Abstract
To determine accuracy of patient-specific instrumentation (PSI), the preoperative
three-dimensional (3D) plan should be superimposed on the postoperative 3D image to
compare prosthetic alignment. We aimed to compare prosthetic alignment on a preoperative
3D computed tomography (CT) plan and postoperative 3D-CT image, and evaluate the accuracy
of PSI during total knee arthroplasty (TKA). Thirty consecutive knees (30 patients)
who underwent TKA using PSI were retrospectively evaluated. The preoperative plan
was prepared using 3D CT acquisitions of the hip, knee, and ankle joints. The postoperative
3D CT image obtained 1 week after surgery was superimposed onto the preoperative 3D
plan using computer software. Differences in prosthetic alignment between the preoperative
and postoperative images were measured using six parameters: coronal, sagittal, and
axial alignments of femoral and tibial prostheses. Differences in prosthetic alignment
greater than 3 degrees were considered outliers. Two observers performed all measurements.
All parameters were repeatedly measured over a 4-week interval. This measurement method's
intraobserver and interobserver reliabilities were more than 0.81 (very good). For
the femoral and tibial prostheses, absolute differences between the preoperative and
postoperative 3D CT images were significantly larger in the sagittal than in the coronal
and axial planes (p < 0.001). The outlier rate for the sagittal alignment of femoral and tibial prostheses
was significantly higher than that for the alignment of coronal and axial planes (p < 0.001). However, there were no significant differences in the range of motion (ROM)
before and after TKA when comparing cases with and without outliers in the sagittal
plane. Even though the present study did not reveal any issues with the ROM that depended
on the presence of an outlier, accurate verification of prosthetic alignment for individual
PSI models may be necessary because the designs, referenced images, and accuracy are
different in each model.
Keywords
total knee arthroplasty - patient specific instrumentation - three-dimensional evaluation
- computed tomography
