Application of bonebed-malleus short process registration in minimally invasive cochlear implantation

Figures & data

Figure 1. (a) Titanium screws and bone hole in bone surface; (b) Shallow and deep fiducial markers for the measurement of registration resolution.

Figure 2. (a, b) Point clouds collected at the bone-bed in real space; (c) Point clouds collected at the transplant bone-bed in the virtual space; (d, e) Point clouds collected at the malleus short process using an otoendoscope. (f) Point clouds collected at the malleus short process of the ossicles using the collecting sphere in the virtual space.

Table 1. TRE of the various registration methods.

	Registration method
Target	A^a	B^b	F	P
Shallow target
Screw 1	0.50 ± 0.21	0.47 ± 0.23	1.469	0.235
Screw 2	0.50 ± 0.17	0.43 ± 0.17
Screw 3	0.58 ± 0.15	0.52 ± 0.23
Screw 4	0.60 ± 0.21	0.54 ± 0.24
Deep target
Retrofacilis titanium screw	0.90 ± 0.41	0.74 ± 0.27	5.078	0.038
Titanium at semicircular canal	0.95 ± 0.37	0.86 ± 0.34
Prill in the round window niche	1.16 ± 0.46	0.90 ± 0.27

^a Joint registration of bone bed-malleus short process.

^b Registration by titanium screw.

Measurement errors are expressed as mean ± standard deviation (mm), sample size n = 10.

Table 2. Comparison of results before and after drilling (n = 8).

No.	Deviation from target point (mm)	Deviation from entry point (mm)	Distance between planned and actual trajectory (mm)	Angle between planned and actual trajectory (°)	Trajectory length
1	0.30	0.46	0.07	1.40	30.21
2	1.08	1.45	0.45	1.29	26.97
3	0.84	0.27	0.15	2.38	25.36
4	1.29	1.41	1.12	3.29	26.16
5	0.97	0.31	0.06	2.49	29.35
6	0.88	0.81	0.80	1.10	27.78
7	0.68	0.41	0.21	2.08	27.60
8	0.66	0.16	0.15	1.15	29.08
Mean	0.84	0.66	0.38	1.90	27.81
Std. deviation	0.30	0.51	0.39	0.79	1.66

Table 3. Distance from the actual trajectory to important structural elements (n = 8).

No.	Trajectory to the facial nerve (mm)	Trajectory to chorda tympani (mm)	Trajectory to the external auditory canal wall (mm)	Ossicle injury
1	1.0	0.0	2.6	no
2	0.7	/	2.2	no
3	0.4	0.9	2.0	no
4	0.2	0.5	1.7	no
5	0.9	/	1.5	no
6	0.8	/	1.0	no
7	0.0	0.0	1.3	no
8	0.5	/	1.3	no
Mean	0.6		1.7
Std. deviation	0.4		1.6