Congenital pseudarthrosis


Congenital pseudarthrosis

Description, Causes and Risk Factors:

Congenital pseudarthrosis is a rare pediatric orthopaedic condition with its incidence being less than 1/10 that of DDH (developmental dysplasia of the hip). Congenital pseudarthrosis is characterized by anterolateral bowing of the tibia, with tapering of the tibia at the defective site. Cystic or sclerotic changes may be present. Neurofibromatosis is linked to about 55% of cases of congenital pseudarthrosis of the tibia.

Congenital pseudarthrosis

There are a few other rare associations, such as constricting bands. The pathology is nonspecific from other etiologies of pseudarthrosis, with a cuff of hamartomatous tissue surrounding the lesion. Fibroblasts and osteoclasts are present. Neurofibromas, axons, and perineural cells are never seen in the pseudarthrosis. The natural history is somewhat variable. Pseudarthrosis may be present in infancy, or the tibia may remain intact throughout a portion of childhood only to fracture later; most by age 2 or 3. Late onset fractures seem to have a better prognosis. Differential diagnosis can include physiologic bowing (which has a gentle bow of the entire leg rather than the sharp, localized bow seen with pseudarthrosis), focal cartilaginous dysplasia (which has a good prognosis), and posteromedial bow which also has a better prognosis. Prophylactic bracing may prevent or delay fracture, but the data is not sufficient to be sure.

The etiology and pathogenesis of the entity is not well established. A familial incidence has been reported; however, most cases are sporadic. The hypothesis of a non-union of the two ossification centers has been disputed as it has been demonstrated that the clavicle has a single ossification center. A mechanical factor has been proposed to exist in the pathogenesis, where minor variations in the development of the subclavian artery have been postulated to be the reason, as it passes just below the clavicle particularly on the right side. The left-sided involvement of the clavicle in congenital pseudoarthrosis is extremely rare and most cases are associated with dextrocardia resulting in the reversal of the relative positions of the subclavian arteries. Other cases supporting the mechanical factors involved the existence of well-formed or rudimentary cervical ribs with a fibrous connection to the first rib which results in the elevation of the first rib, and thus the subclavian artery theoretically plays a role in the development of the pseudoarthrosis.

Symptoms:

    Wobbly gait.

  • Limping or lameness.

  • Stiffness of the joints.

  • Difficulty in climbing stairs.

Diagnosis:

It can be discovered in the patient who does not have any real symptoms when dynamic imaging studies are done. Dynamic means the X-rays are taken as the patient is moving. But this method is not very reliable and would not be done routinely after surgery if the patient was not having any problems.

When it comes to diagnostic imaging, there is not a good way to tell if the fusion failed. When reading dynamic radiographs, the radiologist knows that just because there is not any obvious motion doesn't mean the fusion is complete. And just how much motion constitutes a failed fusion remains fuzzy. There is a lot of debate about what is and what is not a solid fusion. Some experts think there's a difference in springiness between a fusion with and without hardware to hold it together during the healing phase.

Thin-slice CT scans have been used to assess the fusion site. But the results do not really add anything more than what is seen on the X-rays. The one exception to this is in the case of locked pseudarthrosis. Thin-cut CT scans help show this problem more clearly than dynamic radiographs. Locked pseudarthrosis describes a situation in which the top and bottom of the cage inserted between the two vertebrae has fused solid but the middle (inside the cage) has not filled in with bone and solidified.

MRIs can be a bit iffy in patients with hardware in place because the implants cause artifacts (unexplained shadows and altered densities). Those changes interfere in judging whether or not the fusion is completed. There has been some question about the use of ultrasound and bone scans to help diagnose pseudarthrosis. Not enough study has been done to clear up any questions about these modalities. When imaging studies do not aid in the diagnosis, the surgeon can rely on a follow-up surgical procedure to confirm any diagnostic suspicions. Only patients with painful, disabling symptoms would undergo a second (diagnostic) procedure.

Treatment:

There is a great deal of information available on treatment of congenital pseudarthrosis of the tibia. Currently popular methods include excision of the lesion, followed by compression with the Ilizarov device, which can also be used to lengthen the tibia, vascularized free fibular graft, intramedullary rodding, which includes the ankle and subtalar joint and autogenous grafting, electrical stimulation (used less now than 20 years ago), and bypass autogenous graft. Results are better in children > 5 years old, and poorer with the dysplastic type. Rates of union around 60-70% are often reported. When treatment fails, a Symes amputation and prosthetic fitting can result in a very functional limb. Sometimes the pseudarthrosis will heal after amputation, which is the reason underlying the inclusion of the ankle and foot in intramedullary rodding procedures. Fracture following successful achievement of union is not rare. Patients with union at skeletal maturity usually, but not always, fare well in adult life.

There is presently active disagreement among pediatric orthopaedists treating this condition regarding the optimum treatment, and indications for amputation. Those performing reconstructive procedures are more inclined to regard amputation as a failure; others less enthusiastic about reconstructive procedures regard amputation and prosthetic fitting as superior to a reconstructed but fragile limb. It is worthwhile, when perusing results of treatment of pseudarthrosis to note how results are performed. In one paper reporting successful treatment, a small entry in the results section notes that many patients had residual deformity, but were so fatigued from the treatment, they elected to defer deformity correction. Congenital pseudarthrosis of the tibia is still a vexing problem for the pediatric orthopaedist, and there is no consensus on optimum treatment.

NOTE: The above information is for processing purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.

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