According to the literature, 15-30% of all emergency room cases involve the hand. Of all hand injuries, tendon lesions account for approximately ⅓ of cases (surpassed only by fractures).
There are 4 common extensor tendons of the long fingers (extensor digitorum), extensor indices for the middle finger and extensor digiti minimi for the 5th digit. Extensor pollicis longus (EPL) and brevis (EPB) control thumb extension.
Together they form the extrinsic system (known as such as the muscles working on the tendons are situated at a distance from the hand itself). This system in turn is supported by the intrinsic system, the local muscles of the hand to produce the array of complex movements available.
The flexor tendons are more complex in that they consist of a system of tendons, pulleys and sheaths. Flexor digitorum superficialis (FDS) and profundus (FDP) run through the carpal tunnel and flexor the long fingers of the hand. Flexor pollicis longus (FPL) also passes through the carpal tunnel and is the main flexor of the thumb.
The inner complexities of the pulley system itself are beyond the scope of this article, but in brief, they serve to maintain the tendons close to the bone and allow a torque force to be applied at the fingers.
A common question asked of the doctor or physiotherapist is “when can I return to work/normal activities?” In order for this to be answered accurately, a brief understanding of how the tendon heals is necessary.
Due to the presence of tendon sheaths, healing can be separated into extrinsic and intrinsic healing. Extrinsic healing is typified by the inflammatory process with its associated symptoms of redness, swelling, heat etc. This is soon followed by the proliferation and then remodelling phases respectively.
Intrinsic healing, which is supported by the movement of the tendons located within the sheath, is the migration of fibroblast type cells to the region, producing collagenous fibres and therefore remodelling.
The importance of differentiating between the two types of healing, also leads to them being correlated. For example, a smaller inflammatory response, coupled with early mobilisation has been shown to provide the tendon with a superior circulatory and therefore nutrient supply, positively affected clinical outcome.
Healing also occurs in stages, regardless of whether intrinsic or extrinsic:
- migration of cells and increased blood vessels at injury site.
- tendon and surround tissues heal
So to answer the original question:
- Normal daily activities: ~ 12 weeks
- Sporting activities: ~ 3 months
- Completely remodelling occurs: ~ 12 months
Open and blunt tendon injuries of the hand, especially of the flexors, require a skilled surgeon and intense post-op care from a rehabilitation team due to the vast number of complex movements the hand is capable of.