Digital templating in hip replacement with and without radiological markers

Abstract

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.

A comparison of four systems for calibration when templating for total hip replacement with digital radiography

“…8 A comparison of the use of a steel ball as a calibration object with measurement of the object-film-distance revealed a similar accuracy for the two methods, with a mean absolute measurement error of 2.6% for the calibration object and 2.8% for measurement of the object-film-distance (p = 0.75). 9 In two studies the size of the implant was compared with the size digitally templated in retrospect on post-operative radiographs by a blinded observer. 10,11 In the first study the correct sizing was found in 27% of the femoral components with 79% to within ± one size and 23% of acetabular components with 61% to within ± one size, with low intra-and interobserver reliability values.…”

É importante saber onde posicionar o marcador esférico para o planejamento digital de artroplastia de quadril?

“…Estudos que analisam radiografias para planejamento de artroplastia utilizam diferentes métodos de posicionamento e de marcadores sem justificar a escolha, posicionando entre as coxas ou ao nível do trocânter maior. 6,11,14,15,21 Gamble et al 8 não especificam a técnica do posicionamento, apenas indicam a região. Kosashvili et al 22 não utilizaram qualquer marcador e apenas padronizaram a magnificação em 115% para fins práticos, com pouca interferência no resultado final.…”

“…A calibragem da imagem foi feita com a identificação de 3 pontos periféricos da cabeça da prótese, cujo diâmetro era conhecido, localização centrada na articulação e confirmada com a formação de um círculo em torno da cabeça. 9,15 Após a calibragem, a medição dos marcadores foi realizada com a identificação de 3 pontos periféricos e confirmada com o círculo em torno de cada marcador.…”

Retrospective Comparative Study of the Influence on Quality of Primary Total Hip Arthroplasty by the EndoCert-Certification System in a Communal Hospital

“…Undersizing can lead to early loosening. Oversizing is associated with an increased risk of intraoperative periprosthetic fractures [17,18]. The results reveal no significant differences in the groups with respect to cup inclination angle and stem alignment, however, taking the discrepancy in both directions (rate of cup inclination angle > 50°or < 30°) into account, Group 1 demonstrates significantly poorer results with regard to acetabular cup positioning when no preoperative prosthesis planning was carried out, thus confirming the importance of prosthesis planning.…”