DEFINITION

A hammer toe deformity is defined by a flexion deformity of the proximal interphalangeal (PIP) joint, typically with associated metatarsophalangeal (MTP) joint hyperextension. The distal interphalangeal

(DIP) joint may be flexed, extended, or in a neutral position.3

 

 

ANATOMY

 

The plantar plates of the MTP and PIP joints of the toes provide insertion points for ligaments, tendons, and soft tissue septa.

 

 

At the MTP joint, the plantar plate originates from the periosteum of the shaft of the metatarsal and it inserts onto the base of the proximal phalanx. Plantar plate dysfunction has been associated with hammer toes and claw toes.7,9

 

At the PIP joint, the plantar plate also attaches in a similar way as in the MTP joint, lying immediately plantar to the joint.

 

The collateral ligaments insert to the plantar plate at both the PIP and MTP joints.

 

The final position of the toe depends on the delicate balance between the static stabilizers of the MTP and PIP joints (plantar plate, collateral ligaments) and the dynamic stabilizers (extrinsic and intrinsic tendons).

 

The extensor digitorum longus (EDL) tendon is the primary extensor of the MTP joint; it attaches to the lateral four toes. The extensor digitorum brevis (EDB) tendon is the only dorsal intrinsic muscle of the foot, and it attaches to the medial four toes.

 

 

These two tendons maintain their orientation in part due to the fibroaponeurotic extensor hood. Its proximal segment, called the extensor sling, attaches to the plantar base of the proximal phalanx. It receives contributions from the interossei muscles. Its distal segment or extensor wing receives the insertion of the lumbrical muscles.

 

 

 

FIG 1 • Lateral view of the normal anatomy of the MTP and PIP joints of the lesser toes.

 

 

Extension of the PIP and DIP joints is achieved by the coordinated action of the extrinsic extensor tendons and the intrinsic flexor muscles; with paralysis of the intrinsic muscles, the extensor muscles would extend only the MTP joints.

 

The extrinsic flexors are the flexor digitorum brevis (FDB) and flexor digitorum longus (FDL) muscles. The FDB and FDL tendons unite to the base of the middle and distal phalanx, respectively. They flex the PIP and DIP joints and are weak flexors of the MTP joint.

 

The intrinsic flexors are the interossei and lumbrical muscles. The lumbricals flex the MTP joints and extend the interphalangeal (IP) joints; they have a stronger effect over the extension of the PIP and DIP joints due to

their distal attachment compared to the interossei, which are weak extensors of the toes7 (FIG 1).

 

PATHOGENESIS

 

Any disruption of the foot's complex and delicate balance between the static stabilizers (ligaments, plantar plate) and dynamic stabilizers (intrinsic and extrinsic tendons) creates a lesser toe deformity.

 

 

With diminished intrinsic muscle flexion power, the extrinsic extensor tendons will extend the MTP joints. With MTP joint extension, the long flexor tendons flex the PIP and DIP joints, resulting in the intrinsic tendons being insufficient in flexing the MTP joint or extending the PIP or DIP joints. This imbalance creates deformity.

 

Plantar plate disruption may also compromise the balance of the toes and promote MTP joint hyperextension, thus leading to a similar chain of events to that described above9 (FIG 2).

 

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FIG 2 • Lateral view of the pathologic anatomy of a hammer toe. Notice how the MTP extension renders insufficient the lumbricals and dorsally subluxates the interosseous tendon. The PIP flexion subluxates the extensor tendon, and continued pull of the extensor digitorum will increase the PIP flexion.

 

 

The pathologic anatomy of claw toes and hammer toes has been investigated in cadaveric dissections.

 

 

In one of these studies,8 contributions of various anatomic structures to the deformity were determined:

 

For MTP joint hyperextension deformity, the skin provided about 9% of total deformity, the extensor tendons (EDL + EDB) 25%, the dorsal capsule 19%, and the collateral ligaments 47%.

 

For PIP joint flexion deformity, the skin accounted for about 20% of deformity, the FDB tendon 40%, and the plantar capsule 40%; the FDL tendon had no contribution.

 

These numbers show the relative importance of the different anatomic structures in the deformity and suggest which structures to release in surgery.

 

With clawing (hyperextension of the MTP joint), the interossei become subluxated in relation to the MTP joint and their line of pull becomes dorsally situated in relation to the joint axis and center of MTP joint rotation.

 

 

This results in an increased deformity with interossei activity: Instead of plantarflexion, they provide dorsiflexion at the MTP joint.

 

The lumbricals normally have an angle of 35 degrees with respect to the metatarsal axis. With clawing, they can subtend an angle of 90 degrees with the metatarsal axis, rendering them insufficient to flex the

MTP joint.8

 

 

Causes for lesser toe deformity are posttraumatic, inflammatory, neurologic, congenital, postsurgical, and nonspecific in nature.

 

 

Posttraumatic deformities include sequelae of leg injuries, fractures, soft tissue injuries, and compartment syndromes.

 

 

In these cases, a scarring or contracture of the deep compartment of the leg can lead to flexion deformities of the toes.

 

A compartment syndrome after a calcaneal fracture, affecting the calcaneal compartment, will compromise the quadratus plantae muscle, thereby shortening the intrinsic musculature.

 

Damage to the tibial nerve due to these same reasons may also be responsible for loss of intrinsic flexor action, resulting in an MTP joint extension deformity.

 

Inflammatory: in rheumatoid arthritis due to capsular inflammation and disruption

 

 

Plantar plate attenuation may lead to MTP joint hyperextension and nonphysiologic PIP joint flexion.

 

Neuromuscular and congenital causes may alter the foot's intrinsic and extrinsic muscle balance.

 

 

Neuromuscular causes of lesser toe deformities include cerebral palsy, Charcot-Marie-Tooth disease, Friedreich ataxia, spinal dysraphism, and polio, among others.

 

Congenital causes include idiopathic cavovarus foot, clubfoot sequelae, and arthrogryposis.7

 

 

Postsurgical causes

 

 

 

Dorsiflexion of the metatarsal head after distal metatarsal osteotomies (to relieve metatarsalgia or synovitis) Proximal metatarsal osteotomies with elevation of the distal fragment and secondary overpull of the flexor tendons5

 

 

Secondary to metatarsal lengthening due to undesired lengthening of the flexor and extensor tendons Nonspecific causes

 

Muscular imbalance, ineffectiveness of the intrinsic flexors, and age-related deficiencies of plantar structures7

 

Shoe wear has been implicated because of the buckling effect of the toes inside a short toe box, with resulting flexion of the PIP joint.

 

NATURAL HISTORY

 

The natural history of this deformity is a slow progression to a claw toe, where extension of the MTP joint increases with an increase in PIP flexion.

 

If the deformity is flexible, the prognosis is good, as a conservative option may be successful, or if surgery is deemed necessary, simple techniques typically meet with satisfactory outcomes.

 

As the lesser toe deformity becomes fixed, the chance of a successful nonsurgical treatment decreases, and surgical treatment generally involves more complex reconstructive procedures with an increased risk for postoperative stiffness.

 

 

 

PATIENT HISTORY AND PHYSICAL FINDINGS

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The chief complaint is pain and tenderness on the dorsal PIP joint, typically due to pressure from the shoe.

 

A progressive hammer toe deformity may lead to an extended MTP joint and eventually a plantar callus under the corresponding metatarsal head. Occasionally, with associated PIP and DIP flexion, a plantar callus at the tip of the toe will develop.

 

Toe position must be evaluated with weight bearing to appreciate the full extent of the deformity. With the patient seated, the range of motion of the ankle and subtalar, transverse tarsal, and MTP joints is inspected.

 

Flexibility of the MTP, PIP, and DIP joints must be determined as it influences surgical decision making.

 

Inspection and palpation of the plantar foot may reveal calluses under the metatarsal heads and tips of the toes.

 

A comprehensive neurovascular examination is performed. Correction of lesser toe deformities will place digital vessels and nerves on stretch; preoperative neurovascular compromise to the toes must be identified, particularly if surgical correction is considered.

 

Examinations of the lesser toes' MTP and IP joints may include the following:

 

 

Push-up test (MTP): If the deformity is flexible, with the push-up test, the MTP joint will flex to its normal position. If not, it will remain extended, defining a fixed deformity. Semiflexible deformities are those that correct partially with the push-up test.

 

Evaluation of PIP joint stiffness: Fixed deformities are present if it is not possible to obtain full extension of the PIP joint. Flexible deformities allow the PIP joint to extend fully.

 

Evaluation of MTP joint stability: Stage 0, no laxity to dorsal translation; stage 1, the base of the proximal phalanx can be subluxated with the dorsal stress; stage 2, the proximal phalangeal base can be dislocated

and relocated; stage 3, the base of the proximal phalanx is fixed in a dislocated position.13 A new

classification for lesser toe MTP joint stability has been presented by Nery et al9 where besides the drawer test clinical signs such as alignment, flexibility, pain, and loss of toe purchase have been included.

 

IMAGING AND OTHER DIAGNOSTIC STUDIES

 

Plain radiographs

 

 

Inflammatory arthritis may be associated with periarticular erosions, and this may influence surgical management.

 

The extent of the deformity is characterized on plain radiographs: subluxation, dislocation, or medial or lateral deviation. Dislocation of the MTP joint is characterized by an overlap of the base of the proximal phalanx on the head of the metatarsal on the anteroposterior (AP) view and complete dorsal displacement of the proximal phalanx relative to the metatarsal head on the lateral view (FIG 3).

 

Magnetic resonance imaging (MRI)

 

 

MRI evaluation of the extent of plantar plate damage has been reported to be reliable after adequate

training.10 Although not needed as a rule, MRI evaluation of plantar plate disruption can guide our efforts when deciding treatment alternatives of MTP instability.

 

 

 

 

FIG 3 • AP view of a foot with hammer toe deformity with MTP joint subluxation. Notice the overlap between the base of the proximal phalanx and the metatarsal head.

 

DIFFERENTIAL DIAGNOSIS

 

Fixed hammer toe or claw toe deformities (not amenable to treatment with tendon transfer alone) MTP synovitis (absence of deformity warranting tendon transfer)

Posttraumatic toe deformities Soft tissue tumors of the toes

 

 

NONOPERATIVE MANAGEMENT

 

For flexible deformities, an initial conservative approach is recommended.

 

Stretching exercises may help but have little proven benefit, as they do not alter the imbalance of extrinsic and intrinsic tendons.

 

Shoe wear modifications: wider, deeper toe box to give more room to the toes

 

Metatarsal pads to relieve metatarsal head pressure and toe sleeves to cushion pressure on the dorsum of the PIP joints. Orthotics with metatarsal padding must be used judiciously because they elevate the toes and may lead to greater dorsal PIP joint pressure.

 

Hammer toe sling orthoses (or taping) are available that hold the proximal phalanx in a more physiologic position (FIG 4).

 

The value of these measures depends to some degree on the degree of flexibility remaining in the deformity.

 

 

 

 

FIG 4 • Hammer toe orthosis designed to hold the proximal phalanx in a plantarflexed position.

 

 

 

SURGICAL MANAGEMENT

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A toe flexor to extensor tendon transfer is rarely performed in isolation; typically, it is an adjunct to a more comprehensive correction of hammer toe and claw toe deformities.

 

The goal of a flexor to extensor tendon transfer is to reposition the proximal phalanx into a more physiologic alignment, with realignment of the MTP and PIP joints. It is essentially “taping of the toe under the skin.” Despite flexible deformity, tendon transfer may need to be performed with dorsal capsulotomy and collateral ligament release of the MTP joint. As the deformity becomes more fixed, a PIP arthroplasty-arthrodesis with or without metatarsal shortening osteotomy would typically be warranted, but a flexor to extensor tendon transfer may need to be added to avoid residual elevation of the toe (“floating toe”), one that does not touch the floor with weight bearing.

 

Preoperative Planning

 

For MTP joint hyperextension deformity, a bone-shortening procedure can be performed. This procedure is commonly performed if associated metatarsalgia is present.12

 

Generally, a soft tissue procedure is chosen; the choice will vary depending on the amount of release needed.

 

Progressive releases have to be made, starting with the dorsal skin, followed by extensor tendons (tenotomy or lengthening), the dorsal capsule, and collateral ligaments, until an aligned MTP joint is obtained.

 

For further correction and stabilization, a flexor to extensor transfer should be added. In this case, the transfer should be done suturing the FDL to the EDL proximal to the middle of the proximal phalanx to obtain more flexion power over the MTP joint.

 

For PIP joint flexion deformities, FDB releases are considered if the flexion contracture is not solved percutaneously.

 

 

If FDB tenotomy is not enough to treat the PIP deformity, a PIP joint arthroplasty or arthrodesis should be added.

 

A bone-shortening procedure can be also considered, typically a metatarsal-shortening osteotomy. In our opinion, a resection of the proximal aspect of the proximal phalanx should be avoided due to a high prevalence of postoperative MTP joint instability.

 

The flexor to extensor transfer will correct the PIP joint flexion if flexible and will also stabilize the deformity if a FDB tenotomy or a PIP joint arthroplasty was performed. In this case, the transfer should be done suturing the FDL to the EDL distal to the middle of the proximal phalanx to obtain more extension power over the PIP joint.

 

 

 

FIG 5 • Positioning of the patient with adequate room for the surgeon to comfortably approach the toe distally.

 

Positioning

 

A supine position is preferred, with the involved foot on the same side as the surgeon.

 

When performing the flexor to extensor transfer, as a plantar approach is needed, enough distance between the foot and the distal end of the table has to be available so that the surgeon can work comfortably (FIG 5).

 

Approach

 

For the MTP approach, a longitudinal dorsal incision over the involved MTP joint is performed.

 

 

The incision can be performed in a curvilinear fashion to avoid skin contractures (in our experience, a rare complication).

 

For the PIP joint approach, a dorsal transverse approach over the PIP joint is performed, removing the hyperkeratotic skin with the incision.

 

 

It is also possible to perform a longitudinal incision after the tendon transfer incision, which may include the MTP incision when an additional procedure has been performed over the MTP joint.

 

For the flexor to extensor transfer, a dorsal approach over the proximal phalanx must be made.

 

 

In our experience, an extension deformity at the MTP joint is virtually always present, and therefore a procedure over the MTP joint is commonly performed. This MTP approach can be used, extending it distally.

 

To gain access to the flexor tendons, two plantar incisions have to be made, one transverse along the proximal skin crease of the toe and the second oblique over the DIP joint.

 

This last incision can be made transverse, and a percutaneous FDL tenotomy can be performed.

 

There is a risk of damaging the plantar plate of the DIP joint and hyperextension of the joint can be observed.

 

 

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TECHNIQUES

• Flexor to Extensor Tendon Transfer

Exposure

Make a plantar incision in a short transverse fashion along the proximal skin crease of the involved toe.

Carry the dissection through the subcutaneous layer. Identify the flexor tendon sheath and open it longitudinally with a blade (TECH FIG 1).

This incision can also be made longitudinally, as shown by Boyer and DeOrio,2 which helps to avoid damage to the neurovascular structures.

Preparing the Flexor Digitorum Longus

Identify the FDL tendon between the slips of the FDB (TECH FIG 2A) and retract it with a hemostat to the surface of the wound, placing it into traction (TECH FIG 2B). Keep the dissection central to avoid excursion to the adjacent medial and lateral digital neurovascular bundles.

Place a second plantar incision oblique in orientation over the DIP, just proximal to the fat pad, and identify the plantar capsule of the joint to protect it.

Detach the FDL from its insertion to the distal phalanx. As noted before, this incision can be made transversely and the FDL can be detached percutaneously (TECH FIG 2C).

Keep the stab incision central to avoid damage to the digital neurovascular bundles. Although the incision is at the distal crease, direct the scalpel proximally at a 45-degree angle to ensure that the FDL tendon is transected and the DIP plantar plate is avoided.

Pull the FDL tendon from the proximal incision and separate it into two slips along its midline raphe. Hold each half with a hemostat (TECH FIG 2D).

 

 

 

TECH FIG 2 • A. The FDB appears dividing itself in two slips, and the FDL rests in between. The FDL possesses a midline raphe, which helps to identify it. B. The FDL is identified with a small hemostat, and traction is being placed on it. C. Detachment of the FDL through a transverse distal incision in a percutaneous way. D. Splitting of the FDL in two following the middle raphe.

 

 

 

TECH FIG 1 • Plantar view of the proximal plantar incision: flexor tendon sheath identification.

 

Preparing the Extensor Tendon

 

Place a dorsal longitudinal incision over the dorsum of the proximal phalanx just distal to its midpoint to the proximal metaphyseal flare.

 

Perform superficial dissection, and identify the extensor tendon and split it in line with the long axis of the phalanx (TECH FIG 3). Carry the dissection in a subperiosteal manner deep to the neurovascular bundle.

Performing the Transfer

 

Pass a small hemostat from the dorsal aspect of the toe through the extensor tendon, between the bone and the periosteum, to the plantar aspect of the toe. Identify the tip of the hemostat in the plantar incision. Take care to avoid pinching the bundle. The tip of the hemostat must be passed through the slips of the FDB tendon (TECH FIG 4).

 

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TECH FIG 3 • Dorsal incision over the proximal phalanx, identifying the extensor tendon and splitting it following the longitudinal axis.

 

 

First, pull half of the FDL tendon from the plantar aspect of the toe to the dorsal aspect, keeping their relative position—in other words, the lateral one is pulled to the lateral dorsal aspect of the phalanx and vice versa.

 

Then, with the ankle held in a neutral position, the MTP joint in 20 degrees of plantarflexion, and the PIP joint in neutral, secure both slips of the FDL over the extensor tendon with two or three separate stitches of 4-0 absorbable suture.

 

Evaluate the MTP joint at this time to observe for continued extension at that joint. If any is present, alternative procedures will need to be performed.

 

 

 

TECH FIG 4 • Plantar picture of the toe showing the place (marked with an asterisk) where a small hemostat should pass through from dorsal to plantar, deep to the neurovascular bundle, in between the slips of the FDB tendon to hold one of the divided halves of the detached FDL tendon.

 

 

 

Close the wound with absorbable stitches on the plantar incisions and nylon dorsally. Before breaking sterility, deflate the tourniquet to ensure revascularization of the toe.

• Flexor to Extensor Tendon Transfer through a Drill Hole

   

  The technique is as described earlier up to the step where the FDL is brought through the plantar aspect of the toe.

   

  Make a dorsal longitudinal incision over the proximal phalanx from just proximal to its midpoint to the distal metaphyseal flare.

   

  Take the dissection down to the extensor sheath and split the sheath and periosteum in line with the incision, exposing the dorsum of the phalanx.

   

  Place a drill hole dorsal to plantar large enough to allow passage of the tendon, in the junction of the

  middle and distal third of the proximal phalanx.

  Generally, we use a 2.0-mm drill and take care to avoid making a hole larger than one-third of the diameter of the bone.

  Pass the tendon between the short flexors and through the hole. Position the foot as described earlier and suture the tendon with 4-0 absorbable sutures to the extensor sheath.

  The rest of the procedure remains the same as described earlier.

   

   

   

  PEARLS AND PITFALLS

   

  Indications ▪ Evaluate the stiffness of the deformity preoperatively. It is important to inform the patient about the possible additional procedures needed and the corresponding outcome. The surgery for hammer toes is a step-by-step procedure: Additional surgery is commonly needed as the alignment is being corrected. Soft tissue procedures will be followed if needed by bone-shortening procedures and tendon transfers, depending on the alignment we obtain.

   

  Preoperative planning

• Always correct the deformity going proximal to distal. Deciding to add a bone procedure is not always easy; it depends on how stiff the deformity is. A Weil osteotomy will most probably correct the extension component of the MTP joint and some of the flexion component at the PIP joint. The problem is the resulting soft tissue balance, where an MTP joint that is too unstable may lead to a floating toe. Therefore, if there is not metatarsalgia, we prefer to do soft tissue procedures before adding a bone shortening.

   

  PIP

  resection arthroplasty or arthrodesis

  • This is a common adjunct in hammer toe surgery. Failure to resect enough of the head of the proximal phalanx can lead to postoperative pain or recurrence of the deformity. Failure to perform the tenodesis and dermodesis adequately to stabilize the joint may also result in a recurrence.

     

    Flexor to extensor transfer

    • When performing the transfer, hold down the toe to 20 degrees of plantarflexion at the MTP joint and the ankle at 90 degrees. Adequate traction on the tips of the tendon will suffice to hold down the toe. Sometimes, half of the tendon can be stripped off before performing the transfer. In this case, it is possible to perform the transfer through a drill hole to achieve an adequate balance with just one slip of the tendon. If the tissues are of bad quality, then a Kirschner wire may be used to fix the joint and protect the repair.

 

 

 

POSTOPERATIVE CARE

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Individual soft compressive dressings are placed over each operated toe; sterile strips of adhesive bandage are commonly used to keep each toe aligned.

 

Small “tie-down” straps are used to hold each toe in plantarflexion (the straps are placed around the proximal phalanx of each toe). These are kept in place for 6 weeks.

 

A soft compressive dressing is placed over the foot, and the foot is placed in a postoperative shoe with a rigid rockerbottom sole.

 

Immediate weight bearing as tolerated is allowed, with a plantigrade foot, keeping the MTP joints neutral inside the postoperative shoe.

 

From weeks 2 to 4, once soft tissues allow mobilization and the stitches are removed, passive plantar flexion exercises at the level of the MTP joint are done to stretch the dorsal structures.

 

From the sixth week on, depending on comfort and edema, a return to normal shoes is permitted.

 

 

OUTCOMES

The first reports of this technique used both the FDL and FDB tendons in the transfer.

 

Parrish11 in 1973 described the technique shown in this chapter, using only the FDL and splitting the tendon longitudinally and suturing each half to each other under the extensor tendon. Fifteen of 18 patients had good to excellent results (83%).

Barbari and Brevig1 reported 89% patient satisfaction in 39 cases.

Cyphers and Feiwell4 reported 95% good to excellent results in 20 patients with residual paralysis from myelomeningocele.

Boyer and DeOrio2 recently reported an 89% satisfaction rate, using the technique in fixed and flexible hammer toes. They reported better results for fixed deformities where a concomitant resection of the head of the proximal phalanx was performed.

Our experience with this technique over the past 6 years has yielded a good to excellent result in 83% of the 40 cases (unpublished data).

Most postoperative complaints are due to stiffness of the PIP joint and in relation to the MTP joint when a procedure was added at this level (osteotomy, tenotomy, or capsulotomy).

Recurrence of deformity has been noted in 9% of the cases.

Retrospective evaluation of our results has shown that incomplete evaluation of the preoperative stiffness at the MTP joint may explain most of the recurrences.

 

COMPLICATIONS

Swelling and numbness

 

These complications usually subside with time.3

Loss of vascularity can occur due to traction on the neurovascular bundle or compression due to the transfer.

Waiting, using a warm gauze, modifying, or removing the Kirschner wire if used, and redissecting to ensure that the neurovascular bundle is not compressed are useful measures to solve this problem.

A small amount of lidocaine around the bundle can assist in smooth muscle relaxation. Nitropaste can be applied to the toe too.

 

 

PIP stiffness

 

This has been reported in up to 60% of cases6 (excluding joint arthrodesis or arthroplasties). It is one of the main reasons for dissatisfaction, specifically in flexible hammer toe deformity correction.4

In earlier studies, no mention was made of preoperative stiffness, so it is difficult to quantify the relative contribution of previous stiffness (in fixed hammer toes) versus stiffness due to the transfer itself.

Hyperextension deformities

Hyperextension deformities at the DIP joint are the infrequent result of excessive dissection in the volar aspect of the DIP joint when harvesting the FDL tendon.

They can be avoided with careful dissection.

These deformities at the MTP joint are due to inadequate positioning of the transfer (too distal over the proximal phalanx) or preoperative stiffness not adequately evaluated, which may need, besides additional MTP joint releases, bone-shortening procedures.

Recurrence of the deformity

This has been reported in up to 20% of cases.

Recurrence is due to inadequate tension of the transfer, preoperative stiffness not adequately evaluated requiring additional soft tissue releases or bone-shortening procedures, underlying neurologic causes, excessive dorsal soft tissue scarring, or failure of the transfer.

 

REFERENCES

1. Barbari SG, Brevig K. Correction of clawtoes by the Girdlestone-Taylor flexor-extensor transfer procedure. Foot Ankle 1984;5:67-73.

    

    

2. Boyer ML, DeOrio JK. Transfer of the flexor digitorum longus for the correction of lesser-toes deformities. Foot Ankle 2007;28:422-430.

    

    

3. Coughlin M. Lesser toes abnormalities. J Bone Joint Surg Am 2002;84A: 1446-1469.

    

    

4. Cyphers SM, Feiwell E. Review of the Girdlestone-Taylor procedure for clawtoes in myelodysplasia. Foot Ankle 1988;8:229-233.

    

    

5. Hurwitz S. Hammertoe deformity following forefoot surgery. Foot Ankle Clin 1998;3:269-277.

    

    

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6. Kirchner J, Wagner E. Girdlestone-Taylor flexor-extensor tendon transfer. Tech Foot Ankle Surg 2004;3:91-99.

    

    

7. Marks R. Anatomy and pathophysiology of lesser toes deformities. Foot Ankle Clin 1998;3:199-213.

    

    

8. Myerson M, Shereff M. The pathological anatomy of claw and hammer toes. J Bone Joint Surg Am

   1989;71(1):45-49.

    

    

9. Nery C, Coughlin M, Baumfeld D, et al. Lesser metatarsophalangeal joint instability: prospective evaluation and repair of plantar plate and capsular insufficiency. Foot Ankle Int 2012;33(4):301-311.

    

    

10. Nery C, Coughlin M, Baumfeld D, et al. MRI evaluation of the MTP plantar plates compared with arthroscopic findings: a prospective study. Foot Ankle Int 2013;34(3):315-322.

     

     

11. Parrish TF. Dynamic correction of clawtoes. Orthop Clin North Am 1973;4:97-102.

     

     

12. Schuh R, Trnka HJ. Metatarsalgia: distal metatarsal osteotomies. Foot Ankle Clin 2011;16:583-595.

     

     

13. Thompson FM, Hamilton WG. Problem of the second metatarsophalangeal joint. Orthopedics 1987;10:83-89.