➢ The treatment of flexor tendon laceration has 3 major phases: initial evaluation with referral to an appropriate surgeon, operative treatment, and postoperative hand therapy.
➢ The initial provider must perform a comprehensive history and physical examination, including evaluations of tendon function, neurological function, and the vascular viability of the injured digit.
➢ Operative repairs of flexor tendon injuries are best done as soon as reasonably possible with use of a variety of acceptable anesthetic options, suture configurations, and postoperative therapy protocols.
➢ It is necessary to have a complete and interactive team—patient, surgeon, and therapist—in order to obtain the best possible outcome following flexor tendon laceration.
Flexor tendon lacerations are uncommon, with a reported prevalence of 6 per 100,000 acute hand injuries1. Sterling Bunnell, the founder of hand surgery specialization2, recognized the challenges of flexor tendon repair and recommended against primary flexor tendon repair in what he termed “no-man’s land,” now referred to as “zone II” (Fig. 1)3. This region, where both the flexor digitorum profundus (FDP) and flexor digitorum superficialis (FDS) tendons travel within the flexor tendon sheath, is the most challenging location for flexor tendon repair. Nevertheless, with advances in our understanding of the biology of tendon-healing, there has been a paradigm shift such that primary tendon repair is now routine4. Successful results require more than just a skilled surgeon; a committed team approach is paramount, with the goals of treatment being to restore independent tendon function and to achieve as much total active motion of the injured digit as possible. All members on this team are critical: the patient, the initial provider, the surgeon, and the therapist. All members must work in concert for an optimum result to be achieved.
A 27-year old, right-hand-dominant man sustained a laceration to the volar aspect of the right ring finger while towel-drying a knife after cooking. He was no longer able to actively flex the finger at the interphalangeal joints and had profuse bleeding. He was initially seen in the local emergency department, where it was determined that the FDP and FDS tendons had been lacerated. The neurovascular status of the finger was intact. The wound was irrigated and sutured, and the patient was referred to a hand surgeon for additional treatment.
Historically, flexor tendon repair has been considered to be a surgical emergency. While the optimal timing of surgical repair has not been conclusively demonstrated, most surgeons recommend early repair1,4-6. Gorriz and Cooke, in an avian model, found that primary repair within 24 hours after the injury was associated with the best result7. Those authors also reported that repairs performed between 4 and 7 days after the injury had inferior results compared with those performed ≤24 hours or >10 days after the injury, suggesting that there may be a detrimental window in the timing of surgery7. Those results have not been demonstrated in humans; however, at some point after the injury, primary repair may no longer be possible because of myostatic shortening and tendon degeneration. As such, recognition of the injury is paramount.
The initial evaluation of a patient with a flexor tendon laceration is often performed by an emergency-care provider in either an emergency room or an urgent-care facility. The diagnosis is typically made on the basis of clinical evaluation and judgment as imaging studies are not useful. It is critical to ensure that the vascular supply to the digit is intact in order to maintain the viability of the finger. The vascular supply can be assessed by examining the capillary refill in the nail bed, with use of a handheld Doppler monitor, or by means of pulse oximetry. Documentation of digital nerve function with use of 2-point discrimination should follow. On visual inspection, loss of the normal resting finger cascade alerts the examiner that flexor tendons have been lacerated. In addition, the inability to actively flex the distal interphalangeal (DIP) or proximal interphalangeal (PIP) joints in isolation, loss of the normal wrist tenodesis effect, and the lack of finger flexion with forearm compression confirm the diagnosis1,5.
Before the patient is referred to a hand surgeon, the laceration should be properly irrigated. Easily identified foreign material should be removed. Recent tetanus vaccination should be verified and updated if required. Antibiotics may be given to patients with highly contaminated wounds or those who are immunocompromised, but the need should be assessed on a case-by-case basis. The wound can be loosely repaired or left open. A clean dressing should be applied, and follow-up with a hand surgeon should be expedited for prompt surgical exploration and repair.
Ideally, the hand surgeon evaluates the patient soon after the injury in order to confirm the diagnosis and to assess for concomitant injuries that may alter treatment or impact outcomes, such as flexor pulley lacerations, neurovascular injuries, or bone and joint injuries. In addition, the surgeon will discuss operative repair and the necessity of postoperative therapy and will assess the patient’s ability to understand and comply with the entire process. Smoking cessation should be encouraged as tobacco use has been associated with poorer outcomes5,8.
It is important for the patient to understand that he or she is an integral part of the team and will have an important impact on the overall success of treatment. Refusal of the patient to participate can lead to poor outcomes, with results similar to those of nonoperative treatment (i.e., a stiff digit with no active motion). Although we are not aware of any published study that has definitively delineated an end point by which primary repair is no longer feasible, delay in repair beyond 14 to 21 days can lead to the need for flexor tendon grafting, complicating the procedure and reducing the likelihood of a good outcome. Once the surgeon and patient have agreed to proceed with surgery, there are numerous decisions that the surgeon and patient must make regarding anesthetic and intraoperative options.
There are 3 main anesthetic options: regional anesthesia, general anesthesia, and local anesthesia. The choice ultimately will depend on surgeon and patient preference in accordance with institutional policies.
Regional anesthesia, such as a supraclavicular or axillary block, is a very attractive option for flexor tendon repair. The advantages of regional anesthesia include reduced sedation requirements, no need for intubation, the ability to use a tourniquet to create a bloodless operative field, and reduced recovery time in the postoperative care unit. Disadvantages include the possibility for iatrogenic neurological injury, pneumothorax, neurological irritation secondary to hematoma around the nerve sheaths, and incomplete surgical analgesia, necessitating conversion to general anesthesia9,10.
Intravenous regional anesthesia, now commonly referred to as “Bier block” anesthesia, is another option. Bier blocks have many of the same advantages as peripheral nerve blocks; however, the main disadvantage of using a Bier block for flexor tendon repair is operative time. In general, patients are only able to tolerate the tourniquet for about 30 to 45 minutes. If surgery takes longer, either supplemental sedation or general anesthesia is needed for the patient to remain comfortable and motionless. Furthermore, once the tourniquet is released, the anesthetic effect is lost within 15 minutes. In some instances, a Bier block is ineffective for producing surgical analgesia and patients therefore ultimately require general anesthesia9,11.
General anesthesia is another option for flexor tendon repair and typically is used when patients are not candidates for other methods of anesthesia. General anesthesia is advantageous in that intraoperative patient discomfort is not a factor. The disadvantages include the need for the patient to recover in the postoperative care unit, the postoperative effects of the anesthetics used, and the inability of the patient to cooperate with the surgeon to evaluate the quality of the repair intraoperatively9.
While many surgeons are not comfortable using local anesthetics in isolation, a new method, termed “wide-awake local anesthesia no tourniquet (WALANT),” was recently developed12. WALANT is gaining acceptance because of its ease and effectiveness. Tourniquet use is supplanted by vasospasm that is induced 25 to 30 minutes following injection of 1% lidocaine with epinephrine 1:100,00012,13. Until recently, surgeons were admonished not to use lidocaine with epinephrine for hand surgery because of early reports of digital necrosis12. The root cause of digital loss was not ischemia secondary to epinephrine but rather low pH of the procaine solution; however, this fact was ignored. Lalonde and Martin demonstrated that critical ischemia was never generated with WALANT12. The advantages of WALANT include no requirement for an anesthesiologist to be present, no need for intravenous access, no need for sedation, and no need for the patient to recover in the postoperative care unit. Perhaps the greatest benefit of WALANT is that the patient, who is a critical part of the team, can actively participate in the evaluation of the quality of the repair at the time of surgery. The drapes are lowered and the patient flexes and extends the operatively treated finger, allowing the surgeon to evaluate tendon gliding, the strength of the repair, and any gapping at the repair site. Both the patient and the surgeon can assess the total range of motion14. The patient can immediately see the results and can gain an understanding of how to appropriately participate in postoperative therapy14. The postoperative rehabilitation instructions, requirements, and restrictions become obvious at that moment. The potential results of surgery with compliance with the postoperative regimen are clearly evident to both the surgeon and the patient14. The patient is instantly transformed into an active member of the team.
A variety of surgical incisions can be used, with incorporation of the traumatic laceration if possible. A thorough irrigation and debridement of devitalized or infected tissue should follow. The FDP and FDS tendons are then inspected. Within zone II, the FDP is more commonly lacerated, although both the FDP and FDS may be transected1. Partial lacerations involving up to 50% to 60% of the tendon width may be debrided to prevent triggering and adhesion formation. A single slip of FDS also may be excised if needed5 (Fig. 2). The pulleys must also be evaluated (Fig. 3). While the A2 and A4 pulleys are particularly important for tendon function, with many surgeons considering them critical1,15, recent evidence has indicated that complete division of the A4 pulley and up to 50% release of the A2 pulley are acceptable and may lead to improved tendon excursion following zone-II flexor tendon repair1,15.
Numerous techniques are available for flexor tendon repair. Chauhan et al. provided an extensive review of the technical differences in techniques16. Regardless of the technique used, the goals of the repair are secure suture placement, smooth end-to-end tendon apposition, no gapping at the repair site, minimal disruption of tendon vasculature, and a strong-enough construct to foster early motion1,5.
A variety of suture materials are available. The ideal suture is non-reactive and non-inflammatory; is strong; is of small caliber; and has good handling characteristics. Barbed sutures have shown some promise, although they have not been widely used17,18. Typically, a core suture and a circumferential epitendinous suture are utilized. Ideally, core sutures are placed 7 to 10 mm from the zone of injury and cross the repair site in an intratendinous manner. Strickland and other investigators have demonstrated that ≥4 core strands crossing the repair site are ideal6,19,20. During healing, the strength of the tendon repair decreases within the first 1 to 3 weeks after surgery. Thus, having more suture strands crossing the repair site can maintain the tendon ends in apposition while the tendon heals21. Although the number of strands crossing the repair site has been shown to correlate directly with the overall strength of the repair, the configuration of core strands has the greatest impact on the eventual tensile strength5. A running epitendinous suture can increase the strength of the repair by an additional 10% to 50%5,6,22,23; such suturing typically is performed with a 6-0 monofilament material and is placed approximately 2 mm from the repair site to a depth of 25% of the tendon diameter. This stitch also gives the repair site a neat appearance, decreases the cross-sectional area, and improves tendon gliding resistance. The use of an epitendinous suture has been shown to decrease the reoperation rate following flexor tendon repair by up to 84%24.
Following tendon repair, the repair strength and gliding should be assessed with the patient on the operating table. If the patient is awake and able, he or she may be asked to actively flex the involved finger. If the patient is unable to participate, wrist extension and/or forearm compression can be used to assess the tendon repair site. Any gapping, entrapment, or knot resistance must be addressed at this time to maximally improve tendon gliding within the flexor tendon sheath.
The goal of hand rehabilitation after flexor tendon repair is to promote optimal tendon gliding in order to restore functional range of motion25. Communication between the surgeon and the hand therapist is critical to determine the postoperative rehabilitation program26. Important information that is shared includes the strength of the repair, the condition of the tendon, the status of the pulleys and nerves, the presence of any associated injuries, and the quality of intraoperative gliding of the repaired tendon.
The first postoperative visit with the hand therapist occurs at an average of 1 to 3 days after surgery27 and includes the assessment of pain, wound integrity, edema, joint stiffness, other medical conditions, the patient’s understanding of the injury, and the support system. Other factors determining the choice of rehabilitation program include the timing of referral, patient access to therapy, therapist experience, insurance coverage, and the potential for noncompliance28.
At the initial visit, an orthosis is fabricated in a position to reduce tension on the tendons and nerves and to allow early mobilization. A common protocol for zone-II repairs involves the use of a dorsal block orthosis positioning the wrist in 0° to 20° of flexion, the metacarpophalangeal (MP) joints in 40° of 70° of flexion, and the interphalangeal (IP) joints in full extension. The orthosis can include thumb immobilization to avoid functional hand use.
There are 3 main rehabilitation methods following zone-II flexor tendon repair: full immobilization, early passive motion, and early active motion. Early-mobilization protocols provide superior results over immobilization by inhibiting adhesions, promoting intrinsic healing, and preventing a decrease in tensile strength29. Gelberman et al. demonstrated that healing tendons responded favorably to controlled stress30. Boyer et al., and others later, showed that 1.7 to 3.5 mm of tendon excursion could prevent adhesion formation1,31,32. As such, full immobilization is reserved only for special cases.
Immobilization with use of a cast following flexor tendon repair is typically reserved for noncompliant patients, particularly young children under the age of 6 years33. A long-arm cast is usually preferred, and the duration of immobilization is typically 3 to 4 weeks34. Immobilization exceeding 4 weeks has been associated with the deterioration of digital function35. An issue that has arisen in pediatric patients has been repair rupture within the cast due to inadvertent digit flexion34,36. A proposed solution involves injecting botulinum toxin into the flexor muscles to induce temporary muscle weakness and to aid with patient compliance during rehabilitation37. Overall, differences in postoperative rehabilitation have been shown to play a minimal role in the recovery of digital function in pediatric patients38. It has been suggested that children exhibit superior recovery because of better vascular supply and a greater capacity for the remodeling of scars and adhesions39.
Early Passive Mobilization
The Kleinert40 and Duran41 protocols are 2 of the most common early passive-motion rehabilitation protocols28. The Kleinert protocol involves active finger extension and dynamic splint-assisted passive finger flexion40. During the first 3 weeks, a dorsal blocking splint holds the wrist and the MP joints in flexion. Rubber-band traction is applied from the wrist to the fingernail, and the patient is directed to actively extend the digits to the limits of the splint while allowing the rubber band to passively flex the digits. The Duran protocol involves active finger extension and patient-assisted passive flexion41. A dorsal blocking splint is applied to the wrist and digits to keep them in flexion. These exercises are performed every 2 hours, with 10 repetitions of each. Passive motion should be applied gently and slowly to allow the wound to gain full strength and to avoid excessive soft-tissue tension1.
The Washington protocol42 is a proposed combination of the Duran and Kleinert methods in which a Kleinert dorsal blocking splint is utilized and active extension exercises are completed with the assistance of a therapist42,43. Variations of the combined method have been shown to be associated with lower tendon-rupture rates when compared with the Kleinert and Duran protocols individually44.
Early Active Mobilization
Early active-mobilization programs have been gaining popularity for appropriate patients as they have been associated with improved tendon-healing, reduced complications, and enhanced functional outcomes8,25. This type of program requires an ideal candidate with at least 4-strand core sutures and an epitendinous repair, minimal edema and joint stiffness, an appropriate level of understanding of the recovery process, and a willingness and ability to comply with the program45.
Early active mobilization consists of place-and-hold therapy, controlled active motion, or a combination of both. With place-and-hold therapy, the fingers are passively placed into a partial fist and the patient holds the position with gentle active contraction. With controlled active motion, the patient actively flexes the fingers, initiating from the DIP joint, to a specific percentage each week, or to no more than 50% of full digital flexion for the first 3 weeks25. A partial fist places less stress on the repair than a full fist does25. The initiation of motion from the DIP joint helps to improve FDP and FDS gliding. The patient performs this exercise 5 to 10 times every 2 hours while wearing the splint. Before active flexion exercises, the work of flexion needs to be minimized by decreasing the resistance of a stiff and edematous finger25. Therefore, passive range of motion always precedes active range of motion. Edema is managed with strict elevation and compressive wrap. Wrist tenodesis can be added under the guided instruction of the therapist.
Early active mobilization programs involve the use of a dorsal block orthosis that positions the wrist in neutral to reduce the work of flexion with active contraction. The MP joints are in slight flexion to facilitate FDP gliding initiated from active DIP flexion. Removal of the orthosis or lateral pinching against the orthosis can occur; therefore, education should include precautions during wound or skin care and techniques for performing 1-handed tasks.
The first few weeks are critical in any early-motion protocol. The therapist needs to continually reassess and make program changes based on the presentation of the patient and the stages of wound-healing. Scar massage is added once the incision is well healed. A silicone gel sheet may be used to soften the scar for improved joint mobility.
At 3 weeks postoperatively, early passive mobilization and early active mobilization programs are progressed. The wrist is brought to neutral or slight extension in the orthosis. With early passive motion, the patient first progresses to place-and-hold therapy and then to an active composite fist. With early active mobilization, the patient works toward achieving a full fist. The patient continues with passive range of motion prior to active range of motion to minimize the work of flexion25.
At 4 weeks, the patient may remove the orthosis to perform home exercises, including wrist tenodesis and tendon glides (full-fist, hook-fist, and bringing the hand into intrinsic plus position)46. Purposeful motion such as gently grasping a tissue in the palm may facilitate less effort with flexion. Passive intrinsic stretches are also added. A comparison of passive and active ranges of motion determines true tendon glide. Therapy for an adherent tendon can be progressed, whereas a free-gliding tendon requires further protection within a splint and the avoidance of resistive exercises.
At 5 to 6 weeks, if the patient has been unresponsive to active tendon glide exercises, he or she can progress to blocking exercises and can add light resistive exercises such as gentle fist formation around a soft sponge and crunching of a towel. DIP blocking of the small finger may be avoided because of the risk of rupture. The patient can begin light functional use of the hand. PIP joint flexion contractures are managed with night-time extension splinting, gentle passive PIP joint extension stretches, and blocked PIP joint extension exercises. By 6 weeks, the dorsal block splint is generally discontinued, with the continued avoidance of heavy gripping.
After 6 weeks, resistive exercises with use of graded resistive putty or sponges and fist formation around various media and dowels are added. Functional tasks are upgraded.
Therapy continues to focus on upgrading exercises and function in order to improve strength and tendon gliding, addressing joint contracture through splinting, and scar management. Grip-strength testing should not be done until 12 weeks postoperatively. The patient typically is discharged from formal hand therapy by 3 months postoperatively, returning to full use without precautions.
Over the past few decades, tremendous progress has been made in terms of improving the outcomes following flexor tendon injury. A recent meta-analysis demonstrated a 6% reoperation rate, a 4% rerupture rate, and a 4% adhesion formation rate24.
PIP joint flexion contracture is another relatively common complication following zone-II flexor tendon repair. This finding can be addressed with protected extension exercises and/or the placement of a finger orthosis under the initial dorsal block orthosis. If the joint is unresponsive to static splinting and exercise, daytime dynamic PIP joint extension splinting can be added. The use of a blocking orthosis or a yoke splint to help improve IP flexion and PIP extension can be considered. PIP joint contractures may require extension splinting for a year or longer.
Clinical Scenario Revisited
After discussing the nature of the injury and surgical options, our patient ultimately opted for flexor tendon repair. The following day, he underwent surgery with use of the WALANT technique. The procedure was performed through a Bruner incision47 incorporating the preexisting laceration, with exposure of the flexor tendon sheath from the pulp of the fingertip to just proximal to the distal palmar crease.
The tendon lacerations had occurred through the A2 pulley. The FDP had retracted into the palm with rupture of the vinculum, and the FDS was 90% lacerated through the chiasm of Camper.
The FDP tendon was retrieved proximal to the A1 pulley, a 4-0 nonabsorbable looped suture was placed through the tendon, the A1 pulley was released, and the tendon was brought back through the A2 pulley. A window was created in the C1-A3-C2 pulley complex to allow for repair of the tendons. The partially lacerated ulnar slip of the FDS was sutured with a locked cruciate technique with use of a 4-0 nonabsorbable braided suture, and the completely transected radial slip was excised to allow for better gliding with less bulk. The distal part of the FDP tendon was delivered from underneath the A4 pulley by hyperflexing the DIP joint. Both ends of the tendon were carefully freshened and repaired with use of a locked, 4-strand cruciate core suture and a 6-0 epitenon repair.
The patient was then asked to flex and extend the ring finger. The repair did not gap; however, the tendons were noted to bind at the distal edge of the A2 pulley, preventing full composite flexion. The patient was able to fully extend the finger. The distal 30% of the A2 pulley was then resected in order to allow full composite finger flexion. The window in the tendon sheath was not repaired, the wound was irrigated copiously, the incision was closed with 5-0 sutures, and the patient was managed with bulky fluff dressings and a dorsal blocking splint.
The patient was referred to the hand therapist 3 days later, and an early active protocol was begun after the surgeon discussed the case with the therapist. The patient and the therapist met weekly to monitor progress. The surgeon removed the sutures at 12 days. By week 5, the dorsal blocking splint was removed, and the patient was encouraged to continue working on range of motion. At 4 months, the patient had a nearly full composite range of motion and the grip strength had nearly returned to the preinjury level.
The case of our patient represents the progress that has been made in the treatment of flexor tendon lacerations over the past few decades. With a conscientious team approach, an excellent clinical result can be achieved.
Investigation performed at The University of Vermont College of Medicine, University of Vermont Medical Center, Burlington, Vermont
Disclosure: There was no external funding source. The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article.
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