Introduction
For more than a century, flexor tendon repairs have presented challenges to hand surgeons and have aroused enormous enthusiasm among clinicians and investigators. In the early and middle 20th century, secondary tendon grafting dominated the repair of digital flexor tendons. During this period, tendon implants were developed for staged tendon reconstruction. However, as the practice of primary repairs prevailed in recent decades, the number of patients indicated for secondary tendon grafting or staged reconstruction decreased drastically.
From the 1960s and 1970s, primary repair in the digits started to replace the earlier practice of tendon grafting in zone 2 and gradually became mainstream practice. In the most recent two decades, there have been significantly fewer problems in flexor tendon surgery than there were half a century ago. In almost all surgical units around the world, primary repair is popular, and outcomes are much better than they were decades ago. Excellent outcomes have been reported in recent publications. In most patients, the results of direct repair of tendon lacerations in zone 2 are no longer unfavorable. In fact, outcomes of primary repair in zone 2 can be as good as in other areas, although there is greater need for surgical expertise in tendon repair in this area than in other regions of the flexor tendons.
Zone 2 is the most complicated with respect to anatomy and demanding surgical techniques. In repairing tendons in zone 2, surgeons must attend to many more delicate details than in other regions. If the surgeons and therapists carefully follow guidelines, generally good or excellent outcomes can be expected. In other words, there is an established path to good and excellent outcomes of zone 2 tendon repair, but a number of technical requirements must be followed. In contrast, in zone 3 through 5 repair, outcomes can be quite good, with less demanding expertise of surgeons and application of fewer technical details.
Anatony, biomechanics and tendon healing
Anatomical points
Understanding the anatomical details of the flexor tendons and surrounding tissues is essential for successful surgical repair. In zone 2, difficulties in surgery and restoration of tendon function relate to the intricate anatomy of flexor tendon system: the coexistence of flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP) tendons within a tight fibroosseous tunnel. Tendons within the synovial sheath—called intrasynovial tendons —were once considered to lack self-reparative capacity; therefore invasion of adhesions from peritendinous tissues was considered to be a prerequisite in the tendon healing process. As the concepts regarding tendon healing biology evolved, tendon cells have been proven capable of proliferating and of producing collagens to heal the tendons. However, the intrasynovial tendon is innately low in cell density and growth factor activity, which limit its early healing strength. Peritendinous adhesions may occur if the repaired tendon does not move early and sufficiently. The dense adhesions jeopardize tendon gliding.
Synovial sheath and pulleys.
The digital flexor sheath consists of the synovial sheath and interwoven condensed fibrous bands (“pulleys”). The synovial sheath is a thin layer of continuous smooth paratenon covering the inner surface of the fibrous sheath. It provides smooth surface for tendon gliding and nutrition to the tendons. The pulley system consists of annular pulleys (condensed, rigid, and heavier annular bands) and cruciate pulleys (filmy obliquely oriented bands). ,
In the thumb, there are three pulleys from proximal to distal—A1, oblique, and A2—with no cruciate pulleys ( Fig. 15.1 ). The A1 pulley is located palmar to the metacarpophalangeal (MCP) joint, the oblique pulley spans the middle and distal parts of the proximal phalanx, and the A2 is located palmar to the interphalangeal (IP) joint.
In the fingers, there are five annular pulleys (A1, A2, A3, A4, and A5), three cruciate pulleys (C1, C2, and C3), and one palmar aponeurosis (PA) pulley. , The A1, A3, and A5 pulleys originate from the palmar plates of the MCP, proximal interphalangeal (PIP), and distal interphalangeal (DIP) joints ( Fig. 15.2 ), respectively, and the A2 and the A4 originate from the proximal and middle phalanges, respectively. The annular pulleys maintain the anatomical paths of tendons close to the bones and joints of the digits, thus optimizing the mechanical efficiency of digital flexion. The more collapsable cruciate pulleys allow for digital flexion to occur with condensation of the fibroosseous sheath at the inner part of flexed fingers. This is called “concertina effect” (see Fig. 15.2 ).
The A2 pulley in the finger is the broadest pulley, which covers the proximal two-thirds of the proximal phalanx, and here in the middle portion of the A2 pulley, the FDS tendon bifurcates. The A4 pulley is located at the middle third of the middle phalanx. The A2 and A4 pulleys are dense, rigid, and have the most important function. The length of the A2 pulley is about 1.5 to 1.7 cm in the middle finger of an average adult, and the A4 pulley is about 0.5 to 0.7 cm. The diameter of the flexor sheath is narrowest at the A4 pulley and in the middle and distal parts of the A2 pulley. , The A2 and A4 pulleys are recognizable by their locations, and both are denser and more rigid than other pulleys or the sheath.
The A1 pulley, over the MCP joint proximal to the A2, has a length of about 1.0 cm; in some fingers, A1 and A2 pulleys merge to form a lengthy pulley-complex. The A3 pulley, overlying the PIP joint, is short (about 0.3 cm) and may be hard to distinguish from the synovial sheath (see Fig. 15.2 ).
The FDS bifurcates at the middle part of the A2 pulley into two slips, and the two FDS slips then go deeper to the FDP tendon and insert into the middle phalanx ( Fig. 15.3 ).
The FDP tendon has two vincula. The short vinculum is located at the insertion of the FDP tendon. The long vinculum connects the FDP tendon through the short vinculum of the FDS tendon to transverse branches of the digital arteries on the palmar surface of the phalanges. The FDS tendon also has two vincula; one connects to transverse branches of the digital arteries on the volar surface of the proximal phalanx, and another at the insertion of the FDS tendon (see Fig. 15.3 ). Vincula carry blood vessels to the dorsum of these tendons, providing limited nutrition.
Zones and subzones of flexor tendons.
Anatomically, the digital flexor tendons are divided into five zones ( Fig. 15.4 ), which offer the fundamental nomenclature for clinical records and surgical repairs. ,
Zone 1: From the insertion of the FDS tendon to the terminal insertion of the FDP tendon;
Zone 2: From the proximal reflection of the digital synovial sheath to the FDS insertion;
Zone 3: From the distal margin of the transverse carpal ligament to the digital synovial sheath;
Zone 4: Area covered by the transverse carpal ligament;
Zone 5: Proximal to the transverse carpal ligament.
In the thumb, zone 1 is distal to the IP joint, zone 2 is from the IP joint to the A1 pulley, and zone 3 is in the area of the thenar eminence (see Fig. 15.4 ).
Twelve flexor tendons exist in the hand and forearm regions. They include finger and thumb flexors and wrist flexors. Finger flexor tendons are the FDS and the FDP, and the tendon in the thumb is the flexor pollicis longus (FPL). These tendons originate from muscles located in the midforearm.
In the mid and distal forearm (zone 5), the tendons of the FDP to four fingers come from a common muscle belly. The tendons of the FDS originate from the separate muscle bellies, which allow more independent finger flexion. The FPL tendon arises from the volar aspect of the midportion of the radial shaft and from its adjacent interosseous membrane. Three wrist flexors—serving to flex the wrist not the digits—are flexor carpi radialis (FCR) and flexor carpi ulnaris, and palmaris longus (PL). The PL is absent in about 15% to 20% of the normal population. Wrist flexion power is not affected by absence of the PL. Therefore the PL is the primary donor for tendon grafting procedures.
Within the carpal tunnel (zone 4), there are nine tendons—four FDS, four FDP, and one FPL. The relationship of these tendons within the carpal tunnel is rather constant. The FDS tendons to the ring and middle fingers lie superficially; deeper are the FDS tendon to the index and small fingers, and deeper still are the FDP tendons. The FPL tendon is located deep and radially adjacent to the scaphoid and the trapezium. After emerging from the carpal tunnel, the tendons enter the palm (zone 3). At about the level of the superficial palmar artery arch, the lumbrical tendons originate from the FDP tendons.
Within the fingers (zones 2 and 1), the tendons glide within a closed fibroosseous sheath deep to segmental, rigid, constrictive dense connective tissue ( Fig. 15.5 ). The digital sheath forms a closed synovial compartment extending from the distal palm to the distal phalanx. Distally, the synovial sheath ends at the insertion of the FDP tendon in the distal phalanges. Proximally, it ends just proximal to the neck of the metacarpals. The FDS tendons lie superficial to the FDP tendons up to the bifurcation of the FDS tendon (see Fig. 15.3 ). Then, the FDS tendon divides, courses laterally and then deep to the FDP tendon. This FDS bifurcation is in the A2 pulley area (see Fig. 15.3 ). The bifurcation part of the FDS tendon also serves to constrain the FDP tendon; in other words, the FDS segment at bifurcation may be viewed as a structure functioning similar to a pulley. Deep to the FDP tendon, the FDS slips rejoin to form Camper’s chiasm, which is the fibrous interwoven connection between the two FDS slips. Slightly more distally, the FDS fibers insert on the proximal and middle parts of the middle phalanx as two separate slips. The FDP tendon inserts into the volar aspect of the distal phalanx (see Fig. 15.3 ). In the thumb, the FPL tendon inserts at the distal phalanx, and it is the only tendon inside the thumb’s flexor sheath.
In the 1990s, the most complex areas—flexor tendons in the digital sheath—were subdivided by Moiemen and Elliot and Tang (see Figs. 15.4 and 15.5 ).
The subdivisions of zone 1 by Moiemen and Elliot are:
1A: The very distal FDP tendon (usually <1 cm);
1B: From zone 1A to distal margin of the A4 pulley;
1C: The FDP tendon within the A4 pulley.
The subdivisions of zone 2 by Tang are:
2A: The area of the FDS tendon insertion;
2B: From the proximal margin of the FDS insertion to the distal margin of the A2 pulley;
2C: The area covered by the A2 pulley;
2D: From the proximal margin of the A2 pulley to the proximal reflection of digital sheath.
Adhesions often develop around the repaired tendon, but not all adhesions cause clinical problems that need surgical intervention. Five variants (grades) of adhesions are seen clinically: (1) no adhesions; (2) filmy adhesions: formation of visible, filmy, and membranous tissue from tendon to surrounding tissues; (3) loose adhesions: loose and largely movable; (4) moderately dense adhesions: of limited mobility; and (5) dense adhesions: dense, almost immovable, and invading deep into the tendon. The first two grades do not affect tendon motion; the third affects motion mildly. Because the fourth and fifth affect motion dramatically, these are the adhesions that surgeons seek to prevent through early tendon motion in therapy. The density of adhesions relates to the tissues from which they arise. The adhesions arising from bones, periosteum, or major annular pulleys are dense. The density of adhesions can be altered to some extent by tendon gliding. Some adhesion fibers can be disrupted as well. Surgeons should do their utmost to preclude or minimize formation of adhesions that will restrict tendon gliding.
Many strategies have been attempted to prevent adhesion formations, including medications, use of artificial or biologic barriers, and chemical or molecular approaches, all with varied results. However, few medications or barriers have become clinically routine. So far, the most effective methods to prevent adhesions clinically are meticulous surgery and early postoperative active motion. The prime cause of adhesions is tendon repair by inexperienced surgeons.
Biomechanics of tendon gliding and repairs
Forces generated during normal hand action range from 1 to 35 N, except tip pinch, according to intraoperative measurements of forces in the tendons. Therefore it is commonly considered that a surgically repaired tendon should be able to withstand a tension of at least 40 N during motion, with power sufficient to resist gap formation at the repair site. The repair should be able to withstand repeated loads (cyclic loads) under both linear and curvilinear load conditions. Biomechanical studies showed that failure forces of 4-strand repairs are around or beyond 40 N; 6-strand repairs fail with loads more than 50 to 60 N. Hence, at least a 4-strand core suture should be used.
The following factors affect the strength of a surgical repair: (1) the number of suture strands across the repair sites—the strength of a surgical repair is roughly proportional to the number of core sutures; (2) the tension of repairs—most relevant to gap formation and stiffness of repairs; , (3) the core suture purchase; , (4) the types of tendon-suture junction—locking or grasping; (5) the diameter of suture locks in the tendons—a small diameter of locks diminishes anchor power; , (5) the suture calibers (diameter); (6) the material properties of suture materials; (7) types of the peripheral sutures; (8) the curvature of tendon gliding paths—the repair strength decreases as tendon curvature increases. , In addition, the holding capacity of a tendon plays a vital role in repair strength and is affected by degrees of trauma and consequent softening of the tendon tissue.
To achieve an optimal surgical repair, a core suture purchase of at least 0.7 to 1.0 cm is necessary to generate maximal holding power. , The diameter of the suture locks must be at least 2 mm. , Clinically, the suture size used in adults is either 3-0 or 4-0; sutures of 2-0 or greater are too large and rigid in the hand. With an identical number of core sutures across the tendon laceration, different locking junctions result in small differences in the strength. A locking tendon-suture junction is only slightly better than a grasping junction in terms of holding power.
Peripheral sutures mainly serve to “tidy up” the approximated tendon stumps; they also add strength to repairs. Many surgeons now use simple peripheral stitches. Some surgeons even do not supplement peripheral stitches when they repair the tendon with a strong 6-strand core suture. It is a current trend to use very simple peripheral sutures, which simplifies repair maneuvers while stressing a solid and strong multi-strand core suture.
Tendon curvature affects strength during early active flexion of the digits. Surgical repair in a tendon under a curvilinear load is weaker than that under a linear load; the repair strength decreases as the curvature increases. , Mechanically, a tendon under linear tension is pulled without being bent, whereas a tendon under curvilinear tension is subjected to both linear pulling and bending forces. Therefore the repair fails more easily in the extremely flexed finger. When the finger approaches full flexion, a strongly bent tendon is particularly prone to fail. The above studies in the strength of the tendons in the extremely flexed digits are the basis of current partial-range active flexion exercise, in which extreme active flexion of the digit is avoided in the first a few weeks after tendon repair.
Annular pulleys are critical to the mechanical function of the digital flexor tendons. Extensive loss of the sheath and pulleys causes anterior displacement— bowstringing —of the flexor tendon during finger flexion. In fingers, the A2 and A4 pulleys are most critically located and functionally important. Nevertheless, given the presence of other pulleys and sheath, loss of any individual pulleys—including the A2 or A4 pulley—results in few detrimental consequences. Incision of the A2 pulley up to one-half or two-thirds of its length or of the entire A4 pulley results in no tendon bowstringing and little loss of digital flexion. , Even the entire A2 pulley can be incised to favor tendon gliding if necessary. ,
The surgeons in Saint John NB, Canada, and Niigata, Japan, incise up to 2 cm of pulley, including the entire A2 or A4 pulley if required, and find such venting results in no clinically noteworthy tendon bowstringing and little loss of digital flexion. , Therefore the rule in these institutes is to vent the entire A2 pulley if necessary. The length of venting is preferably decided through digital extension-flexion testing during surgery in a wide-awake patient.
Loss of the A3 pulley alone has few consequences, and loss of the A3 pulley together with the A4 pulley may be acceptable as well. Excessive loss of the sheath should be avoided to prevent clinically meaningful bowstringing; however, loss of a small portion (<2 cm in length) of the sheath-pulley, even including a part of the A2 pulley or entire A4 pulley, does not cause noteworthy bowstringing provided that the other pulleys are intact. These more recent practices have led to much easier surgical repair and smoother tendon gliding after surgery, which are as important as the use of strong surgical repairs.
Tendon healing, gliding, and remodeling
After trauma and surgery, tendons and surrounding tissue undergo inflammation and edema. The volume of the tendons is increased, which increases the resistance within the narrow sheath tunnel when the repair is in digits. Subcutaneous edema outside the sheath also impedes tendon motion. The safety margin can be enhanced by a strong surgical tendon repair and appropriately venting the narrow pulleys to avoid overloading the repaired tendons and risk repair ruptures. Based on mechanical studies, the resistance to tendon gliding is determined mainly by the severity of edema in the area of surgical repair. Therefore besides the quality of surgical repair, the severity of edema should be considered in deciding how rigorous the postoperative motion program should be. Similarly important is to limit the extension of surgical incisions proximal to the tendon repair sites, because edema in the proximal areas would increase resistance to tendon gliding during active digital flexion after surgery. These considerations are the basis of recent use of shorter incisions to expose and repair the tendons in the digits.
After surgery, adhesions do not occur in the first few days; therefore leaving the fingers immobile does not cause adhesions. In fact, the absence of digital motion in the first few days may decrease bleeding and lessen the risk of later formation of adhesions. Therefore leaving the fingers immobile in the first few days after surgery is beneficial to preventing adhesion formations. Doing so diminishes swelling, decreases the resistance to tendon gliding, and allows the patient to get off all pain medication so the patient can begin early protected movement 3 to 5 days after surgery without much pain.
Clinical presentation and diagnosis
Flexor tendon injuries are often caused by trauma resulting from a sharp cut or a crush, but they can also present as closed injuries. Open injuries due to extensive trauma are frequently associated with neurovascular deficits. Closed injuries often relate to forced extension during active flexion of the finger. In addition, flexor tendon rupture occurs as a result of chronic attrition in rheumatoid disease, Kienböck disease, scaphoid nonunion, and a hamate or a distal radius fracture.
The patient’s history and the mechanism of injury can alert the surgeon to the extent of the tendon trauma and associated injuries. On examination, the natural resting posture of the wounded digits is often disrupted. Complete lacerations of both FDP and FDS tendons are easily diagnosed when a wound is found on the palmar surface of a finger and the affected finger(s) is seen in a relatively extended position. The digit(s) lose active flexion at PIP and DIP joints. For testing the FPL tendon, the thumb MCP joint is stabilized in extension. The patient is asked to flex the IP joint. Absence of active flexion at the IP joint indicates complete severance of the FPL tendon.
If the patient can actively flex the DIP joint while the motion of the PIP joint is blocked, there may be only incomplete laceration or no injury to the FDP tendon ( Fig. 15.6 ). Weakness during resisted finger flexion indicates a possible partial tendon cut. To assess the continuity of the FDS tendon, the examiner holds the adjacent fingers held in full extension. The FDS tendon is severed completely if the patient cannot actively flex the PIP joint (see Fig. 15.6 ).
The FDS in 30% to 35% of little fingers has connections with the FDS in the ring or middle fingers. Variations of the FDS tendons in the little finger are frequent. Some little fingers (10% to 15%) are missing an FDS tendon. These patients have limited or no PIP joint flexion of the little finger during testing.
Nerve and artery function should be assessed routinely because accompanying injuries in the neurovascular bundles on one or both sides of the fingers or median and ulnar nerves at the carpal tunnel or distal forearm are common. Loss of sensation in the finger pulps or loss of function of some intrinsic muscles in the hand are indicative of such accompanying injuries. Treatment of neurovascular injuries must be included in planning surgical strategies. If fingers or hands are found to be hypovascular or avascular due to arterial lacerations, vascular anastomosis should be a surgical emergency. Otherwise, after wound debridement, either the lacerated flexor tendons can be repaired (when experienced surgeons are readily available) or the skin can be closed to allow for delayed primary repairs within days by experienced surgeons.
Associated fractures are not rare and require treatment. Plain radiographs are necessary for most patients. Ultrasonographic examination is particularly useful to diagnosis closed rupture of tendons. Surgeon-performed ultrasound also lets the operator know exactly where the proximal and distal tendon ends are so that shorter incisions to decrease postoperative adhesions are appropriate. CT scans or MRI images are usually not necessary for diagnosis of open tendon injuries. However, for diagnosis of closed tendon ruptures or suspected ruptures of the primary end-to-end surgical repair, CT scan or MRI image are of particular diagnostic value.
Methods of primary repair
Timing of direct repair
Acutely lacerated flexor tendons in the hand and forearm should be treated primarily or at delayed primary stage, usually within 4 weeks, ideally within 1 to 2 weeks. Primary tendon repair is defined as the end-to-end repair performed immediately after wound cleaning and debridement, usually within 24 hours after trauma. Delayed primary repair is defined as the repair performed within 3 or even 4 or 5 weeks after tendon lacerations. No clinical investigations have validated the best time for direct repair. In a dirty wound where infection is very likely, it may be wise to postpone the repair until the wound is sterile.
The timing of direct repair of the lacerated digital flexor tendons is not important if the repair is not delayed too long. Although primary repair immediately after trauma is always preferable, delayed primary repair within 1 to 2 weeks after injury gives outcomes quite similar to those of a primary repair. Very delayed primary repair (>3 or 4 weeks after injury) can also be attempted, but conservative measures, such as using a very strong repair, should be taken; and surgeons should be very experienced, because the intraoperative decision as to whether to proceed with secondary tendon reconstruction requires expert judgment.
The tendon injured in critical areas (such as zone 2) should not be repaired by an inexperienced surgeon. Rather, the tendon repair can be delayed until an experienced surgeon is available. Our preferred period of deliberate delay is 4 to 7 days, when the risk of infection can be addressed and edema has diminished. The tendon can be repaired after delay for 1-2 weeks. Delay for 3 to 4 weeks makes the repair difficult under greater tension, but the repair can often be performed.
Late direct repair (the repair one or a few months later) encounters large tension at the repair site because of static shortening of the muscle unit after lengthy delay. The late repair is not often attempted, but it is possible in some patients, which is subjected to intraoperative judgment and decision. If it is to be attempted, the surgeon should inform the patient the possibility of giving up the direct repair during surgery. Instead, tendon grafting is performed in the future (if it is less than 3 months after injury) or immediately (if it is beyond 3 months). Some surgeons directly repair the tendon if the two stumps can be pulled together in finger flexion; recovery of muscle elasticity has been seen months later. For the cases of late direct repair, another practical option is to lengthen the tendon within the muscles in the forearm, to ease the tension at the time of the direct repair, or months later if muscle elasticity is not recovered.
Indications and contraindications
The end-to-end tendon repairs are indicated mainly in clean-cut tendon injuries with limited damage to peritendinous tissues. Accompanied neurovascular injury is common and is not a contraindication for primary repairs. However, loss of soft tissue coverage over the tendon or the presence of fractures are borderline indications. Local defects in skin and subcutaneous tissues can be covered by flaps ( Box 15.1 ).
Indications
- 1.
Clean-cut tendon injuries.
- 2.
Tendon cut with limited peritendinous damage, no defects in soft tissue coverage.
- 3.
Within several days or 3 or 4 weeks after tendon laceration.
- 4.
Late direct repair (delay >4 weeks) may be possible in some patients.
- 5.
Regional loss of soft tissue coverage or phalangeal fractures are borderline indications.
Contraindications:
- 1.
Severe wound contamination.
- 2.
Bony injuries involving joint components or extensive soft-tissue loss.
- 3.
Destruction of a series of annular pulleys and lengthy tendon defects.
- 4.
Experienced surgeons are not available.
Digital fractures can be fixed at the same time as tendon repair. Nevertheless, serious crush injuries, severe wound contamination, loss of extensive soft tissues, or extensive destruction of pulleys and tendon structures are contraindications for primary tendon repairs. Fractures involving multiple bones, particularly at different levels and the impossibility of stable internal fixation, are contraindicative to primary tendon repairs.
Surgical techniques
Anesthesia.
Brachial plexus block with the use of a tourniquet in the upper arm or local anesthesia without the use of a tourniquet are used currently. Local anesthesia with epinephrine without the use of tourniquet (WALANT) is highly recommended. This enables intraoperative assessment of active motion of the repaired tendons and the quality of repair. Most patients will opt for WALANT if the surgeon explains to them that local anesthesia can be given almost painlessly and that intraoperative active testing and intraoperative surgeon/patient communication may lead to a better result. If the patient is still against WALANT, local anesthesia with sedation or brachial plexus block is usually sufficient. General anesthesia can be used when associated injuries are severe.
Surgical incision.
In the finger, the lacerated tendons are approached through the skin injury with a volar extension distally for 2 to 3 cm, just enough to expose the tendons and carry out a good, solid repair. In previous books, authors have described that tendons are exposed through zigzag skin incisions on the volar side of the fingers (e.g., Bruner’s incision). However, a long Bruner’s incision is not necessary in most patients. A short incision in the intact skin distal to the laceration and reopening the traumatic wound is usually sufficient, as the distal tendon end commonly lies distal to the skin laceration (because the finger is commonly flexed during injury) (see Fig. 15.7 ). Proximal tendon ends are not often found with this small incision. We advise not extending the incision proximally in search of the retracted tendons. Instead, an incision of about 1 cm is made in the distal palm along a palm crease to find the stump of the FDP, which is delivered to the repair site in the finger under intact skin and within the digital sheath. The use of a small incision in the finger diminishes edema in the finger and resistance to tendon gliding during rehabilitation ( Fig. 15.8 ). A separate incision in the palm is wise, which shifts edema from finger to palm, causing little resistance to tendon gliding, because the palm is large and easily accommodates edema.
Such retrieval of the retracted proximal tendon stump is often required, especially for delayed primary repairs. Through an incision in the distal palm, the FDP tendon can be found beneath the FDS tendon and is grasped with two sets of forceps. The tendon is pushed distally with the proximal forceps with the distal ones released, and the distal forceps is then moved proximally to grasp and push again. Repeating the maneuver a few times usually advances the proximal stump into the digital laceration site (see Figs. 15.8 and 15.9 ). A needle is placed transversely at the base of the digit through the tendon to temporarily immobilize the retracted tendon stump for surgical repair.
In repairing tendon lacerations in the palm, surgeons often need to reopen the wound and extend it proximally as the proximal tendon ends often retract. The proper or common digital nerves are often cut as well, which need exploration and repair.
Treatment of the sheath and pulleys.
To expose the tendons and later carry out surgical repair, the sheath needs to be opened, and the total length of sheath opening should be less than 2 cm ( Fig. 15.10 ). The sheath opening can include a part of A2 pulley or the entire A4 pulley (or combined with the A3 pulley), as judged by the level of the tendon laceration (see Fig. 15.10 ). If the laceration is at or just distal to the A2 pulley, which is 1.5 to 1.7 cm long in adults, the A2 pulley can be vented to one-half or two-thirds of its longitudinal extent ( Fig. 15.11 ). If the laceration site is close to the A4 pulley, the A4 pulley is vented entirely ( Fig. 15.12 and Box 15.2 ).
- 1.
Repairing the flexor tendons is the art of meticulous surgery built on a thorough master of anatomy of the flexor tendon system. The surgeons should know the anatomy in detail, including the lengths of major pulleys, characteristic changes in the diameter of the sheath, and tendon gliding amplitude.
- 2.
Primary repairs should be performed by experienced surgeons whenever possible. Before surgery, the surgeon must review the anatomy of the flexor tendon system and understand every detail of the requirements for an optimal tendon repair.
- 3.
The surgeon’s mastery of atraumatic techniques is essential.
- 4.
The outcomes of the repairs are expertise-dependent; repair of tendons by an inexperienced surgeon is a frequent cause of tendon adhesions and poor function.
- 5.
Strong surgical repairs are necessary. At least a 4-strand core suture should be used; a 6-strand core suture is preferable.
- 6.
Within the digital sheath, the venting of a part of sheath (<2.0 cm), including either a part of the A2 or the entire A4, provides easy access to the injured tendons and decreases resistance to tendon gliding after surgery. Only vent as much as is needed to let the repair glide freely during full fist flexion and extension testing during the surgery. This will allow a good solid repair to heal without rupture and yet not get stuck on an impinging flexor sheath.
Biomechanically, such venting has no clinical functional consequence. Venting can be along the midline of the sheath and pulleys or laterally ( Fig. 15.13 ). In delayed repair, the sheath or pulleys may be fibrotic, and excision of a part of the sheath or pulleys may be needed, which is pulley shortening (see Fig. 15.13 ). Occasionally, release of the entire A2 pulley may be necessary to allow tendon gliding, although in the majority of the patients, part of the A2 pulley can be preserved.
For the repair of the FPL tendon, releasing the oblique pulley between the A2 and A1 pulleys of the thumb is usually necessary, or a part of the oblique pulley is vented along with venting of the entire A1 pulley. The narrow A1 pulley can be cut entirely, but this is not sufficient, and part of the sheath or at least part of the oblique pulley distal to the A1 pulley needs to be incised as well. Surgeons should at least keep one of the three pulleys in the thumb; often, one intact annular pulley with a part of the oblique pulley can maintain full function of the thumb.
Surgical treatment in different zones.
Tendons should be handled as atraumatically as possible. Ragged tendon tissue at the cut sites is removed with a scalpel to make the tendon cut ends fresh and even. The tendon ends can be trimmed for 1 to 3 mm (up to 5 mm if needed) at each side, which does not cause tendon defects or functional disturbance. Basic requirements of a surgical repair are (1) sufficient strength, (2) smooth tendon surface, although some bulkiness at the repair site is allowed to ensure some tension at the junction of two stumps, (3) no gapping of the repair site under tension, and (4) easily performed.
Zone 1 injuries : In this area, only the FDP tendon is present, and it is rather flat. When the tendon laceration is in the distal part of this zone, i.e., zone 1A and 1B, because the vincula connect to the proximal tendon to prevent retraction, both the proximal and distal ends can be easily found not far from the skin wound. When cut in zone 1C, the tendon sometimes retracts proximally.
For zone 1A injuries, the distal stump is very short, but direct repair is often possible, which is a recent technique used by a number of surgeons including colleagues in Nantong and Zurich. Two of us (JBT and MC) regularly use this method and no longer use more complicated conventional pullout suture methods. 61 Such a direct repair is to suture the proximal stump of the FDP to any residual tendon tissue at its insertion and its surrounding tissues, such as the periosteum and the very distal part of the volar plate; 10- or 12-strand sutures are needed to make a strong direct repair to the very short distal residual FDP stump ( Figs. 15.14–15.17 ). The repair strength is obtained through the use of a lot of strands. In repairing a FDP cut at the site near insertion, because the repair site is distal to the DIP joint, formation of adhesions would not damage tendon gliding, but such adhesions are helpful to repair strength. Therefore using a lot of core sutures is acceptable, and adhesions are, in fact, not detrimental, which is different from any other area of the digital flexor tendons.
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