PART VIII
HAND
CHAPTER 77 FLEXOR TENDON REPAIR
BRADON J. WILHELMI
INTRODUCTION
Flexor tendon injuries have long been considered one of the most challenging problems for hand surgeons. Poor results following flexor tendon repair in the fingers led one expert hand surgeon, Boyes, to state “Here in a small area we have two flexor tendons, one passing through the other in a close fitting sheath and snugly held to the proximal phalanx by a pulley which is unyielding so that either trauma or infection squeezes out the blood supply and the tendon dies of ischemia. Suturing of a divided tendon usually results in some thickening and this enlarged area cannot pass the constricting pulley and motion is prevented.”1 Furthermore, Bunnell coined the term “no man’s land” to emphasize the difficulties associated with injuries in this area of the digital sheath.2 If we exclude flexor tendon injuries within the digital sheath, however, the remaining flexor tendon injuries are not a problem. For injuries in no man’s land, adherence to certain surgical techniques and postoperative therapy programs can optimize results and finger motion. Harold Kleinert revolutionized the primary repair of acute flexor tendon injuries in the digital sheath, after others had treated them for decades in a staged fashion with grafts for years.3
ANATOMY
Accordingly, Verdan classified flexor tendon injuries by the location of transection relative to the extremity and their prognosis4 (Figure 77.1A). For simplicity, injuries are classified based on zones: distal to the flexor superficialis insertion (zone 1), within the digital sheath of the flexor superficialis and profundus (zone 2), palm (zone 3), within carpal tunnel (zone 4), and in the forearm proximal to the carpal tunnel (zone 5). In general, flexor tendons repaired in zones 1, 3, 4, and 5 have a better prognosis than those in zone 2.
FIGURE 77.1. Zones of flexor tendon injury. A. Distal to the flexor superficialis insertion (zone 1), within the digital sheath of the flexor superficialis and profundus (zone 2), palm (zone 3), within carpal tunnel (zone 4), and in the forearm proximal to the carpal tunnel (zone 5). In general, flexor tendons repaired in zones 1, 3, 4, and 5 have a better prognosis than those in zone 2, known as “no man’s land.” B. Brunner’s zigzag extensions to optimize exposure of the proximal and distal ends of the flexor tendon.
The flexor tendons originate in the forearm with muscles arranged in three different layers: superficial, intermediate, and deep. The superficial layer consists of the pronator teres, flexor carpi radialis, palmaris longus, and flexor carpi ulnaris. The pronator teres, palmaris longus, and flexor carpi radialis are innervated by the median nerve, whereas the flexor carpi ulnaris receives stimulus from the ulnar nerve. The intermediate layer includes only the flexor digitorum superficialis, innervated by the median nerve. The deep layer consists of the flexor digitorum profundus, flexor pollicis longus, and pronator quadratus. The median nerve innervates the flexor pollicis longus, pronator quadratus, and index/middle finger flexor digitorum profundus. The small and ring flexor digitorum muscles are innervated by the ulnar nerve.
Within the carpal tunnel, nine tendons pass to their respective digits. The flexor pollicis longus is the most radial structure, inserting onto the thumb distal phalanx. The flexor digitorum profundus tendons are found along the base of the carpal tunnel, aligned in order to insert into the base of the distal phalanx of the index through the small fingers. The flexor superficialis tendons course under the carpal tunnel in a stacked array with the middle and ring tendon volar to the index and small finger tendons, which insert into the middle of the middle phalanx of each respective finger. In the palm, the flexor superficialis tendons are initially volar to the flexor digitorum profundus tendons. The flexor digitorum superficialis tendon decussates at the level of Camper’s chiasm, to allow the flexor digitorum profundus to become more volar in the finger. The flexor digitorum superficialis and flexor digitorum profundus tendons course in the finger in a fibro-osseous canal that is lined by synovium and reinforced by a pulley system.
The fibro-osseous canal is comprised of pulleys with variable anatomy depending on their function. There are annular pulleys, labeled A1 to A5, and cruciate pulleys, labeled C0 to C4 (Figure 77.2). The A1, A3, and A5 pulleys prevent bowstringing of the flexor tendon across the metacarpophalangeal joint, proximal interphalangeal (PIP) joint, and distal interphalangeal joint, respectively. The A2 and A4 pulleys prevent bowstringing of the flexor tendon across the proximal phalanx and middle phalanx, respectively. The A2 and A4 pulleys are known as the critical pulleys because they are thicker, longer and in a more critical area than other annular pulleys, allowing them to aid in the prevention of bowstringing. A deficiency of 25% of either of these critical pulleys has the potential to result in the condition of bowstringing. Found between the annular pulleys, the cruciate pulleys (C0 and C3) are of less biomechanical and functional significance.
FIGURE 77.2. Pulley system. The A2 and A4 pulleys are the most critical. When a certain amount of either of these pulleys is missing the flexor is not held down to the bone which increases the moment of the system. Widening of the moment arm causes less motion of the fingertip with a given tendon excursion, resulting in bowstringing of the finger and loss of fingertip flexion. Redrawn from Wilhelmi BJ, Snyder N, Verbesey JE, Ganchi PA, Lee WPA. Trigger finger release with hand surface landmark ratios: an anatomic and clinical study.Plast Reconstr Surg. 2001;108(4):908-915.
Digital flexor tendons receive nutrition from both intrinsic and extrinsic sources. The synovial fluid provides extrinsic nutrition with pumping action facilitated by flexion and extension of the fingers. Flexor tendons receive intrinsic nutrition by three sources, including longitudinal vessels entering the palm in the endotendinous channels, vessels that enter at the osseous insertion, and vincula (two short and two long). Most of the internal nutrition is delivered on the dorsal side of the tendon.
Flexor tendon function depends on many factors, including tendon excursion, intact pulley system, joint motion, and the presence of lubricating synovial fluid. Flexor excursion can be limited by adhesions among tendons, bones, and the synovial sheath. If bowstringing is present, greater amplitude of muscle contraction and greater amount of tendon excursion is required to close the fingertip to the palm.
DIAGNOSIS
Clinical exam provides the most accurate means of detecting flexor tendon injuries. When the flexor tendon is transected, the finger will have impaired flexion. Pain may limit the utility of this exercise and other examination maneuvers are required. Flexor tendon lacerations can be identified by observing a loss of normal finger cascade. Injuries to the flexor tendons can also be suggested by loss of tenodesis effect with passive wrist extension and flexion. Another useful technique to evaluate integrity of the flexor tendons can be compressing the distal forearm that normally brings the fingers into the flexed posture.
Diagnostic studies are occasionally helpful. Plain radiographs, magnetic resonance imaging, or ultrasound may help detect the location of the proximal tendon after closed zone 1 injuries (jersey finger injury). Knowing the location of the proximal tendon also assists in management. When the Flexor Digitorum Profundis (FDP) retracts to the palm (Leddy type 1), the tendon must be repaired within 2 weeks. When retracted to the PIP joint, the repair must be performed within 6 weeks (Leddy type 2). When caught at A4 pulley (Leddy type 3), the repair can be performed at any time.5 Fullness and tenderness at these locations, if present, direct management of jersey finger injuries making diagnostic studies unnecessary. The presence of neurovascular injuries should also be assessed for open lacerations at any level.
Partial tendon injuries are suggested in patients with pain on resisted flexion. On exploration, if the injury is more than 60% of the tendon in diameter, it should be repaired. If the injury is less than 60% of tendon diameter, the free edges are debrided to prevent catching on the pulleys.6
TREATMENT
Ideal flexor tendon repairs are strong and smooth. Strength allows for early active motion to prevent adhesion formation. Repairs should be strong enough to resist gap formation, which can be a site for adhesion formation or repair rupture. Repair techniques should also be smooth and not bunched to facilitate gliding of the tendons around adjacent structures such as pulleys or other tendons. Repairing flexor tendons within 24 to 72 hours minimizes adhesions, tendon retraction, and repair tension, along with gapping at the repair site and joint stiffness. Full exposure of the proximal and distal tendons usually requires extending the laceration in a zigzag (Bruner) or mid-longitudinal fashion (Figure 77.1B). The distal end of the tendon will be found more distally when the injury occurred with the finger in flexion. If the finger was extended at the time of injury, the proximal and distal tendon ends are found at the laceration level. Excessive manipulation of the flexor tendons should be avoided to minimize adhesion formation. Flexor tendons should be grasped in the core of the severed end to avoid epitenon injury that could be nidus for adhesion formation. In general, the technique of flexor tendon repair is dictated by the zone of flexor injury.
Repair Techniques
Several techniques of flexor tendon repair have been described over the years. Tendon repair strength has been shown to be proportional to the number of strands of suture placed across the repair site. There are multiple different types of suture material that can be used for flexor repairs, including Ticron, nylon, Ethilon, Mersilene, Prolene, and stainless steel wire. The ideal suture material is nonreactive, of small caliber, is strong, and with excellent knot-holding characteristics. The suture techniques have different grasping qualities depending on the cruciate, mattress, and cross-stitch configuration. Knots tied within the repair site may consume space and delay healing, whereas knots placed outside the repair may increase friction and adhesion formation. Suture placement may be better on the volar surface to avoid hindering blood delivery to the tendon, which is along the dorsal surface. Use of an epitendinous suture in addition to the core suture adds 20% to the strength of the repair.
Recently, the modified Becker technique (MGH, Massachusetts General Hospital) has gained popularity for its strength, resistance to gap formation, and endurance with active range of motion therapy.6-12 The MGH technique is like the Becker repair as it involves placement of four strands through the core in a criss-cross configuration13 (Figures 77.3A–B). However, the MGH is different in that the core sutures are 3-0 instead of 6-0 and includes augmentation with an epitenon suture and avoids the step-cut bevel.
FIGURE 77.3. The MGH flexor tendon repair technique. (A) This technique is like the Becker repair as it involves placement of four strands through the core in a criss-cross configuration. (B). However, the modified Becker technique (MGH) is different in that the core sutures are 3-0 instead of 6-0, and it includes augmentation with an epitenon suture, avoiding the step-cut bevel. © Bradon J. Wilhelmi, MD.
Specifically, the MGH involves approximation of the epitenon with 6-0 nylon suture in a continuous fashion. Then two double-armed 3-0 sutures (Prolene) are used to place four criss-cross sutures through the core. The criss-crosses of two of the four core sutures are placed on each side of the tendon. These sutures are initiated by placing the 3-0 suture (Prolene) transversely through the lateral aspect of the tendon at least 1.5 cm from the tendon end (Figure 77.4A). Then one of the needles is driven in the oblique direction through the tendon (Figure 77.4B). This is repeated two more times in a spiral fashion and brought out the core, creating oblique suture lines parallel to each other on the external surface of the tendon (Figure 77.4B). The other needle of the first 3-0 suture (Prolene) is then used to place sutures perpendicular to the previous spiral of sutures (Figure 77.4C). These criss-crosses are created by taking the second needle in the oblique direction through the tendon between the parallel lines of the suture on the external surface in the proximal to distal direction to exit the core. This technique is repeated on the distal end of the tendon (Figure 77.4D).
The second double-arm 3-0 suture (Prolene) is used to complete the criss-cross cores on the contralateral side. In performing this technique, three criss-crosses are placed on either end of the tendon. The sutures should be pulled taut to facilitate tendon compression and preload the repair to prevent gapping. Furthermore, before tying the knot the suture is carefully see-sawed to take the slack out and compress the tendon ends, preloading the repair to prevent gap formation.
A monofilament suture (such as Prolene) slides through the tendon substance better and is preferred for preloading and minimizing gapping. However, the disadvantage of a monofilament is the need for multiple knots, which can increase resistance to glide. A modification of the MGH technique involves laying this stack of knots longitudinally along the tendon with another purchase as far from the stack as the height of the stack (Figure 77.4E). Then, three more ties can be performed to lay the stack of knots along the tendon (Figure 77.4F). A taper needle is preferred. Furthermore, the MGH technique should be avoided in patients who require cast immobilization, replants, or combined injuries that cannot be enlisted in early active motion therapy, because of the increased resistance to gliding as shown by biomechanical studies.
Zone 1 Injuries. Zone 1 flexor injuries occur at the level distal to the flexor digitorum superficialis insertion and by definition can only involve the flexor digitorum profundus. An attempt should always be made to repair the profundus tendon. If the patient presents too late for repair and the Flexor Digitorum Superficialis (FDS) is intact, a distal interphalangeal joint arthrodesis can be considered. Grip strength, however, will be decreased. The finger is opened with a Bruner incision to expose the proximal and distal tendon ends. If the proximal end has retracted, wrist and finger flexion with forearm compression can help milk the tendon distally to the opening in the sheath where it can be carefully grasped with a small mosquito or Jacobson and repaired to the distal stump. Usually, the long vincula prevent retraction of the profundus past the A2 pulley. As much of the A4 pulley as possible should be preserved in exposing the proximal tendon end. A hypodermic needle can be used through the proximal tendon and proximal pulley to hold it during the repair. Because early active motion is not as critical for repairs at this level, the repair technique is the surgeon’s choice. If there is less than 1 cm of distal flexor digitorum profundus stump, the proximal tendon can be advanced to the decorticated distal phalanx with Keith needles and repaired dorsally over the sterile matrix of the nail with a button. Repair over the sterile matrix minimizes the risk of nail deformity. For avulsion injuries of the flexor digitorum profundus, the Leddy classification provides guidance for the timing of repair.
Zone 2 Injuries. Zone 2 injuries occur within the digital sheath from the distal palmar crease to the middle of the middle phalanx where the flexor digitorum superficialis inserts. Flexor repairs are more challenging in this area because of the pulley system, and coursing of the flexor digitorum profundus through the chiasm of the flexor digitorum superficialis. A zigzag Bruner type incision or mid-longitudinal incision is used for exposure of the pulley system and tendon to avoid flexion contracture formation. In exposing the tendon ends, it is important to preserve the critical A2 and A4 pulleys. The cut profundus should also be carefully pulled through the superficialis if it is proximal to the chiasm. The retracted proximal tendons can be retrieved as described above by the forearm milking with wrist and finger flexion. Once retrieved, the proximal tendon can be stabilized with a hypodermic needle. Repair of both tendons is performed for optimal strength and reduced risk of injury. The same technique should be utilized in repairing both tendons to allow for appropriate described therapy. In other words, if a technique that allows for early active motion is used for the flexor digitorum profundus, the same technique should be used on the flexor digitorum superficialis. Even though the risk of adhesion formation is theoretically increased with repair of both tendons, the best results occur when both are repaired. In addition, repair of both prevents hyperextension of the PIP joint. Selection of a strong repair for injuries in this zone allows for early active motion and better postoperative range of motion (Figures 77.5A–C).
Zone 3, 4, and 5 Injuries. Most research has focused on the treatment of flexor tendon injuries in zones 1 and 2.
Many studies have shown that flexor repairs for injuries in these zones 3, 4, and 5 do well if basic surgical principles are followed. Wide exposure and carpal tunnel release is generally required to facilitate identification of not only the injured tendons but other neurovascular structures that require repair. It may be necessary to tag and align structures to ensure appropriate coaptation with the respective tendons when multiple tendon injuries are encountered such as in a spaghetti wrist injury. Remember that the stacked array of the middle and ring flexor digitorum superficialis volar to the index and small flexor digitorum superficialis assists in identifying the proximal flexor tendons. The distal tendons can be localized by pulling on the tendon end to observe its function. In general, composite grip is recovered in these patients with the flexor tendons moving en masse. However, recovery of independent tendon glide for injuries at this level is variable and optimized by the use of early active motion protocols. Reduced active and passive motion after zone 5 injuries can result from adherence of all the tendons en bloc to the pronator quadratus, necessitating a later tenolysis procedure (Figures 77.6A–C).
THERAPY
Without good hand therapy, flexor tendon repairs are doomed. Several flexor therapy regimens have been described. Each protocol places different tensile stress demands on the tendons at the repair site. Techniques that allow for more aggressive therapy are preferable because stressed tendons heal faster, gain strength more rapidly, have fewer adhesions, and result in better excursion and function.
There are two types of protocols: passive motion and active range of motion protocols. Passive range of motion programs include the Duran and Kleinert protocols. The Kleinert protocol involves the use of nail plate hooks with elastic bands attached proximally to the palm and wrist to passively draw the fingers into flexion. The Duran protocol requires the patient to passively move the fingers into flexion. In both cases, patients actively extend their fingers into the dorsal blocking splint. Both protocols include the use of dorsal blocking splints with the wrist in 20° to 30° of flexion, metacarpophalangeal joints at 70° to 80° of flexion, and the interphalangeal joint straight. All the fingers are placed in the splint and permitted to actively extend to splint. Passive proximal and distal interphalangeal joint motion within the restrains of the dorsal blocking splint is encouraged four times a day. At 4 weeks, active composite flexion and extension are performed outside the splint, while dorsal blocking splint is continued between exercises. At the fifth week, the dorsal blocking splint is discontinued. Blocking exercises may be initiated at 6 weeks. Gentle passive extension is initiated and a static extension splint may be used if extrinsic flexor tightness is encountered. At 8 weeks, light strengthening is started and resisted exercises are begun at 10 weeks. By 12 weeks normal activities are performed.
FIGURE 77.4. Modified Becker technique. These first two cores are started by placing the first bite with 3-0 suture (Prolene) transversely through the lateral aspect of the tendon at least 1.5 cm from the tendon end (A). Then one of the needles is driven in the oblique direction through the tendon (B). This is repeated two more times in a spiral fashion and brought out the core, creating oblique suture lines parallel to each other on the external surface of the tendon (B). The other needle of the first 3-0 suture (Prolene) is used to place sutures perpendicular to the previous spiral of sutures (C). These criss-crosses are created by taking the second needle in the oblique direction through the tendon between the parallel lines of the suture on the external surface in the proximal to distal direction to exit the core. This technique is repeated on the distal end of the tendon to complete the criss-cross on both ends of the tendon (D). The second double-arm 3-0 suture (Prolene) is used to complete the criss-cross cores on the contralateral side. In performing this technique three criss-crosses are placed on either end of the tendon. The sutures should be pulled taut at each suture purchase to facilitate tendon compression and preload the repair to prevent gapping. Furthermore, before tying the knot the suture carefully is see-sawed to take the slack out and compress the tendon ends, preloading the repair to prevent gap formation. A monofilament suture (such as Prolene) slides through the tendon substance better and is preferred for preloading and minimizing gapping. However, the disadvantage of a monofilament is the need for multiple knots, which can increase resistance to glide. A modification of the MGH technique involves laying this stack of knots longitudinally along the tendon with another purchase as far from the stack as the height of the stack. (E) Then, three more ties can be performed to lay the stack of knots along the tendon (F). © Bradon J. Wilhelmi, MD.
FIGURE 77.5. Zone 2 repair of both the flexor digitorum superficialis and profundus. A. The ring finger has lost cascade from flexor digitorum superficialis and profundus transaction. B. This demonstrates repair of both the profundus and superficialis with the modified Becker MGH tenorrhaphy. C. Postoperative photos of the patient to have recovering normal flexion with composite grip and differential gliding and near-normal extension. ©Bradon J. Wilhelmi, MD.
FIGURE 77.6. Zone V multiple flexor tendon repair (A) with recovery of normal composite grip and extension (B), as well as differential flexor gliding of the superficialis index, middle, ring, and small fingers (C). © Bradon J. Wilhelmi, MD.
An example of an active range of motion program, the MGH protocol, involves the use of a splint similar to the passive regimens (Table 77.1). However, in addition to passive flexion and active extension within the splint, this protocol also involves the patient passively flexing and actively hold the fingers in the palm by gently contracting the muscles to hold the digits in the fist position and for differential gliding of the digit’s individual PIP passive placement and active holding. At 3 weeks, gentle tenodesis exercises are begun out of the splint. Active composite flexion exercises without the splint are initiated at 4 weeks as well as differential tendon gliding exercises. The splint is discontinued at 6 weeks with initiation of passive extension exercises. At 7 weeks, composite passive extension is started. Light strengthening is allowed at 8 weeks and normal activities at 12 weeks.
Cast immobilization is necessary in children younger than 10 years of age due to lack of compliance with motion protocols.
OUTCOMES
Several outcome assessment tools have been described to analyze flexor repair results. The first was the Boyes outcome scale that judged results based on finger tip flexion measurement from palm with poor being >6 cm, fair 4 to 6 cm, good 2.5 to 4 cm, and excellent 0 to 2.5 cm. Then, the American Society for Surgery of the Hand (ASSH) flexor outcome was popularized, which defined outcome based on total active motion minus extension deficit. In the ASSH outcome, measurement of less than 50% (130°) is considered poor, greater than 50% (130°) fair, greater than 75% (195°), and good and excellent as normal or 260°. But probably the most accurate assessment tool is the Strickland Modification of the ASSH which only considers motion of the distal interphalangeal motion and PIP motion as the digital flexors are not the primary metacarpophalangeal flexor. In the Strickland Modified outcome assessment scale poor is 0% to 24% motion (<44°), fair is 25% to 49% motion (44° to 87°), good is 50% to 74% motion (88° to 131°), and excellent is 75% to 100% motion (>132°).
COMPLICATIONS
Adhesions
Dissection is minimized to prevent long segments of tendon ischemia that could result in adhesions. Early motion is instituted as soon as possible to reduce the risk of adhesion development. Also, cast immobilization can increase the risk of adhesion formation. Tenolysis procedures can be considered for compliant patients who can follow early active motion therapy programs at 22 weeks post-repair. This allows for plateau of function with therapy and minimizes the risk of repair site rupture with the tenolysis procedure. Moreover, if patients have stiff joints, these are addressed by passive range of motion exercises before the tenolysis procedure. Post tenolysis patients have significant pain and can benefit from indwelling catheter or regional blocks to permit therapy.
Rupture
Failure of the repair is often due to suture or knot rupture. Flexor pollicis tendons are the most likely to rupture. Therefore, it is critical to use strong suture and secure knots. Furthermore, use of a grasping technique like the MGH may resist rupture even if the knots slip. The strength of the repair decreases up to 50% between the first and third weeks after repair if the tendon is not stressed. Less decrease in strength is noted after early stress to the repaired tendon. Tendon rupturing may be lessened with early therapy and loading of the repair. Also, rupture can be from noncompliance with splint and therapy. If the repair ruptures early, the tendon can often be re-repaired. If the patient presents late, grafting may be required.
Rupture can also complicate tenolysis procedures, which necessitates grafting and must be discussed with the patient preoperatively.
TREATMENT OF LATE FLEXOR TENDON INJURIES
Flexor tendon grafting may be required in the late treatment of flexor tendon injuries, including after late rupture of the flexor tendon repair, rupture after tenolysis, or delay in treatment after flexor tendon injury. Flexor tendon grafting can be performed in a single stage or in two stages in which the first stage involves placement of a silicone rod, pulley reconstruction, and joint contracture release. Single-stage tendon grafting can be considered for tendon deficits in zones 3, 4, and 5. For coaptation of the tendon graft to the proximal and distal ends of the tendon, the interweave technique is preferred because it has been shown to be the strongest in biomechanical studies. Two-stage tendon grafting is recommended when patients require tendon grafting in conjunction with pulley reconstruction or joint contracture release. Two-stage grafting is also recommended if collapse of the sheath or excessive scarring is encountered at the time of tendon grafting or if soft tissue reconstruction is required over the graft.
Several donor tendon site options are available: the palmaris, plantaris, extensor digitorum longus, extensor indicis proprius, and extensor digiti minimi. Selection of a tendon graft is based on the length requirement and the number of tendons requiring graft reconstruction. The palmaris longus provides 16 cm, or sufficient length to graft from the palm to the fingertip. If more graft is needed, lower extremity donors can provide 30 to 35 cm. The palmaris is generally the preferred graft because it is in the same operative field and provides sufficient length. The technique of harvesting a tendon involves dividing the tendon distally and pulling the tendon through a tendon stripper (Brand), which releases the tendon from the muscle substance. The palmaris longus is absent in 15% to 25% of patients. Presence of the palmaris longus can be determined by asking the patient to oppose and flex the wrist against resistance. Another potential upper extremity donor is the injured flexor digitorum superficialis. When multiple tendon grafts or one long tendon graft from the wrist to the fingertip is required, the longer lower extremity donors are useful. The plantaris provides 35 cm of tendon but is absent in 7% to 20% of patients. The plantaris is located anterior and medial to the Achilles tendon. If the plantaris and palmaris are absent, the extensor digitorum longus from the second, third, and fourth toes can provide multiple segments of the tendon 30 cm in length. The extensor digitorum longus is harvested through an incision over the metatarsophalangeal joint. These tendons, however, can be fused at the ankle level, thus necessitating a second incision.
FIGURE 77.7. Two-stage tendon graft procedure with initial pulley reconstruction over a silicone rod (A). At the second stage, the silicone rod is replaced with a tendon graft (B, C). After completion of the distal juncture repair over a button, the proximal tendon is repaired with interweave technique to set the proper tension across the graft (D). Postoperative photos demonstrate the recovery of full composite grip, differential flexion, and full extension (E). © Bradon J. Wilhelmi, MD.
At the first stage of two-stage tendon grafting for zone II reconstruction, the sheath is exposed with mid-longitudinal incisions to minimize the risk of silicone rod exposure. The flexor digitorum profundus can be used as the motor unit and is generally identified just proximal to the A1 pulley because it is held there by the origin of the lumbrical. The distal part of the flexor digitorum profundus is preserved to suture to the silicone rod and the tendon graft in the first and second stages, respectively. Alternatively, the flexor digitorum superficialis can be used as the motor unit to avoid the potential risk of tendon imbalance with quadriga or a lumbrical-plus posture. The distal end of the flexor digitorum superficialis is preserved to adhere to the flexor canal to prevent PIP joint hyperextension. If the PIP joint already hyperextends, the flexor superficialis tail can be tenodesed to the flexor canal to treat the hyperextension. Joint contractures should be released at the first stage. The distal portion of the silicone rod should be secured distally and left free proximally to prevent the rod from being pulled or migrating from the appropriate position. Pulley reconstruction should be performed at the first stage over the silicone rod. Of the various techniques described, the encircling repair technique with a tendon graft has been shown to be the strongest. In this technique, the tendon graft is passed circumferentially around the silicone rod and proximal phalanx volar to the extensor for the A2 pulley, and dorsal to the extensor for the A4 pulley. For reconstruction of the pulley system of the thumb, the oblique pulley has been shown to be the most critical.
The second stage should be performed at 3 months to allow for development of a pseudosheath. Radiographs can be obtained to confirm appropriate positioning of the rod. After limited proximal and distal incisions, the tendon graft is sutured to the rod proximally and pulled distally, and the graft is left in the pseudosheath. Of the various distal juncture techniques, repairing a tendon directly to another tendon has been shown to heal most reliably. The distal juncture can also be repaired with a pull-through suture through the sterile matrix of the nail bed and nail plate over a button. The proximal end of the tendon graft is repaired to the motor unit with the interweave technique, which allows for size discrepancy and tendon balancing 1 cm tighter than cascade to allow for tendon stretching. This technique also allows for setting the appropriate length of the tendon graft. If the tendon graft is too short, quadriga and weakened grip can result. If the tendon graft is too long, a lumbrical-plus posture results with paradoxical hyperextension of the PIP joint on attempted finger flexion. These potential complications can be avoided by using the proximal flexor digitorum superficialis as the motor unit to avoid quadriga and lumbrical-plus posture. Immediately after the second-stage operation, early active motion can be initiated with passive flexion and active hold exercises. Patients can begin active flexion exercises at 4 weeks postoperatively. At 6 weeks, the dorsal blocking splint can be discontinued. The patient is allowed to participate in regular activities at 12 weeks (Figures 77.7A–E).
Possible complications of tendon grafting include adhesions, infection, rod exposure, synovitis, and rupture and tendon imbalance.
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