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Journal of Bone and Joint Surgery - British Volume, Vol 91-B, Issue 4, 459-462.
doi: 10.1302/0301-620X.91B4.21730  
Copyright © 2009 by British Editorial Society of Bone and Joint Surgery
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Digital templating in hip replacement with and without radiological markers

G. Heinert, DPhil, MA, MRCSEd, MRCSGlas, Specialist Registrar1; J. Hendricks, Postgraduate Certificate, Deputy Radiology Services Manager, Digital Templating Lead1; and M. D. Loeffler, MBBS, FRCS(Eng), FRCS(Orth), Clinical Director, Consultant Orthopaedic Surgeon2

1 Department of Radiology
2 Department of Trauma and Orthopaedics Colchester General Hospital, Turner Road, Colchester CO4 5JL, UK.

Correspondence should be sent to Dr G. Heinert at 16 Amwell Road, Cambridge CB4 2UH, UK; e-mail: Gideon.heinert{at}doctors.org.uk

Digital templating in hip replacement is commonly performed with radiological markers to determine the magnification. The latter can also be determined by measuring the distance from the x-ray focal spot to the object and the distance from the x-ray focal spot to the radiological cassette or image receptor. We used post-operative radiographs of total hip replacements and hemiarthroplasties from 22 patients to calculate the magnification using both methods. The accuracy of each method was ascertained by measuring the size of the head of the implant projected on to the radiographs and comparing the result with the known size recorded in the medical records.

The accuracy was found to be similar with a mean absolute measurement error of 2.6% (SD 1.4; 0.0% to 5.2%) for the radiological marker and 2.8% (SD 2.2; 0.4% to 10.1%) for the distance method (p = 0.75). The mean radiation dose for templating radiographs (pelvis and lateral of the hip) was similar when taken using a radiological marker (328 mSv SD 142) (n = 51) or using the distance measurement method (324 mSv SD 39) (n = 39) (p = 0.90).

We conclude that the distance measuring method is as accurate as the radiological marker method, but may avoid some of the disadvantages such as misplacement of the marker or placement outside the radiological field. It may also be more acceptable to the patient and radiographer.




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Digital templating in hip replacement with and without radiological markers
Ashwin Kulkarni, et al.
J Bone Joint Surg Br Online, 7 May 2009 [Full text]

(c) British Editorial Society of Bone and Joint Surgery All Rights Reserved
Registered charity no: 209299     Print ISSN: 0301-620X
Hip, Knee, Trauma, Upper limb, Foot & Ankle, Paediatrics, Oncology, Spine, Arthroplasty, General