Claw Toe

The extensor tendon crosses and is held over the MTP joint by an aponeurotic band of fibrous tissue. Although it does not insert into the proximal phalanx, it is able to dorsiflex the proximal phalanx of the MTP joint through this aponeurotic band, which goes around the MTP joint and is inserted onto the plantar plate (see the image below).

The extensor tendon splits into three parts over the proximal phalanx. The central slip attaches itself to the dorsal aspect of the base of the middle phalanx. The medial and lateral slips rejoin distally to insert on the dorsal aspect of the base of the distal phalanx (see the image below). The extensor tendon is only capable of extending the PIP and DIP joints when the MTP joint is in neutral flexion; otherwise, this is accomplished by the intrinsic musculature.[4, 5, 6, 7]

The intrinsics are made of the lumbricals, which are strong extenders of the PIP and DIP joints by virtue of their attachment onto the extensor sling and the interossei. Interossei are weak extensors of the interphalangeal (IP) joints because so few fibers reach the extensor sling. Furthermore, when the MTP joint is hyperextended, the lumbrical power in extending the PIP and DIP joints is reduced because of a mechanical disadvantage.

The flexor digitorum longus (FDL) tendon inserts into the plantar aspect of the distal phalanx, and the flexor digitorum brevis (FDB) inserts onto the middle phalanx. Thus, no major antagonist to dorsiflexion of the proximal phalanx is present. Hence, when the proximal phalanx dorsiflexes, static tightening of the flexors occurs, which subsequently flexes the PIP and DIP joints. Stabilization of the lesser MTP joint comes from the static restraint of the plantar plate and the collateral ligaments.

The collateral ligaments have been reported as the primary stabilizers of the lesser MTP joint. The two sets of collateral ligaments both emanate from the lateral metatarsal head. The phalangeal collateral ligament inserts into the proximal phalanx, and the accessory collateral ligament inserts onto the plantar plate. The plantar plate is attached from the base of the proximal phalanx to an origin on the metatarsal head, just proximal to the plantar articular cartilage.

When the collateral ligaments and plantar plate lose resiliency or are stretched through repetitive dorsal directing forces on the proximal phalanx from ground reactive forces, the proximal phalanx dorsiflexes. Without a strong plantar flexor attached to the proximal phalanx, the proximal phalanx remains in dorsiflexion, and the PIP and DIP joints subsequently flex (see the image below).

When the flexed position of the PIP and DIP joints remains constant, the collateral ligaments fibrose along the sides of the PIP and DIP joints, and the position of their joints becomes fixed. When this occurs, the claw toe deformity becomes rigid, whereas previously it was considered flexible. This separation of flexible and rigid most often occurs at the PIP joint.

Claw toe deformity results from altered anatomy or neurologic deficit that leads to an imbalance between the intrinsic and extrinsic musculature to the toes.[8, 9]

The prevalence of claw and hammer toe deformities is in the range of 2-20%, gradually increasing with advancing age. Accordingly, claw toe is most often seen in patients in the seventh and eighth decades of life. Women are affected four to five times more than men are. Little is mentioned in the literature regarding these deformities in non-shoe-wearing populations.[10, 11, 12, 13]

Most people have no underlying disease responsible for the claw toe deformity, but it can occur in association with neuromuscular diseases, such as multiple sclerosis, Friedreich ataxia, Charcot-Marie-Tooth disease, cerebral palsy, mild dysplasia, stroke, and lumbar nerve-root impingement. Metabolic diseases such as diabetes and inflammatory arthropathies such as rheumatoid arthritis and psoriasis can also be accompanied by claw toe deformity.

The experiences of other authors indicate that complete correction of the toe is necessary to achieve the best result. Of course, this presumes careful attention to detail and a toe with normal vascularity.

Taylor[14]  and Pyper,[15]  via transfer of both the long and the short flexor to the extensor hood without bony resection, achieved only 72% and 51% good results, respectively. Pyper also noted that with soft-tissue procedures alone, the deformity recurred and results were somewhat unpredictable.[15] Therefore, Frank et al[16]  and McCluskey et al[17]  recommended PIP resection along with soft-tissue procedures to realign the toe.

Barbari et al[18]  reviewed 31 patients who had surgery on multiple toes. These authors concluded that the best cosmetic results were achieved in younger patients, and they noted that active or passive motion in the IP joints was present in 60% of these cases. Of course, restriction in range of motion (ROM) is an intended outcome of the procedure. Patients must be aware that in most instances, they will sacrifice prehensile action of the toe for less pain, will have better shoe-wearing capabilities, and, ideally, will have an improved cosmetic result.

Specific disease entities seem to fare similarly; Cyphers et al[19]  reported 60% good results in patients with myelomeningocele.

A prospective multicenter observational study of 117 patients requiring PIP joint realignment who underwent placement of angled intramedullary implants found that implantation resulted in a high rate of fusion and a good outcome.[20]  None of the patients with incomplete joint fusion who had a stable joint with no pain required reoperation.

Patients with claw toe deformities can present with a variety of symptoms related to the position of the toe. Patients most often report pain at the dorsal proximal interphalangeal (PIP) joint from an impingement of the toe on the shoe. A callus or erythema is present over the dorsal PIP joint where it abuts the shoe. Patients also may report pain at the tip of the toe from pressure against the point of the distal phalanx.[21]

Patients can have a callus at the tip of the toe and a malformed nail, especially patients with diabetes and neuropathies (see the image below). When pain beneath the callus exceeds the neuropathic threshold in a patient with diabetes, an abscess may be present beneath the callus, which is discovered only when the callus is debrided. The other source of pain is the metatarsophalangeal (MTP) joint, which develops synovitis because of irritation from its extended position and instability.

Another less often seen presentation is impingement of the lateral claw toe on the adjacent toe, causing a callus or soft corn on the medial border of the claw toe. This is usually secondary to clawing of the fourth or fifth toe. Finally, the relative increased pressure beneath the metatarsal head from the inability of the toe to share in weightbearing can result in metatarsalgia. This occurs secondary to distal migration of the plantar fat pad with hyperextension of the MTP joint.

Assessing claw toe primarily consists of a physical examination, with additional tests as required. With the patient sitting, each of the three joints (MTP, PIP, and distal interphalangeal [DIP]) is tested for flexibility in the sagittal plane and stability in the frontal and sagittal planes. Vascularity of the toe is assessed clinically, and the presence of calluses or erythema is duly noted.

Normal sensation can be determined by the patient's ability to feel a 0.5-g force with a monofilament pressure device. If the patient cannot detect a 10-g force applied with a monofilament pressure device, this indicates loss of protective sensation.

Depending on the clinician's diagnostic considerations, the following laboratory tests may be appropriate:

• Fasting glucose to rule out diabetes
• Erythrocyte sedimentation rate (ESR) to determine the possibility of an underlying infection
• Rheumatoid factor (RF)

Radiographs are obtained to determine or exclude the following:

• Arthritic changes from old fractures or inflammatory arthropathies
• Increased metatarsophalangeal (MTP) joint space from synovitis
• Osteomyelitis at the tip of the toe from an abscess with a callus
• Position of the toes

Vascular pressure measurements, including ankle-brachial index (ABI) and absolute toe pressure, are helpful for the following purposes:

• To assess toe viability
• To determine whether the toe might reasonably be expected to heal following surgery

Findings from electromyography (EMG) provide information regarding the origin of the claw toe deformity and whether the patient has a neuropathy.

Indications for treatment are the presentations previously described that produce pain (see Presentation).[22]  Contraindications for operative treatment include poor vascularity to the toe (including vascular problems that could lead to ischemia and possible need for amputation following surgery, eg, diabetes, atherosclerosis) and poor skin quality. Of course, an open infected wound—for instance, on the proximal interphalangeal (PIP) joint from shoe pressure—should also be resolved prior to surgery.

An algorithm to help determine the appropriate surgical procedure and postoperative treatment is displayed in the image below.

When to perform each of the procedures on a claw toe and the extent of the surgical procedure on a single toe remain controversial. Other controversies involve the use of a bolster suture above the PIP joint in lieu of a pin, the size of the toe fixation pin, the length of time for which it must remain in place, and whether or not it must cross the metatarsophalangeal (MTP) joint.

There is a need for a prospective study that separates claw toes from hammertoes, fixed from flexible, severe from mild, and bony correction (ie, PIP and metatarsal neck osteotomies) from soft-tissue procedures alone. The addition of an extensor tendon transfer beneath the intermetatarsal ligament with reattachment to the proximal phalanx may help improve continued deformity at the time of surgery or recurrent postoperative dorsiflexion deformity.

Minimally invasive (percutaneous) approaches to treatment of lesser-toe deformities such as claw toe have been associated with high correction potential and low complication rates.[23]  Hedegaard Andersen et al evaluated outcomes of needle flexor tenotomies as a treatment option for hammertoes, mallet toes, and claw toes in 81 patients with diabetes (106 tenotomies); they found needle flexor tenotomies to be safe and effective as compared with scalpel tenotomies done by scalpel, both as treatment for ulcers and to prevent formation of new ulcers associated with these deformities.[24]  Schmitz et al described similar results.[25]

Medical treatment for claw toes depends on the underlying cause. Therefore, anti-inflammatory drugs, glucose-lowering agents, and antibiotics all may be appropriate. However, these treatments are not believed to reverse the claw toe position.

Conservative treatment

After medical treatment is initiated, consider conservative therapy,[26] including avoidance of wearing high-heeled, narrow-toed shoes, which increase dorsal ground reactive forces on the toe and crowd the toes against each other, producing impingement. Shoes with a wide toe box, soft upper shoe, and stiff sole to absorb dorsally directed forces against the plantar plate are appropriate. Some high-quality athletic shoes fulfill these criteria.

A metatarsal bar can be added to the shoe to avoid metatarsal pressure, but patients more easily accept metatarsal pads (see the first image below). Cushioning sleeves or stocking caps with silicon linings can relieve pressure points at the PIP joint and tip of the toe (see the second image below). A longitudinal pad beneath the toes can prevent point pressure at the tip of the toes.[27, 28]

Because the MTP joint is always dorsiflexed by definition, some correction of its position is necessary to restore a more neutral angle at the MTP joint. This consists of Z-lengthening of the extensor tendon, dorsal MTP capsulotomy, and collateral ligament release (see the images below). If deviation is present in the frontal or coronal plane in addition to claw toe, the loose collateral ligament side can be imbricated instead of released.[9, 14, 29, 30, 31]

At the PIP joint (if it is completely flexible), a flexor digitorum longus (FDL) transfer to extensor tendon can bring the toe into alignment. This is accomplished via the following steps:

• Making a longitudinal cut across the plantar MTP proximal skin crease (see the first image below)
• Retracting the skin with one or two small Meyerding retractors if necessary
• Splitting the tendon sheath (see the second image below)
• Isolating the FDL tendon between the flexor digitorum brevis (FDB) tendons (see the third image below)
• Passing a small curved hemostat beneath the long flexor to establish tension in the tendon
• Cutting the tendon distally through a small stab incision in the skin just proximal to its attachment (see the fourth and fifth images below)

The two distal raphes are held with two hemostats, and blunt separation is accomplished by cutting the distal connecting raphe of the FDL tendon into two parts with tenotomy scissors. (See the first and second images below.) Through the dorsal incision used to address the Z tendon lengthening, curved hemostats are directed circumferentially around the proximal phalanx. The tip of the FDL tendon raphe is grasped on the medial side and brought from the plantar wound dorsally. (See the third and fourth images below.)

A similar technique is used to grab the lateral raphe and bring it dorsally. The tendons are attached to themselves and to the repaired extensor Z-lengthened tendon with 2-0 absorbable suture (see the images below). Absorbable suture prevents the formation of a permanent knot bump on the dorsal aspect of the toe.

The tendon transfer is summarized in the video below.

If the PIP is fixed in flexion or cannot be brought back easily to a neutral position, remove the distal portion of the proximal phalanx along with the articular cartilage of the middle phalanx. If only a PIP resection is required (ie, an FDL transfer is not needed), a shorter longitudinal incision can be made dorsally over the MTP joint and proximal phalanx for the Z-lengthening, dorsal capsulotomy, and collateral ligament release surgery. A transverse incision can then be made at the PIP joint for correction of the fixed deformity. (See the images below.)

If an FDL transfer is necessary along with a PIP resection, this may be accomplished with extension of the dorsal longitudinal MTP incision over the PIP joint. Once through the skin, a continuation of the Z-lengthening of the tendon may be accomplished across the PIP joint. The distal portion of the proximal phalanx is isolated by cutting the collateral ligaments and exposing the bone. The distal portion of the proximal phalanx is cut with a small, sharp bone-cutting device (eg, a saw) just proximal to the flare of the condyles.

The articular cartilage is then removed from the proximal portion of the middle phalanx. A 0.54-mm doubly pointed Kirschner wire (K-wire) is driven into the distal cut bony surface of the middle phalanx, with care taken to keep the guide wire in the center of the bone to avoid eccentric positioning.

The K-wire is brought out of the tip of the toe while the distal interphalangeal (DIP) joint is held in neutral position. The K-wire is then grasped distally and drilled back through the proximal phalanx across the metatarsal head, with the interphalangeal (IP) joints held in neutral position with slight flexion at the MTP joints (see the images below).[32, 33]

The resected PIP joint is now inspected to avoid eccentricity and bone prominence. If this is found, the prominence is resected or the guide wire replaced. This guide wire, being somewhat larger than the previously recommended 0.54-mm K-wires, is less likely to break, does not become unstable (which would cause infection), and can be left in place for 4 weeks to increase the chance of fusion or fibrosis of the PIP joint.

If the PIP joint is not resected, stabilization of soft tissue at the MTP joint is important to promote ultimate healing in the corrected position. Therefore, a K-wire can be driven from the articular cartilage of the proximal phalanx out of the tip of the toe and back antegrade through the metatarsal head. This can also be attempted retrograde from the tip of the toe, with the toe in a slightly plantarflexed position at the MTP joint and neutral at the PIP and DIP joints. This is more difficult. However, even if the pin only engages the capsular tissue of the MTP joint, this is often enough to keep the joint relatively stable.

The pin is removed after 2 weeks, because the goal is joint stability, not arthrodesis. The joint may be taped for an additional 4 weeks if further immobilization is necessary.

Almost always, the DIP joint is flexible in a claw toe and is relieved with a flexor-to-extensor transfer. However, should a fixed DIP joint be found, especially if it is part of the problem (ie, pressure on the nail or the tip of the toe), resection of the distal portion of the proximal phalanx and the articular portion of the distal phalanx can be performed in a similar fashion to that used on the PIP joint. A pinning technique similar to that described above also may be used.

Sometimes, such chronic dorsal dislocation of the proximal phalanx is present on the metatarsal head that reduction of the proximal phalanx is not possible or, if attempted, leaves an extreme tightness across the MTP joint, resulting in vascular compromise.

In this instance, an osteotomy, from the proximal dorsal articular surface of the metatarsal head in a direction plantar proximal along a plane parallel to the sole of the foot, allows metatarsal head retraction and reduction of the tension in the neurovascular bundle. The dorsal lip of the metatarsal shaft can be removed, and the head is fixed to the remaining shaft with a screw or continuation of the lesser toe pin into the dorsal metatarsal head and then into the center portion of the shaft. This technique is preferable to metatarsal head resection, which can result in a transfer lesion to another metatarsal head.

When claw toe is due to FDL shortening caused by ischemic contracture of the muscle after posterior leg compartment syndrome, the Valtin procedure (transfer of the FDB to the FDL after FDL tenotomy) may be considered as an option. In a study of 10 such patients treated a mean of 34 months after the injury, Gonçalves et al found that all 10 regained toe flexion and had no claw toe even during ankle dorsiflexion.[34]  

Forefoot surgery is typically performed in an outpatient setting. A fresh dressing is applied the next day, and stitches are removed after 2 weeks. Arthrodesis pins are removed after 4 weeks, and the other types of pins are removed after 2 weeks. Patients may shower with pins protruding from the toes.

The most common complication is pain from recurrent deformity in the sagittal or frontal plane, resulting from inadequate correction of the deformity, failure to obtain an arthrodesis or stable fibrosis, or premature or patient-prompted pin removal.

Other complications include pain from failure of the wound to heal, infection, numbness, dysesthesias, vascular compromise with blistering or eschar formation, and loss of the toe. If pallor of the toe is still present 30 minutes after surgery, the toe is manipulated into a more dorsiflexed position with the pin in place. If the toe does not become pink within 15 minutes, the pin is removed.

When a flexor-to-extensor transfer is done with the tunnel technique instead of the tendon-splitting technique, iatrogenic fracture through the drilled tunnel sute is a possible complication. DiPaolo et al found that such fracture was more likely to occur in proximal phalanges with a bone diameter smaller than 6 mm.[35]  In their study, half of the proximal phalanges fractured with a force of 100-200 N, and the majority of the thinner bones (ie, diameter < 6 mm) fractured with a force of less than 100 N.