Alignment for total knee replacement: a comparison of kinematic axis versus mechanical axis techniques. A cadaver study.
OBJECTIVE
Standard instrumentation tries to reproduce mechanical axes based on mechanical alignment (MA) guides. A kinematic alignment (KA) technique derives its plan from pre-operative MRI-measurements. This matched-pair cadaveric study compared the resulting postoperative alignments.


METHODS
A prospective series of 12 torsos were acquired for a total of 24 limb specimens including intact pelvises, femoral heads, knees, and ankles.The cadavers received MRI scans to manufacture the kinematic alignment cutting guides. Two investigating surgeons performed total knee arthroplasties on randomly chosen sides using MA instruments. On the contralateral sides, KA cutting guides were used. A navigation system was used to measure final alignment.


RESULTS
The overall alignment showed no significant differences between the systems. In the MA group the differences between the planned and the final implantation regarding overall limb alignment ranged between 0.2° and 6.2°. In the KA group the differences between the planned and final implantation regarding overall limb alignment ranged between 0.3° and 9.1°. The differences of the deviation from plan for overall limb alignment showed no significant differences between the methods.


CONCLUSIONS
The different alignment strategies resulted in variations of the combinations of the three-dimensional component position on the femur and the tibia. However, the legs were aligned within comparable range for both chosen techniques.
Department for Orthopaedic Surgery, Unit of Experimental Orthopaedics, Medical University, 6020 Innsbruck, Austria. michael.nogler@i-med.ac.at
Michael
M
Nogler
William
W
Hozack
Dermot
D
Collopy
Eckart
E
Mayr
Gregory
G
Deirmengian
Kathrin
K
Sekyra
D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation / Q000379:methods*; D001696:Biomechanical Phenomena / Q000502:physiology; D002102:Cadaver; D005260:Female; D005269:Femur / Q000033:anatomy & histology / Q000502:physiology; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000517:prevention & control*; D017755:Prosthesis Fitting / Q000379:methods*; D012399:Rotation; D025321:Surgery, Computer-Assisted / Q000379:methods*; D013977:Tibia / Q000033:anatomy & histology / Q000502:physiology; D014057:Tomography, X-Ray Computed