Infectious Tenosynovitis

Infections that occur within the tendon sheath may be called infectious tenosynovitis, suppurative tenosynovitis, or purulent tendon sheath synovitis. If they are not detected early and treated appropriately, they very commonly lead to disability of the hand.

The reason is that infection within the tendon sheath causes adhesions of the tendon, preventing it from gliding and resulting in severe loss of joint motion. In addition, impaired blood flow to the tendon may occur, making it possible for the tendon to undergo necrosis and then rupture or become adherent. Thus, if a flexor tendon of a finger becomes adherent, a flexion contracture of the finger occurs; if it ruptures, an extension contracture occurs.

In clinical practice, cases of disability caused by severe flexion contracture of the fingers due to past tendon sheath infection are not uncommon. In the hand, the tendon sheath develops in the areas where the tendon passes through pulleys, and it does not exist in other areas.

Pulleys are well developed in flexor tendons, so most suppurative tenosynovitis occurs there. However, infection sometimes occurs in the extensor tendon sheath behind the wrist joint.

Among the synovial sheaths surrounding the flexor tendons of the fingers, those of the second to fourth fingers extend from the distal phalanx (the last segment of the finger) to the metacarpal head, and also exist within the carpal tunnel, but not between these two regions. However, the synovial sheath of the little finger flexor tendon extends from the distal interphalangeal joint to the wrist joint, and this is called the ulnar bursa.

The synovial sheath of the long flexor tendon of the thumb also extends from the carpal tunnel to the interphalangeal joint, and this is called the radial bursa. These two bursae are usually not connected even within the carpal tunnel, but they are sometimes normally connected. When suppurative infection occurs, it is not uncommon for the membrane separating the two bursae to rupture and create a connection between them. Therefore, infection occurring on the anterior side of the tip of the thumb or little finger can easily spread to the anterior side of the wrist. In addition, infection of the thumb can sometimes spread to the anterior side of the little finger, and infection of the little finger can sometimes spread to the thumb.

If pus accumulated within the carpal tunnel breaks proximally, infection in the Parona space may also be induced.

However, pus that develops in the synovial sheath of the flexor tendons of the second to fourth fingers cannot spread to the wrist, and if a large amount of pus accumulates, it can rupture into the deep palmar space.

Bacterial synovitis occurring in the tendons of the hand can also be divided into acute and chronic forms. The former may be called acute suppurative tenosynovitis and is caused by pyogenic bacteria. The latter refers to infections caused by Mycobacterium tuberculosis, especially atypical mycobacteria, or fungi.

1. Acute Infectious Tenosynovitis

If pus that has developed within the tendon sheath is left untreated, the gliding mechanism of the tendon is destroyed, and adhesions between the tendon and adjacent tissues progress rapidly, causing severe loss of tendon function. This condition is called acute suppurative tenosynovitis.

This occurs because the inside of the tendon sheath is a long, interconnected space filled with synovial fluid, which serves as a good culture medium, allowing the infection to spread across the entire tendon very quickly. When inflammation increases pressure within the tendon sheath, blood flow within the tendon substance is secondarily impaired and the diffusion function of the synovial fluid is also inhibited, making tendon necrosis likely.

Therefore, in the past, it was common for tendons to become adherent or rupture after infection, resulting in severe contractures and stiffness. However, with appropriate use of antibiotics, the prognosis of acute suppurative tenosynovitis has improved considerably.

2. Chronic Infectious Tenosynovitis

This group of diseases may be called chronic suppurative tenosynovitis, but because a large amount of pus does not usually accumulate, the term suppurative is not commonly used. Diseases in this group include tuberculous tenosynovitis and fungal tenosynovitis.

Among these, tuberculous tenosynovitis is commonly found, whereas tenosynovitis caused by fungi is not frequent.

However, when tenosynovitis is severe, fungal cultures should also be performed.

1. Tuberculous Tenosynovitis

Tuberculosis occurs in the tendon sheath or the synovial membrane of joints. In the hands or feet, infection by atypical mycobacteria is said to be more common than infection by Mycobacterium, and among these, M. marinum is known as the most common causative organism. In addition, M. kansasii, M. avium, M. bovis, and M. intracellular are also causes of tuberculous tenosynovitis.

Hand tuberculosis can also occur hematogenously (through the bloodstream). However, in most cases no lesion can be found elsewhere, and in many cases there is a history of direct trauma to the area or an injection, so it is generally thought to result from direct external infection through a wound.

2. Fungal Tenosynovitis

Athlete’s foot caused by dermatophytes is common on the feet and toenails, but not very common on the hands. However, fungal infections of the hand are common in cases of poor nutrition or poor hand hygiene, in occupations involving prolonged immersion of the hands in water, and when the immune system is weakened. Blastomycosis and coccidioidomycosis can cause tenosynovitis, and in such infections, thorough debridement should be performed followed by careful administration of antifungal agents.

So far, I have explained infectious tenosynovitis.

In the next installment, we will look at rheumatoid tenosynovitis.

Source: National Health Information Portal, Korea Disease Control and Prevention Agency