Templating In Total Hip Arthroplasty Research Articles

Technical Notes and Tips: Acetate Templating for Total Hip Arthroplasty Using PACS

Technical Notes and Tips: Acetate Templating for Total Hip Arthroplasty Using PACS

Evaluation of the Accuracy and Use of X-Ray Markers in Digital Templating for Total Hip Arthroplasty

Despite benefits of digital templating, digital image acquisition techniques often make image magnification unknown and variable. We assessed the accuracy of digital x-ray scaling devices based on position. Radiographs of 106 total hip arthroplasty (THA) patients were studied to determine the accuracy of 2 digital x-ray markers at 1 of 4 positions by comparing true to expected x-ray magnification. The Pearson r coefficient was calculated as an indicator of measurement correlation between investigators. Greater accuracy was obtained for markers placed at the greater trochanter without skin overlap than for markers placed with soft tissue or bone overlap on x-ray. Flexible positioning markers provided greater accuracy than adhesive markers. Based on our data, we suggest positioning at the greater trochanter without skin overlap on x-ray and suggest flexible positioning over adhesive marker use.

Digital templating in total hip arthroplasty with the Mayo stem

In 40 patients undergoing total hip arthroplasty with the Mayo femoral stem we studied how preoperative digital templating corresponded to the actual intraoperative choice of implant size, position, offset and restoration of leg length. The preoperatively planned sizes of the components showed a high rate of coincidence with the sizes used intraoperatively [Intraclass Correlation Coefficient (ICC) 0.661-0.810]. However, the agreements in offset and CCD correction were poor (ICC 0.476, 0.253). This could be statistically attributed to the change in the distance from the medial margin of the stem to the medial margin of the medial femoral cortex and the height of osteotomy. The agreement in leg length correction was moderate (ICC 0.583), which was attributed to the change in the hip rotation center and the height of osteotomy. Careful preoperative planning was useful for accurate size choice of the Mayo prosthesis. Factors such as the height of osteotomy and the distance from the medial margin of the stem to the medial margin of the medial femoral cortex in relation to the position of the Mayo stem should be taken into account in order to restore ideal offset and leg length.

Preoperative templating of femoral components on plain X-rays

Preoperative femoral templating for total hip arthroplasty (THA) has been performed by antero-posterior radiographs of both hips which should be taken with the femur rotated internally to reduce the effect of femoral anteversion. However, there is no criterion to evaluate the optimal rotated radiograph. Here, we quantitatively investigated 50 femora whether the thickness of the lesser trochanter (TLT) was useful when evaluating the femoral rotation, and assessed the effect of prosthetic templating on the inappropriate rotated radiographs. We assessed 50 femora of 46 consecutive osteoarthritic patients using "synthetic X-ray" based on computer tomography (CT) images, which can be displayed as virtual plain radiographs with any magnification and any projected direction such as plain radiographs. We made four femoral radiograph groups of different rotation prepared (neutral, 15 degrees, 30 degrees, and 45 degrees external rotation), and measured the TLT. We also templated femoral stem on the different rotated synthetic X-ray of each patient, and investigated the effect of inappropriate rotated radiograph by the measurement of the position and the size of the stem. Seventy-four percent of the neutral rotational group had less than 5 mm of the TLT. While 30 degrees and 45 degrees external rotation group had few cases with less than 5 mm of the TLT. Compared to the neutral group, smaller stem size was selected in more than 80% cases of 30 degrees and 45 degrees external rotational group, and the stem position in these two groups was more than 5 mm proximally. We suggest that when templating femoral stem, this criterion "the TLT is less than 5 mm" reduces some risks by inappropriate rotated radiograph.

Digital Templating in Total Hip Arthroplasty

Preoperative templating for total hip arthroplasty requires precision and accuracy. The current method of acetate overlays is subject to errors in magnification. Digital radiography permits the use of software programs that calculate the x-ray magnification with precision and then adjust the templates to match the exact magnification. A reproducible set of steps is described that allows a surgeon to preoperatively template in the digital environment.