Electronic Letters to:

Knee: R. W. Trickett, P. Hodgson, M. C. Forster, and A. Robertson The reliability and accuracy of digital templating in total knee replacement J Bone Joint Surg Br 2009; 91-B: 903-906 [Abstract] [Full text] [PDF]

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Authors' reply:

Ryan W Trickett, Paul Hodgson, Mark C. Forster, and Angus Robertson.   (16 September 2009)

The reliability and accuracy of digital templating in total knee replacement

Chris Hoare, Alistair Tindall, Samuel Orakwe   (7 August 2009)

Authors' reply: 16 September 2009
Ryan W Trickett, Specialty Registrar Trauma & Orthopaedics Cardiff & Vale Orthopaedic Centre, Cardiff, Paul Hodgson, Mark C. Forster, and Angus Robertson. Send letter to journal: Re: Authors' reply: ryan{at}trickett00.fsnet.co.uk Ryan W Trickett, et al.	Sir, We read the comments from Hoare et al with interest and we thank them for their letter. The templating process was the same for both senior authors (MF and AR). The femoral components were templated using both the anteroposterior (AP) and lateral radiographs. However, where conflict between the radiographs existed, preference was given to the lateral radiograph as the key element of sizing the femoral component is not to overstuff the patellofemoral joint or notch the femur. We did find that the lack of congruence of the femoral condyles often led to a compromise in the templating of the most appropriate size. This appeared to be due to the larger distal radius of the lateral femoral condyle. We found that the lack of congruence was primarily concerned with the anterior and distal projection of the femoral condyles. All of the patients in our study who were felt to have had an oversized implant inserted were analysed separately. We postulated that the reason for the oversized femoral component had been a variance in the ML:AP ratio of the distal femur. It is recognised that there is a subgroup of patients, usually females, in whom this ratio varies. These patients were analysed separately to determine the accuracy of templating in this group - four from five patients had been correctly templated. It is likely that the altered distal femoral ratio is implicated in the correct (compared with implanted) templating of an oversized femoral component. Gender-specific knee implant systems may have a role in this group of patients. R.W. Trickett, SpR Trauma & Orthopaedics, P. Hodgson, M.C. Forster, A. Robertson, Cardiff & Vale Orthopaedic Centre, Cardiff, UK.
The reliability and accuracy of digital templating in total knee replacement 7 August 2009
Chris Hoare, Speciality Registrar, Trauma and Orthopaedics Queen Elizabeth Hospital, Woolwich, London, Alistair Tindall, Samuel Orakwe Send letter to journal: Re: The reliability and accuracy of digital templating in total knee replacement chrishoare{at}doctors.org.uk Chris Hoare, et al.	Sir, We read this paper with interest. The authors state that the femoral component was consistently templated less accurately than the tibial component and suggest difficulty in assessing the osseous landmarks due to differing outlines of the medial and lateral femoral condyles on the lateral radiograph as an explanation. We feel the position of the posterior femoral condyles in relation to one another does have an impact on the accuracy of templating for the femoral component. In an unpublished study of 135 total knee replacements in our institution, lack of congruency of the posterior femoral condyles had a negative impact on the accuracy of templating. We would be interested to know whether the authors took the templated size of femoral component from the antero-posterior (AP) or lateral radiographs. It is not stated in the text and the article shows images of both AP and lateral radiographs with templated femoral components. The authors have also suggested there may be a subgroup of patients for whom the AP and medio-lateral dimensions of the distal femoral differ from the general population. We would be grateful to hear the authors' response to this. C. Hoare, Speciality Registrar, Trauma and Orthopaedics, A. Tindall, S. Orakwe, Queen Elizabeth Hospital, Woolwich, London, UK.