A novel implantable device for a minimally invasive surgical treatment of obstructive sleep apnea: design and preclinical safety assessment

Figures & data

Figure 1 Schematic of the implant and delivery system.

Notes: The implant pictured has single-hole loop attachment points (A). The deployed implant is depicted in the tongue base (B) and soft palate (C), with the implant tool in situ for visualization of the delivery method).
Abbreviation: PLG, polylactide-co-glycolide.

Figure 2 FEA model of the palate and tongue (A) and single-tongue implant (B).

Abbreviation: FEA, finite element analysis.

Figure 3 685207-F1 pre- and postfatigue testing static conditioning test

Note: The dynamic modulus of the implant was not affected by 5,260,000 stretch cycles; values before (red) and after (blue) stretching were virtually identical.

Figure 4 Exemplar histological samples: inflammatory response at the attachment points and middle of the linear component of the implants of sheep at 30 days and 60 days.

Notes: (A) Fibrous tissue fills the center hole of this device (center of image), bridging between muscle at the top and bottom of image. The two circular voids represent each side of the attachment point loop at 30 days. (B) This micrograph shows the typical 30-day reaction with the fast-eroding PLG; note that a residual PLG layer of ~0.5 mm surrounds the device (void in center of image). There is mild accompanying foreign body-type inflammation directed at the PLG material, with a further encircling thin band of fibrous connective tissue. (C) There is mature fibrous tissue spanning the attachment opening and minimal inflammation at 60 days postimplantation. (D) There is a very thin circular layer of bland fibrous tissue encapsulating the contractile element at 60 days. No residual PLG is present and inflammation is insignificant.
Abbreviation: PLG, polylactide-co-glycolide.

Table 1 Single-hole silicone loop and paddle-shaped implant ends resulted in the best fibrous tissue attachment in lumbar muscle tissue in the ovine model

Days	Attachment point evaluation				Erodible element evaluation
	Attachment element configuration tested	Number of implants tested	Fibrous tissue anchoring of attachment point	Inflammatory response at attachment point	PLG erodible element tested	Number of implants tested	Degree of hydrolysis and bioabsorption of erodible element	Contraction of implant and creation of tensile force	Inflammatory response at middle of implant
30	Single-hole silicone loop	5	Excellent	Minor low grade/mild	Fast eroding	12	Significant	Significant	Negligible/localized mild
	Multiple-hole silicone	4	Variable, inconsistent	Minor low grade/mild
	Polyester cylindrical	4	Variable, inconsistent	Low grade	Slow eroding	2	Minimal	Absent	Minimal
	Paddle shaped	2	Excellent	Minimal
60	Single-hole silicone loop	4	Excellent	Low grade	Fast eroding	12	Complete	Significant	Negligible/localized mild
	Multiple-hole silicone	3	Variable, inconsistent	Moderate localized
	Polyester cylindrical	6	Variable, inconsistent	Low grade	Slow eroding	2	Minimal	Absent	Minimal
	Paddle shaped	2	Excellent	Minimal
180	Single-hole silicone loop	16	Excellent	Minor localized	–	–	–	–	–

Notes: Fast-eroding PLG was fully resorbed within 60 days, allowing contraction of the implant and creation of tensile forces in the target tissues. There was little inflammatory response to the implant.

Abbreviation: PLG, polylactide-co-glycolide.

Table 2 For both tongue and soft palate implants in the canine model, there was little inflammatory response for either silicone durometer tested

Days	Site	Number of implants	PLG erosion rate	Silicone hardness (durometer)	Inflammation (ends)	Inflammation (middle)	Erosion
100a	Tongue	1a	Medium	Low	0	2	2
100a	Tongue	1a	Medium	High	0	2	3
100	Tongue	1	Medium	Low	–	–	3
100	Tongue	1	Medium	High	2.5	2	3
100	Palate	1	Medium	Low	1.5	2	3
100	Palate	1	Medium	High	1.5	2	3
180a	Tongue	2a	Medium	Low	0.25	0.5	1
180	Tongue	2	Medium	High	1 1	0
180	Tongue	3	Slow	Low	2.2	1.67	0.67
180	Tongue	1	Slow	High	–	2	2
180	Palate	2	Fast	Low	1	1	0
180	Palate	2	Slow	Low	1	1	3
180	Palate	2	Medium	Low	1	1.5	1.5
180	Palate	2	Medium	High	1.75	2	1
365	Tongue	2	Slow	Low	1.5	0.5	0
365	Tongue	2	Fast	Low	0.75	0	0
365	Palate	2	Slow	Low	1.25	1.5	0
365	Palate	2	Fast	Low	0	0	0

Notes: All PLG materials were fully resorbed by 365 days postimplant.

a Histological analysis was completed on the implantation sites from which the implant had been removed at least 6 weeks prior. The – indicates samples with abscesses that were excluded from the data set for the purposes of statistical evaluation to remove bias from infection at the implant site, as the abscess was considered to be secondary to infection at the site and not a true reflection of the tissue response in the uncomplicated state. Inflammation was graded on a scale of 1–5 (1= minimal and 5= overt abscess formation), and resorption of the PLG erodible element was graded on a scale of 0–4 (0= none or negligible material persistent in tissue [completely resorbed] and 4= material persistent in tissue largely intact [nonresorbed]).

Abbreviation: PLG, polylactide-co-glycolide.