26 Congenital hand II

Disorders of formation (transverse and longitudinal arrest)

Synopsis

These are the most likely upper limb anomalies to be detected prenatally.

The conditions encompassed are divided into transverse and longitudinal arrest, although this division has little to do with either etiology or treatment.

Repeated observation of the child is the most useful evaluation of the functional capability of each upper limb, aided by the Great Ormond Street Ladder (see Fig. 26.1). This may demonstrate capabilities not noticed earlier due to development, achievement of milestones and progressive myelination of the peripheral nervous system.

Most of these conditions are static with changes largely related to growth or surgical intervention. Early surgical intervention is indicated where deformity is progressive, for primary skeletal realignment or where growth will produce skeletal malalignment.

Congenital transverse arrest

Key points 1

• Rare congenital abnormality

• Etiology may be sporadic or environmental

• Commonly occurs at level of upper arm or wrist

• Most transverse deformities will not require surgery. They may benefit from good quality prostheses for which they should be referred early.

Introduction

The birth of a disabled child is devastating for the parents. They will have many questions including those about the likely etiology of the condition. They may be looking for someone to blame. They frequently come with false hopes, encouraged by the media, about the possibilities of hand transplantation and stem cell technology. At this stage, the family may not be able to see beyond the child’s structural absence, to accept them as an individual in their own right.

The plastic surgeon may be able to assist in answering questions but, most importantly, they may act as a useful link to a disablement services team. This team of physiotherapist, occupational therapist, psychologist, prosthetist, orthotist and rehabilitation physician will be essential for the ongoing care of this child. They will help the parents accept their child and then, can look at ways of providing aids for the future. They may be able to put them in touch with other parents with children with similar disabilities or suggest parent run organizations which are specifically for the child with limb anomalies.

Occasionally, after full assessment by the rehabilitation team (Fig. 26.1), the plastic surgeon is asked to remove tissue/nubbins or make some surgical adjustment to the stump to make prosthesis fitting easier.

Fig. 26.1 The Great Ormond Street Ladder allows rapid assessment of upper limb function in complex cases.

Sometimes, the parents themselves request to have the apparently useless tissue on the terminal part of the limb removed. When left alone they become favored by the child and there is a later reluctance to have them removed.

History

Traditionally this condition has been termed “amelia” (although strictly speaking from the Greek melos meaning limb this means the complete absence of the limb), peromelia, transverse hemimelia, or congenital amputation.

Basic science/disease process

The level of transverse arrest is defined by the level of skeletal absence but there may be residual soft tissue beyond that point such as small nubbins. There are probably two main groups; those where there is a defect in limb formation and those where there is intrauterine amputation after limb formation.

Longitudinal development of a limb is dependent on the apical ectodermal ridge (AER). For the limb to fail to form, there has been an interruption in signalling with fibroblast growth factors (FGF 2, 4, or 8) to the progress zone which supports the AER, sometime in the period between week 5 and week 7 in utero, depending on the level of the transverse arrest.

With the exception of the teratogenic effect of thalidomide, etiological factors causing a failure of limb formation are largely unknown but may include genetic factors (there has been shown to be an autosomal recessive gene in Angora goats, which produces a deficiency of the distal limb segment ¹), chromosomal aberrations or environmental factors.

After limb formation, amniotic bands wrapped tightly around the limb, trauma producing a rupture of amnion or iatrogenic factors like laser ablation may produce an intrauterine loss.

Diagnosis/patient presentation

The patient presents with a congenital amputation (Fig. 26.2) which can occur at any level (humeral, proximal forearm, carpal or metacarpal). It may be bilateral – the left side is affected more at least twice as often as the right. Males are more commonly affected than females.

Fig. 26.2 Transverse arrest.

The diagnosis is usually straightforward at proximal levels but at the level of the carpus and metacarpals, there is frequently disagreement in terminology between transverse arrest and symbrachydactyly. Where there are distal nail elements or nail ghosts present on very short digital sacs, this represents symbrachydactyly but in the absence of these, the two conditions may be indistinguishable. If amniotic bands are present elsewhere, then the amputation is likely to be the result of a severely constricting band in utero. Rarely, a proximally situated amniotic band will have caused sufficient interruption to molecular signalling to create a distal hypoplasia which resembles a symbrachydactyly, with distal nail elements present. The management depends on the type of symbrachydactyly (Fig. 26.3).

Fig. 26.3 (A) Short finger type symbrachydactyly; (B) cleft hand type symbrachydactyly; (C) monodactylous type symbrachydactyly with free toe transfer; (D) peromelic type symbrachydactyly; (E) radiograph of peromelic symbrachydactyly.

From a treatment point of view, it makes no difference except where other limbs are affected, so the terminology is of academic interest only.

With the advent of fetoscopic laser ablation for twin to twin transfusion, an iatrogenic cause of intrauterine limb loss should be considered where there is a history of this procedure. The mechanism is probably via disruption of the amnion creating bands rather than by the laser itself.²

Patient selection, treatment/surgical technique and postoperative care

Transhumeral level

Options for treatment here are between different prostheses, starting with a passive prosthesis. As the child develops active function, the passive prosthesis is replaced with a body-powered cable-controlled or myoelectric prosthesis.

Forearm level

Any treatment is usually restricted to functional and cosmetic prosthetics. The Krukenberg procedure ³ has been used in this condition, particularly when bilateral, to provide a pincer grip between the two forearm bones. The interosseous membrane is extensively released and the defect skin grafted. This procedure has not been readily accepted by either surgeons or families because of the cosmetic deformity it creates in what is already an abnormal limb and is more appropriate in traumatic loss in adults where prostheses are unavailable and adaptation is more difficult.

Carpal level

Once again, prosthetics are the mainstay of management. From a surgical point of view, where there is sufficient carpus to be able to provide some intercarpal movement, a double free toe transfer may provide the ability to grip broader objects but is unlikely to be able provide a fine pincer movement due to the limited range of motion within the transfer. Inability to cup the palm, in the presence of a restricted motion distally in the toe transfers may limit the ability to provide a fine pinch.

Metacarpal level (symbrachydactyly)

Where all metacarpals are present, the simplest option is to deepen the first web to create some form of crude pinch (phalangization). However, although a simple procedure, the pinch is a crude lateral pinch, opposition is not possible and grasp is limited due to the poor span. There are two main alternative surgical options that may improve function further, each of which has a role and the decision to perform one rather than the other is frequently related to parental factors:

• Free phalangeal transfer (FPT) ± distraction augmentation manoplasty (DAM)

• Single or double free vascularized toe transfer.

Free phalangeal transfer may be done at any age but it is claimed, that to obtain near normal growth within the phalanx, this must be undertaken within the first 2 years of life. However, there is no substantial evidence to support this. In our experience, growth plates remain open even if transferred at up to 7 years of age. This procedure is only appropriate where there is a sufficiently large soft tissue envelope and does best where the metacarpals form a normal cascade rather than where the central metacarpals are more deficient, forming a V shape.

First, a pocket must be created by dividing the longitudinal fibrous bands that extend to the tip of the soft tissue nubbin from the flexor-extensor tendon confluence over the metacarpal head. It is only then that the true extent of the soft tissue envelope becomes apparent. The surgeon needs to be wary of those nubbins with a constricted base that will not provide sufficient width to accommodate a phalanx.

It is necessary to harvest a whole phalanx since a partial phalanx inserted into the pocket will be prone to resorption (Fig. 26.4A). The phalanx needs to be taken together with an intact periosteal envelope but the authors do not try to preserve the volar plate and collateral ligaments (Fig. 26.4B). The phalanx is inserted into the soft tissue envelope (Fig. 26.4C). The phalanx is sutured onto the flexor-extensor hood which covers the metacarpal head. The flexor/extensors are not divided. A single K-wire is passed through the phalanx and the centre of the metacarpal head. Four weeks later, this is removed and active and passive movement is encouraged in the new metacarpophalangeal (MCP) joints (Fig. 26.4D–F).

Fig. 26.4 (A,B) Free phalangeal transfer. Bone was harvested with periosteum intact; (C) bone was inserted into soft tissue pocket; (D,E) patients hand with symbrachydactyly post free phalangeal transfer; (F) range of passive motion post free phalangeal transfer.

The extensor and flexor tendons in the donor toe should not be sutured together but there is no consensus on how to deal with the toe donor site defect. It has been suggested that inserting an iliac crest bone graft to the toe at the time of harvest may limit the donor site defect in the longer term.

Distraction augmentation manoplasty is considered as a secondary procedure when the child is old enough to participate in the decision and comply with all that this involves. In our experience, 8 years old is the earliest age that this is likely. Not all patients undergo this stage and so results are in a highly selected group. For this to be successful, the length of the bone being distracted must be a minimum of 10 mm long, it must be stable on the metacarpal and, for the fingers, the range of motion in the MCP joints must be >60°. In the thumb, the carpometacarpal joint must be stable. A distraction frame is applied to the bone with two Kirschner (K) wires or threaded pins fixing each bone proximally and distally (Fig. 26.5A,B). A subperiosteal corticotomy is performed between the proximal and distal fixation points (Fig. 26.5C) and the bones are distracted by 4 mm. Postoperatively, distraction is begun after 1 week at 1 mm/day, with weekly radiographs to monitor progress (Fig. 26.6).

Fig. 26.5 (A,B) Application of fixator for distraction augmentation manoplasty. (C) Corticotomy prior to distraction.

Fig. 26.6 After distraction and ready for bone grafting.

Once the required soft tissue length is obtained, a further procedure is performed to bone graft the resultant defect with bone graft from the metatarsals, harvested subperiosteally (Fig. 26.7). This rapid soft tissue distraction differs from distraction osteogenesis (callotasis) in the rapidity of distraction and need for bone grafting into the sheath of osteoid that forms. Its advantage is the shorter time needed with the distractor in place in bone on which it may have a tenuous hold. Other authors⁴ have suggested that in children bone grafting is unnecessary but that has not been our experience where awaiting bone formation has increased the number of complications with failure of fixation and resulted in some loss of the initial length obtained.

Fig. 26.7 Bone grafting, post-distraction.

Free toe transfer is suitable in those cases where there are toes present that are suitable to harvest, the family will accept the loss of one or both second toes and there are no contraindications to microvascular tissue transfer. One or two toes may be transferred simultaneously in a single procedure or sequentially in two procedures. There is no known benefit in performing this surgery before the age of 2 years and most surgeons would prefer to do it later than this. The site at which the toes should be placed depends on the individual hand anomaly.

For the procedure, the hand must first be dissected out to find suitable tendons, nerves and vessels and decide on the length of these that is required from the donor. To approach the blood supply to the second toe it is easier to explore the first web, rather than trace the dorsal metatarsal artery on the dorsum of the foot. Here, it can be clearly seen if the toe has a dorsal or plantar dominant blood supply and the vessel can be dissected retrogradely, once identified, and its dominance established. Removal of the whole of the second metatarsal gives better access when dissecting the toe than leaving the base and also allows easy closure of the resultant cleft in the foot to leave an acceptable donor site. Ideally, there are two teams present so that one can close the foot, while the other proceeds with the transfer(s).

The toe is K-wired in place on the hand, tendon and nerve repairs are performed and microsurgical anastomosis of arteries and veins is carried out; the level of this and hence the size of the vessel is dependent on multiple factors but it is preferable to avoid the need for vein grafts but also to avoid too long a vessel that may kink and adversely affect flow.

After microsurgical anastomosis in the hand, the surgeon needs to take care to avoid tension in closure of the wounds and it is better to place a skin graft than accept tension that may compromise perfusion.

The free toe transfer needs to be monitored post-operatively and if there is sign of vascular compromise, may need urgent re-exploration.

Outcomes, prognosis, and complications

Prosthetics

If arrest is at the level of the upper arm, use of prostheses is frequent. If this is bilateral, the child may be disinclined to use prostheses and use the feet instead.

If the arrest is at the forearm level, prosthetic use is often limited to task-specific and cosmetic prostheses.

Free nonvascularized phalangeal transfer

Free nonvascularized phalangeal transfer for symbrachydactyly will have a poor outcome if:

1. There is inadequate space in the digital sac for the transferred proximal phalanx

2. If the transferred proximal phalanx is shortened to fit into the digital sac; it will be then be resorbed if the medullary cavity is exposed

3. If there is disruption to the periosteal covering on the proximal phalangeal transfer

4. If the transfer is sutured to divided flexor and extensor tendon, in other words, disruption of the dorsal hood, will lead to an imbalance between adjacent toes.

In terms of growth outcomes, it is often stated that the transfers should be undertaken below 18 months of age but in our series of over 100 free nonvascularized phalangeal transfers this did not prove to be the case and we found open epiphyses were maintained even in transfers up to the age of 7 years.⁵ It is impossible to comment on whether or not the growth plates close prematurely because in all the published series the numbers are simply not enough to make a reasonable assumption. The viability of non-vascularized phalangeal transfers is assured provided they have a periosteal covering and there is no tension in the digital sac.

Where the metacarpals are of equal length with a good soft tissue envelope, free phalangeal transfers remain quite stable and can achieve up to 90° of motion at the new “MCP joint.” However, with uneven lengths of metacarpals, the direct placement of free phalangeal transfers onto the metacarpal heads will often lead to angulatory deformity and subluxation.

Distraction augmentation manoplasty

The secondary phase of distraction augmentation manoplasty is difficult and is prone to complications with regard to pin tract infections. The rapid distraction is relatively straightforward provided that the proximal phalanges are large enough to accommodate two pins proximal to the osteotomy site and two pins distal to it. Trying to attempt to distract multiple digits simultaneously using the same pins and a single fixator tends to compromise one digit whereas multiple fixators may not be feasible because of their bulk.

With regard to the digits that are produced this are often thin and more prone to fracture, but the children concerned value the digits enormously (Fig. 26.8). From a functional point of view, they improve the control of the flat hand, span and grasp of large objects. Psychological benefit to these children is from having four digits of equal length which move well at the MP joints. It is important to understand that the MCP joints that are created by the nonvascularized phalangeal transfers do achieve up to 80° of motion frequently.

Fig. 26.8 (A–D) Results after distraction augmentation manoplasty.

Foot donor site (free phalangeal transfer)

Long-term follow-up is essential and it has become apparent to us recently that although the donor site in the toes initially shows surprisingly little deformity and looks satisfactory for up to 7 years, after 7 years very significant deformities can make themselves apparent. This is especially in terms of shortening, which only deteriorates in adolescence and functional issues related to shoe fitting may occur. These may result in toe amputation.

Bourke and Kay ⁶ utilize a dowel-shaped bone graft from the iliac crest, with its apophysis, to replace the proximal phalanx in the foot and this may well be a very sensible approach but requires long-term study to assess its efficacy.

Outcomes of free toe transfer

Survival of a free toe transfer is now >95% but there is a steep learning curve and initially up to 20% of cases need early re-exploration.

Three-quarters of the children will be expected to undergo secondary procedures including tenolysis and pulp debulking.⁷ Despite tenolysis, the active range of motion remains significantly less than the passive range although it appears better when the transfer is done in the older child.⁸ Recovery of protective sensation in the transferred digit is expected although, two-point discrimination and light touch sensation appear to recover better when the transfer is under the age of 8 years. The transfers are naturally incorporated into use, although their grip and pinch strength are less than on the normal side.⁹

The majority of children, when there has been appropriate counselling and discussion prior to surgery, have physical and psychological benefits from toe transfer (Fig. 26.9). Problems in the child may be anticipated where the parents are poorly adjusted to the hand anomaly.¹⁰