title: Evaluation of implant position and knee alignment after patient-specific unicompartmental knee arthroplasty.
abstract: Implant positioning and knee alignment are two primary goals of successful unicompartmental knee arthroplasty. This prospective study outlines the radiographic results following 32 patient-specific unicompartmental medial resurfacing knee arthroplasties. By means of standardized pre- and postoperative radiographs of the knee in strictly AP and lateral view, AP weight bearing long leg images as well as preoperative CT-based planning drawings an analysis of implant positioning and leg axis correction was performed.The mean preoperative coronal femoro-tibial angle was corrected from 7° to 1° (p<0.001). The preoperative medial proximal tibial angle of 87° was corrected to 89° (p<0.001). The preoperative tibial slope of 5° could be maintained. The extent of the dorsal femoral cut was equivalent to the desired value of 5mm given by the CT-based planning guide. The mean accuracy of the tibial component fit was 0mm in antero-posterior and +1mm in medio-lateral projection. Patient-specific fixed bearing unicompartmental knee arthroplasty can restore leg axis reliably, obtain a medial proximal tibial angle of 90°, avoid an implant mal-positioning and ensure maximal tibial coverage.
authors.affiliation: Orthopaedic Surgery, University of Regensburg, Germany. franz.koeck@klinik.uni-regensburg.de
authors.forename: Franz Xaver
authors.initials: FX
authors.lastname: Koeck
authors.forename: Johannes
authors.initials: J
authors.lastname: Beckmann
authors.forename: Christian
authors.initials: C
authors.lastname: Luring
authors.forename: Bjoern
authors.initials: B
authors.lastname: Rath
authors.forename: Joachim
authors.initials: J
authors.lastname: Grifka
authors.forename: Erhan
authors.initials: E
authors.lastname: Basad
mesh_terms: D000328:Adult; D000368:Aged; D053587:Arthrometry, Articular; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D017760:Bone Malalignment / Q000175:diagnosis* / Q000517:prevention & control; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology / Q000601:surgery*; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000503:physiopathology / Q000601:surgery; D011183:Postoperative Complications; D011446:Prospective Studies; D011474:Prosthesis Design; D015203:Reproducibility of Results; D025321:Surgery, Computer-Assisted / Q000295:instrumentation / Q000379:methods; D016474:Weight-Bearing