Congenital Pseudarthrosis of the Tibia (CPT) is a rare paediatric disease presenting with a bowing deformity of the tibia at birth or within the first decade of life. [1] It is most commonly associated with Neurofibromatosis type 1 (NF-1). [2] For children with CPT, pathological fracture of the tibia eventually occurs, resulting in persistent nonunion of the fracture site. If left untreated, leg deformities, joint stiffness, leg-length discrepancy and pain will persist. [3] Diagnosis is done clinically and through X-ray imaging, with numerous classifications based on the severity of bowing and presence of fracture or intraosseous lesion. [4]
Pathogenesis of CPT remains unclear. Genetic factors may be related due to its association with NF-1, but does not completely explain the development and location of CPT. It is likely related to the involvement of pathological periosteum in the tibia, resulting in abnormal bone turnover. [1] [5]
Treatment for CPT is through surgical correction, to limit the progression of deformity and to correct shortening of the affected limb. Prognosis of treatment depends on site and type of CPT, and there is a risk of recurrent fracture. [6] [7]
About 1 in 150,000 births present with CPT, but aside from its association with NF-1, not much else is shown from epidemiological studies. [1] [4]
Primary CPT presents at birth or in infants as anterolateral bowing of the tibia. Bowing is observed as shortening of the corresponding leg, and is confirmed with X-ray imaging. It is commonly presented unilaterally, but can be bilateral. [1] [8]
Secondary CPT does not present with obvious bowing at birth and may be overlooked, but will eventually progress to pathological fracture as the infant grows. Approximately 50% of fractures occur before the patient is two years of age, when toddlers begin learning to walk. [1] [8]
CPT is characterized by persistent nonunion because of fractures of the tibia and the presence of fibrous tissue between parts of the fractured bone. The persistent nonunion eventually leads to the formation of a false joint, otherwise known as pseudarthrosis. This pseudarthrosis is a non-healing bone lesion, resulting in reduction of mobility and persistent pain in the lower leg. [3]
CPT is most commonly associated with NF-1, with around 50% of cases of CPT being developed from NF-1. [2] A complete neurological and dermatological examination should be done for a newborn baby with anterolateral bowing of the tibia to screen for NF-1. [9]
Diagnosis is done through clinical examination and confirmed with radiographs of the tibia. Other associated clinical findings for NF-1, such as cafe-au-lait spots, neurofibromas and lisch nodules may also be found. [10] “Early onset” CPT is regarded as fracture occurring <4 years old, while “late onset” CPT is regarded as fracture occurring >4 years old. Numerous other classifications have been proposed for CPT, owing to the heterogeneity of the disease. [4] [11] The Crawford and Boyd classifications are more traditional descriptive classifications emphasizing the presence of sclerosis, cystic and atrophic changes of the tibia. The Paley classification is a more recent classification which also takes into account the fibula for treatment and outcome. [12]
Type | Findings |
---|---|
I | Anterior bowing with an increase in cortical density and a narrow medulla |
II | Anterior bowing with narrow, sclerotic medulla |
III | Anterior bowing associated with a cyst or signs of a prefracture |
IV | Anterior bowing and a clear fracture with pseudarthrosis often associating the tibia and fibula |
Type | Findings |
---|---|
I | Anterior bowing associated with other congenital malformations |
II | Anterior bowing with an hourglass appearance to the tibia. A fracture usually occurs before the age of 2. The ends of the bone are thin, rounded and sclerotic with obliteration of the intramedullary canal. This type is more often associated with NF-1 and there is a poor prognosis with frequent recurrence during bone growth |
III | Pseudarthrosis developing from an intraosseous cyst, usually at the middle and distal third junction. Anterior bowing can precede or follow the development of the fracture. This type has a high rate of union and recurrence is rare |
IV | Sclerotic bone with no pathological bowing. The medullary canal is partially or completely obliterated. A fatigue fracture may occur and progress to pseudarthrosis. The prognosis is good if treatment begins before the fatigue fracture occurs |
V | Dysplastic appearance to the fibula. Pseudarthrosis can be located on either of the two bones of the tibial segment. The prognosis is good if the lesion is located only on the fibula, extension to the tibia has a prognosis similar to type II |
VI | Associated with an intraosseous fibroma or a schwannoma. The prognosis depends on the aggressiveness of the intraosseous lesion |
Type | Findings |
---|---|
1 | No fractures |
2A | No fracture of the tibia; fractured fibula, the fibula is not dislocated |
2B | No fracture of the tibia; fractured and proximally migrated fibula |
3 | Fractured tibia, no fracture of the fibula |
4A | Tibia and fibula both fractured |
4B | Tibia and fibula both fractured, the fibula is migrated proximally |
4C | Bone defect of the tibia, the fibula is migrated proximally |
The pathogenesis of CPT remains unclear nowadays. Various theories have been proposed in previous research, including mechanical, vascular, and genetic factors. However, none of these theories provide a comprehensive explanation for the development and location of CPT. [1]
Extensive research has highlighted the significant role of fibrous hamartoma and pathological periosteum in the development of CPT. [15] [16] [17] These factors are believed to hinder bone union by interposing mechanically and disrupt normal blood supply to the affected bone. The periosteum, in particular, may create a fibrous band that increases local pressure around the bone, leading to reduced vascularization and bone atrophy. [4] Additionally, thickening of blood vessel walls in the pseudarthrosis area may contribute to the vascularization defect. [18]
The association of NF-1 in a substantial portion (40 to 80%) of CPT cases suggests a potential genetic disorder. [19] Neurofibromin 1 (NF1) is a gene that codes for a protein called neurofibromin, which plays a crucial role in regulating the Ras protein—a key player in cell differentiation and proliferation. Neurofibromin normally acts as a tumor suppressor by converting Ras-GTP to an inactive form (Ras-GDP). [19] However, mutations in the NF1 gene result in the loss of neurofibromin function, leading to sustained activation of Ras. In certain CPT cases associated with NF-1, a double activation of the NF1 gene has been observed in the pseudarthrotic tissue. [20] This genetic abnormality which only presents in some cases, cannot solely explain the pathogenesis of CPT. The loss of neurofibromin function can lead to disturbances in the Ras-MAPK pathway, resulting in impaired osteoblastic differentiation. [21] Additionally, overexpression of the Ras pathway can increase the activity of osteoclasts and their precursors, contributing to bone resorption in CPT and the high incidence of recurrent fractures. [22] [23] In this case, the underlying pathogenic mechanisms of CPT likely involve a combination of signal abnormalities that enhance osteoclast activity, along with disturbances in osteoblastic differentiation, ultimately leading to defective bone remodeling. These processes are further exacerbated by the diminished local vascularization in the affected area. [1]
Ilizarov fixation is an effective surgical approach for treating CPT, particularly when significant bone gaps or deformities are present. The technique involves applying an external fixator framework known as an Ilizarov apparatus. Composed of rings connected by wires and thin wires or half-pins inserted into the bone, the apparatus allows precise control over bone alignment by gradually distracting or compressing bone ends. [24] Through application of regulated forces, the Ilizarov method stimulates new bone formation and facilitates bone union. Steady adjustments to the frame can progressively correct deformities, lengthen the bone, and induce consolidation across the pseudarthrosis site. [25] This technique has been proven to have high healing rate and a low refracture rate later on in clinical practice. [26] [25]
The Sofield fragmentation technique entails making numerous small bone fractures via controlled osteotomies (surgical bone cuts) in the affected region. Orthopaedic surgeons then stabilize and compress the resultant bone fragments securely using internal fixation devices like plates, screws or intramedullary rods. By intentionally fracturing the bone in a regulated manner and ensuring stability, Sofield fragmentation promotes healing while also assisting consolidation at the pseudarthrosis site. [27] [24]
Intramedullary stabilization involves inserting a rod or nail into the tibial medullary canal. This offers structural support from within the affected bone, allowing for bone alignment and union. Surgeons may opt for flexible or rigid intramedullary nails depending on patient-specific factors such as age, pseudarthrosis severity and any accompanying deformities. [28] Although it almost guaranteed fracture healing and no refractures within a few years, the intramedullary nails would need to be replaced with age, leading to the pain of repeated surgery. [29] [30] [31]
In cases of extensive tibial bone loss or compromised blood flow, surgeons may perform a free vascularized fibular graft. This involves harvesting a section of fibula (usually 10–12 cm long) along with its blood supply from the patient's leg and transplanting it to the pseudarthrosis site. [32] As a vascularized graft, the fibula provides a fresh blood source to aid bone growth and repair at the defect location. [33] This unconventional procedure is reserved for the most challenging clinical presentations, saving many children with CPT from amputation since it was invented in the 1990s. [34] However, due to the lack of mechanical support, the healed bone has a high chance of refracture if this technique was applied alone for CPT treatment. [35] Therefore, it is commonly applied together with intramedullary nails in recent years so as to deal with both tibial loss and low bone mechanical strength, and has demonstrated satisfying efficacy in clinical practice. [36] [37]
In general, 75% of CPT treatments result in initial union, with an average initial union time of 7.2 months. 35% of cases will result in refracture after treatment. [6] [38] Prognosis of treatment depends on several factors relating to the nature and history of the fracture. Age of diagnosis is one of the factors as fractures in older patients are associated with better prognosis. This could be due to the greater cross-sectional bone area, allowing for lower refracture rates. [1] [6] Early diagnosis and surgical treatment before the disease progresses is also associated with favourable results and minimized deformity. [39] Site and type of pseudarthrosis have an impact on treatment success rate, as a lower location of fracture increases the complexity of the surgical operation due to the proximity with the ankle joint. More severe types of pseudarthrosis, such as those with severe bone deformities and significant leg length shortening is also associated with poor prognosis. [40] Patients with a history of multiple surgical interventions and recurrent fractures also indicate poor prognosis, and suggest a high risk of refracture after treatment. [1]
CPT is a rare disease in children, with an estimated frequency of 1 in 150,000 births. [1] Few epidemiological studies for CPT have been done, so the racial and gender distribution is unknown. From its association with NF-1, it is found that around 50 percent of cases of CPT develop from NF-1, though recent studies found the percentage may be as high as 84%, due to CPT being diagnosed before other more subtle signs of NF-1 appear. [2] [19] In NF-1 cases, CPT occurs in infancy in approximately 5 percent of persons, with a male predominance of 1.7:1. [41]
The ankle, the talocrural region or the jumping bone (informal) is the area where the foot and the leg meet. The ankle includes three joints: the ankle joint proper or talocrural joint, the subtalar joint, and the inferior tibiofibular joint. The movements produced at this joint are dorsiflexion and plantarflexion of the foot. In common usage, the term ankle refers exclusively to the ankle region. In medical terminology," can refer broadly to the region or specifically to the talocrural joint.
Orthopedic surgery or orthopedics is the branch of surgery concerned with conditions involving the musculoskeletal system. Orthopedic surgeons use both surgical and nonsurgical means to treat musculoskeletal trauma, spine diseases, sports injuries, degenerative diseases, infections, tumors, and congenital disorders.
An osteotomy is a surgical operation whereby a bone is cut to shorten or lengthen it or to change its alignment. It is sometimes performed to correct a hallux valgus, or to straighten a bone that has healed crookedly following a fracture. It is also used to correct a coxa vara, genu valgum, and genu varum. The operation is done under a general anaesthetic.
Neurofibromatosis type I (NF-1), or von Recklinghausen syndrome, is a complex multi-system human disorder caused by the mutation of neurofibromin 1 (NF-1), a gene on chromosome 17 that is responsible for production of a protein (neurofibromin) which is needed for normal function in many human cell types. NF-1 causes tumors along the nervous system which can grow anywhere on the body. NF-1 is one of the most common genetic disorders and is not limited to any person's race or sex. NF-1 is an autosomal dominant disorder, which means that mutation or deletion of one copy of the NF-1 gene is sufficient for the development of NF-1, although presentation varies widely and is often different even between relatives affected by NF-1.
In medicine, the Ilizarov apparatus is a type of external fixation apparatus used in orthopedic surgery to lengthen or to reshape the damaged bones of an arm or a leg; used as a limb-sparing technique for treating complex fractures and open bone fractures; and used to treat an infected non-union of bones, which cannot be surgically resolved. The Ilizarov apparatus corrects angular deformity in a leg, corrects differences in the lengths of the legs of the patient, and resolves osteopathic non-unions; further developments of the Ilizarov apparatus progressed to the development of the Taylor Spatial Frame.
A malignant peripheral nerve sheath tumor (MPNST) is a form of cancer of the connective tissue surrounding nerves. Given its origin and behavior it is classified as a sarcoma. About half the cases are diagnosed in people with neurofibromatosis; the lifetime risk for an MPNST in patients with neurofibromatosis type 1 is 8–13%. MPNST with rhabdomyoblastomatous component are called malignant triton tumors.
Nonunion is permanent failure of healing following a broken bone unless intervention is performed. A fracture with nonunion generally forms a structural resemblance to a fibrous joint, and is therefore often called a "false joint" or pseudoarthrosis. The diagnosis is generally made when there is no healing between two sets of medical imaging, such as X-ray or CT scan. This is generally after 6–8 months.
Neurofibromin 1 (NF1) is a gene in humans that is located on chromosome 17. NF1 codes for neurofibromin, a GTPase-activating protein that negatively regulates RAS/MAPK pathway activity by accelerating the hydrolysis of Ras-bound GTP. NF1 has a high mutation rate and mutations in NF1 can alter cellular growth control, and neural development, resulting in neurofibromatosis type 1. Symptoms of NF1 include disfiguring cutaneous neurofibromas (CNF), café au lait pigment spots, plexiform neurofibromas (PN), skeletal defects, optic nerve gliomas, life-threatening malignant peripheral nerve sheath tumors (MPNST), pheochromocytoma, attention deficits, learning deficits and other cognitive disabilities.
Ollier disease is a rare sporadic nonhereditary skeletal disorder in which typically benign cartilaginous tumors (enchondromas) develop near the growth plate cartilage. This is caused by cartilage rests that grow and reside within the metaphysis or diaphysis and eventually mineralize over time to form multiple enchondromas. Key signs of the disorder include asymmetry and shortening of the limb as well as an increased thickness of the bone margin. These symptoms are typically first visible during early childhood with the mean age of diagnosis being 13 years of age. Many patients with Ollier disease are prone to develop other malignancies including bone sarcomas that necessitate treatment and the removal of malignant bone neoplasm. Cases in patients with Ollier disease has shown a link to IDH1, IDH2, and PTH1R gene mutations. Currently, there are no forms of treatment for the underlying condition of Ollier disease but complications such as fractures, deformities, malignancies that arise from it can be treated through surgical procedures. The prevalence of this condition is estimated at around 1 in 100,000. It is unclear whether the men or women are more affected by this disorder due to conflicting case studies.
An open fracture, also called a compound fracture, is a type of bone fracture that has an open wound in the skin near the fractured bone. The skin wound is usually caused by the bone breaking through the surface of the skin. An open fracture can be life threatening or limb-threatening due to the risk of a deep infection and/or bleeding. Open fractures are often caused by high energy trauma such as road traffic accidents and are associated with a high degree of damage to the bone and nearby soft tissue. Other potential complications include nerve damage or impaired bone healing, including malunion or nonunion. The severity of open fractures can vary. For diagnosing and classifying open fractures, Gustilo-Anderson open fracture classification is the most commonly used method. This classification system can also be used to guide treatment, and to predict clinical outcomes. Advanced trauma life support is the first line of action in dealing with open fractures and to rule out other life-threatening condition in cases of trauma. The person is also administered antibiotics for at least 24 hours to reduce the risk of an infection.
Gerdy's tubercle is a lateral tubercle of the tibia, located where the iliotibial tract inserts. It was named after French surgeon Pierre Nicolas Gerdy (1797–1856).
The Taylor Spatial Frame (TSF) is an external fixator used by podiatric and orthopaedic surgeons to treat complex fractures and bone deformities. The medical device shares a number of components and features of the Ilizarov apparatus. The Taylor Spatial Frame is a hexapod device based on a Stewart platform, and was invented by orthopaedic surgeon Charles Taylor. The device consists of two or more aluminum or carbon fibre rings connected by six struts. Each strut can be independently lengthened or shortened to achieve the desired result, e.g. compression at the fracture site, lengthening, etc. Connected to a bone by tensioned wires or half pins, the attached bone can be manipulated in three dimensions and 9 degrees of freedom. Angular, translational, rotational, and length deformities can all be corrected simultaneously with the TSF.
Fibular hemimelia or longitudinal fibular deficiency is "the congenital absence of the fibula and it is the most common congenital absence of long bone of the extremities." It is the shortening of the fibula at birth, or the complete lack thereof. Fibular hemimelia often causes severe knee instability due to deficiencies of the ligaments. Severe forms of fibula hemimelia can result in a malformed ankle with limited motion and stability. Fusion or absence of two or more toes are also common. In humans, the disorder can be noted by ultrasound in utero to prepare for amputation after birth or complex bone lengthening surgery. The amputation usually takes place at six months with removal of portions of the legs to prepare them for prosthetic use. The other treatments, which include repeated corrective osteotomies and leg-lengthening surgery, are costly and associated with residual deformity.
Dror Paley is a Canadian-trained orthopedic surgeon, who specializes in limb lengthening and deformity correction procedures.
Fracture blisters occur on skin overlying a fractured bone, and fractures complicated by the development of overlying blisters remain a clinical dilemma in orthopedics.
A crus fracture is a fracture of the lower legs bones meaning either or both of the tibia and fibula.
The following outline is provided as an overview of and topical guide to trauma and orthopaedics:
Orthopedic surgery is the branch of surgery concerned with conditions involving the musculoskeletal system. Orthopedic surgeons use both surgical and nonsurgical means to treat musculoskeletal injuries, sports injuries, degenerative diseases, infections, bone tumours, and congenital limb deformities. Trauma surgery and traumatology is a sub-specialty dealing with the operative management of fractures, major trauma and the multiply-injured patient.
Tibia shaft fracture is a fracture of the proximal (upper) third of the tibia. Due to the location of the tibia, it is frequently injured. Thus it is the most commonly fractured long bone in the body.
David S. Feldman is an American orthopedic surgeon, author, contributor to NIH, and Associate Director of the Paley Orthopedic and Spine Institute. His work involves spinal deformities and complex conditions such as Arthrogryposis, skeletal dysplasia|, scoliosis, multiple hereditary exostoses, congenital pseudarthrosis of the tibia, hip dysplasia, and Legg–Calvé–Perthes disease as well as lower limb deformities and limb length discrepancies. He was previously Professor of Orthopedic Surgery and Pediatrics at NYU Langone Medical Center.