Patients with no functional improvement after total knee arthroplasty show different kinematics.
OBJECTIVE
As many as 20 % of all patients following total knee arthroplasty are not satisfied with the result. Rotational alignment is one factor thought to affect clinical outcome. The purpose of this study was to assess relationships between prosthesis rotational alignment, function score and knee kinematics after TKA.


METHODS
In 80 patients a cemented, unconstrained, cruciate-retaining TKA with a rotating platform was implanted. Rotational alignment was measured using CT-scans. Kinematics was assessed using fluoroscopy images.


RESULTS
Seventy-three patients were available for follow-up after two years. Nine patients had more than 10° rotational mismatch between the femoral and tibial component in the postoperative CT scans. These patients showed significantly worse results in the function score. While the normal patients with less than 10° rotational mismatch improved from a mean pre-operative 55 points to a mean 71 points at follow-up, the group with more than 10° mismatch deteriorated from a mean 60 points pre-operatively to a mean 57 points at follow-up. The pattern of motion during passive flexion from approximately 0° to 120° was quite different. While external rotation steadily increased with knee flexion in the normal group, there was internal rotation between 30° and 80° of flexion in the group with more than 10° rotational mismatch.


CONCLUSIONS
Rotational mismatch between femoral and tibial components exceeding 10° resulted in different kinematics after TKA. It might contribute to worse clinical results observed in those patients and should therefore be avoided.
Department of Orthopaedic Surgery, University Hospital Carl Gustav Carus, Medical Faculty of the Technical University of Dresden, Fetscherstr 74, 01307 Dresden, Germany. Joerg.Luetzner@uniklinikum-dresden.de
Jörg
J
Lützner
Stephan
S
Kirschner
Klaus-Peter
KP
Günther
Melinda K
MK
Harman
D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects / Q000379:methods*; D001696:Biomechanical Phenomena; D017760:Bone Malalignment / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology; D005260:Female; D005269:Femur / Q000473:pathology; D006801:Humans; D007719:Knee Joint / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D007720:Knee Prosthesis; D008297:Male; D017060:Patient Satisfaction; D011183:Postoperative Complications / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D011474:Prosthesis Design; D016059:Range of Motion, Articular; D020127:Recovery of Function; D012399:Rotation; D013977:Tibia / Q000473:pathology; D017211:Treatment Failure; D016896:Treatment Outcome