- Arthrogryposis refers to a variety of conditions characterized by joint contractures related to fetal akinesia.
- Most cases are idiopathic. Distal arthrogryposis is linked to autosomal dominant transmission.
- Hip dislocations are teratologic and do not respond well to Pavlik harness or closed reduction
Description:The term refers to a variety of conditions with the common pathology of decreased fetal movements, congenital joint stiffness and varying degrees of muscle weakness. Amyoplasia refers to the most common type of arthrogryposis (Hall, 1997).
Etiology and EpidemiologyThe clinical findings of arthrogryposis are due to fetal akinesia. There are multiple proposed mechanisms that result in a lack of fetal motion: failure of skeletal muscle development, anterior horn cell abnormalities, vascular interruption, defective myogenic regulatory genes resulting in defective somites, maternal antibodies to fetal acetycholine receptor (as in maternal myasthenia gravis) and possible infectious viral causes (Hall, 1997; Swinyard, 1985). About 93% of cases are thought to be neuropathic (abnormal anterior horn cells) and 7% myopathic.
Distal arthrogryposis has been linked to autosomal dominant transmission. Most forms of amyoplasia are idiopathic, and there is no known genetic cause. The incidence of arthrogryposis is 1 in 3000 births. The incidence of true amyoplasia is 1 in 10,000 births (Hall, 1997).
Clinical Findings:The diagnosis can be identified in utero as early as 19 weeks gestational age due to lack of fetal movement. Breech position is common because of the inability of the fetus to kick strongly enough to turn vertex. Many of these patients are delivered via caesarean section. If not diagnosed in utero, most cases are recognized at birth.
Patients with classic arthrogryposis, or amyoplasia congenita, present with normal intelligence and multiple contractures of all of the extremities. They may also have a midline cutaneous hemangioma (nevus flammeus) on the forehead. The limbs appear thin, atrophic and are without normal flexion creases. Joint motion is markedly decreased in affected joints. Active function is limited in affected limbs. The characteristic joint contractures in amyoplasia include the upper extremity “waiter’s tip” position: shoulders adducted and internally rotated, elbows extended, forearms pronated, wrist flexed and ulnarly deviated, thumb opposed. In the lower extremity hip motion is usually preserved, the knee is either extended or flexed, and foot is typically in equinovarus. Some children develop scoliosis that is usually a large, sweeping c-shaped neuropathic curve with marked pelvic obliquity. The contractures and weakness are not progressive (Bernstein, 2002).
Treatment:Long-term outcomes in these patients have been attributed more to family support, patient personality, education and early attempts to foster independence rather than overall physical involvement and limitations (Carlson, 1985). Treatment should be focused on improving the child’s overall function and independence. Initial treatment should start at birth and involves gentle stretching, range of motion and taping of any contractures. Once the position of a joint is acceptable, lightweight splinting may slow recurrence of contractures. If the joints cannot be placed into an acceptable position, serial casting or soft tissue releases followed by casting may be undertaken.
HipIn general, supple dislocated hips are preferred to stiff, located hips. If the patient has markedly limited range of motion or does not have ambulatory potential, then the hips are not reduced. These are teratologic hip dislocations and closed reductions have poor results. Pavlik harness treatment should not be undertaken. The treatment of bilateral dislocations is controversial. In general, unilateral dislocations are best treated early around age 6 to 12 months with open reduction via an anterior or medial approach and then casted for 6 weeks. Favorable results have been reported using the medial approach (Staheli, 1987; Szoke, 1996). Hip abduction and adduction contractures may contribute to pelvic obliquity and scoliosis. These are treated with stretching and soft tissue releases for mild contractures (Bernstein, 2002). Severe contractures may necessitate osteotomy.
KneeFlexion contractures are more common than extension contractures and limit ambulatory potential to a greater degree. The first line of treatment of flexion and extension contractures is stretching, splinting, bracing and casting. For flexion contractures, soft tissue releases of the hamstrings, posterior capsule and posterior cruciate ligament are technically demanding due to the abnormal appearances of the tissues planes and difficulty identifying neurovascular structures. Adhesions beneath the patella must also be released via a separate incision. If soft tissue release fails, a distal femoral extension and shortening osteotomy can be done (Delbello, 1996). In extension contractures and dislocations that do not respond to conservative measures, a formal quadricepsplasty or open reduction of the knee is usually necessary. Overzealous quadricepsplasty can lead to iatrogenic flexion contractures.
FeetThe most frequent foot deformity is a rigid equinovarus foot and ankle, and the discussion here will focus on treating equinovarus deformity. However, almost any other foot deformity is possible. The goal of treatment is to create a plantigrade foot that is braceable for weight bearing. These feet are usually stiff after treatment. Initial Ponseti casting is undertaken and can be effective (Boehm, 2008; Morcuende, 2008). A modified Ponseti approach where the percutaneous heel cord tenotomy is done prior to casting can also be successful in decreasing the need for extensive soft tissue releases (van Bosse, 2009). Post-casting immobilization is especially important in this population. For rigid recurrences, incomplete corrections or late presenting patients, operative intervention with formal posteromedial release is undertaken. The medial tendons are typically sectioned without repair. The Achilles is formally lengthened. A lateral column shortening osteotomy may be done for residual adductus. Repeat correction for arthrogrypotic clubfoot involves neurovascular risk exceeding that associated with idiopathic deformities (Bernstein, 2002).
Upper ExtremitiesMuch of the treatment of the upper extremity deformities involves the child, family and occupational therapist in creating adaptive solutions for activities of daily living. Surgery is used to maximize the patient’s functional potential. The first goal is to achieve passive elbow flexion. Often patients are born with extension contractures of the elbow. If passive elbow flexion is less than 90 degrees after trials of stretching, splinting and taping, then surgical intervention is recommended. Favorable results have been reported with a triceps lengthening and posterior capsular release (Axt, 1997). The second priority is to correct the humeral rotation and then reposition the wrist and correct thumb-in-palm deformity. In classic amyoplasia, the shoulder is usually contracted in internal rotation. To position the upper extremity in a more favorable position, an external rotation osteotomy of the midshaft or supracondylar region of the humerus may be done. Wrist flexion contractures may be treated with early release and casting. In many cases there are no functioning extensors and the flexor carpi ulnaris (FCU) may be the only well-functioning flexor driving the wrist into flexion and ulnar deviation. FCU transfer to the dorsum of the hand can be considered in these patients as long as they have baseline passive extension of the wrist past neutral. A carpal wedge osteotomy to bring the wrist out of flexion to help with function and hygiene may be considered in more rigid contractures (Ezaki, 2004) This may be more favorable than the older technique of proximal row carpectomy. In general, hand contractures are difficult to stretch and not much function is gained via surgical intervention. Releases should be considered for severe thumb-in-palm deformities.
ScoliosisThe predominant curve is a single thoracolumbar curve often associated with pelvic obliquity in the non-ambulatory patient (Daher, 1985). Bracing is typically ineffective. Young age of onset, difficult surgical exposure, large curve magnitude and poor soft tissue coverage make scoliosis management in this population difficult.
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