Use of ¹⁸F-fluoride PET to determine the appropriate tissue sampling region for improved sensitivity of tissue examinations in cases of suspected periprosthetic infection after total hip arthroplasty

Figures & data

Figure 1. Definitions used for the ¹⁸F-fluoride PET uptake patterns on the acetabular and femoral sides. A. Major-uptake region on the acetabular side: ¹⁸F-fluoride uptake has spread to more than 50% of the acetabular component with an SUV_max of > 5. B. Minor-uptake region on the acetabular side: ¹⁸F-fluoride uptake has localized in less than 50% of the acetabular component with an SUV_max of > 5. C. Major-uptake region on the femoral side: ¹⁸F-fluoride uptake has spread to more than 50% of the femoral component with an SUV_max of > 5. D. Minor-uptake region on the femoral side: ¹⁸F-fluoride uptake has localized in less than 50% of the femoral component with an SUV_max of > 5.

Table 1. Results of PET, histopathological examination, microbiological culture, and real-time PCR in the revision group

			^18F–fluoride PET		Postoperative diagnosis from intraoperative specimens
A	B	C	D	E	F	G	H	I
1	75	F	5.1 / 6.7	Major / Major	+ / –	+ / +	+ / +	Staphylococcus hominis–hominis (MRS)
2	73	F	5.1 / 3.1	Major / –	+ / –	– / –	+ / +	Negative
3	65	M	9.1 / 2.5	Major / –	+ / –	+ / –	+ / –	MRSE
4	73	F	8.6 / 4.9	Major / –	+ / –	+ / –	+ / +	MRSE
5	65	M	5.6 / 13	Minor / Major	– / N/A	– / –	– / +	Negative
6	63	F	7.7 / 10	Minor / Major	– / +	– / –	+ / +	Streptococcus agalactiae
7	75	M	11 / 12	Major / Major	+ / +	+ / +	+ / +	Staphylococcus auricularis (MRS)
8	77	F	17 / 3.5	Major / –	+ / –	– / –	+ / –	Negative
9	65	M	6.8 / 9.8	Minor / Major	– / –	– / –	– / +	Negative
10	71	F	10 / 11	Major / Major	– / +	– / –	– / +	Negative
11	70	M	12 / 10	Major / Major	+ / +	+ / +	+ / +	Non–hemolytic streptococcus
12	56	F	9.8 / 6.1	Major / Minor	+ / –	– / –	N/A / N/A	Negative
13	89	M	5.8 / 6.8	Major / Major	+ / +	+ / +	+ / +	Streptococcus sanguinis
14	70	F	14 / 2.3	Major / –	– / –	+ / –	+ / –	Staphylococcus warneri
15	82	F	9.0/13	Major / Major	– / +	+ / –	+ / +	Aerobic Gram–positive bacillus
16	83	F	15 / 11	Major / Minor	+ / –	– / –	+ / –	Negative
17	69	F	6.8 / 14	Major / Major	+ / +	+ / +	+ / +	MRSE
18	78	M	5.2 / 2.3	Minor / –	– / –	– / –	– / –	Negative
19	69	F	6.8 / 2.3	Minor / –	– / –	– / –	– / –	Negative
20	59	M	2.8 / 9.0	– / Minor	– / –	– / –	– / –	Negative
21	83	M	1.7 / 6.2	– / Minor	– / –	– / –	– / –	Negative
22	83	F	9.9 / 4.5	Minor / –	– / –	– / –	– / –	Negative
23	73	M	7.4 / 3.3	Minor / –	– / –	– / –	– / –	Negative

N/A: not available.

A Case

B Age

C Sex

D SUV _max (acetabular/femoral)

E Uptake pattern (acetabular/femoral)

F Histopathological examination (acetabular/femoral)

G Microbiological culture (acetabular/femoral)

H Real-time PCR (acetabular/femoral)

I Bacterial strain

Table 2. The sensitivity of histopathological examination, microbiological culture, and real-time PCR—individually and in combination—in analyzing the ¹⁸F-fluoride major-, minor- and no-uptake sides in the revision group

	On major-uptake side (24 sides)	On minor-uptake side (11 sides)	On no-uptake side (11 sides)
Histopathological examination
Positive	18	0	0
Negative	5	11	11
Side not available	1	–	–
Sensitivity	0.78	0	0
Microbiological culture
Positive	14	0	0
Negative	10	11	11
Sensitivity	0.58	0	0
Real-time PCR
Positive	22	1	2
Negative	1	9	9
Side not available	1	1	–
Sensitivity	0.96	0.1	0.18
Combined
Positive	23	1	2
Negative	1	10	9
Sensitivity	0.96	0.1	0.18

Figure 2. A. Patient no. 5 (revision group) with a radiolucent line around the femoral implant. B. ¹⁸F-fluoride PET image showing minor uptake with an SUV_max of 5.6 on the acetabular side and major uptake with an SUV_max of 13 on the femoral side. In this patient, real-time PCR was positive only for tissues sampled from the femoral side, suggesting the existence of localized infection around the femoral component.

Figure 3. A. Patient no. 8 (revision group) with severe loosening of the cup side. B. ¹⁸F-fluoride PET image. Massive ¹⁸F-fluoride uptake on the acetabular side suggested that the focal point of inflammation was localized around the acetabular component. The SUV_max was 17 on the acetabular side (white arrow) and 3.5 on the femoral side, indicating major uptake only on the acetabular side. C. Histopathological examination indicated infection with a minimum of 5 HPF (×400) containing 10 or more neutrophils. In this patient, the histopathological examination and real-time PCR results were both positive only for tissues sampled from the acetabular side, suggesting the existence of localized infection on the membrane around the acetabular component.

Figure 4. A. Patient no. 22 (revision group) with a horizontally-moved acetabular implant. B. ¹⁸F-fluoride PET axial image showing a minor-uptake region with an SUV_max of 9.9 on the acetabular side. C. ¹⁸F-fluoride PET coronal image showing a minor-uptake region on the acetabular side and a no-uptake region with an SUV_max of 4.5 on the femoral side. This patient was diagnosed as having aseptic loosening, as no positive results were obtained in any of the tissue examinations