title: Assessment of accuracy of marker ball placement in pre-operative templating for total hip arthroplasty.
abstract: We report the accuracy of positioning of the calibration ball in the process of pre-operative templating for total hip arthroplasty (THA). The ball should be placed in the coronal plane of the hip to provide suitable accuracy. We reviewed 112 post-operative THA radiographs where a calibration ball had been placed. We templated the femoral head size of the implant after calibrating the templating system from the ball. The calibrated femoral head diameter was compared to the known prosthetic head size. A percentage error was calculated. Overall, incorrect placement of the calibration ball resulted in a mean percentage error in templating of 6.8% (median 5.7%; range 0-26%). Such error carries implications with the templating process and may result in incorrect component sizes, leg lengths and offset.
authors.affiliation: Royal Lancaster Infirmary, Lancaster, United Kingdom.
authors.forename: Victoria F
authors.initials: VF
authors.lastname: Sinclair
authors.affiliation: Royal Lancaster Infirmary, Lancaster, United Kingdom.
authors.forename: James
authors.initials: J
authors.lastname: Wilson
authors.affiliation: University Hospital South Manchester, Manchester, United Kingdom.
authors.forename: Neil P M
authors.initials: NP
authors.lastname: Jain
authors.affiliation: Royal Lancaster Infirmary, Lancaster, United Kingdom.
authors.forename: David
authors.initials: D
authors.lastname: Knowles
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001175:Arthrography / Q000379:methods / Q000592:standards* / Q000706:statistics & numerical data; D019644:Arthroplasty, Replacement, Hip / Q000379:methods* / Q000592:standards*; D002138:Calibration / Q000592:standards; D061827:Dimensional Measurement Accuracy; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000601:surgery; D005270:Femur Head / Q000000981:diagnostic imaging / Q000601:surgery; D006622:Hip Prosthesis / Q000592:standards*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D056888:Patient Positioning; D011300:Preoperative Care / Q000379:methods / Q000592:standards* / Q000706:statistics & numerical data; D012189:Retrospective Studies; D016037:Single-Blind Method; D012984:Software / Q000592:standards
keywords: marker ball; position; templating; total hip arthroplasty