Bilateral Syndactyly Release of Third and Fourth Fingers

Amniotic band syndrome, or constriction ring syndrome, happens when a developing fetus gets tangled in the fibrous bands of the amniotic sac. Sometimes, fingers and toes can become trapped in these fibrous bands, with results ranging from amputation of the digits, to fusion of the fingers or toes, termed syndactyly. Syndactyly is amongst the most frequent congenital hand anomaly and is termed simple when the digits are connected by soft tissue only, and complex when one or more phalanges are fused. In complicated syndactyly, there are additional bony elements in between the digits making it challenging if not impossible to separate safely. The patient in this case is a 1-year-old male with complex syndactyly of the left hand and simple syndactyly of the right hand. Here, both sides are released, with the left side involving a full-thickness skin graft taken from the patient's groin crease. This case was filmed during a surgical mission with the World Surgical Foundation in Honduras.

Syndactyly is amongst the most frequent congenital hand anomaly with an incidence of approximately 1 in 2000.^{1, 2, 3, 4} Commonly referred to as “webbed fingers” it results from failure of separation of digits in the sixth to eighth week of intrauterine life.⁴ Syndactyly may occur as an isolated condition or in association with a number of syndromes, some mild and others profound. It is twice as common in males and affects one or both hands in equal frequency.⁴ It can affect some or all digits with ring-long finger syndactyly being the most frequent.⁴

Syndactyly is termed simple when the digits are connected by soft tissue only, complex when one or more phalanges are fused.⁴ In complicated syndactyly, there are additional bony elements in between the digits making it challenging if not impossible to separate safely.⁴ Syndactyly may be complete if joined from web to tip or incomplete if the union extends to less than the tip.⁴

Evaluation of a patient with syndactyly should be comprehensive. In addition to a detailed hand examination with radiographs, a complete examination is necessary to detect additional anomalies if present. Surgical treatment is almost always indicated for functional and aesthetic reasons. Most surgeons agree that surgery to separate the digits should commence at 12–18 months and be completed by the time the child attends school.⁴ An exception would be thumb-index syndactyly, which should be separated as early as practically feasible.

The preferred surgical technique, adapted from Dr. Adrian Flatt’s exceptional text “The Care of Congenital Hand Anomalies”,⁴ can be summarized as follows. The principle steps in the operation to separate digits are fairly consistent. Minor variations occur, especially with regards to skin incisions for web reconstruction. The procedure is done under general anesthesia and tourniquet control.

Surgery is staged if multiple digits are involved. Digits with unequal lengths are separated first. This would include thumb-index, index-long, and ring-small. In cases where all fingers are involved, only one side of a digit is separated at any one time to avoid vascular compromise.

In separating fingers, the critical step is to reconstruct the web or commissure with sufficient width in the correct location. This is best accomplished by a broad dorsal flap that extends two-thirds of the way along the proximal segment. Another method involves the use of triangular volar and dorsal flaps. A single wide dorsal flap will provide adequate width to the web space and minimize the risk of web creep and contracture. Distal to this, the skin incision zig zags to the tip of the digit. The zig-zag incisions on the palmar and dorsal aspect of the digit should be mirror images such that when transposed they interdigitate to provide adequate coverage. It is helpful to bias the flaps in favor of one digit so that complete coverage is obtained in that one digit and any raw areas are confined to the other. The first palmar incision is made as a rectangular flap based on the biased digit. The resulting defect after raising this flap is covered by the dorsal flap forming the web. The natatory ligament should be excised to allow proper positioning and seating of the dorsal flap and prevent later distal web creep.

Care should be taken to identify and protect the neurovascular bundle. A distal nerve bifurcation can be addressed by splitting the nerve but a similar bifurcation of the artery should probably be left intact rather than sacrifice a proper digital artery. Once the skin incisions are made and neurovascular bundles identified, the digits are separated without much difficulty from distal to proximal. The inter-metacarpal ligament should not be divided. Once separated, the digits and skin flaps are defatted generously without causing devitalization. This will facilitate tension-free wound closure.

In a case with complex syndactyly, both digits may share a common nail. Separation involves splitting the nail complex and then recreating the nail fold in each digit by excising a wedge of subcutaneous fat and suturing the skin to the lateral nail plate. Alternate methods are described including the use of local flaps and a composite skin-subcutaneous graft from a toe. Separation of fused phalanges and joints must be undertaken with some caution. Separation is warranted if there is a clear plane of separation or the bony bridge is small, but a complete fusion of adjacent phalanges should probably be left alone and the syndactyly accepted.

The zig-zag skin flaps are transposed and sutured with 6-0 absorbable sutures. Raw areas must be covered with a full-thickness skin graft to avoid graft contracture. The graft is usually harvested from the inguinal area and the donor site is closed primarily.

The operated fingers and the entire hand is covered with a non-adherent soft absorbent dressing designed to provide even compression to the graft and separated fingers. The entire limb is immobilized in an above elbow sugar tong splint and left undisturbed for 2 weeks. After the first dressing change, a lighter dressing is applied without splinting and the child allowed to self-mobilize. It is not uncommon to see small areas of epidermal loss in full-thickness grafts and these will re-epithelialize in a few weeks. If there is full-thickness graft loss then debridement and regrafting should be performed right away to prevent scar and contracture.

Patients with syndactyly involving multiple digits will undergo sequential staged surgery until all digits are separated. Thereafter, serial follow up is necessary to watch for recurrent contracture, web creep, and angular deformity that may need further surgical correction.

Presented here is the case is a 1-year-old child with complex syndactyly of the left hand and simple syndactyly of the right hand resulting from amniotic band syndrome. Physicians have been dealing with this condition since the beginning of modern medicine.⁵ Normally, webbing between digits will regress between 6–8 weeks of gestation in a distal-to-proximal fashion.⁶ The normal result is the formation of a web space between each digit with a commissure extending at a 45-degree angle from the mid-proximal phalanx to the metacarpal head.⁷ Syndactyly can be defined as a variable fusion of soft tissue and/or osteoarticular elements between adjacent digits, resulting from some degree of failure of the aforementioned developmental processes. Syndactyly has highly variable morphological presentations, and the exact surgical management depends upon the type of syndactyly each patient presents with.

Syndactyly can be classified as complete or incomplete depending on the extent of web space involvement, and as simple or complex depending on the tissues involved in the fusion.⁷ Simple syndactyly refers to cases in which fusion is limited only to soft tissue involvement, whereas complex syndactyly is when osseous or cartilaginous unions are present.⁸ Syndactyly can also be considered “complicated” when fusion is more extensive than simple side-to-side fusion. For example, cases are often referred to as complicated when there is the presence of additional phalangeal elements or abnormal tendons, muscles, or nerves in the webspace.⁹ Syndactyly associated with a syndrome, of which there are at least 28 associated syndromes, is also generally referred to as complicated.¹⁰ The treatment of syndactyly is surgical separation/reconstruction and techniques have continually been refined leading to ever-improving outcomes.¹¹

Evaluation of a patient with syndactyly should be comprehensive. In addition to a detailed hand examination with radiographs, a complete examination is necessary to detect additional anomalies if present. Surgical treatment is almost always indicated for functional and aesthetic reasons, but exceptions do exist.^12, 13 Most surgeons agree that surgery to separate the digits should commence at 12–18 months and be completed by the time the child attends school. However, there are instances in which earlier or later intervention should be considered.^12–15 For example, in cases of thumb-index syndactyly, separation should be done as early as practically feasible. 

The patient in this case presented with apical syndactyly without proximal fusion to the level of the commissure. However, given that webbing regresses in a distal-to-proximal fashion, it is more common for there to be proximal fusion. As such, syndactyly release most often necessitates commissure reconstruction following digital separation. 

The goals of syndactyly release are to generate a normal web space with a functional commissure, provide circumferential coverage of the released digits, and to improve the appearance of the hand. Traditionally, syndactyly release includes digital separation, the use of local flaps to close incisions and to reconstruct the commissure, and full-thickness skin grafts for additional coverage of areas unable to be closed primarily. However, many techniques for a graft-free closure have been described since Niranjan and DeCarpentier first described their novel method in 1990.^16–25 

In cases of mild syndactyly, it may be appropriate to forego a commissure flap and simply utilize a z-plasty to provide the patient with increased digital mobility and function.¹² There are many options at the surgeon’s disposal when the creation of a functional commissure necessitates utilization of a flap; however, the most commonly used flap is the above mentioned broad flap from the dorsum of the hand.¹⁰ Many other types of flaps have been used with success, and the reader can be directed to two excellent reviews by Braun et al. and M. Le Hanneur et al. for an in-depth discussion on different flaps that may be utilized.^10, 11 Of critical importance to the success of the operation, and of future operations, is the fact that each digit requires at least one functional digit artery and it is, therefore, necessary to keep detailed surgical records for reference should multiple operations be needed.¹³ 

The rate of complications associated with syndactyly release increases with the increasing complexity of the fusion(s).^26, 27 For example, simple syndactyly release often effectively generates functionally-independent digits, whereas complex syndactyly is associated with higher rates of contracture, scarring, and reoperation.^14, 28 The most common acute complication is superficial surgical site infection, with other common acute complications being flap/graft loss, delayed healing, and ischemia of recently separated digits.¹¹ With regards to long-term complications, the most common is distal migration of the web space, which is referred to as web creep.²⁹

Although syndactyly is one of the most common hand deformities, there are still unanswered questions regarding the ideal surgical approach to management. One of the largest outstanding debates is whether newer graft-free procedures should supplant more tried and true methods. However, the most recent high-quality evidence appears to favor the continued use of skin grafts over graft-less procedures.^30, 31 Despite this, there is an obvious benefit to graft-free procedures without the additional donor-site morbidity, and more evidence will be necessary to define the role that graft-free techniques will play in the future surgical management of syndactyly. 

Nothing to disclose.

The parents of the patient referred to in this video have given their informed consent for surgery to be filmed and were aware that information and images will be published online.