Congenital hand II

26 Congenital hand II


Disorders of formation (transverse and longitudinal arrest)






Congenital transverse arrest





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.



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.





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.



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).



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




Forearm level


Any treatment is usually restricted to functional and cosmetic prosthetics. The Krukenberg procedure3 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.




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 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).



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).




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.



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




Free nonvascularized phalangeal transfer


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



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.





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



The donor site morbidity from free toe transfer depends on which toe is chosen and the number of toes taken from each foot. The authors do not harvest more than one toe from each foot where the foot is to be preserved. Their preference is the second toe transfer because, after closure of the defect as a ray amputation, this provides an excellent aesthetic and functional foot, particularly if the harvest is bilateral. Gait does not appear to be affected in the long term.





Phocomelia







Basic science/disease process


Although phocomelia is mainly sporadic, there are some problems with the same underlying genetic basis which produce four limb abnormalities which may be phocomelic. This includes Roberts syndrome, which is caused by mutation in the ESCO2 gene on chromosome 8, inherited in an autosomal recessive fashion.12 The ESCO2 genes are important in producing the ESCO protein product required for attachment of sister chromatid cohesion during S phases to allow chromosomal separation during cell divisions. In Roberts syndrome, the protein is abnormal so the chromatids attach poorly and cell division is delayed.


Phocomelia has been mimicked in chick limb buds by exposure to X-irradiation. It was thought that this caused a patterning defect as the cell’s identity was determined by its time spent in the progress zone. More recently, research has suggested that both thalidomide and X-irradiation cause defects due to a time-dependent loss of skeletal progenitors which do not survive or differentiate.13 It is known that antiangiogenic analogues of thalidomide induce chick limb defects. It is likely that thalidomide prevents angiogenesis and this would be expected to cause upstream changes in limb morphogenesis.14



Diagnosis/patient presentation


There are three main types of phocomelia:



Both upper limbs are affected, although this may be to different degrees. When all four limbs are affected, the prognosis is more guarded. Phocomelia may be isolated or may be associated with other more serious congenital anomalies that may be the deciding factor in overall prognosis.


The clavicle and scapula may be abnormal in addition to the glenoid, which is hypoplastic. In type III, it may be difficult to distinguish between a severe radial or ulna longitudinal deficiency and phocomelia especially in cases with TAR syndrome who typically have extremely short forearms. Many have abnormalities proximal or distal to the segmental defects which suggest that those cases considered to be phocomelia may, in fact, fit better into a diagnosis of longitudinal dysplasia (Fig. 26.10).15



In Roberts syndrome, there are severely shortened segments of all limbs especially the forearms and lower legs. The upper limbs are usually more affected than the lower limbs. There may be knee and elbow contractures. There is not always the full complement of digits, and those present may be abnormal. There are facial dysmorphisms, including microcephaly hypertelorism, downward slanting palpebral fissures, micrognathia, cleft lip and palate, a beaked nose, and small nostrils. There may be cerebral, heart, kidney and genital anomalies. Overall, growth is slow pre and post natally and there is some intellectual impairment. SC phocomelia used to be thought to be a separate entity but is now considered to be a milder variant of Roberts syndrome.







Feb 21, 2016 | Posted by in General Surgery | Comments Off on Congenital hand II
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