Current Concepts In Surgical Offloading Of The Diabetic Foot

Author(s): 
Nicholas Todd, DPM, Meagan Jennings, DPM, FACFAS, and Shannon Rush, DPM, FACFAS

When conservative offloading options have failed and patients with diabetes are at risk of limb loss, one might consider surgical offloading for diabetic foot ulcers. These authors offer their experience with operative techniques for offloading ulcers in areas such as the midfoot, first ray and lesser metatarsals.

   Treating deformity and secondary ulceration in the diabetic foot is a complicated endeavor. Multiple comorbidities such as polyneuropathy, peripheral arterial disease, large body mass indices and marginal adherence have the potential to sabotage the most thoughtful surgical plan.

   Accordingly, it is necessary to scrutinize each patient with a diabetic foot ulceration and the patient’s underlying etiologies prior to executing any surgical plan. Often, we overlook underlying deformity and pathomechanics when treating diabetic ulceration. In this article, we will discuss several surgical offloading measures that one can employ to treat or prevent ulceration.

   Historically, offloading of ulcers and pre-ulcerative areas has been a mainstay in the treatment of the diabetic foot. Non-surgical offloading modalities such as total contact casts, Charcot restraint orthotic walker (CROW) boots and orthoses are among the options.

   The question remains: when does one consider surgical intervention for the diabetic foot? We must temper the indications for surgical intervention against the potential risk of infection, Charcot neuroarthropathy and loss of limb. In general, we feel depth shoes and custom insoles can be effective in managing a plantigrade foot without osseous prominence or tendon contracture such as equinus.

   One needs to approach operative management of the diabetic foot in a rational and systematic fashion. A dogmatic surgical approach will often lead to failure and possible limb loss. It is imperative that the surgeon does a thorough examination and determines the procedure that would best eliminate or prevent re-ulceration in the patient with diabetes. Often, there is a logical underlying biomechanical abnormality or osseous deformity that surgeons must address in order to properly correct the problem.

   Podiatric surgeons should follow basic principles when trying to offload the diabetic foot surgically. First, only perform surgery if conservative care has failed or the foot/ankle is at risk for imminent infection or amputation. Second, one must understand the biomechanics that are placing the foot at risk. Lastly, when addressing the deformity, there is a need in some instances to address proximal pathology to correct distal pedal issues.

Pertinent Pearls On Correcting Hindfoot Malalignment

A common example of a difficult to treat ulceration is a sub-fifth metatarsal head ulceration secondary to a fixed hindfoot varus. These plantar lesions are difficult to manage with orthotics and shoe modifications. The fixed varus makes the foot more rigid and less able to adapt to sagittal pressure.

   In addition, equinus exacerbates these ulcerations. We feel that by correcting the hindfoot alignment with a lateral closing wedge osteotomy and gastrocnemius recession, outcomes are predictably successful.

Surgical Options For First Ray Ulceration

Wounds of the plantar aspect of the great toe (hallux interphalangeal joint ulcerations) are extremely common in neuropathic patients. The etiology of the ulceration arises from increased plantar pressure due to limitation of the first metatarsophalangeal joint (MPJ). Alterations in plantar pressure can arise from interphalangeal sesamoids or hallux rigidus. Simple removal of the interphalangeal sesamoid is indicated for a prominent sesamoid without hallux rigidus.

   Keller arthroplasty may also be indicated for cases of recalcitrant hallux ulceration. One must exercise caution as there is additional transfer pressure to the second ray as a result of this procedure. Direct attention to an Achilles lengthening or gastroc recession if there is concern for transfer ulceration. Armstrong and colleagues analyzed complications and outcomes of first MPJ arthroplasty (Keller arthroplasty) in comparison to the standard, non-surgical management of hallux interphalangeal joint wounds.1 They found the surgical group healed quicker (24 days versus 67 days respectively) with recurrence being significantly lower.

What You Should Know About First Metatarsal Head Ulcerations

A common area of concern is the first metatarsal head. This area is prone to ulceration, which can occur due to a rigid or a flexible cavus deformity as well as tendon imbalances. It is imperative that the foot and ankle surgeon recognizes the biomechanical etiology. Hansen coined the term “peroneus longus overpull.”2 A careful examination of patients with sub-first metatarsal head ulceration may allow the surgeon to discover an overdrive of the peroneus longus creating a focal first ray cavus. A simple clinical exam of the first ray will determine if the ray is fixed or flexible in the sagittal plane. Active ankle plantarflexion with plantar pressure beneath the first and second metatarsal heads will highlight the sagittal plane overdrive of the first ray.

   We feel the most appropriate treatment for sub-first metatarsal head ulceration secondary to long peroneal overdrive is a tenodesis of the peroneus longus to the peroneus brevis. The surgical approach centers over the cuboid parallel to the fourth ray. One can easily locate the peroneal tendons. Trace the peroneus longus to the plantar cuboid tunnel and transect it. One can anastomose the distal end of the peroneus longus to the lateral band of the plantar fascia in this area. Sew the proximal end of the peroneus longus tendon through a longitudinal incision in the peroneus brevis. Postoperatively, the patient wears a walking pneumatic boot and may ambulate immediately.

   In the case of a fixed deformity, one can also correct this in a number of ways. We prefer a distal oblique dorsal closing wedge osteotomy for relatively small amounts of correction and a tarsometatarsal arthrodesis for any correction greater than 5 mm.

Key Insights On Offloading Lesser Metatarsal Parabola Ulcerations

Neuropathic ulcerations under the lesser metatarsal heads can arise from a variety of biomechanical faults. These include but are not limited to: abnormal metatarsal parabola; transfer lesions secondary to first ray pathology; and plantar fat pad atrophy. Ankle equinus almost always plays a role to some degree in the pathogenesis of forefoot plantar neuropathic ulcers.

   We advocate early percutaneous Achilles release as an important adjunct to wound care and offloading for plantar forefoot ulcerations. One can perform a percutaneous Achilles release with local anesthesia in many instances and manage the ulceration with a short leg cast.

   Boulton and co-workers showed that neuropathic patients had higher plantar pressures under the forefoot.3 The goal for patients with diabetic neuropathy is to mitigate these plantar pressures. Armstrong and colleagues compared peak plantar pressures after Achilles tendon lengthening.4 They found that ankle joint dorsiflexion significantly increased and peak plantar pressures were greatly reduced with percutaneous Achilles lengthening.

   We prefer a triple hemi-section lengthening of the Achilles. Be careful not to over-lengthen the Achilles as it can result in uncontrolled ankle dorsiflexion after hemisection. We prefer lengthening to no more than 5 degrees past neutral. After lengthening, one can manage the Achilles in the same short leg cast that he or she would use with the forefoot ulceration. Patients need a minimum of six weeks to heal before they can walk in a shoe.

   When it comes to bone resection for forefoot ulceration, the surgeon may perform an isolated metatarsal head resection, osteotomy, a plantar condylectomy or a panmetatarsal head resection. Absolute criteria for each clinical scenario are difficult to define. The foot and ankle surgeon must be cautious not to create transfer ulcerations and secondary deformity.

   Sub-second metatarsal head ulceration is often the result of a dorsal dislocation of the second metatarsophalangeal joint, a long second ray or a hypermobile or unstable first ray. To address a long ray or dislocated second MPJ, we prefer a distal oblique shortening osteotomy and Girdlestone-Taylor flexor to extensor tendon transfer to the top of the second toe.

   Isolated metatarsal head resections are effective in eliminating plantar ulceration but can result in the obvious transfer lesion. This is especially predictable when one has not addressed an underlying biomechanical problem such as ankle equinus. Griffiths and colleagues reviewed patients with diabetes who underwent metatarsal head resections for recalcitrant diabetic foot ulcerations.5 They found that the mean time for healing ulcerations conservatively was nine months while the mean time of healing for the ulceration following a metatarsal head resection was 2.4 months.

   Often, we manage the plantar forefoot ulceration for too long unsuccessfully, resulting in radical ray resection or transmetatarsal amputation. Early and definitive surgical care can be very beneficial for patients who do not respond to non-surgical offloading. Biomechanically, a panmetatarsal head resection shortens the metatarsal parabola and distributes weight evenly across the forefoot.

   One should consider panmetatarsal head resection in scenarios with large plantar ulcerations involving multiple metatarsal heads. In addition, surgeons should consider the panmetatarsal head resection if two or more lesser metatarsal heads have been removed. Cohen and colleagues showed that panmetatarsal head resection and transmetatarsal amputation had higher clinical success than a solitary partial ray resection.6

   The problem with the panmetatarsal head resection is elimination of the first metatarsophalangeal joint. The loss of the first MPJ decreases the stability of the medial foot and arch height. Hamilton and colleagues reviewed patients who had ulceration due to abnormal metatarsal parabola.7 The patients underwent a gastrocnemius recession, a peroneus longus to brevis tendon transfer and resection of the second through fifth metatarsal heads. All patients achieved a healed plantigrade foot without ulcer recurrence or transfer callus.

   First, the gastroc recession offloads the forefoot as we previously described. With the first metatarsal head intact and the removal of the lesser metatarsal heads, there is increased pressure on the first metatarsal head. The peroneus longus to brevis transfer offsets this increased pressure, thus creating a stable and ulcer-free foot.

How To Address Digital Ulcerations

Digital deformities are common deformities even among healthy patients. Often, one can accommodate these deformities with padding or treat them surgically with arthrodesis or arthroplasty. Flexor clawing secondary to the intrinsic minus foot, flexor stabilization and poor balance can lead to distal tuft ulceration and osteomyelitis. It is one of the most common causes of digital amputation in the diabetic foot. When padding is not providing desired results, perform a flexor tenotomy. Surgeons can perform a flexor tenotomy with the patient under local anesthesia. The results are often satisfying and dramatic.

   Tamir and co-workers performed a retrospective study of percutaneous flexor tenotomies in patients with claw toes and ulcerations.8 The results showed that the tenotomy facilitated healed toes with ulcers in three weeks and there were no recurrences in ulceration. Interestingly there were no complications in the study.

   This surgical technique involves a stab incision under the intermediate phalanx. Cut the flexor and bandage the digit in its corrected position. One must remember that when evaluating patients with these digital deformities, it is difficult to achieve satisfactory results with a rigid digital deformity without performing an adjunctive procedure such as osteoclasis.

What You Should Know About Midfoot Ulcerations

Debate rages on the appropriate treatment of Charcot foot. The significant deformities that occur often lead to predictable ulceration with secondary infection and often result in loss of limb. Plantar ulceration can occur secondary to Charcot collapse and a resulting secondary deformity. One can perform an exostectomy to treat Charcot deformity, which is often characterized as a rocker bottom foot. Surgeons often perform the exostectomy in conjunction with surgical wound care.

   Catanzariti and colleagues reviewed 20 patients who underwent ostectomy for chronic or recurrent ulceration in the midfoot secondary to diabetic neuroarthropathy.9 Wounds resolved in 74 percent of the cases. The study authors noted failures with ulcerations of the lateral column. The authors concluded that the ostectomy is successful in addressing Charcot ulcerations of the medial column. When patients use post-op bracing, they can expect low recurrence in ulceration, according to the study authors.

   Patients with lateral wounds need education on the fact that there is a high chance of re-ulceration and a possible need for further reconstructive surgery. One can best approach exostectomies of the midfoot from either the lateral or medial aspect of the foot. Postoperative care usually aligns with the need for wound care and often results in offloading and immobilization in some form.

   In situations in which the joints of the midfoot are grossly unstable and exostectomy is not appropriate, a reconstruction with osteotomy or arthrodesis is required. The appropriate choice of fixation for Charcot reconstruction often employs a combination of internal and external fixation, intramedullary rods and locking plate techniques.

   Grant and colleagues popularized beaming to correct the Charcot deformity by recreating anatomical alignment.10 This beaming concept has become popular but requires large diameter screws.

   We advocate a 7.3-mm cannulated screw or Synthes 6.5-mm fusion bolt. Another option for internal stabilization is locking plate fixation, which can stabilize and span the medial column. The one significant concern with this form of fixation is the need for good primary incision healing. Wound dehiscence results in exposed hardware. The endpoints for correction are restoring the talometatarsal axis and a stable fusion.

   External fixation is another valuable option for cases in which internal fixation is not appropriate. One can combine tensioned fine wire fixation with intramedullary screw fixation to afford excellent stability during the healing process.11 However, surgeons must approach external fixation with caution in the diabetic foot due to a high risk of infection.

In Conclusion

Properly designed surgical intervention will decrease healing time, reduce recurrence rates and remove or reduce deformities in the patient with diabetes. The foot and ankle surgeon must remember to approach surgical intervention in the patient with diabetes with thorough planning and caution. When surgeons use this approach, surgical offloading of the diabetic foot can save limbs and improve a patient’s lifestyle.

   Dr. Todd is a Surgical Fellow with the Silicon Valley Foot and Ankle Fellowship at the Palo Alto Foundation Medical Group in Mountain View, Calif.

   Dr. Jennings is affiliated with the Palo Alto Foundation Medical Group in Mountain View, Calif. She is the Chief of the Department of Podiatric Surgery at El Camino Hospital in Mountain View, Calif.

   Dr. Rush is affiliated with the Palo Alto Foundation Medical Group in Mountain View, Calif. He is the Director of the Silicon Valley Foot and Ankle Fellowship.

References

1. Armstrong DG, Lavery LA, Vazquez JR, et al. Clinical efficacy of the first metatarsophalangeal joint arthroplasty as a curative procedure for hallux interphalangeal joint wounds in patients with diabetes. Diabetes Care. 2003; 26(12):3284–3287.
2. Hansen ST. Tendon transfers and muscle-balancing techniques. In: Hansen ST (ed): Functional Reconstruction of the Foot and Ankle. Lippincott Williams & Wilkins, Philadelphia, 2000, pp. 439-441, 462-467.
3. Boulton AJ, Hardisty CA, Betts RP, Franks CI, Worth RC, Ward JD, Duckworth T. Dynamic foot pressure and other studies as diagnostic and management aids in diabetic neuropathy. Diabetes Care. 1983; 6(1):26-33.
4. Armstrong DG, Stacpoole-Shea S, Nguyen H, Harkless LB. Lengthening of the Achilles tendon in diabetic patients who are at high risk for ulceration of the foot. J Bone Joint Surg Am. 1999; 81(4):535–538. [published erratum appears in J Bone Joint Surg Am. 2000; 82-A(10):1510]
5. Griffiths GD, Wieman TJ. Metatarsal head resection for diabetic foot ulcers. Arch Surg. 1990; 125(7):832–835.
6. Cohen M, Roman A, Malcolm WG. Panmetatarsal head resection and transmetatarsal amputation versus solitary partial ray resection in the neuropathic foot. J Foot Surg. 1991; 30(1):29–33.
7. Hamilton GA, Ford LA, Perez H, Rush SM. Salvage of the neuropathic foot by using bone resection and tendon balancing: a retrospective review of 10 patients. J Foot Ankle Surg. 2005; 44(1):37–43.
8. Tamir E, McLaren AM, Gadgil A, Daniels TR. Outpatient percutaneous flexor tenotomies for management of diabetic claw toe deformities with ulcers: a preliminary report. Can J Surg. 2008; 51(1):41–44.
9. Catanzariti AR, Mendicino R, Haverstock B. Ostectomy for diabetic neuroarthropathy involving the midfoot. J Foot Ankle Surg. 2000; 39(5):291–300.
10. Grant WP, Garcia-Lavin S, Sabo R. Beaming the columns for Charcot diabetic foot reconstruction: a retrospective analysis. J Foot Ankle Surg. 2011; 50(2):182-9.
11. Lamm B, Gottlieb H, Paley D. A two-stage percutaneous approach to charcot diabetic foot reconstruction. J Foot Ankle Surg. 2010; 49(6):517-22.

   Editor’s note: For further reading, see “Current Concepts In Surgical Offloading Of DFUs” in the July 2009 issue of Podiatry Today, “A Guide To Surgical Offloading In The Neuropathic Foot” in the March 2007 issue or “Assessing The Use Of Ex-Fix For Offloading In Diabetic Limb Salvage” in the February 2012 issue.

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