A Simple Modification of Extension Block Pinning for Mallet Fractures

 A Simple Modification of Extension Block Pinning for Mallet Fractures

Surgery for mallet fractures has evolved. Generally, the direction of the evolution has been from open procedures to closed procedures and from direct procedures to indirect procedures. Extension block pinning has become the most popular procedure for mallet fractures, although several modifications have been reported since Ishiguro et al first introduced it in 1988.

Despite the simplicity of the procedure, complications, apart from extension loss or arthrosis, persist. Pins exposed out of the skin can be a source of complications, including infection. Further, they keep patients from washing their hands postoperatively. This leads to considerable inconvenience, and surgeons sometimes feel pressured to remove the pins early because of poor patient compliance. To avoid these problems, the current authors placed the tips of the pins under the skin while performing extension block surgery. In this article, the authors describe this modification and report its outcomes.

The authors addressed 2 key questions. First, are there any complications specifically related to burying the tips of the pins under the skin? Second, are the fracture union and the final range of motion sound after this modified surgery?

This retrospective review of prospectively enrolled subjects received institutional review board approval. The authors reviewed 14 patients with mallet fractures treated with extension block surgery. Surgical indications were involvement of more than one-third of the articular surface and/or volar subluxation. All procedures and assessments were performed by a single orthopedic surgeon (S.-H.S.) with 5 years of hand specialty experience. The modification—placing pin tips under the skin—has been applied since 2014, and these 14 consecutive patients underwent the modified procedure. Mean age of the patients was 31 years (range, 13–66 years). There were 2 teenagers, but their distal phalangeal epiphyses were fused. Mean time from injury to surgery was 18 days (range, 2–60 days). Mean follow-up was 14 months (range, 3–25 months).

The surgery was performed under digital block anesthesia using an image intensifier (Video; Figure 1A). The pins used were 0.9 or 1.1 mm in diameter, except for three 0.7-mm extension block pins used for patient 3. The extension block pin was inserted first percutaneously into the head of the middle phalanx. The pin was placed in the midline of the middle phalanx and inserted until it just penetrated the volar cortex. Next, the distal phalanx was extended for fracture reduction, and a pin was inserted across the distal interphalangeal joint to maintain extension and reduction. The pin was inserted from either the volar aspect of the distal phalanx or the distal tip of the distal phalanx until it reached the subchondral bone of the proximal phalangeal base. All pins were cut short enough to place their tips under the skin, and the skin was pressed around the pins with the pin cutter (Figure 1B). Next, the pins were buried under the skin by squeezing the skin around them (Figure 1C). The final position of the pins was confirmed with the image intensifier (Figures 1D–E). A bulky dressing was applied with or without an aluminum finger splint, which remained in place for no more than 2 weeks. Patients were cautioned about possible pin breakage with heavy load. They were allowed to wash their hands 4 to 5 days postoperatively, without any dressing or splinting (Figures 1F–G). The pins were later removed under digital block anesthesia in the day-surgery unit, once fracture union had been confirmed on plain radiographs. When the tip of a pin was buried deeply under the skin, a No. 11 blade was used to make a small (2-mm) stab incision, which was simply dressed without suture (Figure 2). Modified extension block pinning for mallet fracture. Preoperative lateral radiograph (A). All pins were cut short enough to place their tips under the skin, and the skin was pressed around the pins with the pin cutter (B). The pin tips were buried under the skin by squeezing the skin around them (C). Pin position immediately after the surgery on image intensifier (D, E). The patient's finger 2 weeks postoperatively (F, G). The patient was allowed to wash his hand 4 to 5 days postoperatively. Removal of the extension block pin. A small (2-mm) stab incision was made with a No. 11 blade (A). The pin was held with a holder while the skin around it was pressed and then the pin was pulled out (B, C).

Complications specifically related to burying the tips of the pins under the skin were evaluated by (1) comparing the pin positions between the day of extension block surgery and the day of pin removal and (2) reviewing whether there were infections, skin breakdown, or other pin-related complications. Regarding outcome, (1) union of the fracture on plain radiographs and (2) active range of motion of the distal interphalangeal joint at final follow-up were evaluated. Mean time from surgery to removal of the pins was 8 weeks (range, 6–10 weeks). The pins maintained their initial position, and no pull-out, subsidence, bending, or breakage was observed. No patient developed infection or other complications in the pin site. Solid union was achieved in all 14 fractures. Mean time to union was 6.4 weeks (range, 4–9 weeks). Mean extension lag at final follow-up was 4° (range, 0°–20°), and mean distal interphalangeal joint flexion was 75° (range, 45°–90°). Clinical characteristics and outcomes of the 14 patients are summarized in the Table. Characteristics and Outcomes of the 14 Patients With Mallet Fractures

The tips of pins exposed out of the skin after extension block surgery for mallet fractures is an annoying inconvenience. Some surgeons apply finger splints postoperatively for not only the stability of the distal interphalangeal joint but also the protection of the pin tips. The latter might be of more importance when applying a splint after mallet finger pinning, considering that Kirschner wires themselves have been used as internal splinting for mallet fingers since the 1950s. Because pin tips may be sharp enough to cause an injury and may be the source of complications including infection, they should be protected. This protection keeps patients from performing everyday activities such as hand washing. This inconvenience lasts until pin removal at 6 to 8 weeks. One of the best ways to protect pin tips is to place them under the skin. This reduces pin-related complications and allows patients to wash the pin site. This simple change makes a great difference, especially when the pin is in the hand. In the current study, some of the patients had to wash their hands for their jobs and were able to do so soon after the surgery. To the authors' knowledge, there have been no reports of burying pin tips under the skin in mallet fracture surgery. This may be because the soft tissue in the dorsal aspect of the distal interphalangeal joint is thin or there is the risk of pin subsidence. However, the current authors had an inverse idea: if the pin tip is placed under the skin, the thinness of the soft tissue may protect the pin from pressing force. Indeed, the pins maintained their initial positions and no subsidence was observed. Because no other complications were observed, the authors believe that burying pin tips under the skin is a feasible option for extension block surgery of mallet fractures. The other concern regarding burying the pin tips involves whether it hampers the fracture union or final function of the digit. Possible loss of blocking effect may be a concern because of the short length of the extension block pin. However, because the extension block pin is inserted in an angle that the pin tip is located distally, the fracture fragment is trapped stably between the bones and the block pin as long as the pin maintains its initial position. In practice, the union was sound in all of the authors' cases. The authors achieved active range of motion comparable to that of previous reports. In addition, with the pin tips buried under the skin, the current authors may not remove the pins until fracture union is evident on plain radiographs, given the improved compliance of patients. Some studies have reported pin removal at 6 weeks postoperatively, although the reported mean time to union was more than 6 weeks. Thus, sometimes the pins are removed before fracture union, due at least to some extent to patients' inconvenience or the fear of pin-related complications including infection. However, when the pin tips are buried under the skin, delaying pin removal is more tolerable for both the patient and the surgeon. Although the current patients had expected irritation at the pin sites, especially in the finger pulp, they were willing to wait until fracture union because they could wash their hands and perform most of their everyday activities.

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