Toe and Partial Foot Amputations

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  • 1. Toe and Partial Foot AmputationsRobert G. Atnip, MDN ormal ambulation is a complex process made possible by the architecture of the foot and by the machinery ofthe neuromuscular axis. Amputation of any portion of the to preserving the normal architecture. Multiple ligaments in- cluding the large plantar fascia are essential to create and maintain joint stability.foot will alter the process of ambulation in degrees ranging Sensory innervation is supplied by five nerves: the super-from trivial to prohibitive, depending not simply on the ficial peroneal for the dorsal surface; the deep peroneal for aamount of tissue removed, but also on the existing health and very small area of the first web space; the sural for the poste-functional status of the patient. For any given patient, ambu- rior and lateral areas; the saphenous for the medial aspect;lation will be impaired in direct proportion to the amount of and the posterior tibial for the plantar surface. Of thesetissue removed. Further consideration of this concept will be nerves, only the posterior tibial is crucial for normal function,included in the discussion of each amputation level in the as it provides protective sensation on the weight-bearing sur-ensuing paragraphs. face. The most commonly employed levels of amputation are Arterial supply derives from the posterior tibial artery, thethe phalangeal and transmetatarsal, each of which can be dorsalis pedis (a continuation of the anterior tibial), and thesingle or multiple, and are sometimes performed in combi- peroneal artery. The latter vessel ends in smaller branches atnation. Less common are amputations performed through the ankle, but the two tibial vessels extend into the foot tothe midfoot (Chopart and Lisfranc), and hindfoot (Syme) form the plantar arches and directly nourish the forefoot and(Fig. 1). toes. Each toe has medial and lateral digital arteries and nerves.Anatomy of the Foot and ToesThe complexity of the foot is illustrated by an accounting of Phalangeal Amputationits components: 26 bones, 33 joints, and over 100 muscles, The hallux has two phalanges, and the other four digits haveligaments, and tendons, in addition to fatty tissue, vessels, three, with the distal phalanx being the smallest. Beyond thisand nerves, and its investing envelope of skin. These struc- simple anatomic difference, the hallux overshadows thetures are somewhat artificially divided into three zones: the other digits in functional importance by virtue of its roles inforefoot, including the phalanges, sesamoids, and metatarsals balance of the forefoot and in push-off during ambulation.of the five digits; the midfoot, composed of the five tarsal Although the second toe can adapt to some extent in thebones, and the hindfoot, made up of the talus and calcaneus. absence of the great toe, patients who have lost the hallux The range of motion of the foot includes plantar flexion, invariably notice a substantial difference in the mechanics ofpowered by the posterior compartment muscles (tibialis pos- walking, especially after transmetatarsal amputation. Ampu-terior and flexor digitorum), and innervated by the posterior tations of the great toe should be performed for only thetibial nerve. Extension of the foot, also called dorsiflexion, is strictest and most carefully considered indications.enabled by the anterior compartment muscles (tibialis ante- Although amputation of only the distal part of a toe isrior and extensor digitorum), innervated by the anterior tibial technically possible, there is little functional advantage to(deep peroneal) nerve. Eversion is performed by the pero- having half or two-thirds of a toe, even the great toe. Certainlyneus muscles and is rather limited in range. Inversion derives in any situation where perfusion is abnormal, digital ampu-from the posterior muscles and is equally limited in range. tations are best performed through the base of the proximalThe intrinsic muscles of the foot (lumbricals and interossei) phalanx, leaving a relatively short stump with a better likeli-complement the extrinsic forces to maintain balance, allow hood of healing.for finer movements of the toes, and contribute signficantly Digital amputations are typically performed with a “fish- mouth” technique, which is preferred to a circular incision in all cases intended for primary closure. Since the vesselsPenn State Hershey Medical Center, College of Medicine of the Pennsylvania course along the medial and lateral aspects of the toe, it is State University, 500 University Drive, Hershey, PA. sensible to orient the fishmouth in the anterior-posteriorAddress reprint requests to Dr. Robert G. Atnip, Professor of Surgery and Radiology, Chief of Vascular Surgery, Penn State Hershey Medical Cen- (dorsal-plantar) direction, so that the bases of the flaps are ter, College of Medicine of the Pennsylvania State University, 500 Uni- medial and lateral, including the digital vessels. Nonetheless, versity Drive, Hershey, PA 17033-2390. E-mail: ratnip@psu.edu many surgeons obtain equally good results from the use of a1524-153X/05/$-see front matter © 2005 Elsevier Inc. All rights reserved. 67doi:10.1053/j.optechgensurg.2005.07.002
  • 2. 68 R.G. Atnip The ideal flaps will be just long enough to coapt without tension, but “too long” is always preferable to “too short.” When faced with inadequate soft tissue for closure, the sur- geon can use standard plastic techniques to mobilize the flaps further, or can attempt to shorten the bone, even to the point of excising the entire base of the phalanx. The options in that case are to convert to a transmetatarsal amputation (see next section), or to leave the metatarsal head intact. In the latter case, it is imperative to remove the articular cartilage to avoid necrosis and infection of this nonvascular tissue layer. As described in a previous section, closure of the skin can be accomplished with the suture method and material of choice, provided that the technique is as gentle and atrau- matic as possible. A minimal number of sutures. combined with interspersed thin adhesive strips, provide a secure clo- sure with minimal tissue injury. Transmetatarsal Amputation (TMA) This procedure consists of amputation of one or more toes along with a portion of the corresponding metatarsal bone(s). The success of the procedure depends heavily on the health and integrity of the plantar skin and soft tissues that will provide coverage of the bone stump and ultimately form the weight bearing surface. Transmetatarsal amputation is a very useful and effective method for treating ischemic necrosis of the forefoot, and often represents the patient’s last hope for salvage of a functional foot. In cases where the plantar tissuesFigure 1 The skeleton of the foot, showing the level of bony transec-tion for each of the four standard toe or partial foot amputations.Creation of the soft-tissue flaps for each of these procedures is de-scribed in more detail in the text.medial-lateral fishmouth with anterior and posterior flaps. Ineither case, the incisions are arc shaped and symmetric, eachencompassing a hemi-circumference of the toe. It is oftennecessary for the apex of the flap to extend rather close to themargin of necrosis, but the surgeon must visually verify thatthe skin margins of the flap are viable and not grossly in-fected. If the surgeon has any doubt regarding the skin mar-gins, the wound might be better left open temporarily. The soft tissue of the toes is sparse, consisting of skin,minimal subcutaneous fat with nerves and vessels, investingfascia, and tendons within their sheaths. Flaps must thereforebe incised perpendicular to the skin, full thickness down tothe bone, preserving all soft tissue with the flap. The flapsshould initially be generously long (as the distal pathologypermits), with the intent of shortening them to optimallength for a tension-free closure. After stripping of the peri-osteum, the bone should be amputated through the mid-shaft, and then shortened and smoothed with a rongeurdown to the base, taking care not to violate the metatarso- Figure 2 A simple amputation through the proximal phalanx of thephalangeal joint. The large flexor and extensor tendons left great toe. Symmetric medial and lateral flaps have been created,should be then be distracted, amputated sharply, and al- based on the digital arteries. The stump of the phalanx is visible inlowed to retract into the deeper soft tissues. Any final de- the base of the wound, along with the cut ends of the extensor andbridement of the flaps can then be performed (Fig. 2). flexor tendons.
  • 3. Toe and partial foot amputations 69of the forefoot are extensively compromised, however, TMAis unlikely to be a realistic option. It is important to note that TMA includes resection of themetatarsal head. Although sometimes tempting, amputationof a toe through the metatarso-phalangeal (MTP) joint shouldbe avoided for several reasons. Leaving the metatarsal headdoes not improve function, and instead creates a potentialpressure point that may predispose to recurrent ulcerationand infection. The bulk of the metatarsal head can make skinclosure more difficult. Since articular cartilage depends onsynovial fluid for its nutrient supply, the cartilage may dieonce the joint has been disrupted. Removing the cartilage butleaving the bony head offers no advantage over amputation ofthe entire distal metatarsal. Transmetatarsal amputation is indicated primarily in twosituations: necrosis or ulceration of the toe(s) at or proximalto the level of the MTP joint; and/or plantar pressure ulcer-ation over the metatarsal heads. The extent of the amputationis dictated by the extent of necrosis, and can encompass asingle toe, two or three toes, or the entire forefoot. Thesevariations will be considered separately in the following para-graphs.Single Outer-Toe TMAThe toe and its metatarsal are sometimes called a “ray,” andthe corresponding surgery can be called a “ray” amputation.The most commonly performed single ray amputations arethose of the first or fifth toes. Each is performed by the use of Figure 3 An example of the “racket-handle” type of incision used fora “racket-handle” incision consisting of an elliptical cut transmetatarsal amputation of the great toe. The racket joins thearound the base of the affected toe, and a straight incision handle over the medial aspect of the metatarso-phalangeal joint, andstarting at the proximal end of the ellipse and continuing the handle extends along the metatarsal shaft. This incision can bealong the outer edge of the metatarsal shaft (Fig. 3). The exact modified for combined amputations of the first and second toes, andcontour of the incision must often be modified by the pattern can also be used for amputation of the fifth toe, or of the fourth and fifth toes together.of ulceration or necrosis of the toe, but must be designed topreserve as much plantar skin and soft tissue as possible. It isoften convenient to use the elliptical incision to disarticulatethe toe at the MTP joint, and thus remove this ulcerated or then assess the closure potential of the dorsal and plantardead tissue from the surgical field before proceeding with the flaps. If at all possible, any redundancy should be trimmeddeeper dissection. This technique has the added advantage from the dorsal flap rather than the plantar, unless the plantarthat the metatarsal is easier to visualize and isolate after the tissue appears to be of poor quality. In cases where the flapstoe itself has been removed (Fig. 4). will not approximate without tension, the surgeon has the After disarticulation of the MTP joint, the joint capsule choices of resecting more bone, debulking the flaps, leavingmust be sharply and completely separated from the metatar- part of the wound open, or amputating the adjacent ray tosal head. Great care must be taken in avoiding entry into the mobilize more soft tissue. When all is satisfactory, closure isMTP joint of the adjacent ray, and in avoiding injury to the then performed as described in the preceding section.plantar soft tissues abutting the shaft of the metatarsal. (Inthese tissues are located the arterial supply to the plantar Single Inner-Toe TMAflap.) Once the head is free, one then proceeds with stripping Transmetatarsal amputation of an inner toe (toes 2, 3, or 4)of the periosteum of the metatarsal shaft to the desired level can be a useful procedure, but requires modifications in tech-using a small elevator. The shaft is then divided with a bone nique. Because of the constraints imposed by the adjacentcutter and recessed with a rongeur so that the stump is bev- rays, it is more difficult to perform isolated TMA of an innereled with the shorter edge on the plantar surface (to avoid a toe, and more difficult to obtain good closure. If the plantarpressure point) (Fig. 5). tissues are relatively normal, the amputation can be done The next step is to excise the remnants of the joint capsule, using the racket-handle technique, with the handle extend-which in the case of the first toe, will include the sesamoid ing from the dorsal end of the ellipse along the dorsal surfacebone. These structures are virtually avascular and heal of the metatarsal shaft. Added difficulties occur when thepoorly. The dissection is best done with a very sharp #15 plantar skin is ulcerated or ischemic, in which case, it isscalpel blade, taking only the ligamentous and bony compo- impossible to avoid an incision on the plantar weight-bearingnents, and sparing the plantar fascia and other soft tissues. surface. In either case, the operation proceeds best by disar- Once the tissue resection has been completed, one must ticulating and removing the toe at the MTP joint, freeing the
  • 4. 70 R.G. Atnip Figure 4 Transmetatarsal amputation of the great toe. The specimen has been removed after disarticulation of the metatarso-phalangeal joint. The sesamoid bone has been carefully ex- cised from the plantar flap. The transected flexor hallucis longus ten- don can be seen posterior to the shaft of the metatarsal. The plantar flap is redundant, and will need to be sculpted and trimmed before closure.head from the joint capsule (while not entering the adjacent Multiple TMAjoints), stripping and resecting the desired length of shaft, Although in theory any combination of toes could be ampu-and excising the remnants of joint capsule before closing. The tated at the TMA level, such a decision should take intoessentially fixed position of the adjacent metatarsal rays can account the relative importance of the various toes in themake it rather difficult to close an inner-toe TMA without stability of the foot and the mechanics of walking. Significantskin tension. The foot can be wrapped to compress the meta- stability and function are lost with amputation of the greattarsals and reduce tension on the suture line, but only if toe, especially at the TMA level, and the loss is even greater ifprecautions are taken to avoid pressure ulceration from the the second toe is also taken. To perform TMA of the first threebandage itself. toes would likely be a disservice to the patient, leaving him/Figure 5 Transmetatarsal amputationof the great toe. The metatarsal shafthas been cut on a posterior bevel, andthe plantar flap has been trimmed ofexcess soft tissue. The flexor tendonhas been cut shorter than the bone.The joint capsule of the adjacent sec-ond MTP joint is intact, and has notbeen entered or disrupted.
  • 5. Toe and partial foot amputations 71her with a narrow, tapered, and dysfunctional forefoot. Sim-ilarly, the more toes removed from the lateral aspect of thefoot, the greater the asymmetry and imbalance of forces onthe remaining rays. The technique for multiple TMA is a simple modificationof that for first or fifth ray amputation. An ellipitical incisionis created to encompass the base of the affected toes, modifiedas needed to incorporate any areas of dorsal or plantar necro-sis. The racket handle then extends along the outer aspect ofthe metatarsal shaft. Flaps are created in identical fashion tostandard TMA. The MTP joints are disarticulated, the meta-tarsal shafts amputated, recessed, and beveled appropriately.The flaps are then sculpted and closed without tension. Although preservation of the medial toes is more advanta-geous than saving the lateral toes, it is questionable whetherTMA of more than two adjacent rays should ever be per-formed. In patients with diabetic or other polyneuropathies,amputations that create gross asymmetry of the forefoot areassociated with a notoriously high incidence of subsequentbreakdown and re-amputation. As a general rule, balance,function, and stump integrity will be better with a complete(full-foot) transmetatarsal amputation.Full-Foot TMAAmputation of the entire forefoot at the transmetatarsal level Figure 6 Flaps outlined for a “full foot” transmetatarsal amputation.is one of the most useful procedures in the surgical armamen- The plantar flap is long, and the plantar incision extends along thetarium. When properly performed, full-foot TMA results in a base of the toes. The dorsal incision crosses transversely over thesymmetric stump with favorable weight distribution. Al- mid- to distal level of the metatarsal shafts. Either the dorsal orthough there is no question that patients with TMA must plantar incisions may need to be modified if there is ulceration orlearn to adapt their balance, gait, and stride after loss of the necrosis of the forefoot.forefoot, most patients will be able to walk, either indepen-dently or with simple supportive devices. Foot orthoses orcustom shoes can be useful to facilitate walking, but prosthe- sesamoid bones and portions of the joint capsules, whichses are not necessary. should be carefully excised, leaving adjacent muscle and ves- If the plantar tissues are intact, the plantar incision for sels intact. All potentially viable skin and soft tissue of bothTMA crosses the foot as close to the base of the toes as pos- dorsal and plantar flaps should be spared until the final stagesible. The dorsal incision is made across the mid- to distal of the procedure. Excess tissue can be removed and flapslevel of the metatarsal shafts, as dictated by the pattern of trimmed during closure, once it is known how the flaps canforefoot necrosis (Fig. 6). The dorsal and plantar incisions are best be re-approximated.then connected by axial incisions made along the shafts of the In the presence of ulceration or necrosis on the plantarfirst and fifth metatarsals. The result will be a plantar flap of surface, the placement of the plantar incision and the creationvariable length. In developing the plantar flap, the incision of the plantar flap will need to be individualized. In theshould be carried down to the MTP joints, which should all common case of a neuropathic ulcer penetrating to the meta-then be disarticulated. This allows the surgeon to find the tarsal head, the ulcer can be excised in elliptical or V-shapedproper plane along the plantar surface of the metatarsal head fashion, which in essence will create two plantar flaps andand shaft. From the plantar approach, the metatarsal shafts hence require a final T-shaped suture line. If the plantarangle toward the dorsum of the foot as they traverse proxi- necrosis is more medial or lateral than central, the remainingmally, and it is imperative that the surgeon adhere closely to plantar tissue can often be rotated to achieve final closure. Inthe shafts to preserve the muscles and vessels of the plantar such situations, some of the metatarsal shafts may need to beflap. amputated shorter than others to enable closure of the flaps The dorsal incision is carried directly down through the without tension. It is in these cases that the imagination andsoft tissues, extensor tendons, and dorsal vessels to the ante- reconstructive skill of the surgeon become especially impor-rior surface of the metatarsal shafts. At the desired level, these tant.shafts are stripped of periosteum and divided with bone cut- Like most amputations below the ankle, a full-foot TMAter or rongeur. Working simultaneously from the plantar lends itself to only one layer of closure, the skin. In essence,surface, the interosseus muscles are divided along with any the dorsal surface consists of skin, virtually no subcutaneousremaining ligaments and tendons, and the specimen re- fat, and a very thin layer of fascia. If the plantar flap is toomoved. The metatarsal stumps should be recessed and bev- long, it should be shortened to eliminate redundancy andeled, shorter on the plantar aspect. dead space (and thereby minimize the chance of hematoma). Remaining on the plantar flap at this point will be the The optimal length is that which brings the plantar tissues up
  • 6. 72 R.G. Atnip Figure 7 Closure of the transmetatar- sal amputation with simple inter- rupted sutures. The metatarsal shafts have been cut with a posterior bevel, essentially flush with the dorsal inci- sion. The plantar flap has been sculpted to approximate the dorsal tissue without tension or redundancy.to abut and securely cover the bony stumps with minimal employed in America by battlefield surgeons in the Civildead space, while allowing the plantar and dorsal skin to be War. They hold out the prospect of saving part of the foot insutured without tension (Fig. 7). patients who fail or are not eligible for TMA, but they are Given that the success and functionality of forefoot am- seldom used in modern amputation surgery. The chief dis-putation are much superior to that of mid- or hindfoot advantage of the Lisfranc and Chopart procedures is that theyamputations, there can be a role for a certain surgical disrupt the tendinous attachments of the midfoot and predis-“license” in performing modified TMA for patients with pose to stump deformities associated with dysfunctional am-extensive forefoot necrosis. One option is to amputate the bulation. The loss of foot length and loss of tendon insertionsmetatarsal shafts very short, provided that the surgeon is leaves the plantar flexors almost unopposed, resulting in anaware of the dangers inherent in violating the tarso-meta- equinus deformity, with a consequent shift of weight bearingtarsal joints. Removal of the first and/or fifth metatarsal from the calcaneus onto the stump itself. Although technicalbases will result in loss of part of the insertion of the modifications have been introduced that partly compensatetibialis posterior and peroneus tendons, respectively. The for this imbalance of forces, midfoot amputation has still notensuing imbalance of forces on the TMA stump leads to gained wide acceptance as an alternative to below-knee am-deformity, pressure ulceration, and impaired walking. putation. Braces and prostheses are usually required forWholesale entry into the tarso-metatarsal joints is tanta- walking, and there is a relatively high incidence of conversionmount to performing a Lisfranc amputation, which is dis- to BKA.cussed in the following section. The Lisfranc amputation is essentially a disarticulation of If the bone and deeper tissues are viable but local coverage the tarso-metatarsal joints, using a plantar flap for coverageis inadequate, vacuum-assisted closure and/or skin grafting with a technique virtually identical to transmetatarsal ampu-may allow an “open” TMA to eventually heal. In rare cases, tation. The important technical point is to remove as muchthe surgeon may wish to consider a free tissue transfer to articular cartilage as possible from the cuneiform and cuboidsalvage the foot, but an almost ideal set of conditions must surfaces to circumvent cartilaginous necrosis. Various ten-pertain to justify such a complex undertaking. The indica- don transfers, reattachments, and tendo-Achilles lengtheningtions, techniques, risks, and outcomes of free-tissue transfer (TAL) have been proposed to prevent equinus deformity, butare beyond the scope of this monograph. results are often suboptimal. The Chopart amputation shortens the foot even furtherMidfoot Amputations by removing the entire mid- and forefoot through the talo-navicular and calcaneo-cuboid joints. Once again, a(Lisfranc and Chopart) plantar flap is used for coverage, but problems with stumpThese two surgical procedures were introduced by French deformity tend to be even more common than with thesurgeons in the 19th century, and they were supposedly first Lisfranc.
  • 7. Toe and partial foot amputations 73Conclusions ing amputations must approach each procedure with the finest exacting technique and attention to detail worthy of theLocomotion is a fundamental human activity made possible craft.by the structure and function of the foot. Most humans con-sider the potential loss of part or all of the foot as catastrophic, Suggested Readingand view amputation as a disfiguring and destructive proce- Attinger C, Cooper P, Blume P, Bulan E: The safest surgical incisions anddure. Yet due to either trauma or disease, as many as 150,000 amputations applying the angiosome priciples and using the Doppler to assess the arterial-arterial connections of the foot and ankle. Foot andpatients per year are confronted with the necessity for ampu- Ankle Clinics 6:745-799, 2001tation surgery, virtually always with no realistic alternative. Crinnion J, Hicks D: Transmetatarsal amputation: an 8-year experience. AnnFor these patients, properly performed amputation surgery is R Coll Surg Engl 84:291-295, 2002a reconstructive procedure that rehabilitates and restores qual- Funk C, Young G: Subtotal pedal amputations. Biomechanical and intraop- erative considerations. J Am Podiatr Med Assoc 91:6-12, 2001ity of life, albeit, a different life than the patient might desire. Pinzur MS, Pinto MA, Schon LC, Smith DG: Controversies in amputationAlthough many patients have such advanced disease that loss surgery. Instr Course Lect 52:445-451, 2003of the entire foot is inevitable, for some the goal of partial foot Rumenapf G: Borderline amputations in diabetics— open questions andsalvage is achievable. This chapter has described a variety of critical evaluation. Zentralblatt für Chirurgie 128:726-733, 2003 Sanders LJ: Transmetatarsal and midfoot amputations. Clin Podiatr Medprocedures that preserve structure and function of the foot Surg 14:741-762, 1997sufficient to enable ambulation without a limb prosthesis. To Smith DG: Principles of partial foot amputations in the diabetic. Instr Courseachieve the best results for each patient, the surgeon perform- Lect 48:321-329, 1999