Lesser toe deformities include, but are not limited to, hammertoes, mallet toes, and claw toes. These deformities are typically characterized by any combination of a plantarflexion deformity of the proximal interphalangeal (PIP) or distal interphalangeal (DIP) joints, and are commonly seen in adults with diabetes.¹ The pathophysiology appears to be multifactorial with a tendency to affect the second toe or less commonly the third toe.^2,3 The projection of the affected toe distal to the other digits can exert excess pressure and friction on either the toe pad and/or the DIP joints of the toe, especially in a shoe that has a narrow or short toe box. Over time, corns or callosities may form at these pressure points, and frequently in insensate patients with diabetes, subsequent ulceration.

Chronic nonhealing toe ulcerations often result in toe amputations. Postamputation foot dynamics are further altered and new pressure points lead to more ulceration and the possibility of subsequent foot or leg amputation. Typical conservative treatment methods, such as extra-depth toe-box shoes, pads, inserts, and splints must be continually employed and in the authors’ experience in patients with diabetes, provide mixed results and recurrent ulcerations on these pressure points. Device expense, shoe wear compliance issues, and incorrectly applied techniques pose ongoing difficulties. Open flexor tenotomy has traditionally been the definitive corrective procedure used by many surgical sub-specialists for severe lesser toe deformities that are often complicated by ulceration when conservative treatment has failed.⁴ This procedure not only corrects toe deformities, obviating the need for extra-depth shoes and orthotic devices, but also allows for rapid healing of the toe ulcerations after pressure has been relieved. Overall, the “percutaneous” procedure is simple, the outcomes are excellent, and the complications are minimal. The authors routinely perform closed or “percutaneous” flexor tenotomies in insensate patients with diabetes and the procedure—never described in an instructive fashion in the literature—can be performed during a routine office visit.

Procedure

Preoperative preparation with local anesthesia via digital block or local toe injection can be used but anesthesia is usually not necessary in the insensate diabetic foot. The procedure is comprised of several steps. The first step is to make a target incision between the plantar creases of the metatarsophalangeal (MTP) and PIP joints at the paramedial aspect of the toe (Figure 1). Position a 15-scalpel blade perpendicular to the skin with the blade cutting edge facing toward the toe tip. The stab incision is carried down to bone. Once bone resistance is met, the blade tip should be slid beneath the flexor digitorum longus and brevis tendons and above the plantar surface of the bone (Figure 2). In this position, the scalpel blade is turned counterclockwise so that the cutting edge will face away from the bone (Figure 3). This maneuver creates space between the tendon and bone and simultaneously severs the tendons. The cutting is accomplished in 1 motion with a perceptible rupture or “pop” of the tendons. The toe is then stretched to a neutral position. At times after tenotomy, a persistently rigid deformed toe requires capsulolysis that is accomplished by sustained, firm stretching of the toe in order to release the fibrotic joint capsules and straighten the toe. After completion of the procedure, the small stab wound heals secondarily and does not require primary closure (Figure 4). The patient can mobilize with immediate weight bearing. After correction of the flexion deformity the toe pad is now properly offloaded without orthotic devices and rapid healing of the pressure ulceration follows (Figures 5 and 6).

Discussion

Various types of lesser toe deformities exist. Hammertoes are characterized by a plantarflexion deformity of the PIP joints, a condition commonly seen in women with diabetes and peripheral neuropathy. Mallet toes are similar, but the deformity involves the DIP joint rather than the PIP joint. Claw toes are typically a combination of deformities involving all the joints of the toe, hyperextension of the MTP joint, and plantarflexion at both the PIP and DIP joints.¹ This type of deformity is commonly seen in Charcot-Marie-Tooth disease.
The pathophysiology of these toe deformities is believed to be multifactorial.³ Associated disease etiologies include diabetes, inflammatory arthritis (rheumatoid, lupus, gouty, psoriatic), congenital deformity, neuromuscular abnormalities (polio, Charcot-Marie-Tooth disease, muscular dystrophy, cerebral palsy, diastematomyelia), diseases of the lumbar spine, hallux valgus, trauma, small toe box shoe pressure, and instability of the MTP joint.³ The deformities tend to favor the second toe, which is frequently the longest and therefore most traumatized of the lesser toes.^2,4 Consequently, tight or ill-fitted shoes can cause and aggravate ulcerations.⁵ In mallet toes the projection of the second toe distal to the other toes can cause pressure at the tip of the toe and buckling at the DIP joint in a shoe that has a narrow or short toe-box. This flexion posture over time can attenuate the terminal extensor tendon until it can no longer extend the distal joint. Moreover, the flexor digitorum longus, in the absence of a strong antagonist, holds the DIP joint in flexion until the deformity becomes rigid. This chronic fixation can similarly lead to the creation of hammertoes and claw toes. Even in feet with normal sensation the most frequent complication of a lesser toe deformity is a painful end corn just beneath the nail or at the crown of a protruding interphalangeal joint. The corn results from chronic pressure at the tip of the toe or at the head of the protruding joint, which is habitually flexed into the sole of the shoe, leading to ulceration in neuropathic feet. Treatment directed toward the wound alone may be counterproductive while the ultimate goal must be correction of the underlying etiology caused by the toe deformity.
Flexor tenotomy can be performed with a closed percutaneous or the customary open technique. The open technique employs a transverse incision on the plantar toe surface at the proximal phalanx, hooking of the flexor digitorum longus and brevis tendons from the surrounding neurovascular bundle, and subsequent division with tendon release. This technique is more widely used because of its ability to properly define the flexor digitorum longus and brevis tendons as well as the neurovascular bundle.⁶ It also avoids any interruption of innervation to the distal toe and is best indicated in the painful lesser toe deformities of sensate feet, such as seen in congenital curly toe deformities.^6,7 However, the percutaneous or closed technique is an exceptional modality for ulcerated insensate diabetic lesser toe deformities where nerve bundles have already been compromised^.1,8 Offloading is the ultimate goal for healing ulcers.
The main contraindication to this procedure is small vessel vascular compromise in the setting of peripheral vascular disease. Any further vascular injury can lead to rapid anoxia and toe gangrene. Complications of the procedure may include wound infection at the stab site, prolonged toe swelling, and vascular compromise from accidental resection of digital neurovascular bundles.⁹ Residual toe deformity is possible, such as hyperextension deformity of the DIP joint, and flexion deformity of the PIP joint. A failed procedure might also result in associated hyperextensive joint defects at the MTP joint. Residual deformities might require orthopedic open intervention. Failure to completely divide the flexor tendon will prevent straightening of the toe. However, in the authors’ many years of experience none of the above complications have occurred.

Conclusion

Percutaneous flexor tenotomy provides an effective therapy for correcting the majority of lesser toe deformities, especially if complicated by a toe ulcer in an insensate diabetic foot. In most clinics extra depth shoes, toe pads, inserts and splints, in addition to standard wound care, have been the first line of treatment for ulcerations associated with toe deformities. Offloading with relief of pressure points remains the sine qua non in ulcer healing. Percutaneous flexor tenotomy relieves pressure points on the toe, allowing for rapid healing of ulcerations and prevention of future callus formation and repeat ulceration. The need for toe amputation because of nonhealing ulcerations (that are often infected) is eliminated and the foot remains intact. This technique has become the standard toe sparing procedure in the treatment of ulcerations in diabetic lesser toe deformities in the authors’ practice.