13.9 Arthrogryposis

Arthrogryposis, or arthrogryposis multiplex congenital (AMC), is purely a descriptive term: it means ‘hooked or curved joints present at birth’. If a child has joint contractures present in two or more different body areas associated with muscle wasting, then the child can be said to have arthrogryposis but there are over 300 different, specific conditions that present in such a way. The clinical features, inheritance patterns, and prognoses of these conditions vary considerably, so an accurate diagnosis is imperative. Three broad groups have been identified which occur with approximately equal incidence (Box 13.9.1). Firstly, there are those with primarily joint involvement. Secondly, there is a group that includes children with involvement of another body system as well as their limbs. The third group includes those with limb and central nervous system involvement in which there is a high mortality in early life.

This discussion relates principally to children with amyoplasia and distal arthrogryposis but the principles are common to all those with multiple congenital contractures.

The joint contractures are caused by limb deformation in utero. The deformities are not a result of primary limb malformations. A lack of fetal movement, or fetal akinesia, is thought to be the final common pathway in the development of the clinical picture but many other factors may play a role and both myopathic and neuropathic aetiologies have been implicated. The lack of joint movement leads to extra connective tissue around the joint, shortened tendons, and modelling of joint surfaces. Although the contractures are not progressive they have a tendency to recur rapidly after correction. Correction can be difficult because the tissue planes encountered during surgery are significantly less well defined than normal as are the individual muscles. Muscles are generally weak, sometimes profoundly so, but the pattern and extent of muscle weakness is very variable. Preservation of muscle strength is an important principle of treatment.

Multiple congenital contractures occur in 1 in 3000–5000 live births but true amyoplasia is less frequent (1 in 10 000). Most case series in the literature report on less than 20 patients. Amyoplasia is a sporadic condition whilst at least one form of distal arthrogryposis is inherited in an autosomal dominant fashion with the defect mapped to the short arm of chromosome 9.

A child with amyoplasia will usually have symmetrical limb deformities and the majority have all four limbs affected (Figure 13.9.1). Birth fractures may be identified in one in five children. The skin is shiny and joint creases are reduced or absent in affected limbs. The deformities are symmetrical with severe equinovarus (CTEV) deformities of the feet and extended elbows; 10% have abdominal wall defects. The limb deformities are most severe at birth and often quite alarming. However, some of the deformities are positional and will respond to treatment in the neonatal period. Resistant deformities will require more intensive therapy or surgery.

Distal arthrogryposis is characterized by medial deviation of the digits, camptodactyly, clenched fists, and foot contractures. Mild proximal joint involvement can occur. Problems related to each joint or region will be discussed in the following sections.

Most families will not have heard of arthrogryposis but most adapt well to the diagnosis. Organizations such as The Arthrogryposis Group (TAG) in the United Kingdom can provide invaluable support for families of affected children. Childhood can be challenging because of the intensive treatment required in the early years of life and the considerable effort required to ensure that the child functions safely in his/her environment. Although they may be affected profoundly by multiple joint contractures, they do not have the same communication problems, sensory abnormalities, perceptual, and balance problems that affect children with cerebral palsy and spina bifida. The prognosis for walking, without treatment, is poor particularly in the amyoplasia group. With treatment, the majority of children with amyoplasia should be able to walk in childhood but they may lose this ability as they pass through adolescence into adult life. The children have near-normal or normal levels of intelligence and tend to be very determined: described by their mothers as ‘kind, social, attractive but more persistent or even stubborn than their siblings’. The life expectancy for those with distal arthrogryposis is thought to be normal and for those with amyoplasia a survival rate of 94% at 20 years has been reported.

As far as personal and social development are concerned, one demographic study reported that 64% of older children in one series were in an educational setting appropriate for their age with 75% independent for feeding, 20% for grooming, 10% for dressing, 35% for toileting, and 25% for bathing. Another study found that half of their adult patients were employed, a third were married, half were independently mobile (with wheelchairs as necessary), and 70% had no limitations in activities of daily living. Their conclusion was that their dependence upon others ‘was not related to physical deformity but to their personality, their education and to their coping skills’. Clearly orthopaedic surgery is only one aspect of the care needed by these children and their families.

Coordination between health professionals is essential in managing these children and a multidisciplinary team (MDT) approach is recommended. Treatment must be directed at enhancing function and independence throughout their lifetime. It is therefore important that treatment interferes as little as possible with the child’s normal development, education, and family life. Treatment should begin as soon after birth as possible. Serial casting and orthoses are used to correct the positional deformities of the limbs, reassuring the parents that the deformities are always the most severe at birth. Most authors recommend correcting fixed deformities in infancy with ‘fine tuning’ procedures later in life and the Seattle group have recommended the following approach to treatment:

Children with arthrogryposis can present significant problems for the anaesthetists. It may be extremely difficult to secure venous access and mouth opening may be restricted, making tracheal intubation difficult. An increased risk of malignant hyperpyrexia and aspiration has been reported.

Orthoses are an essential part of the management of arthrogryposis. They are used to maintain correction of deformities and to facilitate standing in cases of muscle weakness and joint contracture. They must fit well and make a significant difference to function otherwise the child is likely to reject the splints. A great deal of parents’ energy can be used trying to get their child to wear splints: these children can be very strong willed! The team must be prepared to offer the families as much support as they need (Figure 13.9.2).

Upper limb involvement is common in amyoplasia. The classic posture is of internal rotation of the shoulders, extension of the elbows, and flexion and ulnar deviation of the wrists and fingers (Figure 13.9.3). The degree of muscle weakness in the upper limbs is variable but may be profound. Generally, the elbow extensors are stronger than the flexors and the wrist flexors are stronger than the extensors. Some children have very little movement in the hands. The management of these deformities should be directed towards independence in adult life. The MDT must promote the skills necessary not only for activities of daily living, such as eating, dressing, and toileting, but also for vocational skills such as the use of a computer keyboard. The child may also need to use crutches for walking, or to use their upper limbs for operating a wheelchair. The aims are to help the child to hold objects with as functional a hand as possible, and also to be able to position that hand in space appropriately. One simple philosophy is that the child should have one hand available for hand-to-mouth activities, such as eating and drinking, and the other able to help with perineal hygiene or with pushing themselves up out of a chair. Others prefer a more individualized treatment programme based on the child’s needs and abilities. There is no doubt that stretching, casting, and the use of orthotics are very effective for upper limb deformities. However, for them to be most effective, they must be started as soon after birth as practically possible, and the involvement of a hand therapist is recommended. Most authors recommend that surgical treatment for upper limb problems should be performed either in infancy or early childhood with later secondary procedures if required.

The shoulders are internally rotated and the profile of the shoulder is down-sloping. It is rare for the fixed internal rotation contracture to cause a functional problem but occasional derotation osteotomies of the humerus have been performed.

The elbows may be fixed in flexion or extension but extension is more common. A fixed elbow contracture is the deformity likely to produce most disability. The range of motion is variable and usually the triceps is much stronger than the biceps. It is important to achieve as much passive movement as possible to enable the hand to reach the face, but ideally this should not be at the expense of losing strong elbow extension which is necessary for getting out of a chair or for using crutches. There needs to be a compromise. Stretching and splinting can increase the range of movement in infants. If there is less than 90 degrees of elbow flexion then a posterior release and triceps lengthening will increase the passive range of movement. There is more controversy about the role of muscle transfers to restore active elbow flexion. The pattern of muscle involvement is variable. Triceps transfer is the most widely used but pectoralis major, latissimus dorsi, and proximal transfer of the common flexor origin have also been described. The risk with these procedures is that a fixed flexion contracture may develop and all muscle transfers will result in decreased function elsewhere.

In both amyoplasia and distal arthrogryposis, the classic deformities of the hand and wrist are flexion and ulnar deviation of the wrists and curved flexed fingers (Figures 13.9.3 and 13.9.4). The thumb is often tucked in the palm. This posture makes prehension and grip difficult and the problems are compounded by forearm and intrinsic muscle weakness. The use of neonatal serial casting is extremely effective in improving wrist position, particularly in distal arthrogryposis. Casting should be followed by the use of lightweight custom-made orthoses, worn principally at night, to enable the child to use the hand during the day. This splinting regimen is supplemented with a regular stretching programme. The orthoses need to be replaced regularly as the child grows. There does not appear to be a consensus on the indications and timing for wrist surgery but, on average, only one-third of those with upper limb involvement undergo surgical treatment. Surgery can either be performed within the first year of life or at a later age. Those who advocate early surgery do so because they claim that surgery is more difficult after the first year of life: the contractures are more severe in the older child, the joint surfaces will have remodelled with intra-articular adhesions, and the skin has become less elastic. They claim that there is a more rapid recovery with less scarring and a greater remodelling potential when surgery is performed in infancy. Others suggest that surgery should not be undertaken early but only after the wrist position that will give best function has been identified. This needs to take into account finger flexor power, extension power, and the child’s specific functional requirements (Box 13.9.4). Each child develops their own coping strategies for dealing with the activities of daily living: surgical intervention must be sure to improve the situation rather than simply altering it (Figure 13.9.5). Surgery may involve a volar capsular release, a trapezoidal dorsally-based wedge carpectomy, and tendon transfers to act as check reins.

There can be a significant improvement in finger position and function after the correction of wrist deformities, as the resection of a trapezoidal wedge reduces tension in the contracted finger flexors. Surgical correction of finger deformities is rarely required. When they are refractory to splinting, thumb contractures may be treated by adductor release or, in older children, by metacarpophalangeal fusion and brachioradialis transfer. Web-deepening procedures may also be necessary to improve grasp particularly for the first web space.

Almost 90% of children with amyoplasia will have lower limb deformities. Rigid equinovarus deformities and flexed knees are the commonest pattern accompanied by flexed and abducted hips (see Figure 13.9.1). Sometimes the lower limb deformities at birth can be quite bizarre but these tend to be postural deformities that respond well to careful stretching and splinting. The goals of lower limb management are to provide stability and symmetry to maximize the potential for walking. Surgery for lower limb deformities should be deferred until it is clear whether the child is likely to walk, which can be exceedingly difficult to judge. Preoperative assessment must take into account not only the degree of joint deformity and muscle strength, particularly of the hip extensors and quadriceps, but also the extent of upper limb involvement. A child who is likely to spend most of their time sitting needs symmetrical lower limbs with plantigrade feet. When surgery is required it is better to do simultaneous procedures on different joints, in order to reduce the immobilization time and the time spent in hospital during childhood.

Soft tissue contractures around the hip are common. Most positional deformities respond to careful stretching and splinting. Flexion contractures in excess of 30 degrees are likely to impair walking and those over 45 degrees are likely to require surgical release.

Hip dislocation occurs in almost a half of all children with amyoplasia and is usually bilateral A unilateral dislocation will affect standing, gait, and sitting balance and should be reduced (Figure 13.9.6). Closed reduction is usually unsuccessful in arthrogryposis. There is still debate about what should be done with bilateral hip dislocations—some believe they should be left untreated, particularly if stiff, but the balance of opinion is tending to swing towards reduction in those who are likely to walk. Reduction of bilateral dislocated hips is said to provide a better-looking and more efficient gait. Some recommend the medial approach for hip reduction because the soft tissue dissection is minimal and there is little blood loss. This is important if the feet and knees are being treated in the same operating session. It is also claimed that there is less stiffness following reduction through a medial approach than after an anterolateral approach but success has been reported with both techniques. In older children concomitant pelvic surgery or femoral shortening may be required. The threshold for treating residual acetabular dysplasia is higher in children with arthrogryposis than without.

Knee involvement is present in 70% children with amyoplasia. The common patterns are fixed flexion, fixed extension, or, less frequently, hyperextension. Fixed flexion of greater than 20 degrees makes standing difficult whilst conversely sitting is difficult with fixed extension (Figure 13.9.6). Patients with extended knees are more likely to be community walkers in the long term but may be at a higher risk of degenerative joint disease. An arc of movement between 15–60 degrees is the ideal. Flexion can be gained with a quadricepsplasty but, in the child with significant quadriceps weakness, this may make it less likely that they will be able to stand. Extension can be achieved by a soft tissue release (with femoral shortening in severe cases), a supracondylar femoral osteotomy, or through the use of a ring fixator. Recurrent deformities are common and splintage is essential after surgery to reduce this risk (Figure 13.9.2). Straightening out flexed knees is the only procedure in paediatric orthopaedics that makes a child walk (Staheli 1993).

The vast majority of children with arthrogryposis have foot deformities, most commonly a rigid equinovarus (Figure 13.9.6). Occasionally they may have congenital vertical talus (Figure 13.9.7). Recurrence is the main problem following surgery and many children will require second procedures despite long-term postoperative splinting. The aim of surgery is to produce a rigid plantigrade platform which can be accommodated in normal shoes. Ponseti-style serial casting has been tried and although early reports are favourable, to date, there are no published series available with satisfactory follow-up. More casts are required for correction compared to the idiopathic foot deformity (see Chapter 13.21) and recurrence is common. The options for surgical treatment of the equinovarus foot are either a radical soft tissue release or primary talectomy (see Figure 13.9.6). Most authors recommend a radical soft tissue release as the primary procedure but the recurrence rate may be up to 73%. Recurrences can respond to serial casting or secondary soft tissue surgery and satisfactory results can be achieved in over 90%. There is no doubt that talectomy is a valuable salvage procedure, provided the bone is completely excised and the foot is placed in the correct position after surgery. The Ilizarov method has been used to treat recurrences with good results reported from some specialist centres.

Approximately 20–30% of children with amyoplasia will develop scoliosis. This may affect sitting balance and interfere with upper limb function. The most common curve pattern is thoracolumbar. Curves that develop in early childhood tend to become the most severe. Some, but not all, curves progress relentlessly even after skeletal maturity. Bracing should be used to contain progression and to treat curves less than 30 degrees. Children with curves greater than 50 degrees should be considered for surgery, with a combined anterior and posterior instrumented correction appearing to produce the most reliable results.

Arthrogryposis is uncommon, but needs to be recognized early in life so that treatment can be started, and positional deformities corrected. In the next 5–10 years, there are likely to be great advances in the understanding of the conditions of which multiple congenital contractures are a feature. There are many controversies regarding the timing and nature of surgical treatment and very little evidence upon which to base management. More children are being managed in specialist centres by MDTs and it is to be hoped that collaborative research will lead to better outcomes for these children in the future.