The sheaths of a patient's flexor tendons come nearest to his skin as they pass under the flexor creases of his fingers. It is here, and particularly over his distal flexor crease, that they are most often punctured and infected. They can also be infected by spread from a pulp infection. The sheaths of his little finger and thumb (and occasionally those of his other fingers also) extend proximally into his palm, and so provide a path through which infection can spread there. If an infected tendon sheath bursts, it does so into the middle palmar space, through one of the lumbrical canals.
There are problems: (1) An infected tendon may later stick to its sheath and make a finger stiff. (2) If pressure inside a sheath exceeds that in its vessels, which can occur if drainage is delayed, the tendon will become ischaemic and slough.
If infection is localized or one area is maximally infected, staphylococci are usually causing it. Only one segment of his finger is swollen, so that distinguishing a localized tendon sheath infection of this kind from an infection of one of his middle palmar and thenar spaces can be difficult (8.9).
If infection is fulminating, streptococci are usually responsible, and his whole finger is swollen, sausage shaped and acutely tender, without becoming red. The swelling extends into his distal palm. He holds his finger partly flexed, and cannot bend it, except perhaps for a little movement at its MP joint.
The danger when you open a tendon sheath is that you may cut a patient's digital nerves. So study where these run in the cross-section of the finger shown in G, Fig 8-6. Either approach a tendon laterally, well towards the dorsum, or from the palm. The danger area is the ''palmolateral' region. The other nerve which is in danger is the motor branch of his median nerve as it curves round the distal end of his flexor retinaculum and the tubercle of his trapezium.
Adjust your incisions to the severity of the infection. You can approach an infected tendon sheath: (a) Along the side of a finger towards the dorsum (incision 7). (b) Through several transverse incisions on his palm (incisions 8, see Fig. 8-7). (c) By making zig-zag cuts on his palm (incisions 9); these give the best exposure, but take longer to heal. Incisions 7 and 8 are for less severe infections.
Tendon sheath infections are a common complication of the anaesthetic hands of leprosy (30.4), which allow a patient to neglect an infection until it is so advanced that it has destroyed his tendon sheaths.
Fig. 8-7 INFECTIONS OF THE TENDON SHEATHS. A, lateral incisions for opening an infected tendon sheath (incision 7). B, the anatomy of a tendon sheath, to show the fibrous pulleys opposite the shafts of the phalanges. C, the surface markings of the tendon sheaths. D, transverse incisions for draining tendon sheaths (incisions 8). E, opening the distal cul-de-sac (incision 8a). F, irrigating a tendon sheath. E, and F, after ''Farquharson's Textbook of Operative Surgery', edited by RF Rintoul, Figs. 317 and 318. Churchill Livingstone, with kind permission.
FLEXOR SHEATH INFECTIONS For the general method for a hand infection, see Section 8.1.
EXPOSING [s7]THE TENDON SHEATHS Start by opening the soft tissue over the involved segment through a small lateral incision (incision 7). Examine the synovial sheath. If there is any sign of infection (redness, or thickening) open the sheath itself and look carefully at the fluid. If there is much fluid, it is probably infected; if it is even a little cloudy, it is certainly infected.
If a sheath is infected, make several incisions over the patient's finger(s) and distal palm (incisions 8a, and 8b). Hold the sheath open with hooks and retractors. Using a stiff catheter, syringe the sheath with saline or sterile water (F).
If a sheath is infected in his palm (as is usual with his little finger and thumb), make a further incision (incision 8c) at his wrist, and repeat the irrigation, inserting the catheter through the palmar incision.
If his tendon sheaths are grossly infected, operate urgently. Open the sheath by a zig-zag incision on the volar surface of his finger as in Fig. 8-6. Do this in two stages. First cut along the solid lines (9a), then, if necessary join up these incisions by cutting along the dotted ones (9b). Cut the flaps in the palm larger than those in the fingers, and make them follow his skin creases where possible. Cut through his skin and open the tissues with scissors. Leave bridges of the sheath over the joints to act as pulleys to prevent the tendons prolapsing.
CAUTION ! Don't take the incisions laterally where they may injure his neurovascular bundles.
Wash out the pus with saline. Don't close the incision; the flaps will heal by granulation to leave a linear scar.
If a tendon has become a grey slough, extend the incision, withdraw the dead part into the wound, and excise it. Preserve its sheath and pulley. Allow the wound to heal. If his hand settles well it may be possible to insert a tendon graft later. This will only be worthwhile if the joints of his fingers are mobile. So, as soon as the swelling is starting to settle, he needs intensive physiotherapy, both by himself and a by a physiotherapist[md]this is vital! If his finger remains stiff, try to persuade him that it should be amputated. A stiff finger can be a severe handicap.
If a tendon and its sheath are extensively disorganized, consider amputating his finger. If you don't do so: (1), infection may spread and cause further damage, (2) when his finger heals, it will be stiff, and cause considerable disability by impairing the grip of his other fingers. It may be better amputated. But a stiff thumb is much better than no thumb, so retain it.
If his palm is seriously infected, divide his flexor retinaculum to free his tendons. Either: (a) Approach this through a longitudinal incision 1 cm to the ulnar side of his scaphoid tubercle. Make a 5 cm longitudinal incision over his retinaculum. Keep to the ulnar side of his median nerve and its ulnar branch (incision 10) Or, (b) use the approach shown for the ulnar bursa (incision 3). Both are shown in Fig. 8-6.
AN UNNECESSARY INCISION IS BETTER THAN A LOST FINGER