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.

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:

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

FIGURE 70-26 Extensor tendon injuries on the dorsum of the finger. Injury at the distal insertion causes a mallet finger and, at the central slip over the PIP joint, causes a boutonniere deformity. Proximal to the PIP joint, over the proximal phalanx, injury results in a drop finger.

FIGURE 70-27 A, B, Extension outrigger dynamic splint commonly used for extensor tendon injuries postoperatively (extension and flexion views). C, D, Relative motion splint has the advantage of being low profile and causes minimal interference with daily activities and yet provides protection to the freshly repaired extensor tendon.

Nerve Transfers

If there may be a long distance between the site of nerve injury and distal muscle target, primary nerve repair may be fruitless, because muscle degeneration would have occurred by the time distal neural growth occurs. Muscle recovery is unlikely after an 18-month lapse. Thus, if nerve growth occurs at the rate of approximately 1 mm/day, a proximal motor nerve lesion more than 540 mm proximal to the hand will be doomed to failure. Hence, for proximal arm nerve and brachial plexus injuries, nerve transfers may result in a nerve repair that is closer to the muscle target. The donor nerve must be chosen so as to minimize morbidity from loss of the donor nerve. The donor nerve must be closely related to the denervated muscle so that the repair is performed much closer to the muscle target. Nerve transfers have revolutionized the repair of proximal nerve injuries so that distal muscle atrophy is minimized. For example, the classic Oberlin transfer uses part of the ulnar nerve (usually a single fascicle) for transfer to the musculocutaneous nerve and to the brachialis in the upper arm to restore elbow flexion.¹³ It is technically easy, quick, and effective. No significant motor or sensory deficits result in the territory of the ulnar nerve. This technique has become popular and is indicated for C5-6 brachial plexus lesions when C8-T1 is intact. It can also be used to neurotize a functioning free muscle transfer that may be required if the native muscles have already sustained atrophy because of prolonged denervation.