Evaluation of a novel tool for bone graft delivery in minimally invasive transforaminal lumbar interbody fusion

Figures & data

Figure 1 Standard bone graft delivery funnel.

Figure 2 Conventional end-dispensing cannula ejects BG directly in the path of a fusion cage and does not distribute BG into the periphery of the prepared disk space.

Abbreviation: BG, bone graft.

Figure 3 A removable funnel prevents obscuring the view of the tip of the cannula.

Figure 4 View of the cross section of the bone graft delivery tool relative to the conventional cylindrical tool.

Notes: (A and B) The internal cross-sectional area of the round cannula is only 38 mm² and is responsible for substantial wall friction relative to the larger, ovoid cross-sectional area of the prototype.

Figure 5 Close up of the bone graft delivery tool tip and its radiographic appearance.

Notes: (A) A wedged cannula tip allows entrance into the most collapsed disk space. (B and C) The tapered BG delivery tool takes the path of least resistance and is able to enter even the most collapsed, prepared disk space.
Abbreviation: BG, bone graft.

Figure 6 Axial view of the prepared disk space during and after application of the bone graft delivery tool.

Notes: (A) Biportal bone graft delivery tool ejecting bone graft into the prepared area of the disk space. (B) Removal of the BG delivery tool leads to an unobstructed path for a fusion cage.
Abbreviation: BG, bone graft.

Table 1 Details of the study subjects, L4-5 disk space

BG delivered	Disk removed	Cage volume	Ratio	Age	Sex
10.0	2.5	0.76	4.0	46.0	M
12.0	6.0	0.91	2.0	50.0	F
13.0	4.5	1.47	2.9	71.0	M
7.8	1.8	0.56	4.3	64.0	F
12.5	3.0	0.91	4.2	59.0	F
16.5	6.5	1.47	2.5	52.0	M
11.0	7.0	1.05	1.6	47.0	F
10.0	3.0	0.90	3.3	42.0	F
11.0	8.0	1.26	1.4	59.0	F
10.5	2.0	0.91	5.3	65.0	F
8.0	4.0	1.47	2.0	52.0	M
13.5	3.0	0.91	4.5	50.0	F
14.5	1.0	0.69	14.5	43.0	M
15.5	4.0	0.91	3.9	42.0	M
6.0	1.5	1.26	4.0	68.0	M
13.0	4.5	1.47	2.9	54.0	F
14.5	5.0	1.47	2.9	57.0	M
14.5	7.5	1.47	1.9	74.0	M
10.5	7.5	1.67	1.4	59.0	M
8.5	4.0	0.91	2.1	71.0	F
9.0	3.0	0.56	3.0	57.0	F
8.5	3.0	0.91	2.8	86.0	F
7.3	1.3	0.62	5.6	64.00	F
19.0	10.0	1.26	1.9	59.00	F
12.0	2.0	0.76	6.3	65.00	F
12.5	2.0	1.26	6.3	63.00	M
7.0	3.0	1.06	2.3	70.00	M
10.5	7.0	1.47	1.5	79.00	M
8.0	4.0	0.91	2.0	47.00	F
9.0	8.0	0.91	1.1	42.00	F
8.5	4.5	1.47	1.9	29.00	M
7.5	3.0	1.06	2.5	72.00	M
14.5	7.0	1.98	2.1	69.00	M
7.5	2.5	1.06	2.5	53.00	M
9.0	4.0	1.26	2.1	58.00	M
6.0	5.0	0.91	1.2	35.00	F
7.0	5.0	0.91	1.4	58.00	F
9.0	5.0	1.26	1.8	40.00	F
7.0	1.5	0.91	4.7	83.00	F
9.0	4.0	1.26	2.3	58.00	M
8.0	3.5	0.91	2.3	41.00	F
9.5	3.2	0.76	3.0	60.00	F
10.0	4.0	0.91	2.5	40.00	F
13.5	9.0	1.67	1.5	64.00
8.5	5.0	1.26	1.6	61.00	F
7.5	3.5	0.91	2.1	80.00	F
6.5	1.0	0.56	6.5	85.00	F
6.5	1.5	1.26	4.3	54.00	F
5.5	3.0	0.76	1.8	36.00	F
9.5	6.0	1.74	1.6	54.00	M
7.0	5.0	1.26	1.4	50.00	F
11.5	3.5	1.26	3.3	57.00	M
10.5	7.2	1.67	1.5	58.00	M
6.0	2.0	0.91	3.0	57.00	F
4.5	1.0	1.26	4.5	51.00	F
5.5	1.0	0.96	5.5	64.00	M
7.0	4.0	1.26	1.8	59.00	F
10.0	3.2	1.50	3.1	66.00	M

Notes: Average BG delivered: 9.8±3.3 mL. Average disk material removed: 4.1±2.2 mL. Ratio (BG delivered/disk material removed): 3.1±2.0.

Abbreviations: BG, bone graft; F, female; M, male.

Table 2 Details of the study subjects, L5-S1 disk space

BG delivered	Disk removed	Cage volume	Ratio	Age	Sex
10.0	1.0	0.45	10.45	62.00	F
7.3	1.3	0.62	6.05	64.00	F
14.0	5.0	0.90	2.98	42.00	F
19.0	10.0	1.26	2.03	47.00	F
9.5	3.0	0.76	3.75	52.00	F
6.0	1.0	0.76	6.76	46.00	M
12.0	2.0	0.76	6.38	65.00	F
11.0	3.0	1.26	4.09	52.00	M
7.0	1.0	0.62	7.62	50.00	F
5.0	1.0	0.62	5.62	43.00	M
7.5	3.5	0.91	2.42	42.00	F
11.0	2.0	1.06	6.03	68.00	M
12.5	2.0	1.26	6.88	63.00	M
8.0	4.0	0.91	2.23	71.00	F
7.5	1.0	0.56	8.10	59.00	M
9.5	5.0	0.91	2.10	47.00	F
6.5	2.0	0.91	3.71	56.00	F
8.0	4.5	1.26	2.06	29.00	M
9.0	4.5	1.50	1.50	53.00	M
7.0	3.0	0.91	2.63	35.00	F
5.5	2.0	0.76	3.13	40.00	F
8.0	2.0	1.06	4.53	58.00	M
8.5	5.2	0.91	1.81	41.00	F
6.0	2.0	0.45	3.23	40.00	F
9.5	1.0	1.06	10.10	54.00	F
5.0	1.0	0.76	5.76	58.00	M
6.0	3.5	1.26	2.07	57.00	M
8.5	2.5	1.06	3.82	57.00	F
6.0	1.0	1.16	7.00	51.00	F
8.5	1.0	0.96	9.40	64.00	M
10.0	4.4	1.67	2.65	55.00	M
6.0	1.0	1.06	7.01	59.00	F
9.0	3.0	0.76	3.25	36.00	F
9.0	4.5	0.97	2.22	18.00	M

Notes: Average BG delivered: 8.6±3.1 mL. Average disk material removed: 2.8±1.9 mL. Ratio (BG delivered/disk material removed): 4.2±2.4.

Abbreviations: BG, bone graft; F, female; M, male.

Figure 7 Volumetric measurement of disk material removed and bone graft to be delivered.

Notes: (A) Syringe filled with disk. (B) Bone graft slurry material and compressed for volume measure.
Abbreviation: BG, bone graft.

Figure 8 BG delivered versus disk material removed from the L4-S1 disk spaces.

Abbreviations: BG, bone graft; DMR, disk material removed.

Figure 9 Relationship of BG delivered as a function of DMR.

Abbreviations: BG, bone graft; DMR, disk material removed; T-LIF, transforaminal lumbar interbody fusion.

Figure 10 CT scan of the L5-S1 disk space showing complete filling of the prepared disk space and successful fusion and incorporation of bone graft 15 months postfusion.

Abbreviation: CT, computed tomography.

Figure 11 Geometric explanation for increased volume in a prepared, distracted disk space.