Incidence, etiologies, and classification (Steven Hovius)

Congenital differences of the hand and upper extremity are an intriguing subspecialty of hand surgery, hand therapy, and hand rehabilitation. These differences are not common, with an estimated 175 to 200 per 100,000 live births, and they display a wide spectrum of malformations with or without associated congenital anomalies.

In the past decades, knowledge has expanded in the fields of genetics, embryology, and pathological embryology/pathological anatomy. This has led to the development of a new classification system based on this knowledge, the Oberg-Manske-Tonkin (OMT) classification, in order to better classify the differences, leading to improved communication among involved health care professionals. Also, there has been an increase in publications detailing activities of daily living of these children. They do remarkably well in daily life as they have learned to deal with their problems and adapt by using alternative methods. ^,

In several countries, it is recognized that these children need a multidisciplinary approach in tertiary centers, from specialized pediatricians, geneticists, rehabilitation physicians, hand therapists, and so on. Between 30% and 45% of these children have a syndrome that demands multiple consultations—for example, Fanconi’s anemia, for which early recognition is crucial.

The consequences and benefits of such a centralization are that a higher number of patients are assessed by experienced health professionals. In our study on radial polydactyly—together with the group from Hamburg—we have demonstrated that experienced surgeons, for instance, achieve better results.

As well as an increasing knowledge, publications with long-term follow-up of treatment of congenital differences have improved our understanding of outcomes obtained from different techniques. Although these are nearly all retrospective studies, they do provide directions, such as aiming to correct as much as possible in the first operation to get the best outcome. The learning curve is long, and knowing pathological anatomy helps in providing better results. Clearly, we need more prospective data. This is very difficult to obtain, as children have to be followed long-term.

The development of registries and the organization of multicenter studies are good first steps. Furthermore, approved patient (and/or parent) reported outcomes together with structured clinician reported outcomes at set time points will hopefully provide more evidence in the future.

Surgeons are influenced by their training, reading, and own experiences. In microsurgical centers, for instance, microsurgical interventions such as vascularized toe-transfers for children have provided a new concept of treatment for children with symbrachydactyly and radial longitudinal deficiency. ^,

The editor, Jin Bo Tang, has asked me to edit a chapter on congenital hand anomalies with an emphasis on controversies in treatment. My coauthors and I will focus on the difficult decision-making for those children with congenital anomalies in which no clear pathway has been established as detailed in Table 29.1 : whether they should be operated or not and, if so, what kind of operation is the best for the child.

These decisions remain difficult because evidence is lacking. We will address less fully the importance of the well-being of the child and parents or caretakers, the role of the child in its environment, and the interaction with the people around them. This is not because we do not think it is important, but it is not the scope of this chapter.

The format I have decided on is to choose eight subjects, each with a longer treatise from an experienced surgeon, and with subsequent comments or alternative treatments on each subject from other experienced surgeons. This chapter is not in any way a comprehensive text of congenital anomalies of the hand and upper extremity. Its intention is to provide some insight into how a number of experienced surgeons may differ in their approach to the management of this selection of anomalies, which they have treated over the years, often with great creativity. These subjects are (1) syndactyly; (2) radial polydactyly and triphalangeal thumb; (3) thumb hypoplasia; (4) symbrachydactyly; (5) cleft hand; (6) radial longitudinal deficiency; (7) arthrogryposis; and (8) overgrowth conditions.

The following is a synopsis of the chapter:

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  Syndactyly : whether to use skin grafts or not; the use of skin substitutes instead of skin grafts; the use of tissue distraction in complex syndactyly; and how to compare web creep

  
  
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  Radial polydactyly : the principles of treatment and the importance of alignment of the thumb. Triphalangeal thumb: a flowchart for treatment; a case for keeping the original “carpometacarpophalangeal 1” joint with shortening and rotation-abduction of the thumb versus “formal” pollicization for the five-fingered hand

  
  
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  Thumb hypoplasia : principles and alternative treatments; pollicization techniques and the alternative use of nonvascularized or vascularized metatarsals and joints

  
  
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  Symbrachydactyly : the indications for vascularized toe-transfers; what to do for hands with adactylies; the use of nonvascularized phalanges

  
  
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  Cleft hand : pathology; principles of treatment and alternative treatments

  
  
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  Radial longitudinal deficiency : three different ways of approaching this difficult subject

  
  
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  Arthrogryposis : arthrogryposis multiplex congenita and distal arthrogryposis are discussed with emphasis on elbow movement and wrist and finger management

  
  
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  Overgrowth conditions and medication : principles of treatment

Finally: It is a joy and privilege to help children with congenital hand and upper-extremity differences, even if we cannot make it perfect for them. The introduction continues with the fundamental keys in the first consultation, observation, and physical examination as well as anesthesia and timing by Marybeth Ezaki.

The first consultation, observation, physical examination, anesthesia, and timing (Marybeth Ezaki)

There are several keys in the first consultation and clinical examination of these patients:

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  Your first meeting with the family of a child with a limb anomaly is a big event for all of you.

  
  
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  The parents will have already researched you on the Internet. They will know your training, experience, and your reputation. You know nothing about them!

  
  
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  They will have found information on the baby’s condition on the web—and, most likely, will have been “aggressively misinformed.” Ask them what they have learned or have been told about the diagnosis. Then, you can correct and dispel what they have heard/learned (even if they were referred by their pediatrician). Tell them that they can rely on you and your team for accurate information.

  
  
• •
  

  Do not hesitate to touch the baby—pick the child up, cuddle it, and demonstrate to the family that you are comfortable with their child. Find something good to say about the baby and make sure to tell the parents/grandparents that the child is beautiful, cute, has lovely eyes, seems so bright…

  
  
• •
  

  Ask when the parents learned about the anomaly. Was it on prenatal ultrasound examination? At delivery? Is there a family history?

  
  
• •
  

  As you take the history and examine the child, ask if the parents have others to talk to about their child. Is the extended family supportive and caring?

You must be aware of the normal developmental milestones to accurately examine an infant. Observation is crucial. Is the child moving the neck and limbs normally? Don’t forget to look at the spine and lower limbs as well. Is the child neurologically intact? Is the child ignoring the part—either because it lacks sensation, or in the older child, because it does not want to display it? Is there bimanual activity, fine motor control, and a pinch and grasp pattern? Having toys or enticing objects available for the child to play with gives you an opportunity to observe motor and sensory function, active range of motion, and functional use patterns. I kept several small objects on a key ring—keychain ornaments, keys, toys with buttons that lit up or made a sound—all for reach or guided exploration. “Can you find the button on the little red frog? Push it and it will make a noise.” All these objects can be easily sanitized between children.

X-rays are often not helpful in the very young child—explain why it is best to wait and do them closer to 1 year of age.

When you have made your diagnosis, write it on a piece of paper and provide it to the parents. If you have handouts or printed information about the condition, provide it.

Leave the family with a plan, and if nothing needs to be done soon, tell them to come back when the baby is 1 year old. “We’ll get x-rays then.” Flag your system to send the family a reminder of this appointment. Give the family a way to get in touch with you. Tell them to send you a photo when the baby sits/holds a bottle or something to keep them in contact with you. Unless there is a neurological issue, the parents can expect the child to smile, sit up, crawl, walk, and talk on time. Unless there is something that requires urgent attention, strangulating amniotic band, for example, tell the parents that their job is to love the baby and make sure she grows to know how wonderful she is.

Surgery, when indicated, can and must wait for the safety window for anesthesia. I tell the parents that for surgery the child needs anesthesia, and that it is safest for the baby when the brain and the airway/lungs are more developed and larger. Show them that the baby’s airway is only as big around as his little finger. Any swelling or congestion makes breathing more difficult. Time makes it safer.

Parents also need to have reasonable expectations of what you can do. Most conditions are not “curable,” especially by surgery. Know that the degree of psychological pain that the parents/family may feel is not related to the severity of the condition. Simple syndactyly can be just as devastating as a major syndrome to many parents.

Always make sure the mother—and the family, especially in-laws—knows that there is nothing that she could have done to cause the condition, nor prevent it. And repeat it so that everyone clearly hears it. Expect tears and bring out the tissues! Maternal guilt is a powerful monster.

Make sure the family understands the importance of words—their baby will be introduced to its universe, and the family must help the baby assign names to everything in it. This includes the hand difference. To ignore it is just not reasonable, and the baby will wonder what is wrong with the parents if they do not name and talk about it.

I often tell the parents that the baby will give them many and more serious things to worry about during his or her childhood. The parents should know that they can call you to help run interference and that you will be an advocate for their child. This should include adaptive equipment and adaptive interfaces for sports, musical instruments, and so on.

Perhaps not at the first visit, but as school approaches, bring up school issues such as technology assistance, needing extra time for testing, and bullying. Especially bullying. If a hostile environment exists that precludes learning in a school situation, this constitutes harassment and is illegal under many disability laws. Gently asking a child who its best friend at school is would often reveal deeper problems. I offered and made many phone calls to principals and teachers on behalf of a patient who I found to need advocacy.

Offer support and let the parents know that you can introduce them to families of children with similar conditions—families who are navigating similar challenges. Lastly, promise to see the child yearly or more often as needed.

Classification

Syndactyly is classified as “simple” when involving skin only, complete when the whole of two fingers is connected, incomplete when the syndactyly is partial; “complex” when there is bony attachment between distal phalanges; and “complicated” when other anomalies are present in bone and soft tissues ( Fig. 29.1 ), such as in Apert syndrome.

Clinical presentation and types of syndactyly.

Surgical methods

Correction of a “simple” syndactyly is an exercise in skin management. There is a shortness of skin, best demonstrated to a family by measuring the circumference of two adjacent fingers, adding the two measurements together, and comparing this figure with that obtained from measuring the circumference of the same two fingers when held together, as in a syndactyly. The shortness of skin may be attended to by (1) transfer of skin from an area with excess skin; (2) defatting of flaps; (3) loose suturing; (4) skin grafting or skin graft replacements; and (5) soft-tissue distraction. In recent years, there has been a tendency to try to avoid skin grafting because of the possibility of donor site morbidity, failure to take of the graft, and increased time of surgery, although not all agree that avoidance of a skin graft is an important component of treatment.

Surgery of a “simple” syndactyly involves the creation of a web space, skin cover of the digits, and, in a complete syndactyly, reconstruction of nail folds/pulps. This presentation will, in the main, deal with my preferences for the web space and reasons for my choices.

Web space.

The characteristics of a normal web space are its inclination from the dorsum to the palmar aspect of the fingers, its contour, and its depth. The options for reconstruction are a dorsal rectangular flap with or without modifications, a palmar rectangular flap, or interdigitating V-flaps, one dorsally based and the other from the palm. Some have suggested advancing a dorsal rectangular flap on a dorsal vascular pedicle, having divided the skin connection proximally. Correct inclination is achieved with a dorsal rectangular flap. However, it is my observation that the normal stresses of daily use may play as important a role in re-creation of a normal inclination as the design of the web space. The web space contour is of an hourglass shape, which contributes to the achievement of finger abduction. The depth is, roughly, at the midpoint of a line drawn between the metacarpophalangeal (MP or MCP) and proximal interphalangeal (PIP) joints dorsally and the distal palmar crease (DPC) and PIP joint on the palmar side. When only one web space is involved, it is easy to base this position on the normal adjacent webs, placing it perhaps 2 mm proximal to its normal position.

I prefer a winged dorsal flap. The principle was introduced, to my knowledge, by Naranjan and De Carpentier in 1990, but was shown to me by Giele, who subsequently published his method. ^, I have introduced some modifications to the designs proposed by these authors. These are directed toward obtaining an optimal web space inclination, contour, and depth.

Lines are drawn from mid MP to mid PIP joints of the involved fingers, dorsally. The distal end of the flap is at a point two-thirds to three-fourths of the distance from the MP joint ( Fig. 29.2 A). (An incomplete syndactyly extending less than this distance dorsally may be treated with local flap transpositions rather than a specific dorsally designed flap.) The dorsal winged flap is designed as in ( Fig. 29.2 B).

(A) Dorsal lines from metacarpophalangeal (MP) to proximal interphalangeal joints with distal extent of flap two-thirds of the distance from the MP joint. (N.B. This figure is not of the same patient shown in Figs. 29.2 B to 29.2 F.)

(B) The dorsal winged flap. The distal end of the flap is mildly concave in shape with its two lateral points being a little distal to its center point. These extend laterally to the midpoint of the involved digits. Two triangles (wings) are drawn on each side of the dorsal flap with midpoints just distal to the midpoints of the dorsal longitudinal lines. The triangles reach the full lateral extent of the dorsum of each digit. Importantly, in my opinion, the triangular flaps must not have their distal bases as a direct continuation (extension) of the concave base of the dorsal flap, as this creates a continuity between the web space and the digits when the dorsal flap is inset at its base and leads to web creep.

(C) Siting of the web space depth. The mild convexity of the palmar basal incision matches the concavity of the dorsal flap.

(D) The lateral extensions of the web flap and its insertions recreate the hourglass shape of the web.

(E) Two palmar-based digital flaps prevent continuity of suture lines between the base of the web flap and the digits. Note that the digital flaps reach the midline of each digit.

(F) Dorsal scar lines from triangular flap elevation. The inset of the triangular flaps caters for the usual skin deficits. Note that the digital flaps reach the midline of each digit.

On the palmar side, the midpoint of a mildly convex base is placed at a point 2 mm proximal to the supposed position of a normal web base ( Fig. 29.2 C). The rectangular flap and web space are extensively defatted. The common digital artery bifurcation is usually proximal enough to allow maintenance of arterial flow to both digits. If it is too distal for insertion of the web flap, one or the other is divided after checking that the deprived digit remains viable. The common digital nerve bifurcation may be dissected proximally without loss of continuity. After insetting the base of the web flap, its shape and insertions re-create an hourglass contour ( Fig. 29.2 D).

Palmar based finger flaps are sutured to the palmar aspect of the triangular flaps. This prevents a continuity of suture line between the base of the web flap and the two finger flaps ( Fig. 29.2 E). In my opinion, this decreases any tendency to distal web creep (drag).

The two triangular (wing) flaps turn through 90 degrees plus from their original dorsal position, an area of excess skin, to cover the usual lateral deficit created in the reconstruction of a web space ( Fig. 29.2 F). These areas have previously been covered with skin grafts or skin graft replacements. It is most unusual for me to use skin grafts for a “simple” syndactyly, complete or incomplete. The disadvantage is that dorsal, transverse, donor site scars just distal to the MP joints of the fingers are more obvious ( Fig. 29.2 F).

Digital flaps and nail folds.

The interdigitating digital flaps extend from and to the finger midlines on dorsal and palmar sides of each digit ( Figs. 29.2 E and 29.2 F). These flaps are extensively but judiciously defatted before insetting. I have not seen long-term vascular compromise of these flaps.

I prefer the nail fold flaps of Buck-Gramcko distally ( Fig. 29.3 ). However, distraction may provide more skin for this purpose and a better nail fold, particularly for a “complex” syndactyly. For the latter, I divide the distal phalanges; the Buck-Gramcko flaps are elevated; and the skin deficit is grafted or left to heal secondarily. If needed, grafts are harvested from the ante-cubital fossa.

Buck-Gramcko nail fold flaps.

Web space position assessment.

Measurement of results of surgery is notoriously difficult in the pediatric population. This difficulty, particularly in the very young and uncooperative, and the time it consumes are reasons offered to excuse our failure to do so. I do not believe that we can sustain this excuse. We have a responsibility to inform families of objectively measured outcomes obtained through different techniques. Only in doing so can we justify these techniques.

Web space creep (drag) is the common complication of web space surgery for syndactyly release. Many suggested measurement methods of the web position have been offered, radiological and clinical, some via photography. All have some disadvantages in accuracy and consistency of documentation. The following method is offered as an alternative. It may be performed before and at the end of surgery while the child is under anesthesia. Time taken from surgical time is the complaint. Subsequently, comparison measurement of web position may be conducted in the clinic for an older and more cooperative child, or this can be performed at a time of an anesthesia for another procedure. Photographs of the hand after placement of digits, as in Fig. 29.4 , allows completion of the measurement in a shorter period of time on a cooperative photograph.

Assessment of the web position.

The hand is placed with its dorsum on a flat, firm surface. The web is fully and passively abducted without force. Axial lines are drawn on the palmar aspect of the two involved digits, crossing the midpoints of both. The abduction angle is documented. The midpoint of the web is marked. Perpendicular lines are drawn from this point to the axial lines. Distance A is the distance between the point at which the perpendicular line meets the axial line and the midpoint of the basal finger crease. Distance B is the distance between the midpoints of the most proximal of the basal finger creases and the most proximal of the PIP joint creases, along the axial line ( Fig. 29.4 ). (N.B. The distance A is measured differently from that described previously, as the current reference points of distance A differ from that description. The method of web position assessment remains the same.)

The web index is calculated in the following manner: ½ (A/B of one finger + A/B of the other finger). The web index will be zero when the web is at the level of the proximal basal finger crease, that is, A = 0 as for the ring finger on the right in Fig. 29.4 ; a negative value when the web is proximal to this point, as in clefting; and 1 when the web is at the level of the proximal PIP joint crease (both A and B =1), increasing when the web is distal to this point.

Measurement of web creep (drag) may be assessed by comparison of the current web position with the immediate postoperative measurement. Although this method of web position measurement has flaws, the result of applying this process may well be that of a common approach to the web of a “simple” syndactyly.

Comments and alternatives in treating syndactyly

1. The use of skin grafts in syndactyly repair (Daniel Weber).

Michael Tonkin points out that correction of syndactyly is an “exercise in skin management” and explains his preference for separating simple syndactylies, complete or incomplete, without skin grafts. Although several case series have documented the feasibility of graftless techniques, there are only a few comparative studies with grafted procedures. Whereas Ferrari et al found no differences regarding surgical outcome and patient satisfaction, Yuan and Wang found better aesthetic outcomes with the use of grafts, the latter in a prospective study with bilateral surgeries, comparing skin graft versus graftless techniques in the same patient.

Skin grafting compensates for the skin shortage that is always associated with syndactylies, and it allows tension-free positioning of the flaps in a natural-looking web space. This advantage must be balanced against donor site morbidity, the potential mismatch in color or texture of the donor skin, and the associated risks of loss of the skin graft, usually associated with infection.

Donor sites.

A retroauricular full-thickness skin graft (FTSG) is suitable for hands and is large enough to cover defects for two web space repairs. It is important that one-third of the skin be harvested from the ear and two-thirds from retroauricular so that the scar retracts in the ear fold ( Fig. 29.5 ). Subcutaneous infiltration with a local anesthetic of 1:100,000 concentration of adrenaline with lidocaine facilitates harvesting and prevents bleeding. Intracutaneous suturing with running, resorbable sutures usually results in inconspicuous scars, although hypertrophic scars can occur as severe complication on rare occasions. Taking the retroauricular skin graft before draping and operating on the hand reduces tourniquet time.

Full thickness retroauricular skin graft.

A FTSG from the antecubital fossa or the ulnar-sided wrist crease are equally suitable for the hand and easy to harvest, but donor site scars are more obvious. FTSG can also be harvested from the submalleolar plantar instep area of the foot so that the gradational pigmentation of the darker skin toward the glabrous skin is included.

Traditionally, many surgeons used FTSG from the groin. However, this skin often turns darker and has a hyperpilosity, resulting in an inferior outcome when compared with retroauricular skin.

Skin grafting for syndactylies.

Fig. 29.6 shows my preferred method of skin grafting on proximal defects after syndactyly repair, which is based on the technique by D’Arcangelo and Gilbert. The defatted FTSGs are sutured under slight tension with resorbable 6-0 sutures; running sutures can be used to save time. A well-molded soft dressing and adhesive bandage protects the wound and prevents hematoma formation under the FTSG ( Fig. 29.7 ). The first dressing change is made after 2 to 3 weeks to avoid unnecessary manipulations on the child. By this time, the FTSG is usually fully integrated.

Repair of complete syndactyly with full-thickness skin graft: Left: intraoperative photographs; right: integration of skin graft after 3 months.

Proximal defects are covered with full-thickness skin graft, whereas small distal defects are left open to heal secondarily.

Skin grafts should be placed on well-vascularized tissue; otherwise, there is a risk of loss or delayed healing and hyperpigmentation. I therefore avoid skin grafting to distal defects on the fingers. Residual defects that result by loose suturing heal by secondary intention and result in a better remodeling on the nail folds.

Even simple complete syndactylies have a spectrum in which some have considerable skin shortage. Coverage with a FTSG or skin substitutes is an option in these cases and may result in a more natural-looking web space and prevent web creep.

2. Syndactyly release with skin substitutes (Lorenzo Garagnani).

The research on biomaterials and their clinical applications has led to advanced solutions for tissue healing promotion and enhancement. Among these, hyaluronic acid (HA)-based products have been developed. In 2014, we presented a novel technique for syndactyly release using an HA-based matrix scaffold (Hyalomatrix®, Anika, Bedford, MA, USA) to cover skin defects as an alternative to skin grafts. The product used is bi-layered, constituted of an ester of HA coupled with a semipermeable silicone membrane. A subsequent, independent series from another institution further confirmed and validated our outcomes. Other authors have also reported on their experience using different biomaterials. ^,

The main benefits of the HA matrix scaffold technique include (1) absence of donor site related morbidity, (2) absence of potential hair growth at puberty, (3) possibility to treat skin defects of any size and shape, (4) greater freedom to choose the preferred skin flap design and technique, (5) prevention of excessive tension on the skin flaps during closure as residual defects can be covered with the scaffold, (6) reduced surgical and anesthetic time compared with skin grafting, and (7) possibility to address unforeseen skin closure difficulties when using other techniques.

Surgical methods.

The technique I describe here is based on extensive experience with the procedure and the continued assessment of clinical outcomes. These have led to technical improvements over time. Preoperative flap planning is required. Any shape of dorsal flaps can be used in the web. If simple rectangular flaps are used in the web, we recommend creating additional small triangular flaps (one per side) from the palmar aspect of the web base for skin coverage of the lateral aspect of each digit’s base ( Fig. 29.8 A,B). This is to reduce the risk of postoperative hypergranulation and potential web creep in case of postoperative migration of the scaffold from the web base, as it can sometimes be difficult to secure firmly the scaffold to the web base. Multiple zigzag incisions are used to separate the digits, protecting the neurovascular bundles. Any skin defect area should be covered with a layer of subcutaneous tissue, creating subcutaneous flaps if required, before the scaffold application. The HA matrix layer is applied directly to the wound, whereas the silicone membrane is the outer layer. To achieve satisfactory skin healing, the scaffold should not be applied directly onto bare bone or bare tendon. The scaffold should be wider than the skin defect, and its edges should overlap the skin edges to reduce the risk of scaffold displacement and migration ( Fig. 29.9 ). Piercing the silicone membrane with a scalpel tip reduces the risk of hematoma. The scaffold is sutured in place using absorbable sutures ( Fig. 29.10 ). A bulky dressing is applied and left in place for three weeks. The skin sutures and the dressing need to firmly stabilize the scaffold to prevent its potential migration and displacement. At three weeks postoperatively, the dressing and the silicone component of the scaffold are removed, and wound healing is assessed. Any potential area of hypergranulation ( Fig. 29.11 ), where present, can be treated with either topical steroid cream or silver nitrate application.

Skin flaps. (A) Zigzag incision to separate digits, dorsal rectangular flap in web, palmar triangular flaps to cover lateral aspect of base of web. (B) Residual skin defects requiring coverage.

Correct hyaluronic acid matrix scaffold application to cover skin defects.

Hyaluronic acid matrix scaffold sutured to the underlying skin edges with absorbable sutures.

Syndactyly treated with hyaluronic acid matrix scaffold. Wound review three weeks postoperatively showing satisfactory wound healing, with a small area of hypergranulation over the little finger.

Indications.

Simple syndactyly is the main indication, but I also use this technique for some complex and complicated syndactylies, when sufficient subcutaneous tissue is present for a tension-free coverage of bare bone or tendon before scaffold application. The use of appropriately designed flaps and combined techniques, including tissue expansion and progressive distraction, allow treatment of the most challenging cases. ^,

3. Use of distraction in complex syndactyly (Wiebke Hülsemann).

Transverse distraction is a very helpful technique in very narrow complex syndactylies, which would be difficult, if not impossible, to treat surgically using standard techniques. ^,

In 1996, we started with transverse distraction in Apert hands. The motivation was the lack of skin available in the last release of digits 3 and 4, with very little scarless tissue for pulp plasties. A modular fixator was placed on the finger from dorsal to palmar sides, through skin, tendon remnants, and bone. From 1996 to 2022, we treated 309 complex and complicated syndactylies using this technique, 200 of which were Apert syndrome patients. Since 2018, we have also used it for narrow complex syndactylies of the fourth and fifth fingers with very thin phalanges, but with good active mobility of the proximal interphalangeal (PIP) joints.

The results were convincing: The distal phalanges were broader, additional skin was available, the nail matrix was wider, and there was some skin for pulp plasties. Modeling of the fingertips was improved. A nice side effect was a better blood supply. This better blood supply was recognizable in clinically faster wound healing. Even fingers without bilateral arteries could be separated without ischemia.

This situation requires a modification in the assembly of the modular fixator. Instead of two dorsal-palmar pins through the distal phalanx, an axial Kirschner (K) wire is required to avoid bone burst, and K-wires instead of a pin with thread is used for the middle phalanx in order to not damage the tendons so severely ( Fig. 29.12 ). Results show a much better shape of distal phalanges with a nicer nail anlage and a good active range of motion (AROM) of the PIP joint. The preoperative AROM of the distal interphalangeal (DIP) joint cannot be measured in synostotic distal phalanges. Therefore we cannot evaluate if the DIP joint mobility was altered. Functionally, the DIP joint mobility is not so important. We noticed no tendon laceration in these cases ( Box 29.1 ).

In narrow complex syndactylies of the fourth and fifth finger the device has to be modified. (A) Preoperative. (B) A thin K-wire of 0.8 mm is installed from the fingertip into the distal and middle phalanx. (C, D) K-wires instead of pins with middle thread are inserted into the middle and distal phalanges from dorsal to palmar. The connecting rod is bent distally and fixed with the cubes onto the pins. (E) Nine months postop: symmetric shape of the distal phalanx of the little finger.

BOX 29.1

Syndactyly by Michael Tonkin

Classification: (See Fig. 29.1 ) 1. Simple-soft tissue connection only: a. Incomplete b. Complete 2. Complex- terminal bone connection 3. Complicated- e.g. Apert syndrome

Treatment of simple and complex syndactylies: Usually by 18 months and includes creation of a web; digital flaps for skin cover; reconstruction of nail folds 1/2 separation of terminal phalanges.

Surgical options for the shortness of skin: Dorsal winged flap creates a web and transfers skin from an area of abundance to an area of lack of skin. Alternative options are skin grafts or skin graft substitutes. Transverse distraction separates terminal bone connections and provides skin for nail fold reconstruction. This may be applied also to Complicated syndactylies.

Complication: Web creep (may be measured objectively by the Web index) Excessive skin scarring

 

Definition

Radial polydactyly is described as thumb duplication, but the truth is that this is rarely a true duplication but, more usually, a sharing between two thumbs of the structures that together should make an individual normal thumb. This means that surgery to remove one of the thumbs will always leave the remaining thumb hypoplastic with some residual deficiency. The condition may be an isolated occurrence where it is unilateral, or as part of a syndrome or in association with split hand-split foot malformations where it may be bilateral. Occasionally, it is seen in association with Fanconi’s anemia, so a full examination of the child and testing for chromosome fragility is appropriate. In some cultures, or individuals, it may be inappropriate to intervene surgically.

Classification

The most used classification of radial polydactyly is that of Wassel as it is easily learned, being based on whether on x-ray the duplication arises within a bone or at joint level. However, it is a skewed classification with most of the cases being Type IV, is reliant on x-rays in a skeletally immature system reflecting the clinical appearance at surgery, which frequently they do not, and does not account for tendon anomalies, and many radial polydactyly cases do not fit into this classification. The later Rotterdam classification addresses many of these deficiencies and is much more useful but less easy to recall and less reliable for subtypes.

Clinical treatment

When deciding on surgical technique, a thorough clinical and radiological assessment of both duplicates is required, and this is completed intraoperatively. The interphalangeal (IP), MCP, and carpometacarpal (CMC) joints need to lie parallel to each other in two planes. Where they do not, there is likely to be tendon imbalance and may be a malalignment of the tendons. Depending on the age of the child, it may be possible to realign the insertions and the course of the tendons without osteotomies, but this is only possible in the youngest with the most minor of deviations; otherwise, osteotomies are required. With growth, an imbalance will become more obvious, and a malalignment will pull the thumb into a greater deformity. Even the most vestigial of duplications may need realignment of the insertion of the flexor in the dominant duplicate to avoid a z-deformity later. It has been shown that failure to align tendons leads to poorer results and a greater need for revision surgery. Both duplicates are assessed for joint stability, movement, alignment, size, and nail size and shape—usually, but not always, the ulnar is the dominant duplicate.

Surgical methods and technical tips

A variety of methods are used for reconstructing different forms of radial polydactyly:

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  Maintenance of the dominant duplicate with supplementation using structures from the lesser duplicate.

  
  
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  The Bilhaut-Cloquet procedure, where two similar deficient symmetric duplicates are combined side to side, with epiphyses level, to produce a single larger duplicate.

  
  
• 3.
  

  Modifications of the Bilhaut-Cloquet procedure, where only part of one duplicate is added to the other side to side (e.g., nail and distal phalanx).

  
  
• 4.
  

  On-top-plasty, where the duplicate with the good distal part but poor base (usually ulnar) is moved as a pedicled flap onto the base of the duplicate, which is poor distally but has a stable base.

The first method is overwhelmingly the one I employ, and the others are used only when I cannot produce an adequate thumb with this method. The results of these alternative methods, in my hands, are not as good, but I use them for specific instances when both duplicates are poor, so, not surprisingly, the results are also disappointing.

The Bilhaut-Cloquet procedure produces a stiff, broad, weak thumb, often with a ridged nail, that usually needs later revision procedures. It requires perfectly symmetric duplicates, a rare occurrence. It may be appropriate for the divergent convergent Type IV thumbs that need multiple osteotomies that result in stiffness otherwise and risk re-deviation. The modifications have fewer nail issues but are inclined to deviation.

The on-top-plasty is technically difficult, and the ulnar duplicate usually has a shorter pedicle than needed, which requires greater shortening of the radial duplicate than ideal and difficulty in reattaching the extrinsic tendons deep to the single neurovascular pedicle.

I will detail my method for correcting the most common of thumb duplications, the Wassel Type IV, where the bifurcation is at the MCP joint. The age at which I reconstruct is dependent on the comorbidities of the patient, the age at which they present, the size of the patient, the size of the thumbs, and the complexity of the procedure I anticipate doing. Commonly, the child is between 11 and 24 months of age.

I perform a radial incision along the radial digit proximally from the base of metacarpal to a tennis racket extension distally around the nail. On the ulnar duplicate, this may extend into a Y distally palmarly and dorsally beyond the IP joint to access the extrinsic tendon insertions. I raise the skin flaps on palmar and dorsal sides until I can visualize the anatomy of the underlying tendons of both duplicates. On an extremely rare occasion, when I am uncertain which is the dominant duplicate, I will use zigzag incisions dorsally and palmarly to explore the tendons, but these leave much more noticeable scars with no additional advantage for the majority of cases.

I raise the abductor pollicis brevis from its insertion with a small periosteal extension to hold it by but to be excised once the tendon is reinserted. I raise it longitudinally from the distal two-thirds of the metacarpal.

Distally, I explore the tendon insertions and ensure they are central. If they are not, I use a periosteal elevator to raise the insertion until it lies centrally, supplemented by a suture if required. I check that the pull of the tendon is central, and if it is not, I will realign the tendon until it is, with supplementary osteotomies if needed. I look for signs of a pollex abductus and explore that and release it as required—some abnormal connections between the flexor and extensor tendons are simple short connections, and others are more extensive and complicated to reconstruct.

I assess whether the extrinsic tendons from the radial duplicate are needed for the ulnar duplicate. Frequently, the flexors form a Y-shape and impair flexion. I excise the ulnar duplicate flexor, taking care to ensure it does not catch on a pulley. Rarely, this may be needed for pulley reconstruction. I usually use the extensor from the ulnar duplicate to reconstruct the extensor hood.

With the help of image intensification, I decide on the amount of metacarpal head to be resected including the excess bulk on the shaft—sometimes the shape of the head makes this obvious, but I prefer to check radiologically to avoid prominent bone spikes on the shaft. In small children, I can do this with a blade or small osteotome; older children require a saw. I assess whether a closing wedge osteotomy of the neck of the metacarpal is required and whether more distal osteotomies are required. Where possible, I leave the periosteum intact on the shorter side to stabilize the bone. In young children, a PDS suture passed through bone may be sufficient to close the osteotomy. If not, I use a single 0.9 mm K-wire passed from distal to proximal and use this to stabilize the MCP joint at the same time ( Fig. 29.13 ).

A patient with thumb duplication. (A) preoperative x-ray finding; (B) dorsal view; (C) palmar view; (D) immediate postoperative view; (E) postoperative recovery.

I do not reconstruct the radial collateral ligament with an osteo-periosteal flap but will suture the capsule and reattach the abductor pollicis brevis tendon to the base of the proximal phalanx, excising the periosteal extension. If I am reconstructing a radial thumb, then I will consider maintaining an osteo-periosteal flap for the ulnar collateral ligament as the forces across this through life are significant and the additional bone that it forms, which is unattractive and problematic, on the radial side of the thumb is hidden in the first web on the ulnar side.

If an osteotomy is not needed or can be closed with a suture, then a K-wire is not needed across the joint. The extensor of the radial duplicate is used to recreate an extensor hood, and any excess is excised.

The skin is redraped, and any excess is excised so that the scar sits in the mid-axial line, respecting the border between glabrous and nonglabrous skin but favoring keeping palmar skin, which does not move or stretch so readily. Closure is with subcuticular sutures. A bulky soft dressing extending to the tip of the thumb is applied together with a Tubigrip sling. The dressing is changed after 3 weeks, and any K-wire removed after 6 weeks.

The child is then passed to my therapy team to encourage use of the thumb. They are followed up clinically and radiologically until skeletal maturity because slight imbalance will become evident with growth, and some problems are not apparent until the teenage years. Outcomes may appear different according to which system of evaluation is used, and functional and aesthetic outcomes may be better evaluated separately. Even the best results from reconstruction of radial polydactyly may experience problems with fatigue when tested repetitively in time-pressured situations, but most function effectively for everyday life.

Definition and etiology

Triphalangeal thumb (TPT) is defined as a thumb with three phalanges instead of two. This extra phalanx can vary from a small ossicle to a wedge-shaped middle phalanx to a fully developed phalanx. ^, The long finger-like thumb can be unilateral or bilateral with or without polydactyly or part of a syndrome (e.g., Holt Oram syndrome). Due to the shape of the middle phalanx, clinodactyly is often present. Muscles, tendons, ligaments, and joints of the thumb can be aberrant with resulting instability or stiffness. For example, two flexors and a very hypoplastic thenar musculature lead to an unstable MP joint. The first metacarpal is always longer and more specifically in patients with a dominant inheritance (chromosome 7q36). ^, Therefore the length of the triphalangeal thumb is a combination of both increased growth of the metacarpal and the length of the extra phalanx. The CMC joint is often less developed and less mobile, especially in the finger-like thumb.

Clinical presentation

In bilateral inherited cases, an extra ray or more can be present, varying from a full ray even with an extra CMC1 joint to only distal extra parts. Mostly, the ulnar “thumb” is the best developed. The extra thumbs are underdeveloped, often with syndactyly. Also, in these patients ulnar polydactyly with ulnar syndactyly can occur. In these patient groups, the deformity tends to increase in severity over generations.

In the nonopposable type, patients encounter difficulties with picking up small objects, writing, and the like. The strength of the thumbs in unoperated adults is 30% of normative data. These unoperated adults, however, score hand function as 7.7 using visual analogue scores (10 is excellent) but appearance as 2.2. These parents mostly visit the surgeon for correction of appearance of the thumb for their child. Although earlier reports advised against surgery, our results in combination with low complication rates prompted us to reconsider this advice, depending on the type of TPT. ^,

The prevalence varies from 1:16,000 to 1:25,000. Different classifications have been proposed, but the most used is described by Wood and depends on the shape of the extra phalanx: wedge, trapezoidal, or rectangular in form.

We have treated 131 patients with TPT (213 affected hands) from 1982 to 2016, with 148 operated hands in 225 procedures. Sixty-six percent of the operated patients had a dominant inherited anomaly. Our aim is to operate after one year of age and before children enter primary school in the Netherlands, which starts at four years of age.

Treatment

After many years of treating these children, we devised a treatment algorithm ( Fig. 29.14 ). If a radial polydactyly has a triphalangeal part at the MP joint, I opt for transposition and reconstruction as for a Wassel Type 4 thumb.

Flow chart for treatment of triphalangeal thumb. CMC, Carpometacarpal; DIPRAD, distal interphalangeal reduction and arthrodesis; FDS, flexor digitorum superficialis; MP, metacarpophalangeal; ROAMC, rotation osteotomy and abduction of the metacarpal.

Reproduced with permission from Hovius et al 2019.

If not, it is treated as a triphalangeal thumb. If a wedge-shaped middle phalanx is present, I would excise it in the young patient, together with release of the collateral ligament on the contracted side and tightening of the collateral ligament on the elongated side ( Fig. 29.15 ). This was present in 40% of patients. If the patient is older, a distal interphalangeal (DIP) joint arthrodesis is performed with reduction and alignment. If very incongruent joint surfaces are present, I opt for a reduction-arthrodesis.

Preferred technique on the removal of the additional phalanx with ligament reconstruction. (A) The skin is removed in elliptical fashion on the superfluous skin side, the ligament turned over, and the delta phalanx removed. (B) Subsequently a Z-plasty is performed on the contracted side with a release of the collateral ligament in a V to Y fashion. Finally, the collateral ligament is adjusted on the concave side and the skin closed. (C–F) Perioperative and postoperative images after this procedure.

Reproduced with permission from Hovius et al 2004.

If the middle phalanx is trapezoidal or fully developed, I always perform a reduction-arthrodesis at the DIP joint. The DIP joint shortening arthrodesis was performed in 60% of patients. I am not in favor of performing a shortening arthrodesis at the PIP joint, because the proximal phalanx tends to become too long and the new IP joint too distal. This contrasts with earlier reports. ^,

In addition, as the first metacarpal is longer (more often in a patient with a trapezoidal extra phalanx), a reduction-rotation-abduction osteotomy of the first metacarpal is performed, especially if the thumb is also positioned in the same plane as the fingers. This makes “opposition” easier. The CMC1 joint can be less developed or resembles more a CMC2 joint. The latter is less mobile but stable. In very young children, it is possible to perform an osteotomy by morselizing that specific part of the metacarpal within the periosteum.

In the five-fingered hand, I would not opt for a “formal” pollicization as the existing CMC1 joint is mostly more stable than in a pollicization, resulting in greater strength and stability ^, ( Fig. 29.16 ). A reduction-rotation-abduction osteotomy of the first metacarpal was performed in 50% of our patients. In the other 50%, the metacarpal was left alone or an epiphysiodesis was performed later, particularly when the thumb was in the near normal plane. In the opposable TPT, I would mostly refrain from operative treatment if the thumb is not too long or too deviated. Opposable TPTs are mostly not inherited in a dominant manner.

(A) At the metacarpal level, osteotomies are performed followed by rotation, abduction, and shortening at the midshaft. Also, K-wire and a cerclage wire were used (ROAMC). The skin is incised in a Y over the DIP joint; after incision of the extensor tendon and collateral ligaments, the middle phalanx is reduced substantially and the distal phalanx at its edge to prevent damaging nail growth. Fusion is accomplished with a cerclage wire and a K-wire. (B, C, D) Preoperative images of a patient with five-fingered hands. (E–F) Long-term follow-up after shortening at the DIP joint (DIPRAD) and rotation, abduction, and shortening osteotomy at the metacarpal level (ROAMC). DIP, Distal interphalangeal; DIPRAD, distal interphalangeal reduction and arthrodesis; ROAMC, rotation osteotomy and abduction of the metacarpal.

Reproduced with permission from Hovius et al, 2004.

Other procedures can be to reduce hypermobility at the already very mobile MP joint by performing a capsulorrhaphy and tightening of the volar plate or sesamoidesis, performed in nearly 25% of thumb reconstructions. This hypermobility becomes more apparent with shortening of the metacarpal. Additional procedures may be indicated—opposition plasties, mostly with a flexor digitorum superficialis of the ring finger in 20% of thumb reconstructions or widening of the first web, mostly with a five-Z-plasty in 13% of thumb reconstructions. ^{, ,}

Postoperatively, smaller children will be treated with a boxing glove splint for 6 weeks. If K-wires are used, which we always try to avoid, they will be removed at 6 weeks. A removable splint is then fitted for another 6 weeks. The splint is increasingly removed during these weeks.

Outcomes

Complications are very rare. We have not encountered skin problems or infections. In long-term follow-up (an average of 7 years postoperatively) of resection of the wedge-shaped extra phalanx, no pain or instability was encountered, 16% had residual deviation (range 15–25 degrees), and flexion was with a mean of 35 degrees at the interphalangeal joint. In the group of DIP reduction-arthrodesis, 30% had residual deviation (range 5–25 degrees), no instability nor nail deformities were encountered, and flexion at the remaining IP joint had a mean of 46 degrees (range 0–90 degrees).

The reduction at the DIP joints often resulted in fibrous union according to x-rays, but clinically none were unstable. Secondary operations were mainly opposition plasties: correction of hypermobile MP joints or late epiphysiodesis of the metacarpal.

Regarding “formal pollicization” versus DIP reduction-arthrodesis combined with reduction-rotation-abduction osteotomy of the first metacarpal, all the parameters of opposition strength, movement, and appearance were not in favor of pollicization. The numbers, however, of long-term results in this specific group are too small to produce real evidence. Patients at long-term follow-up were very happy with the change in appearance from VAS 2 to 7 (10 is excellent). The VAS hand function only improved 1 point to nearly 9; strength in the thumb improved from 30% to 65% compared to normative data after operation.

Current status and our suggestions

The triphalangeal thumb is rare, has a great variety in phenotype and can even present with one or more extra thumbs, and is longer when compared to the normal population, due to the extra phalanx and longer first metacarpal. The thumb strength is 30% of normal mainly because of loss of opposition and flexion power. However, a concern of abnormal appearance is the main reason for seeking treatment. Depending on the phenotype, the surgeon addresses either the wedge-shaped extra phalanx or the trapezoidal and full-length extra phalanx and the length of the metacarpal. Furthermore, the first web, opposition movement and strength, and the stability of the MP joint are considered. The flow chart shows our preferences for treatment. For the five-fingered hand, we do not favor pollicization. We are also not in favor of performing a PIP joint arthrodesis. In the long term, patients were satisfied with their hand function but far more with the improved appearance.

Comments and alternatives on radial polydactyly and triphalangeal thumb

2. Nonopposable triphalangeal thumb (Scott Oishi).

The nonopposable triphalangeal thumb (five-fingered hand) poses some unique challenges to function, including increased length, decreased first web space, and positioning in relation to the other fingers ( Fig. 29.17 ). In addition, the thenar muscles may be hypoplastic or absent, leading to further difficulties with function. Pollicization in these patients addresses each of the deficiencies well, using a procedure that has been very successful in patients with absent or severely hypoplastic thumbs.

Nonopposable five-fingered hand. (A) Dorsal view. (B) Palmar view. (C) X-ray findings.

Careful examination of the child often yields important clues in preoperative evaluation before pollicization. Not all children are good candidates for this procedure. Good candidates will have already attempted to pronate the radial digit and be supple at the IP joints ( Fig. 29.18 ). I do not perform any pollicization until the child is at least 18 months of age for various reasons, including potential anesthetic cognitive effects and the size of the finger. The incisions and positioning of the radial digit are similar to those used for index pollicization, as shown in Figs. 29.19 and 29.20 . Important considerations in these patients are the length of digit (i.e., how much metacarpal to remove) as well as careful evaluation of presence or absence of thenar muscles and interosseous muscles.

Pronation of the radial finger.

(A,B) Markings for pollicization. (C) After surgery.

(A,B) intraoperative positioning. (C) Radiograph 2 years after surgery showing good length, open physes in pollicized digit.

In the appropriate setting, pollicization of the radial digit not only can improve function but also can lead to a much more aesthetically pleasing hand, which is important for children with congenital upper limb differences. As in most procedures, proper patient selection is imperative to achieve the optimum result, a happy patient and family ( Box 29.2 ).

BOX 29.2

Radial Polydactyly by Steven Hovius

• 
  

  Classification:

  
  
  
  
  • 
    

    Wassel: Bone classification of radial polydactyly into 7 types, even numbers are at the joints starting distally ( Fig. 29.21 ).

    
    

    
    

    
    

    

    
    

    
    

    Types: I, bifid distal phalanx; II , duplicated distal phalanx; III , bifid proximal phalanx; IV , duplicated proximal phalanx (most common); V , bifid metacarpal; VI , duplicated metacarpal; and VII , triphalangia.

    
    
    
    
  • 
    

    Rotterdam: Based on Wassel, but also describing hypoplasia/floating, deviation, symphalangism, triphalangeal on different levels, triplication.

  
  
  
  
• 
  

  Timing: Surgery normally between 12-24 months old.

  
  
• 
  

  Principles:

  
  
  
  
  • 
    

    Decide which thumb should be kept, often the ulnar one is more developed.

    
    
  • 
    

    Do thorough clinical and radiological examination of the duplicates.

    
    
  • 
    

    Look meticulously at nail size and shape, size, alignment, joint stability, movement.

    
    
  • 
    

    “Make one thumb by using elements of both thumbs, do not simply excise one”.

    
    
  • 
    

    Preserve therefore tendons, ligaments, thenar muscles, and skin of the excised more hypoplastic thumb to align, balance and augment the residual thumb.

    
    
  • 
    

    The first operation is crucial for long term alignment, correct as much as possible on both soft tissues and bones at this moment.

    
    
  • 
    

    Always be aware and search for less obvious anatomical anomalies, like connections between the flexor and extensor tendons.

    
    
  • 
    

    Align articular surfaces as axial and as congruent as possible by transverse and longitudinal osteotomies.

    
    
  • 
    

    The (modified) Bilhaut technique is favoured by a number of surgeons, especially when both hypoplastic thumbs have approximately the same size, mainly when originating at the MCP joint. In this technique both sides of the duplicates are joined at the epiphyses as well as the nails. When the modified technique is used only part of one side is combined with the other side (see also subject Gill Smith and comments Michael Tonkin)

    
    
  • 
    

    Rarely an on top plasty is used where the good distal part is placed as a composite flap on the better proximal part of the other duplicate.

    
    
  • 
    

    Perform ligament reconstructions or releases if necessary, for alignment and stability.

    
    
  • 
    

    Balance tendons on both extensor and flexor sides distally, this prevents malalignment later on.

    
    
  • 
    

    Adjust skin cover as accurately as possible, bumps and indentations will stay visible.

    
    
  • 
    

    Although K-wires can be necessary, I try to avoid using them and use stitches to bone instead.

    
    
  • 
    

    Postoperative dressings should be meticulously applied and resistant to removal by the child.

  
  
  
  
• 
  

  Radial polydactyly at IP level Wassel Type II: ( Fig. 29.22 ).

  
  

  
  

  
  

  

  
  

  
  

  Surgical methods for Type II. From left to right, Type II polydactyly, removal of the radial-side digit and creation of a flap from radial skin as shown; the flap is raised and collateral ligament is sutured back to the ulnar side digit, and then skin closure. Check both flexor and extensor tendon balance, readjust when necessary.

  
  
  
  
• 
  

  Radial polydactyly at IP level Wassel Type IV: ( Fig. 29.23 ).

  
  

  
  

  
  

  

  
  

  
  

  Surgical methods for Type IV. From left to right, Type IV, resection of the radial-side thumb with preservation of radial collateral ligament and abductor pollicis brevis tendon with creation of a flap, reattachment of the abductor pollicis brevis tendon and collateral ligament to the retained ulnar thumb. From left to right, wedge osteotomy is necessary if there is bony deformity in the metacarpal or the proximal phalange. The collateral ligament and abductor pollicis brevis tendon are sutured to the ulnar thumb after phalanx of bony alignment through osteotomy and internal fixation with stitches or a fine K-wire. The drawing shows the acentral insertion of the tendons at the distal phalanx in a Wassel Type IV. When apparent at exploration correct it to a central insertion. Check both flexor and extensor tendon balance, readjust when necessary.

  
  
  
  
• 
  

  Outcomes: Are better when all anomalies are corrected in the first operation; if preoperatively the joint does not move (mostly IP joint) then it will often not move postoperatively; only long term outcomes will provide the real end result; always tell parents that secondary operations maybe necessary.

  
  
• 
  

  Complications in the long term:

  
  
  
  
  • 
    

    Possibilities are deviation at IP or MCP joint; instability at IP or MCP joint; stiffness at IP or MCP joint; nail or nail wall deformities; pulp deformities.

  
  

Classification

The hypoplastic thumb is classified within the OMT system as a failure of formation involving the radioulnar axis. When the radius is affected, the failure involves the whole of the upper limb. Hypoplastic thumb reconstruction has a poorer outcome in this instance than when the hand plate alone is involved.

Grading system

Blauth ^, developed a grading system based on Muller’s 1937 concept of an increasing severity of teratological insult affecting all soft tissues, bones, and joints of the thumb. Several modifications of this grading system have been offered since. The most used is that of Manske and McCarroll, which expands the grading into sub-grades to better describe an increasing number of anatomical deficiencies. This author considers this expansion to provide a significantly superior understanding and description of Muller’s concept. Unfortunately (to my mind), these authors moved some thumbs with a CMC joint to Grade 3, therefore altering the integrity of Blauth’s grading system in which the presence of a CMC joint is equated with a Grade 2 deficiency and its absence with a Grade 3 deficiency. My preference is to retain Blauth’s grading system but to incorporate the more precise anatomical descriptions of Manske and McCarroll within it ( Fig. 29.24 ).

Tonkin modification of the Blauth grading system, which maintains all thumbs with an intact carpometacarpal joint within Grade 2 and those without a carpometacarpal joint in Grade 3, while incorporating the more precise anatomical details of Manske and McCarroll.

Some wish to increase the number of sub-grades of Grade 3, mainly to cater to different methods of surgical management. I continue to consider a retained minimal metacarpal head within a floating digit that is connected to the hand by a skin bridge only, rather than within the hand itself, as a Grade 4 floating thumb. The skin bridge may be supplemented by one skin flap only. A smaller skin bridge may demand two flaps. I acknowledge the increasing sophistication of reconstructive procedures to retain five digits in Grade 3 and 4 thumbs and the reasons for their use. ^, However, the small amount of metacarpal head does not alter the function of the digit before or after reconstruction. If we sub-grade 3 and 4 thumbs according to surgical management—in this case, the possible use of two flaps instead of one—then we also need to add sub-grades for use of different opposition transfers, different collateral ligament reconstructions, and different first web releases in Grade 2 thumbs.

Clinical assessment

Regardless of the grading system one prefers, this remains a description of anatomical deficiency alone. It is not a measure of function, objectively or subjectively measured. Mende has developed a score to reflect the objective function of the hypoplastic thumb. Each anatomical deficiency and its severity are given a score. This allows an assessment of the functional characteristics of the thumb: size, shape, stability, mobility, and strength. Armed with such a score, we can compare the preoperative and postoperative thumb status, the results of different techniques (see below), and the results from different centers. An App, developed by Wee Lam (Edinburgh), Konrad Mende (Basel), and colleagues, will open the concept of a score to greater ease of use. Subjective parameters can be incorporated or measured separately.

Surgical techniques

It is not the intent of this text to compare all different techniques—rather, to touch on a few that cause some dissension among experienced practitioners. ^,

Comments and alternatives in treating thumb hypoplasia

1. Our experience of treating thumb hypoplasia (Shanlin Chen).

We should thank Michael Tonkin for his practical, proven clinical experience in the field of thumb hypoplasia. We believe that the content of the classification and treatment strategy is very objective and reasonable. We also agree that, despite progress in reconstructive surgery, index finger pollicization remains the recommended treatment for severe thumb hypoplasia, particularly for floating thumbs and absent thumbs.

Indications of surgery.

In general, the indications for index pollicization are well established, partly because the popularity of the procedure. Nevertheless, in both Eastern and Western culture, a five-digit hand has a natural advantage over a four-digit hand. Traditionally, doctors may favor index pollicization, but parents may wish to keep five fingers. For severe thumb hypoplasia, we inform the children’s parents that we have two options in our armamentarium, that is, pollicization or thumb reconstruction with a free metatarsal transfer, either vascularized or nonvascularized, and we explain in detail the merits of each method. When explaining the choice of thumb reconstruction, we tell the family the problems of donor site morbidity, multistage surgery, and perhaps a poorly functioning thumb. However, in our experience, about 90% of the family members still choose a five-digit hand even after they understand the advantages and disadvantages of both pollicization and reconstruction.

Times are changing, and various new social media platforms now play a significant role in patient referrals. In fact, most parents are in WeChat, a popular social media group in China, which they have formed themselves. These parents have consulted the literature themselves, exchanged ideas, and obtained long-term follow-up results from other children to determine their final choice.

After 10 years, the results of reconstructive surgery appear to have gained their trust. Based on our experience, we believe that the current grading system of thumb hypoplasia may need to be fine-tuned, but one that considers both the options of thumb reconstruction and pollicization. Our proposed grading system is largely based on our subjective experience, which would need to be further improved and verified by our peers.

Surgical treatment and influencing factors.

One factor that affects the outcome of treatment for severe thumb dysplasia is the presence or absence of a trapezium. We believe that this is not directly related to the severity of thumb dysplasia. Even with a floating thumb, there may be a hypoplastic trapezium. Preoperative palpation or MRI scans can help confirm this, as well as during surgery. If present, a good trapezium not only can allow a new CMC joint to be formed, but it is likely there are also abductor pollicis brevis (APL) and extensor pollicis brevis (EPB) attachments, which lay the foundation for a stable and mobile CMC joint after surgery ( Fig. 29.25 ). Also, this provides the possibility of restoring some degree of motion of the distal joints via tendon transfers. This is an area of active research within our department, and we hope to publish our results in the near future.

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