June 2017

Management of painful plantar fat pad atrophy

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Aging and a number of medical conditions can lead to atrophy of the fat pads under the heel and forefoot, which often causes considerable pain. Cushioned footwear and orthoses are mainstays of treatment, but research also supports the use of fat grafting in recalcitrant cases.

By Barbara Boughton 

The plantar fat pad serves as a cushion and a means of absorbing shock, but as individuals age it begins to atrophy. Like the tread of a tire, the heel fat pad can thin over time, often so much that a patient experiences heel pain that interferes with productivity and daily activities.1,2

“The higher the mileage we have on our feet, the more likely it is that the fat pads begin to wear out,” said James Hanna, DPM, New York State Podiatric Medical Association Board of Trustees, who practices in Lockport, NY.

A normal, healthy fat pad measures 1 to 2 cm in thickness. Patients who have plantar fat pad atrophy—when the fat pad measures less than 1 cm—may be asymptomatic, but others may present with the disturbing sensation that they are almost walking on bone.1 In patients with diabetes, heel fat pad atrophy is particularly problematic, since it may increase the risk of ulcers and associated comorbidities.3 Pedal fat pad atrophy, which is typically associated with pain under the heads of the metatarsals, can also occur.

Risk factors

Besides age, conditions that cause atrophy of the plantar fat pad include rheumatological diseases such as rheumatoid arthritis, scleroderma, and lupus, which affect the connective tissues in the feet,4 and conditions that result in abnormal pressures on the foot and heel, such as type 2 diabetes (especially in the presence of peripheral neuropathy or autonomic neuropathy)5 and cavus foot. Obesity and frequent use of high-heeled shoes also increases the risk of plantar foot pad atrophy.1

Atrophy of the plantar fat pad is also found in runners—especially endurance runners or longtime runners with high arches—and patients who’ve had corticosteroid injections for foot pain, according to Alex Kor, DPM, MS, a clinician in the podiatry department of Froedtert Hospital/Medical College of Wisconsin in Milwaukee and past president of the American Academy of Podiatric Sports Medicine.

It is vital to educate patients with fat pad atrophy about the importance of wearing foot orthoses throughout the day and the best ways to choose proper footwear.

“Even months or years later, you see foot pad atrophy in patients who’ve had multiple cortisone shots for heel pain,” Kor said.

Some patients with heel fat pad atrophy also have conditions such as plantar fasciitis that contribute to their pain, but the painful heel symptoms in most patients come from bursitis—occurring when the bursa sac that protects the heel becomes inflamed, according to Kor. Yet, some patients are asymptomatic, and heel fat pad atrophy may be an incidental finding during diagnosis or treatment of another foot condition, he added.

Diagnosis

Although researchers have used magnetic resonance imaging (MRI) and ultrasound to diagnose and characterize heel fat pad atrophy,3,6,7 diagnosis in clinical practice often relies on a history, physical exam, and x-rays (to rule out other conditions that can cause similar symptoms, such as stress fracture or plantar fasciitis).

“When pushing on the bottom on the feet in someone with heel fat pad atrophy, you can sometimes even feel the bones through the skin,” Hanna said. “Ultrasound and MRI are also very good at diagnosing heel fat pad atrophy, but these technologies are usually reserved for those cases where the findings from a clinical exam and history are equivocal.”

Jeffrey Johnson, MD, president of the American Orthopaedic Foot and Ankle Society and professor of orthopaedic surgery at Washington University in Chesterfield, MO, concurred.

“For a clinical diagnosis of heel fat pad atrophy, there is usually little value in getting an ultrasound and MRI, unless you are also trying to sort out some other source of the foot pain,” Johnson said.

Autologous fat grafting, or lipofilling, in which fat from other anatomical sites is injected into the bottom of the foot, can help address fat pad atrophy and potentially reduce the risk of ulceration in patients with diabetes. (Images courtesy of David Armstrong, DPM, MD, PhD.)

Conservative treatment

The mainstays of treatment for heel fat pad atrophy are custom molded foot orthoses with padding, shoes that provide padding and support for the feet while walking, and heel cups or cushioned socks that help reduce the impact of walking on the foot, experts say.

“Conservative treatment can be quite successful; it can ease pain and prevent symptoms from getting worse. The idea is to replace the fat pad with shock absorption from the outside of the foot. As a result, pressure on the foot—especially on the bones and skin, where there is often damage that seriously impacts health—can be relieved,” said John Steinberg, DPM, chief of podiatric surgery at Medstar Georgetown Hospital in Washington, DC. “Unfortunately, we often get pushback from patients who don’t want to be burdened with wearing an orthotic that they must transfer from shoe to shoe, or to have to wear a shoe that looks orthopedic.”

Thus, it is vital to educate patients about the importance of wearing foot orthoses throughout the day and the best ways to choose proper footwear that is sturdy and cushioned, Steinberg said.

Patients with heel fat pad atrophy often do well with viscoelastic orthotic devices, heel cushions, and heel cups—and any material that has at least 3 to 5 mm of cushion, Kor said. Orthoses should also have a cushioned topcover, such as those made of closed-cell polyethylene foam.

“You want a covering that is cushioned, but also does not break down over a short period of time,” Kor said.

In addition to these conservative treatments, interventions that involve injecting materials into the foot have been tried—with varying degrees of success. One technique is to inject silicone into the foot, but this technique is controversial, since the silicone can migrate over time.8,9 Complications from injecting a foreign substance in the foot are also possible, Hanna said.

Another method used by some clinicians is to inject dermal fillers into the foot, a procedure similar to those in which fillers are injected in the face to address wrinkles. These materials include products made with poly-L-lactic acid and hyaluronic acid, but they are not Food and Drug Administration-approved for use in the foot, and research into their efficacy for heel fat pad atrophy has been limited, Hanna said.

Fat grafting

One of the newest methods of treatment for foot fat pad atrophy is autologous fat grafting, or lipofilling, in which fat from other anatomical sites is injected into the bottom of the foot. Autologous fat grafting for the foot has been used since the 1990s, but early scientific studies on this technique were dogged with problems, especially necrosis of the fat. Recent research, however, has documented the effectiveness of autologous fat grafting for both pedal and heel fat pad atrophy.

In one study published in The Foot in 2014, a team of Italian researchers injected fat harvested from the abdomen in four patients during two sequential injections performed over 12 weeks.10 The four patients in the study had previously undergone repair of post-traumatic soft tissue loss of the foot with skin grafts and, in one case, a cross-leg fascio-cutaneous flap. All of the patients had pain in the plantar aspect of the foot after their surgeries, had difficulty bearing weight on the heel, and showed skin instability with recurrent ulcerations and callus formation. The heel fat pad injections were aimed at thickening the tissue at the plantar sole and increasing the weightbearing capability of the foot.

All four patients demonstrated restoration of the fat pad tissue and the functional structure of the sole of the foot after the lipofilling procedure, according to lead author Giovanni Nicoletti, MD, a plastic and reconstructive surgeon in the department of clinical, surgical, diagnostic, and paediatric sciences at the University of Pavia in Italy.

During recovery, the patients were advised to avoid dynamic and static plantar weightbearing for two weeks. Then, 30% partial dynamic and static plantar weightbearing was allowed, using crutches and soft socks, for two weeks. In the final two weeks of recovery, the patients could engage in full dynamic and static plantar weightbearing, wearing custom plantar insoles, custom shoes, or both.

All four patients experienced good outcomes from the surgery with no serious complications. However, clinicians should be aware of the risk of potentially serious complications associated with these procedures, including infection and fat necrosis from failed adipose tissue engraftment,10 Nicoletti said.

Fat grafting has also been tried as a means of preventing reulceration in high-risk diabetic feet. In a case report published in Plastic and Reconstructive Surgery Global Open,11 David Armstrong, DPM, MD, PhD, and colleagues used fat augmentation to address plantar fat pad atrophy and recalcitrant preulcerative lesions in a patient aged 37 years with type 2 diabetes who had previously undergone tibialis anterior tendon transfer for a progressive chronic styloid ulcer. After four weeks in a splint, the patient successfully transitioned to normal shoe gear, and had no complications or recurrence of his wound at six weeks, Armstrong says.

“The question we asked was: Will this type of grafting hold up? It appears it will, although we don’t have good long-term data yet,” said Armstrong, a professor of surgery at the University of Arizona and deputy director of the Arizona Center for Accelerated Biomedical Innovation in Tucson. “By using the technique of fat grafting for heel fat pad atrophy, we give our patients with diabetes time to recover from ulcers, reduce stress on the feet, and decrease the risk of ulcers. We can heal many of our diabetic patients with ulcers by using other techniques, but the real tough nut to crack is keeping these patients healed and giving them quality of life.”

As well as being a reconstructive surgery, the procedure was a means to achieve tissue repair, he said.

“Thus, we could interrupt the cycle of reulceration in the diabetic foot and keep patients with diabetes and diabetic neuropathy in remission [ulcer-free],” Armstrong said.

Pittsburgh RCT

In the first randomized clinical trial done on autologous fat grafting for pedal fat pad atrophy, researchers at the University of Pittsburgh performed one of the largest studies yet on the technique. The investigators randomized 25 patients with pain under the head of the metatarsal and diagnosed with pedal fat pad atrophy to fat grafting surgery or usual care.1 The cause of fat pad atrophy among the patients included prior foot surgery, failed neuroma surgery, steroid injections, and overuse.

At six months, the patients who received injection of autologous fat, harvested from abdominal or flank subcutaneous tissue, had significantly greater improvement in pain from baseline compared with the control group as assessed by the Manchester Foot and Ankle Disability Index. At 12 months, the intervention group had statistically significant improvements in function, pain, and work/ leisure activities compared with baseline, as measured with the same assessment tool.

“The only complications of the surgery were bruising and swelling, and the surgery was performed as an outpatient procedure,” said Jeffrey Gusenoff, MD, one of the lead investigators for the study, and associate professor of plastic surgery at the University of Pittsburgh Medical Center. “Patients were cautioned not to engage in extended walking after surgery for four to six weeks.”

The patients also wore a cushioned supportive sneaker during full weightbearing, and no barefoot walking was permitted during the recovery period of four to six weeks. Patients used towels placed on the shower floor or shower pads during the short time each day they weren’t wearing protective shoes.

The University of Pittsburgh research group will continue to follow the patients in the trial. The control group in the trial that received usual care will undergo autologous fat grafting and be followed for a year, and those who initially underwent surgery will be followed for an additional year, Gusenoff said. The research group also plans to assess MRI scans taken before and after the fat pad procedures in the clinical trial to look for changes in bone and soft tissue that could explain the decreases in pain seen in the study. Another study will assess a procedure for injecting fat into the heel in patients with chronic plantar fasciitis associated with heel fat pad atrophy.

Addressing deformity

In some patients, however, heel fat pad atrophy is caused by an underlying deformity that creates a high-pressure area under the foot. These deformities include claw toe deformity, rocker bottom foot deformity, and problems in ankle alignment, Johnson said. In patients with diabetes, for instance, slowly progressive deformities associated with diabetic neuropathy—such as claw toe deformity—can increase pressure under the heel as the toes lose function, Johnson said. As a result, these patients are at risk for both fat pad atrophy and ulceration.8

In cases in which a heel cushion or foot orthoses are insufficient to alleviate the heel pressure, surgical correction of the deformity may be necessary, he said. These procedures have the surgical risks associated with most orthopedic procedures, including infection, blood clots, and bleeding from anticoagulant therapy after surgery. They also require a significant recovery time in a cast, splint, walking boot, or combinations of these, so should be performed only when  necessary, Johnson said.

Barbara Boughton is a freelance writer based in the San Francisco Bay Area.

REFERENCES
  1. Gusenoff JA, Mitchell RT, Jeong K, et al. Autologous fat grafting for pedal fat pad atrophy: A prospective randomized clinical trial. Plast Reconstr Surg 2016;138(5):1099-1108.
  2. Rome K, Campbell R, Flint A, et al. Heel pad thickness—a contributing factor associated with plantar heel pain in young adults. Foot Ankle Int 2002;23(2):142-147.
  3. Kao PF, Davis BL, Hardy PA. Characterization of the calcaneal fat pad in diabetic and non-diabetic patients using magnetic resonance imaging. Magn Reson Imaging 1999;17(6):851-857.
  4. Falsetti P, Frediani B, Acciai C, et al. Heel fat pad involvement in rheumatoid arthritis and in spondyloarthropathies: An ultrasonagraphic study. Scand J Rheumatol 2004;33(5):327-331.
  5. Hsu TC, Lee YS, Shau YW. Biomechanics of the heel fat pad for type 2 diabetic patients. Clin Biomech 2002;17(4):291-296.
  6. Hall MM, Finnoff JT, Sayeed YA, et al. Sonographic evaluation of the plantar heel in asymptomatic endurance runners. J Ultrasound Med 2015;34(10):1861-1871.
  7. Bus SA, Maas M, Cavanagh PR, et al. Plantar fat-pad displacement in neuropathic diabetic patients with toe deformity. A magnetic resonance imaging study. Diabetes Care 2004;27(10):2376-2381.
  8. Bowling FL, Metcalfe SA, Wu S, et al. Liquid silicone to mitigate plantar pedal pressure. J Diabetes Sci Technol 2010;4(4):846-852.
  9. Balkin SW, Kaplan L. Injectable silicone and the diabetic foot: a 25-year report. Foot 1991;1(2):83-88.
  10. Nicoletti G, Brenta F, Jaber F, et al. Lipofilling for functional reconstruction of the foot. Foot 2014;24(1):21-27.
  11. Luu CA, Larson E, Rankin TM, et al. Plantar fat grafting and tendon balancing for the diabetic foot ulcer in remission. Plast Reconstr Surg Glob Open 2016;4(7):e810.
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