Hand Surgery
1st Edition

Extensor Tendon Reconstruction after Chronic Injuries
Tim R. C. Davis
Most acute extensor tendon injuries are readily diagnosed, and the results of their acute management are usually satisfactory so that there is no significant residual functional deficit requiring secondary reconstruction. However, some, particularly mallet and central slip injuries of the extensor tendon in the finger, present late, and a few are not diagnosed on initial presentation. Furthermore, the outcome of treatment is sometimes unsatisfactory, and in some it is impossible to perform primary repair because of loss of tendon substance or associated skin and soft tissue injuries. It is in these instances that reconstruction of chronic injuries is required.
The finger extensor system has nine zones, and that of the thumb has seven zones (Fig. 1). Zones 1 to 4 involve the finger; zone 5 overlies the metacarpophalangeal joints; and zones 6, 7, and 8 involve the extrinsic extensor tendons on the dorsum of the hand, under the extensor retinaculum, and in the distal forearm, respectively. Zone 9 involves the musculotendinous junctions and muscles themselves. As the thumb has only one interphalangeal joint and two phalanges, its extensor tendon only has two digital zones (T1 and T2). Its zone T3 is equivalent to finger zone 5, its zone T4 to finger zone 6, and its zone T5 to finger zone 7.
The finger extrinsic tendons primarily extend the meta-carpophalangeal joint, whereas the lateral bands of the extensor hood, which arise from the interosseous muscles, flex the metacarpophalangeal joints and extend the interphalangeal joints. Thus, zone 5 to 9 tendon injuries result in loss of active metacarpophalangeal joint extension, but interphalangeal joint extension is preserved. The anatomy of the extensor mechanism of the finger is complex, with differential motion within adjacent portions allowing precise finger motion that can never be restored by our crude attempts at reconstruction. The extensor expansion contains numerous structures, but to understand the surgical techniques described in this chapter and the functions of the extrinsic tendons, the central slip, and the lateral bands, it is necessary to be familiar with only three other structures: the sagittal bands, the transverse retinacular fibers, and the oblique retinacular ligament (Landsmeer’s ligament) (Fig. 2).
The sagittal bands arise from both sides of the palmar plate of the finger metacarpophalangeal joint and the adjacent intermetacarpal ligaments, which attach to the meta-carpal neck. They pass around the sides of the meta-carpophalangeal joints and attach to zone 5 of the extensor tendon. It is through the sagittal bands that the finger extensor tendons extend the metacarpophalangeal joints and also stabilize the extensor tendons on the dorsum of the metacarpophalangeal joints and prevent them from subluxing radially, or more commonly ulnarly, into the intermetacarpal spaces.
The transverse retinacular fibers are thin and inconspicuous fibrous structures in normal circumstances. They arise from the skin, subcutaneous tissues, and extensor expansion on the dorsum of the proximal interphalangeal (PIP) joint and run down both sides of this joint to insert into the skin and subcutaneous tissues on the palmar surface of the finger. Some of the dorsal transverse retinacular fibers run between the central slip and the lateral bands of the extensor expansion, and these hold the lateral bands dorsal to the axis

of rotation of the PIP joint and prevent them from subluxing palmarly. Some of the palmar transverse retinacular fibers attach the lateral bands to the subcutaneous tissues and skin on the palmar surface of the PIP joint. The transverse retinacular fibers become significant in the boutonnière deformity, as isolated division or rupture of the central slip does not cause this deformity: A boutonnière deformity occurs only if, in addition to central slip division, there is tearing or elongation of the dorsal transverse retinacular fibers that allows palmar migration of the lateral bands. If this occurs, the palmar transverse retinacular fibers fibrose and shorten and then prevent relocation of the lateral bands to their normal position, dorsal to the axis of rotation of the PIP joint. The oblique retinacular ligament of Landsmeer rises from the palmar surface of the distal third of the proximal phalanx and the adjacent fibrous flexor tendon sheath. It runs distally and obliquely across the PIP joint (palmar to its axis of rotation) and merges with the lateral aspect of the extensor tendon over the distal half of the middle phalanx (zone 1). It has no muscle attachment and functions through a tenodesis effect. When the PIP joint is flexed, the oblique retinacular ligament becomes slack and allows flexion of the distal interphalangeal joint. In contrast, when the PIP joint is extended, the oblique retinacular ligament becomes tight, causing extension of the distal interphalangeal joint. Oblique retinacular ligaments are found on both the ulnar and radial sides of each finger and are well formed in some individuals but poorly formed in others. Their function in normal hands is controversial, but their presence preserves active distal interphalangeal joint extension after division of the lateral bands in zone 2 for the treatment of a mobile boutonnière deformity.
FIGURE 1. The zones of injury of the extensor mechanism.
There are three wrist extensor tendons: extensor carpi radialis longus and brevis and extensor carpi ulnaris. However, extensor carpi ulnaris is effective only as an extensor tendon in supination, as in pronation it lies on the ulnar aspect of the wrist. In daily life, wrist extension is usually performed with the forearm pronated, and thus, it is an ineffective substitute for extensor carpi radialis longus and brevis. The extrinsic finger extensor tendons also secondarily extend the wrist joint, but this action is weak and requires either full metacarpophalangeal joint extension or stabilization of these finger joints by static tone within the finger flexor tendons.
When deciding the treatment for a chronic extensor tendon injury, it is important to determine the length of time since the injury, the extent of any associated soft tissue injuries, and the functional loss and disabilities attributable to the loss

of tendon function. The location, extent, mobility, and maturity of any skin or soft tissue scarring should also be noted, and one should particularly ascertain whether such scarring overlies the site of a proposed reconstruction or the path of a potential tendon graft or tendon transfer. In addition, the mobility, both active and passive, of the wrist and finger joints should be assessed, and for zone 8 and 9 injuries in which active extension of the wrist is preserved, the effect of wrist extension and flexion on metacarpophalangeal joint position should be assessed. This is because the distal ends of the damaged finger extensor tendons in the forearm may be fixed in scar tissue and thus produce a tenodesis effect in which wrist flexion causes metacarpophalangeal joint extension and wrist extension causes metacarpophalangeal joint flexion (Fig. 3). In some instances, this tenodesis effect may make secondary extrinsic finger extensor tendon reconstruction unnecessary, especially when there are severe associated soft tissue injuries to flexor and extensor surfaces of the forearm and the dorsum of the hand that restrict the range of reconstruction options.
FIGURE 2. The structure of the extensor expansion. The extrinsic extensor tendon of the finger is attached to the sagittal bands on the dorsolateral aspect of each metacarpophalangeal (MCP) joint. These run palmarly to insert into the palmar plate of this joint, allowing flexion of the metacarpophalangeal joint. There may also be an insertion of the extrinsic extensor tendon into the base of the proximal phalanx. The extrinsic extensor tendon continues distally as the central slip and attaches predominantly to the base of the middle phalanx. The lateral bands run anterior to the center of rotation of the metacarpophalangeal joint and then dorsal to the axis of rotation of the proximal interphalangeal (PIP) joint to insert into the base of the distal phalanx. DIP, distal interphalangeal.
FIGURE 3. Tenodesis effect of wrist position of finger metacarpophalangeal (MP) joint position after zone 8 and 9 finger extensor tendon injuries after which the distal tendon ends have become surrounded by scar tissue in the forearm but active wrist extension is still preserved. A: With the wrist in neutral, the finger MP joint can be slightly flexed before its extensor tendon tightens and prevents further flexion. B: Wrist flexion increases the length of the path for the finger extensor tendon; as the tendon has a fixed length, the MP joint has to extend. C: Wrist extension decreases the length of the path for the finger extensor tendon, thus allowing MP joint flexion.
Nonoperative Treatment
Zone 1 and 2 thumb finger extensor tendon injuries result in the typical mallet deformity, with loss of active finger distal interphalangeal or thumb interphalangeal joint extension. A closed mallet finger tendon injury that presents late, although within 6 weeks of injury, may be treated conservatively in a Stack (mallet) splint (as for acute injuries), and a satisfactory outcome may be achieved (1). However, in the author’s experience, many complain of persistent deformity, and some acute mallet injuries, despite appropriate conservative treatment, result in a persistent and significant extension lag. When assessing patients who present late or who have an unsatisfactory result of primary treatment, it is important to confirm that there is a persistent disability and that this is attributable to the loss of active distal interphalangeal joint extension. Patients frequently complain of pain and swelling on the dorsum of the distal interphalangeal joint for many months after a mallet injury, and this, rather than the loss of extension, is usually the reason for the complaint. Such patients should be reassured that the pain and swelling should settle within 6 to 12 months of the injury, and only those with disability due to the extension lag should consider surgical treatment. Passive distal interphalangeal joint extension is usually preserved after mallet injuries, and most patients with chronic mallet deformity complain of little disability due to the deformity once the initial pain and swelling have subsided. Thus, most patients with a persistent mallet deformity do not require surgical treatment, but if there is a significant disability or cosmetic deformity, there are three surgical treatment options.
Surgical Management of Zone 1 and 2 Injuries
Long-standing zone 1 and 2 injuries can be treated either by shortening or reefing of the extensor tendon in zone 2 or by adjusting the balance of the extensor mechanism by dividing the central slip (Fowler’s procedure). All these procedures are best performed under a local anesthetic ring block using a finger tourniquet so that the patient can

actively extend the finger during the procedure and allow the surgeon to assess the result of this intervention.
Zone 2 Extensor Tendon Shortening/Reefing
Chronic zone 1 and 2 extensor tendon injuries are exposed through a dorsal incision over the middle phalanx, which is usually S-shaped. It is sometimes possible to see the area of scarring within the extensor tendon, but in many instances, it is difficult to detect the site of injury. The patient is asked to extend his or her finger, and the surgeon passively corrects the extension lag while observing the resultant buckling/laxity of the extensor tendon in zone 2. This allows the surgeon to assess how much shortening of the extensor tendon is required. The tendon is divided either transversely or obliquely in zone 2, usually at the site of injury if this is discernible, and the distal interphalangeal joint is fixed in full extension with a transarticular Kirschner wire. The two ends of the tendon are overlapped by 2 to 3 mm and repaired with nonabsorbable 6-0 interrupted sutures. The skin wound is then sutured, and the finger is rested on a splint with both interphalangeal joints extended. This splint is retained for 6 weeks, at which time Kirschner wire is removed, and the patient is encouraged to mobilize the finger. The results of these late repairs/shortening of zone 1 mallet injuries are not always satisfactory either because an extensor lag persists due to inadequate tendon shortening or because scarring tethers the repaired tendon to the underlying middle phalanx, which may also prevent full distal interphalangeal flexion. A secondary extensor tenolysis is not infrequently required, although this should not be performed for at least 3 months so as to allow maturation of the initial repair and surrounding scar tissue.
An alternative technique of shortening the extensor expansion in zones 1 and 2 is tenodermodesis (2,3). This is also performed under local anesthetic with a finger tourniquet and consists of en bloc excision of a wedge of skin and tendon from the dorsal aspect of the distal interphalangeal joint. After this wedge of skin and tendon has been excised, the wound edges should just come together when the distal interphalangeal joint is fully extended, and a further segment of skin and tendon should be excised if they come together before full extension occurs. Usually, the wedge of skin and tendon that is excised is 2 to 3 mm wide. The edges of the skin and tendon are then sutured together en bloc with 4-0 monofilament nylon stitches that pass through both the skin and the extensor tendon. The distal interphalangeal joint is then splinted in extension, and the sutures are retained for 6 weeks. There are no large studies of this technique, but Warren et al. (4) reported satisfactory results in four of six patients.
Another technique, which avoids the risks of division and subsequent repair of the relatively avascular extensor expansion in zone 2, is to shorten the tendon in this region by folding it over (Fig. 4) (5).
FIGURE 4. Folding over the extensor tendon in zone 2 for correction of a mallet deformity. The same technique may be used to shorten the central slip in boutonnière deformities.
Fowler’s Procedure
The central slip over the PIP joint is divided, allowing proximal migration of the whole of the extensor mechanism of the finger. This therefore tightens the extensor tendon in zones 1 and 2 after a mallet injury. Provided the dorsal transverse retinacular fibers, which join the lateral bands to the central slip, are not damaged, a boutonnière deformity should not occur.
Fowler’s procedure should be performed under local anesthetic with either an upper arm tourniquet or a tourniquet at the base of the involved finger. The procedure may be performed through a transverse incision directly over the PIP joint or a midlateral incision, but the author prefers a dorsal S-shaped incision that extends from the PIP joint distally over the middle phalanx. This is because the author has encountered adhesions between the extensor tendon and the middle phalanx at the site of injury and prefers to release them to ensure that the Fowler’s procedure functions satisfactorily. The central slip is divided transversely at its insertion into the middle phalanx, with care taken not to damage the lateral bands or the transverse retinacular fibers. One must ensure that the central slip is completely released, and it should be seen to separate from its insertion during finger flexion. If, after the central slip release, the distal interphalangeal joint does not actively extend fully, the author then passes a MacDonald dissector under the palmar edge of each lateral band and moves it up between the middle phalanx and the extensor tendon, thus releasing any adhesions. This usually suffices, although firm adhesions at the site of injury may require release with a scalpel. Once active extension of the distal interphalangeal joint has been regained, the patient is asked to make a tight fist to confirm that the lateral bands do not sublux palmarly; the wound is closed and the finger is dressed. Some surgeons (6) recommend immobilization with the PIP joint in 45 degrees’ flexion and the distal interphalangeal joint extended for 4 weeks; others encourage active finger mobilization from the first or second postoperative day but discourage the patient from making a tight fist for 2 weeks. Still other surgeons, concerned that a boutonnière deformity may develop with unrestricted early mobilization, prefer to splint the PIP joint in extension for 1 to 2 weeks but encourage the patient to actively extend and flex the distal interphalangeal joint during this period.
Bowers and Hurst (6) performed Fowler’s procedure in five patients over a 3-year period. Preoperatively, all had extensor

lags of more than 45 degrees, and these corrected fully in four cases and improved to a 10-degree lag in the other case. The associated hyperextension of the PIP joint corrected in all cases, but an extension lag of this joint developed in one instance. Grundberg and Reagan (7) treated 17 patients with mallet deformities and reported that the average extensor lag reduced from 37 degrees preoperatively to 9 degrees after a minimum follow-up of 4 months. Hyperextension of the PIP joint corrected in all 17 cases, although four patients developed extension lags of 10 degrees or less at this joint, which were never troublesome. Finally, Houpt et al. (8) reported the results of 35 Fowler’s procedures in fingers that preoperatively had a mean extensor lag of 45 degrees. After a mean follow-up of 8 months, 26 patients had regained full active distal interphalangeal joint extension.
The author’s preferred treatment for a symptomatic chronic mallet deformity is Fowler’s procedure. This is because the author considers that the healing of extensor tendon repairs is precarious and likely to cause adhesions that restrict tendon gliding. The author’s experience is that Fowler’s procedure usually improves the extension lag of the distal interphalangeal joint and sometimes corrects it fully, although it often results in a slight (15-degree) extensor lag of the PIP joint. This, however, is well tolerated by patients who find it less obtrusive than the mallet deformity. A mallet deformity in which the underlying distal interphalangeal joint is osteoarthritic and has a limited range of passive extension should be accepted, or the patient should be offered fusion of the distal interphalangeal joint. Fusion is primarily indicated for persistent pain rather than the loss of extension.
Open and closed central slip injuries may cause mild/moderate mobile boutonnière deformities even if an acute injury is treated carefully and appropriately with splints. Furthermore, central slip injuries may be accompanied by capsular injuries of the PIP joint that can cause persistent swelling and a fixed flexion deformity. A fixed boutonnière deformity, with fixed flexion of the PIP joint and fixed hyperextension of the distal interphalangeal joint, develops only if the dorsal transverse retinacular fibers, which hold the lateral bands of the extensor mechanism dorsolateral to the center of rotation of the PIP joint, are also damaged at the time of injury or subsequently tear or stretch. This allows the lateral bands to migrate palmar to the center of rotation of the PIP joint so that they then flex this joint while still extending the distal interphalangeal joint. Not only is this deformity unsightly but, as opposed to a mobile deformity, it also causes a significant functional disability, as it renders the finger virtually useless.
Clinical evaluation of a patient with a boutonnière deformity requires assessment of the functional disability and measurement of the extensor lag, fixed flexion deformity, and range of flexion of the PIP joint, as well as the ranges of active and passive movement of the distal interphalangeal joint. The PIP joint should also be assessed for residual swelling. Mild, mobile boutonnière deformities do not usually interfere with function and hardly ever require treatment, but significant ones, whether mobile or fixed, may be treated surgically provided the patient considers that this disability is sufficient to warrant the inconvenience of a surgical procedure and an extensive, time-consuming rehabilitation schedule that cannot be guaranteed to improve function and could make the finger worse.
It is absolutely imperative that any fixed deformity is corrected by serial splintage before embarking on tendon rebalancing surgery, as otherwise it is very likely to fail. If the fixed deformity persists despite serial splintage, the finger should be left untreated or, if the deformity is severe and is causing significant disability, either amputated or fused in a more functional position at the PIP joint. Fusion is advisable only if a reasonable range of distal interphalangeal joint flexion can be restored, as otherwise the finger has little function and gets in the way.
Mild Mobile Boutonnière Deformities
Mild mobile boutonnière deformities, in which the lateral bands are mobile and not permanently subluxed palmarly, can be treated surgically. This entails either shortening of the central slip with dorsal realignment of the lateral bands or division of the extensor mechanism distally in zone 2 over the proximal half of the middle phalanx. However, the disability in these cases is often not sufficient to warrant intervention (9). Division of the extensor tendon in zone 2 was used by Littler and allows proximal migration of the whole of the extensor mechanism, such that the central slip tightens and regains its ability to extend the PIP joint (18). Extension of the distal interphalangeal joint is maintained after this procedure (10) by the oblique retinacular fibers (Landsmeer’s ligaments), which insert into the extensor tendon distal to the zone 2 tenotomy and extend the distal interphalangeal joint when the PIP joint is actively extended.
If it is elected to shorten the central slip, the PIP joint is immobilized in full extension with a transarticular Kirschner wire. The central slip is then divided at the site of previous injury, where it is usually thinner and contains less tendon tissue. It is then repaired with overlap of up to 3 mm of the two ends such that it is tight. Most, although not all, surgeons also move the lateral bands dorsally with one of a variety of techniques. These include suturing the

lateral bands together on the dorsum of the PIP joint after division of the palmar transverse retinacular fibers (11), suturing them to the underlying soft tissues over the dorsum of the base of the middle phalanx (12), and suturing them to the central slip (13). Other surgeons (14,15) do not routinely relocate the lateral bands, although all agree that the central slip usually requires no more than 3 mm of shortening. At the end of the procedure, the finger is dressed and rested on a splint that allows distal interphalangeal joint flexion and extension. The Kirschner wire is removed after 4 to 6 weeks, when active finger exercises are commenced to regain PIP joint flexion. A static or dynamic Capener splint is usually worn between therapy sessions for 2 to 4 weeks. An alternative to division and overlap of the central slip is to fold over the elongated central slip just proximal to the area of scarring using nonabsorbable sutures (Fig. 4) (12). If this technique is used, then again the PIP joint should be held in extension with a transarticular Kirschner wire for 4 weeks.
Severe Fixed Boutonnière Deformities
Shortening of the central slip or elongation of the distal extensor expansion in zone 2 is inadequate for the treatment of severe fixed boutonnière deformities, in which the lateral bands have subluxed and remain permanently palmar to the center of rotation of the PIP joint. In these cases, the first step is to restore passive extension of the PIP joint by serial splintage. This is time-consuming and may take the form of dynamic splintage (Capener splints) or static splintage using serial plaster of Paris casts or thermoplastic splints. If the fixed flexion deformity does not improve and resolve, a surgical release of the contracted palmar capsule of the PIP joint may be considered, but this should be done as a separate procedure before the reconstruction of the extensor mechanism (16).
If passive correction of the boutonnière deformity is achieved, a robust reconstruction of the extensor mechanism is required to prevent recurrent palmar migration of the lateral bands. Matev (17), from Bulgaria, described a procedure (Fig. 5) in which the radial lateral band is divided at the base of the middle phalanx and is inserted into the distal stump of the central slip so that it then exclusively extends the PIP joint. The ulnar lateral band is then divided more distally, and its proximal end is sutured to the distal end of the radial lateral band. This elongates the extensor expansion in zone 2, thus permitting distal interphalangeal joint flexion and correcting the hyperextension deformity of this joint. An alternative procedure (Fig. 6) (10) described by Littler and Eaton (18) entails division of both lateral bands over the base of the middle phalanx, proximal to the insertions of the oblique retinacular ligaments, as described for mild boutonnière deformities. However, the lateral bands are then both rotated dorsally so that their palmar edges come together on the dorsum of PIP joint, where they are then sutured together and to the underlying attenuated central band. The PIP joint is held in full extension with a transarticular Kirschner wire for 3 weeks. It is then splinted in full extension while the distal interphalangeal and metacarpophalangeal joints are left free and mobilized. After a further week, the PIP joint is gently mobilized, although it is splinted in extension between physiotherapy sessions for 2 to 4 months.
FIGURE 5. Matev Procedure. Left: The radial lateral band is divided over the proximal portion of the middle phalanx (A) and the ulnar one is divided more distally (B). Right: The proximal end of the radial lateral band is then sutured into the central slip and now extends the proximal interphalangeal joint (A’). The distal end of the radial lateral band is sutured to the proximal end of the ulnar one over the middle phalanx (B’). As the lateral bands were divided at different levels, this causes elongation of the extensor tendon over the middle phalanx, which allows correction of the hyperextension and flexion of the distal interphalangeal joint.
A number of papers report reasonably satisfactory results for the late reconstruction of the boutonnière deformity, but when considering these, one must remember that the outcome depends to a very large extent on the condition of the finger preoperatively. If the boutonnière deformity is mild, there is a reasonably good chance of success for surgery, although some may question whether the preoperative disability was sufficient to warrant intervention and the

inevitable possibility of failure. However, if there is a severe fixed boutonnière deformity, the outcome of surgery to reconstruct the extensor mechanism is, in the author’s experience, very poor. Some papers particularly report an improvement in proximal interphalangeal joint extension, but it is also important to assess that this was not at the expense of loss of flexion. Furthermore, it is important to know whether the procedure corrected the hyperextension and restored flexion of the distal interphalangeal joint. There are no large studies of boutonnière deformity reconstructions, and extensor tenotomy over the middle phalanx for mild deformities has been described in only two cases (19). However, this technique has been recommended by other surgeons, including Littler (18). Rothwell (12) assessed the outcome of reefing the central slip combined with relocation of the lateral bands in 12 posttraumatic cases and reported that 10 regained full active flexion and extension of both interphalangeal joints. Grundberg (14) excised a 3-mm length from the central slip that was then repaired end to end and left the lateral bands undisturbed. He assessed seven posttraumatic (presumably mobile) cases with PIP lags of 30 degrees to 70 degrees preoperatively and found that all but two corrected fully. The others improved to less than 20 degrees. Although some of these patients lost up to 20 degrees of PIP joint flexion, hyperextension was corrected, and flexion was improved at the distal interphalangeal joint, although extensor lags at this joint of up to 20 degrees were encountered. Caroli et al. (15) excised the scarred portion of the central slip as a “swallowtail” flap and released the palmar transverse retinacular fibers from the lateral bands, thus allowing them to relocate dorsally. They treated 20 posttraumatic boutonnière deformities in supple fingers with full ranges of passive motion and assessed 18 at a mean follow-up of 2 years. Thirteen had excellent results, with a residual extension lag at the PIP joint of 10 degrees or less, although one of these had less than 100 degrees of PIP flexion. Three patients had fair results, with minimal improvement, and these were attributed to their failure to use splints or cooperate with physiotherapy postoperatively. In the one case resulting in a poor result, the deformity recurred completely. Littler’s technique for more severe deformities, in which the lateral bands are divided, rotated, and sutured together on the dorsum of the PIP joint, improved the deformity in all eight of Littler and Eaton’s patients (18). More recently, Terrill and Groves (16) reported on the outcome of the Matev procedure in 20 fingers, of which 14 had normal passive ranges of PIP joint movement preoperatively; this had been accomplished in two instances by release of the palmar plate some months earlier. Twelve of the 14 mobile deformities achieved a satisfactory outcome, with the mean extension lag of the PIP joint reducing from 60 degrees to 14 degrees and a mean arc of flexion of 96 degrees. However, many lost 10 degrees to 15 degrees of flexion of this joint, although the hyperextension of the distal interphalangeal joint was corrected in all cases. Distal interphalangeal joint extensor lags of up to 30 degrees were encountered, but the range of flexion of this joint improved considerably. The results for the six fingers

with preoperative fixed flexion deformities of the PIP joint were less satisfactory.
FIGURE 6. A–D: Littler’s procedures for correction of boutonnière deformity. A,B: Dorsal views of finger showing central slip (CS), lateral bands (LB), and oblique retinacular fibers (ORF). A: The LBs are divided proximal to the insertions of the ORFs into the extensor tendon (dashed lines). For mild boutonnière deformities, this is all that is required, and the extensor hood can now migrate proximally, increasing the tension in the CS. However, for severe deformities, the LBs are then rotated dorsally (B). Their palmar edges are sutured together and to the attenuated CS over the proximal interphalangeal joint. C,D: Lateral views of severe boutonnière deformity. C: The site of division of the LBs is shown via the dashed lines. D: Suture of the LBs to the CS over the proximal interphalangeal joint. When the proximal interphalangeal joint is actively extended (arrow), this now tightens the ORFs causing extension of the distal interphalangeal joint, even though the LBs have been divided.
Recurrence of boutonnière deformity, whether partial or complete, may occur if the PIP joint is mobilized too early, if the central slip is not shortened sufficiently, or if the repair of the shortened central slip is of inadequate strength. Alternatively, the central slip may be overshortened or may become adherent to the underlying proximal phalanx, causing loss of PIP flexion. One should remember that, especially in times of recession, a major complication of all procedures requiring lengthy finger immobilization and rehabilitation is loss of employment. Patients should be fully aware of the length of the recovery period and rehabilitation program before embarking on surgery that may prevent manual workers from returning to work for several months.
There is usually a significant dorsal skin injury associated with segmental extensor mechanism injuries, and this may be the result of a burn or a machine injury. Thus, reconstructive surgery is usually delayed until adequate skin cover has been restored. If the skin overlying the tendon defect is adherent to the underlying bone so that there is a fixed scar, reconstructive surgery is most unlikely to benefit the patient. However, if good soft tissue cover with mobile skin rather than a skin graft is achieved, the extensor expansion defect can be repaired with a tendon graft, provided the loss of function attributable to the extensor tendon defect is significant. Many people with loss of the extensor tendon in zone 2 describe minimal disability and, as reconstructive surgery in this zone is unpredictable, are best left untreated.
Zone 3 to 4 loss of tendon substance causes more disability, and here the extensor expansion is more substantial and amenable to reconstruction with tendon grafts. One technique of reconstruction (Fig. 7) uses a strip of extensor digiti minimi or palmaris longus tendon. This is passed through a tunnel created from two drill holes on the dorsal surface of the base of the middle phalanx and then crossed over and sutured to the extensor hood proximally (20). Rico et al. (21) used a similar technique, although they sutured the tendon graft to the distal stump of the central slip rather than create a tunnel in the base of the middle phalanx. In addition, a palmar release of the PIP joint was performed at the same operation in those who did not have full passive PIP joint extension. They reported the results in 22 postburn fingers in 12 patients and observed better results in the fingers with the greatest range of preoperative PIP joint passive movement. Another option is to perform a bypass extensor tendon transfer, in which extensor indicis proprius is lengthened with palmaris longus and is attached to the base of the middle phalanx (22). Satisfactory results have been reported with this technique in five cases.
FIGURE 7. Reconstruction of segmental loss of central slip using tendon graft (palmaris longus or extensor digiti minimi). Two drill holes are placed in the dorsum of the middle phalanx to create a tunnel through which the tendon graft is passed. The ends are then crossed over and sutured proximally to the extensor hood.
The management of extrinsic tendon reconstruction depends on the number of damaged tendons that require reconstruction, the condition of the overlying skin and surrounding soft tissues, and the state of the flexor compartment muscles, which might be used for tendon transfers. Late extensor tendon reconstructions in patients who have sustained serious associated soft tissue injuries may require subsequent tenolyses before a satisfactory result is achieved. In others, the associated soft tissue injuries may have caused joint stiffness and dense scarring, which despite meticulous tendon reconstruction surgery, preclude a satisfactory outcome.

Zone 6 Injuries
Isolated zone 6 tendon injuries after acute trauma are readily identified, and the outcome of acute repair is usually excellent (23). However, if an isolated extensor tendon injury proximal to the juncturae tendinum presents after 3 to 4 weeks, it is usually impossible to perform a primary repair, as the proximal tendon end will have retracted. In such cases, buddying of the distal end of the injured extensor tendon to an adjacent finger extensor tendon or performing an extensor indicis proprius tendon transfer is the treatment of choice, and tendon grafts are not usually required or performed. Buddying the damaged tendon to an adjacent tendon using a Pulvertaft weave is the simplest procedure, although it cannot be done for very distal lesions close to the metacarpophalangeal joint. However, at this level, the juncturae tendinum may have prevented proximal migration of the proximal tendon end, and a direct repair may be possible. After buddying of tendons in the proximal portion of zone 6 lesions, one should carefully check that the tendons do not abut on the extensor retinaculum during active extension and thus prevent full active extension of the fingers. The extensor indicis proprius transfer follows the same principle described for zone 7 extensor pollicis longus

tendon ruptures the author finds it particularly useful to draw a transverse line across all the intact finger extensor tendons with a marker pen before harvesting the extensor indicis, as this allows easier assessment of the tension after the transfer.
Multiple finger extensor tendon injuries in zone 6 with loss of the overlying soft tissues are a more complex problem. The long-established technique of reconstruction requires multiple procedures. First, adequate soft tissue cover is obtained using a free flap, a pedicled flap, or a local flap. Afterward, passive movements of the fingers are maintained, and tendon grafting is then performed at a secondary procedure. Palmaris longus, plantaris, or toe extensors are usually used as grafts, and these are placed superficial to the extensor retinaculum to reduce adhesions and the possibility of obstructed tendon movement. Tendon grafts can also be passed under split-thickness skin grafts, and good results have been reported (24,25). It is also possible in some of these complicated cases to perform a one-stage reconstruction using either standard devascularized tendon grafts under a skin flap or using a composite flap, which, as well as containing skin, contains vascularized tendons (26,27). Such flaps can be raised on the dorsalis pedis artery or the radial artery, in which case, the palmaris longus and part of the brachioradialis tendon are used (28). If there is concern regarding the condition of the extensor digitorum communis muscle, one can use either a flexor carpi radialis or flexor carpi ulnaris tendon transfer, which is then elongated by a tendon graft.
There are very few outcome studies of either simple or complex tendon reconstructions in this region, and most amount to case reports. However, Cautilli and Schneider (29) reported the results of seven complex extensor tendon injuries with overlying skin loss. These cases were initially treated with pedicled skin flaps to achieve skin cover, and in several cases, silicone tendon implants were inserted at the same surgery to prepare tunnels for the subsequent tendon grafts. Tendon grafting was performed 3 to 5 months later, and satisfactory restoration of active finger metacarpophalangeal joint extension was achieved in all cases, although two required extensor tenolyses to regain finger flexion and one case was classed as a failure. Although the outcome of finger extensor tendon reconstruction in zones 6 to 8 is obviously dependent on the force and excursion of the extensor digitorum communis muscle (which may be damaged or be scarred) or the new motor provided by a tendon transfer, as well as the setting of the correct tension, the functional outcome and range of finger extension and flexion are to a large extent determined by the range of active wrist movement. This is because of the tenodesis effect of wrist flexion and extension, and even if there is no active muscle pull on the reconstructed finger extensor tendons, full metacarpophalangeal flexion and extension can be obtained (Fig. 3).
Finally, despite complete loss of the extensor tendons in this zone, some patients who also sustain severe associated soft tissue injuries to the dorsum of the hand regain sufficient “active” metacarpophalangeal joint extension to obviate the need for surgery. Their “active” extension is due to the elastic recoil of the scarred soft tissues on the dorsum of the hand (30). In other patients with severe associated soft tissue injuries, the surgeon may consider that extensor tendon reconstruction is most unlikely to be successful and significantly improve hand function. In these cases, it is better to rapidly adapt the patient’s home and work environments rather than perform speculative surgery with little hope of success and a prolonged rehabilitation program.
The most common injury in zone 7 is closed rupture of the extensor pollicis longus tendon, which usually follows an undisplaced fracture of the distal radius. However, rupture of the little- and ring-finger extensor tendons can occur on a prominent, osteoarthritic ulnar head (31), and these are treated in the same manner as ruptures in rheumatoid arthritis (see Chapter 68).
Closed rupture of the extensor pollicis longus tendon is a well-recognized complication of undisplaced fractures of the distal radius and usually occurs several weeks after the injury. Treatment of the tendon injury is delayed until the fracture has united, and the wrist has regained full mobility. Although some patients experience little disability and decline reconstructive surgery, most complain of a lack of dexterity, due not only to the inability to extend the thumb interphalangeal joint but also to the inability to retropose the thumb and place it in the plane of the fingers. The extensor pollicis longus tendon is the only muscle with these actions. The extensor pollicis longus tendon cannot be repaired, and the standard (almost universal) treatment is an extensor indicis proprius transfer (32), although other transfers, including abductor pollicis longus (33), have been described.
Surgical Technique
Under tourniquet control, the extensor indicis proprius tendon is identified through a transverse incision just proximal to the index finger metacarpophalangeal joint. This tendon lies deep and ulnar to the extensor digitorum communis tendon and is divided just proximal to the extensor hood, which should not be damaged. A second transverse incision is then made along the line of the tendon at the mid–index metacarpal level, where the extensor indicis proprius tendon is again identified and freed from the surrounding soft tissues. The extensor indicis proprius and the “index” extensor digitorum communis tendons often have fairly firm soft tissue attachments in this area that require considerable force to pull apart if they are not freed through this extra incision. Next, a longitudinal incision with its distal margin at the level of the radiocarpal joint is made over the finger extensor tendons in the distal forearm. A window is made in the extensor retinaculum over the fourth compartment, and the extensor indicis proprius tendon, which lies deep to the extensor digitorum communis tendons, is identified by pulling on its distal end. This tendon is then brought out through the retinacular window, which will act as its pulley (in place of the Lister’s tubercle). An S-shaped incision is made over the path of the extensor pollicis longus tendon in the first web space. The distal end of this tendon is usually bulbous and lying within a pseudocapsule that is adherent to the surrounding soft tissues. Care must be taken not to damage or stretch the overlying superficial branch of the radial nerve while it is mobilized. A wide subcutaneous tunnel is then created between this web space incision and the one on the dorsum of the wrist. The author does this with long-handled curved scissors (McIndoe’s scissors), which the author pushes into the subcutaneous tissues and then opens and withdraws. The extensor indicis proprius tendon is now passed into the web space wound, and all incisions except that in the web space are closed. With the wrist and thumb extended, the extensor indicis tendon is then sutured to the distal end of the extensor pollicis longus tendon with a Pulvertaft weave using 4-0 nonabsorbable sutures. The tension of the transfer is correct if, with the base of the thumb abducted and the thumb metacarpophalangeal joint extended, the interphalangeal joint extends fully with the wrist in 20 degrees of flexion and the thumb can be opposed to the middle fingertip with the wrist extended. In the author’s experience, it is best to set the transfer in too much, rather than too little, tension, as extensor transfers that initially appear too tight gradually stretch out with time. The transfer is protected in a plaster cast that holds the wrist in slight extension and the thumb extended and retroposed for 3 weeks. The author leaves the thumb interphalangeal joint as well as the fingers free during this period and allows the patient to gently use his or her transfer to actively extend the thumb interphalangeal joint once or twice every day. This tendon transfer is very reliable and requires no formal rehabilitation, presumably because the extensor indicis proprius and extensor pollicis longus tendons are synergistic.
Although it is widely believed that this transfer results in loss of independent index finger metacarpophalangeal joint extension, most patients regain the ability to actively extend the index finger metacarpophalangeal joint independently of those of the other fingers (34,35 and 36). Presumably, this is because the index finger extensor digitorum communis tendon has a more or less separate muscle belly. Lemmen et al. (36) reported that 15 of 17, and Magnussen et al. (37) that 19 out of 21, extensor indicis proprius transfers achieved satisfactory long-term results. Lemmen et al. found 10 degrees and 20 degrees of mean active losses of interphalangeal and metacarpophalangeal joint extension.
Isolated divisions of the radial wrist extensor tendons may be missed because the emergency doctor does not appreciate that the wrist can still be actively extended against gravity even after these tendons have been divided. This is either because of the action of the extensor carpi ulnaris (a reasonable wrist extensor with the wrist in supination) or because the finger extensor tendons can also extend the wrist when the metacarpophalangeal joints are fixed by tension in the finger flexor tendons. Primary repair of the radial extensor tendons is usually impossible after 2 to 3 weeks. If the injury is detected at this time and the overlying skin is satisfactory, a primary tendon graft (e.g., using palmaris longus) can be performed. This should be tight with the wrist in extension to allow for elongation of the extensor carpi radialis muscles from a contracted position. Tendon grafting for reconstruction of the wrist (and finger) extensor tendon injuries can also be performed after a longer delay, but if the tendon injury is relatively proximal and close to the musculotendinous junction, the tendon transfers commonly used after radial nerve injury may be used instead. Transfer of pronator teres to the extensor carpi radialis brevis is very reliable; however, loss of its usual function does cause morbidity, and the author’s preference is for a tendon graft, provided the wrist extensor muscles have not been damaged and it is not more than a few months since the injury. After a wrist extensor tendon graft, the wrist is immobilized in a below-elbow plaster cast in 30 degrees of extension for 6 weeks. The wrist is then

gently mobilized with the patient wearing a protective splint between rehabilitation sessions for a further 4 weeks. If a pronator teres tendon transfer is performed, this is protected in an above-elbow plaster cast with the wrist in extension for 5 to 6 weeks. Rehabilitation is then commenced, but the transfer is protected in a splint between rehabilitation sessions for a further 4 weeks. Finger extensor tendon injuries in zone 8 may also be treated with either a tendon graft or a tendon transfer if the level of the injury is relatively proximal. However, one should remember that, for patients with full active wrist extension and flexion, extensor tendon divisions at this level often do not cause a major disability. This is because the tendon ends are stuck down to the surrounding soft tissues in the distal forearm, and thus, wrist extension and flexion, through the tenodesis effect, allow active finger flexion and extension, respectively (Fig. 3). If, however, primary tendon grafting is performed, the palmaris longus or plantaris tendons are usually used, and care should be taken not to set the tension too tight. The metacarpophalangeal joints should be able to flex fully with the wrist fully extended. This assumes that the extensor communis muscle does not stretch and elongate from its contracted condition when tension is reapplied to it. In truth, the author thinks there is a lot of luck involved in achieving the right tension. An alternative is to use the flexor carpi radialis or extensor flexor carpi ulnaris as a tendon transfer, as described for radial nerve palsy (see Chapter 52). However, unless a bridging tendon graft is used, this can be done only for relatively proximal divisions.

The literature is devoid of outcome studies of these relatively rare injuries. However, the results for radial palsy tendon transfers are reported in Chapter 52, and there are a few case reports of complex injuries with skin loss (38).
Zone 9 extensor compartment injuries involve the muscle bellies themselves, and the posterior interosseous nerve or its branches may have also been damaged. It is thus sometimes difficult to decide whether the loss of extension is due to nerve or muscle damage. Electromyography is useful in differentiating between these possibilities, but a careful clinical examination that assesses whether all the muscles supplied by the posterior interosseous nerve, or only a selection of them, are not functioning is vital. When these findings are combined with the knowledge of the branching patterns of the posterior interosseous nerve (39,40) and the origins of the extensor muscles and the site of injury, the situation may become clear. Poor extensor tendon function after injuries in this zone are best treated by tendon transfers, as described for radial nerve injuries. If the flexor compartment muscles available for transfer have also been damaged or are unavailable for transfer, the only option is a free muscle transfer. As always, the first priority is the restoration of active wrist extension. If there is overlying skin and soft tissue damage, this must be addressed before or at the same time as the tendon reconstruction using the principles discussed for zone 6.
Most cases of ulnar subluxation of the finger extensor tendon at the metacarpophalangeal joint present acutely after trauma, and the results of primary treatment are usually satisfactory. However, some cases present late with clicking (which should not be mistaken for triggering) of the finger during flexion and extension; this is due to the extensor tendon subluxing during flexion and relocating during extension. In others, the extensor tendon is permanently subluxed ulnarly; this causes inability to extend the meta-carpophalangeal joint and is sometimes accompanied by hyperextension of the PIP joint. In contrast to the acute situation, conservative treatment with splintage does not correct the alignment of the extensor tendon, and it is usually impossible to repair the damaged radial sagittal band, as this is scarred and shortened. Eisenbaum (41) described the trapdoor pulley repair technique (Fig. 8), which is performed through an incision on the dorsum of the metacarpophalangeal joint. The extensor tendon, if not chronically subluxed ulnarly, is retracted ulnarly, and a 1-cm length of half the thickness of the dorsal metacarpophalangeal joint capsule is elevated as an ulnar-based flap. The extensor tendon is then replaced centrally on the metacarpophalangeal joint, and the ulnar-based flap (trapdoor) is passed over it and sutured back to the dorsoradial joint capsule. The finger is then splinted in extension for 4 weeks.
An alternative technique is a lumbrical loop operation (Fig. 9) (42). The subluxed tendon and metacarpophalangeal joint are again exposed through a dorsal incision. The radial one-third of the subluxed extensor tendon is stripped from the remainder, starting from a point just proximal to the PIP joint and extending to the level of the articular surface of the metacarpal head. Proximally (at the metacarpal head level), a suture is placed across the whole width of the extensor tendon to prevent further tearing. The mobilized radial strip of the extensor tendon is then passed around the lumbrical tendon and sutured back onto itself with sufficient tension to hold the extensor tendon centrally over the metacarpophalangeal joint and prevent ulnar subluxation. This tension is determined by flexing the metacarpophalangeal joint fully to sublux the extensor tendon and then applying traction to the mobilized strip until the tendon reduces. The extensor hood is then repaired over the proximal phalanx, and the finger is immobilized while healing occurs. Others have passed similar slips of the extensor tendon under the deep intermetacarpal ligament.
FIGURE 8. Trapdoor repair technique for chronic subluxation of a finger extensor tendon. The base of the capsular flap should be no more ulnar than is necessary to replace the extensor tendon centrally over the metacarpophalangeal joint. A: The extensor tendon is shown superficial to the metacarpophalangeal joint capsule, subluxated laterally over the phalanx. B: A partial thickness flap is elevated, with its base on the side of the capsule where the tendon subluxates. C: The extensor tendon is placed deep to the flap, which is subsequently sutured to the intact capsule, stabilizing the course of the extensor tendon.
FIGURE 9. Lumbrical loop technique for relocation of a chronically ulnar-subluxed extensor tendon. A: The extrinsic extensor tendon is split longitudinally with a proximal base to the slip. B: The tendon slip is passed deep to the lumbrical tendon (arrow). C: The tendon slip is sutured back to the intact extensor tendon, and the longitudinal tear in the sagittal band is replaced.
There are only case reports of the above techniques, and satisfactory results were obtained in all three cases. The author’s experience is that chronic subluxation of the extensor tendons does not always require surgical treatment, as many people adapt to the snapping of the dislocating/relocating tendon. Furthermore, the author’s colleagues and the author have found that surgical reconstruction of the sagittal bands can result in finger stiffness.
The roof of the extensor compartment for the extensor carpi ulnaris tendon at the wrist (sixth compartment) may tear as a result of acute trauma, often with the forearm in full supination. The extensor carpi ulnaris tendon may then sublux from its groove in the ulnar head during forearm rotation. This often causes painful snapping of the wrist during forearm rotation, and this usually warrants surgery. Spinner and Caplin (43) described a technique of stabilization of this subluxing tendon in which an ulnar-based flap of extensor retinaculum is used. This rectangular flap is 1 cm wide, and its apex is in line with Lister’s tubercle, on the radial edge of the fourth extensor compartment. Its base is the fibrous septum

between the fifth (extensor digiti minimi) and sixth (extensor carpi ulnaris) compartments. The flap is passed under the extensor carpi ulnaris tendon and is then passed back over this tendon and sutured onto itself so that it holds the extensor carpi ulnaris tendon reduced in the groove in the distal ulna and has its “synovial” layer in contact with this tendon. The retinacular sling is then also sutured to the soft tissues on the radial and ulnar aspect of the groove for the extensor carpi ulnaris in the distal ulna. Postoperatively, the wrist is immobilized in a below-elbow plaster cast for 3 weeks, and a wrist splint is then worn for a further 2 weeks. A more robust technique that the author has used in cases of recurrent subluxation after retinacular flap reconstruction is to create a new roof for the groove for the extensor carpi ulnaris tendon in the distal ulna using a palmaris longus tendon graft. This roof is created by making four or five drill holes on both sides of the extensor carpi ulnaris groove and weaving a thin strip of the palmaris longus tendon through these to create a “mesh roof.” This has prevented recurrent subluxation, but the author has encountered painful stenosis of the extensor carpi ulnaris tendon as a late complication of this procedure.
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