Campbell, D.Johnson, L.West, S.2007-07-102007-07-102006ANZ Journal of Surgery, 2006; 76(9):782-7871445-14331445-2197http://hdl.handle.net/2440/35744<h4>Background</h4>Unicompartmental knee arthroplasty is a popular alternative to total knee replacement in selected patients. Component alignment has not yet been described by computer-assisted tomography (CAT) imaging techniques; these have been developed for total knee arthroplasty analysis. The aims of this study were to report two new technologies; a new unicompartmental knee arthroplasty system was radiographically assessed with a new CAT scan protocol.<h4>Methods</h4>In a consecutive cohort study, 60 knees were analysed by the 'UniCAT Protocol'. Patients were implanted with a unicompartmental knee arthroplasty system that uses a unique ligament tensor for femoral component alignment. The uniCAT protocol requires a long anteroposterior and lateral scout scan to measure limb alignment and component orientation. A spiral computer-assisted tomography at the knee is used to measure component rotation. The total scan time was 20 s with a calculated unshielded radiation dose of 1 mSv or less.<h4>Results</h4>The mechanical axis had a mean of 2.7 degrees varus. Femoral components were implanted with a mean of 0.37 degrees valgus and 1.3 degrees flexion. Tibial components were implanted with a mean 3.47 degrees varus and 5.1 degrees posterior slope. Femoral components were externally rotated a mean of 3.36 degrees, tibial components were externally rotated 6.59 degrees from the posterior tibia and 5.68 degrees from the transepicondylar axis.<h4>Conclusion</h4>The UniCAT protocol uses less radiation than whole-limb spiral scans and is a method that can be used with all modern computer-assisted tomography machines. The coronal and sagital alignment results compare favourably with previous published reports without computer-assisted tomography. Component rotation has not previously been reported and its implications are yet to be defined.enKnee JointHumansOsteoarthritis, KneeTomography, X-Ray ComputedArthroplasty, Replacement, KneeCohort StudiesJournal article002006241410.1111/j.1445-2197.2006.03867.x0002403368000062-s2.0-3374710230251629Campbell, D. [0000-0002-1572-9529]