Modified Extension-Block K-wire Fixation ...

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Modified Extension-Block K-wire Fixation Technique for the Treatment of Bony Mallet Finger SANG KI LEE, MD; KAP JUNG KIM, MD; DAE SUK YANG, MD; KYUNG HO MOON, MD; WON SIK CHOY, MD

abstract Full article available online at OrthoSuperSite.com/view.aspx?rID=00000 This article describes the treatment of a bony mallet finger deformity using 2 extension-block Kirschner wires (K-wires) with a transarticular K-wire fixation technique for precise alignment of the terminal extensor tendon–bone relationship and effective immobilization of the distal interphalangeal joint. Twenty-nine patients (33 fingers) with a bony mallet finger deformity and fracture fragment involving more than onethird of the articular surface were treated surgically. The fracture fragment was fixed and the mallet finger deformity was corrected in all patients using modified extensionblock K-wires (2 dorsal extension-block pins) with a transarticular K-wire (volar side pin) fixation technique. Active motion of the proximal interphalangeal and metacarpophalangeal joints was not restricted. The wires are removed in the clinic 6 weeks postoperatively when the bridging trabeculae were observed in the radiographs, and immobilization in a stock splint was continued for an additional 2 weeks. According to Crawford’s evaluation criteria, there were 24 (73%) excellent, 7 (21%) good, and 2 (6%) fair results. Three patients showed radiological signs of mild degenerative changes, which did not limit their daily activities. Nail ridging occurred in 3 cases (9%), which disappeared after an average of 6 months with normal growth, and mild scarring at the dorsal pin site occurred in 2 cases (6%). Modified extension-block K-wires with a transarticular K-wire fixation technique is an acceptable alternative treatment modality for the management of bony mallet finger deformities with or without subluxation of the distal phalanx.

Drs Lee, Kim, Yang, Moon, and Choy are from the Department of Orthopedic Surgery, Eulji University College of Medicine, Daejeon, Korea. Drs Lee, Kim, Yang, Moon, and Choy have no relevant financial relationships to disclose. Correspondence should be addressed to: Sang Ki Lee, MD, Department of Orthopedic Surgery, Eulji University College of Medicine, 1306 Dunsan-dong, Seo-gu, Daejeon 302-799, Korea (sklee@ eulji.ac.kr). doi: 10.3928/01477447-20100826-10

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Figure: Surgical technique of the modified extension-block K-wires with transarticular K-wire fixation. Two extension-block pins were placed in the maximum flexion position of the distal interphalangeal joint (top). The fragment was reduced to an extension block by traction and extension of the distal phalanx (middle). Movement of the distal interphalangeal joint was blocked by volar-side Kwire insertion to avoid damage to the dorsal fragment (bottom).

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A

disruption of the extensor mechanism’s insertion into the base of the distal phalanx causes a characteristic flexion deformity of the distal joint known as a mallet finger.1 Mallet finger injuries are common in the work environment or during sports activities.2 The condition normally results from the sudden forced flexion of an extended distal interphalangeal joint causing an interruption of the terminal extensor mechanism, or an axial loading of the fingertip along with hyperextension at the distal interphalangeal joint producing a fracture of the dorsal lip at the base of the distal phalanx.1 As the extensor tendon excursion is only 3 mm at the distal interphalangeal joint level, functional and aesthetic problems can result from a failure to restore the delicate balance of extension and flexion forces as well as the integrity of the bone and tendon unit precisely. As a result of the small range excursion of this section of the tendon, a 0.5-mm distension can lead to a 10 extension deficit, and a 2-mm distension can cause a 40 extension deficit.3,4 Although the hand deficit is minor, treatment is sought for cosmetic reasons, as well as for the inconvenience of the finger becoming caught on everyday objects or impeding many recreational activities. However, patients are not always managed appropriately, more so because there is considerable controversy regarding the problem. Pain-free stability in the distal interphalangeal joint is essential for an effective and stable pinch. Many studies have reported that conservative treatment provides satisfactory results in patients in whom there is either pure extensor tendon avulsion or fracture-avulsion of less than one-third of the base of the distal phalanx, even as late as 3 months after the injury.5-7 Several authors have recommended surgery when the fracture involves more than one-third of the articular surface to avoid chronic instability, joint subluxation, osteoarthritic deformity, and cosmetically unacceptable outcomes.1,8-10 Healing of a displaced

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bone fragment can lead to an extensor lag and swan-neck deformity.11 A range of surgical techniques for bony mallet fingers have been reported, including the use of Kirschner wires (K-wires), figure-ofeight wiring, screw fixation, internal sutures, tension band fixation, compression fixation pins, mini-external fixator, and mini-plate fixation.9,12-18 However, several complications have been encountered, including infection, nail deformity, joint incongruities, fixation/hardware failure, and secondary deformity.19 Several authors have described percutaneous procedures that allow an indirect anatomical reduction of the fractures to avoid the disadvantages of the open method.12,20,21 In 1988, Ishiguro et al12 described extension-block pinning, which consists of a dorsal extension block K-wire and a second wire to hold the distal interphalangeal joint in extension. This simple and reliable method has been modified by several authors to improve the accuracy of the reduction and the stability of fixation.22-24 In addition, during surgery with the extension-block method, a transarticular pin for fixation of the distal interphalangeal joint often passes the fracture surface in patients in whom the fragment size of the mallet fracture is relatively larger. In these patients, the distal interphalangeal joint is fixed in subluxation to the volar side while reduced bone fragments are redisplaced or the fracture sites are split. A more accurate reduction and stable fixation can be achieved when 2 small extension-block K-wires (0.9 mm) are used, producing a more favorable outcome. This article describes the treatment of a bony mallet finger deformity using 2 extension-block K-wires with a transarticular K-wire fixation technique for precise alignment of the terminal extensor tendon–bone relationship and effective immobilization of the distal interphalangeal joint.

MATERIALS AND METHODS This study was approved by the Institutional Review Board, and all patients were

available for review. The retrospective study was performed from March 2003 to April 2008. Twenty-nine patients (33 fingers) with a bony mallet finger deformity were treated using 2 extension-block Kwires with a transarticular K-wire fixation technique. Patients with no limitation in passive motion of the distal interphalangeal and proximal interphalangeal joints and no swan-neck deformity were enrolled in this study. The inclusion criteria were: (1) a dorsal intra-articular fracture fragment involving ⬎30% of the base of the distal phalanx with or without volar subluxation of the distal phalanx; and (2) ⬍3 weeks’ delay from the injury without treatment. Patients with comminuted or open fractures were excluded. All procedures were carried out by a single surgeon. The study group comprised 29 patients (33 fingers; 2 patients had 2 fingers treated)—21 men and 8 women—with a mean age of 31 years (range, 17-54 years). The ring finger was the most commonly affected (12 cases), followed by the small finger (8 cases), long finger (7 cases), and index finger (6 cases). According to the Wehbe and Schneider11 classification (Table), there were 12 type IB, 6 type IC, and 15 type IIB injuries. The size of the fracture fragment was recorded as a percentage of the anteroposterior diameter of the base of the distal phalanx, as observed on the lateral radiograph.11 The mean time from the injury to surgery was 16 days (range, 1-22 days). Patients were evaluated clinically and radiologically. The mean follow-up period was 28 months (range, 24-85 months). The patients were assessed for time to union, functional recovery, incidence of complications (elongation of the fracture segment, subluxation, narrowed joint space, degenerative changes, cold intolerance, and nail deformity) and physical capacity. The range of motion of the distal interphalangeal joint of the finger involved was recorded using a forearm goniometer. The functional outcomes were assessed using Crawford’s25 criteria. An excellent

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rating meant full distal interphalangeal joint extension, full flexion, and no pain. A good rating indicated an extension deficit of 0 to 10, full flexion, and no pain. A fair rating meant an extension deficit of 10 to 25, any flexion loss, and no pain. A poor rating indicated an extension deficit ⬎25 or persistent pain. The patients were assessed for pain on a scale from 1 to 4, where 1⫽no pain, 2⫽mild pain occasionally or with hard work, 3⫽mild pain occurring frequently or with daily activities, and 4⫽severe pain restricting their daily activities. In addition, all patients were examined for any changes in sensation at the distal phalanx. Surgical Technique Under digital block anesthesia, the patient is placed on a radiolucent operating table in the supine position. The operation is aided with a digital tourniquet. With the distal interphalangeal joint held in maximum flexion, a 0.9-mm K-wire is introduced just behind the fragment and driven proximally into the head of the middle phalanx at an angle of 30 to its long axis (Figure 1). A second 0.9-mm K-wire is inserted 2 to 3 mm apart from and parallel to the first K-wire. The fracture is reduced with the distal interphalangeal joint in traction and slight extension. In our cases, an accurate reduction could not be achieved using an extension of interphalangeal joint only due to volar subluxation of the distal phalanx. However, accurate reduction was achieved with the concomitant use of a traction force. A 0.9- or 1.2-mm K-wire is then advanced from the volar side of the finger and across the distal interphalangeal joint to hold it in slight extension. Therefore, the K-wire is not across the fracture surface and the dorsal fragment is not damaged (Figure 2). This is the basic principle of this technique to produce an accurate reduction and avoid a displacement or rotation of any dorsal fracture fragment. Fluoroscopic verification of successful fracture reduction and wire position


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Table

Wehbe and Schneider11 Classification of Mallet Fractures Type

Definition

Subtype

Articular Surface

I

No DIP joint subluxation

A

⬍1/3

II

DIP joint subluxation

B

1/3-2/3

III

Epiphyseal and physeal injuries

C

⬎2/3

Abbreviation: DIP, distal interphalangeal.

1

2A

2B

2C

Figure 1: Surgical technique of the modified extension-block K-wires with transarticular K-wire fixation. Two extension-block pins were placed in the maximum flexion position of the distal interphalangeal joint (top). The fragment was reduced to an extension block by traction and extension of the distal phalanx (middle). Movement of the distal interphalangeal joint was blocked by volar-side K-wire insertion to avoid damage to the dorsal fragment (bottom). Figure 2: Lateral radiograph of a 24-year-old man with 45% involvement of the articular surface of the little finger with volar subluxation at the distal interphalangeal joint (type IIB) (A). Lateral (B) and AP (C) radiographs taken immediately postoperatively, demonstrating satisfactory fracture reduction.

should be obtained in all patients. The wires are cut short, and a volar aluminum splint is applied to protect them and prevent movement of the distal interphalangeal joint but allow active motion of the proximal interphalangeal and metacarpophalangeal joints postoperatively. A regular dressing and pin care hygiene is encouraged. The wires are removed in the clinic 6 weeks postoperatively when the bridging trabeculae are observed in the radiographs, and immobilization in a stock splint is continued for an additional 2 weeks. Full active and passive exercises are then initiated.

RESULTS Radiographic bone union was achieved in all patients in a mean of 6.4 weeks

(range, 6-7.1 weeks). The K-wires were removed 6 weeks postoperatively in all patients. The mean size of the bone fragment at the time of the initial injury was 51% of the articular surface of the distal phalanx (range, 38%-71%). The mean extensor lag of the distal interphalangeal joint was 21 (range, 8-37) preoperatively, which was improved to 4 (range, 0-7) postoperatively. Three patients had an extension lag up to 6, and 26 patients showed full extension (Figure 3). The mean flexion of the distal interphalangeal joint was 79 (range, 69-90). Active exercise was started immediately after removing the stock splint (8 weeks postoperatively), and daily activities were not restricted. Three patients (9%) showed radiological signs of mild degenerative changes or

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3A

3D

3B

3E

3C

3F

Figure 3: Initial radiographic view of a 21-year-old woman with type IB mallet fractures of the third and fourth fingers (A). Lateral (B) and AP (C) radiographs taken postoperatively, demonstrating an anatomic reduction of the fractures. Radiograph taken 2 years postoperatively showing satisfactorily healed fractures with congruent joint spaces (D). Photographs showing a full range of distal interphalangeal joint motion (E, F).

joint space narrowing. One of these patients (3%) experienced the clinical symptoms (occasional mild pain) of arthrosis, which did not limit his daily activities. The clinical symptoms of these patients subsided after 6 months without additional surgical intervention. Congruent and satisfactory joint surfaces (anatomical or intra-articular step-off of ⬍1 mm) were present in the remaining 26 patients (30 fingers), and no arthritic changes were observed at the final follow-up. One case of a superficial infection at the pin entry site was treated successfully with oral antibiotics and local wound care. Nail ridging occurred in 3 cases (9%), which disappeared after a mean period of 6 months (range, 4-10 months) with normal growth. There was mild scarring at the dorsal pin site in 2 cases (6%). Four cases (12%) had mild paresthesia at the dorsal and palmar surface of the finger, which improved after a mean period of 4 months (range, 2-7 months) without specific treatment. None of the cases showed avascular necrosis of the fragment, breakage of the K-wire, nail deformity, cold

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intolerance, prominent dorsal bump, or recurrent mallet deformity. Using the Crawford’s evaluation criteria, 24 of 29 patients (33 fingers; 73%) had excellent results, 7 (21%) had good results, and 2 (6%) had fair results. The 2 fair results were attributed to flexion loss of the distal interphalangeal joint (3 and 5, respectively). None of these patients reported pain at the final follow-up and no further treatment was required. There were no poor results due to the precise alignment of the fragments and anatomical restoration of the terminal tendon–bone unit.

DISCUSSION The results of this study demonstrate that good outcomes can be achieved for a bony mallet finger deformity using a modified extension-block K-wire fixation technique with transarticular K-wire fixation. The treatment goals for mallet fractures are to provide anatomical restoration of the tendon and bone integrity with rigid fixation. However, some controversy exists regarding the treatment of a mallet finger deformity.

In the case of a mallet finger fracture, the size of the avulsed fragment is the most important factor when deciding the treatment modality. There is general agreement that acute mallet fingers with tendon rupture or a small fracture fragment involving less than one-third of the articular surface of the distal phalanx should be treated nonsurgically with one of many splints available. Nonsurgical treatment has been proposed by Wehbe and Schneider,11 including in those with subluxation of the distal interphalangeal joint, regardless of the size or amount of fracture displacement. However, frequent follow-up evaluations and patient compliance are essential for nonsurgical treatment. Conservative treatment involving splinting can also have complications, including skin slough, tape allergy, transverse nail plate grooves, splint-related pain, and tender dorsal prominence.8,19 Our technique provides the stability of surgical fixation without relying on surgical exposure or splints, thereby eliminating the associated risks with these treatments. In contrast, treatment is more controversial when the fragment involves more than one-third of the articular surface, and many treatment modalities have been suggested as the best fixation technique for a mallet fracture.9-18 Bischoff et al26 examined the results of tension-band wiring and reported poor results in 21 of 51 patients. Complications included skin breakdown, infection, and secondary displacement. Damron and Engber15 confirmed the high complication rate of tension-band wiring in their series. Wehbe and Schneider11 examined 160 mallet deformities and reported a 33% complication rate in the open surgical-treated group, as opposed to 9% with nonsurgical treatment. However, noncompliance was a major problem in 20% of patients in the splinted group.11 Several authors have described percutaneous procedures to decrease the complications associated with open surgical treatment. When comparing nonsurgical


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treatment with single longitudinal pin fixation without a reduction of the fracture fragment, Auchincloss27 reported similar results in the groups; both groups had an equal complication rate. However, in the splint group, 14% of the patients had local irritation and 11% of the single longitudinal pin group had a superficial infection. The final extensor lag was 6 and 10 in the surgical and splint group, respectively. Finally, the subjective function results were 0% restriction in the surgical group and 9% in the splint group.27 In cases of fracture involving ⬎30% of the articular surface, as well as those in which the symptoms are indicative of an acute injury, the minimally invasive technique of extension-block percutaneous Kwire pinning is an easy, effective, and safe alternative to conservative treatment of displaced mallet fractures.12,20,21,27 Moreover, the method of Ishiguro et al12 is more straightforward than open surgery, and indirect manipulation reduces the possibility of the fragment becoming comminuted. However, when the dorsal fragment is large, markedly displaced, or rotated, it is difficult to control indirectly with a single K-wire. Two parallel extension-block pins 2 to 3 mm apart are used routinely to achieve better control of the dorsal fragment. The technique of wire insertion is similar to that of the original Ishiguro et al12 method but the wires are smaller (0.9 mm) and are inserted at a lower angle (30 to the axis of the middle phalanx). Anatomical reduction can be obtained without difficulty using 2 extension-block K-wires because they create a wall that prevents the rotation of even a large fragment when a reduction force is applied. Parallel and lower-angled wires make contact with a wide area of the fragment, which is strongly compressed when the distal phalanx is extended, thereby achieving and maintaining better reduction. In addition, the use of smaller wires is less traumatic and reduces the number of pin-related complications. There was no damage to the dorsal fragment during the procedure.


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In our study, during transarticular Kwire fixation a pin was inserted on the volar side of the distal phalanx. Anatomically, the distal phalanx has a smaller intramedullary space than other types of phalanx, and the volar side cortex is concave. Therefore, the angle cannot be adjusted during longitudinal pin fixation. Fixation should be performed along the shape of the intramedullary space. Accordingly, in cases in which the size of the bone fragments is greater, the pin often penetrates the fracture surface, resulting in the displacement of bone fragments. This leads to a loss of reduction, interference with fracture healing, and subluxation of the distal phalanx to the volar side. To resolve these problems, Ishiguro et al12 reported that a transarticular K-wire should be introduced from the radial or ulnar side rather than from the distal end. However, in these cases—those in whom the size of the fracture fragment is relatively larger— the K-wire passes the fracture line and cannot achieve secure fixation of the distal interphalangeal joint. In addition, Pegoli et al28 modified the transarticular K-wire fixation technique and performed transarticular fixation under such conditions that the distal interphalangeal joint was flexed. As a result, they reported an extensor lag in 54% (35/65) of cases.28 In our study, the mean size of the fracture fragment was 51%. This corresponds to larger bone fragments in most cases. Accordingly, if longitudinal K-wire fixation should be performed first from the tip of the distal phalanx, the K-wire would pass the fracture surface in most cases. Therefore, a K-wire was fixed from the volar side of the distal phalanx to the midphalanx. The location and angle of insertion can be adjusted if a K-wire needs to be fixed on the volar side. Therefore, there are advantages in that fixation can be performed by maximally avoiding the fracture site. In addition, in cases where there is subluxation in the distal interphalangeal joint, after inserting a pin in the distal phalanx a compression force

should be exerted and the subluxation of the distal interphalangeal joint should be reduced accordingly. A pin should then be progressed and the distal interphalangeal joint should be fixed. Hence, an anatomical reduction of the distal interphalangeal joint can be achieved. In our series, there were no complications related to the use of transarticular K-wires. The mean time from the onset of trauma until surgery was 16 days (range, 1-22 days). The surgical indications were determined to be relatively acute cases. As in chronic mallet finger fractures, removal of the callus to realign the correct anatomical relationship cannot be accomplished using percutaneous techniques. Therefore, complete functional recovery and a satisfactory outcome are dependent solely on remodeling. An inability to access the distal interphalangeal joint correctly, potential injury to the tenuous soft tissue envelope, and a reduction of the small articular fragments have been reported to be percutaneous procedure-related problems.8,12 Accordingly, scars, debris, or callus between the fracture surfaces should be removed effectively in cases of a chronic bony mallet finger. An open procedure might be essential for a precise restoration of the bone–tendon integrity. In our experience, unstable pattern fractures of the distal phalanx require a precise reduction of the fracture, adequate joint reduction, and proper buttressing of the dorsal fragment to obtain satisfactory remodeling and prevent further deformity, stiffness, arthritis, and other complications. There were some limitations to our study. First, it was a retrospective review of a single surgeon’s experience. Second, the meticulous reduction and careful pinning technique is a demanding procedure. Transient nail ridging occurred after vigorous manipulation or repetitive reduction maneuvers in patients with volar subluxation of the distal interphalangeal joint and marked displacement of a fracture fragment. Dorsal scarring occurred after repeated insertion of the dorsal pin due to

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■ Feature Article

extensor tendon injuries of the hand. Can J Surg. 1973; 16(6):366-375.

technical error. Although technically demanding, this procedure provides both accurate and secure fixation of the fragment. Overall, modified extension-block Kwires with a transarticular K-wire fixation technique provides an alternative and acceptable treatment modality for the treatment of bony mallet finger deformities with or without subluxation of the distal phalanx.

10. Stark HH, Gainor BJ, Ashworth CR, Zemel NP, Rickard TA. Operative treatment of intra-articular fractures of the dorsal aspect of the distal phalanx of digits. J Bone Joint Surg Am. 1987; 69(6):892-896.

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3. Chang P. Extensor tendon repairs in zones 12. In: Blair WF, ed. Techniques in Hand Surgery. Baltimore, MD: Wiliams & Wilkins; 1996:91-96. 4. Damron TA, Engber WD, Lange RH, et al. Biomechanical analysis of mallet finger fracture fixation techniques. J Hand Surg Am. 1993; 18(4):600-607. 5. Garberman SF, Diao E, Peimer CA. Mallet finger: results of early versus delayed closed treatment. J Hand Surg Am. 1994; 19(5):850-852. 6. Warren RA, Norris SH, Ferguson DG. Mallet finger: a trial of two splints. J Hand Surg Br. 1988; 13(2):151-153. 7. McFarlane RM, Hampole MK. Treatment of

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