Congenital Pseudarthrosis

Congenital pseudarthrosis is a rare bone condition where a fracture fails to heal properly, most commonly affecting the shin bone in young children. Though challenging to treat, modern surgical techniques have transformed outcomes for patients with this condition.

Table of contents

• What Is Congenital Pseudarthrosis?
• How Common Is This Condition?
• Causes and Associated Conditions
• Signs and Symptoms
• How Is It Diagnosed?
• Treatment Options
• Challenges and Complications

Congenital Tibial Pseudarthrosis, CPT

• Tibia (shin bone)
• Fibula
• Periosteum (membrane covering the bone)
• Ankle
• Knee

What Is Congenital Pseudarthrosis?

Congenital pseudarthrosis is a condition where a bone fracture does not heal correctly, creating what doctors call a pseudarthrosis or “false joint” where solid bone should exist. The word “congenital” means the condition is present from birth or develops in early childhood^[1].

This condition most commonly affects the tibia, which is the larger of the two bones in the lower leg that connects the ankle to the knee^[4]. When it occurs in the tibia, it is called congenital pseudarthrosis of the tibia, or CPT. The condition was first described by a physician named Paget in 1891^[1].

The problem develops in a segment of bone that is abnormally formed. A fracture may happen spontaneously or after very minor injury to this weak area of bone. Once the break occurs, the bone has little or no ability to heal on its own. This creates an unstable area where the leg should be solid and strong, making it difficult for the child to walk and function normally^[2].

The root of the problem lies in the periosteum, a membrane that covers bones. In healthy bones, this tissue helps form new bone when a fracture happens. In congenital pseudarthrosis, the periosteum is abnormal and prevents proper bone healing^[2].

How Common Is This Condition?

Congenital pseudarthrosis of the tibia is a rare condition. It occurs in approximately 1 in 140,000 to 1 in 250,000 live births^[6]. Some sources report it as occurring in 1 out of every 150,000 births^[1]. The condition typically affects only one leg and bilateral forms (affecting both legs) are extremely rare^[6].

Causes and Associated Conditions

The exact cause of congenital pseudarthrosis remains unclear, despite many theories proposed over the years. Various researchers have suggested it might be due to genetic defects, nutritional deficiencies, hormonal disturbances, or problems with nerves and blood vessels during early development^[1].

What doctors do know is that congenital pseudarthrosis has a strong connection to other medical conditions. Between 40% and 90% of children with this condition also have neurofibromatosis type 1 (NF-1), a genetic disorder that affects nerve cell growth and causes skin changes^[1][2]. Because of this strong link, all patients diagnosed with congenital pseudarthrosis should be screened for neurofibromatosis through genetic counseling and testing^[1].

However, not all cases are related to neurofibromatosis. The condition can also occur with fibrous dysplasia, osteofibrous dysplasia, and cleidocranial dysostosis^[2]. In some cases, the exact cause remains unknown, which doctors call “idiopathic”^[2].

Research has shown that the poor healing in congenital pseudarthrosis is due to several factors working together: the irregular periosteum, abnormally overactive osteoclasts (cells that break down bone), and the mechanical challenge of stabilizing very small bone fragments in young children^[2].

Signs and Symptoms

Congenital pseudarthrosis typically appears before a child turns two years old^[2]. The condition may be noticed at birth or may become apparent when the child begins to walk^[1].

The most common signs include a curved or bowed appearance of the shin bone. This is called anterolateral bowing, meaning the bone curves forward and to the side. In some cases, parents notice that the child’s leg appears unstable or that the child has difficulty bearing weight on the affected leg^[2].

When a fracture occurs through the affected area, it typically happens either spontaneously or after very minor trauma that would not normally cause a break in healthy bone^[2]. The broken bone does not heal properly, creating an unstable “false joint” where solid bone should be^[7].

As the condition progresses, several problems develop. The affected leg often becomes shorter than the healthy leg because the tibia grows more slowly and because of the bowing deformity. The bone remains weak and has a tendency to fracture or refracture repeatedly^[7].

In 60% to 90% of patients with congenital pseudarthrosis of the tibia, the fibula (the smaller bone next to the tibia in the lower leg) also shows abnormalities^[1].

How Is It Diagnosed?

Doctors typically identify congenital pseudarthrosis through X-rays and physical examination^[2]. During the doctor visit, several steps occur to make an accurate diagnosis.

The doctor will review the child’s medical history and family history. They will perform a thorough examination of the skin, including areas like the underarms and groin, looking for signs that might indicate neurofibromatosis, such as skin freckling or unusual spots^[2].

The physical examination includes checking the range of motion of the hips, knees, and ankles. The doctor will assess the alignment of both lower legs and measure whether there is a difference in leg length. They will also examine the area of the false joint to determine how much movement exists where the bone should be solid^[2].

X-rays are essential for diagnosis. They can show the bowing of the bone, the quality of the bone tissue, and whether a fracture or nonunion is present. The X-rays also help determine the condition of the joints and the severity of any bone abnormalities^[2].

Because of the strong link between congenital pseudarthrosis and neurofibromatosis, the doctor will evaluate the patient for this genetic condition, which may be confirmed through genetic blood testing^[2].

For children who are deemed high risk, such as those with neurofibromatosis, screening X-rays may be performed in early childhood even before symptoms appear^[2].

Treatment Options

The primary goal of treatment is to achieve healing and union of the broken bone and to maintain that union over time. Treatment must also address resulting problems such as differences in leg length and bone deformities^[2].

Treatment is mainly surgical, although some non-surgical approaches may be used in certain situations or as part of the overall treatment plan^[6].

Non-Surgical Treatment

For children who have a curved tibia but no actual fracture, doctors may use a special brace called a clamshell brace. The purpose is to allow the child to be active while trying to prevent the deformity from getting worse and delay or prevent fracture^[2].

Even after successful surgery, most children need to wear braces until they finish growing to help prevent refracture^[2].

Some medications may be used to support surgical treatment. Bisphosphonate medications work by interfering with cells called osteoclasts that break down bone. These cells are overactive in congenital pseudarthrosis. The medication may be given through an IV before and after surgery as part of comprehensive treatment^[7].

Surgical Treatment

Surgery remains the main treatment approach. The goals are to remove the diseased portion of bone and the abnormal periosteum, replace it with healthy tissue, and stabilize the bone to promote healing. The alignment must be corrected and maintained^[6].

Modern surgical techniques use a multi-faceted approach that addresses each component of the problem. Several different surgical methods may be used, often in combination^[2].

One key technique involves placing a rod through the center of the tibia bone, called intramedullary nailing. This provides internal support to stabilize the bone^[6].

Surgeons often use bone grafts to help with healing. These grafts may come from the patient’s own hip bone. Some surgeons also use bone morphogenetic protein (BMP), a biological substance that stimulates bone formation, though this is an off-label use^[7].

An important modern approach is called the cross-union technique. This involves intentionally joining the tibia and fibula together at the site of the pseudarthrosis. This creates a wider, stronger area for bone healing and helps prevent future fractures^[15]. Studies have shown this technique to be highly effective, with some reporting 100% success in achieving bone union^[15].

External fixation devices, particularly the Ilizarov method, are also valuable. These devices attach to the bone with pins and provide external support. They can address not only the pseudarthrosis but also complex deformities, leg-length differences, and alignment problems^[13].

Additional procedures may be necessary over time to address leg length differences, correct deformities, and maintain proper alignment^[7].

Challenges and Complications

Congenital pseudarthrosis has historically been one of the most challenging conditions in pediatric bone surgery. The natural course of the disease is extremely unfavorable, and once a fracture occurs, there is little tendency for it to heal on its own^[6].

The most serious complication is refracture, meaning the bone breaks again after it has healed. This was a devastating and common problem in the past. With modern treatment protocols, particularly the cross-union technique, the risk of refracture has been significantly reduced^[2][15].

Other complications that can occur include problems with growth of the affected leg, mechanical misalignment of the leg, stiffness in nearby joints (particularly the ankle), and ongoing differences in leg length^[6].

Children with congenital pseudarthrosis must be followed until they reach skeletal maturity (finish growing) to identify and address any remaining problems after the initial healing^[6].

Historically, when treatments failed repeatedly or when there was severe deformity or leg length difference, amputation was sometimes considered. However, with modern treatment approaches, especially the cross-union protocol, many experts now believe that amputation should be reserved only for the most severe cases of failed reconstruction^[5][6].

While congenital pseudarthrosis remains a difficult condition to treat, advances in medical treatment and surgical techniques have generated vast improvements in outcomes. Current treatment protocols have minimized complications that were once devastating^[2].