The injection of autologous blood into a tendon is a relatively new procedure within the UK but has been pioneered for a few years in the U.S. The principle is relatively straightforward; the patients own (autologous) blood is taken from a vein and then reinjected in and around the diseased tendon in order to promote the healing process. What follows is an explanation of why this would be undertaken, how it works and how the procedure is undertaken.

Tendinitis, tendinosis or tendinopathy?

In medical jargon the suffix (the end of the word) describes the underlying disease process affecting the structure described. Tonsillitis literally means inflammation of the tonsils. For many years it was thought that the cause of pain in tendons was due to inflammation of the tendon fibres and hence it was called a tendinitis. However new research has demonstrated that there are no signs of inflammation in an established diseased tendon. Rather the tendon fibres showed signs of disorganisation and lack of repair suggesting a degenerative cause and hence it is more correctly known as either a tendinosis or a tendinopathy (diseased tendon).

Why do tendons fail to repair?

Having established that the problem was due to failure of healing the next question is why does this happen. Researchers are still pondering this however there are three main theories.

The mechanical theory suggests that excessively exercising a tendon causes tiny tears that fail to heal up before the next bout of activity. Small tears lead to bigger ones weakening the tensile strength of the tendon which leads to further damage. A downward spiral of trauma.

The vascular theory maintains that exercise restricts the blood supply to the tendon. Depleted of the necessary oxygen and nutrients supplied from blood the tendon struggles to repair itself and degenerates as a consequence.

Tendons are highly innervated by nerves. The neural theory proposes that excessive tendon activity causes irritation to these nerves and in response they release harmful chemicals into the tendon structure leading to degradation.

The role of autologous blood

Following any injury there is localised bleeding into the damaged tissue concentrating blood products. The presence of blood initiates the inflammatory cascade which kick-starts the body into repairing itself. The first blood products to arrive at the scene are known as platelets which are packed full of growth factors. As the name implies these growth factors instigate the re-growth of cells to replace those damaged. Blood contains lots of platelets.

The rationale for the use of autologous blood, therefore, is to inject large quantities of platelets into and around the tendon. By delivering these growth factors right next to the degenerative tendon tissue the hope is that the healing process is boosted and the regeneration of healthy tendon fibre begins.

The autologous blood injection procedure

Having identified the part of the tendon to be treated with an ultrasound scan a vial of local anaesthetic (pain killer) is injected around the site. This takes a few minutes to have its effect. A
small volume of blood (between 3 to 5 ml) is taken from the vein of an arm, identical to having a blood test. This blood is then injected into and around the tendon guided by the ultrasound scan. For some tendons as this being done the needle is also passed repeatedly through the tendon (fenestration) in order to facilitate further localised bleeding.

The procedure is not particularly painful akin to having dental work. However all patients are warned that a few hours later as the local anaesthetic wears off there can be discomfort especially if fenestration was employed. Painkillers and ice are sufficient to control this. Patients rest from activity for a few days then start a specific rehabilitation programme prescribed by the medical practitioner. Sometimes it is necessary to repeat the procedure after a couple of months.