Intractable Plantar Keratosis Treatment & Management

A detailed history, meticulous clinical assessment, and radiographic evaluation should be used to assess the causes and extent of intractable plantar keratosis (IPK). Lesions recalcitrant to nonoperative care and routine debridement can be considered for surgery.

Indications for surgical treatment of IPK include the following:

• Failure of periodic debridement, offloading, and accommodative shoes
• Continued pain and loss of function that a patient cannot tolerate
• Patient acceptance of the risks and benefits of surgery

Absolute contraindications for surgical correction of an IPK include the following:

• Local infection
• Vascular insufficiency
• Painless lesion
• Neuropathy

Relative contraindications include the following:

• Diabetes
• Avascular necrosis (AVN) of the metatarsal head
• Hypermobile first ray

The future of IPK treatment must focus on more accurate identification of the underlying pathology of IPK. The enhancement of nonsurgical means of treatment and the refinement of surgical options also are critical. Computerized force plates can aid in understanding the pressure distribution on the foot and thus create better offloading orthotics.

The high rate of transfer metatarsalgia and recurrence of IPK suggests that surgical intervention should be undertaken with caution. Surgery is more successful when a specific etiology can be determined. Performing prophylactic surgery on an asymptomatic foot because of irregularities seen on radiography is highly controversial and is not recommended.

In a study by Zhao et al, pelvis adjustment combined with Dong's extraordinary points helped abate 21 cases of refractory calcaneal pain, and it may have the potential to help treat IPK. ^[31]

First-line medical treatment of IPK includes the following:

• Padding - A doughnut-type cutout pad can be placed directly over the lesion; this allows the IPK to sit in the center and be offloaded by the surrounding pad
• Shoe modifications - A low-heel shoe reduces the amount of weight shifted toward the forefoot and can be more forgiving on the foot; a shoe with a wide, soft toe box that does not crowd the toes is also recommended
• Oral nonsteroidal anti-inflammatory drugs (NSAIDs) - These are occasionally used but typically are not very effective
• Injectable therapies - Steroid injection into or around an IPK is not recommended, on the grounds that it can create fat-pad atrophy and further exacerbate the plantar foot pain; other injectable modalities have been tried, but results to date have not been promising ^[32]
• Orthotic devices - These are typically accommodative or offloading and are soft so as to help cushion the area; if the IPK is secondary to a hypermobile first ray, a rigid Morton extension may be used to help focus more of the weightbearing force onto the medial column of the foot
• Moisturizing lotions or creams - These can be effective in softening the keratosis and reducing pain; some prescription creams include mild lactic acid to help remove callus tissue
• Pumice stones and callus removers - These should be used with caution in certain patients; they are typically used in the shower or bath, when the skin is soft; reducing the overall mass of the lesion usually provides some symptomatic relief
• Foot baths
• Scrub brushes
• Paraffin baths to reduce callus buildup
• Botulinum toxin - This may be a treatment for IPK ^[33]

More effective and invasive treatments include debridement. In a study by Jain et al, platelet-rich plasma injections were more effective than corticosteroid injections for the treatment of plantar fasciitis; such injections might work for IPK. ^[34]

Surgical options

Surgical treatment of IPK can involve the following:

• Paring of callus tissue and removal of the central core of the lesion
• Sesamoid planing, with protection of the flexor attachments - This is done in lesions below the first metatarsal
• Complete tibial or fibular first-ray sesamoidectomy - This is avoided if possible, but it may be necessary in cases of an enlarged sesamoid, sesamoid arthrosis, or nonunion of fracture; care should be taken to reestablish soft-tissue balance of the first metatarsophalangeal (MTP) joint so as to prevent a varus or valgus plane deformity
• Distal metatarsal osteotomies - Variations include minimal incision or percutaneous transverse osteotomy of the metatarsal neck, chevron osteotomy, oblique sliding osteotomy, dorsal closing wedge, partial or total resection of the metatarsal head, intramedullary decompression, and lesser-rays condylectomy at osteotomy ^[8] ; in the past, most of these osteotomies were not fixated, but the current norm is to use internal fixation, employing either screws or wires, with possible percutaneous wiring as well ^{[35, 36]}
• Proximal metatarsal segmental resection - This involves removal of the proximal metatarsal bones to shorten the overall length of the metatarsal and translate the head more proximally

Data have been published on the clinical outcomes of isolated periarticular osteotomies involving the first metatarsal to treat hallux rigidus. ^[37]

Preparation for surgery

Patients should be appropriately counseled on the risks and benefits of surgery and the expected postoperative course. Operative risks include infection, neurovascular damage, nonunion, wound dehiscence, toe destabilization, recurrence of lesion, and development of a transfer lesion. The patient should be made aware of the likelihood of recurrence or transfer lesion development. The patient must have appropriate expectations. An informed surgical consent is obtained.

The clinician must determine the cause of the IPK because this dictates the surgical correction. Associated pathologies, such as hammertoe contracture, should be addressed at the same sitting if they are causative to the painful IPK.

Operative details

There are various surgical approaches to the correction of an IPK. The authors' preferred technique includes either a plantar condylectomy of the metatarsal head or a double-cut metatarsal oblique osteotomy at the head and neck of the metatarsal. Either approach is well suited to monitored anesthesia care (MAC) with a regional popliteal or ankle block. An ankle Esmarch or tourniquet can be used, provided that this does not cause contracture of the long toe flexors.

A dorsally based linear incision is marked just medial or lateral to the extensor tendon over the involved MTP joint. Sharp dissection through the skin and fascia tissue is performed, with care taken to protect any cutaneous nerves. The incision is deepened, and the extensor complex is elevated and protected either medially or laterally. The capsular tissue is sharply incised, and minimal release of the collaterals is performed to enhance exposure. The involved toe is plantarflexed to expose the metatarsal head.

If a plantar condylectomy is to be performed, the plantar capsular attachments must be released with a curved dissector. Care should be taken to protect the long flexor tendons beneath the metatarsal head. The plantar condyles are identified, and one is typically larger than the other. A microsagittal saw is used to remove the condyles in a thin plantar osteotomy made parallel to the weightbearing surface (plantar one-third of the metatarsal head).

The small sliver of bone, including the condyles, is then removed. A hand rasp can be used to smooth any rough edges. A percutaneous Kirschner wire (K-wire) is driven through the length of the toe and across the involved MTP joint down the metatarsal. This is important for allowing the plantar capsule to adhere to the cut bone surface and preventing MTP destabilization.

If the involved metatarsal is plantarflexed or elongated, a double-cut Weil osteotomy is instead performed. The microsagittal saw is used to make a 30° osteotomy at the superior aspect of the metatarsal head-neck junction angled from distal-dorsal to proximal-plantar. Two blades are stacked together to create a controlled wedge resection. The width of each blade cut is approximately 1 mm; thus, two blades together create a 2-mm wedge. This allows some dorsal displacement of the metatarsal head in a controlled fashion.

The metatarsal head is also translated slightly proximal along the osteotomy to shift the head away from the pressure area, and it is fixated with a small screw. An aggressive proximal shift must not be made, because this can shift the head in a plantar direction as it follows the angle of the osteotomy. Again, a percutaneous K-wire is used to splint the toe and maintain alignment of the MTP joint.

The extensor tendon sling and capsular tissue are repaired with 2-0 absorbable suture. Subcutaneous closure is performed with 2-0 absorbable suture, and the skin is closed with 4-0 nonabsorbable suture of choice. The IPK is then debrided from the plantar forefoot, and the central core should be completely removed.

A compressive dressing is applied, and the tourniquet is released. Before leaving the operating room, the physician should confirm that the toe's vascularity is intact.

The patient is placed in a rigid postoperative shoe and allowed to bear weight as tolerated. The dressing is kept clean and dry and is changed in 7-10 days. At that point, the sutures are removed if adequate healing has taken place. Postoperative radiography is performed to confirm alignment of the toe and/or osteotomy.

The patient must remain in the postoperative shoe until the K-wire is removed and adequate healing of the osteotomy is observed. Typically, the K-wire is left in place for 4 weeks and then removed in the office.

At 6 weeks postoperatively, follow-up radiography is performed to assess the healing of the osteotomy. The osteotomy typically requires 6-8 weeks to heal enough to allow migration out of the surgical shoe and into a comfort shoe. Once the patient is in a comfort shoe, postoperative exercises of the toe are encouraged so as to restore the toe's strength and prevent loss of purchase, or floating, of the toe.

Typically, patients are able to return to all activities without restriction by 12 weeks.

Postoperative complications of surgical therapy for IPK include the following:

• Edema
• Recurrence of IPK
• Pain
• Numbness
• Stiffness of the involved MTP joint
• Shortening of digits or metatarsals
• Malposition
• Nonunion
• Delayed union
• Transfer lesions
• Vascular complications
• Reflex sympathetic dystrophy

Appropriate shoe wear is important in preventing recurrence of the IPK. The patient should again be counseled on wearing shoes with enough room in the toe box and a reasonable heel height. Custom orthotics may be beneficial in supporting the foot, and specific modifications can be made to off-load the surgical area.

Periodic follow-up should be made to monitor for recurrence of the IPK or development of transfer lesions.