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Achilles Tendon Lengthening to Prevent Recurrent and Late Forefoot Ulcers After Transmetatarsal Amputation
There are few foot and ankle surgical procedures supported by level I evidence. One procedure supported by a level I study is Achilles tendon lengthening (ATL) to prevent recurrent forefoot ulcers. In a randomized controlled trial, Mueller and colleagues found a 38% recurrence rate with ATL compared to an 81% recurrence rate using total contact casting (TCC) without ATL at a 2-year follow-up.1 In 2010, Wukich noted that ATL is the only prophylactic surgery for foot ulcers supported by Grade A (strong evidence).2 Despite the Grade A recommendation and the large effect size reported, we observe that the frequency with which ATL is employed for surgical offloading of diabetic foot ulcers varies among foot and ankle providers.
An often-cited concern with ATL in patients with neuropathy is overlengthening of the Achilles tendon, which can cause plantar heel ulcers, which could go on to partial calcanectomy or major lower extremity amputation as a sequelae. Plantar heel ulcers have been successfully managed with flexor hallucis longus (FHL) transfer in one case series.3
Many studies show a high incidence of plantar heel ulcers when ATL is used to prevent recurrent forefoot ulcers. A closer look at the literature shows the studies that illustrated this risk primarily allowed immediate weight-bearing. We identified 4 studies that allowed immediate weight-bearing and the total incidence of plantar heel ulcerations was 15% (24/165).1,4-6 We identified 3 studies that had an initial period of strict non-weight-bearing for 3–4 weeks, followed by an additional 4 weeks ambulating in a fracture boot or TCC. With the delayed weight-bearing and immobilization protocol there was a 1.5% (3/192) incidence of plantar heels ulcers.7-9
Gastrocnemius recession demonstrates a lower risk of plantar heel ulcers, but provides less correction compared to Achilles tendon lengthening. While recent studies appear to show benefit to performing gastrocnemius recession, many of the studies use gastrocnemius recession as an adjunct with tendon transfers, bone resection or reports relate to midfoot instead of forefoot ulcers.10-13 For these reasons, the true efficacy of gastrocnemius recession to prevent recurrent neuropathic forefoot ulcers is not well established.
Using ATL to Prevent Recurrent Forefoot Ulcers in the Authors’ Practice
When evaluating a neuropathic patient for ATL to treat forefoot ulcers under the metatarsals, it is important to discuss their support system and ability to remain non-weight-bearing. For patients with diabetes and an equinus contracture who have an ability to remain non-weight-bearing, we consider Achilles tendon lengthening early in the course of treatment. Patients are also offered physical therapy preoperatively to determine if they can safely remain non-weight-bearing. Patients are advised after the first 4 weeks of non-weight-bearing in a below-knee cast they will transition into a fracture boot or a below-knee walking cast dependent on ulcer healing. In our experience, this treatment protocol has quickly healed recalcitrant forefoot ulcers that have failed multiple treatment modalities for years.
Evidence for ATL to Prevent Late Forefoot Ulcers After Transmetatarsal Amputations
Foot and ankle providers often see plantar forefoot ulcers after transmetatarsal amputation. We define late forefoot ulcers as plantar forefoot ulcers that occur after initial incision healing with a biomechanical etiology. In 1989, Sage and colleagues noted a high incidence of late ulceration within the first year in patients who did not have early wound failure after TMA.14 Recently it was reported that TMAs have a 44% failure rate due to late ulceration with a mean time to ulceration of 15 months.15
Clinicians that perform TMA often perform concomitant ATL to prevent late ulcerations, but this varies greatly by location, and until recently there was no evidence to support its use. Our retrospective study was recently published showing a large patient cohort where TMA was performed with or without ATL.9 After excluding patients with less than 120 days’ follow-up, we found a 35% (n = 55) incidence of late ulceration in patients without ATL and a 3% (n = 30) incidence of late ulceration in patients with ATL with similar mean follow-up times and no confounding variables between the two groups. Mean time to ulcer development was 587 days. Younger patients were significantly more likely to develop late forefoot ulceration (P = .006).
Similar to Colen and colleagues. we noted a low incidence of plantar heel ulceration when ATL was performed in neuropathic patients to prevent ulceration (3%). Our protocol included 4 weeks of non-weight-bearing in either a posterior splint or a short leg cast followed by 4 additional weeks in a high tide fracture boot. In some instances, a heel lift was utilized inside the fracture boot. We also allowed a slow and gradual increase in passive ankle dorsiflexion stretching, usually starting 10 weeks after surgery.
ATL to Prevent Late Forefoot Ulcers After Transmetatarsal Amputations in the Authors’ Practice
In our practice, we include ATL with most of the transmetatarsal amputations (TMAs) we perform. When we did not perform ATL, we saw many instances of severe equinus deformity and new neuropathic forefoot ulceration more than a year postop from TMA (Figure 1). Performing a TMA creates a tendon imbalance that favors plantarflexors since the digital extensors are responsible for a greater contribution to ankle dorsiflexion compared with the lost contribution of digital flexors to ankle plantarflexion. Attempts to perform ATL after severe equinus and neuropathic ulceration have been less successful in our practice with 3 instances of recurrence.
We perform ATL with wounds kept covered in the stockinette prior to the TMA. We create triple transverse hemisections with a 15-blade, spaced 2.5 cm apart (Figure 2). The ankle is passively dorsiflexed until a release is felt, and further fibers can be released if needed. We prefer to slightly overcorrect and obtain close to 10 degrees of passive ankle dorsiflexion. Adherence with postoperative protocol is critical. We have seen overlengthening when patients weight-bear in their splint or walk short distances without their controlled ankle motion (CAM) boot. Both of these problems have been successfully treated with increased duration of immobilization if caught early. Patient education is key to avoid complications.
While we perform an ATL in the majority of TMAs, we do note relative contraindications including: inability to remain non-weight-bearing after surgery, concern for non-adherence with postoperative protocol, lymphedema and increased passive ankle joint dorsiflexion before surgery. We are also less likely to perform ATL in older patients with lower activity levels. Typically, we perform dressing changes through the posterior splint for the first week and then evaluate the wound weekly with cast changes. If a very extensive surgical wound is created that involves the plantar flap, we consider initial non-weight-bearing in a high fracture boot or staging the ATL procedure so we can perform regular dressing changes in the first week. (Figure 3)
In Conclusion
Current evidence supports the use of ATL to prevent recurrent forefoot ulcers and also late forefoot ulcers after transmetatarsal amputation. Current evidence only favors the use of ATL to prevent forefoot ulcers when non-weight-bearing and prolonged immobilization are instituted postoperatively. Additional studies are needed to define the efficacy of gastrocnemius recession for these uses.
Dr. Bullock practices at Covenant Orthopaedics. He is a Fellow of the American College of Foot and Ankle Surgeons. Dr. Bullock is faculty for the Central Michigan University Residency program and AO North America.
Dr. Hamawi is a third-year podiatric resident at Central Michigan University in Saginaw, MI.
Dr. Gill practices at Midland Podiatry Associates in Midland, MI.
References
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