Correction of Crossover Toe Deformity

Abstract

Crossover toe deformity cannot be corrected in the same way as for a claw toe or hammertoe. If correction is undertaken using a standard metatarsophalangeal (MTP) joint release with arthroplasty of the interphalangeal (IP) joint, the deformity will invariably recur, because the associated contracture is in the transverse plane. Ideally, stability in the transverse plane should be enhanced, but at the same time, flexibility of the MTP joint and control of any sagittal plane instability should be maintained. To some extent, the success of the operation will depend on the cause of the deformity. The pathogenesis of this condition is assumed to involve a partial or complete tear of the plantar plate, followed by some degree of rupture of the lateral collateral ligaments, followed by dorsomedial and occasionally dorsolateral deviation. The MTP joint should be evaluated for instability with the vertical Lachman test. If the translation of the proximal phalanx is more than 2 mm, then this is indicative of a plantar plate injury in 95% of patients. The advent of the plantar plate repair has improved our ability to treat this condition.

Key Words

crossover toe, plantar plate, Lachman test, repair, tendon transfer, instability

Surgical Approach

Crossover toe deformity cannot be corrected in the same way as a claw toe or hammertoe. If correction is undertaken using a standard metatarsophalangeal (MTP) joint release with arthroplasty of the interphalangeal (IP) joint, the deformity will invariably recur, because the associated contracture is in the transverse plane. Ideally, stability in the transverse plane should be enhanced, but at the same time, flexibility of the MTP joint and control of any sagittal plane instability should be maintained. To some extent, the success of the operation will depend on the cause of the deformity. The pathogenesis of this condition is assumed to involve a partial or complete tear of the plantar plate, followed by some degree of rupture of the lateral collateral ligaments, followed by dorsomedial deviation. The MTP joint should be evaluated for instability with the vertical Lachman test. If the translation of the proximal phalanx is more than 2 mm, then this is indicative of a plantar plate injury in 95% of patients. If additional imaging is desired, magnetic resonance imaging is very effective and noted to be 95% sensitive and 100% specific for the diagnosis of a plantar plate tear.

If the crossover deformity is associated with a long second metatarsal, then the second metatarsal should be shortened. Shortening the metatarsal relieves the medial joint contracture because pressure is taken off the intrinsic tendons, as illustrated in Fig. 8.1 . In this case, the patient presented for treatment 1 year after bilateral hallux valgus correction. An interesting observation is that recurrent hallux valgus did not develop, despite the lack of anatomic barriers to valgus drift of the hallux (see Fig. 8.1A–B ). The lesser toe deformities were treated with shortening osteotomies of the lesser metatarsals. The alignment initially was not ideal but improved somewhat with taping of the toes into varus for 3 months after surgery (see Fig. 8.1C ).

Treating a crossover toe deformity as a claw toe will lead to prompt recurrence of deformity ( Fig. 8.2 ). However, one must not forget to treat any concurrent deformity of the proximal interphalangeal (PIP) joint, with a PIP arthroplasty/arthrodesis required for many patients with long-standing deformity. Treatment of this deformity has evolved over the last few years, with the significant push to primary repair of the plantar plate as opposed to tendon transfer. With the combined approach of a metatarsal osteotomy with plantar plate repair, outcomes at 1 year are promising with significant reduction in pain; however, return to a normal functioning toe is not achieved in many patients, and loss of motion of nearly 25% may occur. A plantar approach has been described with some success as well and mitigates the need for specialized equipment; however, given the risk of a painful plantar scar, neurologic injury, and inability to perform a shortening osteotomy, we prefer a dorsal approach. Although the use of a tendon transfer has decreased with the advent of plantar plate repair, we still present this option, as it does stabilize the toe and does not require any specialized equipment and is more appropriate in cases of frank dislocation. Each patient must be individually evaluated, and for minor cases, a simple osteotomy, associated with a medial collateral release and extensor lengthening, may be sufficient, particularly in lower-demand patients. In elderly patients, when the MTP joint is severely subluxated, with crossover of the toe on the hallux and asymptomatic hallux valgus, amputation of the toe may be a very reasonable option. The hallux does not drift further because it typically is abutting the third toe already, and the removal of the painful second toe is generally a very successful procedure for the patient ( Fig. 8.3 ).

Components of Surgical Correction

Incision and Dissection

The incision begins at the MTP joint, with an adequate soft tissue release of the dorsal and medial contracture. The extensor hood is identified and is incised longitudinally medial to the extensor digitorum longus tendon, which is retracted laterally. The attachment of the extensor hood to the base of the proximal phalanx must be maintained, and a transverse dorsal capsulotomy is performed. On the dorsal-medial aspect of the MTP joint the collateral ligament is now released. This can be cut at its attachment to the proximal phalanx or the metatarsal head, but the volar plate ligament should be maintained.

Oblique Metatarsal Head Osteotomy (Maceira Osteotomy)

The indication for oblique metatarsal head osteotomy (the Maceira osteotomy) is instability of the MTP joint in either the sagittal or the transverse plane in patients with a relatively long metatarsal. In this section, the osteotomy procedure is described for correction of a transverse plane deformity such as the crossover toe. The Weil or Maceira osteotomy is also necessary for correction of any other medial or lateral deviation of the lesser toes off the metatarsal head, such as with severe valgus or abduction of the toes or with generalized varus or adductus of the toes associated with hallux varus. The goal of the operation is to slightly shorten the metatarsal head, releasing the intrinsic contracture on either side of the MTP joint. This procedure is also performed in conjunction with treatment of subluxation or dislocation of the MTP joint, occasionally in the setting of metatarsalgia, when instability is present in addition to the crossover or varus deformity ( Fig. 8.4 ).

Despite the popularity of the Weil osteotomy and indeed our own extensive experience with this procedure, its unpredictability with respect to the axial alignment of the toe after the surgery is a recognized problem. It has certain advantages: decompression of the joint is excellent, and shortening can be readily accomplished. Nevertheless, this type of osteotomy has been shown in both clinical and laboratory settings to result in slight elevation of the axis of the intrinsic tendons dorsal to the center of the metatarsal head. The force exerted by the extensor tendons is then augmented by the slight dorsal shift in the intrinsic tendons, which do not as effectively plantarflex the MTP joint. The toe is therefore slightly shortened and also slightly elevated off the ground, causing what has been referred to as the “floating toe deformity.” Lengthening of the extensor tendons may aid in minimizing the risk of a “floating toe,” but it must be done with some caution, as over-lengthening of the extensors may result in total loss of extensor tone with the toe “dragging” and “floppy,” which can interfere with gait in barefoot walking.

To some extent, this elevation can be limited but not reversed entirely, with vigorous plantar flexion exercises of the MTP joint that begin soon after surgery. The flexor-to-extensor transfer is not the definitive operation for correction of instability because it too may be associated with complications, including stiffness and patient dissatisfaction with the use of the toe. Nonetheless, in the presence of a dislocated MTP joint, a shortening osteotomy of the metatarsal of some type is necessary, and the Weil osteotomy is an effective procedure to reduce this dislocation. It is not an ideal procedure for correction if isolated metatarsalgia is present, however, because alternative osteotomies are available that do not result in elevation of the toe. Surprisingly, in view of the plane of the osteotomy, avascular necrosis of the metatarsal head is extremely rare, and although arthritis of the MTP joint may occur, it is uncommon.

The role of the flexor-to-extensor transfer in treatment of a crossover toe deformity is not clear cut. This procedure was used fairly frequently a decade ago but was associated with problems of sufficient magnitude, including recurrence of deformity, that we do not often use this transfer for a crossover toe. Instead, we use an osteotomy when needed and a plantar plate repair or extensor brevis transfer. If the extensor brevis procedure fails intraoperatively, we use the flexor-to-extensor transfer procedure. If the MTP joint is dislocated, plantar plate repair is theoretically ideal to attempt to achieve stability of the toe; however, the remaining plantar soft tissue may be too attenuated for repair. In addition, this typically requires an aggressive capsulotomy with extensor lengthening to balance the forces. If the plantar plate repair is not possible and the toe is persistently unstable, then a flexor-to-extensor transfer is performed. The tendon transfer should not be used to forcibly reduce a dislocated or subluxated MTP joint; the role of the tendon transfer is to provide stability following reduction, otherwise recurrence will surely occur.

The incision for the metatarsal osteotomy is made and located according to the number of metatarsals to be cut. If the correction is focused on a single metatarsal, an incision is made directly over the MTP joint. If two adjacent metatarsals require osteotomies, then the incision is made between them (e.g., in the second interspace). Although performance of the central three metatarsal osteotomies through a single incision located over the third MTP joint is possible, it entails too much stretching of the skin with the potential for wound breakdown. We therefore prefer to use either two incisions, one medial to the second MTP joint and then one slightly lateral to the fourth, or a single transverse incision ( Fig. 8.5 ). The incision is deepened through the subcutaneous tissue, and the extensor tendons are lengthened, particularly in the setting of any subluxation, dorsiflexion contracture, or dislocation. A dorsal capsulectomy is performed to expose the metatarsal head, and a curved periosteal elevator is inserted into the MTP joint if it is dislocated. As it is levered down, the metatarsal head becomes visible. Care is taken not to injure the articular surface as a curved periosteal elevator is inserted. If the joint is dislocated, the volar plate must be stripped off the underside of the metatarsal head, to facilitate scarring down of the volar plate under the neck.

With the metatarsal head visible, the cut is planned at the apex of the metatarsal head. The cut must avoid the articular surface and must be at the level of the neck dorsal to the articular surface. The cut is made at a 30-degree angle, but the angle will vary according to the declination of the metatarsal. It typically is extended for approximately 2 cm, which corresponds to the length of the saw blade used. The cut is completed, and a second cut is made just vertically perpendicular to the axis of the metatarsal. This second cut, according to Maceira, allows precise measurement of the amount of shortening required for the osteotomy. The third cut is then made as a slice or with resection of a small wedge of bone along the axis of the metatarsal. The metatarsal head now is reduced directly onto the distal end of the metatarsal osteotomy, without any overhang of the dorsal surface of the metatarsal on the articular surface as seen with the Weil osteotomy ( Fig. 8.6 ).