How To Treat Polysyndactyly And Syndactyly Of The Foot
Drawing on his clinical experience and the literature, this author provides a comprehensive guide to surgical approaches to the various forms of polysyndactyly and syndactyly in pediatric patients, focusing on which segment to delete and how to avoid surgical complications.
Developmental errors in digital and metatarsal formation are common pediatric anomalies. These include bone and soft tissue digital fusions, multiple digits and complex deformities involving both of these patterns. In addition, there may be associated metatarsal, midfoot and rearfoot developmental abnormalities. They may occur in isolation, be combined with deformities of the upper extremity or may be part of a cluster of skeletal and visceral malformations that constitute identifiable syndromes.
In polydactyly, there are more than five digits on an extremity. These take the form of more or less complete duplications. In some cases, the digit is perfectly formed. In others, there may be incomplete expressions distinguished by deficient phalangeal and nail plate development. On occasion, the duplicated digits may be abnormally placed. On rare instances, radiographically recognizable phalanges can be visible in the interval between the first and second metatarsal bases in the same area as the os intermetatarseum. Polydactyly may occur in isolation or may be a component of a syndrome combined with other congenital skeletal and visceral anomalies.1-5
Syndactyly is characterized by failure of two or more adjacent digits to segmentalize fully. A number of subsets are recognized. Simple syndactyly is defined as a complete separation of the adjacent phalanges even though they are contained in a more or less complete single skin envelope. In complete syndactyly, the fusion extends to the hyponychium.
Incomplete syndactyly is defined as partial fusion of adjacent soft tissue segments of the toes but the level of skin fusion does not extend to the hyponychium. The presence of two distinct nail plates usually indicates two separate distal phalanges or at least duplicated terminal tufts. In complex syndactyly, the phalanges fuse together at some point along the course of the bony segments. The fusion is most likely to occur at the tips of the distal phalanges.
Fenestration occurs very infrequently. It most likely occurs in complete syndactyly when a well-defined opening occurs between the superior and inferior aspects of the soft tissue bridge.
Syndactyly is one of the most common occurring limb malformations. It can occur in isolation or may be a component of more than 300 syndromic anomalies.6 Syndactyly occurs in 1:2,000 to 1:2,500 live births, and is three times more common in males. The second and third toes are most frequently involved.7 Tibial (preaxial) polydactyly accounts for 15 percent of all toe duplications and fibular (postaxial) polydactyly accounts for 79 percent.8,9
Polysyndactyly (synpolydactyly) is a variation of polydactyly in which the extra toes are contained in a single skin envelope.
Polysyndactyly in disarray is a deformity usually associated with other named syndromes. The best examples are Carpenter and Apert syndromes. These are complex disorders involving cranial and maxillofacial abnormalities, upper extremity variations of polysyndactyly and foot deformities that include polysyndactyly and major rearfoot coalitions.
A Guide To Anatomical Distribution And Classification
We can further group syndactyly, polydactyly and polysyndactyly according to the anatomical distribution in the extremity. Previously, the terms preaxial, central and postaxial described abnormalities involving the first ray, the central rays and the lateral ray respectively.
A number of years ago, the hand literature began to abandon this classification in favor of using the terms radial, central and ulnar polydactyly, syndactyly and polysyndactyly. The foot and ankle literature is slowly adopting this classification by using tibial and fibular terminology to replace the older terms preaxial and postaxial. The term central remains the same. The foot and ankle literature is somewhat slow in accepting this terminology and many recently written articles continue to use the older terms.
Mirror polydactyly of the foot is a very rare condition and is characterized by a single identifiable large metatarsal and hallux with a number of rays medial and lateral to it.10-15 This condition usually accompanies multiple visceral and skeletal anomalies including various forms of tibial agenesis and fibular dimelia. Rarely, it may occur in isolation.16
There are a number of anatomical classifications for polydactyly and syndactyly in the foot. Most of these are adapted from hand classifications. Some of the proposed forms in these classifications have probably been added for completeness and may not actually exist. This is particularly true for fibular polydactyly and polysyndactyly. On the other hand, some clinical patterns are so unusual and bizarre that they defy all of the currently available classifications.
Classifications are useful for communicating the nature of the deformity among professionals but in the final analysis, classifications are only descriptive and decision making occurs on a case-by-case basis as one studies the anatomy of the deformity and assesses the functional needs of the patient. It is beyond the scope of this article to discuss all of the classifications and I refer the reader to the literature.6,17-22
What You Should Know About Related Syndromes
Syndactyly, polydactyly and polysyndactyly may occur in isolation, or they may be components of an extremely large group of syndromes. The list is quite long and includes such syndromes as Bardet-Biedl syndrome, Peters syndrome, trisomy 18 syndrome, Ellis-Van Creveld syndrome, Rubinstein-Taybi syndrome, caudal regression syndrome and so many others that are beyond the scope of this article to list or discuss. It is important for the surgeon to examine each of these patients carefully for an association of these digital deformities with cranial, cardiac, renal, urogenital and neuroanatomical abnormalities and other neurological issues. Do not presume that these are isolated deformities. In many patients, these associated and more serious conditions have not yet been diagnosed.
Tibial polydactyly. These include duplication of the hallux with and without metatarsal involvement. Metatarsal involvement may be incomplete with abnormality of the metatarsal head, wide or short shaft, or may involve incomplete or complete duplication of the metatarsal. In some cases, the medial metatarsal vestige may be incomplete and tarsal support may be tenuous. In other cases, a metatarsal vestige may simply be a fibrous remnant along the medial side of the first metatarsal and will not be visible on radiograph. The course and insertion of the abductor hallucis is usually abnormal.23
Central polydactyly. This is the least common form of polydactyly. It accounts for 3 to 6 percent of cases.24 In most cases, there is complete duplication of one or more central rays. One can identify a complete metatarsal with its phalanges and its relationships to the tarsal structures can be variable. It may share an articulation with another ray on a single cuneiform or may have a separate accessory cuneiform. On occasion, one can identify an extra metatarsal but the phalangeal structures fail to differentiate.25 The literature has also reported bifid distal metatarsal variations.26
Fibular polydactyly. Anomalies on the lateral side of the foot are much more common than those on the medial side. They are characterized by more or less complete duplication of the phalanges. The metatarsal head may be slightly widened, bifid, dumbbell-shaped, V-shaped, Y-shaped, T-shaped or the metatarsal may be completely duplicated. Generally speaking, the lateral component has a higher incidence of intrinsic anomaly that is likely to make it the least desirable to attempt to salvage. On rare occasions, the lateral metatarsophalangeal joint fails to form. However, there are many exceptions to this rule.27
Tibial syndactyly. Rarely, the first and second digits may be syndactylized. When this occurs, there is usually a normal row of phalanges in both the first and second toes. The metatarsophalangeal joints are normal.
Central syndactyly. The most common form of central syndactyly is more or less complete syndactyly of the second and third toes. The middle phalanx of the third toe is likely to be anomalous and may not have a physis. The middle phalanx of the second toe is often wedged with the apex lateral so the distal portion of the second toe abducts. Due to these abnormalities, progressive deformity of the two toes is more likely to occur with subsequent growth than in more lateral forms of this condition. Less frequently, the third and fourth toes are involved. Very rarely, the fourth and fifth toes are involved.
Critical features in this form of syndactyly are the extent of the fusion of the skin envelope and the presence or absence of phalangeal fusion. Of interest, when there is fusion of the phalanges themselves, this deformity is frequently associated with macrodactyly of one or both of the involved toes.
Fibular syndactyly. In this deformity, a single skin envelope contains the fourth and fifth toes. Most frequently, the phalanges of each of the pair are separate and distinct. It is possible that the fifth toe could be a biphalangeal toe instead of having three distinct phalanges.
Tibial polysyndactyly. These take two forms. More frequently, there is duplication of the distal phalanx with separate nail plates and an extraordinarily wide proximal phalanx. Less frequently, there may be duplication of the proximal and distal phalanx. Changes in the first metatarsal head are variable. If the duplication involves the distal phalanges alone, the metatarsophalangeal joint is likely to be normal. If there is duplication of the proximal and distal phalanges, the first metatarsal head will be anomalous and the anatomy will support the two phalangeal bases.
Central polysyndactyly. The most frequent form is duplication of the distal phalanx. One can recognize this clinically by the presence of two distinct nail plates. Involvement of the middle and proximal phalanx is much less frequent.
Fibular polysyndactyly. There are two distinct forms. The most common form is duplication of the distal phalanx of the fifth toe and syndactyly with the fourth toe. Less common is duplication of all three phalanges of the fifth toe and a metatarsal vestige with syndactyly to the fourth toe. On occasion, there is duplication of the segments of the fifth toe with anomalies of the fifth metatarsal head that take the form of a V- or Y-shaped fifth metatarsal. A complicating factor in this form is abnormal sagittal plane position of one or both of the abnormal segments of the fifth metatarsal. This can lead to abnormal weightbearing from plantarflexion of one of the bifid metatarsal head segments. There may be abnormalities in the proximal phalanx and the middle phalanx that can make it difficult to determine the segment to be deleted.
Essential Treatment Considerations
The goals and objectives of treatment of congenital abnormalities of the lesser toes should include pain relief, proper alignment of the toes and comfort when the patient is wearing shoes.28
There are some general rules that hold true for surgical repair of syndactyly, polydactyly and polysyndactyly. With some exceptions, surgeons can best treat most syndactyly on the fibular side of the foot by deleting the lateral segment. On the other hand, when it comes to most cases of tibial polydactyly, surgeons best manage these cases by deleting the medial segment.
Central polydactyly poses some difficulties. First, it is difficult to decide which is the abnormal ray or rays. A good rule is to identify the ray that is either abnormally long or abnormally short. The surgical dilemma is that resection of the ray itself does not narrow the foot and reconstruction of a cosmetically acceptable web space is extremely difficult. Physicians must give additional attention to the abnormalities in the tarsus.
Central syndactyly also presents a surgical dilemma in the decision to intervene. Unless there is discrepant growth in the two toes, there is no medical indication to separate the toes. There are two exceptions. First, syndactyly repair would be justified if there were progressing deformity because of asymmetrical growth. Second, on rare occasions, psychological issues may become so severe that an attempt at desyndactyly becomes justified.
Fibular polysyndactyly usually causes clinical symptoms. There may be difficulty with foot hygiene. Very frequently, there are issues with shoe gear fitting. The decision on which segment needs deletion depends on the anatomy of the deformity. Alignment is critical but one must also take the final cosmetic appearance into account.
Fibular polydactyly can present some difficult surgical planning issues and treatment is influenced by the anatomy of the fifth metatarsal. In most cases, the lateral segment will be the one surgeons choose for deletion. If the fifth metatarsal head is large transversely after deletion of the lateral segment, the head will need debulking and narrowing.
The concern here is damage to the physis of the fifth metatarsal located distally. With careful resection, the physis will probably continue to function normally. The possibility of lateral growth arrest with subsequent lateral deviation of the fifth toe is a real possibility. If the fifth metatarsal is Y-shaped, the medial portion may be adducted in relation to the proximal segment and its shaft components may be somewhat diminutive.
There could also be some sagittal plane malpositioning with unacceptable plantarflexion or dorsiflexion. Resecting the lateral portion leaves a substantial amount of lateral cortical deficiency and makes additional corrective osteotomy at the same time somewhat risky since the osteotomy will occur near the “watershed” area of the metatarsal shaft. Fixation is difficult because of the loss of substantial lateral cortex and the possibility of delayed union or nonunion is very real because of its location in the shaft.
When Skin Grafting Is Necessary
In the separation of digital syndactyly and repair of the various forms of polydactyly, the surgeon must be prepared to perform a skin graft. There is usually enough skin to design a flap to cover one side of one of the toes but the adjacent side of the other toe will require a full thickness skin graft. Skin over the dorsolateral aspect of the sinus tarsi or the lateral ankle just anterior to the tendo-Achilles is a good cosmetic match. The groin is a good site as well but harvesting should happen in an area sufficiently lateral of midline so there is little risk of transplanting pubic hairs.
Researchers have described many separation techniques that use multiple flaps plus a skin graft.29-31 Authors have described a technique for repair of polysyndactyly without the need for skin grafting.32,33 There are several reports in the literature describing the technique of allowing the exposed surface of the toe to granulate in.34,35
In repairs that need skin grafting, a major concern is loss of the graft. This may occur because of excessive movement of the parts, the development of a hematoma or seroma under the graft, or failure to prepare the graft by appropriate debridement of all of the subcutaneous fat. It is advantageous to immobilize the part for several weeks in order to allow for vascularization of the graft. This can be very difficult in young children who are incapable of following postoperative protocol because of their age. Immobilization in a cast to minimize or prevent weightbearing is helpful. It is also helpful to operate when the patient is at an age when immobilization can be easily secured (perhaps before the patient begins ambulating or when the child is old enough to appreciate the gravity of the situation and is capable of cooperation).
On rare occasions, keloid formation may occur. This is very difficult to manage.36-38 A possible solution is the use of methotrexate to minimize scar formation.39
The surgeon must also consider the potential negative effects that harvesting the skin graft can have on the donor site. Unsightly scars can be a problem. Contractures of the scar at the donor site can be a major issue. Hyperpigmentation can also occur. Many skin grafts are harvested from the bikini area in the groin. There is a possibility of color and texture mismatch at the recipient site. The dorsolateral sinus tarsi followed by the areas between the tendo-Achilles and the malleoli match well, and morbidity is minimal as long as the surgeon avoids major nerves.
Other Pertinent Insights On Reducing Complication Risk
Whenever possible, the respective surgeons should perform repair of combined congenital deformities of the hand and foot together. Obviously, a single anesthesia is advantageous. However, the additional benefit is that skin harvested from a congenital toe abnormality can be a full thickness skin graft for a finger.40
Whenever possible, one should use an absorbable suture not only in cases of syndactyly and polydactyly repair, but also in most other pediatric foot surgeries.41 This spares the child and the surgeon the difficulty of removing a large number of non-absorbable sutures.
It is also important to keep in mind that the surgeon should never attempt desyndactyly or any intervention on both sides of a toe in those cases of syndactyly and polysyndactyly involving three adjacent toes. The risk of vascular complications is overwhelming and there is an extremely high likelihood of ischemia of two or all three of the involved toes with disastrous complications and major digital loss.
In spite of apparently successful correction of tibial polydactyly, progressive varus deformity of the hallux may persist and, in some cases, worsen. This is due in part to the development of the adaptive medial position of the metatarsal articular surface. In very young children, there is a high potential for remodeling resulting in better alignment of the articular surface. Deviation may also be due to persistent tethering of deep soft tissue along the medial side of the foot that is caused by remnants of an incompletely formed medial ray.
The longitudinal epiphyseal bracket occasionally occurs in polydactyly and polysyndactyly. In this deformity, rather than having a single epiphysis located at the end of a bone, the epiphyseal plate and the epiphysis itself wraps around one side of the involved bone.42 This causes a restriction of growth on one side with overall shortening of the bone but allows some longitudinal growth on the opposite side. The result is shortening and angular deformity.43,44 When it occurs in the first metatarsal, the result is varus deformity.45 The longitudinal epiphyseal bracket is present in 2 to 14 percent of congenital foot and hand deformities.46 This lesion has only been reported in short tubular bones with epiphyses located at the proximal ends of the bones. This limits the deformity to the phalanges and first metatarsal.
Treatment is by bracket excision.43,47-49 Before epiphyseal ossification, one can simply excise the bracket. Once ossification occurs, it is necessary to place something in the void in order to prevent the bracket from reestablishing. This can be fat harvested from areas adjacent to the surgery or one can place a strip of methyl methacrylate against the diaphysis after excision of the bracket.
Repair of these deformities is very rewarding both for the patient and the surgeon. Results are instantaneous and immediately apparent.
However, there is the potential for serious and irreversible error when the surgeon does not take the time to evaluate the anatomy carefully so goals and objectives become realistic and he or she can avoid complications. Some semblance of normal function is the major goal but surgeons cannot totally ignore the cosmetics. Specific issues are scar formation, appropriate tissue color and texture match, creation of an acceptable web space, flap development and skin grafting, and maintenance of joint motion.
Technical skills notwithstanding, careful evaluation of the clinical appearance of the parts and the radiographs is the most important component in ensuring a good result. This type of surgery reinforces the old adage “measure twice, cut once.”
Dr. Harris is a Clinical Associate Professor in the Department of Orthopaedics and Rehabilitation at the Loyola Medical Center in Maywood, Ill. He is a Fellow of the American College of Foot and Ankle Surgeons.
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