New developments in bone-conduction hearing implants: a review

Figures & data

Figure 1 Categorization of bone-conduction devices.

Abbreviations: BAHA, bone-anchored hearing aid; BCI, bone-conduction implant.

Figure 2 Conventional skin-drive bone-conduction devices, attached with (A) a steel spring headband, and (B) with frames for glasses.

Note: Images provided courtesy of (A) Starkey Hearing Technologies, (B) bruckhoff hannover gmbh.

Figure 3 Sophono^®, a passive transcutaneous skin-drive bone-conduction device.

Note: Image provided courtesy of Sophono^®.

Table 1 Summary of audiometric data of implantable bone conduction devices in clinical studies, only including studies that are reasonably comparable

Model	Type	No of subjects	PTAbc [dB HL]	Ages [years]	Etiology	Aided vs unaided sound field improvement			Reference
						PTA4 [dB HL]	SRT [dB HL]	SRS [%]
Bonebridge	Active trans	12	5–35	19–69	Cond, mixed	25	N/A	78,8	Sprinzl et al^Citation59
		4	24–36	45–63	Cond, mixed	36,5	36,25	N/A	Barbara et al^Citation60
		6	Average 26	40–57	Cond, mixed	34,9*	N/A	80,0*	Ihler et al^Citation62
		23	5–60	6–80	Cond, mixed, SSD	29‡	N/A	49	Riss et al^Citation63
BCI	Active trans	6	0–30	18–67	Cond, mixed	31,0	27,0	51,2†	Reinfeldt et al^Citation50
Sophono	Passive trans	20 of >100	Average 11	6–50	Cond	28,6	N/A	61,6	Siegert and Kanderske^Citation27
		6	0–11	5–11	Cond	22*	28*	61*	Hol et al^Citation28
		10	18–36	16–67	Cond, mixed	29,7*	34,1*	84,1*	Magliulo et al^Citation31
Baha Attract	Passive trans	9 of 12	3–26	5–65	Cond	19	19	N/A	Işeri et al^Citation33
BAHA HC 200	Per	110–122	−1–45	Average 54	Cond, mixed	29,4	26,5	41,6†	Tjellström and Håkansson^Citation35

Notes:

* Unaided measured with headphones

† SRS was measured with competing noise, signal-to-noise ratio =4 dB

‡ average of 0.5, 1, 2, 3, 4, and 6 kHz.

Abbreviations: BAHA, bone-anchored hearing aid; BCI, bone-conduction implant; cond, conductive; HL, hearing level; N/A, not applicable; per, percutaneous; PTA₄, four-frequency averages of pure-tone audiometry; PTAbc, pure-tone average for bone-conduction; SRS, speech-recognition score; SRT, speech-recognition thresholds; SSD, single-sided deafness; trans, transcutaneous.

Figure 4 Baha^® Attract, a passive transcutaneous skin-drive bone-conduction device.

Note: Image provided courtesy of Cochlear Bone Anchored Solutions AB.

Figure 5 Bone-anchored hearing aid, a percutaneous direct-drive bone-conduction device.

Notes: (A) Ponto (Oticon Medical, Askim, Sweden); and (B) Baha^® BP100 (Cochlear Bone Anchored Solutions AB, Mölnlycke, Sweden). Images provided courtesy of Oticon Medical (A) and Cochlear Bone Anchored Solutions AB (B).

Figure 6 Bone-conduction implant, an active transcutaneous direct-drive bone-conduction device.

Figure 7 Bonebridge™, an active transcutaneous direct-drive bone-conduction device.

Note: Image provided courtesy of MED-EL.

Figure 8 SoundBite™, an in-the-mouth bone-conduction device with implant for tooth attachment and behind-the-ear sound processor.

Note: Image provided courtesy of Sonitus Medical.

Table 2 MPO and reference thresholds for implantable BCDs

Device	MPO in force level [dB re 1μN]					Comment/reference
	0.5 k	1 k	2 k	4 k	PTA4
1. Bonebridge MPO @ Skullsimulator	93	104	102*	84	95.8	Håkansson B, personal communication, 2014
2. BCI MPO @ Skullsimulator	97	102	94*	95	97.0	Taghavi et al, unpublished data, 2014
3. RETFL DBC @ pos A (BAHA)	48	45.5	26	27.5	36.8	Carlsson and Håkansson^Citation79
4. Correction: Pos A (BAHA) vs pos B (BCI) [dB]	3	9	10	8	7.5	Reinfeldt et al^Citation50
5. RETFL DBC @ pos B (BCI)	45	36.5	16	19.5	29.3	Calculated (3 minus 4)

Notes: Pos A refers to the approximate skull position for a BAHA, 55 mm behind and slightly above the ear-canal opening. Pos B is the skull position for the BCI, 10–15 mm behind the ear-canal opening. Correction (4) is the calculation of the sensitivity difference between stimulation of the BCI and the BAHA positions (pos B and pos A, respectively). @, attached to.

* Values were taken slightly below 2 kHz to avoid interference with a resonance peak.

Abbreviations: BAHA, bone-anchored hearing aid; BCI, bone-conduction implant; BCD, bone-conduction device; DBC, direct bone conduction; MPO, maximum power output; pos A, position A; pos B, position B; PTA₄, four-frequency pure-tone average; re, relative to; RETFL, reference equivalent threshold force level.

Table 3 Maximum dynamic ranges and suggested BC thresholds for implantable BC devices

Device	Max dynamic range with normal cochlear function [dB HL]					Comment/reference	Max PTAbc at aided PTA =30–35 dB HL
	0.5 k	1 k	2 k	4 k	PTA4
Bonebridge Alt 1	48	68	86	65	67	Calculated*	32–37
Bonebridge Alt 2	55	61	71	60	62	Mertens et al^Citation73	27–32
BCI	52	66	78	76	68	Calculated**	33–38
Sophono @ Skullsimulator	51	53	64	50	54	Zwartenkot^Citation70	19–24
Baha Divino @ Skullsimulator	64	68	75	68	69	Zwartenkot^Citation70	34–39
Baha Cordelle @ Skullsimulator	80	75	87	81	81	Zwartenkot^Citation70	46–51

Notes: Dynamic range is calculated from Table 2 and from published MPO dB HL data. Indication range in PTA₄ BC, assuming aided PTA₄ of 30–35 dB HL, is calculated as the dynamic range minus 30–35 dB.

* Row 1 minus row 5 in Table 2;

** row 2 minus row 5 in Table 2. @, attached to.

Abbreviations: Alt, alternative; BC, bone-conduction; BCI, bone-conduction implant; HL, hearing level; max, maximum; MPO, maximum power output; PTA, pure-tone average; PTA₄, four-frequency pure-tone average; PTAbc, pure-tone average for bone-conduction.

Figure 9 Estimated maximum recommended preoperative bone-conduction thresholds, which include a “gray” zone depending on if an aided PTA of at least 30 or 35 dB HL is met.

Abbreviations: BCI, bone-conduction implant; HL, hearing level; max, maximum; preop, preoperative; PTA, pure-tone average; PTA₄, four-frequency averages of PTA; PTAbc, pure-tone average for bone-conduction.

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