In vitro study of the efficacy of acrylic bone cement loaded with supplementary amounts of gentamicin: Effect on mechanical properties, antibiotic release, and biofilm formation

Figures & data

Figure 1. Dimensioned drawing of rectangular cross-sectional fatigue test specimen. Drawing not to scale

Figure 2. Compressive strength (mean ± SD) of unloaded and gentamicin-loaded Palacos R bone cements. ‘a’ denotes a p-value less than 0.001, indicating a statistically significant difference between unloaded bone cement and cements loaded with 1–4 g of gentamicin. ‘b’ denotes a p-value less than 0.001, indicating a statistically significant difference between Palacos R cement with 0.5 g of gentamicin and Palacos R cement loaded with 1–4 g of gentamicin.

Figure 3. Bending strength (mean ± SD) of unloaded and gentamicin-loaded Palacos R bone cements. ‘a’ denotes a p-value less than 0.001, indicating a statistically significant difference between unloaded bone cement and cements loaded with 1–4 g of gentamicin. ‘b’ denotes a p-value less than 0.001, indicating a statistically significant difference between Palacos R cement with 0.5 g of gentamicin and Palacos R cement loaded with 1–4 g of gentamicin.

Figure 4. Fatigue data of unloaded and gentamicin-loaded Palacos R bone cements. (A.) number of cycles to failure (mean ± SD), (B.) Weibull slope, and (C.) fatigue performance. ‘a’ denotes a p-value less than 0.001, indicating a statistically significant difference between unloaded bone cement and cements loaded with 1–4 g of gentamicin. ‘b’ denotes a p-value less than 0.001, indicating a statistically significant difference between Palacos R cement with 0.5 g of gentamicin and Palacos R cement loaded with 1–4 g of gentamicin.

Summary of results from mechanical, physical, and thermal studies of unloaded and gentamicin-loaded bone cements

	Unloaded Palacos R	Palacos R 0.5 g gentamicin	Palacos R with additional gentamicin added:
			1 g	2 g	3 g	4 g
Weibull parameter estimates
Weibull minimum fatigue life, N0(cycles)	46,630	36,316 ^a	10,938 ^a, b	6,311^a, b	7,187 ^a, b	2,208 ^a, b
50% probability of fracture life, N50(cycles)	60,256	48,417 ^a	19,861 ^a, b	16,218 ^a, b	13804 ^a, b	8,318 ^a, b
Weibull characteristic fatigue life, Na(cycles)	62,616	50,220^a	22,363^a, b	20,244^a, b	15947 ^a, b	11,627 ^a, b
Weibull slope, ^b	1.99	1.55 ^a	1.35 ^a, b	1.02 ^a, b	1.08 ^a, b	0.87 ^a, b
Fatigue performance, I	88,342	62,435 ^a	26,023 ^a, b	20,442 ^a, b	16585 ^a, b	10,854 ^a, b
Particle size and distribution, mean (SD)
Particle size (µm)	53.2 (0.41)	51.5 (0.59)	50.0 (0.43)	50.1 (0.72)	50.3 (0.82)	50.2 (0.58)
Particle distibution (µm)	102.0 (1.55)	102.7 (0.45)	99.6 (1.24)	94.3 (1.40)	99.6 (0.97)	99.4 (1.13)
Thermal properties, mean (SD)
Maximum temperature (°C)	54.9 (2.8)	51.8 (3.1)	55.0 (1.6)	56.5 (4.0)	55.1 (1.6)	50.5 (2.5)
Time at max. temperature (min)	14.0 (0.4)	14.9 (0.7)	14.0 (0.6)	14.0 (0.7)	14.4 (0.9)	15.3 (0.8)
Set temperature (°C)	38.0 (1.5)	35.4 (2.1)	36.2 (1.8)	39.8 (2.0)	38.0 (1.1)	35.4 (1.8)
Set time (min)	13.3 (0.7)	14.2 (0.6)	13.1 (0.4)	13.5 (0.7)	13.7 (0.5)	14.3 (0.7)

^a p-value of less than 0.001, indicating a statistically significant difference between unloaded bone cement and cements loaded with 1–4 g of gentamicin.

^b p-value of less than 0.001, indicating a statistically significant difference between Palacos R with 0.5 g of gentamicin and Palacos R cement loaded with 1–4 g of gentamicin.

Figure 5. Micrographs of unloaded and gentamicin-loaded bone cements in which antibiotic agglomerates can be identified as white clusters (arrows show examples). The micrographs of the unloaded Palacos R and Palacos R with 0.5 g gentamicin show no evidence of antibiotic agglomerations. The bone cements containing 1 g or 2 g of gentamicin show a small number of agglomerations within the cement microstructure, and a much larger number is present in the cements containing 3 g or 4 g of gentamicin.

Figure 6. Gentamicin release rates (mean ± SD) from Palacos R bone cements containing additional gentamicin. a denotes a p-value less than 0.001, indicating a statistically significant difference between Palacos R cement with 0.5 g of gentamicin and Palacos R cement loaded with 1–4 g of gentamicin.

Figure 7. Colonization (mean ± SD) of unloaded and gentamicin-loaded bone cements by clinical prosthetic hip isolates: (A.) S. epidermidis, (B.) S. aureus, and (C.) S. capitis. ‘a’, ‘b’ and ‘c’ denote p-values less than 0.001, 0.01, and 0.05, respectively, indicating a statistically significant difference between unloaded bone cement and cements loaded with 1–4 g of gentamicin. ‘d’ and ‘e’ denote p-values less than 0.01 and 0.05, respectively, indicating a statistically significant difference between Palacos R cement with gentamicin and Palacos R cement loaded with 1–4 g of gentamicin.