title: Assessment and validation of CT scanogram to compare per-operative and post-operative mechanical axis after navigated total knee replacement.
abstract: Our objective was to assess and validate low-dose computed tomography (CT) scanogram as a post-operative imaging modality to measure the mechanical axis after navigated total knee replacement. A prospective study was performed to compare intra-operative and post-operative mechanical axis after navigated total knee replacements. All consecutive patients who underwent navigated total knee replacement between May and December 2006 were included. The intra-operative final axis was recorded, and post-operatively a CT scanogram of lower limbs was performed. The mechanical axis was measured and compared against the intra-operative measurement. There were 15 patients ranging in age from 57 to 80 (average 70) years. The average final intra-operative axis was 0.56 degrees varus (4 degrees varus to 1.5 degrees valgus) and post-operative CT scanogram axis was 0.52 degrees varus (3.1 degrees varus to 1.8 degrees valgus). The average deviation from final axes to CT scanogram axes was 0.12 degrees valgus with a correlation coefficient of 0.9. Our study suggests that CT scanogram is an imaging modality with reasonable accuracy for measuring mechanical axis despite significantly low radiation. It also confirms a high level of correlation between intra-operative and post-operative mechanical axis after navigated total knee replacement.
authors.affiliation: Department of Trauma and Orthopaedics, Medway Maritime Hospital, Gillingham, Kent, UK. drmpkumar@hotmail.co.uk
authors.forename: Paraskumar
authors.initials: P
authors.lastname: Mohanlal
authors.forename: Sunil
authors.initials: S
authors.lastname: Jain
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging* / Q000601:surgery; D007720:Knee Prosthesis; D035002:Lower Extremity / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods; D019990:Perioperative Care / Q000379:methods; D011182:Postoperative Care; D011446:Prospective Studies; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D025321:Surgery, Computer-Assisted / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*; D016896:Treatment Outcome