[Diagnosis specific differences in knee joint geometry. A challenge for the correct axial implantation of long stems in total knee arthroplasty].
BACKGROUND
Arthrotic deformities with changes in knee geometry can produce difficulties in implanting long stem knee prosthesis systems using intramedullary alignment. They can result in incorrect lower limb axis and prosthesis positioning. The aim of the presented study was to measure knee geometry in patients with varus and valgus gonarthrosis in order to define diagnosis related differences.


METHODS
A total of 75 patients with indication for total knee arthroplasty were divided in two groups using the weight bearing lower limb axis: patients with varus gonarthrosis (n=43) and with valgus gonarthrosis (n=32). Angles and extensions, important for knee prosthesis implantation, were measured, digitalized and analyzed. The results were investigated for diagnosis specific differences.


RESULTS
After regulation of the measured extension in mean femur/tibia lengths, significant diagnosis specific differences were found: femur condyles were widened towards pathologic weight bearing (P<0.044), and the mechanical tibia axis of the varus gonarthrosis group is transferred to the lateral side (P<0.046) and in projection over the lateral internal cortical substance.


CONCLUSIONS
The significant differences in deformed arthrotic knees indicate that for an optimal postoperative result the use of standard implants is not always sufficient. Modular knee prosthesis systems can provide adequately for individual demands.
Goebel
M
M
Klinik für Orthopädie und Sportorthopädie, Klinikum rechts der Isar, Technische Universität München. michaelgoebel@yahoo.de
Burgkart
R
R
Gerdesmeyer
L
L
Diehl
P
P
Schmitt-Sody
M
M
Plötz
W
W
Gradinger
R
R
D000328:Adult; D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation* / Q000379:methods*; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D005260:Female; D006801:Humans; D016916:Joint Deformities, Acquired / Q000175:diagnosis* / Q000601:surgery*; D007719:Knee Joint / Q000002:abnormalities* / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D025321:Surgery, Computer-Assisted / Q000379:methods*; D016896:Treatment Outcome