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The type IV flexor digitorum profundus avulsion is a rare injury involving fracture of the volar base of the distal phalanx and separation of the tendon from the fracture fragment. Recommendations for management are sparse and are substantiated only by a few isolated case reports. We recently encountered two of these injuries, both of which proved challenging, particularly with regard to joint incongruity and tendon adhesions. In reviewing the literature, it is apparent that no consensus exists regarding surgical strategies. However, based on our experience and that of other authors, we can suggest the following: (1) high index of suspicion of this potentially deceptive injury, with use of magnetic resonance imaging or ultrasound if preoperative confirmation is needed; (2) rigid bony fixation that prevents dorsal subluxation of the distal phalanx; (3) tendon repair that is independent of the bony fixation; and (4) early range of motion therapy.
Flexor digitorum profundus (FDP) avulsions or jersey fingers are injuries with which most hand surgeons are familiar, whether they involve separation of the tendon from the distal phalanx or fracture of the distal phalanx at the tendon’s insertion. Relatively few, however, have encountered the injury involving both a fracture and a separation of the tendon from the fracture fragment, the so-called type IV FDP avulsion. Because of its rarity, there is little evidence to guide treatment and to warn against potential complications. Our group recently encountered two such injuries, both of which proved challenging. In discussing these cases we will review the literature and provide suggestions for the management of these injuries.
A 21-year-old collegiate defensive tackle sustained an injury to his left ring finger while rushing the passer. His trainer diagnosed an FDP avulsion and placed him in a splint. When seen in our clinic 3 days later, the digit was extensively ecchymotic, especially at the pulp and distal interphalangeal (DIP) level. There was no active flexion at the DIP, and there was moderate edema and tenderness at the volar P1 area. Plain films revealed an avulsion fracture involving the volar 50% of the base of P3, volarly rotated 90°, with dorsal subluxation of the remainder of P3 (Fig..1).1). On operative exploration, a type IV FDP avulsion was discovered, with the tendon retracting to the level of P1. The fragment and the tendon stump were secured simultaneously, using a 2-0 prolene suture woven through the tendon, passed through both the fragment and the remainder of P3 via two Keith needles, and tied over a button. Intraoperative fluoroscopy demonstrated acceptable reduction of the fracture and correction of the subluxation. On postoperative day3, he was referred to our therapist for initiation of a Duran-type rehabilitation protocol. On his return to clinic on postoperative day11, plain films showed displacement of the fragment and recurrent subluxation. He was returned to the operating room the following day, when closed reduction and percutaneous longitudinal pin fixation were performed. Therapy was resumed at postoperative day3. The K-wire was removed at 1 month. Plain films taken at 3 months showed significant joint incongruity and persistence of subluxation. The digit was pain-free but the range of motion of the DIP joint was only 0–30° passive and 10–20° active. At 1 year, his motion was unchanged, but because the digit caused no functional limitations, he declined further treatment.
A 52-year-old male injured his right ring finger while pulling on the starter cord of a power washer. He was seen in the ER the next day, diagnosed with a distal phalanx fracture, and his finger was placed in a splint. In our clinic the following day, the ring finger was ecchymotic distally, with severe tenderness over the DIP and in the region of the A1 pulley. There was no active DIP flexion. Plain films showed a comminuted fracture of the base of P3 with moderate displacement of the volar fragment and no subluxation (Fig. 2). A magnetic resonance imaging (MRI) was obtained, demonstrating retraction of the tendon to the proximal P2 level. In the OR, the fractures were reduced and fixed with a longitudinal K-wire and a 1.0-mm cortical screw. The tendon was then repaired with 2-0 prolene passed through the main portion of P3 and tied over a button. Duran-type rehabilitation protocol was begun on postoperative day3. Plain films demonstrated anatomic alignment of the fracture, articular congruency, and good positioning of the screw. At 5 months, he had 55° passive and 15° active range of motion at the DIP joint. The potential need for tenolysis was discussed, but the patient was subsequently lost to follow-up.
In 1977, Leddy and Packer  published their classic article describing their series of 36 FDP avulsions. Although the injury had been recognized and described much earlier in numerous case reports and small series [1, 3, 4, 7, 8, 13, 14, 20], they were the first to classify the injury into three types (Table 1). In type I, the tendon is avulsed at the insertion and retracts into the palm, tethered only by the lumbricals. As the vincula are ruptured, the tendon stump is potentially devascularized, and repair should theoretically be performed promptly (7–10 days) or ischemic degeneration might ensue. In type II, which is the most common type, the long vinculum remains intact, tethering the tendon stump at the proximal interphalangeal (PIP) level and maintaining its blood supply. These injuries can be reconstructed weeks or even months later. In type III, the tendon is avulsed along with a large bony fragment that catches on the distal tendon sheath, preventing retraction beyond the head of the middle phalanx.
Absent from Leddy and Packer’s original classification was what we now call type IV, which is similar to type III except that the tendon separates from the bony fragment and retracts proximally into the finger or palm, as in type II or I injuries, respectively. This unusual variant was first mentioned in the literature by Böhler in discussing Carroll and Match’s 1969 presentation; in his experience, he claimed a 50% incidence of this yet-unnamed type of avulsion . The first formal report came in 1974 by Robins and Dobyns , followed in 1981 by Smith , who was the first to suggest that it be classified as a type IV injury. Several case reports followed [2, 5, 6, 9, 10, 16, 18, 19], and counting the cases of Robins and Dobyns and Smith, there have been a total of 19 reported cases in the literature (preceding ours).
The details of these 19 cases are collated in Table 2. The mean patient age was 35 years (range, 16–53), and the most common mechanism was pulling on a jersey (53% of cases for which the mechanism was specified) or a starter cord (24%). The ring finger was affected in 94% of specified cases, consistent with most series of FDP avulsions (the ring finger’s susceptibility probably has a multifactorial basis, including a relatively longer length in the grasping hand, a weaker tendon insertion , and less independent movement owing to the common flexor muscle belly  and juncturae tendiniae ).
In 53% of cases, the tendon retracted to the level of P2 or the PIP joint, as with a type II avulsion, and in the remaining 47%, it retracted to the level of P1 or the palm, as with a type I avulsion. In theory, in the latter situation, which we have called subtype I, the vincula are ruptured, while in the former, subtype II, the vincula remain intact and tether the tendon in the middle of the finger. By this definition, our first case was subtype I and the second subtype II, although we did not observe the status of the vincula in our cases nor was it mentioned in any of the reviewed case reports. The implication, of course, is that subtype I injuries would require early repair from the standpoint of tendon vascularity.
Importantly, in only 35% of reviewed cases—and in neither of ours—was the level of tendon retraction signaled by a small fleck of bone on plain film. MRI and ultrasound are therefore valuable diagnostic tools in this situation. If such a test is not obtained, the vigilant course would be to approach all suspected type IV injuries as subtype I injuries with early intervention.
As can be seen in Table 2, surgical approaches were widely variable. Unfortunately, it is difficult to compare these approaches, as postoperative protocols were largely omitted and outcomes inconsistently reported. However, a few inferences can be drawn.
First and foremost, most authors fixed the fragment and attached the tendon separately, and in general, their reported outcomes were very good. Of the various means of bony fixation, cortical screws [5, 19] seemed to result in the best range of motion at the DIP joint, although K-wires [15, 17, 18] and pullout wires [2, 5, 6, 16] also yielded good outcomes. Three authors added a K-wire oriented axially [2, 16] or as a dorsal blocking pin  to prevent dorsal subluxation of P3; this wire did not seem to diminish results substantially.
In contrast, only one author attempted to hold the fragment and tendon simultaneously with a single pullout wire . Although the patient healed strongly and had a pain-free joint, her range of motion was relatively poor.
One author used a miniplate from a craniofacial set for the fracture and sutured the tendon to the miniplate . The patient’s range of motion was outstanding—the best in our review. The plate and screws were said to be palpable but not problematic.
In two reports, the fragment was excised; in one case , this was performed by another surgeon and, in the other , as part of a planned volar plate arthroplasty. A stable joint with good range of motion was achieved in both patients.
DIP arthrodesis was performed for three patients, all seen late and all with subtype I injuries . In this situation, tendon advancement and direct repair is impossible. If the joint is stable and painless, no treatment is necessary, but if not, arthrodesis is the most predictable option. In rare circumstances, a tendon graft may be attempted but only in highly motivated and understanding patients .
As for our cases, results have thus far been disappointing. Both patients have achieved bony union (albeit with suboptimal joint congruity in the first case) but have minimal active range of motion at the DIP joint, despite early range of motion therapy. At presentation, both digits were notable for substantial ecchymosis, and blood within the tendon sheath undoubtedly contributed to the adhesions that restrict them today. While generally good outcomes were reported in the literature, we believe that such difficulties are not atypical and suspect that many surgeons have encountered similar problems with adhesions in previous (unreported) instances of type IV injuries.
Nonetheless, from our experience, we would recommend independent repairs of the bone and tendon, as rigid fixation of the fracture is of paramount importance if an early motion rehabilitation protocol is to be successful. Cortical screws appear to be preferable, assuming the bone stock is sufficient. We would not hesitate to add an anti-subluxation K-wire if fixation were uncertain, even if this delays the onset of therapy.
Our cases of type IV FDP avulsion demonstrate the difficulties that can be encountered in the surgical treatment of this rare injury. Pitfalls include missed or delayed diagnosis, joint subluxation or incongruity, and flexor tendon adhesions. From our experience and review of the literature, we recommend (1) MRI or ultrasound if the diagnosis is suspected and preoperative confirmation is required, (2) rigid bony fixation including stable correction of subluxation, (3) independent tendon repair, and (4) early range of motion therapy.
No financial conflict of interest exists on the part of any of the authors with any commercial entity whose products are described, reviewed, evaluated, or compared in this manuscript. No external funding was utilized.