Yes. Although the transmetarsal amputation has important indications in limb salvage, these authors note significant re-operation, re-amputation and morbidity rates, and point to a variety of alternative procedures for salvaging the forefoot.
By Casey Lewis, DPM, John Martucci, DPM and Barry I. Rosenblum, DPM, FACFAS
The transmetatarsal amputation (TMA) has been a longstanding, reasonable option for patients whose extremities are compromised by infection and/or necrosis, and often results in a functionally and structurally sound foot. Numerous authors have described favorable outcomes for this procedure, especially in patients with diabetes complicated by either peripheral neuropathy, peripheral arterial disease or both.1 However, surgeons may be utilizing the TMA more frequently than necessary.
Historically, researchers have described the TMA as a salvage procedure. McKittrick and coworkers originally discussed the procedure as an alternative to the below-knee amputation in patients with diabetes.2 Employing the TMA frequently for patients with infections, severe arterial insufficiency and gangrene as well as those with peripheral neuropathy, McKittrick and colleagues noted gratifying results for this group of patients.2
While the TMA does have important indications, there are two primary viewpoints that support the notion that this procedure is overutilized today. First, TMAs are not without complications and secondly, there is a variety of successful alternative procedures that preserve the forefoot.
Considering Complications And Outcomes With The TMA
First, despite advances in the management of critical limb-threatening ischemia (CLTI), the complication rate and morbidity following TMAs are not insignificant. Like most amputations, TMAs do carry a significant morbidity rate.3 A patient may ultimately require a more proximal amputation due to vascular status. While most patients and providers certainly prefer to avoid a more proximal amputation (e.g. a transtibial, below-knee or above-knee amputation), there are cases in which there is predictable failure with the more distal TMA.1,3,4,5 In order to avoid the risks of unnecessary surgeries and prolonged hospitalizations, one must conduct honest discussions with patients and family regarding the true healing potential of a TMA.
In a retrospective study of 101 TMAs, Pollard and colleagues noted post-op complications in over 87 percent of the cases, and found that 57.4 percent of patients achieved a healed stump.3 The study authors suggested that TMA is associated with high complication rates in a diabetic and vasculopathic population. The strongest correlations for an increased risk of postoperative complications after TMA were nonpalpable pedal pulses or end-stage renal disease.
Thorud and coworkers performed a systematic review and meta-analysis looking at re-operation and re-amputation after TMA.1 They noted a re-operation rate of 24.43 percent, a re-amputation rate of 28.37 percent and a major amputation rate, defined as a more proximal amputation, of 30.16 percent. Yet they concluded that additional research was necessary to identify reliable predictors of re-operation and re-amputation in an effort to assist surgeons in selection of the appropriate amputation level resulting in reliable outcomes.1
Landry and colleagues noted that TMA is a suboptimal option because of its low healing rate and recommend that surgeons avoid this procedure in cases in which ambulation is clearly not a reasonable future goal.6 Ammendola and team went so far as to limit offering TMA to only those patients with favorable prospects for postoperative ambulation.7
Evaluating The Viability Of Alternatives To TMA
Secondly, in situations with a predictable failure of a TMA, there are alternative procedures that aim to salvage as much of the foot as possible. This is especially true in cases in which the team has either successfully addressed significant arterial insufficiency or is unable to further improve circulation. Patients may benefit from a more limited amputation along with meticulous wound care and close outpatient follow-up. Additionally, some patients may benefit from a procedure aimed at preserving the forefoot in order to maintain the integrity of the skin and soft tissue envelope and a more normal gait. In fact, there are currently many procedures that surgeons can perform that salvage the forefoot and result in a foot that is more structurally and functionally sound than a TMA.
Our group at Beth Israel Deaconess Medical Center published a review of patients presenting with forefoot ulcers secondary to diabetic neuropathy in the setting of severe arterial insufficiency.8 In this series, we performed metatarsal osteotomies or resections in lieu of a TMA to salvage the forefoot. None of the studied patients lost any part of the foot. Revascularization was solely open bypass in this cohort as the study predated the use of endovascular procedures with any degree of regularity. These findings support the opinion that once a patient’s vascular status is optimized or can no longer be improved upon, conservative metatarsal osteotomies do present a viable alternative to the TMA in the right setting.
Metatarsal head resection is by no means a new concept. Various authors describe the use of the pan metatarsal head resection as an alternative to the TMA.9,10 In a series studied at our institution, primary healing was 94 percent and the overall success rate was 97 percent after a pan metatarsal head resection. Of note, with almost two years of follow-up, no patient required further amputation of any kind. By successfully maintaining the structural and functional integrity of the forefoot in select patients, metatarsal head resection is a reasonable alternative to the TMA.
Other authors describe the pan metatarsal head resection as a viable alternative to the TMA as well. Armstrong and colleagues described successful outcomes of the pan metatarsal head resection in patients with diabetes and neuropathic wounds.10 His group compared surgical excision of multiple metatarsal heads to standard offloading and wound care. The surgery group healed significantly faster than the standard therapy group and had fewer recurrent ulcers and infections during one year of follow-up. Their results suggested that the pan metatarsal head resection may be associated with shorter times to healing and lower morbidity in comparison to standard wound care alone in patients with multiple forefoot ulcers.
Suh and team reported their approach in a retrospective series that evaluated first ray- or first and second ray-preserving procedures with complete transmetatarsal amputation and free flap reconstruction.11 Despite the two groups having somewhat different soft tissue reconstructions (anterolateral thigh flap predominantly in the TMA group while superficial circumflex artery flap was most frequent in the ray preservation group), the flap failure rate was similar in both groups as was the high rate of partial flap loss, which was not statistically significant. They concluded that despite the higher tendency of minor procedures following ray preservation, preservation of the first or first two rays may ultimately benefit patients and lead to a more functional outcome than a TMA.11
In review, the TMA is often a viable surgical option with predictable outcomes. In the properly selected patient, healing should proceed uneventfully. However, when it comes to patients for whom there is an expectation of a complicated healing process, the TMA may be overutilized. These patients may exhibit more optimal results with a more proximal amputation. However, in addition to these considerations, there is a subset of patients who may benefit from alternatives to the TMA, such as pan metatarsal head resection or procedures designed to salvage the first or first two rays. As foot and ankle surgeons involved with complex limb salvage efforts, we should recognize when a procedure, such as a TMA, may be a suboptimal option and weigh other surgical alternatives to achieve the most successful and functional outcomes for our patients.
Dr. Lewis is a second-year Podiatric Medicine and Surgery resident at Beth Israel Deaconess Medical Center in Boston.
Dr. Martucci is a second-year Podiatric Medicine and Surgery resident at Beth Israel Deaconess Medical Center in Boston.
Dr. Rosenblum is an Assistant Clinical Professor of Surgery at Harvard Medical School in Boston. He is board-certified in foot surgery by the American Board of Foot and Ankle Surgery.
No. When surgeons ensure appropriate patient selection, preoperative evaluation and post-op management, these authors emphasize that the TMA offers more durable outcomes in contrast to more distal level procedures that are prone to subsequent ulceration and re-amputation.
By Andrew S. Au, DPM, Ashley A. Bruno, DPM and Peter A. Blume, DPM, FACFAS
The transmetatarsal amputation (TMA) is not an overutilized procedure in patients with diabetes. In fact, it is the preferred biomechanical level of amputation in many cases. Patients may also be more apt to explore limb salvage procedures at the transmetatarsal level prior to a major amputation. In comparison to Lisfranc and Chopart amputations, the TMA provides a functional end-bearing limb with durable plantar flap coverage. Patients can wear custom molded shoes fitted with toe fillers and orthoses.1 When one juxtaposes the TMA against major transtibial and transfemoral amputations, there is a considerably lower energy cost of walking as well as lower mortality rates.2-4
In 1949, McKittrick utilized the TMA to manage infection and gangrene in patients with diabetes.5 Today, the indications include but are not limited to chronic forefoot ulceration, digital ischemia, failed distal amputation, and trauma. Patients with distal neuropathic wounds and abscesses may benefit the most from a procedure, such as a TMA, that does not cause imbalance to the remaining foot. One can reconstruct the metatarsal parabola at varying metatarsal lengths to salvage as much of the viable foot as possible. This is an extremely important consideration in favor of the TMA since an abnormality of the metatarsal parabola via isolated ray amputations may lead to recurrent forefoot ulceration and infection.6
Transmetatarsal amputations with proper tendon balancing are an underutilized combination. The surgeon must direct close attention to the inherent biomechanical alterations that affect the residual foot. Restoration of anatomical alignment is critical for healing and ulcer prevention after a TMA and achievement of source control. Percutaneous tendo-Achilles lengthening or gastrocnemius recession can correct ankle equinus due to imbalance of the anterior muscle compartment. One can address deforming varus forces with intramedullary screw fixation, a peroneus brevis-to-longus tendon transfer, a split anterior tibial tendon transfer or a flexor hallucis longus and extensor digitorum longus tendon transfer.7-9
What The Literature Reveals About Alternatives To TMA
The risks of performing a distal amputation in place of a TMA for patients with chronic neuropathic ulcerations or infection are recurrence and the possible need for additional amputation. The pitfalls of isolated ray amputations involve deformity-induced transfer ulcerations that lead to osteomyelitis of the adjacent metatarsals.
Armstrong and Lavery conducted a comparison study looking at peak plantar pressures in patients with diabetes who had a digit or ray amputation.10 The peak plantar pressures were significantly higher for these patients in comparison to controls. Forefoot amputees were up to 10 times more likely to present with joint deformity and limitations. The authors noted that considerable biomechanical changes following a digit or ray amputation placed an already high-risk limb at further risk for tissue breakdown and amputation.10
In a retrospective study evaluating the outcomes of preserving the first ray or first two rays in comparison to a TMA, Suh and colleagues found that preservation of the medial rays will eventually give way to deforming forces and require further surgery.11 Additionally, Borkosky and Roukis in 2013 found that despite initial healing, 69 percent of patients with diabetes and peripheral neuropathy who had an initial partial first ray amputation developed three subsequent foot ulcerations on average.12 Ultimately, 42 percent of patients in this study required more proximal repeat amputation. Other study authors report success rates of solitary ray resections that range between 31 and 37 percent.13-15 In a systematic review of 435 partial first ray amputations, Borkosky and Roukis noted the incidence of re-amputation was approximately 20 percent.16
Emphasizing The Importance Of Perioperative Evaluation And Planning
A well-balanced TMA may be indicated as the index amputation in patients with diabetes and peripheral sensory neuropathy as it may be more beneficial to the patient than distal and isolated ray amputations.16 The primary goals of deciding on a level of amputation is to achieve source control, healing vascularity and a stable, plantigrade foot that will never require additional amputation. Thus, one must take thoughtful planning and preoperative selection criteria into account.
Patient screening for healing impairments at the amputation level is crucial. An ankle brachial index (ABI) greater than 0.7 and a serum albumin level greater than 30 g/l are significant factors affecting wound healing success.17 Glycemic control as measured by hemoglobin A1c (HbA1c) is also an important factor affecting TMA outcomes. Aggressive control can limit sensory decline and reduce the incidence of ulceration, infection and additional amputation. A HbA1c level less than seven percent is optimal.18,19
Transmetatarsal amputations require appropriate preoperative evaluation and postoperative management. Meticulous operative technique is vital for every surgical procedure. The judgement of an experienced surgeon may be one of the more reliable indicators for postoperative healing. However, careful consideration of glycemic control and vascular status are essential prior to performing a TMA. In a systematic review by Musuuza and colleagues, initiation of multidisciplinary teams addressing glycemic control, local wound management, vascular disease, and infection in the treatment among patients with diabetic foot ulcers reduced major amputations in 94 percent of studies.20 A multidisciplinary team that appropriately practices standardized diabetic foot guidelines will facilitate a successful operation, excellent postoperative care and continued wound prevention. The TMA is a powerful limb salvage procedure and should be an alternative or principal procedure in patients requiring distal level amputations.
In conclusion, TMAs are underutilized because of the availability to amputate at varying distal levels such as digits and rays. It is important to recognize the load transfers that result from these alternative digital and ray amputations, and consider the durability and proper alignment that the TMA affords. The TMA is also underutilized because of the added complexity of performing adjunctive tendon balancing procedures. These procedures, however, are necessary to allow the patient a full potential for healing. Choosing to perform a TMA over more distal level amputations may lead to less re-operation rates, less anesthesia and a decrease in surgical risks and complications.
Dr. Au is a first-year resident at the Yale New Haven Medical Center Foot and Ankle Residency in New Haven, Conn.
Dr. Bruno is a Clinical Instructor of Podiatric Surgery at Yale New Haven Hospital in New Haven Conn., and an Attending physician at the VA Connecticut Healthcare System in Newington, Conn.
Dr. Blume is the Medical Director of Ambulatory Surgery for Yale New Haven Health Systems in New Haven, Conn. He is also an Assistant Clinical Professor of Surgery in the Departments of Anesthesia and Cardiology at Yale School of Medicine in New Haven, Conn.
1. Thorud JC, Jupiter DC, Lorenzana J, Nguyen TT, Shibuya N. Reoperation and reamputation after transmetatarsal amputation: a systematic review and meta-analysis. J Foot Ankle Surg. 2016;55(5):1007-1012.
2. McKittrick LS, McKittrick JB, Risley TS. Transmetatarsal amputation for infection or gangrene in patients with diabetes mellitus. Ann Surg. 1949;130(4):826-840.
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