Accuracy of a Three-Dimensional (3D)-Printed Patient-Specific (PS) Femoral Osteotomy Guide: A Computed Tomography (CT) Study

Abstract

Femoral neck osteotomy creates a critical anatomical landmark for surgeons performing primary Total Hip Arthroplasty (THA); it affects the final height and position of the femoral component. Patient Specific Instrumentation (PSI) has been developed to guide the osteotomy. We aimed to assess the accuracy of a patient-specific (PS) femoral osteotomy guide in primary THA using three-dimensional (3D) computed tomography (CT) analysis. We included pre- and post-operative CT data of 103 THAs. All patients underwent 3D planning to define the optimal femoral neck osteotomy level. Our primary objective was to quantify the discrepancy between the achieved and planned osteotomy level; our secondary objective was to evaluate the clinical outcome. The median (Interquartile Range—IQR) discrepancy between the achieved and planned osteotomy level was 0.3 mm (−1 mm to 2 mm). We found a strong positive correlation between the planned and achieved osteotomy level (R2 = 0.9, p < 0.001). A satisfactory clinical outcome was recorded. Our findings suggest that surgeons can use 3D-printed PS guides to achieve a femoral neck osteotomy with a high level of accuracy to the plan.

Keywords: 3D-printed patient-specific guides; femoral neck osteotomy; total hip arthroplasty.

Figure 1

Study design.

Figure 2

(a) Schematic illustration of the surgical plan; (b) Illustration of the 3D-printed Patient-Specific (PS) femoral osteotomy guide; (c) Two pins secure its position and the surgeon cuts the femoral neck using the saw blade. The femoral head–neck junction is then removed with the guide attached.

Figure 3

Schematic illustration of the point adopted for evaluation. (a) The middle depth marking of the femoral stem, (b) was translated to the posterior cortex of the proximal femur on the osteotomy plane.

Figure 4

(a) The surgical plan in red colour is registered to the post-operative CT scan (model in white colour); (b) The relative vertical discrepancy between the achieved and planned osteotomy planes is quantified (light blue arrow).

Figure 5

Box plot illustrating the measurements of the planned and achieved osteotomy levels.

Figure 6

A linear regression analysis plot illustrating achieved osteotomy level as a function of the surgical plan.

Figure 7

Bland–Altman plot of the comparison between the planned and achieved osteotomy level. The dashed red lines represent the Upper and Lower Limits of Agreements (ULA and LLA). These were 4.8 mm and −3.8 mm, respectively.

Figure 8

Histogram depicting the distribution of the vertical osteotomy discrepancy in 103 primary THAs.