Radiographic accuracy in TKA with a CT-based patient-specific cutting block technique.
OBJECTIVE
Patient-specific instrumentation (PSI) technology for the implantation of total knee arthroplasty (TKA) has a rising interest in the orthopaedic community. Data of PSI are controversially discussed. The hypothesis of this paper is that the radiological accuracy of CT-based PSI is similar to the one of navigated TKA published in the literature.


METHODS
Since 2010, all 301 consecutively performed PSI TKAs (GMK MyKnee©) were included in this study. The radiological assessment consisted in a preoperative and postoperative standard X-ray and long-standing X-ray. Changes from the planned to the definitively implanted component size were documented. Postoperative analysis included limb alignment and position of femoral and tibial components (for varus/valgus and flexion or tibial slope).


RESULTS
The postoperative average hip-knee-ankle angle was 180.1° ± 2.0°. In the frontal plane a total of 12.4 % of outliers >3°, for the tibial components 4.1 % of outliers >3° and for the femoral components 4.8 % of outliers >3° were measured. A total of 12.3 % of outliers for posterior tibial slope and 9 % of outliers >3° for the femoral flexion were noted. 10.8 % of the 602 planned size components were adapted intraoperatively.


CONCLUSIONS
Although it is still unknown which limb axis is the correct one for the best clinical result, a technology providing the aimed axis in a most precise way should be chosen. Comparing the outcome of the current study with the data from the literature, there does not seem to be any difference compared to computer-assisted surgery.


METHODS
IV.
Department of Orthopaedics, Balgrist University Hospital, University of Zurich, Forchstrasse 340, 8008, Zurich, Switzerland, peter.koch@balgrist.ch.
P P
PP
Koch
D
D
Müller
M
M
Pisan
S F
SF
Fucentese
D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation / Q000379:methods*; D017760:Bone Malalignment / Q000000981:diagnostic imaging / Q000209:etiology / Q000517:prevention & control*; D005500:Follow-Up Studies; D006801:Humans; D021621:Imaging, Three-Dimensional; D007719:Knee Joint / Q000000981:diagnostic imaging* / Q000601:surgery; D007720:Knee Prosthesis; D017063:Outcome Assessment, Health Care; D011183:Postoperative Complications / Q000000981:diagnostic imaging / Q000517:prevention & control*; D011300:Preoperative Care / Q000295:instrumentation / Q000379:methods*; D012189:Retrospective Studies; D025321:Surgery, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D014057:Tomography, X-Ray Computed