Abstract
PurposeThe purpose of this study was to investigate stability and strain distribution of a tibial plateau reconstruction with a trabecular metal cone while the tibial component is implanted with and without a stem, and whether prosthetic stability was influenced by bone mineral density. Trabecular metal cones are designed to fill up major bone defects in total knee arthroplasty. Tibial components can be implanted in combination with a stem, but it is unclear whether this is necessary after reconstruction with a trabecular metal cone. Implanting a stem can give extra stability, but may have negative side effects.MethodsTibial revision arthroplasties with trabecular metal cones were performed after reconstruction of a 2B bone defect according to the Anderson Orthopedic Research Institute classification. Components were implanted in seven pairs of cadaveric tibiae; one tibia of each pair was implanted with stem and the other without. All specimens were loaded to one bodyweight alternating between the medial and lateral tibial component. Implant-bone micro-motions, bone strains, bone mineral density and correlations were measured and/or calculated.ResultsTibial components without a stem showed only more varus tilt [difference in median 0.14° (P < 0.05)], but this was not considered clinically relevant. Strain distribution did not differ. Bone mineral density only had an effect on the anterior/posterior tilt [ρ: −0.72 (P < 0.01)].ConclusionTibial components, with or without a stem, which are implanted after reconstruction of major bone defects using trabecular metal cones produce very similar biomechanical conditions in terms of stability and strain distribution. If in vivo studies confirm that a stem extension is not mandatory, orthopaedic surgeons can decide not to implant a stem.Level of evidenceII.
Highlights
Major bone defects are frequently seen in revision total knee arthroplasty
Types 2B and 3 bone defects according to the classification of the Anderson Orthopedic Research Institute (AORI) [13,14,15, 26] are commonly seen during revision total knee arthroplasty (rTKA) and reconstruction of these major bone defects is usually done with metal augmentations in combination with a stem [6, 17, 27], which is shown to provide a mechanically stable reconstruction [10, 29, 33]
Trabecular metal (TM) cones are designed to fill up bone defects during TKA
Summary
Major bone defects are frequently seen in revision total knee arthroplasty (rTKA). Reasons for this may be design and removal of the primary prosthesis, original disease process, mechanism of failure and technical problems during the procedure. If enhanced stress-shielding occurs, adverse bone remodelling may follow in the long term, possibly influencing component fixation and inducing fractures [5, 22, 36]. Another disadvantage of the use of stems is elevated stress at the tip of the stem, which is associated with pain, lower post-operative clinical outcome and increased risk of periprosthetic fracture [1]
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