Are Acellular Dermal Matrices Effective For Grade 0 Ulcers And Fat Pad Augmentation?

Fat pad augmentation or the use of grafting in the ball of the foot and the heel has gained popularity over the past decade. The goal is simply to add cushioning or padding to areas that demonstrate a loss or displacement of natural fat due to an increased peak pressure.

   Patients typically present with pain and verbalize the discomfort they experience while walking barefoot or in shoes, flats and high heels. Patients complain they cannot walk barefoot or in sandals without significant pressure on the ball of the foot or the heel, and feel as if they are walking on pebbles. On the other hand, patients who have neuropathy present with a Grade 0 foot lesion and the physician observes the increased mechanical stress.

   In the latter presentation, it is our obligation to diagnose and treat this condition, and prevent progression of the Grade 0 ulceration to more severe levels of breakdown. A Grade 0 lesion by the classic Wagner system (see “A Guide To The Wagner Classification For Diabetic Foot Ulcers” below right) is a pre-ulcerative lesion, healed ulceration site or the presence of bony deformity. These patients usually present with calluses, with or without capillary bleeding, or a healed ulceration with dermal scarring.

   One can see increased pressure strain in the heel or the ball of the foot in all foot types. In these cases, clinicians will note subcutaneous atrophy or anterior displacement, which one may observe in the cavus foot where the fat that was once positioned under the metatarsal heads now bunches at the plantar digit sulcus. Genetics, aging, autoimmune diseases with collagen breakdown such as rheumatoid arthritis, previous steroid injections and trauma can also cause loss of the adipose layer. The amplified stress leads to superficial and deep skin problems associated with painful calluses, intractable plantar keratomas, skin breakdown with ulcerations, metatarsalgia, sesamoiditis, neuromas, plantar plate tears and certainly pain.

   Clinicians may use a number of methods to specifically analyze fat pad loss in a region. Pedography — with either a classic Harris Mat or a more modern floor-based and insole-based technological system — is available to identify peak pressure loads. One may employ ultrasound or MRI to measure the thickness of the fat pad.

   There have been significant advances in treatment options over the past decade. Traditionally, clinicians have offered offloading with pads, orthotics and/or changes in shoes to the patient. Surgical options include a lesser metatarsal V osteotomy, a Weil osteotomy or even a metatarsal head excision. Surgeons have also performed autolipotransplantation, a procedure in which the surgeon takes adipose tissue from the posterior calf or other body part, and transplants it to the plantar fat pad.1

Weighing The Pros And Cons Of Injection Therapy

Over the past decade, injection therapy has gained popularity with the use of collagen, silicone and dermal fillers. One may use dermal fillers off-label for fat pad augmentation. When it comes to injection therapy, clinicians may opt for Graftjacket Xpress® (KCI), Sculptra® (Sanofi Aventis), Radiesse® (Merz Aesthetics) or other commonly used aesthetic dermal replacements.

   Although some of these modalities have been marketed as cosmetic treatments, I have found positive outcomes with these products that have helped address a range of conditions from hallux valgus to hammered digit corns, facilitated relief of a heloma molle, provided padding over protruding hardware and offered heel pain cushioning.

   Most significant is the relief of pressure for previously ulcerated sites and in patients with diabetes who are at risk for further breakdown. When it comes to hemorrhagic calluses due to dermal capillary injuries, injection therapy can provide enough focal restoration that skin breakdown decreases.

   The benefit of injection therapy is that one can perform this in the office setting. Clinicians measure outcomes by patient feedback with decreased pain in sensate patients and clinical improvement in neuropathic patients. One can determine clinical improvement by performing follow-up peak pressure studies.

   Although these treatments are rewarding and fillers provide patients relief in their shoes, I have found limitations with injection therapy. The chemical compounds of the fillers break down over time with patients being able to obtain optimal relief for up to 10 months. Accordingly, there is a need for annual touch-up treatments. When it comes to radiopaque injectables like Radiesse®, which is made of calcium hydroxylapatite, one can see these products on X-ray migrate from their original injection locations.

   Furthermore, in patients with collagen disorders who have severe fat atrophy, fillers cannot provide the adequate fat restoration needed to provide desirable outcomes. Lastly, using these products for off-label indications can be cost-prohibitive.

Rethinking Our Approach To Grade 0 Ulcerations

Grade 0 ulcerations in patients with diabetic neuropathy are slightly more challenging because they typically do not have pain. The physician must educate the patient on the importance of addressing the pathology even though he or she may not feel a problem. While treatment options including padding and insoles are beneficial, they may be limiting and unrealistic on a daily basis. Granted, these traditional methods are standards in our profession but they fail to be more proactive at focusing on treatment of high-pressure areas with bone deformities. Until a patient presents with skin breakdown and the presence of Grade 1 ulceration, we typically sit and wait.

   We should not overlook patients who present in the Grade 0 class as treatment for these conditions can delay or even prevent a more serious condition such as ulceration, infection and amputation. Treatment of grade 0 ulceration is indicated in healthy individuals and more importantly in the high-risk patient.

   A more aggressive approach is required for patients who have severe fat atrophy and an inability to perform activities due to pain, hemorrhagic calluses, and blistering. Furthermore, individuals who have diminished sensation and neuropathy, high peak pressures and early skin breakdown need a more reliable and permanent solution. It is important to consider the varying degrees of peak pressure and load time on a given structure that can lead to skin breakdown, infections and ultimately amputations.

   When it comes to an extreme load-bearing region on the bottom of the foot, one can surgically address this by placing a piece of graft in the subcutaneous space. Surgeons can perform this procedure on either isolated submetatarsal regions or generally in the ball of the foot or the heel. Preoperative evaluation and medical management are imperative as immunocompromised patients may have difficulty healing.

Step-By-Step Insights On The Procedure

Incision placement depends on the location of the pressure load. However, I prefer the medial or lateral aspects of the foot.

   For the first, second or third submetatarsal or the global fat pad, I utilize a medial first metatarsal head incision. I will retract the medial common nerve to the great toe or the medial marginal vein if I encounter these after the incision. Tent and retract the plantar skin, and use a blunt instrument to create a space between the deep dermis and plantar plate. Most of the subcutaneous tissue is lost and there is a natural space that you can enter. You will encounter septal attachments and adhesions from the dermis to the deep layers, and may incise these accordingly.

   The graft of preference is a regenerative tissue matrix. Companies such as KCI, Wright Medical, Biomet and Integra provide grafts. There are varying ranges of thicknesses available, typically from 0.45 mm to 2.0 mm. The dimensions of the allograft depend on the size of the area in which you will be inserting the graft. Remember, it is easier to cut away excess than be short.

   One would open the graft and allow it to soak for at least 10 minutes although some grafts require a lengthier hydration. Proceed to pass a 2.0 absorbable suture through two distal corners of the free graft and tie a knot, leaving one long end of suture in each corner. Use a Keith needle to pass the suture from the open incision, through the subcutaneous tunnel and out the skin at the far end of the desired graft location. Pulling the Keith needle through the skin and gently pulling the absorbable suture taut allows the graft to shift into place.

   A blunt instrument can help guide the graft and allow adequate placement and seating. Tie the two ends of absorbable suture on the outside of the skin anchoring the graft. I have found that there is no need to anchor the graft at the end nearest the incision. Surgeons should take care to avoid kinking, folding, overlapping, bunching or stuffing the graft in the opening. One can insert the graft with it lying in place flat. Finally, irrigate the area and close the skin.

   Apply a bulky dressing and allow partial weightbearing in a surgical shoe. One would cut the absorbable suture ends flush with the skin at the second postoperative visit and allow patients to return to a supportive sneaker by week four. The graft ends are palpable and usually the patient can feel the cushion and graft as he or she walks for approximately six weeks.

   By the sixth postoperative week, the patient should be back to most normal activities with complete graft integration by 12 weeks.

   To help facilitate graft integration, I have utilized Laser Genesis (Cutera).

   Laser Genesis is a gradual warming of the dermis that allows for increased blood flow, oxygenation and collagen remodeling. Postoperative complications have included wound dehiscence in one patient. I have not seen graft rejection in my patients who have undergone this procedure.

   The remarkable changes noted with the procedure include relief of symptoms and a return to activities that patients could not otherwise perform. I do see a diminished need for pads as well as less potential for non-adherence. Most importantly, the potential lack of progression from Grade 0 ulcerations to more advanced stages is evident.

   Dr. Schoenhaus Gold is a Fellow of the American College of Foot and Ankle Surgeons, and is board-certified in foot surgery and reconstructive rearfoot and ankle surgery by the American Board of Podiatric Surgery. She is in private practice in Boca Raton, Fla.

References
1. Chairman EL. Restoration of the plantar fat pad with autolipotransplantation. J Foot Ankle Surg. 1994;33(4):373-9.
2. Rocchio TM. Augmentation of atrophic plantar soft tissue with an acellular dermal allograft: a series review. Clin Podiatr Med Surg. 2009;26(4):545-57.

   For further reading, see “Emerging Concepts In Cosmetic Foot Surgery” in the April 2011 issue of Podiatry Today, “Injectable Silicone: Can It Mitigate Plantar Pedal Pressure?” in the September 2008 issue or the DPM Blog “A Closer Look At The Plantar Fat Pad In People With Diabetes” at https://tinyurl.com/8ph97ns .