Augmentation of autologous bone graft by a combination of bone morphogenic protein and bisphosphonate increased both callus volume and strength

Figures & data

Figure 1. The region of interest (ROI) for each bone was determined by first identifying the fracture line (dashed line) and then defining a region approximately 3 mm (150 images) proximal and distal to the fracture line (solid lines) (panel A). Within the defined ROI, semi-automatic segmentation was used on each 2D image to identify the circumferential boundaries of the calluses (panel B).

Figure 2. Radiographs of the median samples from each group (based on callus volume) after harvest at 6 weeks.

A. Group A (autograft group) with fracture line still visible.

B. Group B (autograft + BMP) showing larger calluses than in group A.

C. Group C (autograft + BMP + zoledronate) showing an even larger callus and a denser appearance, reflecting increased BMD.

Figure 3. Micro-CT rendered image of median samples from each group (based on callus volume). A. Autograft. B. Autograft + BMP. (C) Autograft + BMP + zoledronate.

Table 1. Bone callus measurements based on microCT. Total callus volume (TVc), highly and lowly mineralized bone volume (BVhigh, BVlow), bone volume fraction (BVhigh / TVc) and tissue mineral density (TMD) were calculated. Mean and standard deviation (SD) are given, as well as statistical significant differences based on Kruskal-Wallis post hoc test (^a p<0.05, ^b p<0.01, ^c p<0.001 compared to group A; ^d p<0.01 compared to group B). ABG stands for saline treated bone graft

Group	TVc (mm3)				BVhigh (mm^3)			BVlow (mm^3)			BVhigh/TVc (%)			TMD (g/cm^3)
	N	Mean	SD	p-value	Mean	SD	p-value	Mean	SD	p-value	Mean	SD	p-value	Mean	SD	p-value
A: ABG	11	118	8		63	4		12	2		54	2		1.08	0.10
B: ABG + BMP	11	241	24	c	96	14	c	23	4	b	40	3	b	1.00	0.06	a
C: ABG + BMP + ZOL	12	436	43	c,d	239	30	c,d	68	14	c,d	55	2	d	0.84	0.09	c,d

Table 2. Mechanical testing outcome for experimental (osteotomized) and the control (contralateral non-fractured) femurs. Based on three-point bending, the ultimate force, stiffness and absorbed energy were calculated. The percentage differences (Diff.) and the statistical differences between the experimental and control side (Wilcoxon signed rank test) are given

Group	Ultimate force (N)							Stiffness (N/mm)						Absorbed energy (Nmm)
	N	Exp.		Control		Diff.	p-value	Exp.		Control		Diff.	p-value	Exp.		Control		Diff.	p-value
		Mean	SD	Mean	SD	(%)		Mean	SD	Mean	SD	(%)		Mean	SD	Mean	SD	(%)
A: ABG	11	88	31	158	24	-57	< 0.001	207	72	461	88	-55	< 0.001	33	36	70	39	-52	0.06
B: ABG + BMP	11	170	38	164	33	3	0.7	257	98	415	111	-38	0.002	107	38	88	28	22	0.1
C: AGB + BMP + ZOL	12	357	104	156	21	129	< 0.001	356	138	398	80	-10	0.3	299	131	59	26	406	< 0.001

Figure 4. Mechanical testing data from the experimental (osteotomized) femurs in Group A, B, and C (see Figure 2). Mean and standard deviation (SD) are given for ultimate force (left panel), bending stiffness (middle panel), and absorbed energy (right panel). Statistically significant differences, based on Kruskal-Wallis post hoc test, are indicated ( ^a p < 0.05, ^b p < 0.001).