Comparison of fluoroscopic and imageless registration in surgical navigation of the acetabular component

Figures & data

Figure 1. Simulation of the operating room setting with placement of the cadaveric pelvis in the lateral decubitus position for fluoroscopic image acquisition.

Figure 2. Cadaveric pelvis placed supine for imageless referencing of the pubic tubercle. Note the cup inserter placed for measuring cup position.

Table I.  Measurement precision and variability. (Cp benchmark > 1.3; Cpk benchmark > 2.0)

Measurement system	Assessment methodology	Inclination (SD; Range)	Anteversion (SD; Range)	Reference points	Cp	Cpk
Coordinate measuring machine	Benchmark precision	46.02°	15.79°	ASISs, symphysis	Inc: 3.06	–
		(1.075; 43.32–46.84°)	(0.411;15.07–16.38°)		Ante: 8.13
CT	Benchmark precision	42.2°(0.65) pubic tubercles	12.1°(0.14) pubic tubercles	ASISs, tubercles	Inc: 5.12	–
					Ante: 23.8
		41.8(0.69) pubic symphysis	14.3°(0.89) pubic symphysis	Symphysis	Inc: 4.8
					Ante: 3.74
Fluoroscopic referencing	Repeatability precision	42.8°	17.5°	ASISs, symphysis	Inc: 2.2	Inc: 4.8
		(1.5; 39.5–44.5°)	(3.0; 14.5–22.5°)		Ante: 1.1*	Ante: 1.0*
Imageless referencing	Repeatability precision	42.3°	11.2°	ASISs, tubercles	Inc: 8.3	Inc: 69.7
		(0.4; 41.5–42.6°)	(0.8; 10.1–12.4°)		Ante: 4.1	Ante: 17.3
Fluoroscopic referencing	Reproducibility precision	48.5°	17.8°	ASISs, symphysis	Inc: 3.7	Inc: 7.5
		(0.9; 46–50°)	(2.5; 13.5–23.5°)		Ante: 1.33	Ante: 1.5*
Imageless referencing	Reproducibility precision	41.8°	15.2°	ASISs, tubercles	Inc: 4.2	Inc: 17.0
		(0.8; 40.1–43.2°)	(1.06; 13.6–16.8°)		Ante: 3.2	Ante: 7.7

Figure 3. Position of the more anterior pubic tubercle (A) compared to the pubic symphysis (B).

Figure 4. Anatomical reference planes of the pelvis used to calculate anteversion and abduction. [Color version available online.]

Table II.  Reported precision of reproducibility of different navigation systems using Process Capability Analysis. (Upper and lower specification limits: ±10°)

Reference	Modality	Object	N	Control measurement	Inclination (°)	Anterversion (°)	Cp inclination	Cp anteversion
Grützner et al.	Fluoroscopy, digitizing	Patients	50	CT measurement	1.5 (SD: 1.1)	2.4 (SD: 1.4)	2.22	1.38
Nogler et al.	Imageless	Cadaver	12	Digitizing arm	−3.86 (SD: 3.4)	−4.89 (SD: 4.55)	0.98*	0.36*
Tannast et al.	Fluoroscopy	Cadaver	14	CT measurement	0.7 (SD: 2.8)	−6.6 (SD: 6.0)	1.19*	0.55*
Jolles et al.	CT	Plastic bones	50	Electromagnetic digitizing	Mean SD: 2.5	Mean SD: 1.5	1.33	2.2
Present study	Fluoroscopy	Cadaver	24	CT; CMM	0.6 (SD: 0.9)	3.2 (SD: 2.5)	3.7	1.3*
Present study	Imageless	Cadaver	24	CT; CMM	−0.6 (SD: 0.4)	3.1 (SD: 0.8)	8.3	4.1

*Denotes below acceptable limits for process capability (= greater than 1.3)