Sterile Instruments and Implants
Standard knee retractors
Sagittal saw
Gigli saw for removal of uncemented implants
Flexible and stiff osteotomes of multiple widths
Moreland type osteotomes
6.5 mm and pencil-tip burrs
Cerclage wires if osteotomy is performed
Metal cutting burr (if needed)
Diamond cutting wheel (if needed)
Surgical Approaches
A standard extensile medial parapatellar approach is recommended.
A quadriceps snip can be performed and is recommended for the stiff knee revision. No change in postoperative protocols is necessary when performed.
A tibial tubercle osteotomy (TTO) can be useful in cases with severe patella baja or with a well-fixed long press fit or cemented stem to facilitate implant removal.
Minimally invasive approaches are not recommended.
Preoperative Planning
Anteroposterior and lateral radiographs of the entire implants aid with identification of current implants, fixation methods, as well as anatomical features that may increase difficulty in implant removal (i.e., patella baja).
Certain implants have specific locking mechanisms on the polyethylene liner or have modular connections where implant-specific extraction devices are useful.
Osteolysis is always underestimated on preoperative films and must be considered. A metal suppression computed tomography scan may sometimes be useful to more accurately assess bone loss.
Plan for the specific implant that will be utilized at the time of revision and consider a backup plan. Often higher levels of constraint are needed. If substantial femoral osteolysis is present, then a hinge should be available in case either collateral ligaments is compromised.
Bone, Implant, and Soft Tissue Techniques
Perform a standard approach to the knee.
After medial parapatellar arthrotomy, clear the gutters and evaluate the need for a quadriceps snip or TTO to protect the extensor mechanism.
Polyethylene
Remove the modular polyethylene insert with implant-specific tools that disrupt the locking mechanism, or it can be removed with an osteotome and mallet with relative ease. If removing a varus-valgus constrained insert, often the metal support post must be removed before removing the polyethylene insert.
For an all-polyethylene component a saw can be utilized at the implant-cement interface to separate the keel and facilitate removal.
Femoral Component
Define femoral interface and use a small saw blade at the implant-cement interface to initiate disruption. This is not possible for the posterior condyles of the femur. This can also be accomplished with a pencil-tip burr (Figures 61.1 and 61.2).
Use flexible osteotomes in the implant-cement interface to connect the medial and lateral sides of the anterior flange. In the cruciate retaining component, small osteotomes can be used in the central cut out to further aid with bone preservation (Figures 61.3 and 61.4).Related posts:
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