Abstract
In atrophic non-union models, a minimally invasive technique is used to deliver stem cells into the fracture site via percutaneous injection. This technique is significantly affected by a backflow leakage and the net number of cells might be reduced. The Z-track method is a technique used in clinical practice for intramuscular injections to prevent backflow leakage.
We evaluated the potential of the Z-track injection technique for preventing cell loss in non-union models by determining the behaviour of observable marker fluids. Firstly, toluene blue stain was used as an injection material to allow visual detection of its distribution. Rat's cadaver legs were used and tibias were kept unbroken to ensure intact skin and overlying soft tissue. Technique includes pulling the skin over the shin of tibia towards the ankle and injection of the dye around the mid-shaft. The needle was then partially pulled back, the skin was returned to its normal position and a complete extraction of the needle was followed. Secondly, a mixture of contrast material and toluene blue was used to allow direct visual and radiological detection of the injected material into the fracture site. Ante-grade nailing of tibia via tibial tuberosity was carried out followed by a 3 point closed fracture. Injection was performed into the fracture gap similarly to the steps above. X-rays were taken to visualise the location and distribution of the injected material.
Observation revealed no blue stain could be detected over the skin, X -rays revealed that the radiopaque dye remained around the tibia with no escape of the material into the superficial layers or onto the skin surface. Therefore, the number of cells delivered and maintained at a target site could be increased by the Z-track method and therefore, the therapeutic benefit of stem cell injections could be optimised with this simple technique.
