Visual Pattern and Serial Quantitation of 18F-Sodium Fluoride PET/CT in Asymptomatic Patients After Hip and Knee Arthroplasty

Abstract

Purpose: We investigated the visual tracer distribution pattern and serial changes in uptake ratio in different anatomical zones during the natural postoperative course in order to establish a reference for evaluation of patients with complications.

Methods: A total of 36 patients without symptoms after hip or knee arthroplasty were grouped according to the interval between surgery and the scan. The serial changes in SUVmean in each periprosthetic zone were quantified using the volume of interest isocontour method. Images were classified according to the uptake distribution pattern. The uptake ratios in the postoperative period groups were then compared using the Kruskal-Wallis test. The correlation between uptake ratio and postoperative period was then determined.

Results: Tracer distribution patterns in hip prostheses were classified into three types and the patterns in knee prostheses into five types. In hip prostheses, intense osteoblastic activity was observed during 3-6 months and then declined in most patients, but showed a slight increase over 15-25 months in 5-10 % of patients. The correlation coefficients varied among the zones. Significant differences in uptake ratios among the period groups was found for all zones, except zone 8. Porous coated areas showed higher uptake than uncoated areas only for the period the 3-6 months. In knee prostheses, uptake ratios showed a curvilinear pattern, increasing from 3-6 to 8-15 months and declining later. The uptake ratios were different among the period groups. Every zone showed a positive correlation from 3-6 to 8-15 months, and negative correlations from 8-15 to 22-25 months.

Conclusions: This is the first 18F-sodium fluoride PET/CT study investigating the stability of implants and sets a reference for evaluation of patients with complications.

Keywords: Arthroplasty; Positron emission tomography; Postoperative; Prosthesis; Sodium fluoride.

Conflict of interest statement

Compliance with Ethical Standards Conflicts of Interest The authors declare that they don’t have conflicts of interest. Ethical Statement The study was approved by an institutional review board or equivalent and has been performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments. All subjects in the study gave written informed consent or the institutional review board waived the need to obtain informed consent.

Figures

Fig. 1

a Hip prosthesis. Zones 1–3 in the acetabular component correspond to DeLee-Charnley zones. Zones 4–10 in the femoral component correspond to Gruen zones. b Knee prosthesis. Zones 1–3 are located in the femoral component (on the sagittal view) and zones 4–6 are located in the tibial component (on the coronal view)

Fig. 2

a, c, e Three-dimensional cuboid VOI placement for each zone. In the hip prosthesis, the acetabular VOI in zones 1–3 is 25 × 30 × 25 mm, the femoral VOI in zones 5, 6, 8 and 9 is 37 × 37 × 37 mm; in zone 4 is 37 × 37 × 55 mm; and in zones 7 and 10 is 37 × 37 × 20 mm. In the knee prosthesis, the tibial VOI in zones 4 and 6 is 30 × 30 × 30 mm, and in zone 5 is 27 × 27 × 40 mm. b, d, f. The isocontours to place the VOIs around the structures are automatically detected by setting a threshold of 30 % of the difference between the maximum SUV and minimum SUV

Fig. 3

Diagrams and representative PET images showing the three types of uptake pattern in hip prostheses (a type 1, b type 2,. c type 3). Black areas are areas of severely increased uptake and shaded areas are areas of mildly increased uptake

Fig. 4

Diagrams and representative PET images showing the five types of uptake pattern in the femoral component of knee prostheses (a type 1, b type 2,. c type 3, d type 4, e type 5) Black areas represent areas of severely increased uptake and shaded areas represent areas of mildly increased uptake

Fig. 5

Diagrams and representative PET images showing the five types of uptake pattern in the tibial component of knee prostheses (a type 1, b type 2,. c type 3, d type 4, e type 5) Black areas represent areas of severely increased uptake and shaded areas represent areas of mildly increased uptake

Fig. 6

Uptake ratios during the periods 3–6 months (group 1), 7–22 months (group 2), and more than 24 months (group 3) in the ten periprosthetic zones of hip prostheses

Fig. 7

Differences in mean uptake ratios between coated and uncoated areas in the femoral components of hip prostheses (a 3–6 months, b 7–22 months, c more than 24 months)

Fig. 8

Changes in uptake ratios during the natural postoperative course in the ten periprosthetic zones of hip prostheses. Correlation coefficients and p values are also shown. a Zone 1, b Zone 2, c Zone 3, d Zone 4, e Zone 5, f Zone 6, g Zone 7, h Zone 8, i Zone 9, j Zone 10

Fig. 9

Uptake ratios for the periods 3–6 months (period 1), 8–15 months (period 2), 22–25 months (period 3) in the six zones of knee prostheses. a Zone 1, b Zone 2, c Zone 3, d Zone 4, e Zone 5, f Zone 6

Fig. 10

Changes in uptake ratios during the natural postoperative course in the six periprosthetic zones of knee prostheses. The total period is divided into an early period and a delayed period. Correlation coefficients and p values are also shown. a Zone 1, b Zone 2, c Zone 3, d Zone 4, e Zone 5, f Zone 6