Digital Templating Accuracy in Hip Replacement: Clinical Research

Title: The Accuracy of Digital Templating in Primary Total Hip Arthroplasty

Authors: S tephen R. Kantor, MD and Ivan M. Tomek, MD

Department of Orthopaedic Surgery
Dartmouth-Hitchcock Medical Center and Dartmouth Medical School
Lebanon, NH, USA

Purpose:

The purpose of this study was to assess the ability of digital templating software to accurately predict implant size requirements for primary total hip arthroplasty.

Methods:

• 135* consecutive primary total hip arthroplasties were templated preoperatively using the TraumaCad™ templating software (Orthocrat Ltd, Israel).

• Hips were templated using magnification-calibrated radiographs. For each hip, an AP pelvis, AP and false profile projection were used for the preoperative assessment.

• All acetabuli implanted were either Trilogy Trabecular Metal (Zimmer), Trident PSL (Stryker), or Pinnacle (DePuy) implants.

• Femoral stems were either Alloclassic or ML-Taper (Zimmer), Accolade or Exeter (Stryker), or Corail (DePuy).

• All hips were implanted by a single surgeon using either a MIS posterior or modified MIS Watson-Jones approach.

• Postoperatively, the predicted implant size was compared to the actual components selected at the time of surgery.

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Title: Accuracy of digital (Filmless) Templating in Total Hip Replacement
Article Type: Clinical

Authors: William Murzic, MD; Priya Hirway, MS; Paula Lowe , RN; Zeev Glozman

Abstract: Background: Preoperative templating has been useful to determine the correct size prosthesis in
cementless total hip replacement. Typically this has been accomplished using acetate overlays on plain
radiographs with good success. With the advent of digital x-ray and PACS, software has been developed
that incorporates the templates of many different vendors into a program that enables the surgeon to
measure without radiographs, the size of the intended femoral and acetabular components. We compared
the two techniques to assess the relative accuracy of digital templating.

Methods: A total of 40 cases were analyzed comparing the preoperative templated sizes with the actual
size prosthesis implanted at surgery. Both acetabular and femoral component sizes were reviewed.
Magnification markers were used in all cases and all templating and surgery was performed by one surgeon.
Twenty hips that were templated using radiographs were compared to twenty hips that were done using
digital templating software on a pacs workstation (TraumaCad, Novapacs, Salt Lake City UT) A synergy
femoral component and a Reflection cup (Smith and Nephew, Memphis TN) were used in all cases.
Preoperative templating data was compared to prosthesis size on operative notes.

Results: Using standard templating, thirty percent of implanted stems were the same size as templated, 65
percent were within one size, and 5 percent were within 2 sizes. With digital templating 60 percent were the
same size, 35 percent were within one size, and 5 percent were within 2 sizes. For acetabular components
using acetate overlays, 50 percent of implanted cups were the same size as templated, 45 percent were
within 2 mm, and 5 percent within 4 mm. Digitally, 45 percent were the identical size, 35 percent were within
2 mm, and 20 percent within 4mm. All postoperative films show good fit of the components and there were
no intraoperative or postoperative fractures.

Conclusions: This preliminary study, using recently developed digital templating software, showed no
significant differences when compared to the standard technique using magnified radiographic overlays.
Use of this templating software was safe and effective.
Clinical Relevance: In total hip replacement, preoperative templating provides valuable information about
anatomy and appropriate implant size. Having the information prior to surgery provides surgical accuracy,
reduces fractures, and decreases operative time. With the increasing demand for digital imaging/pacs,
digital templating will become more prevalent.