**7.2 Animal model**

The following work has been published in *Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 25, No 12 (December), 2009: pp 1391-1400* (Saw et al, 2009). An excerpt of the published work is described.

be able to regenerate into tissue that will integrate better with the surrounding native structures. This may minimize of delamination which is occasionally seen by the autologous chondrocyte implantation (ACI) technique. Fig 7 shows the potential

**Hemopoetic stem cell** 

Open surgery does not appeal to arthroscopic surgeons. The ideal method of articular cartilage repair would be a single arthroscopic procedure followed by an adjunct cell therapy which could be performed in the out-patient setting. Obviously the desired end result should be the regeneration of the original hyaline cartilage with clinical improvement.

The following work has been published in *Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 25, No 12 (December), 2009: pp 1391-1400* (Saw et al, 2009). An excerpt

The arthroscopic surgeon's wish list for chondrogenesis is listed below:

differentiation process of MSC.

Fig. 7. Potential differentiation process of MSC.

 Single arthroscopic procedure Able to treat multiple/kissing lesions Applicable in large osteochondral defects Simple delivery – intraarticular injections

Hyaline cartilage regeneration

of the published work is described.

 Treat associated injuries Regeneration of soft tissues

Scaffold free

Cost effective

**7.2 Animal model** 

In the animal model, we wished to find out whether postoperative intraarticular injections of autologous marrow aspirate (MA) and HA after subchondral drilling could result in a better cartilage repair.

A 4 mm full thickness articular cartilage defect was created in the stifle joint, followed by subchondral drilling as shown in Fig 8. The animals were divided into three groups: group A (control), no injections; group B (HA), weekly injection of 1 mL of sodium hyaluronate for 3 weeks; and group C (HA + MA), similar to group B but with 2 mL of autologous MA in addition to HA. MA was obtained by bone marrow aspiration, centrifuged, and divided into aliquots for cryopreservation. 15 animals were equally divided between the groups and sacrificed 24 weeks after surgery, when the joint was harvested, examined macroscopically and histologically (Fig 9).

Fig. 8. (A&B) A 4mm full thickness articular cartilage defect was created in the stifle joint, followed by subchondral drilling.

#### **7.2.1 Macroscopic findings**

The chondral defects were covered with repair tissue in all groups, without evidence of synovitis or synovial thickening (Fig 9). In group A the defects were covered with semitransparent tissue having recognizable margins but with an irregular surface. A similar appearance was seen in group B goats. In group C the defect coverage was almost complete, and the color of the repair tissue was indistinct from surrounding cartilage. The surfaces were smooth and appeared level with adjacent normal cartilage.
