**2.5 Histologic and histomorphometric analyses**

Rabbit knee joints were collected and fixed in a neutralized formalin solution for 2 days and decalcified in 10% formic acid until being cut. The specimens were sliced into 4-um-thickness in an orientation parallel to the bone tunnel, and each section was stained with Masson's trichrome, and visualized using an optical microscope. Healing of the tendon in the bone tunnel was graded histomorphologically by two blinded observation methods.

Histomorphometric analysis was assessed for tendon healing in the bone tunnel. Quantitative histomorphometric analysis was performed by two blinded observations, which apportioned 0–3 points based on histomorphologic criteria, representing fibrocartilage formation, new bone formation, and tendon graft bonding to adjacent tissue (**Table 1**).


**Table 1.**

*Histomorphometric analysis to assess healing of the tendon within the bone tunnel (full score = 9 points).*

**143**

**Figure 2.**

*The Injectable rhBMP-2-containing Collagen Gel for Tendon Healing in a Rabbit…*

The data were averaged from at least triplicated samples. The same experiments were repeated for three times to ensure the reproducibility of the methods used. All statistical analyses were performed using SPSS version 15.0. The post hoc Scheffé test was sued to analyze the significant difference between groups, with significance

The turbidity of collagen gel at 37°C was significantly increased between the time points of 10 (OD: 0.953) and 20 (OD: 4.099) minutes (**Figure 2**). The half release from the total rhBMP-2 quantity from the collagen gel was done within 5 days from incubation. And the rest half was released slowly for over 28 days when it was released 89.3% totally. The rhBMP-2 conjugated collagen gel showed a

In the 3D-CT analysis, new bone formation was detected at the interface between the tendon and tibia bone tunnel in the rhBMP-2-collagen gel group after 3 weeks even though the normal distal epiphyseal plate of rabbits has a limited cancellous bone. However, the control and collagen gel groups did not show new bone formation (**Figure 4**). At 6 weeks after the surgery, the rhBMP-2-collagen gel group

*Ultraviolet turbidity of 1% collagen gel at each time point, dependent on temperature; average of triplicates at* 

*each time point, which is 0, 10, 20, and 30 min at 37°C incubation.*

*DOI: http://dx.doi.org/10.5772/intechopen.82471*

**2.6 Statistical analysis**

**3. Results**

levels at \*p < 0.05 and \*\* < 0.01.

sustained release phase (**Figure 3**).

*The Injectable rhBMP-2-containing Collagen Gel for Tendon Healing in a Rabbit… DOI: http://dx.doi.org/10.5772/intechopen.82471*

### **2.6 Statistical analysis**

The data were averaged from at least triplicated samples. The same experiments were repeated for three times to ensure the reproducibility of the methods used. All statistical analyses were performed using SPSS version 15.0. The post hoc Scheffé test was sued to analyze the significant difference between groups, with significance levels at \*p < 0.05 and \*\* < 0.01.
