Introduction
Arthrogryposis, also known as arthrogryposis multiplex congenita (AMC) is a rare diagnosis that applies to all children with congenital joint contractures affecting more than one limb. Multiple conditions fall within the AMC umbrella, including progressive neuromuscular disorders such as spinal muscular atrophy, idiopathic disorders such as amyoplasia, and inheritable nonprogressive disorders such as Beal’s syndrome and other distal arthrogryposes (DAs). All told, there are over 300 myriad disorders that fit under the AMC umbrella. Having a single chapter on “Arthrogryposis” is akin to having a single chapter on “Fractures.” Each of the 300+ variations have their own personality, prognosis, and management. This chapter will therefore focus on the most common types, and could not possibly cover all phenotypes or genotypes.
Amyoplasia is the single most common type, accounting for around 30% of cases. Presentation can range from bilateral mild joint stiffness to complete skeletal muscle aplasia and gastroschisis requiring permanent ventilatory support and tube feeds. Most children, however, are born within a narrow range of the typical phenotype, with the shoulders adducted and internally rotated, elbows extended, forearms in neutral, wrists in flexion, and fingers in flexion with the thumbs in the palm ( Fig. 10.1A ). Because the posture of the arm is nearly identical to the “waiter’s tip” ( Fig. 10.1B ), amyoplasia isolated to the upper extremities is most commonly misdiagnosed as a bilateral brachial plexus birth injury (BPBI), or Erb’s palsy. Clinically, the two diagnoses can be differentiated by the restriction of passive motion in amyoplasia. Children with a BPBI should have full passive motion up to 2 months of age, when shoulder internal rotation and elbow flexion contractures begin to develop. Lower limb involvement is also common in amyoplasia with club feet present in most cases. Another distinct common feature of amyoplasia is a stork-bite hemangioma around the bridge of the nose and/or the occiput ( Fig. 10.2 ), which is thought to be associated with maternal estrogen levels. The etiology of amyoplasia remains unknown, but there is speculation of primary muscular versus anterior horn cell aplasia or apoptosis. Theories of extrinsic causes for amyoplasia such as oligohydramnios and bicornuate uterus are falling out of favor. A genetic cause or predisposition has yet to be found. We have never seen both of a set of identical twins affected with amyoplasia, suggesting that genetics is unlikely to play a role.
Different from amyoplasia, the DAs ( Fig. 10.3 ), of which there are now over 10 types ( Table 10.1 ), do have a predominantly autosomal dominant genetic etiology. Presentation is again quite variable, with some forms of Escobar syndrome resulting in fetal demise and other types such as Sheldon-Hall typically having excellent upper limb function and a normal lifespan.
| Distal Arthrogryposis Types | Other Name(s) | Label | Characteristic Findings |
|---|---|---|---|
| Distal arthrogryposis type 1 | Common or typical | DA1 | Camptodactyly, clasped thumb, clubfoot |
| Distal arthrogryposis type 2A | Freeman–Sheldon syndrome | DA2A | Whistling face, camptodactyly, clasped thumb, clubfoot, scoliosis |
| Distal arthrogryposis type 2B | Sheldon-Hall syndrome | DA2B | Prominent nasolabial folds, downslanting palpebral fissures, small mouth, camptodactyly, clasped thumb, clubfoot |
| Distal arthrogryposis type 3 | Gordon syndrome | DA3 | Short stature, cleft palate |
| Distal arthrogryposis type 4 | Scoliosis | DA4 | Scoliosis, camptodactyly |
| Distal arthrogryposis type 5 | Ophthalmoplegia, ptosis | DA5 | Ptosis, strabismus, restrictive lung disease |
| Distal arthrogryposis type 6 | Sensorineural hearing loss | DA6 | Hearing loss, camptodactyly |
| Distal arthrogryposis type 7 | Trismus-pseudocamptodactyly | DA7 | Trismus, pseudocamptodactyly, short stature |
| Distal arthrogryposis type 8 | Autosomal dominant multiple pterygium syndrome, Escobar | DA8 | Multiple pterigia, camptodactyly, scoliosis, ptosis, downslanting palpebral fissures |
| Distal arthrogryposis type 9 | Beals syndrome (congenital contractural arachnodactyly) | DA9 | Camptodactly, arachnodactyly, kinked upper earlobe, tall stature |
| Distal arthrogryposis type 10 | Congenital plantar contractures | DA10 | Plantar contractures |
Regardless of etiology, the role of the therapist in caring for these patients is threefold: (1) assessing the child’s function and functional goals, (2) assisting with surgical planning, and (3) providing pre- and postoperative therapy. The treatment goals are to maximize joint motion, compensatory strategies, and overall independence.
Classification
There are three basic subtypes to AMC: (1) amyoplasia, (2) distal arthrogryposes, and (3) congenital neuromuscular conditions. Within these subtypes, amyoplasia encompasses a wide range of presentations but these variations are believed to be due to severity of involvement rather than to a different etiology or subdiagnosis. The DAs are distinct inheritable disorders that may have variable phenotypes within each genotype, but are overall consistent with their patterns of involvement. Beal’s syndrome, for example, presents with characteristic camptodactyly and arachnodactyly (contractural arachnodactyly) in nearly all patients, but the degree of contracture varies widely from patient to patient. The third and least common category includes the most distinct disorders, with well over 300 central nervous system and neuromuscular disorders ( Table 10.2 ).
| Central Nervous System | Neuromuscular |
|---|---|
| Moebius syndrome | Maternal myasthenia gravis |
| X-linked spinal muscular atrophy | Maternal Botox administration |
| Infantile spinal muscular atrophy (Werdnig–Hoffmann disease) | Congenital muscular dystrophy |
| Emery–Dreifuss muscular dystrophy |
There is currently no schema by which to classify the severity of involvement, and despite what some have suggested, we have found no identifiable pattern of involvement. Some children have normal lower extremities and very limited upper limb function. Others have the exact opposite. Side-to-side differences are less dramatic. If a patient has asymmetric involvement, some have suggested a central neurologic insult and have recommended imaging of the brain and cervical spine. Despite a classic presentation as described earlier, exceptions are the rule and each child has to be assessed individually.
Initial Visit Assessment and Early Management
We recommend an initial visit to a therapist or surgeon within the first 2 months of life. Because of the rarity of the diagnosis, families are often misinformed or unaware of the diagnosis and are often hurting emotionally. The primary goal of the initial visit is to explain and/or confirm the diagnosis and answer all the questions asked by the family. It is important for families to understand that most conditions with congenital contractures improve over time, that there is hope that their child will be able to be independent, and that they are a critical part of the care team. For the family, this initial interaction with the medical team, who will usher them through their grieving period and into a place where the family can become meaningful participants in their child’s care, is critical for building a long-term relationship that best serves the patient.
In neonates, the examination is mostly observational: watch for spontaneous active motion of the limbs as the child lies on an examination table or in their caretaker’s arms. Each upper extremity joint complex is assessed for active and passive range of motion. Look for shoulder position and motion, particularly rotation. Determine passive and active elbow, forearm, wrist, and hand motion. In the older child, test grasping ability, writing method, and strength throughout the limb(s). When a child is of age to engage in perineal care, determine if this is best done around the back, or through the legs. Resist the temptation to intervene early with functional aids or functional tricks; allow the child to develop their own compensatory movement patterns. Counsel the family to provide as minimal assistance to the child as possible. Let the child figure things out for themselves whenever possible. Once the child asks for support, provide tips and tricks first, and specialized equipment later.
Most children with amyoplasia will have shoulder internal rotation contractures with a deficit of passive and active external rotation. This will result in a crossover grasp pattern ( Fig. 10.4 ). Elbow extension contractures are more common ( Fig. 10.1 ), but flexion contractures can also occur. Generally, children with both active elbow flexion and extension will have minimal contractures. Children with elbow flexion contractures typically have weak or absent triceps function. Conversely, extension contractures are most often the result of weak or absent elbow flexors. It is rare, but not unheard of, for a child to have no active elbow flexion and retain passive motion. Children with DAs most commonly have a functional active elbow arc of motion in both flexion and extension. The exception is Escobar syndrome, which presents with elbow flexion contractures and pterygia ( Fig. 10.3 ).
Much has been written about the forearm protonation contractures of children with AMC, despite protonation contractures being just as common as supination contractures, and both being relatively uncommon. Most children have a limited arc of forearm motion, both passive and active, that is centered around neutral. Analogous to elbow contractures, forearm contractures follow the principle that the joint will contract in the position of action of the active muscles. Children with AMC typically have no biceps, no supinator, no pronator teres, and no pronator quadratus, so their forearms remain in a neutral position.
The wrist in amyoplasia is most often in flexion and ulnar deviation ( Fig. 10.1 ), but can also be in extension and/or ulnar deviation. By contrast, wrist extension is the norm, but not the rule in DAs ( Fig. 10.5A ). Nearly all children will have limited passive and active motion regardless of diagnosis or wrist position. Wrist extension contractures in DAs are often accompanied by ulnar deviation of the finger metacarpophalangeal (MP) joints, particularly when the wrist is in radial deviation. In amyoplasia, if the wrist is in flexion and the patient retains active extrinsic finger extension (extensor indicis proprius, extensor digitorum communis, extensor digiti minimi), the MP joints will posture in extension. Some children will be born with or quickly develop MP joint hyperextension contractures.
The interphalangeal finger joints will typically be stiff or even ankylosed, with absent or diminished flexion creases. The lack of fingers creases is the telltale sign of a stiff or ankylosed joint. Camptodactyly, a flexion contracture of the proximal interphalangeal (PIP) joint, is common, particularly in the central two fingers ( Fig. 10.6 ). The thumb can present with isolated MP or carpometacarpal (CMC) joint flexion contractures, or a combination of both ( Fig. 10.7 ). Clasp thumb, extension of the CMC and flexion of the MP joints ( Fig. 10.5 ), though considered to be common in AMC, is predominantly seen in DAs and rare in amyoplasia. Most patients with amyoplasia will have flexion at both thumb MP and CMC joints to some degree, but the CMC flexion contracture will be the primary deformity ( Fig. 10.8 ).
Initial treatment is always passive range of motion exercises with an emphasis on a home stretching program. It is not possible to rely solely on the therapy provided by a professional once to a few times a weeks. As we tell our patients, passive stretching is like eating: it is good to be fed a few times a week, but better to feed yourself three times a day. Some of the best results I have seen are from caretakers who had the time and discipline to range the child every hour on the hour while awake. Although this intense a therapy regimen is unattainable for most, it does demonstrate that, at least in some cases, more therapy is better. As a guideline, we tell our deputized therapists to move every joint that does not move by itself.
Neonates are often too small and some too contracted to be fitted with splints. Even when splints become technically possible, somewhere between 3 and 6 months, we prefer to splint only at night and naptimes to allow unencumbered motion during the day for cognitive and muscle mass development. Common splints include wrist and finger extension, thumb spica wrist extension, and elbow flexion hourglass splints ( Fig. 10.9 ). Dynamic splints are poorly tolerated and have questionable value when considering the cost.
