A Guide To Effective Forefoot Salvage Procedures

It is believed that 15 percent of diabetics will develop a foot or leg ulceration at some point during the course of their disease and that 50 percent will recur within 18 months.1 Approximately 80 percent of diabetic ulcers occur plantarly due to abnormal pressures. Most of these ulcers can be treated with sharp debridement, offloading devices and local wound care.2-4 Once you’ve achieved ulcer healing, utilizing custom orthotics with extra depth shoes will often prevent recurrence and reduce the needed frequency of pre-ulcerative keratoma debridements. Unfortunately, many ulcerations develop acute infections or reoccur despite our best conservative efforts. At this point, we must consider surgical intervention as a vital part of the treatment plan for these patients. The primary goal of diabetic foot surgery is to salvage as much of the foot as possible and reduce the risk of lower extremity amputation. A secondary goal is to maintain functional stability and allow the patient to make a quicker return to his or her daily, recreational and work activities. When we discuss foot surgery with a diabetic patient and his or her family, there is often tremendous anxiety. It is critical to explain the goals of the procedure and that an additional procedure or amputation may be necessary. By performing surgery, we’re often able to prevent the need for amputation in the future. Several studies have revealed that once a diabetic lower extremity amputation has been performed, the risk of additional amputation is greater than 50 percent within five years. In addition, the three-year survival rate after an amputation is only 50 percent.5-6 Be Aware Of Pertinent Biomechanical Considerations When contemplating surgical management of a recurrent ulceration or acute infection, you should always consider the biomechanical effects of the foot that may have contributed to the cause of the ulceration as they may influence the results of surgical treatment. For example, plantar hallux ulcers are often caused by hallux limitus and ankle equinus, which can be treated surgically. Therefore, some surgical procedures will result in fewer post-op complications and better outcomes if you address the biomechanics at the time of surgery. Employing custom orthotics in conjunction with surgical care will also help facilitate improved patient outcomes. Orthotics will help minimize the complexity of surgical procedure choices. For example, if the primary cause of a plantar hallux ulceration is hallux limitus with abnormal pronation, then performing a Keller bunionectomy and utilizing a slightly inverted functional foot orthotic should address the biomechanical etiology, minimize pressure under the hallux and prevent recurrence. Keep in mind the most common diabetic forefoot wounds occur at the plantar aspects of the metatarsal heads, the plantar aspect of the hallux and the dorsal and distal aspects of the digits. These are areas of the foot that receive the most stress and shearing forces in gait. How Should You Address Ulcerated Lesser Digits? Lesser digits have the greatest risk of ulceration when motor neuropathy results in contracture of the joints. Distal digital or dorsal joint ulcers quickly occur from shearing forces and pressure against shoes. When considering hammertoe repair on a patient with diabetes, it is crucial to remember that motor neuropathy will persist following repair, making an arthroplasty a short-lived solution. Therefore, arthrodesis procedures are preferred for treating proximal IP joints unless there is bone infection. Due to intrinsic muscle wasting and neuropathy, ulcers often develop at the tip of the distal phalanx, dorsally over the proximal or distal phalanx or on the side of the digit due to pressure from an adjacent toe. Although amputation is an option, it is often unnecessary if bone infection is localized to the ulcer site. In this instance, performing an arthroplasty or distal tuft resection (terminal Symes) is preferable. A flexor tenotomy is also an option for treating flexible hammertoe deformities. Reviewing The Options For First Ray Dilemmas The primary causes of ulceration at the plantar aspect of the hallux or first metatarsal are abnormal biomechanics and structural deformities. Ulcers underneath the hallux are often due to abnormal pronation, hallux limitus, enlarged condyles or an accessory sesamoid. Treatments include a hallux IP arthroplasty or Keller bunionectomy. In our experience, IP arthroplasties only work well in sedentary patients. Active patients often develop a hallux extensus deformity or hallux hammertoe (malleus). The Keller bunionectomy seems to alleviate pressure more effectively and is preferable unless the distal portion of the proximal phalanx is infected. In cases of hallux malleus, be aware that a distal ulceration often develops, which you may treat with an IPJ fusion. Plantar first metatarsal head ulcers are more challenging to treat surgically due to the greater involvement of biomechanical forces. First metatarsals are often rigidly plantarflexed in the diabetic patient. In order to correct this problem and prevent recurrent ulceration, you’ll usually need to perform a proximal metatarsal procedure. We have found that plantar condylectomies and/or sesamoidectomies have unpredictable results. We prefer to perform a sagittal Z osteotomy or a Juvara C procedure in order to achieve an adequate amount of first ray dorsiflexion and alleviate plantar pressures. Key Pointers For Treating Lesser Metatarsals You’ll often find that the plantar metatarsal heads of diabetic patients have excessive pressure due to neuropathic changes. In cases of chronic neuropathy, the foot develops an anterior cavus and ankle equinus, causing hammering of the digits, plantarflexion of the metatarsals and early heel-off during gait.7 Additionally, a diabetic patent may have fat pad atrophy, reducing the cushioning to the metatarsal phalanageal joints that are now receiving extra pressure. Ideally, you can alleviate this pressure with custom orthotics, extra depth or rocker bottom shoes, keratoma debridements and emphasizing stretching exercises for equinus.8 In 1992, a study by Young demonstrated that regular debridements of keratomas caused by repetitive pressure reduce the peak plantar pressures by 26 percent.9 Other studies have revealed that patients seen more frequently in a foot clinic had less severe ulcerations and were less likely to undergo surgery than those who had infrequent care.6,8 However, if the keratomas or ulcers persist, performing a pan metatarsal head resection in conjunction with a first MTP joint fusion, hammertoe repair and possible tendo-Achilles lengthening may be necessary.10 It is our preference to avoid using first MTPJ implants with a pan metatarsal head resection because these patients often have a higher risk of postoperative infection and may have preexisting soft tissue or bone infection. Performing arthrodesis of the PIPJs of digits 2 to 4 is also recommended in order to stabilize the muscle imbalance to these joints and reduce retrograde pressure to the forefoot. If ankle equinus is present, a gastrocnemius recession or percutaneous TAL is vital to preventing recurrent ulceration. Individual plantar metatarsal ulcers may also occur due to abnormal metatarsal length, trauma or prior bone infection. In these instances, you may perform isolated metatarsal procedures such as condylectomies, osteotomies and resections. However, if more than one metatarsal is involved, performing a pan metatarsal head resection will produce a more predictable and manageable outcome. Final Notes It is encouraging that more than 80 percent of diabetic-related amputations are preventable with regular podiatric exams, patient education, custom orthotics and, sometimes, surgical intervention.6 Surgical management plays a vital role in preventing diabetic foot infections and amputation. New advances in podiatric surgical care will hopefully further reduce the incidence of amputation for the next generation of patients with diabetes. Dr. Feit (on the right) is a Fellow of the American College of Foot And Ankle Surgeons and practices privately in San Pedro and Torrance, Calif. He is Past President of the Los Angeles chapter of the American Diabetes Association. Dr. Peters is a surgical resident at the San Pedro Peninsula Hospital in San Pedro, Calif. Dr. Steinberg (pictured) is an Assistant Professor in the Department of Orthopaedics/Podiatry Service at the University of Texas Health Science Center.
 

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References 1. Reiber GE, Boyko EJ, Smith DG: “Lower Extremity Foot Ulcers and Amputation in Diabetes,” Diabetes in America, 2nd Ed, p409, National Institute of Diabetes and Digestive and Kidney Disease, National Institutes of Health, Bethesda, MD, 1995. 2. Boulton AJM, Hardisty CA, Betts RO, et al: Dynamic foot pressure and other studies as diagnostic and management aids in diabetic neuropathy. Diabetes Care 6:26m 1983. 3. Murray HJ, Yound MJ, Hollis S, et al: The association between callus formation, high pressures and neuropathy in diabetic foot ulceration. Diabet Med 13: 979, 1996. 4. Reiber GE, Vileik L, Boyko EJ, et al: Causal pathways for incident lower-extremity ulcers in patients with diabetes from two settings. Diabetes Care 22: 157, 1999. 5. Most RS, Sinnock P: The epidemiology of lower extremity amputations in diabetic individuals. Diabetes Care 1983; 6: 87-91. 6. Edmonds ME, Blundell MP, Morris ME, et al.: Improved survival of the diabetic foot: the role of a specialized foot clinic. Q J Med 60: 763-771, 1986. 7. Tesfaye S, Ward JD. Clinical features of diabetic polyneuoropathy. In: Veves A, ed. Clinical management of diabetic neuropathy. Totowa, NJ: Humana Press, 1998: 49-60. 8. Sage RA, Webster JK, Fisher SG: Outpatient Care and Morbidity Reduction in Diabetic Foot Ulcers Associated with Chronic Pressure Callus. JAPMA 91: 6, 2001 9. Young MJ, Cavanagh PR, Thomas G, et al: The effect of callus removal on dynamic plantar foot pressures in diabetic patients. Diabet Med 9: 55, 1992. 10. Giurini JM, Basile P, Chrzan JS, et al. Panmetatarsal head resection: a viable alternative to the transmetatarsal amputation. JAPMA 83, 1993.