Rinsing of allograft bone does not improve implant fixation

Figures & data

Figure 1. Gap-implant in the proximal tibia. Radiograph taken post mortem.

Figure 2. Experimental porous-coated titanium 2.5 mm gap implant with measurements.

Table 1. Allograft wash

	Weight	Volume	Volume/impl.
	(g)	(cm^3)	(cm^3)
Control	22.08	19.62	1.23
Rinsed	22.44	17.82	1.11
Difference rinsed/control	1.63%	–9.17%

Volume and weight were measured after water was drained with maximum manual pressure.

Figure 3. Bone graft of the 2 treatment groups.

Figure 4. Histology: representative histological sections from the two groups. The sections shown are from the two implants inserted in the same animal. Porous-coated Ti implants are surrounded by a 2.5-mm concentric defect. The sections are cut parallel to the long axis of the implant. Left-hand panels (control): fibrous (FIB) tissue at the implant (IMPL) surface. Right-hand panels (rinsing): new bone (NB) on graft (AG) remnants.

Table 2. Biomechanical results

Groups	Shear strength	Shear stiffness	Energy absorption
	(MPa)	(MPa/mm)	(KJ/m^2)
Control ^a	2.7 (1.0)	15 (6.7)	0.5 (0.2)
Rinsed ^a	2.9 (1.2)	15 (5.6)	0.6 (0.4)
Rinsed – Control ^b	0.2 (–0.3 to 0.6)	0.0 (–2.8 to 2.8)	0.1 (–0.2 to 0.3)
p-value (t-test)	0.5	1.0	0.5

^a Mean (SD).

^b Absolute difference between treatment groups. Mean (95% CI).

Table 3. Histomorphometrical analysis: tissue area fraction on implant surface and tissue volume fraction in the gap (ingrowth)

	New bone	Bone graft	Fibrous tissue
	mean% (SD)	mean% (SD)	median% (IQR)
Implant surface
Control	6 (3.7)	0 (0.2)	18 (3–31)
Rinsed	7 (2.9)	0 (0.2)	7 (1–18)
Rinsed – Control ^a	0 (–1.1 to 3.0)	0 (–0.1 to 0.3)
p-value	0.3 ^b	0.4 ^b	0.2 ^c
Ingrowth
Control	9 (2.7)	13 (4.1)	4 (1–6)
Rinsed	9 (3.3)	13 (4.4)	2 (1–5)
Rinsed – Control ^a	0 (–2.1 to 3.0)	0 (–1.5 to 2.7)
p-value	0.7 ^b	0.5 ^b	0.3 ^c

IQR: interquartile range.

^a Absolute difference between treatment groups. Mean (95% CI).

^b T-test

^c Wilcoxon