33 Hand Spaces

33.1 Introduction

Hand spaces can be affected by injury, inflammatory process, or infection. ¹ A thorough knowledge of the anatomy of these spaces is essential for proper understanding of pathophysiology and surgical management of conditions involving these spaces.

There are two varieties of hand spaces: (1) potential anatomical spaces that are bordered within muscle planes or by fascial bands and (2) true anatomical spaces that are lined by synovial membrane.

Based on their anatomical location, hand spaces can be classified into the following types:

I. Perionychium and pulp space
II. Superficial potential spaces
1. Digital spaces
  - Dorsal
  - Palmar
2. Dorsal hand spaces
  - Subcutaneous
  - Subaponeurotic
3. Palmar hand spaces
4. Interdigital web spaces
III. Synovial spaces
1. Extensor tendon sheath
2. Flexor tendon sheath
3. Radial and ulnar bursae IV. Deep potential spaces
4. Space of Parona.
5. Thenar space.
6. Mid palmar space.
7. Lumbrical spaces.
8. Hypothenar space.

33.2 Perionychium/Pulp Space

The nail plate is made of solid keratin and has a root and body. The nail root is contained in the nail socket. The proximal cornified thin skin layer that covers the nail plate is the eponychium, which extends a variable distance onto its surface. The lateral skin fold is called the paronychium, whereas the distal skin beneath the nail margin is the hyponychium.

Kanavel described the anatomy of the distal pulp as a “closed sac of connective tissue framework isolated and different from the rest of the finger.” ¹ Multiple fibrous bands (▶Fig. 33.1, ▶Fig. 33.2, and ▶Fig. 33.3) extend from the periosteum of the distal phalanx to the dermis, dividing the pulp into numerous compartments that are potential spaces for spread of infection from the nail bed. ²

**Fig. 33.1** (**a,b**) Diagram of sagittal section through the fingertip showing the fibrous bands running from the distal phalanx to the dermis. (From Schmidt H-M, Lanz U. Surgical Anatomy of the Hand. Stuttgart, Germany: Thieme; 2004.)

**Fig. 33.2** (**a,b**) Diagram of axial section of the pulp and nail along with the distal phalanx showing the detailed anatomy of the fingertip. (From Schmidt H-M, Lanz U. Surgical Anatomy of the Hand. Stuttgart, Germany: Thieme; 2004.)

**Fig. 33.3** Dissection of the fingertip showing the insertion of the FDP tendon and the fibrous septae running from the distal phalanx to the pulp skin and the spaces they create. Also seen are the interosseous ligaments of Flint.

Subungual or paronychial infection may occur de novo or spread from a pulp space. The tight septa can cause considerable swelling and pain from pressure caused by purulence or bleeding. Infection is contained in the pulp for a while, but if not relieved either by spontaneous drainage or surgically, it can spread to the bone, causing osteomyelitis of the distal phalanx, to the distal interphalangeal joint, causing septic arthritis, or to the flexor tendon sheath, causing septic flexor tenosynovitis.

33.3 Superficial Spaces

33.3.1 Subcutaneous Dorsal and Palmar Digital Spaces

The dorsal skin of the digit is loose and attached to the deeper structures at the metacarpophalangeal (MCP), proximal, and distal interphalangeal joints by dorsal paratendinous cutaneous system that arises from the central and terminal tendons, respectively, and insert directly into the dermis deep to the dorsal skin crease of the finger joints ³ (▶Fig. 33.4). These fibers are probably a continuation of Cleland’s ligaments and were originally described by Cleland. ³

**Fig. 33.4** *Dorsal paratendinous cutaneous system* arising from the extensor tendons and attaching to the dermis at the PIP joint skin crease. (From Zancolli EA, Cozzi EP. Atlas of Surgical Anatomy of the Hand. New York, NY: Churchill Livingstone; 1992.)

Thus the dorsal subcutaneous areas over the middle and proximal phalanges are potential spaces that can be filled with fluid, blood, pus, or granulation tissue. The space over the proximal phalanx has direct connection to the loose subcutaneous space on the dorsum of the hand, as the paratendinous cutaneous system over the MCP joint is less robust and the skin on the dorsum of the MCP joint is much more mobile.

The primary function of the cutaneous ligaments is to provide stability to the skin by tethering it to the deeper fascial or bony structures. The Cleland’s ligaments attach in the vicinity of the lateral borders of these joints and lie dorsal to the digital neurovascular bundles. The Grayson’s ligaments are slender fibrous strips that extend from the flexor tendon sheath to the palmar skin of the digits and lie volar to the neurovascular bundle ³ (▶Fig. 33.5). The dorsal digital cutaneous creases form areas of skin tether to the deeper fascial structures (▶Fig. 33.4). Between the adjacent digital creases are potential subcutaneous spaces that can harbor infection.

**Fig. 33.5** Dissection of the digit showing Grayson’s ligaments.

At the palmar digital skin creases, the skin is attached to the deeper structures (▶Fig. 33.6). The area in between the palmar digital creases form a potential space for fluid collection.

**Fig. 33.6** Dissection showing the palmar and digital skin creases. The subcutaneus spaces between the creases are potential areas for fluid collection.

33.3.2 Superficial Dorsal Hand Spaces

The superficial dorsal spaces include the dorsal subcutaneous and the dorsal subaponeurotic space ¹ (▶Fig. 33.7 and ▶Fig. 33.8).

**Fig. 33.7** The dorsal subcutaneous and the dorsal subaponeurotic spaces in the back of the hand.

**Fig. 33.8** Cross sectional specimen showing the dorsal subcutaneous and the dorsal subaponeurotic spaces. (From Thurmuller P, Schubert M, Bade H. Functional gliding space of the dorsal side of the human hand. The Anatomical Record 2002 267; 242-251. With permission.)

The dorsal subcutaneous space lies between the loose dorsal skin of the hand and the deeper extensor tendons and the dorsal aponeurosis. ¹ ^, ⁴ Distally it communicates with the space over the proximal phalanx, as the paratendinous cutaneous fibers are less robust over the dorsum of the MCP joints. The wrist skin creases define the limit of this space proximally. This large space on the dorsum of the hand and fingers can be potentially increased by poor finger position after injury whereby the MCP joint is hyperextended and the proximal interphalangeal (PIP) joint is flexed (▶Fig. 33.9). Placing the hand in the intrinsic plus or “safe position” with the wrist slightly extended, the MCP joints flexed, and PIP joints extended pulls the dorsal skin tight and reduces the size of this space and decreases edema fluid accumulation in this space.

**Fig. 33.9** MP joint hyperextension and PIP joint flexion increases the potential space on the dorsum of the hand.

The deeper dorsal subaponeurotic space lies between the aponeurotic network of the extensor tendons and their connections superficially and the periosteum over the metacarpals (▶Fig. 33.7 and ▶Fig. 33.8) and the fascia covering the interosseous muscles. ¹ ^, ⁴ On the radial and ulnar sides, the aponeurotic sheath merges with the fascia covering the dorsal interosseous muscles and the periosteum of the thumb and the small finger compartments as well as the capsules of these MCP joints, forming what Kanavel termed a “truncated cone.” The thin fascia between the extensor tendons—intertendinous fascia of Anson—extends to the space between the thumb and index metacarpals, connecting the extensor tendons of these two digits ⁵ (▶Fig. 33.10). Therefore, this aponeurosis spans the first dorsal interosseus muscle and fascia as well as the adductor pollicis muscle and forms a curved edge on the dorsum of the first web space. Thus, the dorsal subaponeurotic space extends to the thumb metacarpal on the radial side.