MUSCLE	INNERVATION*	FUNCTION
Abductor pollicis brevis (APB)	Median	Abducts the thumb
Flexor pollicis brevis (FPB)	Median	Flexes the thumb
Opponens pollicis (OP)	Median	Opposes the thumb
Lumbricals	Median and ulnar	Flexes metacarpal phalangeal (MCP) joints and extends interphalangeal (IP) joints
Palmaris brevis	Ulnar	Wrinkles the skin on the medial (ulnar) side of the palm
Adductor pollicis (AdP)	Ulnar	Adducts the thumb
Abductor digiti minimi (ADM)	Ulnar	Abducts the small finger
Flexor digiti minimi (FDM)	Ulnar	Flexes the small digit
Opponens digiti minimi (ODM)	Ulnar	Opposes the small finger
Dorsal interossei	Ulnar	Abducts the fingers; flexes MCP joints and extends the IP joints
Palmar interossei	Ulnar	Adducts the fingers; flexes MCP joints and extends the IP joints

* All the thenar intrinsic muscles are supplied by the median nerve except the AdP; all the remaining intrinsic muscles are supplied by the ulnar nerve except the two radial lumbricals.

The extrinsic muscles originate proximal to the wrist and comprise the long flexors and extensors of the wrist and digits. The extensors are located dorsally and are divided into three subgroups. The radialmost subgroup is termed the mobile wad and comprises the brachioradialis (BR), extensor carpi radialis longus (ECRL), and extensor carpi radialis brevis (ECRB). The ECRL and ECRB extend the wrist and deviate it radially. The second group is located in a more superficial layer and comprises three muscles—namely, the extensor carpi ulnaris (ECU), extensor digiti minimi-quinti (EDM-Q), and extensor digitorum communis (EDC). The ECU deviates the wrist in an ulnar direction and extends the wrist, whereas the EDM and EDC extend the MP joints of the fingers. The third and deeper subgroup comprises four muscles, three of which act on the thumb; the remaining muscle influences the index finger. The abductor pollicis longus (APL), extensor pollicis longus (EPL), and extensor pollicis brevis (EPB) provide function to the thumb, and the extensor indicis proprius (EIP) extends the MP joint to the index finger. Last of the deep muscles is the supinator, which is located proximally in the forearm (Table 70-2).

Table 70-2 Extrinsic Muscles of the Dorsal Forearm

MUSCLE	INNERVATION*	FUNCTION
Extensor pollicis brevis (EPB)	Radial	Abducts the hand and extends the thumb at the proximal phalanx
Abductor pollicis longus (APL)	Radial	Abducts the hand and thumb
Extensor carpi radialis longus (ECRL)	Radial	Extends and radially deviates the hand
Extensor carpi radialis brevis (ECRB)	Radial	Extends and radially deviates the hand
Extensor pollicis longus (EPL)	Radial	Extends the distal phalanx of the thumb
Extensor digitorum communis (EDC)	Radial	Extends the fingers and the hand
Extensor indicis proprius (EIP)	Radial	Extends the index finger
Extensor digiti minimi/quinti (EDM/Q)	Radial	Extends the small finger
Extensor carpi ulnaris (ECU)	Radial	Extends and ulnarly deviates the wrist
Supinator	Radial	Supination
Brachioradialis	Radial	Flexes the forearm

* All muscles of the dorsal forearm are innervated by the radial nerve and its respective branches.

The extensor tendons pass through six compartments deep to the extensor retinaculum at the dorsum of the wrist. From radial to ulnar side, these tendons and compartments are arranged as follows. The first compartment contains the APL and EPB, which also forms the radial boundary of the so-called anatomic snuffbox. The second compartment consists of the ECRL and ECRB, and the third compartment (which also forms the ulnar boundary of the anatomic snuffbox) contains the EPL. The EIP and EDC pass through the fourth compartment and the EDM through the fifth compartment, where they overlie the distal radioulnar joint. The sixth compartment contains the ECU (Fig. 70-3).

FIGURE 70-3 A, B, Surface anatomy of the six dorsal extensor compartments at the wrist. Note that the first (APL and EPB) and third (EPL) compartments form the radial and ulnar boundaries, respectively, of the anatomic snuffbox.

At the level of the MP joints, the long extrinsic extensor tendons broaden out to form the extensor hood. The proximal part of the hood at this level is called the sagittal band. It loops around the MP joint and blends into the volar plate, thus forming a lasso around the base of the proximal phalanx, through which it extends the MP joint. The insertions of the interossei and lumbricals enter into the extensor hood as the lateral bands. These lateral bands insert distally and dorsally to the axis of the PIP joint, and it is through this distal insertion that the intrinsic muscles (the interossei and lumbricals) are flexors of the MP joints and yet extensors of the IP joints. The extensor hood inserts to the base of the middle phalanx, which is termed the central slip, and finally proceeds on to the base of the distal phalanx, where it inserts through the terminal slip, thus extending the distal interphalangeal (DIP) joint (Fig. 70-4).

FIGURE 70-4 Extensor mechanism of the fingers. A, Lateral view. B, Dorsal view.

The extrinsic flexor muscles are located on the volar aspect of the forearm and are arranged in three layers. The superficial layer comprises four muscles—pronator teres (PT), flexor carpi radialis (FCR), flexor carpi ulnaris (FCU), and palmaris longus (PL). The PL muscle may be absent in as many as 10% to 12% of individuals. These muscles originate from the medial humeral epicondyle in the proximal forearm and function to flex the wrist and pronate the forearm. The intermediate layer consists of the flexor digitorum superficialis (FDS), which allows independent flexion of the proximal interphalangeal (PIP) joints of the fingers. In the deep layer, there are three muscles: the FPL, which flexes the IP joint to the thumb; the FDP, which flexes the DIP joints of the fingers; and a distal quadrangular muscle that spans between the radius and ulna termed the pronator quadratus, which helps in pronation of the forearm (Table 70-3).

Table 70-3 Extrinsic Muscles of the Volar Forearm

MUSCLE	INNERVATION*	FUNCTION
Pronator teres (PT)	Median	Pronation
Flexor carpi radialis (FCR)	Median	Flexion and radial deviation of the wrist
Palmaris longus (PL)	Median	Flexion of the wrist
Flexor carpi ulnaris (FCU)	Ulnar	Flexion and ulnar deviation of the wrist
Flexor digitorum superficialis (FDS)	Median	Flexion of the proximal interphalangeal (PIP) joint
Flexor digitorum profundus (FDP)	Median and ulnar	Flexion of the distal interphalangeal (DIP) joint
Pronator quadratus	Median	Pronation
Flexor pollicis longus (FPL)	Median	Flexion of the thumb

* All muscles of the volar forearm are innervated by the median nerve and its branches except the two ulnar digits of the FDP and FCU, which are innervated by the ulnar nerve.

Nerve supply to the hand is by three nerves, the median, ulnar, and radial nerves. A knowledge of the surface anatomy of nerves helps when evaluating specific lacerating injuries (Fig. 70-5). The ulnar attachment to the flexor retinaculum is to the pisiform and hook of the hamate, and the radial attachment is to the scaphoid and ridge of the trapezium. The median nerve passes through the carpal tunnel between these landmarks. It gives sensation to the thumb, index finger, middle finger, and radial half of the ring finger. The palmar cutaneous branch of the median nerve originates from its radial side 5 to 6 cm proximal to the wrist, providing sensation to the palmar triangle. The ulnar nerve travels to the radial side of the pisiform and passes to the ulnar side of the hook of the hamate in its passage through Guyon’s canal. It gives sensation to the little finger and ulnar half of the ring finger; the dorsal branch of the ulnar nerve (arising proximal to the wrist and curving dorsally around the head of the ulna) supplies the same digits on their dorsal aspects. The superficial radial sensory nerve emerges from under the brachioradialis in the distal forearm, dividing into two or three branches proximal to the radial styloid, which then proceed in a subcutaneous course across the anatomic snuffbox, innervating the skin of the dorsum of the first web space. The number of fingers served by each nerve is variable. However, as an absolute rule, the palmar surfaces of the index and little fingers are always served by the median and ulnar nerves, respectively.

FIGURE 70-5 Surface anatomy of median (red) and ulnar (black) nerves. H, Hook of hamate; P, pisiform; S, scaphoid; T, trapezium.

With regard to the motor supply of these nerves, the ulnar nerve supplies the hypothenar muscles, interossei, ulnar two lumbricals, adductor pollicis, and deep head of the flexor pollicis brevis. The median nerve supplies the abductor pollicis brevis, opponens pollicis, radial two lumbricals, and superficial head of the flexor pollicis brevis. In summary, the median nerve thus supplies all the extrinsic digit flexors and wrist flexors (except the FDP to the ring and little fingers and the FCU, which are supplied by the ulnar nerve) and all the thumb intrinsic muscles (except the AP, innervated by the ulnar nerve). The ulnar nerve supplies all the interossei, all the lumbricals (except the radial two, supplied by the median nerve), and the adductor of the thumb. The radial nerve innervates all of the wrist, finger, and thumb extrinsic long extensors.

Examination And Diagnosis

Evaluation

Basic instruments used in hand examination are shown in Figure 70-6. Examination of the resting posture of the hand can provide valuable information; for example, if a finger flexor tendon is severed, that affected finger does not assume its normal resting position in line with the natural flexion cascade of the adjacent digits (Fig. 70-7). Extensor tendon injuries may be indicated by a droop at the affected joint. A clawed posture of the little and ring fingers may be characteristic of an ulnar nerve injury (Fig. 70-8). Absence of sweating at the fingertips may imply a nerve injury in that particular distribution. Swelling and erythema may indicate a hand infection, and a purulent flexor tenosynovitis always results in a flexed posture of the digits. Rotational and angular digital deformities may occur when there are underlying fractures.

FIGURE 70-6 Basic instruments used in hand examination include a tuning fork, pinch meter, grip dynamometer, two-point discriminator (paperclip also suffices), goniometer, and patella hammer.

FIGURE 70-7 A, B, Natural finger flexion cascade of the hand in repose. Note the fingertips pointing to the distal pole of the scaphoid. C, With flexor tendon injury, the affected digit does not adopt this resting flexed posture. D, E, Spiral finger fractures produce a rotational deformity, which is also noted as an interruption in the finger flexion cascade.

FIGURE 70-8 A, Marked atrophy in the first web space dorsal interosseous muscle is noted with ulnar nerve palsy, with clawing of the little and ring fingers. B, The little finger assumes an abducted position and cannot be adducted to the adjacent fingers (Wartenberg’s sign). C, Because thumb adduction is weak, attempts to grasp a piece of paper between the adducted thumb and index finger produce compensatory thumb IP joint flexion (Froment’s sign).

Neurovascular Examination

The Allen test confirms patency of the ulnar and radial arteries. Two-point sensory discrimination is the most sensitive method for testing for sensory loss and is easily done by using a bent paperclip (Fig. 70-9). The paperclip ends are set to a distance of approximately 5 mm apart for fingertip pulp sensory testing. The points are aligned along the axis of the finger. If this test is not reproducible because of an uncooperative patient, suspicion of a nerve injury can be confirmed by the tactile adherence test, in which a plastic pen is passed back and forth gently across the pulp on either side of each finger. Adhesion, because of the presence of sweat, is shown by slight but definite movement of the finger being examined (anesthetized finger pulp will not sweat).

FIGURE 70-9 Two-point discrimination on the fingertip can be tested with a bent paperclip, with the tips of the paperclips set specific distances apart.

There are two muscle tests that may provide the examiner with an absolute diagnosis of median or ulnar nerve injury. The motor function of the abductor pollicis brevis tests the median nerve. With the hand flat and facing palm up, the patient is asked to use his or her thumb to touch the examiner’s finger, which is held directly over the thenar eminence (Fig. 70-10). The FDM muscle function will test the motor supply of the ulnar nerve. In the same hand position, the patient raises her or his little finger vertically, flexing the MP joint to a 90-degree angle, with the IP joint held straight. Tests for radial nerve function and its branches require wrist extension, thumb extension, and finger extension at the MP joint.

FIGURE 70-10 Motor innervation of muscles of the hand. A, Thumb abduction tests median motor nerve function. B, Little finger flexion at the metacarpophalangeal joint with simultaneous IP joint extension tests ulnar motor nerve function.

Musculoskeletal Examination

The integrity of the tendons is individually tested (Fig. 70-11). Flexion at distal joints of the thumb and fingers confirms that the FPL and FDP, respectively, are intact. Testing of FDS tendons is more complex. It is not possible to flex the DIP joints independently of one another because of a common origin of the FDP tendons. Thus, the other fingers are fixed in extension by the examiner and the patient is asked to flex the remaining digits. Movement is produced by the FDS and occurs at the PIP joint. In approximately one third of patients, the FDS cannot produce little finger flexion. In 50% of these, in turn, there is a common origin with the ring finger, so flexion will occur if the ring finger is permitted to flex simultaneously. More uncommonly, there is no profundus tendon to the little finger and the superficialis inserts into the middle and distal phalanges. The long and short extensors (EPL and EPB) and long abductor of the thumb are tested by asking the patient to extend his or her thumb against resistance, whereas these tendons are individually palpated. Long extensors of the fingers are tested by asking the patient to extend them against resistance applied to the dorsum of the proximal phalanx.

FIGURE 70-11 Individual clinical testing of the FDP (A), FDS (B), FPL (C), finger extensors (D), and thumb extensors (E).

Special Investigations

Radiographs are necessary in almost every case. These help in the diagnosis and evaluation of fractures and also in the investigation of foreign bodies. Multiple radiographic views of the affected part are required to define the precise pathology or fracture pattern. Glass is often seen on plain radiographs and, if not seen but suspected, may be visualized by computed tomography (CT) or magnetic resonance imaging (MRI). If plastic is painted, it may be seen on routine radiographs; it is generally poorly visualized with CT but can be clearly seen with MRI. Wooden foreign bodies may be seen by CT or MRI, but not by routine radiography.

Various stress radiographic views and cineradiography may be useful for demonstrating dynamic wrist instability patterns, especially scapholunate separation. Arthrography may detect ligamentous tears by extravasation of contrast material between the radiocarpal, distal radioulnar, and midcarpal joints. This is best combined with MRI, especially for the detection of triangular fibrocartilage tears at the ulnocarpal joint. Radionuclide bone scanning may help diagnose osteomyelitis but, in the hand, a false-positive result may occur because of the close proximity of soft tissue infections to the bones. Occult wrist fractures may be localized by increased radionuclide uptake, but a false-positive result when evaluating for a fracture may also occur with ligamentous injuries. CT is a helpful modality for diagnosing suspected carpal fractures, (e.g., a scaphoid fracture that may not be seen on a routine x-ray), although most prefer MRI.

Wrist arthroscopy is useful as a diagnostic and therapeutic modality for a number of wrist problems, especially for disorders of the triangular fibrocartilage. Minimally invasive surgery with arthroscopic guidance has added a new dimension to the treatment of acute wrist disorders such as scaphoid and distal radius intra-articular fractures.

Patients with ischemic problems often require noninvasive vascular studies. Doppler pressure measurements help localize the site of a vascular lesion. Angiography in the upper extremity is always carried out in the presence of a vasodilator (e.g., tolazoline [Priscoline], nitroglycerin) or an axillary block to differentiate apparent vessel occlusion from vasospasm. Subtraction radiographs with magnification help improve the detail and definition of the vascular study, especially in the distal forearm and hand.

Principles Of Treatment

In the case of injuries, treatment is directed at the specific structures damaged—skeletal, tendon, nerve, vessel, integument.^1,² In emergency situations, the goals of treatment are to maintain or restore distal circulation, obtain a healed wound, preserve motion, and retain distal sensation. Stable skeletal architecture is established in the primary phase of care because skeletal stability is essential for effective motion and function of the extremity. This also reestablishes skeletal length, straightens deformities, and corrects the compression or kinking of nerves and vessels. Arteries are also repaired in the acute phase of treatment to maintain distal tissue viability. Also, extrinsic compression on arteries must be released emergently, such as with compartment pressure problems. In clean-cut injuries, tendons can be repaired primarily. In situations in which there is a chance that tendon adhesions may form, such as when there are associated fractures, it is nonetheless better to repair tendons primarily with preservation of their length and, if necessary at a later date, to perform tenolysis. However, when there are open and contaminated wounds or a severe crushing injury, it is best to delay repair of tendon and nerve injuries.

In clean-cut sharp wounds, primary nerve repair lessens the possibility of nerve end retraction and therefore the need for later nerve grafting. However, primary nerve repair must not be performed in situations in which there is contusion of the nerve (e.g., gunshot wounds, power saw injuries, blunt crushing trauma) because the extent of proximal axonal injury may not be immediately evident. If nerve repair is performed before this is apparent, it may result in abnormal nerve ends being reattached, negating the chance for functional return.

In severe soft tissue injuries, wound closure may not be possible immediately. Initial open treatment of the wound is directed to prevent an infection and protect critical deep structures by proper dressing and wound management (Fig. 70-12). Adequate débridement is essential, but appropriate soft tissue coverage must be achieved as soon as possible thereafter. The sooner the soft tissue coverage can be achieved, the less likely there will be a secondary deformity caused by fibrosis and joint contractures. The more rapidly hand therapy can be started, the better the chance for maximizing functional return. The treatment regimen must consist of débridement, rigid skeletal fixation, and early soft tissue resurfacing, possibly even requiring microvascular soft tissue reconstruction, followed by protected range-of-motion exercises as soon as possible. It has been shown that early soft tissue reconstruction results in improved function, decreased morbidity, and shortened hospital stay.

FIGURE 70-12 A, Gunshot wound of forearm showing extensive soft tissue injury. B, Initial radiograph. C, Microvascular reconstruction using a bilobed latissimus dorsi musculocutaneous flap was done in association with fracture fixation. D, Long-term follow-up of reconstructed forearm that also required sural nerve grafting to a segmental injury of the median nerve.

Appropriate treatment of upper extremity problems requires a thorough knowledge of local and regional anesthesia, use of a tourniquet to provide a bloodless field, correct placement of incisions to minimize later scar contracture, and appropriate use of dressings and splints to reduce edema and maintain a functional position. Above all, a clear knowledge of the unique anatomy of the hand and upper extremity not only aids in obtaining an accurate clinical diagnosis, but also enables the safe performance of surgery.

Anesthesia

The choice of general, regional (e.g., IV Bier block, brachial plexus block that might be a supraclavicular or axillary block), or local anesthesia is governed by the extent and length of the operation. An upper arm or forearm tourniquet can be used in the unanesthetized extremity with only local anesthetic field infiltration or digital block for 30 to 45 minutes in a relaxed, cooperative patient provided that the arm is well exsanguinated. After this time, tourniquet pain will not permit more extensive local anesthetic procedures. If one has to operate in other areas, such as for harvesting of bone, nerve, tendon, or skin graft, or if more extensive surgical procedures are planned, general anesthesia will be required.

A digital block or median, ulnar, or radial wrist nerve block may be useful, especially for more limited emergency room procedures (Fig. 70-13). Digital nerve blocks usually do not include epinephrine, which could lead to vasospasm, but evidence has indicated the safety of distal blocks using an epinephrine solution. A maximum safe dose of lidocaine is 4 mg/kg.

FIGURE 70-13 A, Median nerve block is done at the wrist, where the median nerve is superficial to all the flexor tendons in the carpal tunnel. B, At the wrist, when a median nerve block is performed, the needle is directed between the PL and FCR tendons. C, Ulnar nerve block at the wrist is done by passing the injecting needle around the ulnar deep aspect of the FCU tendon just proximal to the pisiform. Intravascular injection into the immediately adjacent ulnar artery is avoided by first aspirating before injection. D, Dorsal branches of the ulnar nerve and superficial sensory radial nerve are anesthetized by raising a broad weal of local anesthetic across the dorsum of the wrist. E, A dorsal approach to the finger can be used for digital nerve block.

Tourniquet Application

The tourniquet is used to provide a bloodless field so that clear visualization of all structures in the operative field is obtained. Penrose drains, rolled rubber glove fingers, or commercially available tourniquets can be used on digits. Great care must be taken when using any constrictive device on digits because narrow bands cause direct injury to underlying nerves and digital vessels. With the use of an arm tourniquet, the skin beneath the cuff must be protected with several wraps of cast padding. During skin preparation, this area must be kept dry to prevent blistering of the skin under an inflated cuff over moist padding. The cuff selected needs to be as wide as the diameter of the arm. Standard pressures used are 100 to 150 mm Hg higher than systolic blood pressure. The cuff is deflated every 2 hours for 15 to 20 minutes (5 minutes of reperfusion for every 30 minutes of tourniquet time) to revascularize distal tissues and relieve pressure on nerves locally before reinflating the cuff for more extensive procedures.³ Exsanguination of the extremities is performed by wrapping the extremity with a Martin’s bandage in all cases, except those involving infection or tumors. In these latter cases, because of the possibility of embolization by mechanical pressure, exsanguination by bandage wrapping needs to be avoided. Simple elevation of the extremity for a few minutes before tourniquet inflation suffices.¹

Incisions

Incisions are of the Bruner zigzag or midaxial type, or combinations of these, to avoid longitudinal motion-restricting scars that cross palmar flexion creases (Fig. 70-14). The marginal edge of a skin graft with healthy skin is also a potential scar line, so the margin of the skin graft is designed to be in these same lines to prevent contractures across flexion creases. Palmar incisions follow the pattern of skin creases. Dorsal incisions on the fingers and wrist and incisions on the forearm may follow longitudinal straight lines.

FIGURE 70-14 Incisions used on the palmar surface of the hand must respect the creases. These may be zigzag Brunner incisions or midaxial incisions of the digits.

Dressings and Splints

The purposes of dressings are to protect wounds, absorb drainage, and help splint repaired structures. The first layer consists of a nonadherent dressing and may contain an antibiotic. The next layer is soft and bulky and is usually followed by a firmer, more conforming external wrap. Conforming compression is useful, but constriction is harmful. Splints are made to protect only the part necessary to be immobilized and must not prevent motion in the remainder of the extremity. Often, patients keep the injured, operated, or infected hand in a flexed wrist position, which automatically causes the MP joints to extend, thereby placing the collateral ligaments in their shortest lengths. Edema fluid collects dorsally and the resulting dorsal hand swelling causes stiff joints. Thus, a splint that keeps the hand in the protected position extends the wrist 40 to 50 degrees, maintaining the MP joints at 70 degrees of flexion and the IP joints in a neutral position (Fig. 70-15). Postoperative hand elevation is essential to reduce edema.

FIGURE 70-15 Application of a splint and dressings to demonstrate the safe or protected position of the wrist, hand, and digits. The thumb is palmar-abducted.

Trauma

Emergency Control of Bleeding

Bleeding in the extremity can often be profuse when first encountered. A reasoned and controlled assessment of the situation almost invariably results in the control of bleeding and minimization of further blood loss, and facilitates necessary stabilization of the patient and appropriate assessment of the upper limb injury. Bleeding in the upper extremity often results when vessels lie in a superficial location, such as at the wrist. Bleeding can originate from superficial veins that bleed more profusely when poorly applied dressings result in venous engorgement. The thicker media of transected arterial walls contract strongly, resulting in hemostasis. Partially lacerated arteries continue to bleed profusely.

Elevation and accurately placed point pressure over bleeding points result in hemostatic control in almost all cases. Brief use of tourniquets may be a useful adjunct to allow temporary control of blood loss in the emergency room (ER). Poorly applied dressings may be removed, bleeding points identified, point pressure dressings applied, and the hand elevated. This should take no more than 5 to 10 minutes. Extended tourniquet application results in hyperemic bleeding on deflation and subsequently hinders the surgeon. Tourniquets should not be applied for any significant period of time before definitive repair in the operating room (OR), except for control of torrential hemorrhage caused by major amputation in the field. Misguided attempts to control upper extremity bleeding with clamps, ligatures, and cauterization in the ER frequently result in additional avoidable injury to adjacent uninjured structures and to vessels that may need to be repaired for adequate limb perfusion. Fracture reduction and stabilization will improve distal perfusion and facilitate hemorrhage control by restoring the limb to its correct anatomic alignment.

Lacerations, Fingertip, and Complex Soft Tissue Injuries

Although it is tempting to look within a wound to determine whether any tendon or nerve injuries exist, the same information can be obtained by careful physical examination without further violating a potential operative field and causing the patient extreme discomfort. A combination of knowledge of anatomy, presence of sensory or motor deficits, and presence or absence of radial or ulnar pulses can narrow the differential diagnosis of injured structures to a minimum. Control of bleeding is attempted by direct pressure with dressings and not by blind clamping of vessels because vital structures may be inadvertently injured in the depths of the wound. However, a tourniquet may be used if the initial pressure measures fail. Tourniquets are generally not used initially because the entire limb will be ischemic during patient transport. If the trauma has caused complete obliteration of anatomy, incisions can be extended into nonviolated areas in which control of bleeding vessels and delineation of injured tendons and nerves may be easier, using the guidelines presented earlier for extremity incisions.

All patients who present with extremity injuries undergo radiography. Fractures of the distal phalanx are among the more commonly encountered hand fractures.⁴ A distal phalangeal fracture is appropriately splinted, reduced to improve alignment, or occasionally fixated internally if the fracture is unstable. Internal fixation is usually provided by simply placing a longitudinal 0.028-inch Kirschner wire. Appropriate antibiotics are administered because, technically, these are open fractures.

The least severe injury of the dorsum of the fingertip is a nail bed hematoma. When seen early, the hematoma can be decompressed by perforating the nail plate after the administration of a digital local anesthetic block. Fingertip and nail bed injuries can be managed with digital block anesthesia and a Penrose drain at the base of the finger as a tourniquet. After the nail plate has been stripped, simple gentle removal of the nail to examine the underlying nail bed is done and suture repair of the nail bed is performed using loupe magnification and a 6-0 catgut suture. Once the nail bed has been repaired, it is best to place the thoroughly cleansed nail back under the nailfold, where it serves as a rigid splint for an underlying distal phalangeal fracture and prevents adhesions from forming between the adjacent surfaces of the nailfold, which might lead to an unsightly split nail deformity. If there is a piece of nail bed missing, the undersurface of the avulsed nail plate is examined. Frequently, the missing piece may still be adherent to the nail, and it can be gently removed and replaced as a nail bed graft. Some fingertip injuries may be so severe that amputation revision may be the most sensible and functional solution.

Volar fingertip injuries range from simple to more complex. Multiple digits may be involved, such as with lawnmower injuries. If bone is not exposed and a soft tissue defect of the finger pulp is smaller than 1 cm, the wound is best left open and managed with dressings. Such an injury will heal with excellent functional and cosmetic results. Larger soft tissue defects of the fingertip pulp are more appropriately treated with a small, full-thickness skin graft. However, if bone is exposed and the soft tissue wound is larger, flap coverage or revision of amputation by trimming back exposed bone to obtain soft tissue coverage should be considered. In a dorsally angulated fingertip amputation, soft tissue coverage can be achieved by a neurovascular V-Y advancement flap. If the soft tissue loss is angulated in a more volar direction, a cross-finger flap, adjacent finger digital island flap, or homodigital flap may be performed (Figs. 70-16 to 70-18).

FIGURE 70-16 A, B, Volar angulated fingertip injury with loss of pulp pad and bone exposed was treated with a traditional cross-finger flap from the dorsum of the adjacent finger. C, Excellent healing is seen in the long term after flap division.

FIGURE 70-17 A-D, More recent understanding of the vascular skin territories of the finger and hand enable intrinsic flap coverage of fingertip injuries and avoid the cumbersome tethering of adjacent fingers, as is done with cross-finger flaps. In this patient, a distally based turnover vascular island flap reconstructs an avulsed fingertip. The reverse-flow perforating vessels at the proximal IP joint cross from the opposite side to nourish this flap.

FIGURE 70-18 A-C, The first dorsal metacarpal artery flap is a vascularized island flap that is transposed from the dorsoradial aspect of the index finger to the distal pulp of the thumb following a crushing injury.

Tendon Injuries

Flexor Tendons

Flexor tendon injuries usually result from lacerations or puncture wounds on the palmar surface of the hand, although flexor tendons can be avulsed from their distal bony insertions by sudden violent contractions. These are best treated by a surgeon experienced in the treatment of such injuries. Flexor tendon injuries are divided into five zones (Fig. 70-19). In zones 1, 2, and 4, each tendon is surrounded by a synovial sheath and contained within a semirigid fibro-osseous canal, either within the flexor tendon sheath of the digit or carpal tunnel. In the other zones, the flexor tendons are surrounded by loose areolar (paratenon) tissue. Those parts devoid of a fibrous sheath usually heal very well because of the good blood supply from the paratenon. Tendons in the carpal tunnel (zone 4) have their rich blood supply provided by the mesotenon; however, zones 1 and 2 have a precarious blood supply through the vincula; complementary nutritional support is provided by the synovial fluid in these latter two zones. For tendon gliding to occur, the mesotenon has disappeared in the digital flexor sheath except at the sites of the vincula that carry the vessels from the periosteum to the tendons (Fig. 70-20). Tendon zones to the thumb are T1 through T3.

FIGURE 70-19 Zones of flexor tendon injuries on the fingers, thumb, and hand.

FIGURE 70-20 Complex arrangement of FDS and FDP tendons in the flexor sheath of the fingers. Blood supply to the tendons travels through the vincula from the dorsal aspects of the tendons.

Primary tendon repair undertaken within a few hours of injury is generally reserved for cleanly cut tendons. Delayed primary repair is performed from several hours up to 10 days after injury and is indicated for tidy, but potentially contaminated, wounds to allow for prophylaxis against infection before the tendon repair. Relative contraindications to immediate tendon repair include the following:

1 Injuries more than 12 hours old

2 Crush wounds with poor skin coverage

3 Contaminated wounds, especially human bites

4 Tendon loss more than 1 cm

5 Injury at multiple sites along the tendon

6 Destruction of the pulley system

After 4 weeks, a later secondary repair is generally not possible because of retraction of the musculotendinous unit so that reapproximation of the tendon ends produces undesirable joint flexion. In this situation, tendon graft repair may be required. The surgeon’s endeavors are directed at avoiding the four major complications that interfere with smooth gliding and the integrated action of tendons—adhesions, attenuation of the repair, repair rupture, and joint and soft tissue contractures. Prerequisites for tendon repair are aseptic conditions in the OR, with good lighting, good instruments, adequate anesthesia, and loupe magnification. A well-performed technical operation can be futile without proper postoperative hand therapy, splinting, and excellent patient compliance.⁵

Appropriate treatment of partial flexor tendon injuries is necessary to produce a smooth juncture at the injury site. Prevention of complications requires exploration of all wounds likely to cause partial flexor tendon lacerations. A partial tendon injury of 50% or less is treated by simple trimming of the lacerated portion. Those injuries greater than 50% are repaired. Failure to diagnose a partial flexor tendon laceration at the time of primary repair may lead to delayed tendon rupture, entrapment between the tendon laceration and the laceration in the flexor sheath, or trigger finger.

Zone 2 flexor tendon injuries require special attention. This zone is also called Bunnell’s no man’s land. There are three tendons—the profundus and two slips of superficialis—that traverse zone 2 and they constantly interchange their mutual spatial relationships. Tendon injury in this region requires opening the existing laceration in the flexor tendon sheath by making a longitudinal trap door so that a flap of tendon sheath can be elevated. Care must be taken to avoid excising excessive portions of the flexor tendon sheath because bowstringing may result in ineffective finger flexion, although portions can be vented or excised to facilitate repair or prevent postoperative triggering. Total preservation of the A2 and A4 pulleys, previously thought to be essential, is no longer believed to be critical to success. One can excise up to 50% of the A2 and A4 pulleys without creating unnecessary tendon bowstringing if this is thought to be prudent to avoid the tendon repair impinging under the pulley.⁶ It has also been shown that one can incise the full length of the A4 pulley (but not excise it), without any biomechanical consequences.⁷ This is especially helpful when the zone 2 repair occurs proximate to the A4 pulley, the narrowest part of the flexor tendon sheath. Finally, wide awake anesthesia, which is local anesthetic infiltration using a solution of xylocaine with epinephrine, enables flexor tendon repair without the use of a tourniquet and ensures full patient cooperation during the procedure.⁸ This was previously thought to be unwise, but this has been proven to be unsubstantiated. Thus, one can determine intraoperatively that there is full flexor tendon excursion at the repair site without impingement under the pulleys as the patient flexes and extends his or her fingers before the skin incision is finally closed. All these novel and revolutionary concepts challenge previously accepted dogma with regard to zone 2 flexor tendon repairs and the significance of the various annular pulleys. It is often difficult to repair profundus and superficialis tendons if they are injured in zone 2. Nonetheless, both can be repaired because resection of the superficialis reduces overall grip strength, predisposes to a recurvatum and swan neck deformity at the PIP joint, and damages the vincula supply to the profundus.

Usually, skin wounds have to be extended proximally and distally in a zigzag fashion to display the retracted divided tendon ends. Tendon ends are handled with a fine-toothed forceps and the tendon surface is never touched. The wrist is flexed and a small Keith needle is passed transversely through the proximal tendon, approximately 2 cm from the end, transfixing it to the skin and tendon sheath. In this way, immobilization of the tendon end facilitates a tension-free repair. Ragged tendon ends may be squared off sharply, but no more than 1 cm is resected or permanent finger contracture will result. The tendon ends are brought together by a single tension-holding, locking, core suture. Various locking core suture techniques have been described, but usually a modified Kessler-type suture is placed. A specifically placed locking loop increases the ultimate tensile strength of the tendon repair by 10% to 50% compared with a simple mattress suture. If this is not done, tension on the suture line can open up the repair, increasing the propensity for tendon gapping at the repair site. The ideal suture material for tendon repairs has not been found. A 4-0 coated polyester or braided nylon suture is the best material for the core suture. Increasing the number of suture strands that cross the tendon repair site and obtaining suture bites of at least 0.7 cm will increase the overall tensile strength of the actual repair.⁹ However, the more suture strands that are added, the greater will be the friction and edema within the flexor tendon sheath. A four- or six-stranded core repair appears to provide optimum repair strength and does not increases stiffness and friction at the repair site excessively. Some perform a four-stranded core repair by simply using a double-stranded type of suture material, whereas others place a second core suture with a single-stranded material. A four-stranded core repair permits a light, protected, composite grip for the duration of postoperative healing. Also, a running circumferential epitenon suture repair is also placed (Fig. 70-21). This not only helps smooth the repair but also adds to the ultimate tensile strength at the repair site and reduces gap formation. A peripheral 6-0 nylon suture serves this purpose.

FIGURE 70-21 Technique of performing a four-strand flexor tendon core suture repair is demonstrated in association with a peripheral running suture.

The forces generated on FDP flexor tendons during passive finger flexion are 600 g and during active finger flexion are 2000 g; with strong active finger flexion, they are 8000 g. However, after tendon repair, the effects of wound healing, changes in elasticity, and added friction between the flexor tendons and their surrounding tissues will affect the overall work of flexion. There will be added frictional forces caused by edema, the presence of suture material, and the pulley system. The estimated work of flexion (resistance) increases by a factor of 50% after tendon repair. Thus, the estimated forces on repaired tendons, with 50% added for the work of flexion, are 900 g for passive finger flexion, 3000 g for active finger flexion, and 12,000 g for strong active flexion. The ultimate tensile strengths of various repairs are 2600 g for two-stranded and simple epitendinous repair, 4600 g for four-stranded and simple epitendinous repair, and 6800 g for six-stranded and simple epitendinous repair. The strength of the initial tendon repair decreases by approximately 25% during the first 3 weeks and then steadily increased thereafter to 6 weeks. Hence, if one is to undertake a postoperative active finger flexion protocol, then at least a four- or six-stranded core suture tendon repair is needed.¹⁰

Zone 1 flexor tendon injury may be caused by a penetrating injury. However, closed-traction injury may also cause profundus tendon avulsion, which most frequently involves the ring or middle finger. In the repair of a zone 1 injury, a pullout suture is necessary if the distal tendon length is insufficient to repair the tendon securely (Fig. 70-22), although suture bone anchors have facilitated this mode of tendon repair into bone at the base of the distal phalanx.

FIGURE 70-22 Zone 1 flexor tendon repair to reattach tendon to bone.

Postoperatively, hand elevation is important to reduce edema. The wrist is placed in approximately 20 degrees of flexion and the MP joint at approximately 60 to 70 degrees of flexion. The splint is molded against the fingers, with the IP joints fully extended. A system of rubber band dynamic traction may be used following the repair of flexor tendons in zone 2, with good results obtained in more than 80% of cases. Differential excursion between the two digital flexors is dramatically increased by a synergistic splint that allows for wrist extension and finger flexion. This position of wrist extension and MP joint flexion produces the least tension on a repaired flexor tendon during active digital flexion; thus, we have come to use the flexor hinge brace technique and the so-called place-and-hold protocol (Fig. 70-23). Of all the postoperative flexor tendon protocols, this enables the greatest overall tendon excursion of each of the FDS and FDP tendons and the most significant differential tendon gliding between the FDS and FDP repair sites, which theoretically would then reduce the risk of adhesion formation between the two tendons. A tenodesis brace with a wrist hinge is fabricated to allow for full wrist flexion, wrist extension of 30 degrees, and maintenance of MP joint flexion of at least 60 degrees. After composite passive digital flexion, the wrist is extended and passive finger flexion is maintained. The patient actively maintains digital flexion and holds that position for approximately 5 seconds. The patient is instructed to use the lightest muscle power necessary to maintain digital flexion. Wrist flexion and finger extension follow. This protected motion postoperative protocol is continued for 6 weeks.

FIGURE 70-23 Flexor hinge brace with place-and-hold technique of finger mobilization is one of the preferred methods for postoperative rehabilitation after flexor tendon repair.

Extensor Tendons

Proper diagnosis of extensor tendon injuries requires full knowledge of the relatively complex anatomy of the extensor mechanism of the dorsum of the finger. The subcutaneous location of extensor tendons makes them susceptible to crush, laceration, and avulsion injuries. The presence of juncturae tendinum prevents proximal retraction of the EDC tendons. Extensor tendon injuries have been divided into nine zones, which ascend numerically from the dorsum of the DIP joints to the forearm. The odd-numbered zones begin at the DIP joint and are located over the joints; the even-numbered zones are located between the joints.

Extensor tendons are thinner than flexor tendons and, over the dorsum of the digits, are spread out to form the extensor hood. It may occasionally be possible to use conventional tendon repair techniques in the proximal parts of the tendons, but this is usually not the case in the extensor hood region. Here, horizontal mattress sutures or figure-of-eight mattress sutures may be needed. All lacerations are repaired if 50% or more of the tendon is divided.

Extensor tendon avulsions are most likely to occur at the DIP joint from a jamming type of injury that results in a mallet finger deformity (Fig. 70-24). If a bone fragment representing 50% or more of the articular surface is involved, or if there is volar subluxation of the DIP joint, an open reduction with internal fixation is performed. If there is a tendon rupture only or a small piece of bone is avulsed with the tendon, good results can be obtained by 6 weeks of continuous splinting with the DIP joint in extension (Fig. 70-25). After this period of splinting, the DIP joint is further protected during sleep for 2 more weeks.

FIGURE 70-24 A-C, Mallet fracture with avulsed bony fragment involving more than 50% of the articular surface with volar subluxation of the distal phalanx. The bony fragment is reapproximated with a tie-over volar suture and a longitudinal pin traversing the DIP joint.

FIGURE 70-25 A, Prefabricated stack splint may be used for the closed treatment of a mallet finger. B, A simple dorsal aluminum splint may serve equally well for mallet finger treatment. C, D, Dorsal splinting across the PIP joint enables closed treatment of a boutonniere injury. The DIP is left free for flexion and extension.

Closed tears through the triangular ligament may be caused by PIP joint subluxation or a jamming type of injury that results in a boutonniere deformity. The central slip attachment at the base of the middle phalanx is disrupted, so that extension of that joint is altered. The lateral bands lose their support dorsal to the PIP joint axis and slip volar and become flexors at the PIP joint and extensors of the DIP joint. The consequent deformity is one of flexion at the PIP joint and hyperextension at the DIP joint. Within 6 weeks of injury, these can be treated satisfactorily by extension splinting at the PIP joint, maintaining the DIP joint free for active flexion and extension (see Fig. 70-25). If there is an open laceration to the central slip mechanism and adjacent triangular ligament, direct suture repair or reinsertion into bone by means of bone anchor minisutures is performed, followed by the same postoperative protocol.

Extensor tendon injuries proximal to the PIP joint result in a drop finger (Fig. 70-26). These are repaired and splinted for 4 weeks. Common extensor tendon injuries over the dorsum of the hand and at the wrist must be repaired and then treated postoperatively by various different controlled motion protocols. One is a dynamic rubber band extension outrigger brace or use of a relative motion splint, in which the affected digit is kept at a more dorsal pitch to the adjacent fingers, thus relaxing the repaired tendon. This latter splint causes minimal interference with daily activities during rehabilitation (Fig. 70-27).¹¹