Accuracy of radiographic measurement techniques for the Taylor spatial frame mounting parameters

Abstract

Aim The correction accuracy of the Taylor Spatial Frame (TSF) fixator depends considerably on the precise determination of the mounting parameters (MP). Incorrect parameters result in secondary deformities that require subsequent corrections. Different techniques have been described to improve the precision of MP measurement, although exact calculation is reportedly impossible radiologically. The aim of this study was to investigate the accuracy of intraoperative and postoperative radiographic measurement methods compared to direct MP measurement from TSF bone mounting. Methods A tibial Sawbone® model was established with different origins and reference ring positions. First, reference MPs for each origin were measured directly on the frame and bone using a calibrated, digital vernier calliper. In total 150 MPs measured with three different radiographic measurement techniques were compared to the reference MPs: digital radiographic measurements were performed using soft-copy PACS images without (method A) and with (method B) calibration and calibrated image intensifier images (method C). Results MPs measured from a non-calibrated X-ray image (method A) showed the highest variance compared to the reference MPs. A greater distance between the origin and the reference ring corresponded to less accurate MP measurements with method A. However, the MPs measured from calibrated X-ray images (method B) and calibrated image intensifier images (method C) were intercomparable (p = 0.226) and showed only minor differences compared to the reference values but significant differences to method A (p < 0,001). Conclusion The results demonstrate that MPs can be accurately measured with radiographic techniques when using calibration markers and a software calibration tool, thus minimizing the source of error and improving the quality of correction.

Accuracy of the hexapod external fixator in treating tibial angular deformities with or without limb length discrepancy: a retrospective study

“…The accuracy of TSF depends on mounting parameters which identify the exact location of the frame in relation to the deformity [29]. If there is an error in the mounting parameters, it results in residual translation-angulation deformity requiring subsequent correction [9,30]. To deal with this, various postoperative radiograph and intraoperative fluoroscopy techniques have been proposed [9,29,[31][32][33][34].…”

“…If there is an error in the mounting parameters, it results in residual translation-angulation deformity requiring subsequent correction [9,30]. To deal with this, various postoperative radiograph and intraoperative fluoroscopy techniques have been proposed [9,29,[31][32][33][34]. However, SCF's radiographic navigation system automatically reproduces the clinical scenario to a virtual scenario without using mounting parameters.…”

Staged correction trajectory with hexapod external fixator for the satisfactory reduction of acute long bone shaft fracture

“…Liu et al 27 precisely measured the deformity and mounting parameters with the help of the elliptic registration technique and three-dimensional reconstruction. Gessmann et al 30 declared that the mounting parameters can be accurately measured with radiographic techniques when using calibration markers and a software calibration tool.…”

Correction of severe lower extremity deformity with digital hexapod external fixator based on CT data

“…The measurement of each parameter produces errors that can affect the final orthopedic result. Moreover, the post-TSF adjustments depend on the precise anteroposterior and lateral radiographic measurements to produce the most accurate output [ 13 , 14 ]. Hence, these X-rays must be taken in a plane orthogonal to the reference ring.…”