Point-Counterpoint: Is Tendon Lengthening A Worthwhile Treatment For Diabetic Forefoot Ulcers?

Yes.

This author notes that when one combines Achilles tendon lengthening with other treatments for the diabetic foot, it can help heal lower extremity wounds and prevent wound recurrence and amputation.     

By J. Monroe Laborde, MD, MS

Diabetic neuropathy results in decreased protective sensation and tendon imbalance.^1,2 Tendon imbalance, especially Achilles or gastrocnemius-soleus tightness, causes increased stress in the foot.^3,4 This stress can cause a callus followed by a forefoot ulcer.³ Accordingly, let us take a closer look at tendon imbalance correction, Achilles or gastroc-soleus tightness correction and other tendon lengthenings, and how they compare to other forms of treatment for diabetic forefoot problems.

Foot ulcers commonly become infected and lead to amputation.⁵ Approximately 85 percent of patients with diabetes who have an amputation have had foot ulcers.⁵ Healing foot ulcers and preventing their recurrence could prevent most amputations in patients with diabetes. Foot ulcer treatment consists of managing infection, arterial problems and high stress in the foot. One may address infection with antibiotics and debridement. If the patient lacks both pedal pulses, I recommend vascular evaluation and treatment. One can decrease stress in the foot through conservative methods such as shoe modification, walkers and total contact casts (TCC), or by surgical treatment such as tendon lengthenings.³       

Achilles tendon or gastroc-soleus lengthening can be helpful as a primary or adjunctive treatment that usually heals foot ulcers.^2,6-18 Treatment of forefoot ulcers with tendon lengthening has good literature support, both for healing ulcers and preventing recurrence.^2,6-18 Some authors have recommended tendon balancing to prevent forefoot ulcers.^3,16,18,19 A study focusing on tendon lengthening in the largest known series of 100 plantar foot ulcers appeared in Podiatry Today.¹⁸ This larger study confirms the excellent results of prior studies for healing ulcers and preventing recurrence and amputation. I previously published a detailed literature review on the benefits of tendon balancing for diabetic foot problems.¹⁶

For plantar toe ulcers, one can perform percutaneous flexor tenotomies. Surgeons can perform a gastrocnemius recession for ulcers that are plantar to the metatarsal heads. Add posterior tibialis tendon lengthening to the gastrocnemiussoleus recession for ulcers plantar to the fifth metatarsal, and add peroneus longus tendon lengthening for ulcers plantar to the first metatarsal. Gastrocnemius-soleus recession results in much fewer heel ulcers than does Achilles tendon lengthening.^16,18-21

What The Literature Reveals About The Benefits Of Tendon Lengthening

Tendon lengthening in the calf has fewer complications than bony procedures in the foot and ankle, especially if the patient has diabetes and/or has no pedal pulses.^16,18,20-23 Tendon surgery seems preferable to bony procedures in patients with diabetes, smokers and patients with foot ulcers, infection and/or without pedal pulses.^16,18,20-23

Tendon lengthening heals more ulcers than wound care and TCC.^16,18,24,25 A meta-analysis of the literature revealed that “good” wound care healed only 31 percent of 458 diabetic foot ulcers in five months.²³ The TCC healed an average of 80 percent of diabetic foot ulcers.25 Over 90 percent of 100 ulcers heal after tendon lengthening and they heal more quickly so ulcers have less chance to get infected.^16,18 Mueller and colleagues reported that 81 percent of 26 forefoot ulcers recurred two years after healing with TCCs.⁸ In two studies, I reported that three of 18 forefoot ulcers recurred at a 45-month follow-up and 10 of 98 plantar foot ulcers recurred after tendon lengthening.^13,18 Guyton reported a 30 percent complication rate with TCCs.²⁶

Resection of the metatarsal head, metatarsal osteotomy and partial foot amputation all have high complication rates, including frequent transfer ulcers and amputation of the entire foot.^16,22,23 Tendon lengthening heals more ulcers with much less recurrence and fewer other complications including fewer transfer ulcers and amputations.^2,6-18,20,21  

Tendon lengthening appears to be an effective treatment and is my initial treatment of choice for diabetic ulcers of toes and ulcers plantar to the metatarsal heads.^2,6-18 If ulcers recur, one can repeat tendon lengthening with good success.^13,14,18 Tendon lengthening also helps heal transmetatarsal amputations and arterial forefoot wounds.^7,27-35 In the few cases in which tendon balancing fails, one can subsequently perform bony procedures. General contraindications to Achilles lengthening and gastrocnemius-soleus recession are plantar heel ulcers, extensive necrosis and/or infection that necessitates amputation of the entire foot.

Patients with diabetes have a higher complication rate with foot and ankle surgery.³⁶ Tendon lengthening has an advantage over most other surgeries for foot pain from Achilles tendinitis, plantar fasciitis, midfoot arthritis and metatarsalgia in patients with diabetes since tendon lengthening has a low complication rate, and can also prevent foot ulcers from developing in the future.^3,16,18-21 Belatti and Phisitkul noted a 47 percent decrease in major amputations in Medicare patients with diabetic foot ulcers between 2000 and 2010.³⁷ In the same period, the use of Achilles tendon lengthening increased 89 percent and gastrocnemius recession increased 575 percent. These authors felt the major cause of the decrease in major amputations was the increase in tendon lengthening.

Cychosz and colleagues recently performed a literature review on diabetic foot ulcer treatment and gave the highest recommendation (supported by strong evidence) to tendon lengthening.³⁸ They gave the same recommendation to footwear modification, total contact casting and advanced biological therapy.

Most of the literature on treatment of diabetic foot problems consists of case series and personal opinion. Levels of evidence for tendon lengthening for ulcers plantar to metatarsal head are the best: levels I, III and IV.^{2,6,8,10,12,13,15,18} There is lower level evidence when it comes to tendon lengthening for plantar ulcers on the toes and the distal end of transmetatarsal amputation stumps.^{7,12,14,17-19} Available evidence seems to indicate that tendon lengthening is the most effective treatment for diabetic forefoot ulcers with the fewest complications.

Final Thoughts

Surgeons may combine tendon lengthening with other modalities but should perform lengthening as soon as possible to promote rapid healing before the ulcer gets infected, and to better prevent recurrence, transfer ulcers and amputation.

Dr. Laborde is an orthopaedic surgeon at Touro Infirmary in New Orleans. He is a Clinical Assistant Professor of Orthopaedic Surgery at the Tulane University School of Medicine at Louisiana State University Health Sciences Center (LSUHSC) in New Orleans, and is the Director of the Foot Clinic at LSUHSC.

References

1. Rosenbloom AL, Silverstein JH. Connective tissue and joint disease in diabetes mellitus. Endocrinol Metab Clin N Am. 1996;25(2):473-83.
2. Lin SS, Lee H, Wapner KL. Plantar forefoot ulceration with equinus deformity of the ankle in diabetic patients; the effect of tendo-Achilles lengthening and total contact casting. Orthopaedics. 1996;19(5):465-474. 29.  
3. Armstrong DG, Shea SS, 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. 1999;81-A(4):535-8.
4. Lavery LA. Ankle equinus deformity and its relationship to high plantar pressure in a large population with diabetes mellitus. J Am Pod Med Assoc. 2002;92(9):479-832.
5. Pecoraro RE, Reiber GE, Burgess EM. Pathways to diabetic limb amputation. Diabetes Care. 1990;13(5):213-21.
6. Yosipovitch Z, Sheskin J. Subcutaneous Achilles tenotomy in the treatment of perforating ulcer of the foot in leprosy. Int J Leprosy Other Mycobat Dis. 1971;39(2):631-632.
7. Barry DC, Sabacinski KA, Habershaw GM, Giurin JM, Chrzan JS. Tendo-Achilles procedure for chronic ulceration in diabetic patients with transmetatarsal amputations. J Am Pod Med Assoc.1993;83(2):96-100.
8. Mueller MJ, Sinacore DR, Hastings MK, Strube MJ, Johnson JE. Effect of Achilles tendon lengthening on neuropathic plantar ulcers, a randomized clinical trial. J Bone Joint Surg. 2003;85A(8):1436-1445.
9. Nishimoto GS, Attinger CE, Cooper PS. Lengthening the Achilles tendon for the treatment of diabetic plantar forefoot ulceration. Surg Clin N Am. 2003;83(3):707-726.
10. Holstein P, Lohman M, Birtsch M, Jorgensen B. Achilles tendon lengthening, the panacea for plantar forefoot ulcers? Diab Met Res Rev. 2004; 20(S1):S37-40.
11. Strauss MB. The orthopaedic surgeon’s role in the treatment and prevention of diabetic foot wounds. Foot Ankle Int. 2005;26(1):5-14.
12. Laborde JM. Tendon lengthening for forefoot ulcers. Wounds. 2005;17(5):122-130.     
13. Laborde JM. Neuropathic plantar forefoot ulcers treated with tendon lengthening. Foot Ankle Int. 2008;29(4):378-384.
14. Laborde JM. Neuropathic toe ulcers treated with flexor tenotomies. Foot Ankle Int. 2007;28(11):1160-64.
15. Dayer R, Assal M. Chronic diabetic ulcers under the first metatarsal head treated by staged tendon balancing. J Bone Joint Surg. 2009;91B(4):487-493.
16. Laborde JM. Tendon lengthening for neuropathic foot problems. Orthopedics. 2010;33(5):319-26.
17. KearneyTP, Hunt NA, Lavery LA. Safety and effectiveness of flexor tenotomies to heal toe ulcers in persons with diabetes. Diabetes Res Clin Pract. 2010;89(3):224-6.  
18. Laborde JM. What a new study reveals about tendon lengthening for diabetic foot ulcers. Podiatry Today. Available at https://www.podiatrytoday.com/what-new-study-reveals-about-tendon-lengthening-diabetic-plantar-foot-ulcers . Published Nov. 1, 2012.
19. Van Netten JJ, Price PE, Lavery LA, et al. Prevention of foot ulcers in the at-risk patient with diabetes: a systematic review. Diabetes Metab Res Rev. 2016;32(Suppl. 1):84-98.
20. Rush SM, Ford LA, Hamilton GA. Morbidity associated with high gastrocnemius recession. J Foot Ankle Surg. 2006;45(3):156-160.
21. Takahashi S, Shrestha A. The Vulpius procedure for correction of equinus deformity in patients with hemiplegia. J Bone Joint Surg. 2002;84B(7):978-980.
22. Weiman TJ, Mercke YK, Cerrito PB, Taber SW. Resection of the metatarsal head for diabetic foot ulcers. Am J Surg. 1998;176(5):436-441.
23. Fleischli JE, Anderson RB, Davis WH: Dorsiflexion metatarsal osteotomy for treatment of recalcitrant diabetic neuropathic ulcers. Foot Ankle Int. 1999;20(2):80-85.
24. Margolis DJ, Kantor J, Berlin JA. Healing of diabetic neuropathic foot ulcers receiving standard treatment. Diabetes Care. 1999;22(5):692-5.
25. Saltzman CL, Zimmerman MB, Holdsworth RL, Beck S, Hartsell HD, Frantz RA. Effect of weight-bearing in a total contact cast on healing of diabetic foot ulcers. J Bone Joint Surg. 2004;86A(12):2714-19.
26. Guyton GP. An analysis of iatrogenic complications of total contact cast. Foot Ankle Int. 2005;26(11):903-7.
27. Claxton MJ, Armstrong DG. Addressing tendon balancing concerns in diabetic patients. Podiatry Today. 2003;16(3):63-70.
28. Lafontaine J, Brown D, Adams M, VanPelt. New and recurrent ulcerations after percutaneous Achilles tendon lengthening in transmetarsal amputation. J Foot Ankle Surg. 2008;47(3):225-229.
29. Roukis TS. Flexor hallucis longus and extensor digitorum longus tendon transfers for balancing the foot following transmetatarsal amputation. J Foot Ankle Surg. 2009;48(3)398-401.
30. 30. Schade VL. Key insights on adjunctive procedures with transmetatarsal amputations. Podiatry Today. 2011; 24(3):22-28.
31. Pinzur M, Kaminisky M, Sage R, Cronin R, Osterman H. Amputations at the middle of the foot. J Bone Joint Surg. 1998;68A(7):1061-4.
32. Sage R, Pinzur MS, Cronin R, Preuss HF, Osterman H. Comlications following midfoot amputation in neuropathic and dysvascular feet. J Am Pod Med Assoc. 1989;79(6):277-280.
33. Lieberman JR, Jacobs RL, Goldstock L, Durham J, Fuchs MD. Chopart amputation with percutaneous heel cord lengthening. Clin Orthop Rel Res. 1993;296(11):86-91.
34. Clark GD, Lui E, Cook KD.Tendon balancing in pedal amputations. Clin Pod Med Surg. 2005;22:447-67.
35. Shirzad K. Lesser toe deformities. JAAOS. 2011;19(8):505-13.
36. Myers TG, Lowery NJ, Frykberg, Wukish DK. Ankle and hindfoot fusions: comparison of outcomes in patients with and without diabetes. Foot Ankle Int. 2012;33(1):20-28.
37. Belatti DA, Phisitkul P. Declines in lower extremity amputation in the Medicare population, 200-2010. Foot Ankle Int. 213;34(7):923-31.
38. Cychosz CC, Phisitkul P, Belatti DA, Wukich DK. Preventive and therapeutic strategies for diabetic foot ulcers. Foot Ankle Int. 2016;37(3):334-43.

Editor’s note: For further reading, see “Is Tendon Lengthening The Best Treatment For Diabetic Foot Ulcers?” in the May 2012 issue of Podiatry Today or “Addressing Tendon Balancing Concerns In Diabetic Patients” in the March 2003 issue.  

No.

Citing various surgical risks, this author argues Achilles tendon lengthening is not part of the standard of care for plantar forefoot ulcers in patients with diabetes.  

By Richard D. Weiner, DPM

A second-year resident recently presented to me a 61-year-old non-insulin dependent obese female with diabetes and multiple comorbidities including radiographic findings of sclerosis of pedal arteries. She had a full-thickness ulceration underlying her second metatarsophalangeal joint (MPJ), which had failed to respond to conservative wound care efforts over the previous five weeks. This is a well-read resident who cites articles by Attinger, Armstrong, Tagoe, Mueller and numerous others as evidence supporting the need to add this patient onto the surgery schedule to perform a formal debridement with the addition of a tendo-Achilles lengthening in an effort to relieve the plantar pressure to her forefoot ulcer.

As peak foot pressures increase, so does the likelihood of ulcerations.¹ In response to the resident’s proposed plan, I ask, “Would it be appropriate for me to perform this surgery? Diabetic plantar foot ulcerations are multifactorial and involve a combination of comorbidities that are not easily attributed to a single cause.”  The resident replies that an Achilles tendon lengthening is appropriate because this patient with diabetes has had non-enzymatic collagen glycosylation in her Achilles tendon and has equinus. The resident then emailed me links to numerous articles concluding that to heal diabetic plantar forefoot ulcerations, an Achilles tendon lengthening is appropriate.

I do not disagree with the findings of the numerous articles on the topic of tendo-Achilles lengthening but I do question how to interpret the findings from studies involving relatively small quantities of patients.^2-11 Perhaps more importantly, I question how best to incorporate these findings into our everyday standard of patient care.

A Closer Look At The Risks Of Achilles Tendon Lengthening

Prior to 15 years ago when these articles started appearing, how did podiatrists successfully treat patients with plantar diabetic foot ulcerations? For those recent graduates, the answer is, quite successfully and without performing Achilles tendon lengthening.

Many physicians argue that a percutaneous Achilles tendon lengthening is among the easiest of surgical procedures to perform and due to its simplicity, it should be a first line of treatment. However, there are implicit risks with patients with diabetes that we must consider in pursuing any surgical procedures. In addition to the increased potential healing issues in this patient population, there is also the all too common dilemma of non-adherence with postoperative protocols, whether intentional or otherwise.

I do not believe it is standard of care for every patient with diabetes with an equinus deformity and an associated forefoot ulceration to have an Achilles tendon lengthening. For new practitioners whom we have taught that standard of care revolves around evidence-based medicine, we must recognize that it is our responsibility to assimilate evidence-based medicine and clinical guidelines, but also couple this with outcome-based results.

Wound care treatment follows the same dichotomy as any other treatment plan. Appropriately diagnose and address the etiologies of the wound. Consider a team-oriented approach and make efforts to treat local or systemic infection, address vascular impairment and corresponding orthopedic deformity, evaluate nutritional status or other systemic deficiencies, provide local wound care and offload the wound. With this approach, a majority of diabetic wounds have the potential to heal without an Achilles tendon lengthening.^1,12-16  

Some authors have discussed an Achilles tendon lengthening as a prophylactic treatment in patients with diabetes to prevent plantar ulcerations.¹⁷ How far are we prepared to go? There will always be those patients who do not readily respond to treatment as successfully as the majority of our patients do and for that small subset of patients, perhaps an Achilles tendon lengthening is appropriate if in fact an equinus deformity is present and a contributing factor.

Performing surgery on a patient with diabetic neuropathy and a non-healing wound unresponsive to conservative care has numerous risks. Surgery on this class of patients is in no way benign.^{1,15,16,18,19} To read the well-written literature and conclude every patient with diabetes with a plantar ulceration and equinus is a candidate to undergo an Achilles tendon lengthening procedure is unfortunate, and will likely lead to an increase in unnecessary postoperative complications. These complications may include anaphylaxis to anesthetic agents, cardiovascular collapse, respiratory depression, aspiration pneumonitis, hypoxic brain damage, infection, nerve damage, further wound healing complications, venous thrombosis or pulmonary embolism.

There is also the risk of overcorrection of the equinus deformity, which can lead to a calcaneal gait and the formation of another significantly more complicated rearfoot ulceration. Not to mention there is a risk of under-correction, leading to complicated revisional surgery or the possibility of an Achilles tendon rupture leading to severe loss of strength, loss of function and permanent long-term bracing.^2,3

La Fontaine and colleagues reported on a series of 28 patients who had an Achilles tendon lengthening for treatment of diabetic plantar ulcerations.¹⁹ Five patients developed plantar central heel ulcerations due to iatrogenic over-lengthening. Hoefnagels and colleagues found that one-third of their triple hemisections of cadaveric Achilles tendon resulted in failure.¹¹ They either had insufficient or complete tenotomies. Salisch and coworkers reported that an Achilles tendon lengthening procedure achieved a 37 percent reduction of plantar forefoot torque but at eight months, torque had normalized, making the relief of plantar pressure transient.³

What Is The Standard Of Care For Plantar Forefoot Ulcers?

How are physicians who treat wounds to decide how to incorporate the results of these studies into our practices? There are many physicians who treat wounds who do not perform Achilles tendon lengthening regardless if it is a privileging or philosophical issue. If one concludes that an Achilles tendon lengthening is appropriate treatment for plantar forefoot ulcerations in patients with diabetes, are those practitioners who do not perform this procedure treating below the standard of care? Should the patients of those who do not perform Achilles tendon lengthening get referrals to practitioners who do?

I do not believe that to be the case. Numerous respected authors who have published their results of successfully healing patients with diabetes with plantar ulcerations by an Achilles tendon lengthening should be commended for their efforts, their dedication and their results. It is incumbent upon the community of providers who treat these patients to determine the standard of care. The most important component should be the individual practitioner’s outcomes.

It is not mandatory to perform an Achilles tendon lengthening on every patient with diabetes with a forefoot plantar ulceration and equinus in an effort to heal the wound. There are many other successful nonsurgical options to offload the plantar foot that carry significant less risk and less morbidity with decades of documented success. These include total contact casting (“the gold standard”), offloading with custom inserts and/or shoes, hyperbaric oxygen therapy, negative pressure wound therapy, bracing/ankle-foot orthotics and even skin substitution products.

Conservative care cannot faithfully heal every diabetic plantar forefoot ulceration in which an equinus deformity is a contributing factor. How does the individual practitioner take the volume of viable information available and form a reasonable treatment paradigm that minimizes risk to both patient and practitioner, and ultimately yields a successful outcome? How does a practitioner without access to reliable means of gait analysis and measurement of plantar foot pressures make the decision that an equinus is the major contributing factor toward the wound’s development? The modern practitioner must be capable of identifying when traditional accommodation is warranted but must also recognize when surgical intervention is indicated. The practitioner must prioritize individualized patient care and determine the underlying multifactorial etiologies of each ulceration to maximize the patient’s potential to heal.

Surgeons should not consider the definitive standard of care to be performing an Achilles tendon lengthening on a patient with diabetes and a plantar forefoot ulceration. Surgeons should rather regard tendon lengthening as another valuable tool to have in the individual treatment algorithm.

Dr. Weiner is a Clinical Professor of Podiatry in the Department of Specialty Medicine at the Ohio University Heritage College of Osteopathic Medicine in Athens, Ohio. He is a Clinical Assistant Professor in the Department of Orthopedics, Division Foot and Ankle Surgery at Ohio State University in Columbus, Ohio. Dr. Weiner is in private practice at Step Lively Foot & Ankle Centers in Columbus.

References

1. Singh N, Armstrong DG, Lipsky BA. Preventing foot ulcers in patients with diabetes. J Am Med Assoc. 2005; 293(2):217–228
2. Tagoe MT, Reeves ND, Bowling FL. Is there still a place for achilles tendon lengthening? Diabetes Metab Res Rev. 2016; 32(Suppl 1):227¬–231.
3. Salsich GB, Mueller MJ, Hastings MK. Effect of Achilles tendon lengthening on ankle muscle performance in people with diabetes mellitus and a neuropathic plantar ulcer. Physical Therapy. 2005; 85(1):34–43.
4. Mueller MJ, Sinacore DR, Hastings MK. Effect of Achilles tendon lengthening on neuropathic plantar ulcers. J Bone Joint Surg Am. 2003; 85-A(8):1436–45.
5. Barry DC, Sabacinski KA, Habershaw GM, Giurini JM, Chrzan JS. Tendo Achilles procedures for chronic ulcerations in diabetic patients with transmetatarsal amputations. J Am Podiatr Med Assoc. 1993; 83(2):96–100.
6. Armstrong DG, Peters EJG, Athanasiou KA. Is there a critical level of plantar foot pressure to identify patients at risk for neuropathic foot ulceration? J Foot Ankle Surg. 1998; 37(4):303–7.  
7. Armstrong DG, Stacpoole-Shea S, Nguyen H. Lengthening of the Achilles tendon in diabetic patients who are at high risk for ulceration of the foot. J Bone Joint Surg. 1999; 81(4):535–8.
8. Willrich A, Angirasa AK, Sage RA. Percutaneous tendo Achilles lengthening to promote healing of diabetic plantar foot ulceration. J Am Podiatr Med Assoc. 2005; 95(3):281–4.
9. Weiner RD, Hlad LM, McKenna DR. Recurrence of diabetic pedal ulcerations following tendo-Achilles lengthening. Diabetic Foot Ankle. 2011; epub May 11.
10. Colen LB, Kim CJ, Grant WP. Achilles tendon lengthening: friend or foe in the diabetic foot? Plast Reconstr Surg. 2013; 131(1):37e–43e.
11. Hoefnagels EM, Waites MD, Belkoff SM, Swierstra BA. Percutaneous Achilles tendon lengthening: a cadaver-based study of failure of the triple hemisection technique. Acta Orthop. 2007;78(6):808-12.
12. International Working Group on the Diabetic Foot: International Consensus on the Diabetic Foot. Available at www.iwgdf.org .
13. Jeffcoate WJ, Ince P, Chipchase SY, Game FL. Assessing the outcome of the management of diabetic foot ulcers using ulcer-related and person-related measures. Diabetes Care. 2006; 29(8):1784–7.  
14. Van Gils CC, Roeder B. The effect of ankle equinus upon the diabetic foot. Clin Podiatr Med Surg. 2002; 19(3):391–409.
15. Apelqvist JA, Elgzyri T, Larsson J. Factors related to outcome of neuroischemic/ischemic foot ulcer in diabetic patients. J Vasc Surg. 2011; 53(6):1582–8.  
16. Prompers L, Schaper N, Apelqvist J, et al. Prediction of outcome in individuals with diabetic foot ulcers: focus on the differences between individuals with and without peripheral arterial disease. The EURODIALE Study. Diabetologia. 2008; 51(5):747–755.
17. Armstrong DG, Stern S, Lavery LA, Harkless LB. Is prophylactic diabetic foot surgery dangerous? J Foot Ankle Surg. 1996; 35(6):585–9.
18. Brechow A, Slesaczeck, Munch D. Improving major amputation rates in the multicomplex diabetic foot patient: focus on the severity of peripheral arterial disease. Ther Adv Endocrinol Metab. 2013; 4(3):83–94.
19. La Fontaine J, Brown D, Adams M. New and recurrent ulcerations after percutaneous Achilles tendon lengthening in transmetatarsal amputation. J Foot Ankle Surg. 2008; 47(3):225–9.