Dorsal dislocation of the interphalangeal joint of the great toe is rare. It results from a hyperextension injury to the joint. Closed reduction is often attempted in the emergency setting, but this measure is seldom successful owing to invagination of the sesamoid-plantar plate complex into the interphalangeal space. The classic treatment, open reduction, is indicated when closed reduction fails1-12.
In this report, attempts at closed reduction were unsuccessful in two patients. A novel technique of percutaneous reduction of the incarcerated sesamoid was then performed, leading to a successful reduction. Both patients and their families were informed that data concerning the case would be submitted for publication, and they consented.
Surgical Technique
With the patient under local, regional, or general anesthesia, a small stab incision is made over the extensor hallucis longus tendon. Under fluoroscopic guidance, a 1.0-mm Kirschner wire is introduced through the extensor tendon head and the dorsal capsule toward the invaginated sesamoid while traction is applied to the distal phalanx. The Kirschner wire is then used as a joystick to lever the sesamoid away from the head of the proximal phalanx and into the joint and then to push it plantarward (for Miki type-II injuries) (Fig. 1-A)1. To avoid fracturing the sesamoid, the Kirschner wire is not drilled into it but is manipulated by hand. Adequate reduction is then confirmed by noting that the distal phalanx is clinically unstable, and the sesamoid is restored with use of fluoroscopy to its original location plantar to the interphalangeal joint. Obstructed interphalangeal joint flexion and extension suggest reduction of the sesamoid into the joint space and conversion of a type-II to a type-I dislocation (Fig. 1-B)1. The procedure should then be repeated until the sesamoid is reduced to the plantar surface (Fig. 1-C). Miki type-I dislocations can be addressed in a similar manner.
Other instruments besides the Kirschner wire, such as a dental probe or a Freer elevator, may be used to similar effect. However, the Kirschner wire is advantageous because (1) it is of small enough caliber to fit within the confines of the joint, leaving but a puncture wound on the dorsum, and (2) it will bend if excessive force is used to lever an unyielding sesamoid, providing tactile feedback to the surgeon that either the maneuver should be refined or the open technique should be considered instead. With a more robust implement, sesamoid fracture may result instead, leaving no alternative but to resort to open reduction.
Case 1. An eighteen-year-old man fell from a chin-up bar onto the left foot, sustaining a hyperextension injury to the interphalangeal joint of the great toe. In the emergency department, there was swelling and tenderness of the left great toe with the distal phalanx being hyperextended and the skin dimpled over the dorsum of the interphalangeal joint. There was a 2-mm burst laceration over the medial plantar aspect of the joint. Neurovascular examination revealed no abnormality. Radiographs revealed a Miki type-II dislocation of the interphalangeal joint1, with the distal phalanx dorsally displaced (Fig. 2-A) and the sesamoid entrapped in the joint. Closed reduction was attempted without success.
With the patient under general anesthesia, closed reduction with fluoroscopic guidance was again unsuccessful (Fig. 2-B). After adequate lavage of the medial plantar burst laceration, percutaneous reduction of the incarcerated sesamoid-plantar plate complex was performed. Fluoroscopy revealed an acceptable reduction (Fig. 2-C). However, in view of perceived joint laxity, the joint was opened through a dorsal incision and the interphalangeal joint space was examined visually to confirm that there was no residual tissue interposed between the phalanges. The dorsal incision was closed, and the joint was then immobilized with an axial 1.25-mm Kirschner wire. At four weeks, the Kirschner wire was removed.
At six months, the patient reported mild stiffness at the interphalangeal joint, but he had returned to active sports, including basketball. On examination, interphalangeal range of motion was reduced to 40°, whereas metatarsophalangeal joint range of motion was normal. Radiographs revealed normal anatomy and alignment of the great toe (Fig. 2-D).
Case 2. A thirty-four-year-old male motorcyclist skidded while trying to avoid an oncoming vehicle and sustained a hyperextension injury to the left great toe, in addition to multiple superficial abrasions of other parts of his body. In the emergency department, examination was remarkable for marked swelling and deformity of the left great toe. The distal phalanx was hyperextended and displaced dorsomedially. Radiographs revealed a Miki type-II dislocation with the sesamoid interposed between the two phalanges (Fig. 3-A). Unlike the case of the first patient (Case 1), the distal phalanx was dislocated dorsomedially instead of dorsally. The dislocated interphalangeal joint was refractory to attempts at closed reduction.
With the patient under general anesthesia, closed reduction was again unsuccessful. This was followed by percutaneous reduction of the incarcerated sesamoid-plantar plate complex with a Kirschner wire that proceeded uneventfully. Joint laxity was again noted after the reduction. The interphalangeal joint was then immobilized with an axial 1.6-mm Kirschner wire. The Kirschner wire was removed at one month, and the joint remained stable at two months.
At two years, the patient was noted to have mild residual interphalangeal joint stiffness that did not bother him. The range of interphalangeal joint motion was 35°, and the range of metatarsophalangeal joint motion was normal. Radiographs revealed preservation of the joint space and alignment (Fig. 3-B).
Dorsal dislocation of the interphalangeal joint of the great toe is a rare injury. The anatomy of the joint makes closed reduction difficult to achieve, with one author noting successful reduction in only two of twenty-two patients in the available literature1. Furthermore, in up to 44% of patients, the interphalangeal sesamoid is invisible radiographically1, leading to difficulty not only in diagnosing sesamoid incarceration but also in confirming a successful reduction. It is also possible to convert a Miki type-II dislocation into a type-I dislocation by moving the sesamoid-plantar plate complex from a dorsal position into the joint between the phalanges. This occurred in six of twenty-two patients1.
Open reduction is necessary once attempts at closed reduction are unsuccessful. Most surgeons advocate a dorsal1-3,5,6 or medial4,7,8 approach. With the dorsal or dorsolateral approach, the extensor tendon may be retracted aside, or split9,10, with the latter affording better surgical exposure5.
In this report, an alternative technique is proposed on the basis of a few anatomical principles. In an anatomical study of the great toes of a single cadaver, Miki et al.1 discovered that (1) the thick plantar plate is separate from the flexor hallucis longus tendon and can easily displace into the joint; (2) the sesamoid is almost completely buried within the plantar plate, allowing the sesamoid-plantar plate complex to move as a single unit; (3) the plantar plate is connected to the proximal and distal phalanges by fibrous tissue, which prevents dislocation; (4) the plantar plate does not displace into the joint space as long as either connection to the proximal or distal phalanx remains intact; and (5) the plantar plate can only dislocate into the joint space with both proximal and distal phalangeal connections divided.
With the anatomy defined as such, interphalangeal joint dislocations can then be divided into two groups. In type-I dislocations, the sesamoid-plantar plate complex slips into the joint, resulting in minimal elongation of the great toe but no marked deformity. In type-II dislocations, the sesamoid-plantar plate complex slips into the plantar aspect of the joint and emerges dorsally with the sesamoid overriding the head of the proximal phalanx, leaving the distal phalanx in hyperextension. Both patients described in this report fall into this latter group.
Examination of the position of the distal phalanx allows one to distinguish between the two types. In type-I dislocations, the distal phalanx is in a neutral position, and displays resistance to dorsiflexion and plantar flexion. In type-II dislocations, the distal phalanx is hyperextended and displays little resistance to dorsiflexion.
An examination of anteroposterior and lateral radiographs confirms the type of dislocation. In type-I dislocations, the sesamoid is visualized within a widened joint space and the phalanges are coaxial. In type-II dislocations, the sesamoid is located dorsal to the head of the proximal phalanx and the distal phalanx is hyperextended.
In both types of injury, reduction is difficult because of intact collateral ligaments, which tighten when the joint is distracted by the sesamoid (type I) or when it is hyperextended (type II)1.
Percutaneous reduction makes use of two principles. First, the sesamoid is inseparable from the plantar plate, and the entire sesamoid-plantar plate complex moves as a unit. The sesamoid is not, as was previously believed, attached to the flexor hallucis longus2. Second, the sesamoid can be visualized radiographically to confirm a successful reduction of the sesamoid-plantar plate unit. However, it must be remembered that while the sesamoid is present in up to 95% of cadaver feet, it is radiographically visible in only 56% to 93% of ambulatory patients1, depending on the radiographic technique employed. In patients in whom the interposed sesamoid is not apparent radiographically, an open approach is mandated when closed manipulation fails.
One potential risk of this procedure is trauma to the extensor tendon during Kirschner wire passage, although it is unlikely to be of a greater degree than other tendon-splitting dorsal approaches9,10. Another theoretical possibility is sesamoid fracture resulting from excessively forceful Kirschner wire manipulation coupled with inadequate traction to distract the joint space. This situation may arise in patients who are seen late and have had joint contracture set in, firmly fixing the sesamoid in the joint space. It may thus be prudent to apply this technique only to patients with acute presentations and those who display sufficient joint laxity under traction.
After reduction, the joint displays increased laxity. Radiographs made after reduction may reveal a widened joint space. In our first patient (Case 1), the surgeon resorted to open visual inspection to confirm a successful reduction without tissue interposition within the joint space. In retrospect, this was unnecessary as the laxity arises from overstretching of the capsule and collateral ligaments at the time of injury1,5 rather than from residual interposed tissue. To address joint laxity after reduction, we prefer temporary Kirschner-wire immobilization5,11, although other methods of stabilization, including bulky dressing3, buddy strapping6,7, splinting1,8, and immobilization in a short leg cast1,12 for up to four weeks1,7,11, have been described. The ideal method of stabilization is subject to debate.
Although Leung and Wong noted that, on removal of fixation, further dislocation is rare and the long-term prognosis is excellent5, late joint stiffness occurred in both of our patients who were treated with a similar (four-week) period of immobilization. We will consider a shorter period of Kirschner-wire immobilization for future patients.
In conclusion, percutaneous reduction of a dorsally dislocated interphalangeal joint of the great toe is an alternative to open reduction following failed closed reduction and is based on an understanding of interphalangeal joint anatomy. Its advantages are that it can be easily performed by surgeons of varying levels of experience, and it avoids open surgery.