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Tendon Avulsion Injuries of the Distal Phalanx

Tuttle, Harrison, G*; Olvey, Scott, P*; Stern, Peter, J

Section Editor(s): Meals, Roy A MD, Guest Editor; Harness, Neil G MD, Guest Editor

Clinical Orthopaedics and Related Research: April 2006 - Volume 445 - Issue - p 157-168
doi: 10.1097/01.blo.0000205903.51727.62
SECTION I: SYMPOSIUM: Problem Fractures of the Hand and Wrist
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SDC

Mallet injuries are the result of incompetence of the terminal tendon. Most acute mallet fingers can be treated by continuous splinting of the distal interphalangeal (DIP) joint in extension for 5-6 weeks. Fracture dislocations require open reduction and internal fixation. Treatment of chronic mallet injuries must be individualized. If there is a flexible swan neck deformity, spiral oblique ligament reconstruction is indicated. For a fixed contracture, DIP joint arthrodesis is preferred. Profundus avulsion injuries, or jersey finger, seen within 10 days of injury require operative reattachment of the profundus tendon. Treatment of avulsions more than 10-14 days after injury must be individualized and depends on location of the stump (palm vs. digit), time from injury, passive mobility of the digit, and individual functional demands. Chronic avulsions, where the stump is distal to the proximal interphalangeal joint can often be advanced secondarily. Other options include no treatment, stump excision with or without DIP joint arthrodesis, or flexor tendon reconstruction with a free graft.

Level of Evidence: Therapeutic study, Level V (Expert opinion). See the Guidelines for Authors for a complete description of levels of evidence.

From the *Mary S. Stern Hand Fellow, Department of Orthopaedic Surgery, University of Cincinnati College of Medicine, Cincinnati, Ohio; and the †Department of Orthopaedic Surgery, University of Cincinnati College of Medicine, Cincinnati, Ohio.

The authors certify that there are no commercial associations that might pose a conflict of interest in connection with the submitted article. Correspondence to: Peter J. Stern, MD, P.O. Box 670-0212, Cincinnati, OH 45267-021. Phone:513-961-4263 or 513-558-5592, Fax: 513-558-2220, E-mail: pstern@handsurg.com.

The extreme position of the distal phalanx makes it prone to flexor and extensor tendon avulsion injuries because the fingertips exposed and a tremendous amount of torque can be transmitted through the distal tendon insertions. Distal phalanx extensor tendon avulsions are called mallet (or baseball) fingers, and avulsions of the flexor digitorum profundus insertion on the distal phalanx are called jersey fingers. Though hand surgeons have several methods for treating these injuries, outcomes studies indicate that results are frequently suboptimal.29,46,68

In this review, the authors selected articles which emphasized various aspects of these injuries including mechanism of injury, diagnosis, classification, treatment, and management of complications.

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Mallet Finger

A mallet finger results when there is an extensor tendon insufficiency or disruption over the distal interphalangeal (DIP) joint. Clinically, there is an extensor lag at the DIP joint, and radiographically there may be a variable sized avulsion fracture from the dorsal base of the distal phalanx. Despite its frequency, there is no clear consensus on the proper treatment of mallet fractures. Closed treatment has been recommended for tendon avulsions. Most authors recommend operative fixation for mallet fractures, particularly with significant articular involvement.12,22,23,39 There has been increasing evidence of satisfactory results with closed treatment of mallet fractures with fewer complications.48,68

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Anatomy

The conjoined lateral bands converge to form the terminal tendon over the dorsum of the middle phalanx.56 The terminal tendon averages 10 mm in length and 5.6 mm in width.56 Its longitudinal fibers insert an average of 1.2-1.4 mm from the germinal matrix requiring care during exposure.56,59 A study on the microvasculature showed that the terminal tendon was essentially avascular 11-16 mm from its insertion on the distal phalanx.72 This avascular zone correlated with the portion of the tendon stretched over the middle phalanx with full flexion of the DIP joint.72 Schweitzer and Rayan determined in a kinematic study of the terminal extensor mechanism that the middle finger was at greatest risk for mallet deformity based on its limited tolerance to lengthening, its central location, and length.57 They determined that the ring, small, and index fingers had the greatest potential for mallet deformity after the middle finger. Wehbe and Schneider's reported similar findings in their clinical series on 42 digits.75

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Mechanism and Incidence

Despite the findings of Schweitzer and Rayan,56 most studies disagree on the finger most likely to be affected. Different studies have reported the most involved fingers as the ring, small, and middle.11,23,39,48,60,75 There is also a lack of consensus regarding the mechanism of injury. Sporting activities are reported as causing the majority of mallet injuries in some series,13,39,65,75 but usual household activities or trivial trauma are reported as the most common causes in others.1,66 The mechanism of injury is typically axial loading or hyperflexion of an actively extended DIP joint. This can produce an extensor tendon avulsion from its insertion or with a fragment of bone.1 Less commonly, hyperextension may cause a mallet injury secondary to a dorsal lip fracture as the hyperextended distal phalanx impacts on the head of the middle phalanx.34 A twisting injury of the DIP joint may cause a tear in one of the conjoined lateral bands and cause a mallet deformity.1

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Classification

Several classification schemes have been developed to describe mallet deformities. In 1956, Watson-Jones classified tendinous mallets into Types I-III.74 Type I is a partial rupture with less of an extensor lag than Type II. Type II is a complete avulsion from the distal phalanx. Type III is a complete avulsion with a small flake of bone pulling off with the tendon.74 Regardless of the nature of the tendon avulsion, we believe treatment should be nonsurgical making this classification largely academic. Perhaps the most widely recognized classification is the Wehbe and Schneider system that specifically addresses mallet fractures.75 They divided mallet fractures into three types and three subtypes depending on degree of articular involvement.75 Type I involves a fracture without joint subluxation, Type II involves a fracture associated with joint subluxation, and Type III involves a fracture through the physis or epiphysis.75 The subtypes include: A, less than ⅓ articular involvement; B, ⅓-⅔ articular involvement; and C, more than ⅔ of joint involvement.75 When this classification is applied using historic treatment recommendations, operative management of Type II fractures or subtype B and C fractures is advised.75 However, Wehbe and Schneider75 demonstrated successful management of mallet fractures of variable size with splint immobilization rather than surgical treatment. Doyle14 proposed a classification including soft tissue and bony mallet deformities with more of an emphasis on mechanism (Table 1). These injuries were classified into Types I-IV. Type I is a closed trauma resulting in a tendon avulsion with or without a small fracture fragment, Type II results from a laceration, and Type III results from a deep abrasion with loss of tendon continuity.14 Type IV mallet fingers include three subtypes: transepiphyseal fractures, fractures with 20- 50% of the distal phalangeal articular surface involved, and fractures with greater than 50% of the joint involved with subluxation.14 We believe that most Type I injuries may be treated by closed fixation, and Types II and III are best managed with repair and attention to soft tissue damage. However, it is less clear when deciding management for displaced fractures, fractures involving a large portion of the articular surface, and injures with joint subluxation.47

TABLE 1

TABLE 1

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Treatment

We believe closed treatment produces satisfactory results for tendon avulsions without fracture and minimally displaced or small fractures.10,48,53,63,65,75 Studies have shown that because some extensor lag is expected after treatment, loss of extension at the DIP joint does not correlate with patient satisfaction.48,75 Okafor et al reported on 31 patients with a 5-year mean followup and found high patient satisfaction despite an average 8° extensor lag.48 Garberman et al showed that even delayed splinting of a mallet finger at an average of 53 days from injury resulted in a successful outcome with or without the presence of a small (<30% of articular surface) fracture.57 Katzman et al demonstrated in a cadaver model that PIP motion does not affect terminal tendon gapping in a mallet finger, supporting the practice of isolated DIP joint immobilization.28 Various types of splints have been reported (Fig 1).16,25,30,63,73,77 We prefer a simple dorsal aluminum splint wrapped in mole skin or Coban (3M, St. Paul, MN) to immobilize the DIP joint in slight hyperextension. The patient is instructed to change the splint at least daily, maintaining the DIP joint in extension while the splint is off. We have found that this procedure and weekly office visits, particularly during the first 3 weeks, minimizes skin problems. If dorsal skin ulceration develops then a change to a palmar splint or Stack (Link America, East Hanover, NJ) splint should be considered.

Fig 1

Fig 1

Despite reasonable success with closed treatment of tendinous mallets, operative treatment has been advocated to increase recovery and minimize complications related to splinting.47 Nakamura and Nanjyo proposed a method of internal fixation allowing early mobilization of the DIP joint with superior results compared with Nanjyo's conservatively treated group in an earlier series.47 They used an internal suture technique with a 0.2 mm stainless steel wire secured to the terminal tendon with a figure of eight technique then passed through drill holes in the distal phalanx.47 The repair site was reinforced with a nylon suture and protected by pinning the DIP joint for 3 weeks.47 The pin was then removed in 3 weeks and patients started active DIP joint exercises.47 Tenodermodesis is another treatment for the soft tissue mallet, particularly those associated with a laceration of the terminal tendon. Similar results to splinting have been reported with this technique,44,71 suggesting that splinting alone may be a viable option even with an open injury.

We believe that most bony mallets can be treated nonoperatively (Fig 2). Rather than making an operative decision based on the percentage of articular involvement or the amount of displacement of the mallet fragment, we evaluate subluxation of the distal phalanx in the lateral radiograph with the DIP joint splinted in extension. We consider operative intervention if there is lack of collinearity of the distal and middle phalanges secondary to palmar subluxation of the distal phalanx. Clinical reports48,55,65,75 have shown satisfactory results with closed treatment despite the presence of a large fragment and even subluxation. Wehbe and Schneider75 found that the articular surface remodeled to maintain congruity and preserve the joint space. Closed treatment of a poorly reduced large fragment with or without volar subluxation will likely result in a dorsal prominence and extensor lag. The desire to minimize these outcomes has driven continued interest in operative treatment. Lubahn found superior cosmetic and functional results using open reduction compared with splinting.39 He recommended surgery only for “certain patients” in which a “more perfect result is desirable.”39

Fig 2A

Fig 2A

There are various surgical options for mallet fractures. Authors have reported on an extension block technique.13,23,26,27,50 This technique (Fig 3) involves the percutaneous placement of a dorsal blocking pin at a 45° angle through the terminal tendon just proximal to the fragment. Extension of the distal phalanx then reduces the fragment and the reduction is held with a second pin placed longitudinally across the DIP joint. An optional third pin may be passed into the fragment. Hofmeister et al found a 92% good or excellent result with this method. Various other techniques have been described including internal suture,4 tension banding,12 screws,32, or compression pins,78 and several arrangements of K wires.3,22,66 In a biomechanical analysis, Damron and Engber found a tension band suture technique to most reliably prevent irreversible loss of reduction.11 If we elect operative intervention, we prefer open reduction of the mallet fragment under direct visualization. This procedure can be accomplished under local anesthesia. The joint is approached through a dorsal H shaped incision. Care must be taken not to injure the terminal tendon during the approach. Next, the defect in the base of the distal phalanx is exposed and the fibrous tissue carefully curetted from the defect. A K pin (0.9 or 1.1 mm) is driven antegrade out the distal phalanx, the mallet fragment is anatomically reduced into the defect, and the pin is driven retrograde across the mallet fragment into the head of the middle phalanx (Fig 4). The DIP joint is immobilized in a dorsal splint for 4-5 weeks, the pin is removed, and an active ROM exercise program is initiated. During the postoperative immobilization period the proximal interphalangeal joint should be left free to permit unrestricted ROM.

Fig 3A

Fig 3A

Fig 4

Fig 4

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Complications

High complication rates have been reported with closed and operative treatments. Stern and Kastrup reported on 123 mallet fingers and found a 53% complication rate in surgically treated mallets and a 45% complication rate using splints.68 Seventy-six percent of complications resulted in long-term disability with high rates of nail deformity, joint incongruity, infection, and pin failure. The complications associated with splinting tended to be transient, usually in the form of skin ulcerations (35%). King and colleagues found a 41% complication rate with open reduction and pin fixation of mallet fractures.29 The most frequent complications were marginal skin necrosis and recurrent flexion deformity.29 Some extensor lag is likely with operative and conservative treatment; however, this does not appear to result in patient dissatisfaction or functional deficit.47,48 Given the number of permanent complications associated with operative management, we use nonoperative treatment except for irreducible fracture-subluxations.

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Chronic Mallet

In our experience, persistent mallet deformity with a residual extensor lag often does not result in a functional deficit. We have found some patients complain of the appearance of the finger or that it catches when placed into a pocket. Chronic mallet is typically defined as 4 or more weeks from the date of injury.17,49 Patel et al reported on a series of 10 patients treated at an average of 8 weeks after injury (range, 4-18 weeks) with five excellent, four good, and one fair result.49 Excellent results were defined as DIP joints with equal active flexion and extension as the uninvolved contralateral joint, with no extension lag.49 Good results were digits with a 10° extension lag and full flexion.49 These patients were treated with a Stack splint (Link America, East Hanover, NJ) for 10 weeks of continuous splinting and 2 weeks of night splinting.49 Two patients had recurrence of the deformity after splinting and were placed in the splint for an additional 8 weeks with subsequent good results.49 Garberman et al reported similar results with mallet fingers treated at an average of 53 days from injury using a Stack splint (Link America) or a dorsal aluminum splint.17 The delayed group in this series had an average 10° extensor lag after 7 weeks of continuous splinting compared to a 9° extensor lag in the early treated group after the same amount of splinting.17 We also believe mallet injuries that present 4-8 weeks after injury without a fixed deformity should initially be treated with splinting.

If closed treatment fails some patients complain it is awkward to use the finger, or they express concern regarding the finger's appearance. Occasionally, a swan neck deformity will develop making it difficult to initiate flexion at the PIP joint.1 A fairly simple and effective choice is a central slip tenotomy commonly attributed to Fowler.5,20,40 This procedure can be done under local anesthesia and involves isolating and cutting the central slip close to its insertion on the middle phalanx. Several authors have demonstrated considerable improvement in extensor lag after this procedure as well as improvement in PIP joint hyperextension.5,8,20,24,40 Care must be taken not to damage the triangular ligament as there is the possibility of creating a boutonniere deformity. Thompson et al originally described the spiral oblique retinacular ligament reconstruction (SORL) for chronic mallet deformity.70 A palmaris longus or plantaris tendon graft is fixed to the base of the distal phalanx through an osseous tunnel and routed dorsal to the DIP joint and volar to the PIP joint where it is ultimately fixed to the proximal phalanx through a transverse bone tunnel.70 Kleinman and Petersen reported a series of 12 patients with a passively correctable chronic mallet deformity treated with a modification of the oblique retinacular ligament reconstruction (Fig 5).31 They utilized soft tissue attachments for the graft rather than bone tunnels.31 The DIP joint was fixed with a K wire in full extension and the PIP joint at 10°-15° of flexion.31 The PIP joint was allowed to move at 3 weeks of immobilization, and the DIP joint was allowed to move after 6 weeks of immobilizaton.31 All 12 patients had correction to full extension or slight hyperextension with no functional compromise observed in those with slight active hyperextension.31 Successful results have also been reported with excision of the scar and suturing of the terminal tendon or with reconstruction of the terminal tendon with free palmaris graft or a lateral band of the extensor tendon.38,62

Fig 5

Fig 5

We prefer a central slip tenotomy to SORL reconstruction because of its simplicity and proven track record. The SORL procedure is anatomically appealing, but there is a risk of overcorrection that results in interphalangeal joint stiffness or boutonniere deformity. We prefer DIP joint arthrodesis and headless screw fixation in patients with a fixed contracture with or without degenerative changes.

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Flexor Digitorum Profundus Avulsions: Pathophysiology and Etiology

Avulsion injuries to the insertion of the flexor digitorum profundus (FDP) are commonly referred to as jersey fingers. This eponym is derived from the cause of injury, frequently seen in American football, when a tackler grabs an opponent's jersey with the tip of the finger while the opposing player pulls away.36 The mechanism of injury is one of forced hyperextension of the distal interphalangeal (DIP) joint while the finger is actively flexing. In the absence of previous attrition to the flexor digitorum profundus (FDP) tendon because of an inflammatory process or irritation from a hook of hamate nonunion, the weakest point in the FDP musculotendinous unit is at its insertion onto the distal phalanx.45 With forced hyperextension to the flexed finger the FDP can avulse from the distal phalanx, with or without attached bone, and retract proximally to a variable degree.35 These injuries are common; however, there are no large series suggesting the true incidence.

In 1977, Leddy and Packer published a classic paper on 36 patients with FDP avulsion injuries.36 They proposed a three type classification system that is still used for its simplicity and clear treatment implications.36 Modifications to this classification system have been proposed as different variations of FDP avulsions have been recognized (Table 2).2,36,61

TABLE 2

TABLE 2

In Type I FDP avulsions the stump of the tendon retracts into the palm and the vincula longus and brevis are ruptured. The proximal migration of the stump is limited by the lumbrical origin. After these injuries, a myostatic contracture may quickly develop. It has been hypothesized that this is from loss of nutrition to the tendon as the entire vincular blood supply is disrupted. Surgical mobilization of these tendon avulsions is generally considered ideal when treating these injuries in the first 7-10 days.36

Type II FDP avulsions occur when the tendon retracts to the level of the proximal interphalangeal (PIP) joint. The tendon stump is usually held at this level by the preserved attachment of the long vinculum. A fleck of bone may be present at the tendon stump and may also help to keep the tendon from retracting more proximally as the bony fragment may get caught in the chiasm of the flexor digitorum superficialis (FDS). Though early treatment of Type II injuries is recommended, successful outcomes have also been reported as late as 3 months after injury.36 The possible success of late treatment is attributed to the preserved vincular blood supply and the less significant retraction of the tendon.36

Type III FDP avulsions occur when there is a large osseous fragment attached to the distal stump. The fragment prevents retraction of the stump proximal to the A4 pulley, and both the vinculum longus and brevis are preserved. Early open reduction and internal fixation of the bony fragment is the treatment of choice.36

Type IV FDP avulsions occur when there is a combined bony avulsion from the base of the distal phalanx and a tendon avulsion. Two separate injuries need to be addressed. This injury pattern was first recognized by Robins and Dobyns in 1974; subsequent case reports have also been published.15,33,54,61 In 1981, Smith61 proposed that Type IV FDP avulsions be included in the Leddy and Packer classification.36 The presumed mechanism occurs when a large bony fragment is first avulsed from the distal phalanx that gets caught at the A4 pulley.33 Continued force is exerted through the tendon and then avulses from the bony fragment that remains caught in the A4 pulley.33 A combined injury was reported when two separate traumatic events occurred 5 months apart.15

Al-Qattan proposed a modification of Leddy and Packer's classification where an FDP avulsion with an osseous fragment is associated with an additional distal phalanx fracture.2 This pattern, considered a Type V FDP avulsion, would have unique treatment considerations given possible difficulty in achieving fixation of the multiple fracture fragments avulsed into a distal phalanx.2 Al-Qattan further divided these Type V avulsion fractures into extraarticular (Type Va) and intraarticular (Type Vb) because these two subtypes were treated differently in his series of four patients.2

The relative incidence of each of these injuries is difficult to extrapolate from the literature. It has been reported that 50% of FDP tendon avulsions are associated with bone fragments.15 However, it is unclear what proportion of these were large fragment caught at the A4 pulley. Leddy and Packer did not specify the number of patients with each type of injury, but they noted that “Type II is the most common type.”36 Moieman and Elliot were more specific. In their series of nine FDP avulsions, six were Type II and three were Type III.46 It seems reasonable to assert that Type II avulsions are the most frequent type of avulsion encountered, followed by Type III. Types I, IV, and V are less common.

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Diagnosis

A patient with a FDP avulsion injury typically is injured on the athletic field.36 The injured finger gets caught in an opposing player's jersey while the opposing player is pulling away. The nature of the injury is often unappreciated, and the patient often finishes the game. The pathognomonic finding on physical examination is inability to flex actively the DIP joint (Fig 6). Most patients will also have ecchymosis, pain, and swelling of the involved finger.36 This pain and swelling may obscure the diagnosis by inhibiting active flexion of the entire finger. We test the DIP joint in isolation so as not to overlook the injury. Ecchymosis, pain, and swelling may also be relatively absent from the finger with an FDP avulsion.64 With such an unremarkable appearance of the finger, and with normal active ROM of the PIP and MP joints, the examiner may again miss the diagnosis unless active flexion of the DIPJ is specifically tested.

Fig 6A

Fig 6A

Once there is clinical suspicion of an FDP avulsion, it is important to palpate the flexor tendon of the involved finger. Frequently the point of maximal tenderness represents the stump of the avulsed tendon, allowing the surgeon to appreciate the proximal extent of the retraction preoperatively.64 If the physical exam does not reveal the location of the distal tendon stump, magnetic resonance imaging (MRI) can be useful. An ultrasound done by an experienced ultrasonographer can also determine the proximal retraction of the FDP stump.9 In our opinion, in the acute setting, additional imaging is generally unnecessary because such studies rarely change the treatment recommendation; however, in a chronic injury, it may be difficult to determine if the tendon has retracted into the palm. Tendon stump location alters treatment options. Radiographs are also necessary to identify whether or not there is a large osseous fragment that will require fixation. When there is a small osseous fragment the examiner can ascertain the exact location of proximal retraction.

The ring finger is most frequently affected, although FDP avulsions have been reported in every finger including the thumb. Leddy and Packer reported that the ring finger was involved in 75% of patients.36 Several authors have postulated on why the ring finger is most frequently involved, but a common hypothesis in all studies is that the ring finger has the least independent motion of all the fingers.15 Leddy and Packer asserted that the limited independent MP joint extension because of the junturae tendinae predisposed the ring finger to these injuries.36 Gunter proposed that the ring finger had limited independent ROM because of its central positioning relative to the common muscle belly of the FDP to the long, ring, and small fingers.21 Lunn and Lamb proposed that the bipennate structure of the ring finger lumbrical tethered its FDP and limited independent ROM.41 Manske and Lesker found that the insertion of the ring finger FDP was weaker than in the long finger.42 Bynum and Gilbert showed that the ring fingertip becomes 5 mm more prominent and absorbs more force than the other fingers during grip.7 The ring finger's predisposition to FDP avulsion is clearly multifactorial.

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Treatment

The treatment of FDP avulsions depends on the time elapsed since the injury, the extent of proximal retraction, and the size of the bony fragment. Because of finger dysfunction of the finger without active flexion of the DIP joint, it is generally recommended that all FDP avulsions recognized acutely be repaired primarily.36 If the injury is not recognized immediately primary repair may be impossible, and other reconstructive procedures may be considered.36

In Type I injuries, Leddy and Packer reported that the tendon became necrotic and retracted if not treated in the acute phase.36 They recommended primary reattachment of the avulsed tendon to the distal phalanx in the first 7- 10 days after the injury.36 The tendon end was retrieved in the palm, and the necrotic distal portion was carefully debrided while taking care to avoid unnecessary handling of the proximal tendon.36 They used a 3-0 braided nonabsorbable suture on a tapered needle while two separate locking stitches were placed into the stump of the tendon so that a four strand repair could be accomplished over a button.36 The tendon and suture were then threaded through the fibroosseous tunnel to the distal phalanx.36 This can often be accomplished by using a looped 26-gauge wire threaded in a retrograde direction inside the flexor tendon sheath.36 A trough was then made in the distal phalanx just distal to the DIP joint volar plate.36 This trough should be large enough in diameter to seat the full tendon stump, but should not penetrate the full depth of the cortical bone.36 They then used a 0.9 mm K wire and drilled two tunnels through the base of the trough in a volar proximal to dorsal distal direction.36 The sutures were passed through these tunnels using a free needle and tied over the nail plate using a button.36 Prior to tying the suture, it is important to verify that the tendon stump is well seated in the trough.36 The fixation sutures were typically removed 6 week postoperatively. We recommend the Duran protocol for postoperative rehabilitation similar to repairs of a zone 1 FDP laceration.

This technique has its drawbacks. The suture can act as a nidus for infection and penetration of the nail plate can lead to a nail plate deformity. Because the sutures are removed 6 weeks postoperatively, this method depends on fairly rapid tendon to bone healing. There are other methods of fixation for FDP avulsions that may avoid some of these pitfalls. One alternative is to make a dorsal transverse incision proximal to the nail germinal matrix and to tie the suture anchors down over the bone.58 This method avoids potential damage to the nail plate, avoids the risk of late infection, and provides permanent fixation of the tendon to the bone. However, it can be quite challenging to tie the suture down in the narrow zone between the terminal tendon proximally and the germinal matrix distally. Also, the subcutaneous knot from the nonabsorbable suture tied over the bone proximal to the nail plate is prominent and a source of skin irritation. Despite purported advantages, we do not recommend this technique.

Using suture anchors avoids a dorsal incision and potential nail deformities and provides permanent fixation of the tendon to the bone.6,58 A cadaveric study tested the load to failure of three different methods of fixation: a pullout button using 3-0 monofilament nylon and a two strand repair; a 1.8 mm suture anchor using 3-0 braided polyester and two strand repair; or two 1.3 mm suture anchors using a 3-0 braided polyester suture for a four strand repair.6 The load to failure using the two 1.3 mm suture anchors was the strongest, with the most frequent mode of failure being suture breakage.6 While the study indicated excellent relative load to failure strength of the suture anchors, it did not address the possibility of fatigue failure of the anchor bone interface. We believe this method holds promise and we await clinical data to substantiate its efficacy.

Type II FDP avulsions retract to the level of the PIP joint.36 Thus, the techniques for acute repair of Type I injuries are applicable to Type II FDP avulsions. It is easier to mobilize the tendon to its insertion if repair is accomplished soon after the injury because the stump does not tend to become necrotic or to retract to the same degree as Type I injuries.36 This relative preservation of the tendon stump presumably is attributable to the intact vascular supply which persists through the vinculum longus. Leddy and Packer reported a successful primary repair of a Type II avulsion 3 months after the injury.36 Provided that the tendon stump appears relatively healthy, we agree with Leddy and Packer that delayed primary repair of a Type II injury is reasonable even long after the acute period has passed.

There can be a gray zone between Type I and Type II injuries. Sometimes the stump retracts proximal to the PIP joint, but not into the palm.36 If the retraction is proximal to the PIP joint it can be assumed that the vinculum longus is ruptured, and should be managed as a Type I injury. In such a circumstance, the tendon may be difficult to mobilize distally.. If this occurs, the injury should likewise be treated as a Type I injury.

Type III injuries are FDP bony avulsions that are caught in the A4 pulley (Fig 7). These bony fragments are usually large enough to internally fix with at least two minifragment screws or K wires. The vascular anatomy to the FDP insertion has recently been reported.37 The FDP insertion is unique in that it primarily receives its blood supply from continuations of intraosseous vessels within the distal phalanx. However, the vinculum brevis also provides a robust vascular supply to the tendon which extends from the dorsal surface to the palmar surface of the tendon. This vincular supply extends to within 1 centimeter of the FDP insertion onto the bone.37 Because the vinculum brevis is generally preserved in Type III injuries, the tendon remains relatively healthy allowing late primary repair.

Fig 7A

Fig 7A

Type IV FDP avulsions are defined as injuries that have a large bony fragment incarcerated at the A4 pulley and retraction of the tendon into the finger or palm.61 These are rare injuries and are not usually anticipated at the time of surgical exploration unless a careful preoperative examination indicates an area of tenderness proximal to the bony avulsion. Treatment requires a combination of techniques used for Type I -III injuries. Langa and Posner repaired the tendon to the bone fragment and then secured the bony fragment to the distal phalanx using a wire over a pullout button.33 The single wire construct was used to fix both injuries.33 Eglseder and Russell treated the two injuries with separate constructs.15 The bony fragment was fixed with a 2 mm cortical screw supplemented with an intraosseous wire. The tendon stump was then secured to the distal phalanx with a pullout wire.15 We have been successful in removing the bony avulsion and directly attaching the avulsed tendon to the defect at the base of the distal phalanx.

Al-Qattan reported that Type V FDP injuries involve an avulsion associated with a large bony fragment in combination with a distal phalanx fracture.2 Type Va injuries involve an extraarticular fracture fragments and Type Vb injuries include intraarticular injuries.2 Al-Qattan treated type Va injuries with pullout sutures tied over a dorsal button.2 Fracture stability was achieved by passing each limb of the pullout suture through a different fracture fragment.2 In Type Vb injuries the intraarticular component of the fractures may render the DIPJ unstable, so the DIP joint was first stabilized with a K wire prior to reduction and fixation of the tendon avulsion with a pullout button.2 Given the complexity of these injuries, the goal should be to fix the large osseous fragment attached to the FDP stump to the portion of the distal phalanx attached to the extensor mechanism. If there is remaining comminution, additional fragments may need to be fixed depending on the condition of the associated soft tissues. The goal of any additional fixation should be to allow protected ROM immediately postoperatively.

Flexor digitorum profundus avulsions frequently present long after injury. If these injuries are Type II or Type III injuries then delayed primary repair is still a consideration. However, the retracted tendon in a chronic Type I injury is not amenable to repair.36 Once the diagnosis of a chronic Type I injury has been made, it is important to appreciate the nature of the patient's complaints (Table 3). Many patients will adjust to the loss of DIP flexion and we recommend no treatment. Other patients experience some loss of PIP joint flexion. These patients are best served by an aggressive therapy regimen18 or tenolysis of the FDS. Patients often have associated pain in the palm at the site of the distal stump, which can be treated by debridement of the tendon stump. Other patients complain of instability of the DIP joint of the affected finger. This loss of active DIPJ flexion is especially problematic in the index finger, but is usually tolerated in the ring finger.41 A DIPJ arthrodesis is appropriate treatment for these patients. Some patients present late after a Type I FDP avulsion and insist on active DIP joint motion. If full passive ROM is restored, and if the patient demonstrates the ability to work diligently with hand therapy, a tendon reconstruction may be considered.18,64

TABLE 3

TABLE 3

Flexor digitorum profundus grafting with an intact FDS tendon should be undertaken cautiously. It is a technically demanding procedure, and results have been directly linked with surgeon experience.69 For a patient to be satisfied with ring finger grafting, adequate DIP joint range of motion must be achieved. Unlike the index or long finger where adequate strength with limited ROM lead to successful pinch, the ring finger DIP joint needs significant active ROM to increase grip strength for small objects.76 Pulvertaft reported that 50% of patients with isolated FDP grafts were able to touch their fingertip within 0.5 in of their distal palmar crease.51,52 Eighty-six percent of patients achieved 30° of active ROM at the DIP joint, while only 9% achieved 70° of active DIP joint ROM.51 McClinton et al43 reported a series of 100 isolated FDP grafts in which the graft was placed around the FDS decussation. A two stage reconstruction was not necessary in any of their patients, but 17 patients required subsequent tenolysis.43 The average DIP joint ROM was 48°, and 80% of their patients had successful outcomes.43 However, 13 fingers were considered failures secondary to loss of PIP joint ROM.43 Several authors have suggested that grafting is only appropriate in patients younger than 21 years.19,52,67 However, grafting has been shown to be successful in older patients who are motivated and have full passive motion.43 Considering the potential for failure, most authors agree that FDP grafting is an appropriate procedure in an index and long finger of a young, motivated patient, but that it is rarely indicated in the small finger.43,76 In a ring finger, it can be considered only if there is a specific reason, for instance if the patient is a musician.35

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Outcomes

It is difficult to extract information on outcomes after surgery for FDP avulsions because of the limited number of large case series. Leddy and Packer reported on 36 patients with FDP avulsions; 12 had reinsertion of the tendon into the bone. The patients had a 10°-15° loss of extension at the DIP joint, good return of flexion, and almost equivalent grip strength compared to the unaffected hand.36 The best information on results after FDP avulsions was reported by Moieman and Elliot.46 They studied the results of 102 fingers with Zone 1 FDP injuries; nine were FDP avulsions.46 Of the nine avulsions, six were Type II and treated by primary reinsertion to the bone.46Three were Type III avulsions and treated by open reduction and internal fixation (ORIF).46 They found that patients with isolated distal FDP injuries can be expected regain most of their motion at the PIP joint but there were problems regaining motion at the DIP joint.46 Of the nine patients with FDP avulsions, 66% had poor DIP joint ROM in Type II and Type III injuries.

The current techniques of primary tendon to bone repair of FDP avulsions during the acute period generally do lead to a satisfactory functional outcome. Patients should be counseled preoperatively about losing greater than 1/2 their overall arc of motion at the DIP joint, resulting in a lack of full extension.

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