Abstract
Introduction
The use of stems in TKA revision surgery is well established. Stems off-load stress over a broad surface area of the diaphysis and help protect the metaphyseal interface areas from failure. Stems can provide an area of extra fixation.
Uncemented Stems
Pros and Cons
Advantages
(1) Expeditious, (2) Compatible with intramedullary based revision instrumentation (3) Easy to remove if necessary (4) By filling diaphysis they help guarantee axial alignment
Disadvantages
(1) They help off load stress, but how much fixation do they really provide? (2) They don't fit all canal deformities, and under some circumstances can actually force implants into malalignment. (3) ? potential for end of stem pain
Cemented Stems
Pros and Cons
Advantages
(1) Cemented stem adds fixation in fresh metaphyseal and diaphyseal bone. (2) Proven 10-year track record. (3) Allow the surgeon to adjust for canal geometry abnormalities
Disadvantages
(1) More difficult to remove, if required. (2) They don't fill the canal so they don't guarantee alignment as well under most circumstances.
Results
Favorable results with uncemented and cemented stems have been reported in several series. Cemented stems have longer term data.
Technique Issues
Uncemented Stems
(1) Take advantage of offset bolts, tibial trays, stems to fit the stem/implant to the patient's anatomy. (2) Don't let the stem force you into suboptimal implant position. (3) Longer stems can be narrower but help engage more diaphysis. (4) Do a good job of restoring/uncovering cancellous bone in metaphysis for cement interdigitation. The cement provides the fixation.
Cemented Stems
(1) Intra-operative x-ray with trials helps guarantee optimal alignment. (2) Use cement restrictors. (3) Cement tibia/femur separately
Metaphyseal Fixation
(1) Area of new emphasis. (2) Cones and sleeves can improve cemented and uncemented fixation.
