Evaluation of the internal fixation effect of nano-calcium-deficient hydroxyapatite/poly-amino acid composite screws for intraarticular fractures in rabbits

Figures & data

Figure 1 (A) The φ 3.5× (20–22) mm stainless-steel screw and (B) n-CDHA/PAA screw.

Abbreviation: n-CDHA/PAA, nano-calcium-deficient hydroxyapatite/poly-amino acid.

Figure 2 (A) The intercondylar fracture model of the femur; (B) control group was fixed with metal screw; and (C) experimental group was fixed with n-CDHA/PAA screw.

Note: Gray arrow indicates the metal screw cap and blue arrow indicates the n-CDHA/PAA screw cap.

Abbreviation: n-CDHA/PAA, nano-calcium-deficient hydroxyapatite/poly-amino acid.

Table 1 The adjusted OAS system

OAS	Points
Fracture gap level with surrounding cartilage
Level	2
Raised	1
Below	0
Integration of fracture gap level with surrounding cartilage
Complete	2
Minor disruption (<25% of area)	1
Major disruption (>25% of area)	0
Stiffness in fracture gap
Normal compared with adjacent cartilage	2
Softer	1
Very soft/hard	0
Appearance of articular surface
Smooth	2
Fine fronds	1
Severe fronds/fibrillation	0
Color of articular surface
Pearly, hyaline-like	2
White	1
Yellow bone	0
Total	0–10

Abbreviation: OAS, Oswestry Arthroscopy Score.

Figure 3 The axial push-out test diagram.

Notes: (A) Push bin; (B) methyl methacrylate cement (including the harvested distal femoral condyle); and (C) clamp.

Figure 4 The specimen of harvested distal femoral condyles at 4 (A), 8 (B), and 12 (C) weeks after surgery in the control group; the specimen of harvested distal femoral condyles at 4 (D), 8 (E), and 12 (F) weeks after surgery in the experimental group.

Figure 5 (A) The X-ray results at 4 weeks after surgery in the control group (a, anteroposterior view; b, lateral view) and in the experimental group (c, anteroposterior view; d, lateral view). (B) The X-ray results at 8 weeks after surgery in the control group (a, anteroposterior view; b, lateral view) and in the experimental group (c, anteroposterior view; d, lateral view). (C) The X-ray results at 12 weeks after surgery in the control group (a, anteroposterior view; b, lateral view) and in the experimental group (c, anteroposterior view; d, lateral view).

Figure 6 The Lane-Sandhu scores in the control and experimental groups.

Note: *P>0.05, compared with control group (n=5).

Figure 7 The range of motion of knee joints in the control and experimental groups.

Note: *P>0.05, compared with control group (n=5).

Table 2 The results of adjusted OAS for femoral intercondylar fracture

Time (weeks)	Group	Appearance of articular surface			Color of articular surface			Fracture gap level with surrounding cartilage			Integration of fracture gap with surrounding cartilage			Stiffness in fracture gap			Total
		Min	Max	Avg	Min	Max	Avg	Min	Max	Avg	Min	Max	Avg	Min	Max	Avg
4	Control	0	1	0.6	0	1	0.6	0	1	0.6	0	1	0.6	0	1	0.8	3.2
	Experimental	0	2	0.8	0	2	1.0	0	1	0.4	0	1	0.6	0	1	0.8	3.6
8	Control	0	1	0.8	1	2	1.2	0	2	1.2	1	2	1.4	1	2	1.4	6.0
	Experimental	0	2	1.2	1	2	1.4	0	2	1.0	1	2	1.2	1	2	1.2	6.0
12	Control	1	2	1.4	1	2	1.6	1	2	1.8	1	2	1.8	1	2	1.8	8.4
	Experimental	1	2	1.8	1	2	1.8	1	2	1.6	1	2	1.6	1	2	1.8	8.6

Abbreviation: OAS, Oswestry Arthroscopy Score.

Figure 8 The results of push-out strength in the control and experimental groups.

Note: *P<0.01, ^#P>0.05, compared with control group (n=5).

Figure 9 The weight loss of n-CDHA/PAA screw in vivo (n=5).

Abbreviation: n-CDHA/PAA, nano-calcium-deficient hydroxyapatite/poly-amino acid.

Figure 10 The result of XRD of n-CDHA/PAA screw.

Notes: (A) The outer surface of n-CDHA/PAA before implantation; (B) The internal cross-section of n-CDHA/PAA after implantation; (C) The outer surface of n-CDHA/PAA after implantation.

Abbreviations: n-CDHA/PAA, nano-calcium-deficient hydroxyapatite/poly-amino acid; XRD, X-ray diffraction.