Tibial component with and without stem extension in a trabecular metal cone construct.
OBJECTIVE
The 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.


METHODS
Tibial 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.


RESULTS
Tibial 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)].


CONCLUSIONS
Tibial 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.


METHODS
II.
Department of Orthopaedics, University Medical Center Groningen, University of Groningen, PO Box 30.001, 9700 RB, Groningen, The Netherlands. M.F.Meijer@umcg.nl.
Marrigje F
MF
Meijer
Department of Orthopaedics, University Medical Center Groningen, University of Groningen, PO Box 30.001, 9700 RB, Groningen, The Netherlands.
Alexander L
AL
Boerboom
Department of Orthopaedics, University Medical Center Groningen, University of Groningen, PO Box 30.001, 9700 RB, Groningen, The Netherlands.
Martin
M
Stevens
Department of Trauma Surgery, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
Inge H F
IHF
Reininga
Orthopedic Research Laboratory, Radboud University Medical Center Nijmegen, Nijmegen, The Netherlands.
Dennis W
DW
Janssen
Laboratory of Biomechanical Engineering, University of Twente, Enschede, The Netherlands.
N
N
Verdonschot
Department of Orthopaedics, University Medical Center Groningen, University of Groningen, PO Box 30.001, 9700 RB, Groningen, The Netherlands.
Sjoerd K
SK
Bulstra
D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods; D001696:Biomechanical Phenomena; D015519:Bone Density; D002102:Cadaver; D005260:Female; D006801:Humans; D007720:Knee Prosthesis; D008297:Male; D008670:Metals; D011474:Prosthesis Design; D012086:Reoperation; D013314:Stress, Mechanical; D013977:Tibia / Q000502:physiology* / Q000601:surgery*
D008670:Metals
Bone defect; Cone; Stem extension; TKA; TM; Tibial component; Total knee arthroplasty; Trabecular metal