This is the most important space in the hand, and is frequently infected in leprosy patients (30.4). It lies deep to a patient's flexor tendons and lumbricals, and between them and the fascia covering his interossei and metacarpals. It is separated from his thenar space by a fibrous septum which extends from his middle metacarpal towards his palmar fascia. Infection reaches this space from a lumbrical canal, or from an infected tendon sheath.
His hand is so grossly swollen that it looks like a blown-up rubber glove. The normal hollow of his palm is obliterated, and the dorsum of his hand is swollen. He cannot move his middle or ring fingers. His interossei are surrounded by pus and paralysed, so that if you ask him to hold a piece of paper between his extended fingers he cannot do so.
The middle palmar space communicates through the carpal tunnel with a space deep to the flexor tendons in the forearm (the space of Parona). If there is pus there you may be able to detect fluctuation between it and the pus in his palm.
MIDDLE PALMAR SPACE. For the general method for a hand infection, see Section 8.1. Always use a tourniquet.
Make a transverse incision (incision 2) in the middle third of the patient's distal or proximal palmar creases or wherever fluctuation is maximal. Enter his middle palmar space on either side of the flexor tendon of his ring finger. Or, enter it through an incision along the ulnar border of his hand, passing between his 5th metacarpal and his hypothenar muscles (incision 3). As soon as you are through his skin, use blunt dissection (Hilton's method) in the line of his tendons and nerves. See also under ''ulnar bursa' (8.13).
CAUTION ! (1) Don't make your initial incision deeper than his palmar fascia. Push a blunt instrument through it to free the pus underneath. You can then see clearly to open up the space more by a combination of sharp and gentle blunt dissection. (2) Don't cut his digital nerves or vessels, his flexor tendons, or his lumbrical muscles.
If there is pus in the space of Parona, drain it through a longitudinal incision (incision 6) on one side of his palmaris longus tendon (absent in 5% of people), taking care not to injure his median and ulnar nerves or his radial and ulnar vessels.
Fig. 8-5 A SEVERE HAND INFECTION. This started as a web infection which spread to the patient's middle palmar space. A, shows the standard site of the incisions for a middle palmar space infection (incisions 2 and 3), and B that for web space infections (incisions 1). In this patient these incisions had to be modified. C, shows the callosity through which infection entered. Although the back of his hand was swollen (D) it was not incised, because the swelling was due to secondary inflammatory oedema only. E, pus was found in his distal palm, his three web spaces, and his flexor sheaths. The spaces were drained and necrotic tissue was excised. F, eight days after the incision the web spaces have been grafted. After ''Campbell's Operative Orthopaedics', edited by AS Edmondson and AH Crenshaw[md]the Chapter on ''Hand infections' by Lee Milford, Figs. 3-355 and 3- 356. CV Mosby, with kind permission.