The retinacular system is comprised of palmar (volar) fascia and the retaining ligaments of the fingers. Grayson’s and Cleland’s ligaments flank the neurovascular bundle and can play a role in anchoring the skin envelope to the digital skeleton without impeding movement. Grayson’s ligaments pass transversely from the flexor sheath to the skin and lie volar to the neurovascular bundles. They are thought to prevent bowstringing of the neurovascular bundles. Cleland’s ligaments lie dorsally, arising from periosteum and inserting into the skin. The transverse retinacular ligaments anchor the lateral bands to the volar aspect of the proximal phalanx, near the PIP joint. Their function is to prevent excessive dorsal displacement of the lateral bands in PIP joint extension (which occurs in a swan-neck deformity). The ligament of Landsmeer originates on the volar aspect of the middle phalanx and inserts on the dorsal aspect of the distal phalanx. It helps coordinate PIP joint and DIP joint motion (Figs. 70.1 and 70.2).1,2 Cleland’s ligament Transverse metacarpal ligament Transverse fibers, palmar aponeurosis Grayson’s ligament Lateral digital sheet bundle Natatory ligament Spiral band Longitudinal fibers, palmar aponeurosis Fig. 70.1 Distal volar digital fascia. (Adapted from Doyle JR, Botte MJ, eds. Surgical Anatomy of the Upper Extremity. Philadelphia: Lippincott Williams & Wilkins, 2003.)
2. Beasley RW, ed. Beasley’s Surgery of the Hand. New York: Thieme; 2003 The fascial spaces of the hand are potential spaces that are clinically relevant with respect to hand infections. The interdigital web space is the site of a collar button abscess. Drainage usually requires both volar and dorsal approaches. Parona’s space is important with respect to proximal spread of infection from either the midvolar space or from the radial or ulna bursa. It is important to look deep to the digital flexors for pus lying superficial to the pronator quadratus when draining palmar digital infections.1–4 The palmar spaces are illustrated in Fig. 70.3. IO L IVPL TRL ORL SB ED LB TL CS Fig. 70.2 Extensor mechanism. CS, Central slip; ED, extensor digitorum; IO, interosseous; IVPL, intervolar plate ligament (deep transverse metacarpal ligament); L, lumbrical; LB, lateral band; ORL, oblique retinacular ligament of Landsmeer; SB, sagittal band; TL, triangular ligament; TRL, transverse retinacular ligament. (Adapted from Lluch AL. Repair of the extensor tendon system. In: Aston SJ, Beasley RW, Thorne CHM, eds. Grabb and Smith’s Plastic Surgery, 5th ed. Philadelphia: Lippincott-Raven, 1997.) Fig. 70.3 A and B, Fascial spaces of the hand. A B Thenar space Midpalmar space Hypothenar septum Midpalmar oblique septum
3. Teo WZW, Chung KC. Hand infections. Clin Plast Surg 2019;46(3):371–381
4. Jebson PJ. Deep subfascial space infections. Hand Clin 1998;14(4):557–566, viii DORSAL WRIST COMPARTMENTS 3. Which one of the following statements is correct regarding the dorsal wrist compartments? The wrist contains six extensor compartments (not five), which are synovial lined fibro-osseus tunnels through which extensor tendons pass under the retinaculum (Table 70.1). The EIP and EDC tendons pass through the fourth extensor compartment. The posterior interosseous nerve is also found in this compartment, where it terminates to supply the wrist joint. Knowledge of its anatomic location is useful because it can be intentionally resected to treat wrist pain or can be a potential donor for digital nerve grafts. EDM and ECU are located in different compartments (fifth and sixth, respectively). ECRL and ECRB are located in the second compartment and EPL within the third compartment (Fig. 70.4).1–3 Fig. 70.4 Cross section of the wrist illustrating basic anatomic relations of major structures. Note the configuration of the flexor tendons (flexor digitorum superficialis [FDS] and flexor digitorum profundus [FDP] groups). APL, Abductor pollicis longus; ECRB, extensor carpi radialis brevis; ECRL, extensor carpi radialis longus; ECU, extensor carpi ulnaris; EDC, extensor digitorum communis; EDM, extensor digiti minimi; EIP, extensor indicis proprius; EPB, extensor pollicis brevis; EPL, extensor pollicis longus; FCR, flexor carpi radialis; FCU, flexor carpi ulnaris; FPL, flexor pollicis longus. (Adapted from Bentz ML, Bauer BS, Zuker RM. Principles & Practice of Pediatric Plastic Surgery. St Louis: Quality Medical Publishing, 2008.) EPL EIP EDC EDM ECU FDP group Ulnar nerve Ulnar artery FCU FDS Palmaris longus Median nerve Radial artery FPL APL EPB ECRL ECRB Lister’s tubercle Radius Ulna Pronator quadratus Superficial branch of radial nerve Brachioradialis tendon FCR Table 70.1 Muscles of the Dorsal Wrist Compartments Compartment Muscle Insertion Action First APL Base of first metacarpal Extensor of first metacarpal and aids in abduction of thumb EPB Base of proximal phalanx of thumb Combines with EPL to extend thumb IP joint Second ECRL Base of second metacarpal Primarily radial deviation of wrist and secondarily wrist extension ECRB Base of third metacarpal Prime wrist extensor Third EPL Passes around Lister’s tubercle of radius and inserts on distal phalanx of thumb Extends thumb IP joint Fourth EDC No direct bony attachment to proximal phalanx (see Extensor mechanism below) Extends MCP joints and, with intrinsic muscles, extends IP joints EDC to small finger absent in 50% of population EIP Tendon lies ulnar to EDC tendon; functionally independent Extends index finger while others are flexed Fifth EDM Tendon lies ulnar to EDC tendon Prime extensor of fifth MCP joint, allows independent small finger extension Abducts small finger Sixth ECU Inserts on base of fifth metacarpal Primarily ulnar deviation of wrist Secondarily wrist extension
The sagittal bands arise from the volar plate and help to stabilize the extensor tendon over the MCP joint. They may be torn during a punching injury, or sharply divided by a tooth or other sharp object. Although the intact extensor tendon may continue to extend the digit at the MCP joint, there may be painful jumping of the extensor tendon into the gutter between the metacarpal heads in flexion. Initiating extension may also be difficult or painful as the tendon loses some of its mechanical advantage when dropped between the metacarpal heads instead of being held over the dorsum of the metacarpal head by the sagittal bands. Central slip is the insertion of the extensor mechanism on the dorsal base of the middle phalanx where it extends the PIP joint. The juncturae tendinum are tendinous interconnections between EDC tendons on the dorsum of the hand which prevent fully independent action of EDC on a single digit. The lateral bands are formed by the intrinsics and the lateral slips. They insert onto the distal phalanx as the terminal extensor tendon. The transverse retinacular ligament prevents dorsal subluxation of the lateral bands during PIP joint extension.1–3
All four fingers have an EDC tendon which effects a mass extension action. In addition, the index and little finger each have another tendon (EIP and EDM, respectively), which allows for independent extension. These may be used as tendon transfers and it is important to be able to differentiate them anatomically from EDC (see Table 70.1). EPL inserts on the distal phalanx of the thumb. ECRL inserts on the second metacarpal base. The EDC tendons extend over the proximal phalanges as the extensor expansion, including lateral bands and central slip, but do not insert directly into these bones. APL inserts on the base of the thumb metacarpal.1–3
The carpal tunnel usually contains the median nerve and nine flexor tendons (four FDS, four FDP, and FPL). The FDS tendons to the middle and ring fingers lie most superficially alongside the median nerve. FPL lies deep and just ulnar to the FCR tendon at the wrist crease (see Fig. 70.4).1,2
Originally Verdan1 described five zones (not six) of flexor tendon injury, which relate to treatment and prognosis (Fig. 70.6). Bunnell2 had previously described zone II as no-man’s land because of the poor outcomes of repair in this area. This zone lies between the A1 pulley and the FDS (not the FDP) insertion and represents a tight sheath that contains both flexors. The sheath comprises five annular and three cruciate pulleys (Fig. 70.7). These function to prevent bowstringing and improve the mechanical advantage of tendons. The A2 and A4 pulleys are most important in preventing bowstringing and should be preserved during surgery. The odd-numbered annular pulleys are sited at the joints (MCP, PIP, and DIP), whereas the even-numbered pulleys lie over the shafts of the phalanges. All cruciate pulleys lie between the annular pulleys; however, no cruciate pulley exists between A1 and A2. The cruciate pulleys are thinner and more pliable and are thought to distort to accommodate flexion of the digit.
region? The thumb flexor zones differ from those of the other digits and an injury over the proximal phalanx is located in zone II (see Fig. 70.6). The thumb contains only one long flexor and three pulleys (one oblique and two annular) but does not have a cruciate pulley like the fingers. The most important pulley is the oblique pulley and this is at risk of damage in a zone II injury. It is a continuation of the adductor pollicis insertion and lies between the two annular pulleys. These are located at the MCP joint and IP joints. When completely divided, the FPL tendon retracts proximally and is usually found just ulnar/deep to the FCR tendon in the wrist. The neurovascular bundles are less well protected in the thumb as they lie more superficially than in the other digits.1–5 Zone TI Zone TII Zone TIII Zone TIV Zone TV Zone V Zone IV Zone III Zone II Zone I Fig. 70.6 Flexor zones of the hand. (Adapted from Zidel P. Tendon healing and flexor tendon surgery. In: Aston SJ, Beasley RW, Thorne CHM, eds. Grabb and Smith’s Plastic Surgery, 5th ed. Philadelphia: Lippincott-Raven, 1997.) Synovial sheath A1 A2 C1 C2 C3 A3 A4 A5 Fig. 70.7 Flexor tendon sheath pulley system. (Adapted from Zidel P. Tendon healing and flexor tendon surgery. In: Aston SJ, Beasley RW, Thorne CHM, eds. Grabb and Smith’s Plastic Surgery, 5th ed. Philadelphia: Lippincott-Raven, 1997.)
Kaplan1 originally described the cardinal line in 1953 as a line “drawn from the apex of the interdigital fold between the thumb and index finger toward the ulnar side of the hand, parallel with the middle crease of the hand.” It has also been described as a line drawn across the palm from the first web space to the hook of the hamate (Fig. 70.8). Various authors have identified it as a useful landmark in carpal tunnel release because the superficial palmar arch is usually distal to this line, and ensuring dissection stops here should protect it from damage. The princeps pollicis artery usually arises from the deep palmar arch or from the radial artery direct (not the superficial arch) and is the dominant blood supply to the thumb. The ulnar artery lies radial (not ulnar) to the nerve and FCU at the wrist. The digital vessels lie dorsal to the nerves within the fingers, and when patients describe profuse bleeding after sustaining a knife wound to the volar aspect of the digit, they are likely to have also transected the digital nerve. The deep palmar arch is formed by the largest branch of the radial, not ulnar, artery. Superficial palmar arch Deep palmar arch Hook of hamate B A Pisiform Ulnar artery Radial artery Kaplan's line Fig. 70.8 Kaplan’s line in relation to vascular anatomy of the hand.
Most of the extrinsic flexors are innervated by the median nerve, with the exception of the FDP to the little and ring fingers and the FCU. Loss of ulnar nerve function would affect the ability to flex both the little and ring fingers at the DIP joint. Flexion at the PIP joint would be spared because this is controlled by the median nerve innervated FDS. Flexion at the thumb IP joint and index finger DIP joint would also be spared as they are innervated by the anterior interosseous branch of the median nerve. The main wrist flexor is the FCU; however, wrist flexion is still possible with loss of FCU function because of the action of FCR.1
APB is innervated by the recurrent motor branch of the median nerve. It is a useful guide to median nerve function in the hand in relation to carpal tunnel syndrome. All of the other listed muscles are usually innervated by the ulnar nerve.1
The sensory nerve supply to the hand and wrist arises from branches of the radial, ulnar, median, medial antebrachial cutaneous, and musculocutaneous nerves. The lateral antebrachial cutaneous nerve arises from the musculocutaneous nerve, and the posterior antebrachial cutaneous nerve arises from the radial nerve. The sensory distribution differs on the volar surface compared with the dorsal surface (Fig. 70.9).1 A B Volar digital branches (ulnar nerve) Palmar branch (ulnar branch) Medial antebranchial cutaneous nerve (C8,T1) Lateral antebranchial cutaneous nerve (musculocutaneous nerve) Lateral antebranchial cutaneous nerve (musculocutaneous nerve) Posterior antebranchial cutaneous nerve (radial nerve) Superficial branch (radial nerve) Superficial branch and dorsal digital branches (radial nerve) Volar digital branches (median nerve) Proper volar digital branches (median nerve) Palmar branch (median branch) Proper volar digital branches (ulnar nerve) Dorsal branch and dorsal digital branches (ulnar nerve) Medial antebrachial cutaneous nerve (C8,T1) Fig. 70.9 Sensory distribution. A, Volar. B, Dorsal. (Adapted from Beasley RW, ed. Beasley’s Surgery of the Hand. New York: Thieme, 2003.)
BR and ECRL are usually supplied by the radial nerve before it branches into the superficial radial nerve and the posterior interosseous nerve (PIN), although sometimes ECRL is also supplied by the PIN. Therefore, patients with a posterior interosseous nerve palsy may still be able to extend their wrist.1–3
hand. A Riche-Cannieu anastomosis is a motor fiber connection from the ulnar to median nerve in the hand and is thought to be present in as many as 70% of individuals. This can result in preservation of APB function despite a complete division of the median nerve at the wrist. A Martin-Gruber anastomosis is a motor fiber connection from the median to ulnar nerve in the forearm that is present in 10–25% of the United States population.1 A Berretini sensory anastomosis can arise between the common digital nerves derived from the median and ulnar nerves.2 A Martin-Gruber anastomosis can result in preserved ulnar nerve motor function in the hand after a high ulnar nerve injury. The presence of these variations can lead to confusion in a clinical examination, particularly in a trauma setting. When exploring wounds, it is important to be aware of the usual anatomical locations of key branches. The dorsal sensory branch of the ulnar nerve usually arises 5–7 cm proximal to the ulnar styloid process and the palmar cutaneous branch of the median nerve usually arises 5 cm proximal to the wrist crease.
The distal row includes the trapezium, trapezoid, capitate, and hamate. The proximal carpal row includes the scaphoid, lunate, and triquetrum. The scaphoid links the proximal and distal rows and is the most commonly fractured carpal bone (the pisiform is a sesamoid bone within the FCU tendon and is not a functional part of the carpus).1–3