13.11 Congenital upper limb anomalies

The term congenital upper limb anomaly is used to describe all hand and upper limb abnormalities that arise as a result of an error of normal embryological development. This error can either be environmental or genetic in aetiology.

A good knowledge of these anomalies is important as not only can they have a profound impact on the functional and cosmetic condition of the child affected but they may also have important psychological consequences for both the child and parents. It is often the position of the surgeon to relay information regarding the aetiological and embryological basis for these disorders to the parents as well as to discuss the prognosis and possible management strategies.

These anomalies are common: they may be obvious at birth if severe or they may present when the child is older, becoming more apparent with growth. They are often very visible and identifiable as a result of this but equally many anomalies are minor and interfere little with upper limb function.

Most epidemiological studies regarding upper limb anomalies are based on relative frequency, as opposed to true incidence and prevalence rates. In a recent study in Western Australia, upper limb anomalies were reported in 1:506 live births but this reduced to 1:610 at the time of presentation due to neonatal or infant deaths perhaps with conditions related to the upper limb anomaly. Previous studies have reported an overall incidence of any congenital anomaly as 1:100–200 live births and as 10% of these were upper limb abnormalities, the incidence for upper limb anomalies was given as 1:1000–2000. Many upper limb problems are associated with non-musculoskeletal problems. There is no evidence that anomaly rates are higher in monozygotic rather than dizygotic twins but rates are higher in mothers who are either old or young and babies born both pre- and post-term (Box 13.11.1).

Upper limb anomalies can be the result of either a malformation or a deformation. A malformation is described as an abnormality of primary structural development whereas deformation is the result of secondary change in a part which was previously developing normally.

Whilst upper limb anomalies do occur in isolation, they may well be associated with other systemic disorders or syndromes. These associated conditions are often of more clinical importance to the health of the child than the musculoskeletal abnormality. It is therefore important to be aware of these disorders so that the patient is evaluated properly.

The aetiology of congenital upper limb anomalies is incompletely understood. The accepted classification of this group of anomalies is based on clinical diagnosis and according to our understanding of where and when the failure took place during fetal development. There is no good evidence to link congenital upper limb anomalies to specific environmental agents although the use of thalidomide was associated with phocomelia. Some studies have shown an association with the use of antiepileptic agents in the early gestational period. The causative environmental agent or genetic abnormality can impact upon development at various stages of fetal development and a specific insult may have a very different effect if it is given at different stages of development. Similarly, seemingly very different insults given at a specific stage of development can cause the same anomaly.

Overall, duplications and failures of differentiation and formation account for the majority of the upper limb anomalies identified.

The upper limb bud appears on the lateral aspect of the embryo 24h before the lower limb bud around 26 days postfertilization. There is then rapid progress with upper limb development and the process is complete by 8 weeks (Figure 13.11.1). Therefore it holds that congenital upper limb anomalies are most likely to occur during this short time period of development.

Three areas of signalling have been discovered which guide the development of the embryonic upper limb. Firstly, the apical ectodermal ridge (AER) which overlies the limb bud, guides the mesoderm to differentiate by the medium of fibroblast growth factors. Differentiation occurs in a proximal to distal direction; thereby the upper arm will differentiate prior to the forearm which develops prior to the hand. It is this mechanism that allows the webbed hand to develop by way of dorsal grooving and interdigital necrosis regulated by apoptosis (programmed cell death) separates the digits between weeks 7–8.

The second mechanism is the zone of polarizing activity (ZPA), located on the posterior aspect of the limb bud. This activity is mediated by the Sonic hedgehog (SHH) protein and its function is to signal radio–ulnar development and orientate the limb.

The final mechanism of upper limb embryonic development is through the Wingless-type (Wnt) signalling centre. This centre is located in the dorsal ectoderm and it controls dorsoventral differentiation and limb rotation by secreting factors that influence mesodermal development around week 7.

The HOX (homeobox containing) genes also play an important role in limb development as their genetic expression controls growth by regulating mesenchymal cell function.

Thus, any abnormality in the function of any of these mechanisms could result in a specific and possibly predictable upper limb anomaly; for example, failure of the AER can lead to a failure of distal limb development including syndactyly. In experimental situations, transplantation of the AER has led to duplication of the limb or the development of supernumerary digits.

By the end of week 5, the majority of the skeletal limb has differentiated, as well as the brachial plexus. More distal neurological branches are complete at the end of week 6, with musculature defined at the end of week 8.

Other systems are also developing between weeks 4–8 and therefore a more general embryological insult, genetic or environmental, can result in abnormalities elsewhere in the developing embryo. Specifically the gastrointestinal, cardiovascular, and neurological systems are all also developing rapidly at this time. Therefore it is important for the clinician to consider the possibility of a wider and potentially more clinically serious disorder than the musculoskeletal anomaly alone and to investigate and refer as appropriate.

Currently the most widely accepted classification for congenital upper limb anomalies is the Swanson classification which has been adopted by the International Federation of Surgical Societies of the Hand and known now as the IFSSH classification (see Table 13.11.1, and Chapter 13.13). It is based on the specific developmental failure and relies on clinical diagnosis of the anomaly.

Often, as shown in epidemiological studies, more than one anomaly may be present in more than one area of the limb and with this current embryological classification of upper limb anomalies it is not possible to classify all hand anomalies. For example, brachysyndactyly may fit in either of two categories, failure of formation and failure of differentiation.

Congenital pseudarthrosis of the clavicle is a rare condition. Less than 200 cases have been reported in the English literature.

The majority of cases are right sided and the common presentation is that of a painless, non-tender, and mobile mass at the centre of the clavicle identified soon after birth. The clavicle begins to ossify at 8 weeks and is the first bone to do so. It normally develops from two separate intramembranous centres of ossification which go on to unite. In pseudarthrosis of the clavicle this process fails due either to a mechanical or an environmental insult: it may be caused by an intrinsic primary failure of development or because of external compression. The two parts of the clavicle form a fibrous bridge which then goes onto develop into a true pseudarthrosis. Histologically, each clavicular end is capped with cartilage tissue and they are joined by dense fibrous or fibrocartilaginous tissue. Generally, radiographs show that the medial part of the clavicle sits anteriorly and superior to the lateral acromial section of the pseudarthrosis (Figure 13.11.2). A birth fracture is the most common differential diagnosis but the lack of callus formation over time excludes this diagnosis. Occasionally neurofibromatosis or cleidocranial dysostosis may be considered.

It is postulated that pressure from the subclavian artery which runs posterior to the clavicle on the right accounts for the fact that the right clavicle is much more commonly affected. In accordance with this theory, left-sided cases are found almost exclusively in individuals with dextrocardia or situs inversus.

There is usually no significant functional deficit of the shoulder. The natural history is not known as most reported cases have undergone operative treatment. The aesthetic appearance worsens with time as the pseudarthrosis becomes more prominent, tenting the skin on movement. There may be pain on certain activities or with compression.

The indications for treatment are often aesthetic and surgical treatment is usually advocated between the ages of 3–5 years. Treatment involves surgical excision of the pseudarthrosis, remembering that approximation of the bone ends followed by bone grafting and stable internal fixation is essential if union is to be achieved. Some authors emphasize the importance of maintaining the periosteal sleeve. Currently, plate and screw fixation is recommended. The major complication of this surgery is non-union but overall, reported union rates are high and the cosmetic appearance is improved.

This skeletal dysplasia affects the development of many bones, primarily those of membranous origin. As the name implies, the bones most significantly affected are the clavicles and the skull although there is also delayed ossification and underdevelopment of the pelvis (including the hips) and the spine. The clavicles can be hypoplastic or absent and in the skull, there is delayed closure of the cranial sutures and the fontanelles with maxillary hypoplasia and dental abnormalities (Figures 13.11.3 and 13.11.4).

Recently, genetic studies have concluded that the disorder is inherited in an autosomal dominant fashion with an increase in mutations of the CBFA1 gene located on the short arm of chromosome 6.

Clinically the patient has bilateral ‘drooping’ shoulders, often with the ability to oppose the shoulders anteriorly, due to the profound hypoplasia or absence of the clavicles. This can lead to difficulty with coordination of arm movements and a theoretical potential for brachial plexus injury. Abnormalities of the musculature can also occur depending on which part of the clavicle is deficient. If lateral, deltoid and trapezius muscles can be affected but if the medial end is affected problems with the pectoralis major and sternocleidomastoid muscles can occur.

Other associations include hypoplastic scapulae, hypoplasia of the iliac wings, joint laxity, and dislocations and abnormalities of hands and feet. The patient is often of short stature and he may walk with a Trendelenburg gait secondary to the associated coxa vara.

Management involves genetic testing and counselling. Specific orthopaedic intervention at the shoulder is only indicated if the hypoplastic ends of the clavicles compress the subclavian vessels or the brachial plexus or to prevent secondary complications of pressure on the overlying skin. Treatment is usually by excision of the hypoplastic clavicle. Craniofacial surgery and surgical correction of the concomitant coxa vara or scoliosis may be required.

A Sprengel deformity is the most common congenital malformation of the shoulder girdle. During normal embryological development the scapula arises opposite the lower cervical spine and in the third month of gestation it descends caudally to the thorax. Failure of this normal migration leads to a hypoplastic, undescended, and hence malpositioned scapula. Associated with this bony abnormality are abnormalities of the surrounding musculature: pectoralis major, trapezius, rhomboids, and latissimus dorsi may be hypoplastic, absent, or weak. A weak serratus anterior can lead to a winged scapula.

The condition is three times more common in males than females but it affects both left and right sides equally. It can occur sporadically but sometimes there is an autosomal dominant inheritance pattern.

Clinically there is an asymmetrical shoulder line (Figure 13.11.5). The scapula can sit up to 10cm more superiorly than normal as well as more medially. The inferior pole is medially rotated which in turn points the glenoid fossa inferiorly. Patients often complain most about a ‘lump’ in the web of the neck where the superior pole of the scapula bends anteriorly over the top of the thorax (Figure 13.11.6).

Movements of the glenohumeral joint are often normal but scapulothoracic movement is limited and thus there is a restriction of shoulder abduction (Figure 13.11.7). Rotation and forward flexion may also be limited.

The deformity can be classified in rudimentary terms (Table 13.11.1) and the more severe the deformity the greater the restriction in joint movement and the more likely there are to be associated developmental anomalies (Box 13.11.2).

An omovertebral connection is present in up to 50% of cases: this may consist of a fibrous, cartilaginous, or bony bar and it may contribute adversely to the cosmetic appearance.

Treatment for a Sprengel deformity is based on the severity of the functional loss and to some extent cosmesis. Passive stretching exercises are recommended in less severe cases to increase the range of movement and strengthen the surrounding muscles. If surgery is required it should be carried out before 8 years of age to reduce the risk of complications such as a brachial plexus neuropathy. Many of the operations described can leave an unsightly scar and therefore careful consideration should be given to the cosmetic benefits of such surgery. In mild cases, an extraperiosteal resection of the superior pole of the scapula and any associated omovertebral tissue may provide significant cosmetic improvement with little risk of morbidity.

In more severe cases, the aim of surgical treatment is to improve the range of functional abduction by relocating and repositioning the scapula and hence the glenoid. Several surgical options are essentially soft tissue releases involving resection of the omovertebral bone with division of the trapezius, rhomboids, levator scapula, and parascapular muscles from either their spinal or scapular origins. The muscles are then reattached via various suture techniques once the scapula has been brought distally. Another popular technique involves a vertical scapular osteotomy.

Phocomelia is rare but in such cases there is often glenoid aplasia as there is in amelia. The management is non-operative. Prosthetic limbs are not often a good functional solution.

In this uncommon condition, the glenoid is flat and shallow. It can be found in association with a malformed proximal humerus (which may be an aetiological factor) and may develop secondary to a neonatal brachial plexus lesion (see Chapter 13.12). Clinically the patient may complain of instability and/or dysfunction but often the condition is entirely asymptomatic. If the deformity is severe enough to cause loss of function, operative management involves a glenoplasty using iliac crest graft.

Glenoid dysplasia is often an isolated condition but it can be part of other more general conditions (Box 13.11.3).

Holt–Oram syndrome is an autosomal dominant condition resulting in a complex of cardiac defects and skeletal malformations. The genetic defect is in a transcription factor TBX5. All cases have abnormalities of the carpal bones and the most severe cases will have a phocomelia. In between, manifestations include a rotated, hypoplastic scapula with associated wrist and forearm problems (see Chapter 13.13).

Os acromiale is a disorder where there is a non-union between one, two, or all of the three normal ossification centres of the acromium with the rest of the scapula. The condition is not inherited (Box 13.11.4). It is often an incidental finding on plain radiographs but symptoms may be similar to those of subacromial impingement syndrome. Initial treatment is conservative but occasionally, surgical excision or fixation of the fragment is required and subacromial decompression may be necessary.

Congenital humerus varus is analogous to coxa vara. It may be due to medial epiphyseal damage of the humeral head. Often it is asymptomatic but severe cases demonstrate a limitation of abduction.

Humeral head retroversion develops in response to abnormal pressures on the shoulder: it is commonly associated with a neonatal brachial plexus palsy. Movements of abduction, external rotation, and adduction are limited. Treatment, if necessary, is by anterior capsular release. If the deformity and decreased function are severe, a proximal derotation osteotomy can be performed but only after careful assessment of shoulder congruity.

Poland’s syndrome is a sporadic, uncommon, unilateral congenital disorder characterized by underdevelopment or absence of the chest wall and scapula muscles and the breast tissue with associated rib cage defects and hand anomalies (see Chapter 13.13). Not all features need be present to constitute a diagnosis of Poland’s syndrome and subtle cases may be missed. Girls may present in puberty due to the unilateral failure of breast development.

Like congenital pseudarthrosis of the clavicle it is thought to arise from an abnormality in the development of the subclavian artery. Non-musculoskeletal manifestations of Poland’s syndrome include dextrocardia, diaphragmatic hernia, and gastrointestinal abnormalities.

Functional impairment in Poland’s syndrome is rare and surgical management is often primarily to improve appearance. Syndactyly is usually treated prior to school age.

Abnormalities of the elbow joint can be overlooked particularly in the patient with normal function in the joints above and below (the shoulder and wrist/hand) and when the elbow is essentially asymptomatic. Congenital disorders of the elbow can involve bone and joint or soft tissues.

Radial head subluxation or dislocation is the most frequently occurring congenital abnormality of the elbow; 60% of cases are bilateral. The pathology is thought to be due to a hypoplastic capitellum allowing the radius to dislocate. In about one-third of patients, there will be another anomaly elsewhere in the upper limb. The forearm is often hypoplastic, and the ulna may be short with a negative variance at the distal radioulnar joint. Acquired dislocations can occur in infancy. It is, however, the hypoplastic nature of the capitellum on radiography or arthrography or other imaging that help distinguish a congenitally dislocated radial head from an acquired one (Figure 13.11.8).

Congenital radial head dislocation often presents at ages 3–5 years. There is usually no functional loss of movement but clinically the patient may have reduced supination with an inability to achieve full extension. Pain or clicking is not usually a major feature but many patients or their parents notice a lump on the lateral side of the elbow.

Three types of isolated congenital dislocation are described: type 1 is the least frequently occurring, but is associated with pain (Table 13.11.2). Radial head dislocations can also be classified according to the direction of dislocation (Table 13.11.3). Radial head dislocation is associated with a variety of conditions: in some such as diaphyseal aclasis, the dislocation develops over time as a result of the abnormal forces that growth places on the developing forearm structures (Figure 13.11.9 and Box 13.11.6).

Management in most cases is to reassure and observe. Analgesia may be required. Surgical treatment is indicated when the patient has significant symptoms of pain. Occasionally, surgery is advised for deformity (with growth the dislocated radial head may become more obvious) and to try and improve movement if there is severe restriction.

Due to the hypoplastic capitellum and reciprocal changes in the radial head, relocation of the congenitally dislocated radial head is not a very successful option. For acquired dislocations, most frequently seen secondary to a missed or late diagnosis of a Monteggia fracture dislocation of the forearm, relocation of the radial head is advisable and usually successful. This involves an open reduction of the joint in combination with a reconstruction of the annular ligament with a triceps fascial sling and an ulnar osteotomy to restore length and correct the bowing deformity.

Excision of the congenitally dislocated radial head invariably reduces symptoms of pain but it is less likely to improve the patient’s range of movement. This can be performed safely at any age if symptoms are severe (Box 13.11.7).

Classically, the exostoses around the distal ulna lead to differential growth rates in the foream bones. The ulna is short and the radius becomes progressively bowed leading to radial head dislocation in a significant number of cases (see Figure 13.11.9). Surgery designed to prevent this complication has been advised. This involves excision of the prominent exostoses, correction of the radial deformity and lengthening of the short ulna. Whilst this approach may keep the radial head in joint, it risks decreased function due to an increase in forearm stiffness with further limitation of pronation/supination.

This abnormality is a congenital osseous or fibrous union between the radius and ulna. It is generally sporadic but occasionally autosomal dominant inheritance can occur with incomplete penetrance and variable expression. It is a rare disorder demonstrating an equal sex distribution.

During the sixth week of gestation, the cartilage anlage of the humerus, ulna, and radius starts to separate. An abnormality in this separation can cause a synostosis to occur. The union may be complete or more commonly partial. Over half of patients will have bilateral synostoses. The most common site for partial synostosis is the proximal radius and ulna and the proximal radius is often hypoplastic. Radioulnar synostosis is associated with a large range of limb and other congenital anomalies and some syndromes.

The clinical problem is loss of forearm rotation but presentation may not be until late childhood. There is usually a fixed pronation position that most patients adapt to by extending their range of movement at the radiocarpal joint so that, overall, there is little functional loss. There is no association between forearm position and level of the synostosis or between forearm position and function. The condition has been classified into four types (Table 13.11.4 and Figure 13.11.10).

Indications for operative treatment usually include bilateral synostoses with a severe degree of functional loss and fixed pronation deformity of both forearms. The shoulder and wrist joints can compensate, to a certain extent, for loss of forearm supination and pronation. If required, a derotational osteotomy is performed designed to improve the fixed forearm position: attempts to restore range of movement by excision of the synostosis and/or silastic or tissue interposition have been unsuccessful. Even in bilateral cases, a position of 10–20 degrees pronation is usually preferred although an individual decision may be required to take into account particular cultural or social requirements. Although various osteotomy levels have been described, some have a high complication rate and simple methods are often the most reliable. Vascular compromise is a particular risk if the correction is greater than 45 degrees.

Congenital pseudarthrosis most commonly affects the tibia but it has been documented in all the long bones. In the forearm, the ulna is more frequently affected. The reported incidence of associated neurofibromatosis is higher with forearm pseudarthrosis than with tibial pseudarthrosis. As with tibial pseudarthrosis, surgical management is often required but frequently fraught with difficulties. The use of a vascularized fibula graft is perhaps the most popular and successful technique reported but in severe cases the creation of a single bone forearm may be most realistic solution.