Flexor Tendon Reconstruction

All fractures should be healed in anatomic alignment

Wounds must have healed with soft, stable scars and skin cover

Joint contractures have been mobilized to near normal passive ROM

Tendons systems should be intact Muscle strength should be good

Muscle strength should be good

The patient is compliant and motivated

An experienced hand therapist should be available

Preceding tenolysis, at least 3 months of intensive hand therapy is recommended to obtain as much passive ROM as possible. As long as hand therapy improves ROM, tenolysis should be postponed. If no progress has been seen during the previous 4–8 weeks, tenolysis can be planned [11]. Tenolysis earlier than 3 months after primary flexor tendon repair or tendon grafting is considered potentially dangerous to tendon blood supply. This could put the tendon at risk for rupture during postoperative hand therapy exercises [12].
Any additional procedure that requires postoperative immobilization such as tendon grafting, free skin grafts or corrective osteotomies should not be planned concomitantly. In these cases reconstruction in multiple stages is advised.
Ideally, flexor tendon tenolysis is performed under local anesthesia with intravenous analgesia and a sedative [13]. Active involvement of the patient is helpful to fully judge the active ROM of the digit when the tendons have been freed of adhesions. Additional tenolysis at a more proximal or distal level may be required if ROM is still found to be limited. Another advantage of local anesthesia is that the patient can directly observe the progress made during the procedure. This helps the patient’s motivation to preserve the results during the postoperative hand therapy program [6]. If the procedure will take longer than 1 h or the patient does not tolerate the local anesthesia with sedation, general anesthesia or axillary block should be used.
Azari et al. described a step by step technique of flexor tendon tenolysis [6]. First, wide exposure of the entire flexor tendon sheath is obtained by Bruner type zigzag incisions or a mid-lateral approach. The flexor tendon is exposed proximally and distally to reach unaffected tissue. Then, both the flexor tendons are freed en-bloc from their surroundings proceeding from an unaffected area through the affected area. The pulley system, especially the A2 and A4 pulleys, is carefully spared as far as possible. Access to the tendons can be obtained through minimal transverse windows in the cruciate pulleys or, if need be, by sacrificing the A3 pulley [14]. Specially designed tenolysis knives are available to get to adhesions under the pulleys that are otherwise difficult to reach (Fig. 4.1).
When the flexor tendons have been freed from the tendon sheath, adhesions between the FDP and FDS tendons should be addressed by separating the tendons from one another [6]. If the tendons appear very frail or heavily scarred, the tenolysis procedure is stopped and one- or two-stage tendon reconstruction should be considered.
All adhesions are dealt with until the tendons glide adequately. At this stage, the patient can be asked to actively flex and extend the involved digits to assess the gliding. If the patient has general or axillary block anesthesia, gliding of the freed tendons can be assessed by the “traction flexor check”, as proposed by Whitaker et al. [15]. In this maneuver, proximal traction on the involved tendons through a palmar or volar distal forearm incision is used to flex the digit passively (Fig. 4.2). Additional tenolysis may be required if tendon gliding is still unsatisfactory.
Several techniques have been tried to prevent adhesion formation after tendon surgery. Local deposition of steroids at the end of the procedure has been suggested, but has also been hypothesized to have adverse effects on tendon healing [6]. Various interposition materials have been tried experimentally and clinically from as early as the 1940’s. Materials included silicone sheets, gelatin sponge, and more recently Seprafilm, hyaluronan gel or hydrogel containing biocompatible phospholipid polymer [16–18]. Most however, prefer the use of early active mobilization programs to prevent tendon adhesions [19]. As early as the same day of tenolysis, hand therapy can be initiated. The hand therapist should be advised on the peri-operative findings so therapy can be adjusted to the individual patient’s needs.

Fig. 4.1

A tenolysis knife is used to disrupt adhesions under the pulleys that are otherwise difficult to reach

Fig. 4.2

The traction flexor check. To assess the presence of remaining adhesions, proximal traction on the involved tendon through a volar distal forearm incision is used to passively flex the digit

Outcome

In most, carefully selected patients, improvement of ROM after flexor tendon tenolysis is to be expected. Complete, unrestricted ROM however, is infrequently obtained. In 1989 Jupiter et al. reported an increase of ROM from 72 to 130 ° after tenolysis in replanted fingers [20]. In a series of 72 patients with flexor tendon tenolysis, Foucher et al. obtained an improvement in active ROM from 135° to 203° in 84 % of the fingers and from 65° to 115° in 78 % of the thumbs [21]. Tenolysis also improved ROM with 107 ° in a series of patients with flexor tendon adhesions after a phalangeal fracture [22]. More modest results were obtained in 19 patients with zone II flexor tendon adhesions, reported by Riccio et al. In this group tenolysis improved ROM by 28 % [18].

Complications

Tenolysis does not always improve digital function. In one series the large majority of patients had benefit of tenolysis, but no change or reduced ROM was observed in 16 % of the fingers [21]. So insufficient effect, or deterioration due to surgery are complications that need to be considered. The main cause for these complications is recurrence of adhesions again emphasising the importance of early postoperative active mobilization programs.

Tendon rupture is another known complication of tenolysis. In a series of 23 patients, flexor tendon rupture occurred after tenolysis in 16 % of the cases [23].

Other, less specific complications after tenolysis include would healing problems, cold intolerance or neurovascular injury. These complications are mainly due to the repeated surgical insult to the already compromised digit. Careful patient selection to meet the above mentioned selection criteria can avoid these problems.

One- and Two-Stage Tendon Reconstruction

Background

Potential candidates for flexor tendon reconstruction can present early or late. A patient seen immediately after injury has a completely different subset of problems to be addressed than a patient presenting weeks or months after the initial injury or after undergoing earlier surgical attempts at tendon repair.

In acute cases, crush or blast injury is often the cause of a mangled digit or hand. Injuries are often extensive and involve multiple digits, levels or soft tissue structures. This often makes primary tendon repair impossible. In these cases, problems such as inadequate soft tissue cover, infections or fractures need to be dealt before the flexor tendons can be reconstructed.

Patients that present late usually had less extensive initial injuries. Their causes of functional problems include tendon bed scarring, adhesions, joint stiffness or trophic changes due to associated nerve injury. Alternatively, impairment of flexor tendon function recurred after earlier attempts at primary repair. In these secondary cases, tendon adhesions, failure of the tendon repair or both require attention.

The classification system published by Boyes in 1950 is a useful tool in surgical planning, Table 4.1 [24]. In the most favorable cases, a single involved digit is in otherwise optimal condition (Grade 1). Presence of scar tissue renders the case more complicated (Grade 2). Stiffness of the interphalangeal joints requires additional hand therapy or capsulectomy (Grade 3). Associated digital nerve damage causes trophic changes making successful functional outcome less likely (Grade 4). Finally, “multiple damage” can be interpreted in two ways: multiple injured fingers or multiple lesions (e.g. bone, skin and neurovascular injury) in a single digit (Grade 5) [25]. In general, primary repair can be attempted in grade 1 injuries without significant delay. Tendon reconstruction in one or two stages should be considered in grades 2 to 5 [26].

Table 4.1

Boyes classification [24]

Grade	Condition
1	Minimal scar, mobile joints, optimal condition
2	Scarring
3	Joint damage/stiffness
4	Digital nerve damage
5	Multiple digits/lesions per digit

Tubiana has refined the indications for tendon reconstruction of injured digits since Boyes’ publication [25]. In addition to assessment of associated injuries, timing of presentation (early, intermediate or late) is also considered in the decision making process. According to Tubiana, the indication for one- or two-stage tendon reconstruction arises if (1) the case presents late and significant scarring is present, (2) an addressed associated fracture remains unstable, (3) there is inadequate skin cover or 4) in case of multiple injuries (i.e. nerve, bone, joint or skin). In the latter, outcome of tendon reconstruction is poor and salvage procedures such as arthrodesis or amputation should be considered.

In short, flexor tendon reconstruction should only be considered if issues of soft tissue cover, joint stiffness, bone injuries and neurovascular damage can be or have been adequately addressed. It is essential that functional, passive ROM is present or restored before tendon reconstruction procedures are initiated. Pulvertaft summarized these conditions for successful tendon grafting (See “Clinical pearls: Pulvertaft’s conditions for successful tendon grafting” below) [27].

Clinical Pearls: Pulvertaft’s Conditions for Successful Tendon Grafting

The involved hand is in overall good condition

There is no extensive scarring of the tendon bed

Passive ROM is (nearly) full

Circulation of the digit is satisfactory

At least one digital nerve is intact

The patient is cooperative

The state of the involved digit or hand cannot always be judged completely by history and physical examination alone. In the acute situation conventional radiography is often required, but there is no place for other diagnostic imaging modalities [12]. Imaging techniques such as ultrasound, CT or MRI can be helpful in secondary cases. It can be difficult to distinguish between a tendon rupture or adhesion formation after earlier flexor tendon repair. In these cases ultrasonography is a useful, non-invasive imaging technique [12]. CT is capable of detecting pulley ruptures. MRI is expensive, but superior in diagnosing flexor tendon problems such as adhesions, partial or complete tendon ruptures or pulley damage.

Surgical exploration however, remains the only method to fully assess the amount of scarring, presence and location of tendon adhesions, the state of the tendon sheath and the tendon stump. Based on physical examination, imaging and operative findings a definitive reconstructive plan can be made.

In all cases a clear understanding of the patient’s wishes, expectations and – very importantly – motivation, are of paramount importance when deciding if the patient is a good candidate for flexor tendon reconstruction. Thorough pre-operative counseling is needed to discuss the options, the potential results, risks and complications of all reconstructive efforts. A multi-disciplinary hand clinic is ideal to council patients seeking flexor tendon reconstruction. The involved hand surgeon and therapist can consult the patient together to guide decision making by all parties involved. Decisions should not be made hastily. If the patient has reservations or second thoughts, a follow-up appointment should be arranged for more counseling.

Flexor Tendon Reconstruction of Zone I Injuries

Presentation

In flexor tendon zone I, the FDP tendon is damaged distal to the insertion of the intact FDS tendon by avulsion from its insertion, laceration or failure of a previously performed primary FDP repair.

In 1977 Leddy and Packer categorized closed avulsion injury of the FDP insertion from the distal phalanx into three types [28]. A few years later, a fourth type was added [29, 30] (Fig. 4.3).

Fig. 4.3

Types I to IV avulsion injuries of the FDP insertion

Type I injury involves rupture of the FDP tendon from its insertion on the distal phalanx. Vinculae are also ruptured, allowing the tendon to retract into the palm. Rupture of the vinculae causes a hematoma in the flexor tendon sheath. If not treated urgently, fibrosis in the flexor tendon sheath and fixed muscular contraction make primary repair impossible.

Type II FDP avulsions are more forgiving. The tendon ruptures from its insertion, but the intact vinculae only permit limited retraction of the tendon to the level of the PIP joint. Hematoma formation is less pronounced and limited retraction is unlikely to cause fixed contraction of the muscle. Type II injuries are therefore often eligible for delayed primary repair with good results. Successful primary repair of type II injuries after 3 months delay have been described [31].

Type III lesions are much like type II injuries to the extent that retraction is limited and the vinculae remain intact. In these lesions, a bony avulsion fragment of the distal phalanx prevents tendon retraction into the flexor tendon sheath. Type III lesions are therefore also more often suitable for delayed primary repair.

In 1981 Smith suggested adding a type IV FDP avulsion injury. In this fairly rare type of injury not only does the FDP tendon retracts into the finger or palm bit it also ruptures from an avulsed bony fragment [30]. Other than the presence of a bony avulsion fragment, this is much like a type I injury and should be addressed in an urgent fashion.

In summary, flexor tendon grafting or two stage flexor tendon repair is usually indicated in type I and IV injuries. However, significant delay or associated injuries may require more this type of treatment in types II and III injuries.

Open lacerations of the FDP tendon in zone I have similarities to type II closed avulsion injuries; the FDP tendon usually remains tethered to its vinculae and retracts no further than the PIP joint or proximal phalanx.

Unfortunately, rupture of a previously repaired zone I primary tendon injury is not uncommon. If recognized within two to three days, ruptured primary tendon repairs can be successfully treated with a repeated attempt at primary repair. If delayed longer, one- or two-stage reconstruction should be considered.

Treatment

The indication for reconstruction of FDP function with an intact FDS remains controversial. The reasons for this debate are twofold.

Firstly, impairment caused by loss of FDP function is limited to inability to actively flex the DIP joint and reduced strength in the involved digit. It must be noted that particularly in the ulnar two fingers, loss of power grip can be quite restrictive. Also, active flexion of the DIP joint may be needed in particular cases (e.g. musicians). But if the DIP joint does not hyperextend during pinch and the patient does not have particular need for active DIP joint flexion, conservative treatment is a viable option. Alternatively, tenodesis or arthrodesis to stabilize the DIP joint are functionally valuable options.

Secondly, good outcome of FDP reconstruction with an intact FDS cannot be guaranteed. Some authors go as far as limiting reconstruction to patients of 10–21 years of age [32]. If the wish for reconstruction is outspoken, the patient should be clearly informed that results can be disappointing or, in some cases, may even be functionally worse.

Clinical Pearls

Isolated loss of FDP is often functionally unimportant
More conservative options: − no surgical treatment, tenodesis procedure or arthrodesis are usually more appropriate
Consider one-stage reconstruction in younger and well motivated patients

One Stage Tendon Grafting

One stage tendon grafting can only be performed if the flexor tendon sheath is intact, there is minimal scarring and joints are supple. The tendon graft chosen should be thin enough to fit in the flexor tendon sheath together with the intact FDS tendon slips. In the majority of cases, fingertip-to-palm grafts suffice for zone I FDP tendon reconstructions with an intact FDS. The palmaris longus tendon or the extensor digitorum communis tendon to the index finger have been reported to be suitable grafts [11]. These tendons have sufficient length for tip to palm grafting. Characteristics and harvesting technique of available grafts for one- or two-stage reconstruction are described later in this chapter.

Bruner type zig-zag incisions or a mid-lateral approach to the flexor tendon system is obtained. Choice of approach depends on preference of the surgeon and on pre-existing scars. The zig-zag incisions provide the best exposure, but the mid-lateral approach reduces the amount of scarring directly over the flexor tendon sheath [33]. Exposure of the flexor tendon sheath is obtained from the FDP insertion at the distal phalanx to the mid palm. Remnants of the FDP tendon should be excised from the fingertip to the lumbrical origins. If possible a 1 cm stump of the distal FDP at its insertion on the distal phalanx should be preserved for attachment of the graft. The annular pulleys should be spared as much as possible.

Ideally, the graft is threaded carefully through the chiasma of the FDS tendon. But the chiasma is often obliterated by scarring. If so, the graft can be routed around the FDS tendon slips. Under no circumstance should the functional FDS insertions be sacrificed. Some authors however, have suggested a resection of one of the FDS tendon slips [34]. This is usually considered unnecessary [35].

The distal junction of the graft to the distal FDP stump or distal phalanx should be fixed first. Multiple techniques for the fixation of the distal juncture have been described. If the distal FDP tendon stump is of sufficient length, a graft-to-tendon suture technique is used. Otherwise, graft-to-bone fixation is warranted [34]. The same techniques apply for fixation of the distal graft junction as described previously for primary flexor tendon repair. Options include pull-out sutures through or around the distal phalanx that place the tendon end into small transverse trough in the volar distal phalanx, or alternatively the use of a small bone anchor. The decision on which fixation to use is largely based on surgical preference. Pull out sutures have the advantage of being non-permanent. They also allow for accurate placement of the distal tendon end into the bony trough. If the sutures are placed through the nail plate, deformities of the nail may result. The bone anchor has de advantage of a strong fixation without the need of suture removal or the risk of nail plate deformities. The downside is the use of a permanent implant, which some surgeons prefer to prevent if possible.

Skin can be closed distally before the proximal juncture in the palm or distal forearm is made. This facilitates skin closure before tensioning at the proximal juncture places the digit into a flexed position.

Typically for zone I injuries, the FDP motor is still intact and its proximal tendon is available in the palm. Proximal fixation of a slender graft such as the plantaris or palmaris tendon can be done by interlacing the graft through the FDP tendon as described by Pulvertaft [36]. Care should be taken to place this fairly bulky connection sufficiently proximal to the A1 pulley to allow for unimpeded tendon gliding, if needed the A1 pulley can be vented to create additional gliding room (Fig. 4.4). Alternatively, an end-to-end juncture can be fashioned if the graft and FDP tendon are of similar caliber. If the proximal juncture is placed in the distal forearm, the Pulvertaft weave is recommended. With the wrist, MCP joint and PIP joint straight, tensioning of the graft should put the DIP joint in approximately 40° of flexion [35].

Fig. 4.4

The tendon graft is tunneled trough the flexor tendon sheath and attached proximally. If sufficient space is available, the attachment is made by interlacing the graft through the FDP tendon as described by Pulvertaft

Strickland recommends postoperative immobilization of the hand with a dorsal splint for 3.5 weeks [11]. More recently, others allowed for gentle short-arc active extension and flexion within the first postoperative week, supervised by an experienced hand therapist [19].

Two Stage Tendon Grafting

A two-stage tendon grafting procedure is needed if scarring of the flexor tendon sheath does not allow for supple gliding of the future graft. Also, if the A4 pulley needs to be reconstructed or a stiff DIP joint needs release, this can be done at the first procedure together with placement of a silicone rod.

Stage One

Exposure of the entire flexor tendon sheath is obtained from the insertion of the FDP tendon on the fingertip to the site of the planned proximal juncture in the palm or the distal forearm. Previous incisions must be respected to ensure viability of the skin flaps. The state of the sheath and FDS tendon are evaluated. Any scarring of the sheath or pulleys is excised. Joint contractures are released at this stage if needed.

The A4 pulley is reconstructed if it is considered dysfunctional and irreparable. The remainder of the FDP tendon is excised to the origin of the lumbricals in the palm. If possible, the distal 1 cm of the FDP at its insertion on the distal phalanx should be spared for attachment of the silicone rod and the tendon graft in the first and second stages respectively. Also, the (healthy) proximal end of the FDP can be sutured to the A1 pulley in the first stage. This maintains length and prevents retraction.

Depending on the planned future tendon graft and the available space, a properly sized silicone implant is threaded through the (reconstructed) pulley system and fixed to the distal FDP stump. If the distal FDP stump is not available through- or around-the-bone suture techniques or screw fixation of the silicone implant can be used [37].

If the plantaris tendon is to be used at the second stage, a 3 mm silicone rod will usually suffice [12]. A future palmaris tendon graft requires a larger size implant: 4–5 mm, but space is usually limited due to the proximally intact FDS tendon. The implant can be placed trough or around the chiasma of the FDS and threaded proximally enough into the palm to allow for unimpeded gliding of the proximal end. If the palm is scarred or the lumbricals are damaged, these should be bypassed by a longer silicone rod to the distal forearm. In the distal forearm the proximal end is placed between the FDS and FDP tendons. The proximal end of the silicone rod is left unattached. Free gliding of the rod must be tested before closure of the wounds. The proximal tendon end in the forearm can be marked with an non-resorbable monofilament suture to make subsequent identification easier during the second stage. The hand is covered in a bulky compressive dressing with the wrist in slight flexion.

After stage one, post-operative hand therapy is aimed to keep the joints supple and the tendon sheath open. Passive guided motion exercises are started at 7–10 days. After sufficient time for the soft tissues to heal and the pseudosheath to form, the second procedure is scheduled. This is usually 3 months after the first procedure.

Stage Two

In the second procedure, only minimal exposure of the silicone rod and the newly formed pseudo-sheath is necessary at the fingertip and at the site of the proximal juncture. Distally, the silicone rod is released from its insertion. The tendon graft can then be attached securely to the silicone rod and very gently pulled proximally trough the pseudosheath into the proximal wound. Characteristics and harvesting technique of suitable grafts are described later in this chapter. With the tendon graft in place, the rod is detached and discarded. The distal juncture of the graft is secured as described above before closure of the distal wound.

Attachment to the original FDP motor is preferred. The combined FDP motor of the third to fifth digit is usually available and in good shape if only one digit had been injured initially. The individual FDP motor of the second digit is often contracted if the palmar tendon and lumbricals have been excised at the first stage. Contracture can be prevented by attaching the musculo-tendinous juncture of the FDP motor of the second digit to the periosteum of the radius under tension at the first stage so the motor can be used in the future The alternative of attachment of a tendon graft of the second digit to the combined motor of the third to fifth FDP is preferred by most. Alternatively, the FDS can also be chosen as a motor to the tendon graft if multiple digits need to be grafted, or if the FDP motors are of insufficient quality.

Enough tension is placed on the graft at the proximal juncture to place the DIP joint in 40° of flexion with the PIP and MCP joints in extension and the wrist held straight. Tenodesis testing at wrist level ensures proper tensioning and cascade of the digits. Depending on the caliber of the graft and the motor tendon a Pulvertaft weave or end-to-end tenorrhaphy is used for the proximal juncture. At the end of the procedure, the hand is put in a bulky compressive dressing with the wrist in slight flexion, the MCP joints in approximately 70 ° of flexion and the interphalangeal joints in extended or slightly flexed position [35].

Early mobilization under supervision of an experienced hand therapist can be initiated in the first postoperative week. If the graft and junctures are not considered to be strong enough, immobilization for 3–4 weeks can be chosen [11]. This does increase the risk of adhesion formation [19].

Outcome

In 1988 Ipsen et al. published a series of one-stage tendon grafts through or around an intact FDS tendon [38]. They concluded that early mobilization is safe with only one tendon rupture in 25 cases. All but one had increased total ROM at long term follow up. On the other hand, six fingers lost an average of 16° of PIP joint flexion.

Older series of one-stage tendon grafting for isolated FDP lesions also reported favorable results [39, 40]. In 1969 Goldner et al. demonstrated good functional outcome but stressed that detailed preoperative assessment, meticulous surgical technique, careful selection of patients and surgical experience are necessary.

Wilsen et al. reported a series of delayed, two-stage tendon grafting in a series of twelve fingers with flexor profundus avulsions or lacerations. Total active motion improved 78°. Grip strength significantly improved in 8 of the 11 patients. One graft rupture occurred and in two cases secondary tenolyses were necessary [41]. Sullivan reported disappointing results of staged flexor tendon grafting for isolated FDP injuries. Only 7 of the 16 cases achieved satisfactory results [42].

Complications

Complications associated with repeated surgical interventions to the digits include skin flap necrosis, wound healing difficulties, scar contractures, cold intolerance and neurovascular damage. Careful selection of cases with the Boyes classification in mind reduces occurrence of these problems.

More specifically, damage to the intact FDS tendon or added scarring due to repeated surgeries need to be considered. Potentially, the patient could have no benefit or reduced function due to failed reconstructive efforts [42].

Suboptimal tensioning of the graft causes problems. If the FDP graft from the fingertip to the palm is kept too long, a lumbrical plus digit may result. Contracture of the FDP motor causes more tension on the lumbricals than the distal graft, causing paradoxical extension of the interphalangeal joints. Conversely, if a graft is tensioned too tightly a quadriga effect may occur, especially in the third to fifth digits. In this case, further (common) FDP muscle belly contraction is limited by the fully flexed reconstructed digit, leaving the muscle incapable to further flex the other fingers with their less tight/longer tendons.

Complications of two-stage grafting include infection, synovitis around the implant or rupture of the distal juncture between stages one and two. Other reported complications include median nerve neuralgia and carpal tunnel syndrome [42].

In all cases, adhesion formation is the most important reason for disappointing results and the need for additional interventions [43, 44]. If, in the months following reconstruction, active flexion diminishes in the presence of passive flexion, tenolysis should be considered. Reoperation however, should be delayed. If tenolysis is performed within 5 months of tendon reconstruction there is an increased risk of tendon rupture [35].