13.14 Management of the limb deficient child

Congenital limb deficiency is rare, with an overall incidence of 1:2000 live births. In 2005/2006, there were 95 new upper limb and 68 new lower limb referrals to United Kingdom Prosthetic Rehabilitation Centres. Upper limb congenital absence is commoner than lower limb absence with fingers, hands, and forearms most affected. The majority of children will develop coping strategies to deal with their deficiency with many benefiting from prostheses or appliances and a few from surgical intervention. In 2005/2006, only 17% of congenital abnormalities required a surgical amputation, the majority of which involved the lower limb. These procedures usually aid prosthetic fitting or improve cosmetic appearance. Sometimes limb lengthening and/or reconstruction procedures must be considered.

Limb development begins during the fourth week after fertilization. Thickening of the lateral plate mesoderm occurs opposite the cervicothoracic and lumbosacral segments. The overlying ectoderm differentiates into a ridge known as the apical ectodermal ridge (AER). This controls the proximodistal limb growth by keeping the cells beneath the ridge in a continuous proliferating state. As the limb grows away from the trunk these cells stabilize and differentiate. The femur and humerus are both patterned before cell differentiation; however, formation of the remaining bones and digits depends upon the AER. The lower limb lags behind the upper limb by 1–2 days.

Further control of development in an anteroposterior direction (radial to ulnar) is by the zone of polarizing activity (ZPA), a small area of mesoderm along the posterior border of the limb. The limb development from the dorsal to ventral surface is controlled by the dorsal ectoderm. Ossification begins around the seventh week with vascular invasion and creation of the primary ossification centres within the cartilage anlage model by the process of endochondral ossification.

Control of limb development involves factors such as fibroblast growth factors (FGF)-4 and -8. FGF-4 is present after the AER has been induced; FGF-8 is present before and therefore may be involved in the initiation process. Overexpression of FGF-8 in chick embryos has resulted in limb anomalies: truncations, deletions, and extra digits. The action of the ZPA is related to a protein produced by the sonic hedgehog gene (SHH). Other genes involved include the Wnt-7a, that controls dorsoventral development, and the Hox (homeobox containing) genes that influence proximodistal and anteroposterior patterning.

The majority of limb defects are unilateral and sporadic. In 60–70% of cases the cause is unknown. Some are associated with known genetic changes resulting in specific syndromes (Table 13.14.1). Chromosomal abnormalities can lead to limb deficiency, for example, trisomy 18 may be associated with a central ray deficiency. Maternal drug ingestion, including both alcohol and smoking, during the first trimester can lead to limb anomalies. In the recent past, thalidomide, prescribed as an antiemetic, resulted in severe multiple limb deficiencies.

Vascular disruption at a critical stage of limb development can result in birth defects. Poland’s syndrome presents with unilateral absence of the sternocostal head of pectoralis major muscle, ipsilateral hypoplasia (or absence) of the breast with absence or hypoplasia of the fingers, hand, and occasionally the forearm. It is hypothesized that these deficiencies occur following an interruption of the early embryonic blood supply in the subclavian, vertebral, and/or branch arteries.

True intrauterine amputation in association with amniotic bands is very uncommon. The amnion becomes disrupted resulting in mesenchymal tissue developing fine hair-like structures that wrap around the limbs resulting in amputation or a constriction requiring emergency release soon after delivery.

Traditionally surgical classifications describe the affected bone and its deficiency, for example fibula hemimelia and proximal femoral focal deficiency (PFFD). While these remain convenient terms for clinical practice, the accepted classification is the International Standards Organization’s Method of Describing Limb Deficiencies at Birth (ISO 8548-1, 1989). The system describes the skeletal element deficiency as either transverse or longitudinal.

The birth of a child with congenital limb deficiency is a cause of great anxiety to the family. They require support along with adequate explanation of the condition and its management and with reassurance that experts are available for advice and assistance. Information given to parents and family should be accurate and avoid unrealistic expectations and if an antenatal diagnosis has been made on fetal ultrasound, an early referral to a Prosthetic Rehabilitation Centre could be considered.

Provided there are no associated congenital abnormalities, these children are expected to develop normally until they are old enough to compare themselves to their peers. The lifelong management of patients with congenital limb deficiencies may involve different professional disciplines at different stages. The emphasis of management is on the needs of the child and thus as the needs change with growth from childhood to adulthood so does the management. Good liaison between the Paediatric Services, Limb Deficiency and Prosthetic Clinics, and the orthopaedic or plastic surgeons is vital. Combined clinics are recommended to facilitate management plans.

The child with a limb deficiency requires a multidisciplinary approach for both the child’s clinical condition and the psychological support for the family. In the lower limb, our treatment algorithm (Figure 13.14.3) always raises the question of possible limb reconstruction. For the lower limb, the aim is that at skeletal maturity, the legs will be of equal length with a stable foot and good, pain-free function. Upper limb reconstruction may involve procedures such as pollicization in cases of absent thumbs, carpal centralization in radial hemimelia, or ulna lengthening in ulna hemimelia to provide support for the carpus. (For further details see Chapter 13.13.)

In cases where limb reconstruction is considered unachievable, treatment concentrates on providing support and improving function. This may consist of simple advice, appliances (e.g. to hold cutlery), orthotics, or prostheses. Surgical intervention is indicated in only a minority of cases. Procedures are performed for cosmesis or to improve prosthetic fitting, the latter by removal of obstructing appendages (Syme’s disarticulation) or correction of deformity (lateral femoral hypoplasia creating genu valgum or significant tibial bowing in complete fibula absence).

In the growing child, the optimal level for a surgical amputation is a disarticulation (or a ‘through joint’ amputation).This reduces the risk of bone overgrowth: a common complication of diaphyseal amputations particularly with transtibial or transhumeral levels where the growing end of the bone is retained in the residual limb. The overgrowth can result in pain, bursa formation, and skin ulceration often requiring surgical revision. Through joint amputation or disarticulation also offers a larger end-bearing surface and better proprioreceptive properties. The malleolar or condylar flare also aids suspension and rotational control of the prosthesis.

Transverse radial deficiency is the commonest level of congenital limb loss in children (see Figure 13.14.1). The management is prosthetic replacement, as part of an overall rehabilitation programme, with virtually no place for surgical intervention. As children are generally likely to benefit from prostheses, they should be introduced to them early. This allows the child to learn and make valid choices, based on personal experience. However, many children prefer not to use any prostheses at all, or opt to use it part time for specific tasks or for cosmetic purposes.

The rehabilitation programme starts with a simple cosmetic arm (Figure 13.14.4) first provided when independent sitting balance is achieved at 6 months. A functioning prosthesis, either body powered (Figure 13.14.5) or with electric controls (Figure 13.14.6) can be introduced at 18–24 months of age, when the child is better established with walking. The first powered prostheses use switch controls incorporated in a shoulder loop. Later, surface electrodes are used to pick up signals from extensor and flexor muscles for opening and closing myoelectric hands. The increased weight of these prostheses may limit their use in younger children. With increasing maturity (and as required) more complicated control mechanisms and additional tasks can be added to the limb. A specialist occupational therapist is crucial in training the patient how to use the limb and for advice on the use of other appliances, aids or ‘gadgets’ and how to manage one-handed activities.

Prostheses for more proximal levels of limb deficiencies (through elbow or transhumeral) are appreciably more difficult to use because of the need to control the prosthetic elbow. A figure-of-eight harness is required for suspension and control and the electric prostheses are heavy. ‘Hybrid’ prostheses may be required. Many patients opt for a passive function or cosmetic prosthesis and even those who have a functioning prosthesis often use them simply as a cosmetic arm. A comprehensive review of the literature over the past 25 years showed that there is a rejection rate of 45% in body-powered and 35% in myoelectric prostheses in children, although, worldwide, a wide variance is reported.

Children with distal limb loss (partial hand or transcarpal), if unilateral, generally function very well without active prosthetic intervention. However ‘appliances’ or orthoses in the form of simple leather gauntlets with pockets to hold cutlery or cup sockets for cycle handle bars or other activities need to be considered as part of the rehabilitation and management. Recently, myoelectric prostheses have been made available for transcarpal or partial hand levels of limb loss.

These deficiencies are less common and tend to be bilateral. They sometimes occur as part of various syndromes, for example VATER (vertebral defects, imperforate anus, tracheo-oesophageal fistula, radial and renal dysplasia), Holt–Oram syndrome, Fanconi syndrome, TAR (thrombocytopaenia and absent radius) syndrome, etc. (see Table 13.14.1).

Unlike transverse deficiencies, surgical reconstruction has a major role in maintaining optimum hand function in longitudinal limb deficiencies (Box 13.14.1). Radial longitudinal deficiency is commoner than ulnar longitudinal deficiency. Centralization of the hand or ‘radialization’ have been recommended but results are not always encouraging in the long term. Pollicization is generally recommended after these procedures to establish pinch grip. However these procedures are contraindicated in the presence of severe restriction of elbow function because the repositioned hand is unable to reach the face.

Longitudinal ulnar deficiency is associated with variable degrees of deficiencies in the hand on the ulnar side. The radius is short and associated with a functionless elbow and possible fusion of the radius with the humerus. Function is often better than expected. Various surgical procedures have been attempted but radical surgery is best avoided. Function is assisted by use of various aids, appliances, and other forms of orthoses.

Congenital deficiencies in the hand may be an absence of the thumb, central hand deficiency (cleft hand), syndactyly, or absence of a number of digits.

Cleft hand function is usually good without surgery and syndactyly can be released if felt appropriate. With severe finger deficiencies, reconstruction or rarely finger prostheses are used to provide a pinch grip.

Transverse lower limb deficiencies are rare and surgical intervention is usually unnecessary. This type of limb loss is managed with a prosthesis, just like an acquired amputation at the same level. When limb loss is unilateral, they are well tolerated with good function.

For forefoot absence or complete metatarsal loss, a total contact silicone prosthetic foot may be provided. If the residual limb is hypoplastic or there is a Chopart-type amputation (partial tarsal) additional support will be required above the ankle such as a plastic or leather bootee with an ankle–foot orthosis. Alternatively, a Syme’s disarticulation may be indicated with an appropriate appliance and later the possibility of revising this to a standard transtibial prosthesis. Total absence of the foot will require similar prostheses. A Syme’s appliance in children does not have the same problem of poor cosmesis as for adults, because as the child grows, the malleoli tend to be hypoplastic and a standard below knee prostheses can be used.

Transverse limb loss at a higher level requires a standard lower limb prosthesis to compensate for the partial or complete tibial deficiency or the partial femoral loss (Figure 13.14.7). Treatment should start when the child begins to show signs of standing independently. For above knee levels, the introduction of a flexible knee unit may need to be delayed. Unilateral complete absence of the lower limb is worth treating with a prosthesis but the prosthetic socket encompasses both hips and presents practical problems in daily living. Regular follow-up is essential to allow modifications or replacement to the prostheses to accommodate for growth.

This is the most common congenital lower limb deficiency. The diagnosis covers a spectrum of limb deformities often involving proximal and distal anomalies both in the femur and in the foot, such as tarsal coalition and absence of the lateral ray. The fibula itself can simply be smaller in size but in the most severe cases it may be completely absent (Table 13.14.2).

Treatment guidelines were highlighted by Birch et al. (1998) in their ‘Functional classification of fibular deficiency’ (Table 13.14.3). Patients are divided by possessing a functional foot or a non-functional foot, and further divided by leg length discrepancy: minor discrepancies may be considered for equalization but a discrepancy of 30% or more would require multiple lengthenings and could be considered for amputation (Box 13.14.3).

Our preferred amputation for a severe Type I is the modified Syme’s disarticulation (Figure 13.14.8). The remaining stump acts as a below-knee level amputation at skeletal maturity and is fitted with the corresponding type of prosthesis. The Boyd type amputation may be considered but difficulties in placing the calcaneum below the tibia can be encountered as the calcaneum is often in significant equinus and adherent to the posterior cortex of the tibial shaft.

Type II cases with a non-functional foot are further subdivided into IIA with a functional proximal component of the limb, treated with amputation as described earlier and IIB with a non-functional proximal part. In these cases salvage procedures are considered as the foot may become important for function.

Other surgical interventions may be necessary for associated femoral deformity such as the genu valgum secondary to lateral femoral hypoplasia (Figure 13.14.8B).

This uncommon condition is characterized by complete or partial loss of the tibia but usually with the presence of a normal fibula. Clinically, there is anterolateral bowing of the lower leg with equinovarus position of the foot. There may be duplication of the toes and associated hand anomalies. Jones classified tibial deficiency into four types (Table 13.14.4 and Figure 13.14.9).

Classic recommendations dictate knee disarticulation for types 1a and 3, and below-knee amputation for types 1b and 2. Reconstruction may be considered in types 1b, 2, and 4 either by limb lengthening or consideration of ipsilateral fibula transfer using Brown’s procedure.

Femoral deficiency may present with subtotal absence of the femur, true PFFD (see Figure 13.14.2), or simple femoral hypoplasia, with a femur that is normal anatomically but simply smaller than the contralateral bone. There are several classifications in the literature describing the spectrum of radiological appearances that can be seen.

Radiographs alone may, however, be misleading of the actual femoral length, especially if the film is taken with the limb in its characteristic resting posture of hip flexion, abduction, and external rotation. Although radiographs obviously aid in management decisions, they should be used in conjunction with a full clinical assessment of the limb. The function and possible fixed contractures of the hip and knee joints will impact on surgical intervention (see Figure 13.14.2B).

Gillespie and Torode initially recognized two broad groups—true PFFD and congenital short femur. Later a change was proposed that would take into account the clinical features. Group A consist of congenital short femur with no hip instability and minimal fixed flexion of hip and knee. By extending the limb the foot lies opposite the mid part of the contralateral tibia or lower. The shortening will be 20% or less. Group B are an exaggeration of group A, the thigh is short and bulbous with the hip in flexion, abduction and external rotation. There is a sense of proximal instability with ‘pistoning’ of the proximal femur. When the limb is pulled down into extension the foot lies at the level of the opposite knee or shorter, the knee fixed flexion persists. Group C represents those patients with a subtotal loss of the femur. There is marked proximal instability with a similar clinical appearance to group B.

In group B the proximal femur tends to flex anteriorly during weight bearing. This makes prosthetic fitting difficult: treatment options include performing an arthrodesis of the knee in combination with an ankle disarticulation. This produces a single lever arm with the aim of leaving the end of the limb slightly proximal to the opposite knee and allowing an above knee prosthesis to be fitted.

In group C patients, due to the femur being so much shorter, anterior displacement of the thigh segment does not occur and therefore knee fusion may not be required as an ischial bearing prosthesis can be fitted more easily.

An alternative procedure is the van Nes rotationplasty, described in 1950. The aim with this procedure is to fuse the knee as above whilst rotating the foot 180 degrees to leave the ankle lying at the level of the opposite knee. The gastrocnemius and soleus muscles then act as ‘knee’ extensors and a below-knee type prosthesis may be fitted. We have no experience of this technique. A comparison between the two procedures emphasized the need for individual treatment plans. With a good hip and adequate ankle function then the rotationplasty allows more ‘normal’ function as judged clinically, but there can be a psychological price to pay due to the abnormal cosmetic appearance.

Recently, authors have emphasized again the importance of knee mobility and knee deficiency in patient management and some feel that knee function is of greater importance than hip stability (Table 13.14.5).

The strategy of Paley’s treatment algorithm is for reconstruction from proximal to distal thus ultimately reconstructing a functional limb of equal length. He does accept that amputation may be the preferred option in type 3 cases.

Finally, the Steel femoropelvic fusion is a procedure that may be considered in those severe cases of significant diaphyseal femoral loss (Gillespie Group C, Paley Type 3). The femur is fused to the pelvis in a flexed position to allow the knee to act as the ‘hip’. A good result allows the patient to function as an above-knee amputee.

Prosthetic replacement forms an important and integral part of the management of PFFD. Because of the inevitable limb shortening on the affected side, the aim of treatment is to equalize limb length for effective gait. This can be achieved by simple devices like heel or shoe raises if the shortening is minimal. If the shortening is significant and greater than that which can be managed reasonably with a shoe raise, an ‘extension prostheses’ is used. This is essentially a prostheses accommodated distally to the end of the short limb, effectively ‘extending’ it to the ground level and attached proximally to the short limb by enclosing it in the prosthetic socket. The design and construction varies, dependant on the deformity including shape and size of the residual limb and joint function and understandably they are not particularly aesthetic (Figure 13.14.10). Sometimes, surgical intervention may be advisable, to improve function and appearance by facilitating use of standard below or above-knee prostheses. Thus, a Syme’s disarticulation in a child with fibular hemimelia or PFFD with a stable hip joint may allow use of a cosmetically more acceptable, standard transtibial or transfemoral prosthesis (Figure 13.14.11).

All categories of patients with femoral shortening should initially be treated with extension prostheses to allow them to stand up when they are ready to do so, generally around the ages of 12–18 months. In patients with a severe form of PFFD with no true hip joint and the knee virtually at the hip level and with associated fixed contracture, the prostheses needs to be ischial tuberosity bearing. Rarely, they may need to enclose the whole pelvis. If the foot is a significant cosmetic problem, a Syme’s disarticulation should be recommended. With an intermediate degree of PFFD and minor loss of hip extension, an arthrodeses of the knee joint and Syme’s amputation may allow the use of standard transfemoral prostheses if the resultant stump length is approximately equal to the contralateral femur. In practice, this is most effective and appropriate in those patients who have associated distal limb deficiencies in the fibula and foot.

The principles for prosthetic prescription for distal deficiencies are similar. An extension prosthesis is provided for limb shortening, if it is too great to be overcome conveniently with an orthosis or shoe raise. However, the extension prostheses may not need to extend proximal to the knee joint. If a Syme’s disarticulation has been performed, a standard transtibial prosthesis will be appropriate, and cosmetically preferred. Good function is achieved. If a knee disarticulation has been performed, a standard prosthesis for the appropriate level is prescribed. It should be noted that a transfemoral prosthesis is often appropriate for a knee disarticulation because of the associated minor femoral shortening and knee clearance available.

Prosthetic management for longitudinal lower limb deficiencies is challenging. Each case has to be assessed on individual circumstances and management planned jointly with the surgical and medical rehabilitation teams.

Discussion of this topic is outside the remit of this chapter but many of the principles that govern management of the congenital limb deficiency are applied to patients with acquired limb deficiency: in both groups, consideration must always be given to possible problems with the opposite lower limb (Figure 13.14.12).