Doxycycline-coated sutures improve the suture-holding capacity of the rat Achilles tendon

Figures & data

Figure 1. Using the Kessler technique, the suture was inserted only into the distal part of the cut Achilles tendon to specifically evaluate suture holding capacity. A free loop was left for attachment during mechanical testing.

Table 1.  Systemic treatment with doxycycline. Force (N) at suture pull-out and energy uptake (Nmm) 3, 5, and 7 days after tendon suture. One 3 day-group was operated on at a separate occasion (a). The p-values refer to two-way ANOVA for the effect of treatment (b) and time (c).

Day	Control		Doxycycline		Difference		P-value
	mean (SD)	n	mean (SD)	n	mean	(95% CI)
Force at suture pull-out (N)
3^a	12.6 (3.6)	9	15.0 (4.3)	9	2.4	(−1.3 to 6.0)
3	14.8 (2.0)	9	17.6 (4.1)	8	2.8	(−0.4 to 5.9)	0.08 ^b, 0.1 ^c
5	16.7 (4.2)	9	14.8 (4.0)	9	−1.9	(−5.6 to 1.9)
7	15.4 (3.8)	9	18.6 (4.2)	8	3.2	(−0.6 to 7.0)
Energy uptake (Nmm)
3^a	59.5 (19)	9	88.0 (36)	9	29	(2.0 to 55)
3	85.3 (17)	9	105.4 (21)	8	20	(1.7 to 38)	0.04^b, 0.06 ^c
5	98.8 (30)	9	80.7 (24)	9	−18	(−43 to 6.8)
7	85.6 (23)	9	123.0 (70)	8	37	(−13 to 88)

Table 2.  Local doxycycline treatment using drug-coated sutures. Force (N) at suture pull-out and energy uptake (Nmm) 3 days after tendon suture. The p-values refer to the effect of treatment in a two-way ANOVA where the other factor was experiment 1 vs. experiment 2. The results were not significantly different between the two experiments. Controls were uncoated in experiment 1 and carrier (fibrinogen)-coated in experiment 2

Experiment	Control	n	Doxycycline	n	Difference		P-value
	mean (SD)	n	mean (SD)	n	mean	(95% CI)
Force at suture pull-out (N)
1	14 (3.7)	15	16 (2.4)	15	2.1	(−1.3 to 5.5)	0.02
2	15 (2.8)	21	16 (3.2)	23	1.3	(−1.4 to 3.9)
Energy uptake (Nmm)
1	76 (23)	15	86 (14)	15	9	(−11 to 30)	0.01
2	82 (19)	21	99 (25)	23	17	(−2 to 36)

Figure 2. In vitro drug release from the suture surface. The percentage released was calculated from the expected total amount of doxycycline on the thread, based on measurements using silicon surfaces. After 24 and 72 h, 73% and 96% of doxycycline had been released from the surface of the suture.